scholarly journals Mitochondrial carrier protein overloading and misfolding induce aggresomes and proteostatic adaptations in the cytosol

2019 ◽  
Vol 30 (11) ◽  
pp. 1272-1284 ◽  
Author(s):  
Yaxin Liu ◽  
Xiaowen Wang ◽  
Liam P. Coyne ◽  
Yuan Yang ◽  
Yue Qi ◽  
...  
Keyword(s):  
Stress Responses ◽  
Protein Import ◽  
Protein Targeting ◽  
Human Cells ◽  
Mitochondrial Proteins ◽  
Protein Accumulation ◽  
Carrier Protein ◽  
Mitochondrial Carrier ◽  
Fold Reduction ◽  
Mitochondrial Carrier Protein

Previous studies in yeast showed that mitochondrial stressors not directly targeting the protein import machinery can cause mitochondrial precursor overaccumulation stress (mPOS) in the cytosol independent of bioenergetics. Here, we demonstrate mPOS and stress responses in human cells. We show that overloading of mitochondrial membrane carrier, but not matrix proteins, is sufficient to induce cytosolic aggresomes and apoptosis. The aggresomes appear to triage unimported mitochondrial proteins. Interestingly, expression of highly unstable mutant variants of the mitochondrial carrier protein, Ant1, also induces aggresomes despite a greater than 20-fold reduction in protein level compared to wild type. Thus, overloading of the protein import machinery, rather than protein accumulation, is critical for aggresome induction. The data suggest that the import of mitochondrial proteins is saturable and that the cytosol is limited in degrading unimported mitochondrial proteins. In addition, we found that EGR1, eEF1a, and ubiquitin C are up-regulated by Ant1 overloading. These proteins are known to promote autophagy, protein targeting to aggresomes, and the processing of protein aggregates, respectively. Finally, we found that overexpression of the misfolded variants of Ant1 induces additional cytosolic responses including proteasomal activation. In summary, our work captured a profound effect of unimported mitochondrial proteins on cytosolic proteostasis and revealed multiple anti-mPOS mechanisms in human cells.

scholarly journals From cytosol to mitochondria: the beginning of a protein journey

2020 ◽  
Vol 401 (6-7) ◽  
pp. 645-661 ◽  
Author(s):  
Maria Clara Avendaño-Monsalve ◽  
José Carlos Ponce-Rojas ◽  
Soledad Funes
Keyword(s):  
Mitochondrial Biogenesis ◽  
Stress Responses ◽  
Protein Import ◽  
Protein Targeting ◽  
Mitochondrial Protein ◽  
Past Research ◽  
Membrane Receptors ◽  
Mitochondrial Proteins ◽  
Mitochondrial Protein Import ◽  
The Past

AbstractMitochondrial protein import is one of the key processes during mitochondrial biogenesis that involves a series of events necessary for recognition and delivery of nucleus-encoded/cytosol-synthesized mitochondrial proteins into the organelle. The past research efforts have mainly unraveled how membrane translocases ensure the correct protein sorting within the different mitochondrial subcompartments. However, early steps of recognition and delivery remain relatively uncharacterized. In this review, we discuss our current understanding about the signals on mitochondrial proteins, as well as in the mRNAs encoding them, which with the help of cytosolic chaperones and membrane receptors support protein targeting to the organelle in order to avoid improper localization. In addition, we discuss recent findings that illustrate how mistargeting of mitochondrial proteins triggers stress responses, aiming to restore cellular homeostasis.

scholarly journals Quantitative Proteomics and Differential Protein Abundance Analysis after the Depletion of PEX3 from Human Cells Identifies Additional Aspects of Protein Targeting to the ER

2021 ◽  
Vol 22 (23) ◽  
pp. 13028
Author(s):  
Richard Zimmermann ◽  
Sven Lang ◽  
Monika Lerner ◽  
Friedrich Förster ◽  
Duy Nguyen ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Protein Import ◽  
Protein Targeting ◽  
Human Cells ◽  
Protein Abundance ◽  
General Role ◽  
Differential Protein ◽  
Er Targeting ◽  
Dependent Pathway ◽  
Er Membrane

Protein import into the endoplasmic reticulum (ER) is the first step in the biogenesis of around 10,000 different soluble and membrane proteins in humans. It involves the co- or post-translational targeting of precursor polypeptides to the ER, and their subsequent membrane insertion or translocation. So far, three pathways for the ER targeting of precursor polypeptides and four pathways for the ER targeting of mRNAs have been described. Typically, these pathways deliver their substrates to the Sec61 polypeptide-conducting channel in the ER membrane. Next, the precursor polypeptides are inserted into the ER membrane or translocated into the ER lumen, which may involve auxiliary translocation components, such as the TRAP and Sec62/Sec63 complexes, or auxiliary membrane protein insertases, such as EMC and the TMCO1 complex. Recently, the PEX19/PEX3-dependent pathway, which has a well-known function in targeting and inserting various peroxisomal membrane proteins into pre-existent peroxisomal membranes, was also found to act in the targeting and, putatively, insertion of monotopic hairpin proteins into the ER. These either remain in the ER as resident ER membrane proteins, or are pinched off from the ER as components of new lipid droplets. Therefore, the question arose as to whether this pathway may play a more general role in ER protein targeting, i.e., whether it represents a fourth pathway for the ER targeting of precursor polypeptides. Thus, we addressed the client spectrum of the PEX19/PEX3-dependent pathway in both PEX3-depleted HeLa cells and PEX3-deficient Zellweger patient fibroblasts by an established approach which involved the label-free quantitative mass spectrometry of the total proteome of depleted or deficient cells, as well as differential protein abundance analysis. The negatively affected proteins included twelve peroxisomal proteins and two hairpin proteins of the ER, thus confirming two previously identified classes of putative PEX19/PEX3 clients in human cells. Interestingly, fourteen collagen-related proteins with signal peptides or N-terminal transmembrane helices belonging to the secretory pathway were also negatively affected by PEX3 deficiency, which may suggest compromised collagen biogenesis as a hitherto-unknown contributor to organ failures in the respective Zellweger patients.

scholarly journals Role of YHM1, encoding a mitochondrial carrier protein, in iron distribution of yeast

2004 ◽  
Vol 378 (2) ◽  
pp. 599-607 ◽  
Author(s):  
Emmanuel LESUISSE ◽  
Elise R. LYVER ◽  
Simon A. B. KNIGHT ◽  
Andrew DANCIS
Keyword(s):  
Protein Family ◽  
Carrier Protein ◽  
Ferric Reductase ◽  
Mitochondrial Carrier ◽  
Mitochondrial Dna Damage ◽  
Cellular Iron ◽  
Mitochondrial Transporter ◽  
Large Protein Family ◽  
Mitochondrial Carrier Protein ◽  
Mitochondrial Carrier Proteins

Mitochondrial carrier proteins are a large protein family, consisting of 35 members in Saccharomyces cerevisiae. Members of this protein family have been shown to transport varied substrates from cytoplasm to mitochondria or mitochondria to cytoplasm, although many family members do not have assigned substrates. We speculated whether one or more of these transporters will play a role in iron metabolism. Haploid yeast strains each deleted for a single mitochondrial carrier protein were analysed for alterations in iron homoeostasis. The strain deleted for YHM1 was characterized by increased and misregulated surface ferric reductase and high-affinity ferrous transport activities. Siderophore uptake from different sources was also increased, and these effects were dependent on the AFT1 iron sensor regulator. Mutants of YHM1 converted into rho°, consistent with secondary mitochondrial DNA damage from mitochondrial iron accumulation. In fact, in the Δyhm1 mutant, iron was found to accumulate in mitochondria. The accumulated iron showed decreased availability for haem synthesis, measured in isolated mitochondria using endogenously available metals and added porphyrins. The phenotypes of Δyhm1 mutants indicate a role for this mitochondrial transporter in cellular iron homoeostasis.

scholarly journals Quantitative Proteomics and Differential Protein Abundance Analysis after Depletion of PEX3 from Human Cells Identifies Additional Aspects of Protein Targeting to the ER

2021 ◽  
Author(s):  
Richard Zimmermann ◽  
Sven Lang ◽  
Monika Lerner ◽  
Friedrich G Förster ◽  
Duy Nguyen ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Protein Import ◽  
Protein Targeting ◽  
Human Cells ◽  
Protein Abundance ◽  
General Role ◽  
Differential Protein ◽  
Er Targeting ◽  
Dependent Pathway ◽  
Er Membrane

Protein import into the endoplasmic reticulum (ER) is the first step in the biogenesis of about 10,000 different soluble and membrane proteins in humans. It involves co- or post-translational targeting of precursor polypeptides to the ER and their subsequent membrane insertion or translocation. So far, three pathways for ER targeting of precursor polypeptides plus four pathways for ER targeting of mRNAs were described. Typically, these pathways deliver their substrates to the Sec61 polypeptide-conducting channel in the ER membrane. Next, the precursor polypeptides are inserted into the ER membrane or translocated into the ER lumen, which may involve auxiliary translocation components, such as the TRAP and Sec62/Sec63 complexes, or auxiliary membrane protein insertases, such as EMC and the TMCO1 complex. Recently, the PEX19/PEX3-dependent pathway, which has a well-known function in targeting and inserting various peroxisomal membrane proteins into pre-existent peroxisomal membranes, was also found to act in targeting and, putatively, inserting monotopic hairpin proteins into the ER. These either remain in the ER as resident ER membrane proteins or are pinched off from the ER as components of new lipid droplets. Therefore, the question arose if this pathway may play a more general role in ER protein targeting, i.e. represents a fourth pathway for ER targeting of precursor polypeptides. Thus, we addressed the client spectrum of the PEX19/PEX3-dependent pathway in both PEX3-depleted HeLa cells and PEX3-deficient Zellweger patient fibroblasts by an established approach, which involves label-free quantitative mass spectrometry of the total proteome of depleted or deficient cells and differential protein abundance analysis. The negatively affected proteins included twelve peroxisomal proteins and two hairpin proteins of the ER, thus confirming two previously identified classes of putative PEX19/PEX3-clients in human cells. Interestingly, fourteen collagen-related proteins with signal peptides or N-terminal transmembrane helices and belonging to the secretory pathway were also negatively affected by PEX3-deficiency, which may suggest compromised collagen biogenesis as a hitherto unknown contributor to organ failures in the respective Zellweger patients.

scholarly journals Correction: Legionella pneumophila Secretes a Mitochondrial Carrier Protein during Infection

2012 ◽  
Vol 8 (1) ◽  
Author(s):  
Pavel Dolezal ◽  
Margareta Aili ◽  
Janette Tong ◽  
Jhih-Hang Jiang ◽  
Carlo M. T. Marobbio ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Carrier Protein ◽  
Mitochondrial Carrier ◽  
Mitochondrial Carrier Protein
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