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An Msp1-containing complex removes orphaned proteins in the mitochondrial outer membrane of trypanosomes (SILAC-IP data)

ABSTRACT: The AAA-ATPase Msp1 extracts mislocalized outer membrane proteins and thus contributes to mitochondrial proteostasis. Using pull down experiments, we show that trypanosomal Msp1 localizes to both the glycosome and the mitochondrial outer membrane, where it forms a stable complex with four outer membrane proteins. The trypanosome-specific pATOM36 mediates complex assembly of alpha-helically anchored mitochondrial outer membrane proteins, such as protein translocase subunits. Inhibition of complex assembly triggers a pathway that results in the proteasomal digestion of unassembled substrates. Using inducible single, double and triple RNAi cell lines combined with proteomic analyses, we demonstrate that both TbMsp1 and the trypanosomal homolog of a cytosolic AAA-ATPase, VCP, are implicated in this quality control pathway. Moreover, in the absence of TbVCP, three out of the four TbMsp1-interacting mitochondrial proteins are required for efficient proteasomal digestion of pATOM36 substrates, suggesting they act in concert with TbMsp1. pATOM36 is a functional analogue of the yeast MIM complex, and possibly of human MTCH2, suggesting that similar mitochondrial quality control pathways linked to Msp1 might also exist in yeast and humans.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Trypanosoma Brucei

SUBMITTER: Julian Bender

LAB HEAD: Bettina Warscheid

PROVIDER: PXD039631 | Pride | 2023-07-26

REPOSITORIES: Pride

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An Msp1-containing complex removes orphaned proteins in the mitochondrial outer membrane of trypanosomes (RNAi knockdown data)

Project description:The AAA-ATPase Msp1 extracts mislocalized outer membrane proteins and thus contributes to mitochondrial proteostasis. Using pull down experiments, we show that trypanosomal Msp1 localizes to both the glycosome and the mitochondrial outer membrane, where it forms a stable complex with four outer membrane proteins. The trypanosome-specific pATOM36 mediates complex assembly of α-helically anchored mitochondrial outer membrane proteins, such as protein translocase subunits. Inhibition of complex assembly triggers a pathway that results in the proteasomal digestion of unassembled substrates. Using inducible single, double and triple RNAi cell lines combined with proteomic analyses, we demonstrate that both TbMsp1 and the trypanosomal homolog of a cytosolic AAA-ATPase, VCP, are implicated in this quality control pathway. Moreover, in the absence of TbVCP, three out of the four TbMsp1-interacting mitochondrial proteins are required for efficient proteasomal digestion of pATOM36 substrates, suggesting they act in concert with TbMsp1. pATOM36 is a functional analogue of the yeast MIM complex, and possibly of human MTCH2, suggesting that similar mitochondrial quality control pathways linked to Msp1 might also exist in yeast and humans.

2023-07-26 | PXD039634 | Pride

A hybrid TIM complex mediates protein import into hydrogenosomes of Trichomonas vaginalis

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2024-06-16 | PXD047649 | Pride

Characterisation of a highly diverged putative mitochondrial ATP synthase peripheral stalk subunit b in Trypanosoma brucei

Project description:The mitochondrial F1Fo ATP synthase of Trypanosoma brucei has been studied in detail. Whereas its F1 moiety is relatively highly conserved in structure and composition, the same is not the case for the Fo part and the peripheral stalk. A core subunit of the latter, the normally conserved subunit b, could not be identified in trypanosomes suggesting that it might be absent. Here we have identified a 17 kDa mitochondrial protein of the inner membrane that is essential for normal growth, efficient oxidative phosphorylation and membrane potential maintenance. Pulldown experiments and native PAGE analysis indicate that the protein is associated with the F1Fo ATP synthase. Its knockdown reduces the levels of Fo subunits, but not those of F1, and disturbs the cell cycle. HHpred analysis showed that the protein has structural similarities to subunit b of other species, indicating that the Fo part of the trypanosomal ATP synthase does contain a highly diverged subunit b. Thus, the Fo part of the trypanosomal ATPase synthase may be more widely conserved than initially thought.

2022-05-20 | PXD031259 | Pride

mitoCPR - a surveillance pathway that protects mitochondria in response to mitochondrial import stress

Project description:Mitochondrial functions are essential for cell viability and rely on protein import into the organelle. Various disease and stress conditions can lead to mitochondrial import defects. We find that inhibition of mitochondrial import in budding yeast activates a surveillance mechanism, mitoCPR, that is aimed at ameliorating mitochondrial import and protecting mitochondria during import stress. mitoCPR induces expression of Cis1 which associates with the mitochondrial translocase to reduce the accumulation of mitochondrial precursor proteins at the organelle surface. Clearance of precursor proteins depends on the Cis1 interacting AAA+ ATPase Msp1 and the proteasome suggesting that Cis1 facilitates degradation of un-imported proteins at the mitochondrial surface.

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Trypanosomal Pam18/Pam16 and maxicircle replication – TbPam16 CoIPs

Project description:Protein import and genome replication are essential processes for mitochondrial biogenesis and propagation. The J-domain proteins Pam16 and Pam18 regulate the presequence translocase of the mitochondrial inner membrane. In the protozoan Trypanosoma brucei, their counterparts are TbPam16 and TbPam18, which are essential for the procyclic form of the parasite, though not involved in mitochondrial protein import. Here, we show that during evolution, the two proteins have been repurposed to regulate the replication of maxicircles within the intricate kDNA network, the most complex mitochondrial genome known. TbPam18 and TbPam16 have inactive J-domains suggesting a function independent of heat shock proteins. However, their single transmembrane domain is essential for function. Pulldown of TbPam16 identifies a putative client protein, termed MaRF11, the depletion of which causes the selective loss of maxicircles, akin to the effects observed for TbPam18 and TbPam16. The level of MaRF11 is controlled by the mitochondrial proteasome. Thus, we propose a model for a membrane-bound regulatory circuit that controls maxicircle replication in response to an unknown nuclear signal. This model posits that MaRF11 directly mediates maxicircle replication, that its activity is regulated by the mitochondrial proteasome that its level is controlled by proteasomal digested that it is protected from degradation by binding to the TbPam18/TbPam16 dimer.

2024-07-20 | PXD046849 | Pride

mitoCPR - a surveillance pathway that protects mitochondria in response to mitochondrial import stress [yeast]

Project description:Mitochondrial functions are essential for cell viability and rely on protein import into the organelle. Physiological perturbations and disease conditions can lead to mitochondrial import defect. We find that in budding yeast, mitochondrial import defects result in activation of a surveillance mechanism, which we termed mitoCPR. The mitoCPR is aimed at ameliorating mitochondrial import and protecting mitochondria during import stress. This is mediated by the mitoCPR effector, Cis1, which associates with mitochondria to reduce the accumulation of mitochondrial preproteins at the organelle's surface. Clearance of preproteins depends on the AAA-ATPase Msp1 and the proteasome, suggesting that Cis1 facilitates the degradation of unimported proteins that accumulate at the mitochondrial surface. We further show that mitoCPR is critical for maintaining mitochondrial functions during mitochondrial import stress and provide evidence that it is an ancient, conserved mitochondrial protection mechanism.

2019-03-16 | GSE96727 | GEO

mitoCPR - a surveillance pathway that protects mitochondria in response to mitochondrial import stress [human]

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A MYC-driven change in mitochondrial dynamics limits stem cell properties of mammary epithelial cells (ChIP-seq)

Project description:In several developmental lineages, an increase in expression of the MYC proto-oncogene drives the transition from quiescent stem cells to transit amplifying cells. The mechanism by which MYC restricts self-renewal of adult stem cells is unknown. Here, we show that MYC activates a stereotypic transcriptional program of genes involved in protein translation and mitochondrial biogenesis in mammary epithelial cells and indirectly inhibits the YAP/TAZ co-activators that are essential for mammary stem cell self-renewal. We identify a phospholipase of the mitochondrial outer membrane, PLD6, as the mediator of MYC activity. PLD6 mediates a change in the mitochondrial fusion/fission balance that promotes nuclear export of YAP/TAZ in a LATS- and RHO-independent manner. Mouse models and human pathological data confirm that MYC suppresses YAP/TAZ activity in mammary tumors. PLD6 is also required for glutaminolysis, arguing that MYC-dependent changes in mitochondrial dynamics balance cellular energy metabolism with the self-renewal potential of adult stem cells. ChIP-Seq experiments for MYC-HA (HA-IP) performed in IMEC primary breast epithelial cells. Input-samples were sequenced as controlls.

2015-10-28 | E-GEOD-66252 | biostudies-arrayexpress

Receptor-mediated recruitment of cytosolic J-proteins to the mitochondrial outer membrane promotes assembly of preprotein translocases

Project description:Mitochondria possess elaborate machineries for the import of preproteins from the cytosol. Cytosolic factors like Hsp70 chaperones and their co-chaperones, the J-proteins, guide preproteins to the mitochondrial surface. The translocase of the mitochondrial outer membrane (TOM) forms the entry gate for precursor proteins. How proteins are delivered to the receptors Tom20, Tom22 and Tom70 is only understood in part. We identified the cytosolic J-protein Xdj1 as a specific interaction partner of the central receptor Tom22. Tom22 recruits Xdj1 to the mitochondrial surface to promote assembly of the TOM complex. A second J-protein of the cytosol, Djp1, binds to Tom70 to mediate biogenesis of the mitochondrial import (MIM) complex. Thus, by targeting distinct TOM receptors, cytosolic J-proteins promote the biogenesis of different mitochondrial preprotein translocases.

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