1
|
Knöringer K, Groh C, Krämer L, Stein KC, Hansen KG, Zimmermann J, Morgan B, Herrmann JM, Frydman J, Boos F. The unfolded protein response of the endoplasmic reticulum supports mitochondrial biogenesis by buffering nonimported proteins. Mol Biol Cell 2023; 34:ar95. [PMID: 37379206 PMCID: PMC10551703 DOI: 10.1091/mbc.e23-05-0205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 06/15/2023] [Accepted: 06/22/2023] [Indexed: 06/30/2023] Open
Abstract
Almost all mitochondrial proteins are synthesized in the cytosol and subsequently targeted to mitochondria. The accumulation of nonimported precursor proteins occurring upon mitochondrial dysfunction can challenge cellular protein homeostasis. Here we show that blocking protein translocation into mitochondria results in the accumulation of mitochondrial membrane proteins at the endoplasmic reticulum, thereby triggering the unfolded protein response (UPRER). Moreover, we find that mitochondrial membrane proteins are also routed to the ER under physiological conditions. The level of ER-resident mitochondrial precursors is enhanced by import defects as well as metabolic stimuli that increase the expression of mitochondrial proteins. Under such conditions, the UPRER is crucial to maintain protein homeostasis and cellular fitness. We propose the ER serves as a physiological buffer zone for those mitochondrial precursors that cannot be immediately imported into mitochondria while engaging the UPRER to adjust the ER proteostasis capacity to the extent of precursor accumulation.
Collapse
Affiliation(s)
| | - Carina Groh
- Cell Biology, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Lena Krämer
- Cell Biology, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Kevin C. Stein
- Department of Biology, Stanford University, Stanford, CA 94305
| | - Katja G. Hansen
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115
| | - Jannik Zimmermann
- Institute of Biochemistry, Center for Human and Molecular Biology (ZHMB), Saarland University, 66123 Saarbrücken, Germany
| | - Bruce Morgan
- Institute of Biochemistry, Center for Human and Molecular Biology (ZHMB), Saarland University, 66123 Saarbrücken, Germany
| | | | - Judith Frydman
- Department of Biology, Stanford University, Stanford, CA 94305
- Department of Genetics, Stanford University, Stanford, CA 94305
| | - Felix Boos
- Cell Biology, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| |
Collapse
|
2
|
Schlagowski AM, Knöringer K, Morlot S, Sánchez Vicente A, Flohr T, Krämer L, Boos F, Khalid N, Ahmed S, Schramm J, Murschall LM, Haberkant P, Stein F, Riemer J, Westermann B, Braun RJ, Winklhofer KF, Charvin G, Herrmann JM. Increased levels of mitochondrial import factor Mia40 prevent the aggregation of polyQ proteins in the cytosol. EMBO J 2021; 40:e107913. [PMID: 34191328 PMCID: PMC8365258 DOI: 10.15252/embj.2021107913] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 05/25/2021] [Accepted: 05/31/2021] [Indexed: 12/11/2022] Open
Abstract
The formation of protein aggregates is a hallmark of neurodegenerative diseases. Observations on patient samples and model systems demonstrated links between aggregate formation and declining mitochondrial functionality, but causalities remain unclear. We used Saccharomyces cerevisiae to analyze how mitochondrial processes regulate the behavior of aggregation‐prone polyQ protein derived from human huntingtin. Expression of Q97‐GFP rapidly led to insoluble cytosolic aggregates and cell death. Although aggregation impaired mitochondrial respiration only slightly, it considerably interfered with the import of mitochondrial precursor proteins. Mutants in the import component Mia40 were hypersensitive to Q97‐GFP, whereas Mia40 overexpression strongly suppressed the formation of toxic Q97‐GFP aggregates both in yeast and in human cells. Based on these observations, we propose that the post‐translational import of mitochondrial precursor proteins into mitochondria competes with aggregation‐prone cytosolic proteins for chaperones and proteasome capacity. Mia40 regulates this competition as it has a rate‐limiting role in mitochondrial protein import. Therefore, Mia40 is a dynamic regulator in mitochondrial biogenesis that can be exploited to stabilize cytosolic proteostasis.
Collapse
Affiliation(s)
| | | | - Sandrine Morlot
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France.,Université de Strasbourg, Illkirch, France
| | - Ana Sánchez Vicente
- Department of Molecular Cell Biology, Institute of Biochemistry and Pathobiochemistry, Ruhr University Bochum, Bochum, Germany
| | - Tamara Flohr
- Cell Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Lena Krämer
- Cell Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Felix Boos
- Cell Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Nabeel Khalid
- German Research Center for Artificial Intelligence DFKI, Kaiserslautern, Germany
| | - Sheraz Ahmed
- German Research Center for Artificial Intelligence DFKI, Kaiserslautern, Germany
| | - Jana Schramm
- Cell Biology, University of Bayreuth, Bayreuth, Germany
| | | | - Per Haberkant
- Proteomics Core Facility, EMBL Heidelberg, Heidelberg, Germany
| | - Frank Stein
- Proteomics Core Facility, EMBL Heidelberg, Heidelberg, Germany
| | - Jan Riemer
- Biochemistry, University of Cologne, Cologne, Germany
| | | | - Ralf J Braun
- Cell Biology, University of Bayreuth, Bayreuth, Germany.,Neurodegeneration, Danube Private University, Krems/Donau, Austria
| | - Konstanze F Winklhofer
- Department of Molecular Cell Biology, Institute of Biochemistry and Pathobiochemistry, Ruhr University Bochum, Bochum, Germany
| | - Gilles Charvin
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France.,Université de Strasbourg, Illkirch, France
| | | |
Collapse
|
3
|
Laborenz J, Bykov YS, Knöringer K, Räschle M, Filker S, Prescianotto-Baschong C, Spang A, Tatsuta T, Langer T, Storchová Z, Schuldiner M, Herrmann JM. The ER protein Ema19 facilitates the degradation of nonimported mitochondrial precursor proteins. Mol Biol Cell 2021; 32:664-674. [PMID: 33596095 PMCID: PMC8108515 DOI: 10.1091/mbc.e20-11-0748] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
For the biogenesis of mitochondria, hundreds of proteins need to be targeted from the cytosol into the various compartments of this organelle. The intramitochondrial targeting routes these proteins take to reach their respective location in the organelle are well understood. However, the early targeting processes, from cytosolic ribosomes to the membrane of the organelle, are still largely unknown. In this study, we present evidence that an integral membrane protein of the endoplasmic reticulum (ER), Ema19, plays a role in this process. Mutants lacking Ema19 show an increased stability of mitochondrial precursor proteins, indicating that Ema19 promotes the proteolytic degradation of nonproductive precursors. The deletion of Ema19 improves the growth of respiration-deficient cells, suggesting that Ema19-mediated degradation can compete with productive protein import into mitochondria. Ema19 is the yeast representative of a conserved protein family. The human Ema19 homologue is known as sigma 2 receptor or TMEM97. Though its molecular function is not known, previous studies suggested a role of the sigma 2 receptor as a quality control factor in the ER, compatible with our observations about Ema19. More globally, our data provide an additional demonstration of the important role of the ER in mitochondrial protein targeting.
Collapse
Affiliation(s)
- Janina Laborenz
- Cell Biology, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Yury S Bykov
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | | | - Markus Räschle
- Molecular Genetics, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Sabine Filker
- Molecular Ecology, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | | | - Anne Spang
- Biozentrum, University of Basel, CH-4056 Basel, Switzerland
| | - Takashi Tatsuta
- Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany
| | - Thomas Langer
- Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany
| | - Zuzana Storchová
- Molecular Genetics, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Maya Schuldiner
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | | |
Collapse
|