ORCID Profile
0000-0002-0199-3222
Current Organisations
University of Melbourne
,
La Trobe University
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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)
Biochemistry and Cell Biology | Proteomics and Intermolecular Interactions (excl. Medical Proteomics) | Protein Trafficking | Biochemistry And Cell Biology Not Elsewhere Classified | Protein Targeting And Signal Transduction | Membrane Biology | Receptors and Membrane Biology | Biochemistry and Cell Biology not elsewhere classified | Structural Biology (incl. Macromolecular Modelling) | Analytical Biochemistry | Systems Biology | Bacteriology
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Biological Sciences | Expanding Knowledge in the Agricultural and Veterinary Sciences | Expanding Knowledge in the Chemical Sciences | Biological sciences | Expanding Knowledge in the Medical and Health Sciences |
Related Links
Publications
Dissection of the mitochondrial import and assembly pathway for human Tom40
Publisher: Elsevier BV
Date: 03-2005
Sideroflexin 4 is a complex I assembly factor that interacts with the MCIA complex and is required for the assembly of the ND2 module
Publisher: Proceedings of the National Academy of Sciences
Date: 25-03-2022
Abstract: Mitochondria are double-membraned eukaryotic organelles that house the proteins required for generation of ATP, the energy currency of cells. ATP generation within mitochondria is performed by five multisubunit complexes (complexes I to V), the assembly of which is an intricate process. Mutations in subunits of these complexes, or the suite of proteins that help them assemble, lead to a severe multisystem condition called mitochondrial disease. We show that SFXN4, a protein that causes mitochondrial disease when mutated, assists with the assembly of complex I. This finding explains why mutations in SFXN4 cause mitochondrial disease and is surprising because SFXN4 belongs to a family of amino acid transporter proteins, suggesting that it has undergone a dramatic shift in function through evolution.
Super-resolution microscopy reveals the arrangement of inner membrane protein complexes in mammalian mitochondria
Publisher: The Company of Biologists
Date: 07-2021
DOI: 10.1242/JCS.252197
Abstract: The mitochondrial inner membrane is a protein-rich environment containing large multimeric complexes, including complexes of the mitochondrial electron transport chain, mitochondrial translocases and quality control machineries. Although the inner membrane is highly proteinaceous, with 40-60% of all mitochondrial proteins localised to this compartment, little is known about the spatial distribution and organisation of complexes in this environment. We set out to survey the arrangement of inner membrane complexes using stochastic optical reconstruction microscopy (STORM). We reveal that subunits of the TIM23 complex, TIM23 and TIM44 (also known as TIMM23 and TIMM44, respectively), and the complex IV subunit COXIV, form organised clusters and show properties distinct from the outer membrane protein TOM20 (also known as TOMM20). Density based cluster analysis indicated a bimodal distribution of TIM44 that is distinct from TIM23, suggesting distinct TIM23 subcomplexes. COXIV is arranged in larger clusters that are disrupted upon disruption of complex IV assembly. Thus, STORM super-resolution microscopy is a powerful tool for examining the nanoscale distribution of mitochondrial inner membrane complexes, providing a ‘visual’ approach for obtaining pivotal information on how mitochondrial complexes exist in a cellular context.
Impaired folding of the mitochondrial small TIM chaperones induces clearance by the i-AAA protease
Publisher: Elsevier BV
Date: 12-2012
DOI: 10.1016/J.JMB.2012.09.019
Abstract: The intermembrane space of mitochondria contains a dedicated chaperone network-the small translocase of the inner membrane (TIM) family-for the sorting of hydrophobic precursors. All small TIMs are defined by the presence of a twin CX(3)C motif and the monomeric proteins are stabilized by two intramolecular disulfide bonds formed between the cysteines of these motifs. The conserved cysteine residues within small TIM members have also been shown to participate in early biogenesis events, with the most N-terminal cysteine residue important for import and retention within the intermembrane space via the receptor and disulfide oxidase, Mia40. In this study, we have analyzed the in vivo consequences of improper folding of small TIM chaperones by generating site-specific cysteine mutants and assessed the fate of the incompletely oxidized proteins within mitochondria. We show that no in idual cysteine residue is required for the function of Tim9 or Tim10 in yeast and that defective assembly of the small TIMs induces their proteolytic clearance from mitochondria. We delineate a clearance mechanism for the mutant proteins and their unassembled wild-type partner protein by the mitochondrial ATP-dependent protease, Yme1 (yeast mitochondrial escape 1).
Mitochondrial morphology and distribution in mammalian cells
Publisher: Walter de Gruyter GmbH
Date: 12-2006
DOI: 10.1515/BC.2006.193
Abstract: It is now appreciated that mitochondria form tubular networks that adapt to the requirements of the cell by undergoing changes in their shape through fission and fusion. Proper mitochondrial distribution also appears to be required for ATP delivery and calcium regulation, and, in some cases, for cell development. While we now realise the great importance of mitochondria for the cell, we are only beginning to work out how these organelles undergo the drastic morphological changes that are essential for cellular function. Of the few known components involved in shaping mitochondria, some have been found to be essential to life and their gene mutations are linked to neurological disorders, while others appear to be recruited in the activation of cell death pathways. Here we review our current understanding of the functions of the main players involved in mitochondrial fission, fusion and distribution in mammalian cells.
Loss of mitochondrial fatty acid β-oxidation protein short-chain Enoyl-CoA hydratase disrupts oxidative phosphorylation protein complex stability and function
Publisher: Wiley
Date: 24-08-2023
DOI: 10.1111/FEBS.16595
Abstract: Short‐chain enoyl‐CoA hydratase 1 (ECHS1) is involved in the second step of mitochondrial fatty acid β‐oxidation (FAO), catalysing the hydration of short‐chain enoyl‐CoA esters to short‐chain 3‐hyroxyl‐CoA esters. Genetic deficiency in ECHS1 (ECHS1D) is associated with a specific subset of Leigh Syndrome, a disease typically caused by defects in oxidative phosphorylation (OXPHOS). Here, we examined the molecular pathogenesis of ECHS1D using a CRISPR/Cas9 edited human cell ‘knockout’ model and fibroblasts from ECHS1D patients. Transcriptome analysis of ECHS1 ‘knockout’ cells showed reductions in key mitochondrial pathways, including the tricarboxylic acid cycle, receptor‐mediated mitophagy and nucleotide biosynthesis. Subsequent proteomic analyses confirmed these reductions and revealed additional defects in mitochondrial oxidoreductase activity and fatty acid β‐oxidation. Functional analysis of ECHS1 ‘knockout’ cells showed reduced mitochondrial oxygen consumption rates when metabolising glucose or OXPHOS complex I‐linked substrates, as well as decreased complex I and complex IV enzyme activities. ECHS1 ‘knockout’ cells also exhibited decreased OXPHOS protein complex steady‐state levels (complex I, complex III 2 , complex IV, complex V and supercomplexes CIII 2 /CIV and CI/CIII 2 /CIV), which were associated with a defect in complex I assembly. Patient fibroblasts exhibit varied reduction of mature OXPHOS complex steady‐state levels, with defects detected in CIII 2 , CIV, CV and the CI/CIII 2 /CIV supercomplex. Overall, these findings highlight the contribution of defective OXPHOS function, in particular complex I deficiency, to the molecular pathogenesis of ECHS1D.
Stimulating Mitochondrial Biogenesis with Deoxyribonucleosides Increases Functional Capacity in ECHS1-Deficient Cells
Publisher: MDPI AG
Date: 20-10-2022
Abstract: The lack of effective treatments for mitochondrial disease has seen the development of new approaches, including those that stimulate mitochondrial biogenesis to boost ATP production. Here, we examined the effects of deoxyribonucleosides (dNs) on mitochondrial biogenesis and function in Short chain enoyl-CoA hydratase 1 (ECHS1) ‘knockout’ (KO) cells, which exhibit combined defects in both oxidative phosphorylation (OXPHOS) and mitochondrial fatty acid β-oxidation (FAO). DNs treatment increased mitochondrial DNA (mtDNA) copy number and the expression of mtDNA-encoded transcripts in both CONTROL (CON) and ECHS1 KO cells. DNs treatment also altered global nuclear gene expression, with key gene sets including ‘respiratory electron transport’ and ‘formation of ATP by chemiosmotic coupling’ increased in both CON and ECHS1 KO cells. Genes involved in OXPHOS complex I biogenesis were also upregulated in both CON and ECHS1 KO cells following dNs treatment, with a corresponding increase in the steady-state levels of holocomplex I in ECHS1 KO cells. Steady-state levels of OXPHOS complex V, and the CIII2/CIV and CI/CIII2/CIV supercomplexes, were also increased by dNs treatment in ECHS1 KO cells. Importantly, treatment with dNs increased both basal and maximal mitochondrial oxygen consumption in ECHS1 KO cells when metabolizing either glucose or the fatty acid palmitoyl-L-carnitine. These findings highlight the ability of dNs to improve overall mitochondrial respiratory function, via the stimulation mitochondrial biogenesis, in the face of combined defects in OXPHOS and FAO due to ECHS1 deficiency.
Coxiella co-opts the Glutathione Peroxidase 4 to protect the host cell from oxidative stress–induced cell death
Publisher: Proceedings of the National Academy of Sciences
Date: 28-08-2023
Abstract: The causative agent of human Q fever, Coxiella burnetii, is highly adapted to infect alveolar macrophages by inhibiting a range of host responses to infection. Despite the clinical and biological importance of this pathogen, the challenges related to genetic manipulation of both C. burnetii and macrophages have limited our knowledge of the mechanisms by which C. burnetii subverts macrophages functions. Here, we used the related bacterium Legionella pneumophila to perform a comprehensive screen of C. burnetii effectors that interfere with innate immune responses and host death using the greater wax moth Galleria mellonella and mouse bone marrow–derived macrophages. We identified MceF (Mitochondrial Coxiella effector protein F), a C. burnetii effector protein that localizes to mitochondria and contributes to host cell survival. MceF was shown to enhance mitochondrial function, delay membrane damage, and decrease mitochondrial ROS production induced by rotenone. Mechanistically, MceF recruits the host antioxidant protein Glutathione Peroxidase 4 (GPX4) to the mitochondria. The protective functions of MceF were absent in primary macrophages lacking GPX4, while overexpression of MceF in human cells protected against oxidative stress–induced cell death. C. burnetii lacking MceF was replication competent in mammalian cells but induced higher mortality in G. mellonella, indicating that MceF modulates the host response to infection. This study reveals an important C. burnetii strategy to subvert macrophage cell death and host immunity and demonstrates that modulation of the host antioxidant system is a viable strategy to promote the success of intracellular bacteria.
Stress-induced OMA1 activation and autocatalytic turnover regulate OPA1-dependent mitochondrial dynamics
Publisher: Wiley
Date: 18-02-2014
Dissecting Membrane Insertion of Mitochondrial β-Barrel Proteins
Publisher: Elsevier BV
Date: 03-2008
DOI: 10.1016/J.CELL.2008.01.028
Abstract: Communication of mitochondria with the rest of the cell requires beta-barrel proteins of the outer membrane. All beta-barrel proteins are synthesized as precursors in the cytosol and imported into mitochondria by the general translocase TOM and the sorting machinery SAM. The SAM complex contains two proteins essential for cell viability, the channel-forming Sam50 and Sam35. We have identified the sorting signal of mitochondrial beta-barrel proteins that is universal in all eukaryotic kingdoms. The beta-signal initiates precursor insertion into a hydrophilic, proteinaceous membrane environment by forming a ternary complex with Sam35 and Sam50. Sam35 recognizes the beta-signal, inducing a major conductance increase of the Sam50 channel. Subsequent precursor release from SAM is coupled to integration into the lipid phase. We propose that a two-stage mechanism of signal-driven insertion into a membrane protein complex and subsequent integration into the lipid phase may represent a general mechanism for biogenesis of beta-barrel proteins.
The MIA pathway: A tight bond between protein transport and oxidative folding in mitochondria
Publisher: Elsevier BV
Date: 07-2012
DOI: 10.1016/J.BBAMCR.2012.04.014
Abstract: Many newly synthesized proteins obtain disulfide bonds in the bacterial periplasm, the endoplasmic reticulum (ER) and the mitochondrial intermembrane space. The acquisition of disulfide bonds is critical for the folding, assembly and activity of these proteins. Spontaneous oxidation of thiol groups is inefficient in vivo, therefore cells have developed machineries that catalyse the oxidation of substrate proteins. The identification of the machinery that mediates this process in the intermembrane space of mitochondria, known as MIA (mitochondrial intermembrane space assembly), provided a unique mechanism of protein transport. The MIA machinery introduces disulfide bonds into incoming intermembrane space precursors and thus tightly couples the process of precursor translocation to precursor oxidation. We discuss our current understanding of the MIA pathway and the mechanisms that oversee thiol-exchange reactions in mitochondria.
Correction: Function of hTim8a in complex IV assembly in neuronal cells provides insight into pathomechanism underlying Mohr-Tranebjærg syndrome
Publisher: eLife Sciences Publications, Ltd
Date: 18-03-2020
DOI: 10.7554/ELIFE.56968
Mitochondrial protein import dysfunction: mitochondrial disease, neurodegenerative disease and cancer
Publisher: Wiley
Date: 28-01-2021
Mitochondrial protein import: precursor oxidation in a ternary complex with disulfide carrier and sulfhydryl oxidase
Publisher: Rockefeller University Press
Date: 13-10-2008
Abstract: The biogenesis of mitochondrial intermembrane space proteins depends on specific machinery that transfers disulfide bonds to precursor proteins. The machinery shares features with protein relays for disulfide bond formation in the bacterial periplasm and endoplasmic reticulum. A disulfide-generating enzyme/sulfhydryl oxidase oxidizes a disulfide carrier protein, which in turn transfers a disulfide to the substrate protein. Current views suggest that the disulfide carrier alternates between binding to the oxidase and the substrate. We have analyzed the cooperation of the disulfide relay components during import of precursors into mitochondria and identified a ternary complex of all three components. The ternary complex represents a transient and intermediate step in the oxidation of intermembrane space precursors, where the oxidase Erv1 promotes disulfide transfer to the precursor while both oxidase and precursor are associated with the disulfide carrier Mia40.
Targeting mitochondria: how intravacuolar bacterial pathogens manipulate mitochondria
Publisher: Springer Science and Business Media LLC
Date: 12-08-2017
DOI: 10.1007/S00441-016-2475-X
Abstract: Manipulation of host cell function by bacterial pathogens is paramount for successful invasion and creation of a niche conducive to bacterial replication. Mitochondria play a role in many important cellular processes including energy production, cellular calcium homeostasis, lipid metabolism, haeme biosynthesis, immune signalling and apoptosis. The sophisticated integration of host cell processes by the mitochondrion have seen it emerge as a key target during bacterial infection of human host cells. This review highlights the targeting and interaction of this dynamic organelle by intravacuolar bacterial pathogens and the way that the modulation of mitochondrial function might contribute to pathogenesis.
Function of hTim8a in complex IV assembly in neuronal cells provides insight into pathomechanism underlying Mohr-Tranebjærg syndrome
Publisher: eLife Sciences Publications, Ltd
Date: 04-11-2019
DOI: 10.7554/ELIFE.48828
Abstract: Human Tim8a and Tim8b are members of an intermembrane space chaperone network, known as the small TIM family. Mutations in TIMM8A cause a neurodegenerative disease, Mohr-Tranebjærg syndrome (MTS), which is characterised by sensorineural hearing loss, dystonia and blindness. Nothing is known about the function of hTim8a in neuronal cells or how mutation of this protein leads to a neurodegenerative disease. We show that hTim8a is required for the assembly of Complex IV in neurons, which is mediated through a transient interaction with Complex IV assembly factors, in particular the copper chaperone COX17. Complex IV assembly defects resulting from loss of hTim8a leads to oxidative stress and changes to key apoptotic regulators, including cytochrome c, which primes cells for death. Alleviation of oxidative stress with Vitamin E treatment rescues cells from apoptotic vulnerability. We hypothesise that enhanced sensitivity of neuronal cells to apoptosis is the underlying mechanism of MTS.
Mitochondrial protein quality control in health and disease
Publisher: Wiley
Date: 28-03-2014
DOI: 10.1111/BPH.12430
Import of Proteins into Mitochondria
Publisher: Elsevier
Date: 2007
Regulation of mitochondrial protein import by cytosolic kinases
Publisher: Elsevier BV
Date: 2011
DOI: 10.1016/J.CELL.2010.12.015
Abstract: Mitochondria import a large number of nuclear-encoded proteins via membrane-bound transport machineries however, little is known about regulation of the preprotein translocases. We report that the main protein entry gate of mitochondria, the translocase of the outer membrane (TOM complex), is phosphorylated by cytosolic kinases-in particular, casein kinase 2 (CK2) and protein kinase A (PKA). CK2 promotes biogenesis of the TOM complex by phosphorylation of two key components, the receptor Tom22 and the import protein Mim1, which in turn are required for import of further Tom proteins. Inactivation of CK2 decreases the levels of the TOM complex and thus mitochondrial protein import. PKA phosphorylates Tom70 under nonrespiring conditions, thereby inhibiting its receptor activity and the import of mitochondrial metabolite carriers. We conclude that cytosolic kinases exert stimulatory and inhibitory effects on biogenesis and function of the TOM complex and thus regulate protein import into mitochondria.
Premature Ovarian Insufficiency in CLPB Deficiency: Transcriptomic, Proteomic and Phenotypic Insights
Publisher: The Endocrine Society
Date: 09-09-2022
Abstract: Premature ovarian insufficiency (POI) is a common form of female infertility that usually presents as an isolated condition but can be part of various genetic syndromes. Early diagnosis and treatment of POI can minimize comorbidity and improve health outcomes. We aimed to determine the genetic cause of syndromic POI, intellectual disability, neutropenia, and cataracts. We performed whole-exome sequencing (WES) followed by functional validation via RT-PCR, RNAseq, and quantitative proteomics, as well as clinical update of previously reported patients with variants in the caseinolytic peptidase B (CLPB) gene. We identified causative variants in CLPB, encoding a mitochondrial disaggregase. Variants in this gene are known to cause an autosomal recessive syndrome involving 3-methylglutaconic aciduria, neurological dysfunction, cataracts, and neutropenia that is often fatal in childhood however, there is likely a reporting bias toward severe cases. Using RNAseq and quantitative proteomics we validated causation and gained insight into genotype:phenotype correlation. Clinical follow-up of patients with CLPB deficiency who survived to adulthood identified POI and infertility as a common postpubertal ailment. A novel splicing variant is associated with CLPB deficiency in an in idual who survived to adulthood. POI is a common feature of postpubertal female in iduals with CLPB deficiency. Patients with CLPB deficiency should be referred to pediatric gynecologists/endocrinologists for prompt POI diagnosis and hormone replacement therapy to minimize associated comorbidities.
Biogenesis of the spacious Coxiella-containing vacuole depends on host transcription factors TFEB and TFE3.
Publisher: American Society for Microbiology
Date: 20-02-2019
DOI: 10.1128/IAI.00534-19
Abstract: Coxiella burnetii is an obligate intracellular bacterial pathogen that replicates inside the lysosome-derived Coxiella -containing vacuole (CCV). To establish this unique niche, C. burnetii requires the Dot/Icm type IV secretion system (T4SS) to translocate a cohort of effector proteins into the host cell, which modulate multiple cellular processes.
Biogenesis of mitochondrial β-barrel proteins: the POTRA domain is involved in precursor release from the SAM complex
Publisher: American Society for Cell Biology (ASCB)
Date: 15-08-2011
Abstract: The mitochondrial outer membrane contains proteinaceous machineries for the translocation of precursor proteins. The sorting and assembly machinery (SAM) is required for the insertion of β‑barrel proteins into the outer membrane. Sam50 is the channel-forming core subunit of the SAM complex and belongs to the BamA/Sam50/Toc75 family of proteins that have been conserved from Gram-negative bacteria to mitochondria and chloroplasts. These proteins contain one or more N-terminal polypeptide transport-associated (POTRA) domains. POTRA domains can bind precursor proteins, however, different views exist on the role of POTRA domains in the biogenesis of β-barrel proteins. It has been suggested that the single POTRA domain of mitochondrial Sam50 plays a receptor-like function at the SAM complex. We established a system to monitor the interaction of chemical amounts of β-barrel precursor proteins with the SAM complex of wild-type and mutant yeast in organello. We report that the SAM complex lacking the POTRA domain of Sam50 efficiently binds β-barrel precursors, but is impaired in the release of the precursors. These results indicate the POTRA domain of Sam50 is not essential for recognition of β-barrel precursors but functions in a subsequent step to promote the release of precursor proteins from the SAM complex.
Mitochondrial biology and dysfunction in secondary mitochondrial disease
Publisher: The Royal Society
Date: 12-2022
DOI: 10.1098/RSOB.220274
Abstract: Mitochondrial diseases are a broad, genetically heterogeneous class of metabolic disorders characterized by deficits in oxidative phosphorylation (OXPHOS). Primary mitochondrial disease (PMD) defines pathologies resulting from mutation of mitochondrial DNA (mtDNA) or nuclear genes affecting either mtDNA expression or the biogenesis and function of the respiratory chain. Secondary mitochondrial disease (SMD) arises due to mutation of nuclear-encoded genes independent of, or indirectly influencing OXPHOS assembly and operation. Despite instances of novel SMD increasing year-on-year, PMD is much more widely discussed in the literature. Indeed, since the implementation of next generation sequencing (NGS) techniques in 2010, many novel mitochondrial disease genes have been identified, approximately half of which are linked to SMD. This review will consolidate existing knowledge of SMDs and outline discrete categories within which to better understand the ersity of SMD phenotypes. By providing context to the biochemical and molecular pathways perturbed in SMD, we hope to further demonstrate the intricacies of SMD pathologies outside of their indirect contribution to mitochondrial energy generation.
The morphology proteins Mdm12/Mmm1 function in the major β-barrel assembly pathway of mitochondria
Publisher: Wiley
Date: 05-04-2007
Proteomic Identification of Coxiella burnetii Effector Proteins Targeted to the Host Cell Mitochondria During Infection
Publisher: Elsevier BV
Date: 2021
Inhibition of Bak activation by VDAC2 is dependent on the Bak transmembrane anchor
Publisher: Elsevier BV
Date: 11-2010
Author response: Function of hTim8a in complex IV assembly in neuronal cells provides insight into pathomechanism underlying Mohr-Tranebjærg syndrome
Publisher: eLife Sciences Publications, Ltd
Date: 26-10-2019
The TIM22 complex regulates mitochondrial one-carbon metabolism by mediating the import of Sideroflexins
Publisher: Cold Spring Harbor Laboratory
Date: 07-02-2020
DOI: 10.1101/2020.02.06.937920
Abstract: The Acylglycerol Kinase (AGK) is a mitochondrial lipid kinase that contributes to protein biogenesis as a subunit of the TIM22 complex at the inner mitochondrial membrane. Mutations in AGK cause Sengers syndrome, an autosomal recessive condition characterized by congenital cataracts, hypertrophic cardiomyopathy, skeletal myopathy and lactic acidosis. We undertook proteomic profiling of Sengers patient fibroblasts and an AGK KO cell line to map the proteomic changes that ensue upon AGK dysfunction. This uncovered extensive remodelling of mitochondrial one-carbon metabolism enzymes and showed that inner membrane serine transporters, Sideroflexins (SFXNs), are novel substrates of the TIM22 complex. Deletion of SFXN1 recapitulates the remodelling of one-carbon metabolism observed in Sengers patient cells. Proliferation of cells lacking AGK is perturbed in the absence of exogenous serine and rescuable through addition of formate, highlighting the dysregulation of one carbon metabolism as a key molecular feature in the biology of Sengers syndrome.
Mitofusins 'bridge' the gap between oxidative stress and mitochondrial hyperfusion
Publisher: EMBO
Date: 11-09-2012
Biogenesis of the Mitochondrial TOM Complex
Publisher: Elsevier BV
Date: 2008
Import of nuclear-encoded proteins into mitochondria
Publisher: Wiley
Date: 2003
DOI: 10.1113/EPH8802501
Abstract: The majority of mitochondrial proteins are encoded by nuclear genes, synthesized in the cytosol and subsequently imported into mitochondria through protein translocation machineries of the outer and inner membranes. In this review, we discuss the arrangement of the various translocation complexes and the function of in idual import components. We also outline the various targeting pathways that preproteins can take in order to reach their appropriate sub-mitochondrial compartment.
Tim29 is a novel subunit of the human TIM22 translocase and is involved in complex assembly and stability
Publisher: eLife Sciences Publications, Ltd
Date: 24-08-2016
DOI: 10.7554/ELIFE.17463
Abstract: The TIM22 complex mediates the import of hydrophobic carrier proteins into the mitochondrial inner membrane. While the TIM22 machinery has been well characterised in yeast, the human complex remains poorly characterised. Here, we identify Tim29 (C19orf52) as a novel, metazoan-specific subunit of the human TIM22 complex. The protein is integrated into the mitochondrial inner membrane with it’s C-terminus exposed to the intermembrane space. Tim29 is required for the stability of the TIM22 complex and functions in the assembly of hTim22. Furthermore, Tim29 contacts the Translocase of the Outer Mitochondrial Membrane, TOM complex, enabling a mechanism for transport of hydrophobic carrier substrates across the aqueous intermembrane space. Identification of Tim29 highlights the significance of analysing mitochondrial import systems across phylogenetic boundaries, which can reveal novel components and mechanisms in higher organisms.
Alternative function for the mitochondrial SAM complex in biogenesis of α-helical TOM proteins
Publisher: Rockefeller University Press
Date: 26-11-2007
Abstract: The mitochondrial outer membrane contains two preprotein translocases: the general translocase of outer membrane (TOM) and the β-barrel–specific sorting and assembly machinery (SAM). TOM functions as the central entry gate for nuclear-encoded proteins. The channel-forming Tom40 is a β-barrel protein, whereas all Tom receptors and small Tom proteins are membrane anchored by a transmembrane α-helical segment in their N- or C-terminal portion. Synthesis of Tom precursors takes place in the cytosol, and their import occurs via preexisting TOM complexes. The precursor of Tom40 is then transferred to SAM for membrane insertion and assembly. Unexpectedly, we find that the biogenesis of α-helical Tom proteins with a membrane anchor in the C-terminal portion is SAM dependent. Each SAM protein is necessary for efficient membrane integration of the receptor Tom22, whereas assembly of the small Tom proteins depends on Sam37. Thus, the substrate specificity of SAM is not restricted to β-barrel proteins but also includes the majority of α-helical Tom proteins.
Mitochondria—hubs for regulating cellular biochemistry: emerging concepts and networks
Publisher: The Royal Society
Date: 08-2019
DOI: 10.1098/RSOB.190126
Abstract: Mitochondria are iconic structures in biochemistry and cell biology, traditionally referred to as the powerhouse of the cell due to a central role in energy production. However, modern-day mitochondria are recognized as key players in eukaryotic cell biology and are known to regulate crucial cellular processes, including calcium signalling, cell metabolism and cell death, to name a few. In this review, we will discuss foundational knowledge in mitochondrial biology and provide snapshots of recent advances that showcase how mitochondrial function regulates other cellular responses.
Adaptor proteins MiD49 and MiD51 can act independently of Mff and Fis1 in Drp1 recruitment and are specific for mitochondrial fission
Publisher: Elsevier BV
Date: 09-2013
Mechanisms of protein sorting in mitochondria
Publisher: Cold Spring Harbor Laboratory
Date: 10-2012
Response: The Mitochondrial β-Signal and Protein Sorting
Publisher: Elsevier BV
Date: 12-2008
Mitochondrial protein transport in health and disease.
Publisher: Elsevier BV
Date: 04-2017
DOI: 10.1016/J.SEMCDB.2017.07.028
Abstract: Mitochondria are fundamental structures that fulfil important and erse functions within cells, including cellular respiration and iron-sulfur cluster biogenesis. Mitochondrial function is reliant on the organelles proteome, which is maintained and adjusted depending on cellular requirements. The majority of mitochondrial proteins are encoded by nuclear genes and must be trafficked to, and imported into the organelle following synthesis in the cytosol. These nuclear-encoded mitochondrial precursors utilise dynamic and multimeric translocation machines to traverse the organelles membranes and be partitioned to the appropriate mitochondrial subcompartment. Yeast model systems have been instrumental in establishing the molecular basis of mitochondrial protein import machines and mechanisms, however unique players and mechanisms are apparent in higher eukaryotes. Here, we review our current knowledge on mitochondrial protein import in human cells and how dysfunction in these pathways can lead to disease.
Mitochondrial morphology and protein import-A tight connection?
Publisher: Elsevier BV
Date: 05-2006
DOI: 10.1016/J.BBAMCR.2006.02.008
Abstract: Although the field of mitochondrial protein import and assembly may have initially been viewed as a completely distinct area of investigation to that of mitochondrial morphology and dynamics, recent findings have noted a clear influence on organelle morphology by perturbations in protein import pathways. This review aims to provide an overview of the mitochondrial import machinery in context of the recent link between translocation components and organelle structure, in addition to conferring the questions and challenges that have surfaced due to these observations.
Eprenetapopt triggers ferroptosis, inhibits NFS1 cysteine desulfurase, and synergizes with serine and glycine dietary restriction
Publisher: American Association for the Advancement of Science (AAAS)
Date: 16-09-2022
Abstract: The mechanism of action of eprenetapopt (APR-246, PRIMA-1 MET ) as an anticancer agent remains unresolved, although the clinical development of eprenetapopt focuses on its reported mechanism of action as a mutant-p53 reactivator. Using unbiased approaches, this study demonstrates that eprenetapopt depletes cellular antioxidant glutathione levels by increasing its turnover, triggering a nonapoptotic, iron-dependent form of cell death known as ferroptosis. Deficiency in genes responsible for supplying cancer cells with the substrates for de novo glutathione synthesis ( SLC7A11 , SHMT2 , and MTHFD1L ), as well as the enzymes required to synthesize glutathione ( GCLC and GCLM ), augments the activity of eprenetapopt. Eprenetapopt also inhibits iron-sulfur cluster biogenesis by limiting the cysteine desulfurase activity of NFS1, which potentiates ferroptosis and may restrict cellular proliferation. The combination of eprenetapopt with dietary serine and glycine restriction synergizes to inhibit esophageal xenograft tumor growth. These findings reframe the canonical view of eprenetapopt from a mutant-p53 reactivator to a ferroptosis inducer.
Levels of human Fis1 at the mitochondrial outer membrane regulate mitochondrial morphology
Publisher: The Company of Biologists
Date: 03-2004
DOI: 10.1242/JCS.01058
Abstract: Mitochondria undergo balanced fission and fusion events that enable their appropriate networking within the cell. In yeast, three factors have been identified that co-ordinate fission events at the mitochondrial outer membrane. Fis1p acts as the outer membrane receptor for recruitment of the dynamin member, Dnm1p and the WD40-repeat-containing protein Mdv1p. In mammals, the Dnm1p counterpart Drp1 has been characterized, but other components have not. Here, we report the characterization of human Fis1 (hFis1). hFis1 is inserted into the mitochondrial outer membrane via a C-terminal transmembrane domain that, along with a short basic segment, is essential for its targeting. Although expression of hFis1 does not complement the phenotype of yeast cells lacking Fis1p, overexpression of hFis1 in tissue culture cells nevertheless causes mitochondrial fragmentation and aggregation. This aggregation could be suppressed by expressing a dominant-negative Drp1 mutant (Drp1K38A). Knockdown of hFis1 in COS-7 cells using RNA interference results in mitochondrial morphology defects with notable extensions in the length of mitochondrial tubules. These results indicate that the levels of hFis1 at the mitochondrial surface influences mitochondrial fission events and hence overall mitochondrial morphology within the cell.
Mitochondrial diseases caused by dysfunctional mitochondrial protein import.
Publisher: Portland Press Ltd.
Date: 04-10-2018
DOI: 10.1042/BST20180239
Abstract: Mitochondria are essential organelles which perform complex and varied functions within eukaryotic cells. Maintenance of mitochondrial health and functionality is thus a key cellular priority and relies on the organelle's extensive proteome. The mitochondrial proteome is largely encoded by nuclear genes, and mitochondrial proteins must be sorted to the correct mitochondrial sub-compartment post-translationally. This essential process is carried out by multimeric and dynamic translocation and sorting machineries, which can be found in all four mitochondrial compartments. Interestingly, advances in the diagnosis of genetic disease have revealed that mutations in various components of the human import machinery can cause mitochondrial disease, a heterogenous and often severe collection of disorders associated with energy generation defects and a multisystem presentation often affecting the cardiovascular and nervous systems. Here, we review our current understanding of mitochondrial protein import systems in human cells and the molecular basis of mitochondrial diseases caused by defects in these pathways.
Sengers Syndrome-Associated Mitochondrial Acylglycerol Kinase Is a Subunit of the Human TIM22 Protein Import Complex.
Publisher: Elsevier BV
Date: 08-2017
DOI: 10.1016/J.MOLCEL.2017.06.014
Abstract: Acylglycerol kinase (AGK) is a mitochondrial lipid kinase that catalyzes the phosphorylation of monoacylglycerol and diacylglycerol to lysophosphatidic acid and phosphatidic acid, respectively. Mutations in AGK cause Sengers syndrome, which is characterized by congenital cataracts, hypertrophic cardiomyopathy, skeletal myopathy, exercise intolerance, and lactic acidosis. Here we identified AGK as a subunit of the mitochondrial TIM22 protein import complex. We show that AGK functions in a kinase-independent manner to maintain the integrity of the TIM22 complex, where it facilitates the import and assembly of mitochondrial carrier proteins. Mitochondria isolated from Sengers syndrome patient cells and tissues show a destabilized TIM22 complex and defects in the biogenesis of carrier substrates. Consistent with this phenotype, we observe perturbations in the tricarboxylic acid (TCA) cycle in cells lacking AGK. Our identification of AGK as a bona fide subunit of TIM22 provides an exciting and unexpected link between mitochondrial protein import and Sengers syndrome.
Mitochondrial protein import machineries and lipids: A functional connection
Publisher: Elsevier BV
Date: 03-2011
DOI: 10.1016/J.BBAMEM.2010.08.003
Abstract: Protein trafficking and translocation are essential processes in even the simplest living cells. The compartmentalisation within eukaryotic cells places a very high demand on the fidelity of protein trafficking and translocation, since a large percentage of the cell's protein complement is inserted into, or translocated across membranes. Indeed, most mitochondrial proteins are imported from the cytosol into the organelle and reach their final destination with the assistance of versatile translocation machineries. The first components involved in mitochondrial protein import were identified about 20years ago and over the last two decades many new factors and machineries have been brought to light. However, in spite of these discoveries we still have much to explore regarding the molecular mechanisms that distinguish the different mitochondrial import pathways. In particular, an open question that requires deeper exploration is the role of lipids and lipid modifying enzymes in this process. Mitochondrial biogenesis requires the coordinated synthesis and import of both proteins and phospholipids, however, these have typically been considered as distinct research fields. Recent findings have placed phospholipids at the forefront of research dealing with mitochondrial biogenesis, in particular their role in the regulation of mitochondrial transport machineries. This article is part of a Special Issue entitled Protein translocation across or insertion into membranes.
Sorting and assembly of mitochondrial outer membrane proteins
Publisher: Elsevier BV
Date: 07-2008
DOI: 10.1016/J.BBABIO.2008.03.017
Abstract: In the last years the picture of protein import into the mitochondria has become much more complicated in terms of new components and new sorting pathways. These novel findings have also changed views concerning the biogenesis pathway of mitochondrial outer membrane proteins. In addition to proteins anchored with transmembrane alpha-helices, the endosymbiotic origin of the mitochondria has resulted in the presence of transmembrane beta-barrels in this compartment. The sorting and assembly pathway of outer membrane proteins involves three machineries: the translocase of the outer membrane (TOM complex) the sorting and assembly machinery (SAM complex) and the MDM complex (mitochondrial distribution and morphology). Here we review recent developments on the biogenesis pathways of outer membrane proteins with a focus on Tom proteins, the most intensively studied class of these precursor proteins.
A Farnesylated Coxiella burnetii Effector Forms a Multimeric Complex at the Mitochondrial Outer Membrane during Infection
Publisher: American Society for Microbiology
Date: 05-2017
DOI: 10.1128/IAI.01046-16
Abstract: Coxiella burnetii , the causative agent of Q fever, establishes a unique lysosome-derived intracellular niche termed the Coxiella -containing vacuole (CCV). The Dot/Icm-type IVB secretion system is essential for the biogenesis of the CCV and the intracellular replication of Coxiella . Effector proteins, translocated into the host cell through this apparatus, act to modulate host trafficking and signaling processes to facilitate CCV development. Here we investigated the role of CBU0077, a conserved Coxiella effector that had previously been observed to localize to lysosomal membranes. CBU0077 was dispensable for the intracellular replication of Coxiella in HeLa and THP-1 cells and did not appear to participate in CCV biogenesis. Intriguingly, native and epitope-tagged CBU0077 produced by Coxiella displayed specific punctate localization at host cell mitochondria. As such, we designated CBU0077 MceA ( m itochondrial C oxiella e ffector protein A ). Analysis of ectopically expressed MceA truncations revealed that the capacity to traffic to mitochondria is encoded within the first 84 amino acids of this protein. MceA is farnesylated by the host cell however, this does not impact mitochondrial localization. Examination of mitochondria isolated from infected cells revealed that MceA is specifically integrated into the mitochondrial outer membrane and forms a complex of approximately 120 kDa. Engineering Coxiella to express either MceA tagged with 3×FLAG or MceA tagged with 2×hemagglutinin allowed us to perform immunoprecipitation experiments that showed that MceA forms a homo-oligomeric species at the mitochondrial outer membrane during infection. This research reveals that mitochondria are a bona fide target of Coxiella effectors and MceA is a complex-forming effector at the mitochondrial outer membrane during Coxiella infection.
Mitochondrial protein homeostasis
Publisher: Wiley
Date: 22-01-2013
DOI: 10.1002/IUB.1122
Abstract: Mitochondria use 800-1,500 proteins to perform their biological functions in the eukaryotic cells. Distinct transport and sorting mechanisms are responsible for the delivery of proteins to the correct location within mitochondria. Mitochondrial proteins undergo processing events and form functional assemblies. Finally, non-functional proteins are cleared to maintain healthy mitochondria. We provide an overview of the processes collectively contributing to the maintenance of mitochondrial protein homeostasis, which is critical for cell physiology and survival.
Huntingtin Inclusions Trigger Cellular Quiescence, Deactivate Apoptosis, and Lead to Delayed Necrosis
Publisher: Elsevier BV
Date: 05-2017
DOI: 10.1016/J.CELREP.2017.04.029
Abstract: Competing models exist in the literature for the relationship between mutant Huntingtin exon 1 (Httex1) inclusion formation and toxicity. In one, inclusions are adaptive by sequestering the proteotoxicity of soluble Httex1. In the other, inclusions compromise cellular activity as a result of proteome co-aggregation. Using a biosensor of Httex1 conformation in mammalian cell models, we discovered a mechanism that reconciles these competing models. Newly formed inclusions were composed of disordered Httex1 and ribonucleoproteins. As inclusions matured, Httex1 reconfigured into amyloid, and other glutamine-rich and prion domain-containing proteins were recruited. Soluble Httex1 caused a hyperpolarized mitochondrial membrane potential, increased reactive oxygen species, and promoted apoptosis. Inclusion formation triggered a collapsed mitochondrial potential, cellular quiescence, and deactivated apoptosis. We propose a revised model where sequestration of soluble Httex1 inclusions can remove the trigger for apoptosis but also co-aggregate other proteins, which curtails cellular metabolism and leads to a slow death by necrosis.
The MIA system for protein import into the mitochondrial intermembrane space
Publisher: Elsevier BV
Date: 04-2008
DOI: 10.1016/J.BBAMCR.2007.10.004
Abstract: When thinking of the mitochondrial intermembrane space we envisage a small compartment that is bordered by the mitochondrial outer and inner membranes. Despite this somewhat simplified perception the intermembrane space has remained a central focus in mitochondrial biology. This compartment accommodates many proteinaceous factors that play critical roles in mitochondrial and cellular metabolism, including the regulation of programmed cell death and energy conversion. The mechanism by which intermembrane space proteins are transported into the organelle and folded remained largely unknown until recently. In pursuit of the answer to this question a novel machinery, the Mitochondrial Intermembrane Space Assembly machinery, exploiting a unique regulated thiol-disulfide exchange mechanism has been revealed. This exciting discovery has not only put in place novel concepts for the biogenesis of intermembrane space precursors but also raises important implications on the mechanisms involved in the generation and transfer of disulfide bonds.
The regulation of mitochondrial morphology: Intricate mechanisms and dynamic machinery
Publisher: Elsevier BV
Date: 10-2011
DOI: 10.1016/J.CELLSIG.2011.05.021
Abstract: Mitochondria typically form a reticular network radiating from the nucleus, creating an interconnected system that supplies the cell with essential energy and metabolites. These mitochondrial networks are regulated through the complex coordination of fission, fusion and distribution events. While a number of key mitochondrial morphology proteins have been identified, the precise mechanisms which govern their activity remain elusive. Moreover, post translational modifications including ubiquitination, phosphorylation and sumoylation of the core machinery are thought to regulate both fusion and ision of the network. These proteins can undergo several different modifications depending on cellular signals, environment and energetic demands of the cell. Proteins involved in mitochondrial morphology may also have dual roles in both dynamics and apoptosis, with regulation of these proteins under tight control of the cell to ensure correct function. The absolute reliance of the cell on a functional mitochondrial network is highlighted in neurons, which are particularly vulnerable to any changes in organelle dynamics due to their unique biochemical requirements. Recent evidence suggests that defects in the shape or distribution of mitochondria correlate with the progression of neurodegenerative diseases such as Alzheimer's, Huntington's and Parkinson's disease. This review focuses on our current understanding of the mitochondrial morphology machinery in cell homeostasis, apoptosis and neurodegeneration, and the post translational modifications that regulate these processes.
Rotavirus NSP6 localizes to mitochondria via a predicted N-terminal α-helix
Publisher: Microbiology Society
Date: 12-2015
DOI: 10.1099/JGV.0.000294
Abstract: Specific roles have been ascribed to each of the 12 known rotavirus proteins apart from the non-structural protein 6 (NSP6). However, NSP6 may be present at sites of viral replication within the cytoplasm. Here we report that NSP6 from erse species of rotavirus A localizes to mitochondria via conserved sequences in a predicted N-terminal α-helix. This suggests that NSP6 may affect mitochondrial functions during rotavirus infection.
Diverse mechanisms and machineries for import of mitochondrial proteins
Publisher: Walter de Gruyter GmbH
Date: 14-08-2007
DOI: 10.1515/BC.2007.097
Abstract: Mitochondria are ubiquitous organelles that play an essential role in energy conversion and biosynthetic pathways in eukaryotic cells. Most mitochondrial proteins must be imported from the cytosol and sorted into one of the four mitochondrial subcompartments, the outer membrane, the intermembrane space, the inner membrane and the matrix. Studies in recent years revealed a remarkable ersity of mechanisms and machineries that are required for the import of proteins into mitochondria. At least four different pathways for the sorting and assembly of nuclear-encoded mitochondrial proteins have been identified.
Identification of the signal directing Tim9 and Tim10 into the intermembrane space of mitochondria
Publisher: American Society for Cell Biology (ASCB)
Date: 15-05-2009
Abstract: The intermembrane space of mitochondria contains the specific mitochondrial intermembrane space assembly (MIA) machinery that operates in the biogenesis pathway of precursor proteins destined to this compartment. The Mia40 component of the MIA pathway functions as a receptor and binds incoming precursors, forming an essential early intermediate in the biogenesis of intermembrane space proteins. The elements that are crucial for the association of the intermembrane space precursors with Mia40 have not been determined. In this study, we found that a region within the Tim9 and Tim10 precursors, consisting of only nine amino acid residues, functions as a signal for the engagement of substrate proteins with the Mia40 receptor. Furthermore, the signal contains sufficient information to facilitate the transfer of proteins across the outer membrane to the intermembrane space. Thus, here we have identified the mitochondrial intermembrane space sorting signal required for delivery of proteins to the mitochondrial intermembrane space.
Profiling phosphoproteins of yeast mitochondria reveals a role of phosphorylation in assembly of the ATP synthase
Publisher: Elsevier BV
Date: 11-2007
Author response: Function of hTim8a in complex IV assembly in neuronal cells provides insight into pathomechanism underlying Mohr-Tranebjærg syndrome
Publisher: eLife Sciences Publications, Ltd
Date: 26-10-2019
Human Tim8a, Tim8b and Tim13 are auxiliary assembly factors of mature Complex IV
Publisher: EMBO
Date: 05-06-2023
Abstract: Human Tim8a and Tim8b are paralogous intermembrane space proteins of the small TIM chaperone family. Yeast small TIMs function in the trafficking of proteins to the outer and inner mitochondrial membranes. This putative import function for hTim8a and hTim8b has been challenged in human models, but their precise molecular function(s) remains undefined. Likewise, the necessity for human cells to encode two Tim8 proteins and whether any potential redundancy exists is unclear. We demonstrate that hTim8a and hTim8b function in the assembly of cytochrome c oxidase (Complex IV). Using affinity enrichment mass spectrometry, we define the interaction network of hTim8a, hTim8b and hTim13, identifying subunits and assembly factors of the Complex IV COX2 module. hTim8‐deficient cells have a COX2 and COX3 module defect and exhibit an accumulation of the Complex IV S2 subcomplex. These data suggest that hTim8a and hTim8b function in assembly of Complex IV via interactions with intermediate‐assembly subcomplexes. We propose that hTim8–hTim13 complexes are auxiliary assembly factors involved in the formation of the Complex IV S3 subcomplex during assembly of mature Complex IV.
Cooperative and independent roles of the Drp1 adaptors Mff, MiD49 and MiD51 in mitochondrial fission.
Publisher: The Company of Biologists
Date: 2016
DOI: 10.1242/JCS.185165
Abstract: Cytosolic Dynamin-related protein 1 (Drp1) is required for both mitochondrial and peroxisomal fission. Drp1-dependent ision of these organelles is facilitated by a number of adaptor proteins at mitochondrial and peroxisomal surfaces. To investigate the interplay of these adaptor proteins, we used gene-editing technology to create a suite of cell lines lacking adaptors MiD49, MiD51, MFF and Fis1. Increased mitochondrial connectivity was observed following loss of in idual adaptors while this was further enhanced following the combined loss of MiD51 and Mff. Moreover, loss of adaptors also conferred increased resistance of cells to intrinsic apoptotic stimuli, with MiD49/MiD51 showing a more prominent role. Using a proximity-based biotin labeling approach, we found close associations between MiD51, Mff and Drp1, but not Fis1. Furthermore, we find that MiD51 can suppress Mff-dependent enhancement of Drp1 GTPase activity. Our data indicates that Mff and MiD51 regulate Drp1 in specific ways to promote mitochondrial fission.
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