ORCID Profile
0000-0001-7003-188X
Current Organisations
University of Western Australia
,
National Research Foundation
,
University of Cape Town Faculty of Law
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Photonics and Electro-Optical Engineering (excl. Communications) | Gene Expression (incl. Microarray and other genome-wide approaches) | Genome Structure and Regulation | Genetics | Electrical and Electronic Engineering | Lasers and Quantum Electronics | Neurogenetics |
ANZSRC Socio-Economic Objective (SEO)
Skeletal System and Disorders (incl. Arthritis) | Expanding Knowledge in the Biological Sciences | Expanding Knowledge in Psychology and Cognitive Sciences | Manufacturing not elsewhere classified | Expanding Knowledge in the Medical and Health Sciences | Aerospace Transport not elsewhere classified
Related Links
Publications
Quantitative Analysis of Synaptic Vesicle Rabs Uncovers Distinct Yet Overlapping Roles for Rab3a and Rab27b in Ca2+-Triggered Exocytosis
Publisher: Society for Neuroscience
Date: 06-10-2010
DOI: 10.1523/JNEUROSCI.0907-10.2010
Abstract: Rab GTPases are molecular switches that orchestrate protein complexes before membrane fusion reactions. In synapses, Rab3 and Rab5 proteins have been implicated in the exo-endocytic cycling of synaptic vesicles (SVs), but an involvement of additional Rabs cannot be excluded. Here, combining high-resolution mass spectrometry and chemical labeling (iTRAQ) together with quantitative immunoblotting and fluorescence microscopy, we have determined the exocytotic (Rab3a, Rab3b, Rab3c, and Rab27b) and endocytic (Rab4b, Rab5a/b, Rab10, Rab11b, and Rab14) Rab machinery of SVs. Analysis of two closely related proteins, Rab3a and Rab27b, revealed colocalization in synaptic nerve terminals, where they reside on distinct but overlapping SV pools. Moreover, whereas Rab3a readily dissociates from SVs during Ca 2+ -triggered exocytosis, and is susceptible to membrane extraction by Rab-GDI, Rab27b persists on SV membranes upon stimulation and is resistant to GDI-coupled Rab retrieval. Finally, we demonstrate that selective modulation of the GTP/GDP switch mechanism of Rab27b impairs SV recycling, suggesting that Rab27b, probably in concert with Rab3s, is involved in SV exocytosis.
Rab3D Regulates a Novel Vesicular Trafficking Pathway That Is Required for Osteoclastic Bone Resorption
Publisher: Informa UK Limited
Date: 06-2005
Genetic regulatory mechanisms in human osteoclasts suggest a role for the STMP1 and DCSTAMP genes in Paget’s disease of bone
Publisher: Springer Science and Business Media LLC
Date: 31-01-2019
DOI: 10.1038/S41598-018-37609-0
Abstract: Paget’s disease of bone (PDB) is characterised by focal abnormalities of bone remodelling, with increased osteoclastic resorption the primary feature of the disease. Genetic factors have been shown to play an important role in PDB, and genome-wide association studies (GWAS) have identified 7 genetic loci as associated with PDB at the genome-wide level. Expression quantitative trait locus (eQTL) studies using cell types that are directly relevant to the disease of interest are increasingly being used to identify putative effector genes for GWAS loci. We have recently constructed a unique osteoclast-specific eQTL resource using cells differentiated in vitro from 158 subjects for study of the genetics of bone disease. Considering the major role osteoclasts have in PDB, we used this resource to investigate potential genetic regulatory effects for the 7 PDB genome-wide significant loci on genes located within 500 kb of each locus. After correction for multiple testing, we observed statistically significant associations for rs4294134 with expression of the gene STMP1 , and rs2458413 with expression of the genes DPYS and DCSTAMP . The eQTL associations observed for rs4294134 with STMP1 , and rs2458413 with DCSTAMP were further supported by eQTL data from other tissue types. The product of the STMP1 gene has not been extensively studied, however the DCSTAMP gene has an established role in osteoclast differentiation and the associations seen between rs2458413 and PDB are likely mediated through regulatory effects on this gene. This study highlights the value of eQTL data in determining which genes are relevant to GWAS loci.
Caffeic acid phenethyl ester, an active component of honeybee propolis attenuates osteoclastogenesis and bone resorption via the suppression of RANKL‐induced NF‐κB and NFAT activity
Publisher: Wiley
Date: 25-09-2009
DOI: 10.1002/JCP.21898
Abstract: Receptor activator NF-kappaB ligand (RANKL)-activated signaling is essential for osteoclast differentiation, activation and survival. Caffeic acid phenethyl ester (CAPE), a natural NF-kappaB inhibitor from honeybee propolis has been shown to have anti-tumor and anti-inflammatory properties. In this study, we investigated the effect of CAPE on the regulation of RANKL-induced osteoclastogenesis, bone resorption and signaling pathways. Low concentrations of CAPE (<1 microM) dose dependently inhibited RANKL-induced osteoclastogenesis in RAW264.7 cell and bone marrow macrophage (BMM) cultures, as well as decreasing the capacity of human osteoclasts to resorb bone. CAPE inhibited both constitutive and RANKL-induced NF-kappaB and NFAT activation, concomitant with delayed IkappaBalpha degradation and inhibition of p65 nuclear translocation. At higher concentrations, CAPE induced apoptosis and caspase 3 activities of RAW264.7 and disrupts the microtubule network in osteoclast like (OCL) cells. Taken together, our findings demonstrate that inhibition of NF-kappaB and NFAT activation by CAPE results in the attenuation of osteoclastogenesis and bone resorption, implying that CAPE is a potential treatment for osteolytic bone diseases.
A bioceramic with enhanced osteogenic properties to regulate the function of osteoblastic and osteocalastic cells for bone tissue regeneration
Publisher: IOP Publishing
Date: 15-06-2016
DOI: 10.1088/1748-6041/11/3/035018
Abstract: Bioceramics for regenerative medicine applications should have the ability to promote adhesion, proliferation and differentiation of osteoblast and osteoclast cells. Osteogenic properties of the material are essential for rapid bone regeneration and new bone formation. The aim of this study was to develop a silicate-based ceramic, gehlenite (GLN, Ca2Al2SiO7), and characterise its physiochemical, biocompatibility and osteogenic properties. A pure GLN powder was synthesised by a facile reactive sintering method and compacted to disc-shaped specimens. The sintering behaviour and degradation of the GLN discs in various buffer solutions were fully characterised. The cytotoxicity of GLN was evaluated by direct and indirect methods. In the indirect method, primary human osteoblast cells (HOBs) were exposed to diluted extracts (100, 50, 25, 12.5 and 6.25 mg ml(-1)) of fine GLN particles in culture medium. The results showed that the extracts did not cause any cytotoxic effect on the HOBs with the number of cells increasing significantly from day 1 to day 7. GLN-supported HOB attachment and proliferation, and significantly enhanced osteogenic gene expression levels (Runx2, osteocalcin, osteopontin and bone sialoprotein) were compared with biphasic calcium phosphate groups (BCP, a mixture of hydroxyapatite (60wt.%) and β-tricalcium phosphate(40wt.%)). We also demonstrated that in addition to supporting HOB attachment and proliferation, GLN promoted the formation of tartrate-acid resistance phosphatase (TRAP) positive multinucleated osteoclastic cells (OCs) derived from mouse bone marrow cells. Results also demonstrated the ability of GLN to support the polarisation of OCs, a prerequisite for their functional resorptive activity which is mainly influenced by the composition and degradability of biomaterials. Overall, the developed GLN is a prospective candidate to be used in bone regeneration applications due its effective osteogenic properties and biocompatibility.
The molecular structure and function of sorting nexin 10 in skeletal disorders, cancers, and other pathological conditions
Publisher: Wiley
Date: 25-11-2020
DOI: 10.1002/JCP.30173
Thonzonium bromide inhibits RANKL-induced osteoclast formation and bone resorption in vitro and prevents LPS-induced bone loss in vivo
Publisher: Elsevier BV
Date: 03-2016
DOI: 10.1016/J.BCP.2016.02.013
Abstract: Osteoclasts (OCs) play a pivotal role in a variety of lytic bone diseases including osteoporosis, arthritis, bone tumors, Paget's disease and the aseptic loosening of orthopedic implants. The primary focus for the development of bone-protective therapies in these diseases has centered on the suppression of OC formation and function. In this study we report that thonzonium bromide (TB), a monocationic surface-active agent, inhibited RANKL-induced OC formation, the appearance of OC-specific marker genes and bone-resorbing activity in vitro. Mechanistically, TB blocked the RANKL-induced activation of NF-κB, ERK and c-Fos as well as the induction of NFATc1 which is essential for OC formation. TB disrupted F-actin ring formation resulting in disturbances in cytoskeletal structure in mature OCs during bone resorption. Furthermore, TB exhibited protective effects in an in vivo murine model of LPS-induced calvarial osteolysis. Collectively, these data suggest that TB might be a useful alternative therapy in preventing or treating osteolytic diseases.
Comparative Perspectives on Communal Lands and Individual Ownership
Publisher: Routledge-Cavendish
Date: 26-02-2010
Effects of Bafilomycin A1: An inhibitor of vacuolar H (+)-ATPases on endocytosis and apoptosis in RAW cells and RAW cell-derived osteoclasts
Publisher: Wiley
Date: 10-03-2003
DOI: 10.1002/JCB.10477
Abstract: Bafilomycin A1, a specific inhibitor of V-ATPases, is a potent inhibitor of bone resorption, but the underlying mechanisms of its action remain unclear. In this study, we investigated the effect of Bafilomycin A1 on endocytosis and apoptosis in RAW cells and RAW cell-derived osteoclasts. Quantitative analysis by flow cytometry showed that Bafilomycin A1 increased total transferrin levels when RAW cells were exposed to labeled transferrin and decreased the total uptake of Dextran-rhodamine B, both in a dose- and time-dependent fashion, indicating that Bafilomycin influences receptor-mediated and fluid phase endocytosis in these cells. Furthermore, Bafilomycin A1 induced apoptosis of RAW cells in a dose dependent manner as evidenced by Annexin V flow cytometry. The action of Bafilomycin A1 on endocytotic events appeared to be more sensitive and occurred earlier than on its apoptosis inducing effects, suggesting that interrupting of endocytosis might be an early sign of Bafilomycin-mediated osteoclast inhibition. Semi-quantitative RT-PCR analysis showed that the gene transcripts of putative Bafilomycin A1 binding subunit, V-ATPase-subunit a3, were expressed in the preosteoclastic RAW cell line, and up-regulated during RANKL-induced osteoclastogenesis. Osteoclasts treated with Bafilomycin A1 exhibited apoptosis as well as altered cellular localization of Transferrin Alexa 647. Given that endocytosis and apoptosis are important processes during osteoclastic bone resorption, the potent effect of Bafilomycin A1 on endocytosis and apoptosis of osteoclasts and their precursor cells may in part account for Bafilomycin A1 inhibited bone resorption.
PLEKHM1/DEF8/RAB7 complex regulates lysosome positioning and bone homeostasis
Publisher: American Society for Clinical Investigation
Date: 20-10-2016
Parathyroid Hormone-Related Protein Negatively Regulates Tumor Cell Dormancy Genes in a PTHR1/Cyclic AMP-Independent Manner
Publisher: Frontiers Media SA
Date: 16-05-2018
p62 Ubiquitin Binding-Associated Domain Mediated the Receptor Activator of Nuclear Factor-κB Ligand-Induced Osteoclast Formation
Publisher: Elsevier BV
Date: 08-2006
DOI: 10.2353/AJPATH.2006.050960
Abstract: Paget's disease of bone (PDB) is a debilitating bone disorder characterized by giant osteoclasts, enhanced bone destruction, and irregular bone formation. Recently, mutations in SQSTM1 (also known as p62) have been detected in PDB sufferers, with all mutations resulting in either loss of function or truncation/deletion of the ubiquitin binding-associated (UBA) domain. We hypothesized that mutation in the p62 gene resulting in either deletion or premature termination of the UBA domain accounts for the elevated osteoclastic formation and bone resorption associated with PDB. Remarkably, overexpression of the p62 UBA domain deletion mutant (p62DeltaUBA) significantly enhanced osteoclastogenesis in vitro compared to cells expressing either wild-type p62 (p62WT) or a control vector in a RAW264.7 osteoclastogenic system. Overexpression of p62DeltaUBA potentiated the formation of abnormally large multinucleated osteoclasts and resorption of bone, reminiscent of PDB. Consistent with the enhancement of osteoclastogenesis, overexpression of p62DeltaUBA potentiated receptor activator of nuclear factor-kappaB ligand-induced activation of nuclear factor-kappaB, NFAT, and ERK phosphorylation. Furthermore, as determined by confocal microscopy, deletion of the p62 UBA domain impaired the association of p62 with TRAF6 in the proteasomal compartment. These results suggest that the UBA domain encodes essential regulatory elements required for receptor activator of nuclear factor-kappaB ligand-induced osteoclast formation and bone resorption that may be directly associated with the progression of PDB.
Circulating Lipocalin 2 Levels Predict Fracture-Related Hospitalizations in Elderly Women: A Prospective Cohort Study
Publisher: Wiley
Date: 21-05-2015
DOI: 10.1002/JBMR.2546
Abstract: Lipocalin 2 (LCN2) or neutrophil gelatinase-associated lipocalin (NGAL) is expressed in a wide range of cells and pathological states. Mounting evidence suggests lipocalin 2 may be an important regulator of bone homeostasis. Recently it has been suggested LCN2 is a novel mechanoresponsive gene central to the pathological response to low mechanical force. We undertook a prospective study of 1009 elderly women over 70 years of age to study the association between circulating LCN2 and potential associated variables, including estimated glomerular filtration rate, physical activity, and baseline measures of hip bone density and heel bone quality. Osteoporotic fractures requiring hospitalizations were identified from the Western Australian Data Linkage System. Over 14.5 years, 272 (27%) of women sustained an osteoporotic fracture-related hospitalization of these, 101 were hip fractures. Circulating LCN2 levels were correlated with body mass index and estimated glomerular filtration rate (r = 0.249, p < 0.001 and r = -0.481, p < 0.001, respectively) that modified the association with hip and heel bone measures. Per standard deviation increase in LCN2, there was a 30% multivariable-adjusted increase in the risk of any osteoporotic fracture (hazard ratio [HR] = 1.30, 95% confidence interval [CI] 1.13-1.50, p < 0.001). In participants with elevated LCN2 levels above the median (76.6 ng/mL), there was an 80% to 81% increase in the risk of any osteoporotic or hip fracture (HR = 1.81, 95% CI 1.38-2.36, p < 0.001 and HR = 1.80, 95% CI 1.16-2.78, p = 0.008, respectively). These associations remained significant after adjustment for total hip bone mineral density (p < 0.05). In conclusion, we have demonstrated that circulating LCN2 levels predict future risk of osteoporotic fractures requiring hospitalization. Measurement of LCN2 levels may improve fracture prediction in addition to current fracture risk factors in the elderly, particularly in those with impaired renal function.
Author response: The GTPase Rab26 links synaptic vesicles to the autophagy pathway
Publisher: eLife Sciences Publications, Ltd
Date: 21-01-2015
Collagen‐Derived Biomaterials in Bone and Cartilage Repair
Publisher: Wiley
Date: 26-07-2007
Distinct yet overlapping roles of Rab GTPases on synaptic vesicles
Publisher: Informa UK Limited
Date: 03-2011
Disulfiram Attenuates Osteoclast Differentiation In Vitro: A Potential Antiresorptive Agent
Publisher: Public Library of Science (PLoS)
Date: 30-04-2015
“Fusion and Fission” Unveils Remarkable Insights into Osteoclast Plasticity
Publisher: Springer Science and Business Media LLC
Date: 07-2012
Transcriptional activation of V-ATPase subunit d2 is regulated by NFATc1 in RANKL-induced osteoclastogenesis
Publisher: Elsevier BV
Date: 03-2008
Staphylococcus aureus infects osteoclasts and replicates intracellularly
Publisher: Cold Spring Harbor Laboratory
Date: 14-05-2019
DOI: 10.1101/638528
Abstract: Osteomyelitis (OM), or inflammation of bone tissue, occurs most frequently as a result of bacterial infection and severely perturbs bone structure. The majority of OM is caused by Staphylococcus aureus , and even with proper treatment, OM has a high rate of recurrence and chronicity. While S. aureus has been shown to infect osteoblasts, persist intracellularly, and promote the release of pro-osteoclastogenic cytokines, it remains unclear whether osteoclasts (OCs) are also a target of intracellular infection. In this study, we examined the interaction between S. aureus and OCs, demonstrating internalization of GFP-labeled bacteria by confocal microscopy, both in vitro and in vivo . Utilizing an intracellular survival assay and flow cytometry during OC differentiation from bone marrow macrophages (BMMs), we found that the intracellular burden of S. aureus increases after initial infection in cells with at least 2 days of exposure to the osteoclastogenic cytokine receptor activator of nuclear factor kappa-B ligand (RANKL). Presence of iding bacteria was confirmed via visualization by transmission electron microscopy. In contrast, undifferentiated BMMs, or those treated with interferon-γ or IL-4, had fewer internal bacteria, or no change, respectively, at 18 hours post infection, compared to 1.5 hours post infection. To further explore the signals downstream of RANKL, we manipulated NFATc1 and alternative NF-κB, which controls NFATc1 and other factors affecting OC function, finding that intracellular bacterial growth correlates with NFATc1 levels in RANKL-treated cells. Confocal microscopy in mature OCs showed a range of intracellular infection that correlated inversely with S. aureus and phagolysosome colocalization. The ability of OCs to become infected, paired with their diminished bactericidal capacity compared to BMMs, could promote OM progression by allowing S. aureus to evade initial immune regulation and proliferate at the periphery of lesions where OCs and bone remodeling are most abundant. The inflammation of bone tissue is called osteomyelitis, and most cases are caused by an infection with the bacterium Staphylococcus aureus . To date, the bone building cells, osteoblasts, have been implicated in the progression of these infections, but not much is known about how the bone resorbing cells, osteoclasts, participate. In this study, we show that S. aureus can infect osteoclasts and proliferate inside these cells, whereas macrophages, immune cells related to osteoclasts, destroy the bacteria. These findings elucidate a unique role for osteoclasts to harbor bacteria during infection, providing a possible mechanism by which bacteria could evade destruction by the immune system. Therapeutic interventions that target osteoclasts specifically might reduce the severity of OM or improve antibiotic responses.
Quantitative Comparison of Glutamatergic and GABAergic Synaptic Vesicles Unveils Selectivity for Few Proteins Including MAL2, a Novel Synaptic Vesicle Protein
Publisher: Society for Neuroscience
Date: 06-01-2010
DOI: 10.1523/JNEUROSCI.4074-09.2010
Abstract: Synaptic vesicles (SVs) store neurotransmitters and release them by exocytosis. The vesicular neurotransmitter transporters discriminate which transmitter will be sequestered and stored by the vesicles. However, it is unclear whether the neurotransmitter phenotype of SVs is solely defined by the transporters or whether it is associated with additional proteins. Here we have compared the protein composition of SVs enriched in vesicular glutamate (VGLUT-1) and GABA transporters (VGAT), respectively, using quantitative proteomics. Of quantified proteins, ∼50 were differentially distributed between the populations, with only few of them being specific for SVs. Of these, the most striking differences were observed for the zinc transporter ZnT3 and the vesicle proteins SV2B and SV31 that are associated preferentially with VGLUT-1 vesicles, and for SV2C that is associated mainly with VGAT vesicles. Several additional proteins displayed a preference for VGLUT-1 vesicles including, surprisingly, synaptophysin, synaptotagmins, and syntaxin 1a. Moreover, MAL2, a membrane protein of unknown function distantly related to synaptophysins and SCAMPs, cofractionated with VGLUT-1 vesicles. Both subcellular fractionation and immunolocalization at the light and electron microscopic level revealed that MAL2 is a bona-fide membrane constituent of SVs that is preferentially associated with VGLUT-1-containing nerve terminals. We conclude that SVs specific for different neurotransmitters share the majority of their protein constituents, with only few vesicle proteins showing preferences that, however, are nonexclusive, thus confirming that the vesicular transporters are the only components essential for defining the neurotransmitter phenotype of a SV.
Rab GTPases: Emerging Oncogenes and Tumor Suppressive Regulators for the Editing of Survival Pathways in Cancer
Publisher: MDPI AG
Date: 21-01-2020
Abstract: The Rab GTPase family of proteins are mediators of membrane trafficking, conferring identity to the cell membranes. Recently, Rab and Rab-associated factors have been recognized as major regulators of the intracellular positioning and activity of signaling pathways regulating cell growth, survival and programmed cell death or apoptosis. Membrane trafficking mediated by Rab proteins is controlled by intracellular localization of Rab proteins, Rab-membrane interactions and GTP-activation processes. Aberrant expression of Rab proteins has been reported in multiple cancers such as lung, brain and breast malignancies. Mutations in Rab-coding genes and/or post-translational modifications in their protein products disrupt the cellular vesicle trafficking network modulating tumorigenic potential, cellular migration and metastatic behavior. Conversely, Rabs also act as tumor suppressive factors inducing apoptosis and inhibiting angiogenesis. Deconstructing the signaling mechanisms modulated by Rab proteins during apoptosis could unveil underlying molecular mechanisms that may be exploited therapeutically to selectively target malignant cells.
The SQSTM1/p62 UBA domain regulates Ajuba localisation, degradation and NF-κB signalling function
Publisher: Public Library of Science (PLoS)
Date: 04-11-2021
DOI: 10.1371/JOURNAL.PONE.0259556
Abstract: The LIM-domain containing protein Ajuba and the scaffold protein SQSTM1 62 regulate signalling of NF-κB, a transcription factor involved in osteoclast differentiation and survival. The ubiquitin-associated domain of SQSTM1 62 is frequently mutated in patients with Paget’s disease of bone. Here, we report that Ajuba activates NF-κB activity in HEK293 cells, and that co-expression with SQSTM1 62 inhibits this activation in an UBA domain-dependent manner. SQSTM1 62 regulates proteins by targeting them to the ubiquitin-proteasome system or the autophagy-lysosome pathway. We show that Ajuba is degraded by autophagy, however co-expression with SQSTM1 62 (wild type or UBA-deficient) protects Ajuba levels both in cells undergoing autophagy and those exposed to proteasomal stress. Additionally, in unstressed cells co-expression of SQSTM1 62 reduces the amount of Ajuba present in the nucleus. SQSTM1 62 with an intact ubiquitin-associated domain forms holding complexes with Ajuba that are not destined for degradation yet inhibit signalling. Thus, in situations with altered levels and localization of SQSTM1 62 expression, such as osteoclasts in Paget’s disease of bone and various cancers, SQSTM1 62 may compartmentalize Ajuba and thereby impact its cellular functions and disease pathogenesis. In Paget’s, ubiquitin-associated domain mutations may lead to increased or prolonged Ajuba-induced NF-κB signalling leading to increased osteoclastogenesis. In cancer, Ajuba expression promotes cell survival. The increased levels of SQSTM1 62 observed in cancer may enhance Ajuba-mediated cancer cell survival.
Osteoblast-derived EGFL6 couples angiogenesis to osteogenesis during bone repair
Publisher: Ivyspring International Publisher
Date: 2021
DOI: 10.7150/THNO.60902
Myocyte Enhancer Factor 2 and Microphthalmia-associated Transcription Factor Cooperate with NFATc1 to Transactivate the V-ATPase d2 Promoter during RANKL-induced Osteoclastogenesis
Publisher: Elsevier BV
Date: 05-2009
Bafilomycin A1 Attenuates Osteoclast Acidification and Formation, Accompanied by Increased Levels of SQSTM1/p62 Protein
Publisher: Wiley
Date: 26-11-2015
DOI: 10.1002/JCB.25442
Abstract: Vacuolar proton pump H + ‐adenosine triphosphatases (V‐ATPases) play an important role in osteoclast function. Further understanding of the cellular and molecular mechanisms of V‐ATPase inhibition is vital for the development of anti‐resorptive drugs specifically targeting osteoclast V‐ATPases. In this study, we observed that bafilomycin A1, a naturally‐occurring inhibitor of V‐ATPases, increased the protein level of SQSTM1 62, a known negative regulator of osteoclast formation. Consistently, we found that bafilomycin A1 diminishes the intracellular accumulation of the acidotropic probe lysotracker in osteoclast‐like cells indicative of reduced acidification. Further, bafilomycin A1 inhibits osteoclast formation with attenuation of cell fusion and multi‐nucleation of osteoclast‐like cells during osteoclast differentiation. Taken together, these data indicate that bafilomycin A1 attenuates osteoclast differentiation in part via increased levels of SQSTM1 62 protein, providing further mechanistic insight into the effect of V‐ATPase inhibition in osteoclasts. J. Cell. Biochem. 117: 1464–1470, 2016. © 2015 Wiley Periodicals, Inc.
Correction: Glucocorticoid impairs cell-cell communication by autophagy-mediated degradation of connexin 43 in osteocytes
Publisher: Impact Journals, LLC
Date: 18-06-2019
Proteasome inhibitors impair RANKL‐induced NF‐κB activity in osteoclast‐like cells via disruption of p62, TRAF6, CYLD, and IκBα signaling cascades
Publisher: Wiley
Date: 13-04-2009
DOI: 10.1002/JCP.21787
Abstract: Proteasome inhibitors represent a promising therapy for the treatment of relapsed and/or refractory multiple myeloma, a disease that is concomitant with osteolysis and enhanced osteoclast formation. While blockade of the proteosome pathway has been recently shown to influence osteoclast formation and function, the precise molecular cascade underlying these effects is presently unclear. Here, we provide evidence that proteasome inhibitors directly impair osteoclast formation and function via the disruption of key RANK-mediated signaling cascades. Disruption of the proteosome pathway using selective inhibitors (MG-132, MG-115, and epoxomicin) resulted in the accumulation of p62 and CYLD, and altered the subcellular targeting and distribution of p62 and TRAF6 in osteoclast-like cells. Proteosome inhibition also blocked RANKL-induced NF-kappaB activation, IkappaBalpha degradation and nuclear translocation of p65. The disruption in RANK-signaling correlated dose-dependently with an impairment in osteoclastogenesis, with relative potency epoxomicin > MG-132 > MG-115 based on equimolar concentrations. In addition, these inhibitors were found to impact osteoclastic microtubule organization and attenuate bone resorption. Based on these data we propose that deregulation of key RANK-mediated signaling cascades (p62, TRAF6, CYLD, and IkappaBalpha) underscores proteasome-mediated inhibition of osteolytic bone conditions.
Targeted sequencing of DCSTAMP in familial Paget's disease of bone
Publisher: Elsevier BV
Date: 06-2019
Leveraging osteoclast genetic regulatory data to identify genes with a role in osteoarthritis
Publisher: Oxford University Press (OUP)
Date: 14-08-2023
Abstract: There has been a growing interest in the role of the subchondral bone and its resident osteoclasts in the progression of osteoarthritis (OA). A recent genome-wide association study (GWAS) identified 100 independent association signals for OA traits. Most of these signals are led by noncoding variants, suggesting that genetic regulatory effects may drive many of the associations. We have generated a unique human osteoclast-like cell-specific expression quantitative trait locus (eQTL) resource for studying the genetics of bone disease. Considering the potential role of osteoclasts in the pathogenesis of OA, we performed an integrative analysis of this dataset with the recently published OA GWAS results. Summary data-based Mendelian randomization (SMR) and colocalization analyses identified 38 genes with a potential role in OA, including some that have been implicated in Mendelian diseases with joint/skeletal abnormalities, such as BICRA, EIF6, CHST3, and FBN2. Several OA GWAS signals demonstrated colocalization with more than one eQTL peak, including at 19q13.32 (hip OA with BCAM, PRKD2, and BICRA eQTL). We also identified a number of eQTL signals colocalizing with more than one OA trait, including FAM53A, GCAT, HMGN1, MGAT4A, RRP7BP, and TRIOBP. An SMR analysis identified 3 loci with evidence of pleiotropic effects on OA-risk and gene expression: LINC01481, CPNE1, and EIF6. Both CPNE1 and EIF6 are located at 20q11.22, a locus harboring 2 other strong OA candidate genes, GDF5 and UQCC1, suggesting the presence of an OA-risk gene cluster. In summary, we have used our osteoclast-specific eQTL dataset to identify genes potentially involved with the pathogenesis of OA.
Mutations within the TNF-Like Core Domain of RANKL Impair Osteoclast Differentiation and Activation
Publisher: The Endocrine Society
Date: 2009
DOI: 10.1210/ME.2007-0465
Septins are critical regulators of osteoclastic bone resorption
Publisher: Springer Science and Business Media LLC
Date: 29-08-2018
DOI: 10.1038/S41598-018-31159-1
Abstract: Septins are known to play key roles in supporting cytoskeletal stability, vesicular transport, endo-/exocytosis, stabilizing cellular membranes and forming diffusion barriers. Their function in mammalian cells is poorly investigated. The osteoclast offers an interesting tool to investigate septins because all cellular activities septins were reported to be involved in are critical for osteoclasts. However, the existence of septins in osteoclasts has not even been reported. Here we show that the SEPT9 gene and Septin 9 (SEPT9) protein are expressed and synthesized during differentiation of human osteoclasts. Pharmacological stabilization of septin filaments dose dependently inhibits bone resorption of human osteoclasts in vitro suggesting a role for septins in bone resorption. Attesting to this, conditional deletion of Sept9 in mice leads to elevated levels of trabecular bone and diminished femoral growth in vivo . Finally, systematic interrogation of the spatial organization of SEPT9 by confocal microscopy reveals that SEPT9 is closely associated to the structures known to be critical for osteoclast activity. We propose that septins in general and SEPT9 in particular play a previously unappreciated role in osteoclastic bone resorption.
Steroid-induced osteonecrosis of the femoral head reveals enhanced reactive oxygen species and hyperactive osteoclasts
Publisher: Ivyspring International Publisher
Date: 2020
DOI: 10.7150/IJBS.40917
Membrane Transport Proteins in Osteoclasts: The Ins and Outs
Publisher: Frontiers Media SA
Date: 26-02-2021
DOI: 10.3389/FCELL.2021.644986
Abstract: During bone resorption, the osteoclast must sustain an extraordinarily low pH environment, withstand immense ionic pressures, and coordinate nutrient and waste exchange across its membrane to sustain its unique structural and functional polarity. To achieve this, osteoclasts are equipped with an elaborate set of membrane transport proteins (pumps, transporters and channels) that serve as molecular ‘gatekeepers’ to regulate the bilateral exchange of ions, amino acids, metabolites and macromolecules across the ruffled border and basolateral domains. Whereas the importance of the vacuolar-ATPase proton pump and chloride voltage-gated channel 7 in osteoclasts has long been established, comparatively little is known about the contributions of other membrane transport proteins, including those categorized as secondary active transporters. In this Special Issue review, we provide a contemporary update on the ‘ins and outs’ of membrane transport proteins implicated in osteoclast differentiation, function and bone homeostasis and discuss their therapeutic potential for the treatment of metabolic bone diseases.
V-ATPases in osteoclasts: Structure, function and potential inhibitors of bone resorption
Publisher: Elsevier BV
Date: 09-2012
DOI: 10.1016/J.BIOCEL.2012.05.014
Abstract: The vacuolar-type H(+)-ATPase (V-ATPase) proton pump is a macromolecular complex composed of at least 14 subunits organized into two functional domains, V(1) and V(0). The complex is located on the ruffled border plasma membrane of bone-resorbing osteoclasts, mediating extracellular acidification for bone demineralization during bone resorption. Genetic studies from mice to man implicate a critical role for V-ATPase subunits in osteoclast-related diseases including osteopetrosis and osteoporosis. Thus, the V-ATPase complex is a potential molecular target for the development of novel anti-resorptive agents useful for the treatment of osteolytic diseases. Here, we review the current structure and function of V-ATPase subunits, emphasizing their exquisite roles in osteoclastic function. In addition, we compare several distinct classes of V-ATPase inhibitors with specific inhibitory effects on osteoclasts. Understanding the structure-function relationship of the osteoclast V-ATPase may lead to the development of osteoclast-specific V-ATPase inhibitors that may serve as alternative therapies for the treatment of osteolytic diseases.
Prevention of Wear Particle-Induced Osteolysis by a Novel V-ATPase Inhibitor Saliphenylhalamide through Inhibition of Osteoclast Bone Resorption
Publisher: Public Library of Science (PLoS)
Date: 11-04-2012
Cytoplasmic Terminus of Vacuolar Type Proton Pump Accessory Subunit Ac45 Is Required for Proper Interaction with V0 Domain Subunits and Efficient Osteoclastic Bone Resorption
Publisher: Elsevier BV
Date: 05-2008
Gene expression of vascular endothelial growth factor in giant cell tumors of bone
Publisher: Elsevier BV
Date: 07-2000
Abstract: The production of vascular endothelial growth factors (VEGF), a major cause of neoangiogenesis, is a prerequisite for tumor growth and invasion. VEGF have also been shown to be important for the formation of osteoclasts. Because giant cell tumors of bone (GCT) are frequently hypervascular and have the ability to recruit macrophages and multinucleated osteoclast-like giant cells, we evaluated the levels of VEGF gene transcript in several of these tumors using Northern blot analyses, semiquantitative reverse transcription polymerase chain reaction (RT-PCR), fluorescence in situ hybridization (FISH), and immunohistochemistry. Our results showed that three major isoforms of VEGF (121, 165, and 189) were expressed in all cases of GCT investigated, with isoform 121 transcripts the most abundant. By both FISH and immunohistochemistry, we have shown that VEGF was present in spindle-shaped stromal-like tumor cells, round macrophage-like cells, and osteoclast-like multinucleate giant cells. Moreover, we have shown that the levels of VEGF gene expression but not microvessel density correlated with Enneking's clinical stage of GCT. There were higher levels of VEGF gene expression in stage III GCT than in stage I/II GCT (P < .0357). In conclusion, our results indicate that overexpression of VEGF may be associated with the advanced stage of the neoplasm.
IBM Watson AI-enhanced search tool identifies novel candidate genes and provides insight into potential pathomechanisms of traumatic heterotopic ossification
Publisher: Elsevier BV
Date: 10-2023
GPCR Signaling and Trafficking: The Long and Short of It
Publisher: Elsevier BV
Date: 03-2017
Brief exposure to full length parathyroid hormone-related protein (PTHrP) causes persistent generation of cyclic AMP through an endocytosis-dependent mechanism
Publisher: Elsevier BV
Date: 11-2019
DOI: 10.1016/J.BCP.2019.113627
Abstract: Parathyroid hormone (PTH)-related protein (PTHrP) (gene name Pthlh) was discovered as the factor responsible for the humoral hypercalcemia of malignancy. It shares such sequence similarity with PTH in the amino-terminal region that the two are equally able to act through a single G protein-coupled receptor, PTH1R. A number of biological activities are ascribed to domains of PTHrP beyond the amino-terminal domain. PTH functions as a circulating hormone, but PTHrP is generated locally in many tissues including bone, where it acts as a paracrine factor on osteoblasts and osteocytes. The present study compares how PTH and PTHrP influence cyclic AMP (cAMP) formation through adenylyl cyclase, the first event in cell activation through PTH1R. Brief exposure to full length PTHrP(1-141) in several osteoblastic cell culture systems was followed by sustained adenylyl cyclase activity for more than an hour after ligand washout. This effect was dose-dependent and was not found with shorter PTHrP or PTH peptides even though they were fully able to activate adenylyl cyclase with acute treatment. The persistent activation response to PTHrP(1-141) was seen also with later events in the cAMP/PKA pathway, including persistent activation of CRE-luciferase and sustained regulation of several CREB-responsive mRNAs, up to 24 h after the initial exposure. Pharmacologic blockade of endocytosis prevented the persistent activation of cAMP and gene responses. We conclude that full length PTHrP, the likely local physiological effector in bone, differs in intracellular action to PTH by undergoing endosomal translocation to induce a prolonged adenylyl cyclase activation in its target cells.
Glucocorticoid impairs cell-cell communication by autophagy-mediated degradation of connexin 43 in osteocytes
Publisher: Impact Journals, LLC
Date: 27-04-2016
Abstract: Osteocytes comprising over 90% of the bone cell population are highly susceptible to the adverse effects of glucocorticoids (GC) administration. Here we observed that Dexamethasone (Dex) induces a robust cytoskeleton rearrangement and decreases Cx43 protein expression in osteocyte-like MLO-Y4 cells. Using a Dmp1Cre-mT/mG osteocyte ex vivo culture system, we found significant shortening of dendritic processes in primary osteocytes following Dex administration. Loss of dendritic processes is a consequence of reduced Cx43 connectivity upon Dex induced autophagy in both RFP-GFP-LC3B transfected MLO-Y4 cells and primary calvarial osteocytes from LC3GFP transgenic mice. Upon the induction of autophagy by Dex, Cx43 was internalized into autophagosome/autolysosomes and degraded by autophagy. The degradation was attenuated following lysosomal inhibition using chloroquine (CLQ) and suppression of autophagy by Atg5 silencing. Inhibition Akt-mTORC1 signaling by Dex induces autophagy subsequently resulting in Cx43 degradation.Activation of Akt phosphorylation by IGF-1 attenuated Dex induced autophagy and degradation of Cx43. Together, we demonstrated that GC impair osteocyte cell-cell connectivity via autophagy mediated degradation of Cx43 through inhibition of the Akt-mTORC1 signaling. This may account for the deleterious effect of GC-induced bone loss.
Cyanidin Chloride inhibits ovariectomy‐induced osteoporosis by suppressing RANKL‐mediated osteoclastogenesis and associated signaling pathways
Publisher: Wiley
Date: 07-09-2017
DOI: 10.1002/JCP.26126
Abstract: Over-production and activation of osteoclasts is a common feature of osteolytic conditions such as osteoporosis, tumor-associated osteolysis, and inflammatory bone erosion. Cyanidin Chloride, a subclass of anthocyanin, displays antioxidant and anti-carcinogenesis properties, but its role in osteoclastic bone resorption and osteoporosis is not well understood. In this study, we showed that Cyanidin Chloride inhibits osteoclast formation, hydroxyapatite resorption, and receptor activator of NF-κB ligand (RANKL)-induced osteoclast marker gene expression including ctr, ctsk, and trap. Further investigation revealed that Cyanidin Chloride inhibits RANKL-induced NF-κB activation, suppresses the degradation of IκB-α and attenuates the phosphorylation of extracellular signal-regulated kinases (ERK). In addition, Cyanidin Chloride abrogated RANKL-induced calcium oscillations, the activation of nuclear factor of activated T cells calcineurin-dependent 1 (NFATc1), and the expression of c-Fos. Further, we showed that Cyanidin Chloride protects against ovariectomy-induced bone loss in vivo. Together our findings suggest that Cyanidin Chloride is capable of inhibiting osteoclast formation, hydroxyapatite resorption and RANKL-induced signal pathways in vitro and OVX-induced bone loss in vivo, and thus might have therapeutic potential for osteolytic diseases.
Disruption of the dynein‐dynactin complex unveils motor‐specific functions in osteoclast formation and bone resorption
Publisher: Wiley
Date: 18-12-2012
DOI: 10.1002/JBMR.1725
Abstract: Osteoclastic bone resorption requires strict interplay between acidified carrier vesicles, motor proteins, and the underlying cytoskeleton in order to sustain the specialized structural and functional polarization of the ruffled border. Cytoplasmic dynein, a large processive mechanochemical motor comprising heavy, intermediate, and light chains coupled to the dynactin cofactor complex, powers unilateral motility of erse cargos to microtubule minus-ends. We have recently shown that regulators of the dynein motor complex constitute critical components of the osteoclastic bone resorptive machinery. Here, by selectively modulating endogenous dynein activity, we show that the integrity of the dynein-dynactin motor complex is an essential requirement for both osteoclast formation and function. Systematic dissection of the osteoclast dynein-dynactin complex revealed that it is differentially localized throughout RANKL-induced osteoclast formation and activation, undergoing microtubule-coupled reorganization upon the establishment of cellular polarization. In osteoclasts actively resorbing bone, dynein-dynactin intimately co-localizes with the CAP-Gly domain-containing microtubule plus-end protein CLIP-170 at the resorptive front, thus orientating the ruffled border as a microtubule plus-end domain. Unexpectedly, disruption of the dynein-dynactin complex by exogenous p50/dynamitin expression retards osteoclast formation in vitro, owing largely to prolonged mitotic stasis of osteoclast progenitor cells. More importantly, loss of osteoclastic dynein activity results in a drastic redistribution of key intracellular organelles, including the Golgi and lysosomes, an effect that coincides with impaired cathepsin K secretion and diminished bone resorptive function. Collectively, these data unveil a previously unrecognized role for the dynein-dynactin motor complex in osteoclast formation and function, serving not only to regulate their timely maturation but also the delivery of osteolytic cargo that is essential to the bone resorptive process.
Membrane trafficking in osteoclasts and implications for osteoporosis
Publisher: Portland Press Ltd.
Date: 05-03-2019
DOI: 10.1042/BST20180445
Abstract: Osteoclasts are large multinucleated cells exquisitely adapted to resorb bone matrix. Like other eukaryotes, osteoclasts possess an elaborate ensemble of intracellular organelles through which solutes, proteins and other macromolecules are trafficked to their target destinations via membrane-bound intermediaries. During bone resorption, membrane trafficking must be tightly regulated to sustain the structural and functional polarity of the osteoclasts’ membrane domains. Of these, the ruffled border (RB) is most characteristic, functioning as the osteoclasts' secretory apparatus. This highly convoluted organelle is classically considered to be formed by the targeted fusion of acidic vesicles with the bone-facing plasma membrane. Emerging findings disclose new evidence that the RB is far more complex than previously envisaged, possessing discrete subdomains that are serviced by several intersecting endocytic, secretory, transcytotic and autophagic pathways. Bone-resorbing osteoclasts therefore serve as a unique model system for studying polarized membrane trafficking. Recent advances in high-resolution microscopy together with the convergence of genetic and cell biological studies in humans and in mice have helped illuminate the major membrane trafficking pathways in osteoclasts and unmask the core molecular machinery that governs these distinct vesicle transport routes. Among these, small Rab GTPases, their binding partners and members of the endocytic sorting nexin family have emerged as critical regulators. This mini review summarizes our current understanding of membrane trafficking in osteoclasts, the key molecular participants, and discusses how these transport machinery may be exploited for the development of new therapies for metabolic disorders of bone-like osteoporosis.
Paclitaxel inhibits osteoclast formation and bone resorption via influencing mitotic cell cycle arrest and RANKL‐induced activation of NF‐κB and ERK
Publisher: Wiley
Date: 20-01-2012
DOI: 10.1002/JCB.23423
Abstract: Pathological bone destruction (osteolysis) is a hallmark of many bone diseases including tumor metastasis to bone, locally osteolytic giant cell tumor (GCT) of bone, and Paget's disease. Paclitaxel is frequently prescribed in the treatment of several malignant tumors where it has been shown to exert beneficial effects on bone lesions. However, the mechanism(s) through which paclitaxel regulates osteoclast formation and function remain ill defined. In the present study, we demonstrate that paclitaxel dose-dependently inhibits receptor activator of nuclear factor-kappa B ligand (RANKL)-induced osteoclastogenesis in both RAW264.7 cells and mouse bone marrow macrophage (BMM) systems. In addition, paclitaxel treatment reduces the bone resorptive activity of human osteoclasts derived from GCT of bone, and attenuates lipopolysaccharide (LPS)-induced osteolysis in a mouse calvarial model. Complementary cellular and biochemical analyses revealed that paclitaxel induces mitotic arrest of osteoclastic precursor cells. Furthermore, luciferase reporter gene assays and western blot analysis indicate that paclitaxel modulates key RANKL-induced activation pathways that are essential to osteoclast formation including NF-κB and ERK. Collectively, our findings demonstrate a role for paclitaxel in the regulation of osteoclast formation and function and uncover potential mechanism(s) through which paclitaxel alleviates pathological osteolysis.
Mutations of vasopressin receptor 2 including novel L312S have differential effects on trafficking
Publisher: The Endocrine Society
Date: 08-2016
DOI: 10.1210/ME.2016-1002
A molecular code for endosomal recycling of phosphorylated cargos by the SNX27–retromer complex
Publisher: Springer Science and Business Media LLC
Date: 05-09-2016
DOI: 10.1038/NSMB.3290
Abstract: Recycling of internalized receptors from endosomal compartments is essential for the receptors' cell-surface homeostasis. Sorting nexin 27 (SNX27) cooperates with the retromer complex in the recycling of proteins containing type I PSD95-Dlg-ZO1 (PDZ)-binding motifs. Here we define specific acidic amino acid sequences upstream of the PDZ-binding motif required for high-affinity engagement of the human SNX27 PDZ domain. However, a subset of SNX27 ligands, such as the β
Decision letter: A trans-eQTL network regulates osteoclast multinucleation and bone mass
Publisher: eLife Sciences Publications, Ltd
Date: 06-03-2020
EGFL6 Promotes Endothelial Cell Migration and Angiogenesis through the Activation of Extracellular Signal-regulated Kinase
Publisher: Elsevier BV
Date: 06-2011
Molecular cloning of the mouse homologue of Rab3c
Publisher: Bioscientifica
Date: 08-2001
Abstract: Small GTP-binding proteins of the Rab subfamily are key regulators of intracellular vesicle transport. Here we report the isolation of a cDNA clone encoding the complete Rab3c isoform from mouse embryo using a degenerative PCR-based approach. Multiple sequence alignment revealed that the predicted amino acid sequence was identical to the previously identified rat Rab3c isoform and 98% identical to the published bovine Rab3c GTPase from brain. Furthermore by in situ hybridisation, Rab3c mRNA was detectable within various regions of the brain, cartilage and highly enriched within intestinal villi of foetal tissues. Chondrocytes in the hypertrophic zone, but not reserve or proliferative zones, expressed high levels of Rab3c. This pattern of expression corresponds with the genesis of matrix vesicles during endochondral ossification.In all, our results suggest that in addition to its functional role during regulated secretion in brain, Rab3c may play a part in matrix vesicle trafficking during skeletal development.
Bone Trans-omics: Integrating Omics to Unveil Mechanistic Molecular Networks Regulating Bone Biology and Disease
Publisher: Springer Science and Business Media LLC
Date: 06-07-2023
DOI: 10.1007/S11914-023-00812-8
Abstract: Recent advancements in “omics” technologies and bioinformatics have afforded researchers new tools to study bone biology in an unbiased and holistic way. The purpose of this review is to highlight recent studies integrating multi-omics data gathered from multiple molecular layers (i.e. trans-omics) to reveal new molecular mechanisms that regulate bone biology and underpin skeletal diseases. Bone biologists have traditionally relied on single-omics technologies (genomics, transcriptomics, proteomics, and metabolomics) to profile measureable differences (both qualitative and quantitative) of in idual molecular layers for biological discovery and to investigate mechanisms of disease. Recently, literature has grown on the implementation of integrative multi-omics to study bone biology, which combines computational and informatics support to connect multiple layers of data derived from in idual “omic” platforms. This emerging discipline termed “trans-omics” has enabled bone biologists to identify and construct detailed molecular networks, unveiling new pathways and unexpected interactions that have advanced our mechanistic understanding of bone biology and disease. While the era of trans-omics is poised to revolutionize our capacity to answer more complex and erse questions pertinent to bone pathobiology, it also brings new challenges that are inherent when trying to connect “Big Data” sets. A concerted effort between bone biologists and interdisciplinary scientists will undoubtedly be needed to extract physiologically and clinically meaningful data from bone trans-omics in order to advance its implementation in the field.
Tctex-1, a Novel Interaction Partner of Rab3D, Is Required for Osteoclastic Bone Resorption
Publisher: Informa UK Limited
Date: 04-2011
DOI: 10.1128/MCB.00834-10
Expression Quantitative Trait Locus Study of Bone Mineral Density GWAS Variants in Human Osteoclasts
Publisher: Wiley
Date: 24-03-2018
DOI: 10.1002/JBMR.3412
Abstract: Osteoporosis is a complex disease with a strong genetic component. Genomewide association studies (GWAS) have been very successful at identifying common genetic variants associated with bone parameters. A recently published study documented the results of the largest GWAS for bone mineral density (BMD) performed to date (n = 142,487), identifying 307 conditionally independent single-nucleotide polymorphisms (SNPs) as associated with estimated BMD (eBMD) at the genomewide significance level. The vast majority of these variants are non-coding SNPs. Expression quantitative trait locus (eQTL) studies using disease-specific cell types have increasingly been integrated with the results from GWAS to identify genes through which the observed GWAS associations are likely mediated. We generated a unique human osteoclast-specific eQTL data set using cells differentiated in vitro from 158 participants. We then used this resource to characterize the 307 recently identified BMD GWAS SNPs for association with nearby genes (±500 kb). After correction for multiple testing, 24 variants were found to be significantly associated with the expression of 32 genes in the osteoclast-like cells. Bioinformatics analysis suggested that these variants and those in strong linkage disequilibrium with them are enriched in regulatory regions. Several of the eQTL associations identified are relevant to genes that present strongly as having a role in bone, particularly IQGAP1, CYP19A1, CTNNB1, and COL6A3. Supporting evidence for many of the associations was obtained from publicly available eQTL data sets. We have also generated strong evidence for the presence of a regulatory region on chromosome 15q21.2 relevant to both the GLDN and CYP19A1 genes. In conclusion, we have generated a unique osteoclast-specific eQTL resource and have used this to identify 32 eQTL associations for recently identified BMD GWAS loci, which should inform functional studies of osteoclast biology. © 2018 American Society for Bone and Mineral Research.
Characterisation of genetic regulatory effects for osteoporosis risk variants in human osteoclasts
Publisher: Springer Science and Business Media LLC
Date: 26-03-2020
DOI: 10.1186/S13059-020-01997-2
Abstract: Osteoporosis is a complex disease with a strong genetic contribution. A recently published genome-wide association study (GWAS) for estimated bone mineral density (eBMD) identified 1103 independent genome-wide significant association signals. Most of these variants are non-coding, suggesting that regulatory effects may drive many of the associations. To identify genes with a role in osteoporosis, we integrate the eBMD GWAS association results with those from our previous osteoclast expression quantitative trait locus (eQTL) dataset. We identify sixty-nine significant cis -eQTL effects for eBMD GWAS variants after correction for multiple testing. We detect co-localisation of eBMD GWAS and osteoclast eQTL association signals for 21 of the 69 loci, implicating a number of genes including CCR5 , ZBTB38 , CPE , GNA12 , RIPK3 , IQGAP1 and FLCN . Summary-data-based Mendelian Randomisation analysis of the eBMD GWAS and osteoclast eQTL datasets identifies significant associations for 53 genes, with TULP4 presenting as a strong candidate for pleiotropic effects on eBMD and gene expression in osteoclasts. By performing analysis using the GARFIELD software, we demonstrate significant enrichment of osteoporosis risk variants among high-confidence osteoclast eQTL across multiple GWAS P value thresholds. Mice lacking one of the genes of interest, the apoptosis/necroptosis gene RIPK3 , show disturbed bone micro-architecture and increased osteoclast number, highlighting a new biological pathway relevant to osteoporosis. We utilise a unique osteoclast eQTL dataset to identify a number of potential effector genes for osteoporosis risk variants, which will help focus functional studies in this area.
In vitro Evaluation of Natural Marine Sponge Collagen as a Scaffold for Bone Tissue Engineering
Publisher: Ivyspring International Publisher
Date: 2011
DOI: 10.7150/IJBS.7.968
Perspective of the GEMSTONE Consortium on Current and Future Approaches to Functional Validation for Skeletal Genetic Disease Using Cellular, Molecular and Animal-Modeling Techniques
Publisher: Frontiers Media SA
Date: 30-11-2021
DOI: 10.3389/FENDO.2021.731217
Abstract: The availability of large human datasets for genome-wide association studies (GWAS) and the advancement of sequencing technologies have boosted the identification of genetic variants in complex and rare diseases in the skeletal field. Yet, interpreting results from human association studies remains a challenge. To bridge the gap between genetic association and causality, a systematic functional investigation is necessary. Multiple unknowns exist for putative causal genes, including cellular localization of the molecular function. Intermediate traits (“endophenotypes”), e.g. molecular quantitative trait loci (molQTLs), are needed to identify mechanisms of underlying associations. Furthermore, index variants often reside in non-coding regions of the genome, therefore challenging for interpretation. Knowledge of non-coding variance (e.g. ncRNAs), repetitive sequences, and regulatory interactions between enhancers and their target genes is central for understanding causal genes in skeletal conditions. Animal models with deep skeletal phenotyping and cell culture models have already facilitated fine mapping of some association signals, elucidated gene mechanisms, and revealed disease-relevant biology. However, to accelerate research towards bridging the current gap between association and causality in skeletal diseases, alternative in vivo platforms need to be used and developed in parallel with the current -omics and traditional in vivo resources. Therefore, we argue that as a field we need to establish resource-sharing standards to collectively address complex research questions. These standards will promote data integration from various -omics technologies and functional dissection of human complex traits. In this mission statement, we review the current available resources and as a group propose a consensus to facilitate resource sharing using existing and future resources. Such coordination efforts will maximize the acquisition of knowledge from different approaches and thus reduce redundancy and duplication of resources. These measures will help to understand the pathogenesis of osteoporosis and other skeletal diseases towards defining new and more efficient therapeutic targets.
Natural Germacrane Sesquiterpenes Inhibit Osteoclast Formation, Bone Resorption, RANKL-Induced NF-κB Activation, and IκBα Degradation
Publisher: MDPI AG
Date: 05-11-2015
Evidence that human cartilage and chondrocytes do not express calcitonin receptor
Publisher: Elsevier BV
Date: 04-2008
DOI: 10.1016/J.JOCA.2007.08.003
Abstract: Calcitonin (CT) has been recently shown to exhibit direct protective effects on articular cartilage against joint degenerative disease. It has been proposed that CT might act via the CT receptor (CTR) to activate the cyclic AMP (cAMP) pathway and protect type II collagen degradation. In this study, we investigated the existence of CTR in human articular cartilage and chondrocytes, and examined the potential pharmacological effects and transduction pathway of salmon CT (sCT) in human chondrocytes. Five human articular cartilage s les were examined for the expression of the CTR by polymerase chain reaction (PCR), immunostaining and Western blot analysis. cAMP levels in human chondrocyte stimulated with sCT were assessed by ELISA. The effect of sCT on the gene expression profiles, including aggrecan, type II collagen, MMP-1, MMP-3 and MMP-13, of human chondrocytes was also examined by relative quantitative Real-time PCR. We failed to detect the CTR at both the transcriptional and protein levels in human chondrocytes and cartilage tissue by PCR, immunostaining and Western blotting. cAMP levels were significantly elevated in human chondrocytes by forskolin (100muM) to more than 10-fold (P<0.001), however, were not induced by sCT (10(-7)M, 10(-8)M, 10(-9)M). Real-time PCR analysis demonstrated that sCT slightly reduced the gene expression of MMPs, although this effect was not statistically significant. In contrary to previous reports, our data indicate that human cartilage and chondrocytes do not express CTR. Furthermore, sCT does not appear to have direct effects on human chondrocytes. We propose that the chondroprotective effect of CT observed in vivo may be indirect via its impact on subchondral bone resorptive activity of osteoclasts.
SC-514, a selective inhibitor of IKKβ attenuates RANKL-induced osteoclastogenesis and NF-κB activation
Publisher: Elsevier BV
Date: 12-2013
DOI: 10.1016/J.BCP.2013.09.017
Abstract: The RANKL-induced NF-κB signaling pathway is essential for osteoclastogenesis. This study aims to identify specific inhibitors targeting NF-κB signaling pathway, which might serve as useful small molecule inhibitors for the treatment and alleviation of osteoclast-mediated bone lytic diseases. By screening for compounds that selectively inhibit RANKL-induced NF-κB activation in RAW264.7 cells as monitored by luciferase reporter gene assay, we identified SC-514, a specific inhibitor of IKKβ, as a candidate compound targeting osteoclastogenesis. SC-514 dose-dependently inhibits RANKL-induced osteoclastogenesis with an IC50 of <5μM. At high concentrations, SC-514 (≥12.5μM) induced apoptosis and caspase 3 activation in RAW264.7 cells. Moreover, SC-514 specifically suppressed NF-κB activity owing to delayed RANKL-induced degradation of IκBα and inhibition of p65 nuclear translocation. Taken together, our results indicate that SC-514 impairs RANKL-induced osteoclastogenesis and NF-κB activation. Thus, targeting IKKβ by SC-514 presents as a potential treatment for osteoclast-related disorders such as osteoporosis and cancer-induced bone loss.
LIS1 Regulates Osteoclast Formation and Function through Its Interactions with Dynein/Dynactin and Plekhm1
Publisher: Public Library of Science (PLoS)
Date: 03-11-2011
Choline kinase β mutant mice exhibit reduced phosphocholine, elevated osteoclast activity, and low bone mass
Publisher: Elsevier BV
Date: 2015
The oncogene AAMDC links PI3K-AKT-mTOR signaling with metabolic reprograming in estrogen receptor-positive breast cancer
Publisher: Springer Science and Business Media LLC
Date: 26-03-2021
DOI: 10.1038/S41467-021-22101-7
Abstract: Adipogenesis associated Mth938 domain containing (AAMDC) represents an uncharacterized oncogene lified in aggressive estrogen receptor-positive breast cancers. We uncover that AAMDC regulates the expression of several metabolic enzymes involved in the one-carbon folate and methionine cycles, and lipid metabolism. We show that AAMDC controls PI3K-AKT-mTOR signaling, regulating the translation of ATF4 and MYC and modulating the transcriptional activity of AAMDC -dependent promoters. High AAMDC expression is associated with sensitization to dactolisib and everolimus, and these PI3K-mTOR inhibitors exhibit synergistic interactions with anti-estrogens in IntClust2 models. Ectopic AAMDC expression is sufficient to activate AKT signaling, resulting in estrogen-independent tumor growth. Thus, AAMDC -overexpressing tumors may be sensitive to PI3K-mTORC1 blockers in combination with anti-estrogens. Lastly, we provide evidence that AAMDC can interact with the RabGTPase-activating protein RabGAP1L, and that AAMDC, RabGAP1L, and Rab7a colocalize in endolysosomes. The discovery of the RabGAP1L-AAMDC assembly platform provides insights for the design of selective blockers to target malignancies having the AAMDC lification.
Evidence of reciprocal regulation between the high extracellular calcium and RANKL signal transduction pathways in RAW cell derived osteoclasts
Publisher: Wiley
Date: 17-08-2004
DOI: 10.1002/JCP.20159
Abstract: During bone resorption, osteoclasts are exposed to high Ca2+ concentrations (up to 40 mM). The role of high extracellular Ca2+ in receptor activator of NF-kappaB ligand (RANKL)-mediated osteoclast survival and their functional interrelationship is unclear. In this study, we show that RANKL enhances osteoclast tolerance to high extracellular Ca2+ by protecting the cell from cell death in a dose dependent manner. We have provided evidence that RANKL does this by attenuating high extracellular Ca2+-induced Ca2+ elevations. Moreover, we have found that high extracellular Ca2+-induced cell death was partially inhibited by a caspase-3 inhibitor, suggesting caspase-3-mediated apoptosis is involved. Conversely, using reporter gene assays and Western blot analysis, we have demonstrated that high extracellular Ca2+ desensitizes the RANKL-induced activation of NF-kappaB and c-Jun N-terminal kinase (JNK), and inhibits constitutive and RANKL-stimulated ERK phosphorylation, indicating a negative feed-back mechanism via specific RANKL signaling pathways. Taken together, this study provides evidence for a reciprocal regulation between high extracellular Ca2+ and RANKL signaling in RAW cell derived osteoclasts. Our data imply a cross talk mechanism of extracellular Ca2+ on osteoclast survival through the regulation of RANKL.
Functional Assessment of Calcium-Sensing Receptor Variants Confirms Familial Hypocalciuric Hypercalcemia
Publisher: The Endocrine Society
Date: 18-02-2022
Abstract: In the clinic it is important to differentiate primary hyperparathyroidism (PHPT) from the more benign, inherited disorder, familial hypocalciuric hypercalcemia (FHH). Since the conditions may sometimes overlap biochemically, identification of calcium-sensing receptor (CASR) gene variants causative of FHH (but not PHPT) is the most decisive diagnostic aid. When novel variants are identified, bioinformatics and functional assessment are required to establish pathogenicity. We identified 3 novel CASR transmembrane domain missense variants, Thr699Asn, Arg701Gly, and Thr808Pro, in 3 probands provisionally diagnosed with FHH and examined the variants using bioinformatics and functional analysis. Bioinformatics assessment utilized wANNOVAR software. For functional characterization, each variant was cloned into a mammalian expression vector wild-type and variant receptors were transfected into HEK293 cells, and their expression and cellular localization were assessed by Western blotting and confocal immunofluorescence, respectively. Receptor activation in HEK293 cells was determined using an IP-One ELISA assay following stimulation with Ca++ ions. Bioinformatics analysis of the variants was unable to definitively assign pathogenicity. Compared with wild-type receptor, all variants demonstrated impaired expression of mature receptor reaching the cell surface and diminished activation at physiologically relevant Ca++ concentrations. Three CASR missense variants identified in probands provisionally diagnosed with FHH result in receptor inactivation and are therefore likely causative of FHH. Inactivation may be due to inadequate processing/trafficking of mature receptor and/or conformational changes induced by the variants affecting receptor signaling. This study demonstrates the value of functional studies in assessing genetic variants identified in hypercalcemic patients.
Prognosis for splicing factor PRPF8 retinitis pigmentosa, novel mutations and correlation between human and yeast phenotypes
Publisher: Hindawi Limited
Date: 15-03-2010
DOI: 10.1002/HUMU.21236
Abstract: PRPF8-retinitis pigmentosa is said to be severe but there has been no overview of phenotype across different mutations. We screened RP patients for PRPF8 mutations and identified three new missense mutations, including the first documented mutation outside exon 42 and the first de novo mutation. This brings the known RP-causing mutations in PRPF8 to nineteen. We then collated clinical data from new and published cases to determine an accurate prognosis for PRPF8-RP. Clinical data for 75 PRPF8-RP patients were compared, revealing that while the effect on peripheral retinal function is severe, patients generally retain good visual acuity in at least one eye until the fifth or sixth decade. We also noted that prognosis for PRPF8-RP differs with different mutations, with p.H2309P or p.H2309R having a worse prognosis than p.R2310K. This correlates with the observed difference in growth defect severity in yeast lines carrying the equivalent mutations, though such correlation remains tentative given the limited number of mutations for which information is available. The yeast phenotype is caused by lack of mature spliceosomes in the nucleus, leading to reduced RNA splicing function. Correlation between yeast and human phenotypes suggests that splicing factor RP may also result from an underlying splicing deficit.
Identical subchondral bone microarchitecture pattern with increased bone resorption in rheumatoid arthritis as compared to osteoarthritis
Publisher: Elsevier BV
Date: 12-2014
DOI: 10.1016/J.JOCA.2014.08.015
Abstract: To analyze the differences in microarchitecture and bone remodeling of subchondral bone in femoral heads from patients with rheumatoid arthritis (RA) and osteoarthritis (OA). Peri-articular bone s les, including subchondral trabecular bone (STB) and deeper trabecular bone (DTB) were extracted from the load-bearing region of femoral heads from 20 patients with RA and 40 patients with OA during hip replacement surgery. Micro-CT, histomorphometry and backscatter scanning electron microscopy (BSEM) were performed to assess microarchitecture and bone histology parameters. In both RA and OA, STB showed more sclerotic microarchitecture and more active bone remodeling, compared to DTB. RA and OA showed similar microarchitecture characteristics in both STB and DTB, despite STB in RA exhibiting higher bone resorption. In addition, there was no difference in the frequency of bone cysts in STB between RA and OA. In STB, the trabecular bone surrounding subchondral bone cysts (Cys-Tb) was more sclerotic than the trabecular bone found distant to cysts (Peri-Tb), with a higher level of bone remodeling. Both Cys-Tb region and Peri-Tb region were detected to have similar microarchitectural and bone remodeling characteristics in RA and OA. Apart from higher bone resorption in the general subchondral bone of RA s les, the peri-articular bone exhibited similar microarchitectural and bone remodeling characteristics in RA and OA.
Sorting nexin 27 couples PTHR trafficking to retromer for signal regulation in osteoblasts during bone growth
Publisher: American Society for Cell Biology (ASCB)
Date: 15-04-2016
Abstract: The parathyroid hormone 1 receptor (PTHR) is central to the process of bone formation and remodeling. PTHR signaling requires receptor internalization into endosomes, which is then terminated by recycling or degradation. Here we show that sorting nexin 27 (SNX27) functions as an adaptor that couples PTHR to the retromer trafficking complex. SNX27 binds directly to the C-terminal PDZ-binding motif of PTHR, wiring it to retromer for endosomal sorting. The structure of SNX27 bound to the PTHR motif reveals a high-affinity interface involving conserved electrostatic interactions. Mechanistically, depletion of SNX27 or retromer augments intracellular PTHR signaling in endosomes. Osteoblasts genetically lacking SNX27 show similar disruptions in PTHR signaling and greatly reduced capacity for bone mineralization, contributing to profound skeletal deficits in SNX27-knockout mice. Taken together, our data support a critical role for SNX27-retromer mediated transport of PTHR in normal bone development.
Osteoclasts recycle via osteomorphs during RANKL-stimulated bone resorption
Publisher: Elsevier BV
Date: 03-2021
The GTPase Rab26 links synaptic vesicles to the autophagy pathway
Publisher: eLife Sciences Publications, Ltd
Date: 02-02-2015
DOI: 10.7554/ELIFE.05597
Abstract: Small GTPases of the Rab family not only regulate target recognition in membrane traffic but also control other cellular functions such as cytoskeletal transport and autophagy. Here we show that Rab26 is specifically associated with clusters of synaptic vesicles in neurites. Overexpression of active but not of GDP-preferring Rab26 enhances vesicle clustering, which is particularly conspicuous for the EGFP-tagged variant, resulting in a massive accumulation of synaptic vesicles in neuronal somata without altering the distribution of other organelles. Both endogenous and induced clusters co-localize with autophagy-related proteins such as Atg16L1, LC3B and Rab33B but not with other organelles. Furthermore, Atg16L1 appears to be a direct effector of Rab26 and binds Rab26 in its GTP-bound form, albeit only with low affinity. We propose that Rab26 selectively directs synaptic and secretory vesicles into preautophagosomal structures, suggesting the presence of a novel pathway for degradation of synaptic vesicles.
A missense mutation sheds light on a novel structure–function relationship of RANKL
Publisher: Wiley
Date: 23-09-2021
DOI: 10.1002/JCP.30045
Abstract: The tumor necrosis factor (TNF)‐like core domain of receptor activator of nuclear factor‐κB ligand (RANKL) is a functional domain critical for osteoclast differentiation. One of the missense mutations identified in patients with osteoclast‐poor autosomal recessive osteopetrosis (ARO) is located in residue methionine 199 that is replaced with lysine (M199K) amid the TNF‐like core domain. However, the structure–function relationship of this mutation is not clear. Sequence‐based alignment revealed that the fragment containing human M199 is highly conserved and equivalent to M200 in rat. Using site‐directed mutagenesis, we generated three recombinant RANKL mutants M200K/A/E (M200s) by replacing the methionine 200 with lysine (M200K), alanine (M200A), and glutamic acid (M200E), representative of distinct physical properties. TRAcP staining and bone pit assay showed that M200s failed to support osteoclast formation and bone resorption, accompanied by impaired osteoclast‐related signal transduction. However, no antagonistic effect was found in M200s against wild‐type rat RANKL. Analysis of the crystal structure of RANKL predicted that this methionine residue is located within the hydrophobic core of the protein, thus, likely to be crucial for protein folding and stability. Consistently, differential scanning fluorimetry analysis suggested that M200s were less stable. Western blot analysis analyses further revealed impaired RANKL trimerization by M200s. Furthermore, receptor–ligand binding assay displayed interrupted interaction of M200s to its intrinsic receptors. Collectively, our studies revealed the molecular basis of human M199‐induced ARO and elucidated the indispensable role of rodent residue M200 (equivalent to human M199) for the RANKL function.
Sugar transporter Slc37a2 regulates bone metabolism in mice via a tubular lysosomal network in osteoclasts
Publisher: Springer Science and Business Media LLC
Date: 21-02-2023
DOI: 10.1038/S41467-023-36484-2
Abstract: Osteoclasts are giant bone-digesting cells that harbor specialized lysosome-related organelles termed secretory lysosomes (SLs). SLs store cathepsin K and serve as a membrane precursor to the ruffled border, the osteoclast’s ‘resorptive apparatus’. Yet, the molecular composition and spatiotemporal organization of SLs remains incompletely understood. Here, using organelle-resolution proteomics, we identify member a2 of the solute carrier 37 family (Slc37a2) as a SL sugar transporter. We demonstrate in mice that Slc37a2 localizes to the SL limiting membrane and that these organelles adopt a hitherto unnoticed but dynamic tubular network in living osteoclasts that is required for bone digestion. Accordingly, mice lacking Slc37a2 accrue high bone mass owing to uncoupled bone metabolism and disturbances in SL export of monosaccharide sugars, a prerequisite for SL delivery to the bone-lining osteoclast plasma membrane. Thus, Slc37a2 is a physiological component of the osteoclast’s unique secretory organelle and a potential therapeutic target for metabolic bone diseases.
Calmodulin interacts with Rab3D and modulates osteoclastic bone resorption
Publisher: Springer Science and Business Media LLC
Date: 29-11-2016
DOI: 10.1038/SREP37963
Abstract: Calmodulin is a highly versatile protein that regulates intracellular calcium homeostasis and is involved in a variety of cellular functions including cardiac excitability, synaptic plasticity and signaling transduction. During osteoclastic bone resorption, calmodulin has been reported to concentrate at the ruffled border membrane of osteoclasts where it is thought to modulate bone resorption activity in response to calcium. Here we report an interaction between calmodulin and Rab3D, a small exocytic GTPase and established regulator osteoclastic bone resorption. Using yeast two-hybrid screening together with a series of protein-protein interaction studies, we show that calmodulin interacts with Rab3D in a calcium dependent manner. Consistently, expression of a calcium insensitive form of calmodulin (i.e. CaM1234) perturbs calmodulin-Rab3D interaction as monitored by bioluminescence resonance energy transfer (BRET) assays. In osteoclasts, calmodulin and Rab3D are constitutively co-expressed during RANKL-induced osteoclast differentiation, co-occupy plasma membrane fractions by differential gradient sedimentation assay and colocalise in the ruffled border as revealed by confocal microscopy. Further, functional blockade of calmodulin-Rab3D interaction by calmidazolium chloride coincides with an attenuation of osteoclastic bone resorption. Our data imply that calmodulin- Rab3D interaction is required for efficient bone resorption by osteoclasts in vitro .
Subchondral bone in osteoarthritis: insight into risk factors and microstructural changes
Publisher: Springer Science and Business Media LLC
Date: 2013
DOI: 10.1186/AR4405
Alexidine Dihydrochloride Attenuates Osteoclast Formation and Bone Resorption and Protects Against LPS‐Induced Osteolysis
Publisher: Wiley
Date: 06-01-2016
DOI: 10.1002/JBMR.2710
Abstract: Aseptic loosening and periprosthetic infection leading to inflammatory osteolysis is a major complication associated with total joint arthroplasty (TJA). The liberation of bacterial products and/or implant-derived wear particles activates immune cells that produce pro-osteoclastogenic cytokines that enhance osteoclast recruitment and activity, leading to bone destruction and osteolysis. Therefore, agents that prevent the inflammatory response and/or attenuate excessive osteoclast (OC) formation and bone resorption offer therapeutic potential by prolonging the life of TJA implants. Alexidine dihydrochloride (AD) is a bisbiguanide compound commonly used as an oral disinfectant and in contact lens solutions. It possesses antimicrobial, anti-inflammatory and anticancer properties however, its effects on OC biology are poorly described. Here, we demonstrate that AD inhibits OC formation and bone resorption in vitro and exert prophylatic protection against LPS-induced osteolysis in vivo. Biochemical analysis demonstrated that AD suppressed receptor activator of NF-κB ligand (RANKL)-induced activation of mitogen-activated protein kinases (ERK, p38, and JNK), leading to the downregulation of NFATc1. Furthermore, AD disrupted F-actin ring formation and attenuated the ability of mature OC to resorb bone. Collectively, our findings suggest that AD may be a promising prophylactic anti-osteoclastic/resorptive agent for the treatment of osteolytic diseases caused by excessive OC formation and function.
Loss of Protein Kinase C-δ Protects against LPS-Induced Osteolysis Owing to an Intrinsic Defect in Osteoclastic Bone Resorption
Publisher: Public Library of Science (PLoS)
Date: 08-08-2013
Autologous Tenocyte Therapy for Experimental Achilles Tendinopathy in a Rabbit Model
Publisher: Mary Ann Liebert Inc
Date: 08-2011
Phosphorylation-regulated axonal dependent transport of syntaxin 1 is mediated by a Kinesin-1 adapter.
Publisher: Proceedings of the National Academy of Sciences
Date: 26-03-2012
Abstract: Presynaptic nerve terminals are formed from preassembled vesicles that are delivered to the prospective synapse by kinesin-mediated axonal transport. However, precisely how the various cargoes are linked to the motor proteins remains unclear. Here, we report a transport complex linking syntaxin 1a (Stx) and Munc18, two proteins functioning in synaptic vesicle exocytosis at the presynaptic plasma membrane, to the motor protein Kinesin-1 via the kinesin adaptor FEZ1. Mutation of the FEZ1 ortholog UNC-76 in Caenorhabditis elegans causes defects in the axonal transport of Stx. We also show that binding of FEZ1 to Kinesin-1 and Munc18 is regulated by phosphorylation, with a conserved site (serine 58) being essential for binding. When expressed in C. elegans , wild-type but not phosphorylation-deficient FEZ1 (S58A) restored axonal transport of Stx. We conclude that FEZ1 operates as a kinesin adaptor for the transport of Stx, with cargo loading and unloading being regulated by protein kinases.
Triptolide inhibits osteoclast formation, bone resorption, RANKL-mediated NF-қB activation and titanium particle-induced osteolysis in a mouse model
Publisher: Elsevier BV
Date: 2015
DOI: 10.1016/J.MCE.2014.10.016
Abstract: The RANKL-induced NF-κB signaling pathway is required for osteoclast formation and function. By screening for compounds that inhibit RANKL-induced NF-κB activation using a luciferase reporter gene assay in RAW264.7 cells, we identified triptolide (PG490), as a candidate compound targeting osteoclast differentiation and osteoclast-mediated osteolysis. Triptolide (PG490) is an active compound of the medicinal herb Tripterygium wilfordii Hook F (TWHF) or Lei Gong Teng with known anti-inflammatory properties. We found that triptolide inhibited osteoclastogenesis and bone resorption, as well as RANKL-induced NF-қB activities as monitored by luciferase reporter gene assays and the nuclear translocation of p65. In vivo studies showed that triptolide attenuates titanium-induced osteolysis and osteoclast formation in a mouse calvarial model. Considering that drugs which protect against localized bone loss are critically needed for the effective treatment of particle-induced osteolysis, our data suggest that triptolide might have therapeutic potential for the treatment of bone lytic diseases caused by prosthetic wear particles.
Abstract
Publisher: eLife Sciences Publications, Ltd
Date: 2014
Circulating lipocalin-2 and features of metabolic syndrome in community-dwelling older women
Publisher: Elsevier BV
Date: 11-2023
Long-term exposure of mice to 890 ppm atmospheric CO2 alters growth trajectories and elicits hyperactive behaviours in young adulthood
Publisher: Wiley
Date: 23-11-2022
DOI: 10.1113/JP282179
Abstract: Atmospheric carbon dioxide (CO 2 ) levels are currently at 418 parts per million (ppm), and by 2100 may exceed 900 ppm. The biological effects of lifetime exposure to CO 2 at these levels is unknown. Previously we have shown that mouse lung function is altered by long‐term exposure to 890 ppm CO 2 . Here, we assess the broader systemic physiological responses to this exposure. Mice were exposed to either 460 or 890 ppm from preconception to 3 months of age, and assessed for effects on developmental, renal and osteological parameters. Locomotor, memory, learning and anxiety‐like behaviours of the mice were also assessed. Exposure to 890 ppm CO 2 increased birthweight, decreased female body weight after weaning, and, as young adults, resulted in reduced engagement in memory/learning tasks, and hyperactivity in both sexes in comparison to controls. There were no clear anxiety, learning or memory changes. Renal and osteological parameters were minimally affected. Overall, this study shows that exposure of mice to 890 ppm CO 2 from preconception to young adulthood alters growth and some behaviours, with limited evidence of compensatory changes in acid–base balance. These findings highlight the potential for a direct effect of increased atmospheric CO 2 on mammalian health outcomes. image Long‐term exposure to elevated levels of atmospheric CO 2 is an uncontrolled experiment already underway. This is the first known study to assess non‐respiratory physiological impacts of long‐term (conception to young adulthood) exposure of mice to CO 2 at levels that may arise in the atmosphere due to global emissions. Exposure to elevated CO 2 , in comparison to control mice, altered growth patterns in early life and resulted in hyperactive behaviours in young adulthood. Renal and bone parameters, which are important to balance acid–base levels to compensate for increased CO 2 exposure, remained relatively unaffected. This work adds to the body of evidence regarding the effects of carbon emissions on mammalian health and highlights a potential future burden of disease.
Influence of age and gender on microarchitecture and bone remodeling in subchondral bone of the osteoarthritic femoral head
Publisher: Elsevier BV
Date: 08-2015
DOI: 10.1016/J.BONE.2015.04.019
Abstract: Age and gender have been reported to have a remarkable impact on bone homeostasis. However, subchondral bone, which plays a pivotal role in the initiation and progression of OA, has been poorly investigated. This study was to investigate age- and gender-related changes of microarchitecture and bone remodeling in subchondral bone in OA. Subchondral trabecular bone (STB) and deeper trabecular bone (DTB) specimens were extracted in the load-bearing region of femoral heads from 110 patients with OA. Micro-CT and histomorphometry were performed to analyze microarchitectural and bone remodeling changes of all specimens. Compared to DTB, STB showed more sclerotic microarchitecture, more active bone remodeling and higher frequency of bone cysts. There were no gender differences for both microarchitecture and bone remodeling in STB. However, gender differences were found in DTB, with thinner Tb.Th, higher Tb.N, higher OS/BV and ES/BV in males. In both STB and DTB, no correlation between microarchitecture and age was found in both genders. However, bone remodeling of STB increased significantly with age in males, while bone remodeling of DTB increased significantly with age in females. No age or gender preference was found in subchondral bone cyst (SBC) frequency. The cyst volume fraction was correlated with neither age nor gender. There were differences in microarchitecture and bone remodeling between STB and DTB, which may be due to the distinct biomechanical and biochemical functions of these two bone structures in maintaining joint homeostasis. OA changed the normal age- and gender-dependence of bone homeostasis in joints, in a site-specific manner.
Versatile Roles of V-ATPases Accessory Subunit Ac45 in Osteoclast Formation and Function
Publisher: Public Library of Science (PLoS)
Date: 04-11-2011
Staphylococcus aureus Infects Osteoclasts and Replicates Intracellularly
Publisher: American Society for Microbiology
Date: 29-10-2019
Abstract: The inflammation of bone tissue is called osteomyelitis, and most cases are caused by an infection with the bacterium Staphylococcus aureus . To date, the bone-building cells, osteoblasts, have been implicated in the progression of these infections, but not much is known about how the bone-resorbing cells, osteoclasts, participate. In this study, we show that S. aureus can infect osteoclasts and proliferate inside these cells, whereas bone-residing macrophages, immune cells related to osteoclasts, destroy the bacteria. These findings elucidate a unique role for osteoclasts to harbor bacteria during infection, providing a possible mechanism by which bacteria could evade destruction by the immune system.
Rheumatoid arthritis: pathological mechanisms and modern pharmacologic therapies.
Publisher: Springer Science and Business Media LLC
Date: 27-04-2018
DOI: 10.1038/S41413-018-0016-9
Abstract: Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease that primarily affects the lining of the synovial joints and is associated with progressive disability, premature death, and socioeconomic burdens. A better understanding of how the pathological mechanisms drive the deterioration of RA progress in in iduals is urgently required in order to develop therapies that will effectively treat patients at each stage of the disease progress. Here we dissect the etiology and pathology at specific stages: (i) triggering, (ii) maturation, (iii) targeting, and (iv) fulminant stage, concomitant with hyperplastic synovium, cartilage damage, bone erosion, and systemic consequences. Modern pharmacologic therapies (including conventional, biological, and novel potential small molecule disease-modifying anti-rheumatic drugs) remain the mainstay of RA treatment and there has been significant progress toward achieving disease remission without joint deformity. Despite this, a significant proportion of RA patients do not effectively respond to the current therapies and thus new drugs are urgently required. This review discusses recent advances of our understanding of RA pathogenesis, disease modifying drugs, and provides perspectives on next generation therapeutics for RA.
Osteal macrophages support osteoclast-mediated resorption and contribute to bone pathology in a postmenopausal osteoporosis mouse model
Publisher: Wiley
Date: 03-08-2021
DOI: 10.1002/JBMR.4413
Abstract: Osteal macrophages (osteomacs) support osteoblast function and promote bone anabolism, but their contribution to osteoporosis has not been explored. Although mouse ovariectomy (OVX) models have been repeatedly used, variation in strain, experimental design and assessment modalities have contributed to no single model being confirmed as comprehensively replicating the full gamut of osteoporosis pathological manifestations. We validated an OVX model in adult C3H/HeJ mice and demonstrated that it presents with human postmenopausal osteoporosis features with reduced bone volume in axial and appendicular bone and bone loss in both trabecular and cortical bone including increased cortical porosity. Bone loss was associated with increased osteoclasts on trabecular and endocortical bone and decreased osteoblasts on trabecular bone. Importantly, this OVX model was characterized by delayed fracture healing. Using this validated model, we demonstrated that osteomacs are increased post‐OVX on both trabecular and endocortical bone. Dual F4/80 (pan‐macrophage marker) and tartrate‐resistant acid phosphatase (TRAP) staining revealed osteomacs frequently located near TRAP + osteoclasts and contained TRAP + intracellular vesicles. Using an in vivo inducible macrophage depletion model that does not simultaneously deplete osteoclasts, we observed that osteomac loss was associated with elevated extracellular TRAP in bone marrow interstitium and increased serum TRAP. Using in vitro high‐resolution confocal imaging of mixed osteoclast‐macrophage cultures on bone substrate, we observed macrophages juxtaposed to osteoclast basolateral functional secretory domains scavenging degraded bone byproducts. These data demonstrate a role for osteomacs in supporting osteoclastic bone resorption through phagocytosis and sequestration of resorption byproducts. Overall, our data expose a novel role for osteomacs in supporting osteoclast function and provide the first evidence of their involvement in osteoporosis pathogenesis. © 2021 American Society for Bone and Mineral Research (ASBMR).
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Max Planck Institute For Comparative Public Law And International Law
Location: Germany
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Linkage Projects - Grant ID: LP210200876
Start Date: 07-2023
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