ORCID Profile
0000-0002-5652-1687
Current Organisations
Wageningen University & Research
,
Nanyang Technological University
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: Wiley
Date: 08-06-2011
Abstract: Identifying the substrates and biochemical pathway regulated by phosphatases has always been more challenging than finding those regulated by kinases. Here, we report the use of phosphoproteomic methods to analyse the pathways regulated by POPX2 (partner of PIX 2) phosphatase. POPX2 is a serine/threonine phosphatase, found in many cancer types. The levels of the POPX2 have been found to be up-regulated in the more invasive breast cancer cells compared with non-invasive ones. Our observations also suggest that POPX2 level is positively correlated with cell motility. Thus, finding substrates or pathways regulated by POPX2 will help to elucidate the regulatory mechanism of cancer cell motility and invasiveness. We have also developed and validated a protocol using electrostatic repulsion-hydrophilic interaction chromatography (ERLIC) to enrich the phosphopeptides followed by LC-MS/MS to allow comparison between the phosphoproteomes of control and POPX2 overexpressing cells. With this approach, we were able to identify a biochemical pathway through which POPX2 exerts its apparent cellular function: the regulation of activity of glycogen synthase kinase-3, which in turn modulates extracellular signal-regulated kinase and cell motility.
Publisher: MDPI AG
Date: 15-04-2020
DOI: 10.3390/IJMS21082755
Abstract: A decline in cognitive function following cancer treatment is one of the most commonly reported post-treatment symptoms among patients with cancer and those in remission, and include memory, processing speed, and executive function. A clear understanding of cognitive impairment as a result of cancer and its therapy can be obtained by delineating structural and functional changes using brain imaging studies and neurocognitive assessments. There is also a need to determine the underlying mechanisms and pathways that impact the brain and affect cognitive functioning in cancer survivors. Exosomes are small cell-derived vesicles formed by the inward budding of multivesicular bodies, and are released into the extracellular environment via an exocytic pathway. Growing evidence suggests that exosomes contribute to various physiological and pathological conditions, including neurological processes such as synaptic plasticity, neuronal stress response, cell-to-cell communication, and neurogenesis. In this review, we summarize the relationship between exosomes and cancer-related cognitive impairment. Unraveling exosomes’ actions and effects on the microenvironment of the brain, which impacts cognitive functioning, is critical for the development of exosome-based therapeutics for cancer-related cognitive impairment.
Publisher: American Chemical Society (ACS)
Date: 07-05-2012
DOI: 10.1021/PR300212G
Abstract: Gastric cancer remains highly fatal due to a dearth of diagnostic biomarkers for early stage disease and molecular targets for therapy. Plasma membrane proteins, including cluster of differentiation (CD) proteins and receptor tyrosine kinases (RTKs), are a rich reservoir of biomarkers. Recognizing that interrogating plasma membrane proteins in idually overlooks extensive interactions among them, we have systematically investigated the membrane proteomes and transcriptomes of six gastric cancer cell lines. Our data revealed aberrantly high expression of proteins whose functions accurately reflect the clinical phenotype of gastric cancer, and prioritized critical RTKs and CD proteins in gastric cancer. Expression of selected surface proteins was confirmed by flow cytometry and immunostaining of clinical gastric cancer tissues. Close to 90% of the gastric cancer tissues in a cohort showed up-regulation of at least one of four proteins, that is, MET, EPHA2, FGFR2, and CD104/ITGB4. All intestinal type gastric cancer tumors in this cohort overexpressed at least one of a panel of three proteins, MET, FGFR2, and EPHA2. This study reports the first quantitative global landscape of the surface proteome of gastric cancer cells and provides a shortlist of gastric cancer biomarkers.
Publisher: American Chemical Society (ACS)
Date: 28-12-2016
DOI: 10.1021/ACS.JPROTEOME.6B00748
Abstract: Cancer metastasis is a complex mechanism involving multiple processes. Previously, our integrative proteome, transcriptome, and phosphoproteome study reported that the levels of serine/threonine phosphatase POPX2 were positively correlated with cancer cell motility through modulating MAPK signaling. Surprisingly, here we found that POPX2 knockdown cells induced more numerous and larger tumor nodules in lungs in longer term animal studies. Interestingly, our analysis of DNA microarray data from cancer patient s les that are available in public databases shows that low POPX2 expression is linked to distant metastasis and poor survival rate. These observations suggest that lower levels of POPX2 may favor tumor progression in later stages of metastasis. We hypothesize that POPX2 may do so by modulation of angiogenesis. Secretome analysis of POPX2-knockdown MDA-MB-231 cells using LC-MS/MS-based SILAC quantitative proteomics and cytokine array show that silencing of POPX2 leads to increased secretion of exosomes, which may, in turn, induce multiple pro-angiogenic cytokines. This study, combined with our previous findings, suggests that a single ubiquitously expressed phosphatase POPX2 influences cancer metastasis via modulating multiple biological processes including MAPK signaling and exosome cytokine secretion.
Publisher: American Physiological Society
Date: 09-2012
DOI: 10.1152/AJPCELL.00402.2011
Abstract: Atrogin-1, a muscle-specific E3 ligase, targets MyoD for degradation through the ubiquitin-proteasome-mediated system. Myostatin, a member of the transforming growth factor-β superfamily, potently inhibits myogenesis by lowering MyoD levels. While atrogin-1 is upregulated by myostatin, it is currently unknown whether atrogin-1 plays a role in mediating myostatin signaling to regulate myogenesis. In this report, we have confirmed that atrogin-1 increasingly interacts with MyoD upon recombinant human myostatin (hMstn) treatment. The absence of atrogin-1, however, led to elevated MyoD levels and permitted the differentiation of atrogin-1 −/− primary myoblast cultures despite the presence of exogenous myostatin. Furthermore, inactivation of atrogin-1 rescued myoblasts from growth inhibition by hMstn. Therefore, these results highlight the central role of atrogin-1 in regulating myostatin signaling during myogenesis. Currently, there are only two known targets of atrogin-1. Thus, we next characterized the associated proteins of atrogin-1 in control and hMstn-treated C2C12 cell cultures by stably expressing tagged atrogin-1 in myoblasts and myotubes, and sequencing the coimmunoprecipitated proteome. We found that atrogin-1 putatively interacts with sarcomeric proteins, transcriptional factors, metabolic enzymes, components of translation, and spliceosome formation. In addition, we also identified that desmin and vimentin, two components of the intermediate filament in muscle, directly interacted with and were degraded by atrogin-1 in response to hMstn. In summary, the muscle wasting effects of the myostatin-atrogin-1 axis are not only limited to the degradation of MyoD and eukaryotic translation initiation factor 3 subunit f, but also encompass several proteins that are involved in a wide variety of cellular activities in the muscle.
Publisher: Wiley
Date: 27-07-2010
Abstract: Human monocytes' exposure to low-level lipopolysaccharide (LPS) induces temporary monocytic insensitivity to subsequent LPS challenge. The underlying mechanism of this phenomenon could have important clinical utilities in preventing and/or treating severe infections. In this study, we used an iTRAQ-based quantitative proteomic approach to comprehensively characterize the membrane proteomes of monocytes before and after LPS exposure. We identified a total of 1651 proteins, of which 53.6% were membrane proteins. Ninety-four percent of the proteins were quantified and 255 proteins were shown to be tightly regulated by LPS. Subcellular location analysis revealed organelle-specific response to LPS exposure: more than 90% of identified mitochondrial membrane proteins were significant downregulated, whereas the majority of proteins from other organelles such as ER, Golgi and ribosome were upregulated. Moreover, we found that the expression of most receptors potentially involved in LPS signal pathway (CD14, toll-like receptor 4, CD11/CD18 complex) were substantially decreased, while the expression of molecules involved in LPS neutralization were enhanced after LPS challenge. Together, these findings could be of significance in understanding the mechanism of LPS tolerance and provide values for designing new approaches for regulating monocytic responses in sepsis patients.
Publisher: Humana Press
Date: 2011
DOI: 10.1007/978-1-61779-319-6_22
Abstract: Although the snapshots of different in vitro conformational states have been intensively studied, current techniques such as nuclear magnetic resonance, X-ray crystallography, and electron microscope method cannot probe the in vivo conformational movements of integral membrane proteins on cell surfaces. Here, we describe a hydroxyl radical protein footprinting coupled to a mass spectrometry detection technique to probe the structural dynamics of a membrane protein directly on the native cell surface. This method uses in situ generation of hydroxyl radicals to oxidize and covalently modify integral membrane proteins on the cell surface. To explain this technique in detail, we use the porin OmpF as an ex le, although the method may be applied to study any membrane protein. Footprinting results show that the surface mapping data of OmpF are consistent with its current crystallographic structure. In addition, this technique also enables the detection of in vivo voltage gating of porin OmpF for the first time. This novel cell surface footprinting method coupled with MS analysis can be a potentially efficient method to study the structural dynamics of the membrane proteins of a living cell.
Publisher: Springer Science and Business Media LLC
Date: 09-03-2015
DOI: 10.1038/NI.3125
Abstract: A cytosolic role for the histone methyltransferase Ezh2 in regulating lymphocyte activation has been suggested, but the molecular mechanisms underpinning this extranuclear function have remained unclear. Here we found that Ezh2 regulated the integrin signaling and adhesion dynamics of neutrophils and dendritic cells (DCs). Ezh2 deficiency impaired the integrin-dependent transendothelial migration of innate leukocytes and restricted disease progression in an animal model of multiple sclerosis. Direct methylation of talin, a key regulatory molecule in cell migration, by Ezh2 disrupted the binding of talin to F-actin and thereby promoted the turnover of adhesion structures. This regulatory effect was abolished by targeted disruption of the interactions of Ezh2 with the cytoskeletal-reorganization effector Vav1. Our studies reveal an unforeseen extranuclear function for Ezh2 in regulating adhesion dynamics, with implications for leukocyte migration, immune responses and potentially pathogenic processes.
Publisher: American Chemical Society (ACS)
Date: 08-05-2017
DOI: 10.1021/ACS.JPROTEOME.7B00154
Abstract: Mass spectrometry-based protein footprinting emerged as a useful technology to understand protein ligand interactions in vitro. We have previously demonstrated the application of footprinting in live E. coli cells. Here, we further optimized an ultrafast laser photolysis hydroxyl radical footprinting method and applied it to study the interaction of EGF and EGFR in live mammalian cells. This method used a nanosecond laser to photochemically generate a burst of hydroxyl radicals in situ in-cell suspension to oxidize the amino acids on the protein surface. Mass spectrometric analysis of the thus modified peptides was interpreted to probe the solvent-accessible surface areas of the protein in its native biological state with and without EGF activation. Our footprinting data agreed with the two relevant EGFR crystal structures, indicating that this in-cell laser photolysis footprinting technique is a valid approach to study the structural properties of integral membrane proteins directly in the native environment.
Publisher: American Chemical Society (ACS)
Date: 12-01-2009
DOI: 10.1021/AC802175R
Abstract: We describe here a rapid method to determine the cyclic structure and disulfide linkages of highly stable cyclotides via a combination of flash partial acid hydrolysis, LC-MS/MS, and computational tools. Briefly, a mixture of closely related cyclotides, kalata B1 and varv A purified from Viola yedoensis was partially hydrolyzed in 2 M HCl for 5 min by microwave-assisted hydrolysis or for 30 min in an autoclave oven (121 degrees C and 15 psi). The partially hydrolyzed peptide mixture was then subjected to LC-MS/MS analysis, with the disulfide linked-peptides fragmented by collision activated dissociation (CAD). A computer program written in-house (available for download at proteomics.sbs.ntu.edu.sg/cyclotide_SS ) was used for interpreting LC-MS/MS spectra and assigning the disulfide bonds. Time-point analysis of single-disulfide fragments revealed that nonrandom acid catalyzed fragmentation mostly occurred at the turns which are solvent-exposed and often contain side chain functionalized amino acids such as Asx/Glx and Ser/Thr. In particular, the most susceptible bond for acid hydrolysis in kalata B1 and varv A was found to be the highly conserved N25-G26 which is also the head-to-tail ligation site of the linear precursor proteins, indicating that formation of the three disulfide bonds might precede cyclic structure closure by N25-G26 ligation. This observation is consistent with the recent report that the N25-G26 bond formation is the last step in the cyclotide biosynthetic pathway. The process demonstrated here can potentially be a high throughput method that is generally applicable to determine disulfide bonds of other relatively low-abundance cyclotides.
Publisher: American Chemical Society (ACS)
Date: 26-04-2013
DOI: 10.1021/PR301113C
Abstract: POPX2 is a serine/threonine phosphatase belonging to the protein phosphatase 2C (PP2C) family that has been found to be elevated in invasive breast cancer cells. Silencing of POPX2 results in lower cell motility and invasiveness. The molecular mechanism of POPX2-regulated cell motility is not well understood. To identify the relevant signaling pathways, we investigated the transcriptome and proteome of POPX2-knockdown MDA-MB-231 breast cancer cells. Our data suggest that POPX2 might be involved in the regulation of focal adhesions and cytoskeleton dynamics through the regulation of MAP kinase (MAPK1/3) and glycogen synthase kinase 3 (GSK3α/β) activities. Silencing POPX2 alters phosphorylation levels of MAPK1/3 and GSK3α/β and results in reduced activity of these kinases. Both MAPK and GSK3 are known to regulate the activities of transcription factors. MAPK1/3 are also implicated in the phosphorylation of stathmin. The level of phospho-stathmin was found to be lower in POPX2 knockdown cells. As phosphorylation of stathmin inhibits its microtubule severing activity, we observed less stable microtubules in POPX2 knockdown cells. Taken together, our data suggest that POPX2 might regulate cell motility through its regulation of the MAPK1/3, leading to changes in the cytoskeleton and cell motility.
Publisher: Frontiers Media SA
Date: 21-06-2017
Publisher: Frontiers Media SA
Date: 03-11-2016
Publisher: Springer Science and Business Media LLC
Date: 17-03-2016
Publisher: Springer Science and Business Media LLC
Date: 11-07-2018
Publisher: American Chemical Society (ACS)
Date: 10-06-2010
DOI: 10.1021/PR100037H
Abstract: In shotgun proteomics, multidimensional liquid chromatography (MDLC) is commonly used to reduce s le complexity and increase dynamic range of protein identification. Since reversed-phase chromatography is mostly used as the second-dimensional separation before mass spectrometric analysis, the improvement of MDLC primarily depends on the first dimension of separation. Here, we present a novel whole proteome analysis method that separates peptides based on ERLIC. Tryptic peptides were retained on a weak anion exchange column through ERLIC with a high organic mobile phase. They were then distributed into multiple fractions based on both pI and polarity through the simultaneous effect of electrostatic repulsion and hydrophilic interaction when eluted using a salt-free pH gradient of increasing water content. Applying this to rat kidney tissue, we identified 4821 proteins and 30 659 unique peptides with high confidence from two replicates using LTQ-FT. This was 36.2% and 64.3% higher, respectively, than was obtained with the widely used SCX separation mode. Notably, the identification of both highly hydrophobic and basic peptides increased over 120% using the ERLIC method. The results indicate that ERLIC is a promising alternative to SCX as the first dimension of MDLC. In total, 5499 proteins and 35 847 unique peptides of rat kidney tissue are characterized.
Publisher: eLife Sciences Publications, Ltd
Date: 27-08-2015
DOI: 10.7554/ELIFE.07759
Abstract: Hutchinson-Gilford progeria (HGPS) is a premature ageing syndrome caused by a mutation in LMNA, resulting in a truncated form of lamin A called progerin. Progerin triggers loss of the heterochromatic marker H3K27me3, and premature senescence, which is prevented by telomerase. However, the mechanism how progerin causes disease remains unclear. Here, we describe an inducible cellular system to model HGPS and find that LAP2α (lamina-associated polypeptide-α) interacts with lamin A, while its interaction with progerin is significantly reduced. Super-resolution microscopy revealed that over 50% of telomeres localize to the lamina and that LAP2α association with telomeres is impaired in HGPS. This impaired interaction is central to HGPS since increasing LAP2α levels rescues progerin-induced proliferation defects and loss of H3K27me3, whereas lowering LAP2 levels exacerbates progerin-induced defects. These findings provide novel insights into the pathophysiology underlying HGPS, and how the nuclear lamina regulates proliferation and chromatin organization.
Publisher: Wiley
Date: 02-11-2017
DOI: 10.1111/BJH.14976
Abstract: Erythropoiesis is marked by progressive changes in morphological, biochemical and mechanical properties of erythroid precursors to generate red blood cells (RBC). The earliest enucleated forms derived in this process, known as reticulocytes, are multi-lobular and spherical. As reticulocytes mature, they undergo a series of dynamic cytoskeletal re-arrangements and the expulsion of residual organelles, resulting in highly deformable biconcave RBCs (normocytes). To understand the significant, yet neglected proteome-wide changes associated with reticulocyte maturation, we undertook a quantitative proteomics approach. Immature reticulocytes (marked by the presence of surface transferrin receptor, CD71) and mature RBCs (devoid of CD71) were isolated from human cord blood using a magnetic separation procedure. After sub-fractionation into triton-extracted membrane proteins and luminal s les (isobaric tags for relative and absolute quantitation), quantitative mass spectrometry was conducted to identify more than 1800 proteins with good confidence and coverage. While most structural proteins (such as Spectrins, Ankyrin and Band 3) as well as surface glycoproteins were conserved, proteins associated with microtubule structures, such as Talin-1/2 and ß-Tubulin, were detected only in immature reticulocytes. Atomic force microscopy (AFM)-based imaging revealed an extended network of spectrin filaments in reticulocytes (with an average length of 48 nm), which shortened during reticulocyte maturation (average spectrin length of 41 nm in normocytes). The extended nature of cytoskeletal network may partly account for increased deformability and shape changes, as reticulocytes transform to normocytes.
Publisher: Springer Science and Business Media LLC
Date: 06-10-2017
DOI: 10.1038/CDD.2017.152
Publisher: Elsevier BV
Date: 03-2019
Publisher: American Association for Cancer Research (AACR)
Date: 29-05-2014
DOI: 10.1158/0008-5472.CAN-13-2321
Abstract: PRL-3, an oncogenic dual-specificity phosphatase, is overexpressed in 50% of acute myelogenous leukemia (AML) and associated with poor survival. We found that stable expression of PRL-3 confers cytokine independence and growth advantage of AML cells. However, how PRL-3 mediates these functions in AML is not known. To comprehensively screen for PRL3-regulated proteins in AML, we performed SILAC-based quantitative proteomics analysis and discovered 398 significantly perturbed proteins after PRL-3 overexpression. We show that Leo1, a component of RNA polymerase II–associated factor (PAF) complex, is a novel and important mediator of PRL-3 oncogenic activities in AML. We described a novel mechanism where elevated PRL-3 protein increases JMJD2C histone demethylase occupancy on Leo1 promoter, thereby reducing the H3K9me3 repressive signals and promoting Leo1 gene expression. Furthermore, PRL-3 and Leo1 levels were positively associated in AML patient s les (N = 24 P & 0.01). On the other hand, inhibition of Leo1 reverses PRL-3 oncogenic phenotypes in AML. Loss of Leo1 leads to destabilization of the PAF complex and downregulation of SOX2 and SOX4, potent oncogenes in myeloid transformation. In conclusion, we identify an important and novel mechanism by which PRL-3 mediates its oncogenic function in AML. Cancer Res 74(11) 3043–53. ©2014 AACR.
Publisher: Elsevier BV
Date: 12-2019
Publisher: Springer Science and Business Media LLC
Date: 16-10-2010
DOI: 10.1007/S00018-010-0545-X
Abstract: We integrated LC-MS/MS-based and protein antibody array-based proteomics with genomics approaches to investigate the phosphoproteome and transcriptome of gastric cancer cell lines and endoscopic gastric biopsies from normal subjects and patients with benign gastritis or gastric cancer. More than 3,000 non-redundant phosphorylation sites in over 1,200 proteins were identified in gastric cancer cells. We correlated phosphoproteome data with transcriptome data sets and reported the expression of 41 protein kinases, 5 phosphatases and 65 phosphorylated mitochondrial proteins in gastric cancer cells. Transcriptional expression levels of 190 phosphorylated proteins were >2-fold higher in gastric cancer cells compared to normal stomach tissue. Pathway analysis demonstrated over-presentation of DNA damage response pathway and underscored critical roles of phosphorylated p53 in gastric cancer. This is the first study to comprehensively report the gastric cancer phosphoproteome. Integrative analysis of the phosphoproteome and transcriptome provided an expansive view of molecular signaling pathways in gastric cancer.
Publisher: American Chemical Society (ACS)
Date: 02-10-2008
DOI: 10.1021/PR800473J
Publisher: Cold Spring Harbor Laboratory
Date: 14-04-2023
DOI: 10.1101/2023.04.12.536670
Abstract: Hypoxia-induced vascular endothelial dysfunction (VED) is a significant contributor to several severe human conditions, including heart disease, stroke, dementia, and cancer. However, current treatment options for VED are limited due to a lack of understanding of the underlying disease mechanisms and therapeutic leads. We recently discovered a heat-stable microprotein in ginseng, known as ginsentide TP1 that has been shown to reduce vascular dysfunction in cardiovascular disease models. In this study, we use a combination of functional assays and quantitative pulsed SILAC proteomics to determine new proteins synthesized in hypoxia and to show that ginsentide TP1 provides protection for human endothelial cells against hypoxia and ER stress. We found that hypoxia activates various pathways related to endothelium activation and monocyte adhesion, which in turn, impairs nitric oxide (NO) synthase activity, reduces NO bioavailability, and increases the production of reactive oxygen species that contribute to VED. Additionally, hypoxia triggers endoplasmic reticulum stress and initiates apoptotic signaling pathways associated with cardiovascular pathology. Treatment with ginsentide TP1 reduced surface adhesion molecule expression prevented activation of the endothelium and leukocyte adhesion, restored protein hemostasis, and reduced ER stress to protect against hypoxia-induced cell death. Ginsentide TP1 also restored NO signaling and bioavailability, reduced oxidative stress, and protected endothelial cells from endothelium dysfunction. In conclusion, this study shows that the molecular pathogenesis of VED induced by hypoxia can be mitigated by treatment with ginsentide TP1, which could be one of the key bioactive compounds responsible for the “cure-all” effect of ginseng. This research may lead to the development of new therapies for cardiovascular disorders.
Publisher: Cold Spring Harbor Laboratory
Date: 06-04-2023
DOI: 10.1101/2023.04.05.535784
Abstract: Ginseng has been known as a “cure-all” traditional medicine to treat various illnesses and as an adaptogen to relieve stress. However, the known active compounds of ginseng are small-molecule metabolites. Here we report ginsentides, which are disulfide-dense, super-stable and cell-penetrating peptides with 31–33 amino acids, as active compounds and adaptogens that restore homeostasis in response to stress. Using mass spectrometry-based target identification and functional studies, we show that ginsentides promote vasorelaxation by producing nitric oxide through endothelial cells via the PI3K/Akt signaling pathway. Ginsentides were also found to alleviate α1-adrenergic receptor overactivity by reversing phenylephrine-induced constriction of the aorta, decrease monocyte adhesion to endothelial cells via CD166/ESAM/CD40, inhibit P2Y12 receptors, reduce platelet aggregation, and thrombus formation in the lung. Orally administered ginsentides were effective in anti-stress behavior using animal models of tail suspension and forced swimming tests. Together, these results suggest that ginsentides interact with multiple systems to restore homeostasis by reversing stress-induced physiological changes and provide new insights into the panacea medicinal effects of ginseng.
Publisher: Springer Science and Business Media LLC
Date: 30-09-2015
DOI: 10.1038/SREP14664
Abstract: Extracellular vesicles (EVs) such as exosomes and microvesicles mediate intercellular communication and regulate a erse range of crucial biological processes. Host cells that are damaged, infected or transformed release biomarker-containing EVs into the peripheral circulation, where they can be readily accessed for use in diagnostic or prognostic testing. However, current methods of EV isolation from blood plasma are complex and often require relatively large s le volumes, hence are inefficient for widespread use in clinical settings. Here, we report a novel and inexpensive method of rapidly isolating EVs from small volumes of human blood plasma by PRotein Organic Solvent PRecipitation (PROSPR). PROSPR encompasses a rapid three-step protocol to remove soluble proteins from plasma via precipitation in cold acetone, leaving the lipid-encapsulated EVs behind in suspension. This generates higher purity EVs that can then be obtained from filtration or classical ultracentrifugation methods. We foresee that PROSPR-based purification of EVs will significantly accelerate the discovery of new disease biomarkers and the characterization of EVs with potential for clinical applications.
Publisher: Elsevier BV
Date: 04-2010
Publisher: Springer Science and Business Media LLC
Date: 11-08-2017
Publisher: Elsevier BV
Date: 03-2014
Publisher: American Chemical Society (ACS)
Date: 02-09-2014
DOI: 10.1021/PR500754J
Abstract: Dementia is a major public health burden characterized by impaired cognition and loss of function. There are limited treatment options due to inadequate understanding of its pathophysiology and underlying causative mechanisms. Discovery-driven iTRAQ-based quantitative proteomics techniques were applied on frozen brain s les to profile the proteome from vascular dementia (VaD) and age-matched nondementia controls to elucidate the perturbed pathways contributing to pathophysiology of VaD. The iTRAQ quantitative data revealed significant up-regulation of protein-l-isoaspartate O-methyltransferase and sodium-potassium transporting ATPase, while post-translational modification analysis suggested deamidation of catalytic and regulatory subunits of sodium-potassium transporting ATPase. Spontaneous protein deamidation of labile asparagines, generating abnormal l-isoaspartyl residues, is associated with cell aging and dementia due to Alzheimer's disease and may be a cause of neurodegeneration. As ion channel proteins play important roles in cellular signaling processes, alterations in their function by deamidation may lead to perturbations in membrane excitability and neuronal function. Structural modeling of sodium-potassium transporting ATPase revealed the close proximity of these deamidated residues to the catalytic site during E2P confirmation. The deamidated residues may disrupt electrostatic interaction during E1 phosphorylation, which may affect ion transport and signal transduction. Our findings suggest impaired regulation and compromised activity of ion channel proteins contribute to the pathophysiology of VaD.
Publisher: Public Library of Science (PLoS)
Date: 23-02-2011
Publisher: Elsevier BV
Date: 12-2010
Publisher: Public Library of Science (PLoS)
Date: 11-03-2021
DOI: 10.1371/JOURNAL.PBIO.3001081
Abstract: The apical complex is the instrument of invasion used by apicomplexan parasites, and the conoid is a conspicuous feature of this apparatus found throughout this phylum. The conoid, however, is believed to be heavily reduced or missing from Plasmodium species and other members of the class Aconoidasida. Relatively few conoid proteins have previously been identified, making it difficult to address how conserved this feature is throughout the phylum, and whether it is genuinely missing from some major groups. Moreover, parasites such as Plasmodium species cycle through 3 invasive forms, and there is the possibility of differential presence of the conoid between these stages. We have applied spatial proteomics and high-resolution microscopy to develop a more complete molecular inventory and understanding of the organisation of conoid-associated proteins in the model apicomplexan Toxoplasma gondii . These data revealed molecular conservation of all conoid substructures throughout Apicomplexa, including Plasmodium , and even in allied Myzozoa such as Chromera and dinoflagellates. We reporter-tagged and observed the expression and location of several conoid complex proteins in the malaria model P . berghei and revealed equivalent structures in all of its zoite forms, as well as evidence of molecular differentiation between blood-stage merozoites and the ookinetes and sporozoites of the mosquito vector. Collectively, we show that the conoid is a conserved apicomplexan element at the heart of the invasion mechanisms of these highly successful and often devastating parasites.
Publisher: Elsevier BV
Date: 08-2009
Publisher: American Chemical Society (ACS)
Date: 06-11-2008
DOI: 10.1021/AC801344Z
Publisher: American Chemical Society (ACS)
Date: 07-10-2008
DOI: 10.1021/PR800403Z
No related grants have been discovered for Siu Kwan Sze.