1
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Hegde RS, Keenan RJ. A unifying model for membrane protein biogenesis. Nat Struct Mol Biol 2024:10.1038/s41594-024-01296-5. [PMID: 38811793 DOI: 10.1038/s41594-024-01296-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Accepted: 03/25/2024] [Indexed: 05/31/2024]
Abstract
α-Helical integral membrane proteins comprise approximately 25% of the proteome in all organisms. The membrane proteome is highly diverse, varying in the number, topology, spacing and properties of transmembrane domains. This diversity imposes different constraints on the insertion of different regions of a membrane protein into the lipid bilayer. Here, we present a cohesive framework to explain membrane protein biogenesis, in which different parts of a nascent substrate are triaged between Oxa1 and SecY family members for insertion. In this model, Oxa1 family proteins insert transmembrane domains flanked by short translocated segments, whereas the SecY channel is required for insertion of transmembrane domains flanked by long translocated segments. Our unifying model rationalizes evolutionary, genetic, biochemical and structural data across organisms and provides a foundation for future mechanistic studies of membrane protein biogenesis.
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Affiliation(s)
- Ramanujan S Hegde
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, UK.
| | - Robert J Keenan
- Gordon Center for Integrative Science, The University of Chicago, Chicago, IL, USA.
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2
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Oh J, Kim DK, Ahn SH, Kim HM, Cho H. A dual role of the conserved PEX19 helix in safeguarding peroxisomal membrane proteins. iScience 2024; 27:109537. [PMID: 38585659 PMCID: PMC10995880 DOI: 10.1016/j.isci.2024.109537] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2023] [Revised: 02/13/2024] [Accepted: 03/18/2024] [Indexed: 04/09/2024] Open
Abstract
Accurate localization of membrane proteins is essential for proper cellular functioning and the integrity of cellular membranes. Post-translational targeting of peroxisomal membrane proteins (PMPs) is mediated by the cytosolic chaperone PEX19 and its membrane receptor PEX3. However, the molecular mechanisms underlying PMP targeting are poorly understood. Here, using biochemical and mass spectrometry analysis, we find that a conserved PEX19 helix, αd, is critical to prevent improper exposure of the PEX26 transmembrane domain (TMD) to cytosolic chaperones. Furthermore, the αd helix of PEX19 interacts with the cytosolic domain of the PEX3 receptor, thereby triggering PEX26 release at the correct destination membrane. The peroxisome-deficient PEX3-G138E mutant completely abolishes this secondary interaction, leading to lack of PEX3-induced PEX26 release from PEX19. These findings elucidate a dual molecular mechanism that is essential to membrane protein protection and destination-specific release by a molecular chaperone.
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Affiliation(s)
- Jeonghyun Oh
- Center for Biomolecular and Cellular Structure, Institute for Basic Science (IBS), Daejeon 34126, Republic of Korea
| | - Do Kyung Kim
- Center for Biomolecular and Cellular Structure, Institute for Basic Science (IBS), Daejeon 34126, Republic of Korea
| | - Seung Hae Ahn
- Center for Biomolecular and Cellular Structure, Institute for Basic Science (IBS), Daejeon 34126, Republic of Korea
| | - Ho Min Kim
- Center for Biomolecular and Cellular Structure, Institute for Basic Science (IBS), Daejeon 34126, Republic of Korea
- Graduate School of Medical Science & Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
| | - Hyunju Cho
- Center for Biomolecular and Cellular Structure, Institute for Basic Science (IBS), Daejeon 34126, Republic of Korea
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3
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Muthukumar G, Stevens TA, Inglis AJ, Esantsi TK, Saunders RA, Schulte F, Voorhees RM, Guna A, Weissman JS. Triaging of α-helical proteins to the mitochondrial outer membrane by distinct chaperone machinery based on substrate topology. Mol Cell 2024; 84:1101-1119.e9. [PMID: 38428433 DOI: 10.1016/j.molcel.2024.01.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 12/08/2023] [Accepted: 01/31/2024] [Indexed: 03/03/2024]
Abstract
Mitochondrial outer membrane ⍺-helical proteins play critical roles in mitochondrial-cytoplasmic communication, but the rules governing the targeting and insertion of these biophysically diverse proteins remain unknown. Here, we first defined the complement of required mammalian biogenesis machinery through genome-wide CRISPRi screens using topologically distinct membrane proteins. Systematic analysis of nine identified factors across 21 diverse ⍺-helical substrates reveals that these components are organized into distinct targeting pathways that act on substrates based on their topology. NAC is required for the efficient targeting of polytopic proteins, whereas signal-anchored proteins require TTC1, a cytosolic chaperone that physically engages substrates. Biochemical and mutational studies reveal that TTC1 employs a conserved TPR domain and a hydrophobic groove in its C-terminal domain to support substrate solubilization and insertion into mitochondria. Thus, the targeting of diverse mitochondrial membrane proteins is achieved through topological triaging in the cytosol using principles with similarities to ER membrane protein biogenesis systems.
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Affiliation(s)
- Gayathri Muthukumar
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Taylor A Stevens
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Avenue, Pasadena, CA 91125, USA
| | - Alison J Inglis
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Avenue, Pasadena, CA 91125, USA
| | - Theodore K Esantsi
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Reuben A Saunders
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02142, USA; Tetrad Graduate Program, University of California, San Francisco, San Francisco, CA 94158, USA; Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Fabian Schulte
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
| | - Rebecca M Voorhees
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Avenue, Pasadena, CA 91125, USA
| | - Alina Guna
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA; Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Avenue, Pasadena, CA 91125, USA.
| | - Jonathan S Weissman
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02142, USA; David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02142, USA.
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4
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Wilson EL, Yu Y, Leal NS, Woodward JA, Patikas N, Morris JL, Field SF, Plumbly W, Paupe V, Chowdhury SR, Antrobus R, Lindop GE, Adia YM, Loh SHY, Prudent J, Martins LM, Metzakopian E. Genome-wide CRISPR/Cas9 screen shows that loss of GET4 increases mitochondria-endoplasmic reticulum contact sites and is neuroprotective. Cell Death Dis 2024; 15:203. [PMID: 38467609 PMCID: PMC10928201 DOI: 10.1038/s41419-024-06568-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 02/13/2024] [Accepted: 02/19/2024] [Indexed: 03/13/2024]
Abstract
Organelles form membrane contact sites between each other, allowing for the transfer of molecules and signals. Mitochondria-endoplasmic reticulum (ER) contact sites (MERCS) are cellular subdomains characterized by close apposition of mitochondria and ER membranes. They have been implicated in many diseases, including neurodegenerative, metabolic, and cardiac diseases. Although MERCS have been extensively studied, much remains to be explored. To uncover novel regulators of MERCS, we conducted a genome-wide, flow cytometry-based screen using an engineered MERCS reporter cell line. We found 410 genes whose downregulation promotes MERCS and 230 genes whose downregulation decreases MERCS. From these, 29 genes were selected from each population for arrayed screening and 25 were validated from the high population and 13 from the low population. GET4 and BAG6 were highlighted as the top 2 genes that upon suppression increased MERCS from both the pooled and arrayed screens, and these were subjected to further investigation. Multiple microscopy analyses confirmed that loss of GET4 or BAG6 increased MERCS. GET4 and BAG6 were also observed to interact with the known MERCS proteins, inositol 1,4,5-trisphosphate receptors (IP3R) and glucose-regulated protein 75 (GRP75). In addition, we found that loss of GET4 increased mitochondrial calcium uptake upon ER-Ca2+ release and mitochondrial respiration. Finally, we show that loss of GET4 rescues motor ability, improves lifespan and prevents neurodegeneration in a Drosophila model of Alzheimer's disease (Aβ42Arc). Together, these results suggest that GET4 is involved in decreasing MERCS and that its loss is neuroprotective.
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Affiliation(s)
- Emma L Wilson
- UK Dementia Research Institute, University of Cambridge, Clifford Albutt building, Cambridge biomedical campus, Cambridge, CB2 0AH, UK
- MRC Mitochondrial Biology Unit, University of Cambridge, The Keith Peters building, Cambridge Biomedical Campus, Cambridge, CB2 0XY, UK
- MRC Toxicology Unit, University of Cambridge, Gleeson Building, Tennis Court Road, Cambridge, CB2 1QR, UK
| | - Yizhou Yu
- MRC Toxicology Unit, University of Cambridge, Gleeson Building, Tennis Court Road, Cambridge, CB2 1QR, UK
| | - Nuno S Leal
- MRC Toxicology Unit, University of Cambridge, Gleeson Building, Tennis Court Road, Cambridge, CB2 1QR, UK
| | - James A Woodward
- MRC Toxicology Unit, University of Cambridge, Gleeson Building, Tennis Court Road, Cambridge, CB2 1QR, UK
| | - Nikolaos Patikas
- UK Dementia Research Institute, University of Cambridge, Clifford Albutt building, Cambridge biomedical campus, Cambridge, CB2 0AH, UK
| | - Jordan L Morris
- MRC Mitochondrial Biology Unit, University of Cambridge, The Keith Peters building, Cambridge Biomedical Campus, Cambridge, CB2 0XY, UK
| | - Sarah F Field
- UK Dementia Research Institute, University of Cambridge, Clifford Albutt building, Cambridge biomedical campus, Cambridge, CB2 0AH, UK
| | - William Plumbly
- UK Dementia Research Institute, University of Cambridge, Clifford Albutt building, Cambridge biomedical campus, Cambridge, CB2 0AH, UK
| | - Vincent Paupe
- MRC Mitochondrial Biology Unit, University of Cambridge, The Keith Peters building, Cambridge Biomedical Campus, Cambridge, CB2 0XY, UK
| | - Suvagata R Chowdhury
- MRC Mitochondrial Biology Unit, University of Cambridge, The Keith Peters building, Cambridge Biomedical Campus, Cambridge, CB2 0XY, UK
| | - Robin Antrobus
- Cambridge Institute for Medical Research, University of Cambridge, The Keith Peters Building, Cambridge Biomedical Campus, Hills Rd, Cambridge, CB2 0XY, UK
| | - Georgina E Lindop
- Cambridge Advanced Imaging Centre, University of Cambridge, Anatomy Building, Downing Site, Cambridge, CB2 3DY, UK
| | - Yusuf M Adia
- MRC Toxicology Unit, University of Cambridge, Gleeson Building, Tennis Court Road, Cambridge, CB2 1QR, UK
| | - Samantha H Y Loh
- MRC Toxicology Unit, University of Cambridge, Gleeson Building, Tennis Court Road, Cambridge, CB2 1QR, UK
| | - Julien Prudent
- MRC Mitochondrial Biology Unit, University of Cambridge, The Keith Peters building, Cambridge Biomedical Campus, Cambridge, CB2 0XY, UK.
| | - L Miguel Martins
- MRC Toxicology Unit, University of Cambridge, Gleeson Building, Tennis Court Road, Cambridge, CB2 1QR, UK.
| | - Emmanouil Metzakopian
- UK Dementia Research Institute, University of Cambridge, Clifford Albutt building, Cambridge biomedical campus, Cambridge, CB2 0AH, UK.
- bit bio, The Dorothy Hodgkin Building, Babraham Research Campus, Cambridge, CB22 3FH, UK.
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5
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Cho H, Liu Y, Chung S, Chandrasekar S, Weiss S, Shan SO. Dynamic stability of Sgt2 enables selective and privileged client handover in a chaperone triad. Nat Commun 2024; 15:134. [PMID: 38167697 PMCID: PMC10761869 DOI: 10.1038/s41467-023-44260-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Accepted: 12/06/2023] [Indexed: 01/05/2024] Open
Abstract
Membrane protein biogenesis poses acute challenges to protein homeostasis, and how they are selectively escorted to the target membrane is not well understood. Here we address this question in the guided-entry-of-tail-anchored protein (GET) pathway, in which tail-anchored membrane proteins (TAs) are relayed through an Hsp70-Sgt2-Get3 chaperone triad for targeting to the endoplasmic reticulum. We show that the Hsp70 ATPase cycle and TA substrate drive dimeric Sgt2 from a wide-open conformation to a closed state, in which TAs are protected by both substrate binding domains of Sgt2. Get3 is privileged to receive TA from closed Sgt2, whereas off-pathway chaperones remove TAs from open Sgt2. Sgt2 closing is less favorable with suboptimal GET substrates, which are rejected during or after the Hsp70-to-Sgt2 handover. Our results demonstrate how fine-tuned conformational dynamics in Sgt2 enable hydrophobic TAs to be effectively funneled onto their dedicated targeting factor while also providing a mechanism for substrate selection.
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Affiliation(s)
- Hyunju Cho
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, 91125, USA
- Center for Biomolecular and Cellular Structure, Institute for Basic Science, Daejeon, 34126, Republic of Korea
| | - Yumeng Liu
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, 91125, USA
- Biochemistry and Molecular Biotechnology Department, University of Massachusetts Chan Medical School, Worcester, MA, 01655, USA
| | - SangYoon Chung
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Sowmya Chandrasekar
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Shimon Weiss
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA, 90095, USA
- Department of Physics, Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, 52900, Israel
| | - Shu-Ou Shan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, 91125, USA.
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6
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Muthukumar G, Stevens TA, Inglis AJ, Esantsi TK, Saunders RA, Schulte F, Voorhees RM, Guna A, Weissman JS. Triaging of α-helical proteins to the mitochondrial outer membrane by distinct chaperone machinery based on substrate topology. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.16.553624. [PMID: 37645817 PMCID: PMC10462106 DOI: 10.1101/2023.08.16.553624] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Mitochondrial outer membrane α-helical proteins play critical roles in mitochondrial-cytoplasmic communication, but the rules governing the targeting and insertion of these biophysically diverse substrates remain unknown. Here, we first defined the complement of required mammalian biogenesis machinery through genome-wide CRISPRi screens using topologically distinct membrane proteins. Systematic analysis of nine identified factors across 21 diverse α-helical substrates reveals that these components are organized into distinct targeting pathways which act on substrates based on their topology. NAC is required for efficient targeting of polytopic proteins whereas signal-anchored proteins require TTC1, a novel cytosolic chaperone which physically engages substrates. Biochemical and mutational studies reveal that TTC1 employs a conserved TPR domain and a hydrophobic groove in its C-terminal domain to support substrate solubilization and insertion into mitochondria. Thus, targeting of diverse mitochondrial membrane proteins is achieved through topological triaging in the cytosol using principles with similarities to ER membrane protein biogenesis systems.
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Affiliation(s)
- Gayathri Muthukumar
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Taylor A. Stevens
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Avenue, Pasadena, CA 91125, USA
| | - Alison J. Inglis
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Avenue, Pasadena, CA 91125, USA
| | - Theodore K. Esantsi
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Reuben A. Saunders
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, USA
- Tetrad Graduate Program, University of California, San Francisco, San Francisco, CA 94158, USA
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Fabian Schulte
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
| | - Rebecca M. Voorhees
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Avenue, Pasadena, CA 91125, USA
| | - Alina Guna
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Avenue, Pasadena, CA 91125, USA
| | - Jonathan S. Weissman
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, USA
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute Technology, Cambridge 02142, MA
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7
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Gupta A, Lu C, Wang F, Chou T, Shan S. An ankyrin repeat chaperone targets toxic oligomers during amyloidogenesis. Protein Sci 2023; 32:e4728. [PMID: 37433015 PMCID: PMC10367600 DOI: 10.1002/pro.4728] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 05/18/2023] [Accepted: 07/10/2023] [Indexed: 07/13/2023]
Abstract
Numerous age-linked diseases are rooted in protein misfolding; this has motivated the development of small molecules and therapeutic antibodies that target the aggregation of disease-linked proteins. Here we explore another approach: molecular chaperones with engineerable protein scaffolds such as the ankyrin repeat domain (ARD). We tested the ability of cpSRP43, a small, robust, ATP- and cofactor-independent plant chaperone built from an ARD, to antagonize disease-linked protein aggregation. cpSRP43 delays the aggregation of multiple proteins including the amyloid beta peptide (Aβ) associated with Alzheimer's disease and α-synuclein associated with Parkinson's disease. Kinetic modeling and biochemical analyses show that cpSRP43 targets early oligomers during Aβ aggregation, preventing their transition to a self-propagating nucleus on the fibril surface. Accordingly, cpSRP43 rescued neuronal cells from the toxicity of extracellular Aβ42 aggregates. The substrate-binding domain of cpSRP43, composed primarily of the ARD, is necessary and sufficient to prevent Aβ42 aggregation and protect cells against Aβ42 toxicity. This work provides an example in which an ARD chaperone non-native to mammalian cells harbors anti-amyloidal activity, which may be exploited for bioengineering.
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Affiliation(s)
- Arpit Gupta
- Division of Chemistry and Chemical EngineeringCalifornia Institute of TechnologyPasadenaCaliforniaUSA
| | - Chuqi Lu
- Division of Chemistry and Chemical EngineeringCalifornia Institute of TechnologyPasadenaCaliforniaUSA
| | - Feng Wang
- Division of Biology and Biological EngineeringCalifornia Institute of TechnologyPasadenaCaliforniaUSA
| | - Tsui‐Fen Chou
- Division of Biology and Biological EngineeringCalifornia Institute of TechnologyPasadenaCaliforniaUSA
| | - Shu‐ou Shan
- Division of Chemistry and Chemical EngineeringCalifornia Institute of TechnologyPasadenaCaliforniaUSA
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8
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Josefson R, Kumar N, Hao X, Liu B, Nyström T. The GET pathway is a major bottleneck for maintaining proteostasis in Saccharomyces cerevisiae. Sci Rep 2023; 13:9285. [PMID: 37286562 DOI: 10.1038/s41598-023-35666-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Accepted: 05/18/2023] [Indexed: 06/09/2023] Open
Abstract
A hallmark of aging in a variety of organisms is a breakdown of proteostasis and an ensuing accumulation of protein aggregates and inclusions. However, it is not clear if the proteostasis network suffers from a uniform breakdown during aging or if some distinct components act as bottlenecks especially sensitive to functional decline. Here, we report on a genome-wide, unbiased, screen for single genes in young cells of budding yeast required to keep the proteome aggregate-free under non-stress conditions as a means to identify potential proteostasis bottlenecks. We found that the GET pathway, required for the insertion of tail-anchored (TA) membrane proteins in the endoplasmic reticulum, is such a bottleneck as single mutations in either GET3, GET2 or GET1 caused accumulation of cytosolic Hsp104- and mitochondria-associated aggregates in nearly all cells when growing at 30 °C (non-stress condition). Further, results generated by a second screen identifying proteins aggregating in GET mutants and analyzing the behavior of cytosolic reporters of misfolding, suggest that there is a general collapse in proteostasis in GET mutants that affects other proteins than TA proteins.
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Affiliation(s)
- Rebecca Josefson
- Department of Microbiology and Immunology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Navinder Kumar
- Department of Microbiology and Immunology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Xinxin Hao
- Department of Microbiology and Immunology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Beidong Liu
- Department of Chemistry and Molecular Biology, Faculty of Science, University of Gothenburg, Gothenburg, Sweden
| | - Thomas Nyström
- Department of Microbiology and Immunology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
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9
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Shan SO. Role of Hsp70 in Post-Translational Protein Targeting: Tail-Anchored Membrane Proteins and Beyond. Int J Mol Sci 2023; 24:1170. [PMID: 36674686 PMCID: PMC9866221 DOI: 10.3390/ijms24021170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 01/02/2023] [Accepted: 01/04/2023] [Indexed: 01/11/2023] Open
Abstract
The Hsp70 family of molecular chaperones acts as a central 'hub' in the cell that interacts with numerous newly synthesized proteins to assist in their biogenesis. Apart from its central and well-established role in facilitating protein folding, Hsp70s also act as key decision points in the cellular chaperone network that direct client proteins to distinct biogenesis and quality control pathways. In this paper, we review accumulating data that illustrate a new branch in the Hsp70 network: the post-translational targeting of nascent membrane and organellar proteins to diverse cellular organelles. Work in multiple pathways suggests that Hsp70, via its ability to interact with components of protein targeting and translocation machineries, can initiate elaborate substrate relays in a sophisticated cascade of chaperones, cochaperones, and receptor proteins, and thus provide a mechanism to safeguard and deliver nascent membrane proteins to the correct cellular membrane. We discuss the mechanistic principles gleaned from better-studied Hsp70-dependent targeting pathways and outline the observations and outstanding questions in less well-studied systems.
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Affiliation(s)
- Shu-Ou Shan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
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10
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Fry MY, Najdrová V, Maggiolo AO, Saladi SM, Doležal P, Clemons WM. Structurally derived universal mechanism for the catalytic cycle of the tail-anchored targeting factor Get3. Nat Struct Mol Biol 2022; 29:820-830. [DOI: 10.1038/s41594-022-00798-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 05/26/2022] [Indexed: 11/09/2022]
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11
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Smertina E, Carroll AJ, Boileau J, Emmott E, Jenckel M, Vohra H, Rolland V, Hands P, Hayashi J, Neave MJ, Liu JW, Hall RN, Strive T, Frese M. Lagovirus Non-structural Protein p23: A Putative Viroporin That Interacts With Heat Shock Proteins and Uses a Disulfide Bond for Dimerization. Front Microbiol 2022; 13:923256. [PMID: 35923397 PMCID: PMC9340658 DOI: 10.3389/fmicb.2022.923256] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Accepted: 06/16/2022] [Indexed: 12/03/2022] Open
Abstract
The exact function(s) of the lagovirus non-structural protein p23 is unknown as robust cell culture systems for the Rabbit haemorrhagic disease virus (RHDV) and other lagoviruses have not been established. Instead, a range of in vitro and in silico models have been used to study p23, revealing that p23 oligomerizes, accumulates in the cytoplasm, and possesses a conserved C-terminal region with two amphipathic helices. Furthermore, the positional homologs of p23 in other caliciviruses have been shown to possess viroporin activity. Here, we report on the mechanistic details of p23 oligomerization. Site-directed mutagenesis revealed the importance of an N-terminal cysteine for dimerization. Furthermore, we identified cellular interactors of p23 using stable isotope labeling with amino acids in cell culture (SILAC)-based proteomics; heat shock proteins Hsp70 and 110 interact with p23 in transfected cells, suggesting that they ‘chaperone’ p23 proteins before their integration into cellular membranes. We investigated changes to the global transcriptome and proteome that occurred in infected rabbit liver tissue and observed changes to the misfolded protein response, calcium signaling, and the regulation of the endoplasmic reticulum (ER) network. Finally, flow cytometry studies indicate slightly elevated calcium concentrations in the cytoplasm of p23-transfected cells. Taken together, accumulating evidence suggests that p23 is a viroporin that might form calcium-conducting channels in the ER membranes.
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Affiliation(s)
- Elena Smertina
- Health and Biosecurity, Commonwealth Scientific and Industrial Research Organisation, Canberra, ACT, Australia
- Faculty of Science and Technology, University of Canberra, Canberra, ACT, Australia
- Centre for Invasive Species Solutions, Canberra, ACT, Australia
| | - Adam J. Carroll
- RSB/RSC Joint Mass Spectrometry Facility, Research School of Chemistry, Australian National University, Acton, ACT, Australia
| | - Joseph Boileau
- RSB/RSC Joint Mass Spectrometry Facility, Research School of Chemistry, Australian National University, Acton, ACT, Australia
| | - Edward Emmott
- Centre for Proteome Research, Department of Biochemistry & Systems Biology, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Maria Jenckel
- Health and Biosecurity, Commonwealth Scientific and Industrial Research Organisation, Canberra, ACT, Australia
| | - Harpreet Vohra
- Imaging and Cytometry Facility, John Curtin School of Medical Research, Acton, ACT, Australia
| | - Vivien Rolland
- Agriculture and Food, Commonwealth Scientific and Industrial Research Organisation, Canberra, ACT, Australia
| | - Philip Hands
- Agriculture and Food, Commonwealth Scientific and Industrial Research Organisation, Canberra, ACT, Australia
| | - Junna Hayashi
- Research School of Chemistry, Australian National University, Acton, ACT, Australia
| | - Matthew J. Neave
- Australian Centre for Disease Preparedness, Commonwealth Scientific and Industrial Research Organisation, Geelong, VIC, Australia
| | - Jian-Wei Liu
- Land and Water, Commonwealth Scientific and Industrial Research Organisation, Canberra, ACT, Australia
| | - Robyn N. Hall
- Health and Biosecurity, Commonwealth Scientific and Industrial Research Organisation, Canberra, ACT, Australia
- Centre for Invasive Species Solutions, Canberra, ACT, Australia
| | - Tanja Strive
- Health and Biosecurity, Commonwealth Scientific and Industrial Research Organisation, Canberra, ACT, Australia
- Centre for Invasive Species Solutions, Canberra, ACT, Australia
| | - Michael Frese
- Health and Biosecurity, Commonwealth Scientific and Industrial Research Organisation, Canberra, ACT, Australia
- Faculty of Science and Technology, University of Canberra, Canberra, ACT, Australia
- *Correspondence: Michael Frese,
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12
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Pool MR. Targeting of Proteins for Translocation at the Endoplasmic Reticulum. Int J Mol Sci 2022; 23:ijms23073773. [PMID: 35409131 PMCID: PMC8998515 DOI: 10.3390/ijms23073773] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Revised: 03/24/2022] [Accepted: 03/24/2022] [Indexed: 12/12/2022] Open
Abstract
The endoplasmic reticulum represents the gateway to the secretory pathway. Here, proteins destined for secretion, as well as soluble and membrane proteins that reside in the endomembrane system and plasma membrane, are triaged from proteins that will remain in the cytosol or be targeted to other cellular organelles. This process requires the faithful recognition of specific targeting signals and subsequent delivery mechanisms to then target them to the translocases present at the ER membrane, which can either translocate them into the ER lumen or insert them into the lipid bilayer. This review focuses on the current understanding of the first step in this process representing the targeting phase. Targeting is typically mediated by cleavable N-terminal hydrophobic signal sequences or internal membrane anchor sequences; these can either be captured co-translationally at the ribosome or recognised post-translationally and then delivered to the ER translocases. Location and features of the targeting sequence dictate which of several overlapping targeting pathway substrates will be used. Mutations in the targeting machinery or targeting signals can be linked to diseases.
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Affiliation(s)
- Martin R Pool
- School of Biological Science, Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PL, UK
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13
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Abstract
The endoplasmic reticulum (ER) is the site of membrane protein insertion, folding, and assembly in eukaryotes. Over the past few years, a combination of genetic and biochemical studies have implicated an abundant factor termed the ER membrane protein complex (EMC) in several aspects of membrane protein biogenesis. This large nine-protein complex is built around a deeply conserved core formed by the EMC3-EMC6 subcomplex. EMC3 belongs to the universally conserved Oxa1 superfamily of membrane protein transporters, whereas EMC6 is an ancient, widely conserved obligate partner. EMC has an established role in the insertion of transmembrane domains (TMDs) and less understood roles during the later steps of membrane protein folding and assembly. Several recent structures suggest hypotheses about the mechanism(s) of TMD insertion by EMC, with various biochemical and proteomics studies beginning to reveal the range of EMC's membrane protein substrates. Expected final online publication date for the Annual Review of Biochemistry, Volume 91 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Ramanujan S Hegde
- Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom;
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14
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Hegde RS, Keenan RJ. The mechanisms of integral membrane protein biogenesis. Nat Rev Mol Cell Biol 2022; 23:107-124. [PMID: 34556847 DOI: 10.1038/s41580-021-00413-2] [Citation(s) in RCA: 76] [Impact Index Per Article: 38.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/06/2021] [Indexed: 02/08/2023]
Abstract
Roughly one quarter of all genes code for integral membrane proteins that are inserted into the plasma membrane of prokaryotes or the endoplasmic reticulum membrane of eukaryotes. Multiple pathways are used for the targeting and insertion of membrane proteins on the basis of their topological and biophysical characteristics. Multipass membrane proteins span the membrane multiple times and face the additional challenges of intramembrane folding. In many cases, integral membrane proteins require assembly with other proteins to form multi-subunit membrane protein complexes. Recent biochemical and structural analyses have provided considerable clarity regarding the molecular basis of membrane protein targeting and insertion, with tantalizing new insights into the poorly understood processes of multipass membrane protein biogenesis and multi-subunit protein complex assembly.
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Affiliation(s)
- Ramanujan S Hegde
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, UK.
| | - Robert J Keenan
- Gordon Center for Integrative Science, The University of Chicago, Chicago, IL, USA.
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15
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Tirincsi A, Sicking M, Hadzibeganovic D, Haßdenteufel S, Lang S. The Molecular Biodiversity of Protein Targeting and Protein Transport Related to the Endoplasmic Reticulum. Int J Mol Sci 2021; 23:143. [PMID: 35008565 PMCID: PMC8745461 DOI: 10.3390/ijms23010143] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 12/19/2021] [Accepted: 12/20/2021] [Indexed: 12/15/2022] Open
Abstract
Looking at the variety of the thousands of different polypeptides that have been focused on in the research on the endoplasmic reticulum from the last five decades taught us one humble lesson: no one size fits all. Cells use an impressive array of components to enable the safe transport of protein cargo from the cytosolic ribosomes to the endoplasmic reticulum. Safety during the transit is warranted by the interplay of cytosolic chaperones, membrane receptors, and protein translocases that together form functional networks and serve as protein targeting and translocation routes. While two targeting routes to the endoplasmic reticulum, SRP (signal recognition particle) and GET (guided entry of tail-anchored proteins), prefer targeting determinants at the N- and C-terminus of the cargo polypeptide, respectively, the recently discovered SND (SRP-independent) route seems to preferentially cater for cargos with non-generic targeting signals that are less hydrophobic or more distant from the termini. With an emphasis on targeting routes and protein translocases, we will discuss those functional networks that drive efficient protein topogenesis and shed light on their redundant and dynamic nature in health and disease.
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Affiliation(s)
- Andrea Tirincsi
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (A.T.); (M.S.); (D.H.)
| | - Mark Sicking
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (A.T.); (M.S.); (D.H.)
| | - Drazena Hadzibeganovic
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (A.T.); (M.S.); (D.H.)
| | - Sarah Haßdenteufel
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Sven Lang
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (A.T.); (M.S.); (D.H.)
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16
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Mehlhorn DG, Asseck LY, Grefen C. Looking for a safe haven: tail-anchored proteins and their membrane insertion pathways. PLANT PHYSIOLOGY 2021; 187:1916-1928. [PMID: 35235667 PMCID: PMC8644595 DOI: 10.1093/plphys/kiab298] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 06/05/2021] [Indexed: 06/14/2023]
Abstract
Insertion of membrane proteins into the lipid bilayer is a crucial step during their biosynthesis. Eukaryotic cells face many challenges in directing these proteins to their predestined target membrane. The hydrophobic signal peptide or transmembrane domain (TMD) of the nascent protein must be shielded from the aqueous cytosol and its target membrane identified followed by transport and insertion. Components that evolved to deal with each of these challenging steps range from chaperones to receptors, insertases, and sophisticated translocation complexes. One prominent translocation pathway for most proteins is the signal recognition particle (SRP)-dependent pathway which mediates co-translational translocation of proteins across or into the endoplasmic reticulum (ER) membrane. This textbook example of protein insertion is stretched to its limits when faced with secretory or membrane proteins that lack an amino-terminal signal sequence or TMD. Particularly, a large group of so-called tail-anchored (TA) proteins that harbor a single carboxy-terminal TMD require an alternative, post-translational insertion route into the ER membrane. In this review, we summarize the current research in TA protein insertion with a special focus on plants, address challenges, and highlight future research avenues.
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Affiliation(s)
- Dietmar G Mehlhorn
- Faculty of Biology and Biotechnology, Molecular and Cellular Botany, University of Bochum, Universitätsstraße 150, 44780 Bochum, Germany
| | - Lisa Y Asseck
- Faculty of Biology and Biotechnology, Molecular and Cellular Botany, University of Bochum, Universitätsstraße 150, 44780 Bochum, Germany
| | - Christopher Grefen
- Faculty of Biology and Biotechnology, Molecular and Cellular Botany, University of Bochum, Universitätsstraße 150, 44780 Bochum, Germany
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17
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Kumar T, Maitra S, Rahman A, Bhattacharjee S. A conserved guided entry of tail-anchored pathway is involved in the trafficking of a subset of membrane proteins in Plasmodium falciparum. PLoS Pathog 2021; 17:e1009595. [PMID: 34780541 PMCID: PMC8629386 DOI: 10.1371/journal.ppat.1009595] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 11/29/2021] [Accepted: 10/19/2021] [Indexed: 01/22/2023] Open
Abstract
Tail-anchored (TA) proteins are defined by the absence of N-terminus signal sequence and the presence of a single transmembrane domain (TMD) proximal to their C-terminus. They play fundamental roles in cellular processes including vesicular trafficking, protein translocation and quality control. Some of the TA proteins are post-translationally integrated by the Guided Entry of TA (GET) pathway to the cellular membranes; with their N-terminus oriented towards the cytosol and C-terminus facing the organellar lumen. The TA repertoire and the GET machinery have been extensively characterized in the yeast and mammalian systems, however, they remain elusive in the human malaria parasite Plasmodium falciparum. In this study, we bioinformatically predicted a total of 63 TA proteins in the P. falciparum proteome and revealed the association of a subset with the P. falciparum homolog of Get3 (PfGet3). In addition, our proximity labelling studies either definitively identified or shortlisted the other eligible GET constituents, and our in vitro association studies validated associations between PfGet3 and the corresponding homologs of Get4 and Get2 in P. falciparum. Collectively, this study reveals the presence of proteins with hallmark TA signatures and the involvement of evolutionary conserved GET trafficking pathway for their targeted delivery within the parasite. Tail-anchored (TA) membrane proteins are known to play essential cellular functions in the eukaryotes. These proteins are trafficked to their respective destinations by post-translational translocation pathways that are evolutionarily conserved from yeast to human. However, they remain unidentified in the malaria parasite Plasmodium falciparum. We have used bioinformatic prediction algorithms in conjunction with functional validation studies to identify the candidate TA repertoire and some of the homologs of the trafficking machinery in P. falciparum. Initially, we predicted the presence of 63 putative TA proteins localized to distinct compartments within this parasite, including a few confirmed TA homologs in other eukaryotic systems. We then identified and characterized PfGet3 as a central component in the Guided-Entry of TA (GET) translocation machinery, and our bacterial co-expression and pulldown assays with two selected recombinant TA proteins, PfBOS1 and PfUSE1, showed co-association with PfGet3. We also identified PfGet2 and PfGet4 as the other two components of the GET machinery in P. falciparum using proximity biotinylation followed by mass spectrometry. Interestingly, we also found six TA proteins in the parasite enriched in this fraction. We further validated the direct interactions between a few TA candidates, PfGet4 and PfGet2 with PfGet3 using recombinant-based pulldown studies. In conclusion, this study classified a subset of membrane proteins with the TA nomenclature and implicated a previously unidentified GET pathway for their translocation in this apicomplexan parasite.
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Affiliation(s)
- Tarkeshwar Kumar
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, India
| | - Satarupa Maitra
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, India
| | - Abdur Rahman
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, India
| | - Souvik Bhattacharjee
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, India
- * E-mail:
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18
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Chio US, Liu Y, Chung S, Shim WJ, Chandrasekar S, Weiss S, Shan SO. Subunit cooperation in the Get1/2 receptor promotes tail-anchored membrane protein insertion. J Cell Biol 2021; 220:212681. [PMID: 34614151 PMCID: PMC8530227 DOI: 10.1083/jcb.202103079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 08/03/2021] [Accepted: 08/19/2021] [Indexed: 11/29/2022] Open
Abstract
The guided entry of tail-anchored protein (GET) pathway, in which the Get3 ATPase delivers an essential class of tail-anchored membrane proteins (TAs) to the Get1/2 receptor at the endoplasmic reticulum, provides a conserved mechanism for TA biogenesis in eukaryotic cells. The membrane-associated events of this pathway remain poorly understood. Here we show that complex assembly between the cytosolic domains (CDs) of Get1 and Get2 strongly enhances the affinity of the individual subunits for Get3•TA, thus enabling efficient capture of the targeting complex. In addition to the known role of Get1CD in remodeling Get3 conformation, two molecular recognition features (MoRFs) in Get2CD induce Get3 opening, and both subunits are required for optimal TA release from Get3. Mutation of the MoRFs attenuates TA insertion into the ER in vivo. Our results demonstrate extensive cooperation between the Get1/2 receptor subunits in the capture and remodeling of the targeting complex, and emphasize the role of MoRFs in receptor function during membrane protein biogenesis.
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Affiliation(s)
- Un Seng Chio
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA
| | - Yumeng Liu
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA
| | - SangYoon Chung
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA
| | - Woo Jun Shim
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA
| | - Sowmya Chandrasekar
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA
| | - Shimon Weiss
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA.,Department of Physics, Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, Israel
| | - Shu-Ou Shan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA
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19
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Fry MY, Saladi SM, Cunha A, Clemons WM. Sequence-based features that are determinant for tail-anchored membrane protein sorting in eukaryotes. Traffic 2021; 22:306-318. [PMID: 34288289 PMCID: PMC8380732 DOI: 10.1111/tra.12809] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 07/15/2021] [Accepted: 07/18/2021] [Indexed: 11/29/2022]
Abstract
The correct targeting and insertion of tail-anchored (TA) integral membrane proteins is critical for cellular homeostasis. TA proteins are defined by a hydrophobic transmembrane domain (TMD) at their C-terminus and are targeted to either the ER or mitochondria. Derived from experimental measurements of a few TA proteins, there has been little examination of the TMD features that determine localization. As a result, the localization of many TA proteins are misclassified by the simple heuristic of overall hydrophobicity. Because ER-directed TMDs favor arrangement of hydrophobic residues to one side, we sought to explore the role of geometric hydrophobic properties. By curating TA proteins with experimentally determined localizations and assessing hypotheses for recognition, we bioinformatically and experimentally verify that a hydrophobic face is the most accurate singular metric for separating ER and mitochondria-destined yeast TA proteins. A metric focusing on an 11 residue segment of the TMD performs well when classifying human TA proteins. The most inclusive predictor uses both hydrophobicity and C-terminal charge in tandem. This work provides context for previous observations and opens the door for more detailed mechanistic experiments to determine the molecular factors driving this recognition.
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Affiliation(s)
- Michelle Y. Fry
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, USA
| | - Shyam M. Saladi
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, USA
| | - Alexandre Cunha
- Division of Biology and Biological Engineering, Center for Advanced Methods in Biological Image Analysis, Beckman Institute, Pasadena, California, USA
| | - William M. Clemons
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, USA
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20
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Farkas Á, Bohnsack KE. Capture and delivery of tail-anchored proteins to the endoplasmic reticulum. J Cell Biol 2021; 220:212470. [PMID: 34264263 PMCID: PMC8287540 DOI: 10.1083/jcb.202105004] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2021] [Revised: 06/20/2021] [Accepted: 06/22/2021] [Indexed: 11/22/2022] Open
Abstract
Tail-anchored (TA) proteins fulfill diverse cellular functions within different organellar membranes. Their characteristic C-terminal transmembrane segment renders TA proteins inherently prone to aggregation and necessitates their posttranslational targeting. The guided entry of TA proteins (GET in yeast)/transmembrane recognition complex (TRC in humans) pathway represents a major route for TA proteins to the endoplasmic reticulum (ER). Here, we review important new insights into the capture of nascent TA proteins at the ribosome by the GET pathway pretargeting complex and the mechanism of their delivery into the ER membrane by the GET receptor insertase. Interestingly, several alternative routes by which TA proteins can be targeted to the ER have emerged, raising intriguing questions about how selectivity is achieved during TA protein capture. Furthermore, mistargeting of TA proteins is a fundamental cellular problem, and we discuss the recently discovered quality control machineries in the ER and outer mitochondrial membrane for displacing mislocalized TA proteins.
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Affiliation(s)
- Ákos Farkas
- Department of Molecular Biology, University Medical Center Göttingen, Göttingen, Germany
| | - Katherine E Bohnsack
- Department of Molecular Biology, University Medical Center Göttingen, Göttingen, Germany
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21
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Dederer V, Lemberg MK. Transmembrane dislocases: a second chance for protein targeting. Trends Cell Biol 2021; 31:898-911. [PMID: 34147299 DOI: 10.1016/j.tcb.2021.05.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 05/11/2021] [Accepted: 05/14/2021] [Indexed: 12/31/2022]
Abstract
Precise distribution of proteins is essential to sustain the viability of cells. A complex network of protein synthesis and targeting factors cooperate with protein quality control systems to ensure protein homeostasis. Defective proteins are inevitably degraded by the ubiquitin-proteasome system and lysosomes. However, due to overlapping targeting information and limited targeting fidelity, certain proteins become mislocalized. In this review, we present the idea that transmembrane dislocases recognize and remove mislocalized membrane proteins from cellular organelles. This enables other targeting attempts and prevents degradation of mislocalized but otherwise functional proteins. These transmembrane dislocases can be found in the outer mitochondrial membrane (OMM) and endoplasmic reticulum (ER). We highlight common principles regarding client recognition and outline open questions in our understanding of transmembrane dislocases.
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Affiliation(s)
- Verena Dederer
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany; Current address: Institute for Pharmaceutical Biology and Buchmann Institute for Molecular Life Science, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany
| | - Marius K Lemberg
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany; Center for Biochemistry, Medical Faculty, University of Cologne, 50931 Cologne, Germany.
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22
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Quel NG, Fernando de C Rodrigues L, Aragão AZB, Pinheiro GMS, Camacho RP, Souto DEP, Kubota LT, Barbosa LRS, Ramos CHI. Insights into the structure and function of the C-terminus of SGTs (small glutamine-rich TPR-containing proteins): A study of the Aedes aegypti homolog. Biochimie 2021; 187:131-143. [PMID: 34082040 DOI: 10.1016/j.biochi.2021.05.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 05/24/2021] [Accepted: 05/26/2021] [Indexed: 10/21/2022]
Abstract
SGTs (small glutamine-rich TPR-containing proteins) are dimeric proteins that belong to the class of co-chaperones characterized by the presence of TPR domains (containing tetratricopeptide repeats). Human (SGTA) and yeast (Sgt2) SGTs are characterized by three distinct domains: an N-terminal dimerization domain, a central TPR-domain important for binding to other proteins (chaperones included) and a C-terminal domain involved in hydrophobic interactions. Both these SGTs are involved in the cellular PQC (protein quality control) system, as they interact with chaperones and have functions that aid stress recovery. However, there are differences between them, such as structural features and binding specificities, that could be better understood if other orthologous proteins were studied. Therefore, we produced and characterized a putative SGT protein, designated AaSGT, from the mosquito Aedes aegypti, which is a vector of several diseases, such as dengue and Zika. The protein was produced as a folded dimer which was stable up to 40 °C and was capable of binding to AaHsp90 and fully protecting a model protein, α-synuclein, from aggregation. The conformation of AaSGT was investigated by biophysical tools and small angle X-ray scattering, which showed that the protein had an elongated conformation and that its C-terminal domain was mainly disordered. The results with a C-terminal deletion mutant supported these observations. Altogether, these results are consistent with those from other functional SGT proteins and add to the understanding of the PQC system in Aedes aegypti, an important aim that may help to develop inhibitory strategies against this vector of neglected diseases.
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Affiliation(s)
- Natália G Quel
- Institute of Chemistry, University of Campinas UNICAMP, Campinas SP, 13083-970 Brazil; National Institute of Science & Technology of Structural Biology and Bioimage (INCTBEB), Brazil
| | | | - Annelize Z B Aragão
- Institute of Chemistry, University of Campinas UNICAMP, Campinas SP, 13083-970 Brazil
| | - Glaucia M S Pinheiro
- Institute of Chemistry, University of Campinas UNICAMP, Campinas SP, 13083-970 Brazil
| | - Rafael P Camacho
- Institute of Chemistry, University of Campinas UNICAMP, Campinas SP, 13083-970 Brazil
| | - Denio E P Souto
- Department of Chemistry, Federal University of Paraná-UFPR, Curitiba PR, 81530-900, Brazil
| | - Lauro T Kubota
- Institute of Chemistry, University of Campinas UNICAMP, Campinas SP, 13083-970 Brazil; National Institute of Science & Technology of Bioanalytics (INCTBio), Brazil
| | - Leandro R S Barbosa
- Institute of Physics, University of São Paulo, São Paulo SP, 05508-090 Brazil; Brazilian Synchrotron Light Laboratory (LNLS), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
| | - Carlos H I Ramos
- Institute of Chemistry, University of Campinas UNICAMP, Campinas SP, 13083-970 Brazil; National Institute of Science & Technology of Structural Biology and Bioimage (INCTBEB), Brazil.
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23
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Raj D, Billing O, Podraza-Farhanieh A, Kraish B, Hemmingsson O, Kao G, Naredi P. Alternative redox forms of ASNA-1 separate insulin signaling from tail-anchored protein targeting and cisplatin resistance in C. elegans. Sci Rep 2021; 11:8678. [PMID: 33883621 PMCID: PMC8060345 DOI: 10.1038/s41598-021-88085-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 04/07/2021] [Indexed: 02/02/2023] Open
Abstract
Cisplatin is a frontline cancer therapeutic, but intrinsic or acquired resistance is common. We previously showed that cisplatin sensitivity can be achieved by inactivation of ASNA-1/TRC40 in mammalian cancer cells and in Caenorhabditis elegans. ASNA-1 has two more conserved functions: in promoting tail-anchored protein (TAP) targeting to the endoplasmic reticulum membrane and in promoting insulin secretion. However, the relation between its different functions has remained unknown. Here, we show that ASNA-1 exists in two redox states that promote TAP-targeting and insulin secretion separately. The reduced state is the one required for cisplatin resistance: an ASNA-1 point mutant, in which the protein preferentially was found in the oxidized state, was sensitive to cisplatin and defective for TAP targeting but had no insulin secretion defect. The same was true for mutants in wrb-1, which we identify as the C. elegans homolog of WRB, the ASNA1/TRC40 receptor. Finally, we uncover a previously unknown action of cisplatin induced reactive oxygen species: cisplatin induced ROS drives ASNA-1 into the oxidized form, and selectively prevents an ASNA-1-dependent TAP substrate from reaching the endoplasmic reticulum. Our work suggests that ASNA-1 acts as a redox-sensitive target for cisplatin cytotoxicity and that cisplatin resistance is likely mediated by ASNA-1-dependent TAP substrates. Treatments that promote an oxidizing tumor environment should be explored as possible means to combat cisplatin resistance.
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Affiliation(s)
- Dorota Raj
- Department of Surgery, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, 413 45, Gothenburg, Sweden
| | - Ola Billing
- Department of Surgical and Perioperative Sciences, Surgery, Umeå University, 901 85, Umeå, Sweden
| | - Agnieszka Podraza-Farhanieh
- Department of Surgery, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, 413 45, Gothenburg, Sweden
| | - Bashar Kraish
- Department of Surgery, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, 413 45, Gothenburg, Sweden
| | - Oskar Hemmingsson
- Department of Surgical and Perioperative Sciences, Surgery, Umeå University, 901 85, Umeå, Sweden
| | - Gautam Kao
- Department of Surgery, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, 413 45, Gothenburg, Sweden.
| | - Peter Naredi
- Department of Surgery, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, 413 45, Gothenburg, Sweden.
- Department of Surgery, Sahlgrenska University Hospital, 413 45, Gothenburg, Sweden.
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24
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Fry MY, Saladi SM, Clemons WM. The STI1-domain is a flexible alpha-helical fold with a hydrophobic groove. Protein Sci 2021; 30:882-898. [PMID: 33620121 PMCID: PMC7980504 DOI: 10.1002/pro.4049] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 02/17/2021] [Accepted: 02/18/2021] [Indexed: 01/05/2023]
Abstract
STI1-domains are present in a variety of co-chaperone proteins and are required for the transfer of hydrophobic clients in various cellular processes. The domains were first identified in the yeast Sti1 protein where they were referred to as DP1 and DP2. Based on hidden Markov model searches, this domain had previously been found in other proteins including the mammalian co-chaperone SGTA, the DNA damage response protein Rad23, and the chloroplast import protein Tic40. Here, we refine the domain definition and carry out structure-based sequence alignment of STI1-domains showing conservation of five amphipathic helices. Upon examinations of these identified domains, we identify a preceding helix 0 and unifying sequence properties, determine new molecular models, and recognize that STI1-domains nearly always occur in pairs. The similarity at the sequence, structure, and molecular levels likely supports a unified functional role.
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Affiliation(s)
- Michelle Y. Fry
- Division of Chemistry and Chemical EngineeringCalifornia Institute of TechnologyPasadenaCaliforniaUSA
| | - Shyam M. Saladi
- Division of Chemistry and Chemical EngineeringCalifornia Institute of TechnologyPasadenaCaliforniaUSA
| | - William M. Clemons
- Division of Chemistry and Chemical EngineeringCalifornia Institute of TechnologyPasadenaCaliforniaUSA
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25
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Cho H, Shim WJ, Liu Y, Shan SO. J-domain proteins promote client relay from Hsp70 during tail-anchored membrane protein targeting. J Biol Chem 2021; 296:100546. [PMID: 33741343 PMCID: PMC8054193 DOI: 10.1016/j.jbc.2021.100546] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 02/22/2021] [Accepted: 03/15/2021] [Indexed: 01/17/2023] Open
Abstract
J-domain proteins (JDPs) play essential roles in Hsp70 function by assisting Hsp70 in client trapping and regulating the Hsp70 ATPase cycle. Here, we report that JDPs can further enhance the targeting competence of Hsp70-bound client proteins during tail-anchored protein (TA) biogenesis. In the guided-entry-of-tail-anchored protein pathway in yeast, nascent TAs are captured by cytosolic Hsp70 and sequentially relayed to downstream chaperones, Sgt2 and Get3, for delivery to the ER. We found that two JDPs, Ydj1 and Sis1, function in parallel to support TA targeting to the ER in vivo. Biochemical analyses showed that, while Ydj1 and Sis1 differ in their ability to assist Hsp70 in TA trapping, both JDPs enhance the transfer of Hsp70-bound TAs to Sgt2. The ability of the JDPs to regulate the ATPase cycle of Hsp70 is essential for enhancing the transfer competence of Hsp70-bound TAs in vitro and for supporting TA insertion in vivo. These results demonstrate a role of JDPs in regulating the conformation of Hsp70-bound clients during membrane protein biogenesis.
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Affiliation(s)
- Hyunju Cho
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, USA
| | - Woo Jun Shim
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, USA
| | - Yumeng Liu
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, USA
| | - Shu-Ou Shan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, USA.
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26
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Zhang Y, De Laurentiis E, Bohnsack KE, Wahlig M, Ranjan N, Gruseck S, Hackert P, Wölfle T, Rodnina MV, Schwappach B, Rospert S. Ribosome-bound Get4/5 facilitates the capture of tail-anchored proteins by Sgt2 in yeast. Nat Commun 2021; 12:782. [PMID: 33542241 PMCID: PMC7862611 DOI: 10.1038/s41467-021-20981-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Accepted: 01/05/2021] [Indexed: 02/03/2023] Open
Abstract
The guided entry of tail-anchored proteins (GET) pathway assists in the posttranslational delivery of tail-anchored proteins, containing a single C-terminal transmembrane domain, to the ER. Here we uncover how the yeast GET pathway component Get4/5 facilitates capture of tail-anchored proteins by Sgt2, which interacts with tail-anchors and hands them over to the targeting component Get3. Get4/5 binds directly and with high affinity to ribosomes, positions Sgt2 close to the ribosomal tunnel exit, and facilitates the capture of tail-anchored proteins by Sgt2. The contact sites of Get4/5 on the ribosome overlap with those of SRP, the factor mediating cotranslational ER-targeting. Exposure of internal transmembrane domains at the tunnel exit induces high-affinity ribosome binding of SRP, which in turn prevents ribosome binding of Get4/5. In this way, the position of a transmembrane domain within nascent ER-targeted proteins mediates partitioning into either the GET or SRP pathway directly at the ribosomal tunnel exit. The guided entry of tail-anchored proteins (GET) pathway assists in the delivery of such proteins to the ER. Here, the authors reveal that the pathway components Get4/5 probe a region near the ribosomal exit tunnel. Upon emergence of a client protein, Get4/5 recruits Sgt2 and initiates the targeting phase of the pathway.
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Affiliation(s)
- Ying Zhang
- Institute of Biochemistry and Molecular Biology, University of Freiburg, Freiburg, Germany.,BIOSS Centre for Biological Signaling Studies, University of Freiburg, Freiburg, Germany
| | - Evelina De Laurentiis
- Department of Molecular Biology, University Medical Center Göttingen, Göttingen, Germany.,Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), Göttingen, Germany
| | - Katherine E Bohnsack
- Department of Molecular Biology, University Medical Center Göttingen, Göttingen, Germany
| | - Mascha Wahlig
- Institute of Biochemistry and Molecular Biology, University of Freiburg, Freiburg, Germany.,BIOSS Centre for Biological Signaling Studies, University of Freiburg, Freiburg, Germany
| | - Namit Ranjan
- Max-Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Simon Gruseck
- Institute of Biochemistry and Molecular Biology, University of Freiburg, Freiburg, Germany.,BIOSS Centre for Biological Signaling Studies, University of Freiburg, Freiburg, Germany
| | - Philipp Hackert
- Department of Molecular Biology, University Medical Center Göttingen, Göttingen, Germany
| | - Tina Wölfle
- Institute of Biochemistry and Molecular Biology, University of Freiburg, Freiburg, Germany.,BIOSS Centre for Biological Signaling Studies, University of Freiburg, Freiburg, Germany
| | - Marina V Rodnina
- Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), Göttingen, Germany.,Max-Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Blanche Schwappach
- Department of Molecular Biology, University Medical Center Göttingen, Göttingen, Germany. .,Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), Göttingen, Germany.
| | - Sabine Rospert
- Institute of Biochemistry and Molecular Biology, University of Freiburg, Freiburg, Germany. .,BIOSS Centre for Biological Signaling Studies, University of Freiburg, Freiburg, Germany.
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27
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Lin KF, Fry MY, Saladi SM, Clemons WM. Molecular basis of tail-anchored integral membrane protein recognition by the cochaperone Sgt2. J Biol Chem 2021; 296:100441. [PMID: 33610544 PMCID: PMC8010706 DOI: 10.1016/j.jbc.2021.100441] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 02/04/2021] [Accepted: 02/17/2021] [Indexed: 02/08/2023] Open
Abstract
The targeting and insertion of tail-anchored (TA) integral membrane proteins (IMPs) into the correct membrane is critical for cellular homeostasis. The fungal protein Sgt2, and its human homolog SGTA, is the entry point for clients to the guided entry of tail-anchored protein (GET) pathway, which targets endoplasmic reticulum-bound TA IMPs. Consisting of three structurally independent domains, the C terminus of Sgt2 binds to the hydrophobic transmembrane domain (TMD) of clients. However, the exact binding interface within Sgt2 and molecular details that underlie its binding mechanism and client preference are not known. Here, we reveal the mechanism of Sgt2 binding to hydrophobic clients, including TA IMPs. Through sequence analysis, biophysical characterization, and a series of capture assays, we establish that the Sgt2 C-terminal domain is flexible but conserved and sufficient for client binding. A molecular model for this domain reveals a helical hand forming a hydrophobic groove approximately 15 Å long that is consistent with our observed higher affinity for client TMDs with a hydrophobic face and a minimal length of 11 residues. This work places Sgt2 into a broader family of TPR-containing cochaperone proteins, demonstrating structural and sequence-based similarities to the DP domains in the yeast Hsp90 and Hsp70 coordinating protein, Sti1.
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Affiliation(s)
- Ku-Feng Lin
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, USA
| | - Michelle Y Fry
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, USA
| | - Shyam M Saladi
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, USA
| | - William M Clemons
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, USA.
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28
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Klasek L, Inoue K, Theg SM. Chloroplast Chaperonin-Mediated Targeting of a Thylakoid Membrane Protein. THE PLANT CELL 2020; 32:3884-3901. [PMID: 33093145 PMCID: PMC7721336 DOI: 10.1105/tpc.20.00309] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 08/11/2020] [Accepted: 10/21/2020] [Indexed: 05/08/2023]
Abstract
Posttranslational protein targeting requires chaperone assistance to direct insertion-competent proteins to integration pathways. Chloroplasts integrate nearly all thylakoid transmembrane proteins posttranslationally, but mechanisms in the stroma that assist their insertion remain largely undefined. Here, we investigated how the chloroplast chaperonin (Cpn60) facilitated the thylakoid integration of Plastidic type I signal peptidase 1 (Plsp1) using in vitro targeting assays. Cpn60 bound Plsp1 in the stroma. In isolated chloroplasts, the membrane integration of imported Plsp1 correlated with its dissociation from Cpn60. When the Plsp1 residues that interacted with Cpn60 were removed, Plsp1 did not integrate into the membrane. These results suggested Cpn60 was an intermediate in thylakoid targeting of Plsp1. In isolated thylakoids, the integration of Plsp1 decreased when Cpn60 was present in excess of cpSecA1, the stromal motor of the cpSec1 translocon that inserts unfolded Plsp1 into the thylakoid. An excess of cpSecA1 favored integration. Introducing Cpn60's obligate substrate RbcL displaced Cpn60-bound Plsp1; then, the released Plsp1 exhibited increased accessibility to cpSec1. These in vitro targeting experiments support a model in which Cpn60 captures and then releases insertion-competent Plsp1, whereas cpSecA1 recognizes free Plsp1 for integration. Thylakoid transmembrane proteins in the stroma can interact with Cpn60 to shield themselves from the aqueous environment.
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Affiliation(s)
- Laura Klasek
- Department of Plant Biology, University of California Davis, Davis, California 95616
| | - Kentaro Inoue
- Department of Plant Sciences, University of California Davis, Davis, California 95616
| | - Steven M Theg
- Department of Plant Biology, University of California Davis, Davis, California 95616
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29
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Ulrich K, Schwappach B, Jakob U. Thiol-based switching mechanisms of stress-sensing chaperones. Biol Chem 2020; 402:239-252. [PMID: 32990643 DOI: 10.1515/hsz-2020-0262] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2020] [Accepted: 09/11/2020] [Indexed: 12/13/2022]
Abstract
Thiol-based redox switches evolved as efficient post-translational regulatory mechanisms that enable individual proteins to rapidly respond to sudden environmental changes. While some protein functions need to be switched off to save resources and avoid potentially error-prone processes, protective functions become essential and need to be switched on. In this review, we focus on thiol-based activation mechanisms of stress-sensing chaperones. Upon stress exposure, these chaperones convert into high affinity binding platforms for unfolding proteins and protect cells against the accumulation of potentially toxic protein aggregates. Their chaperone activity is independent of ATP, a feature that becomes especially important under oxidative stress conditions, where cellular ATP levels drop and canonical ATP-dependent chaperones no longer operate. Vice versa, reductive inactivation and substrate release require the restoration of ATP levels, which ensures refolding of client proteins by ATP-dependent foldases. We will give an overview over the different strategies that cells evolved to rapidly increase the pool of ATP-independent chaperones upon oxidative stress and provide mechanistic insights into how stress conditions are used to convert abundant cellular proteins into ATP-independent holding chaperones.
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Affiliation(s)
- Kathrin Ulrich
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, 1105 N. University Ave., Ann Arbor, MI48109, USA
| | - Blanche Schwappach
- Department of Molecular Biology, Universitätsmedizin Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
| | - Ursula Jakob
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, 1105 N. University Ave., Ann Arbor, MI48109, USA.,Department of Biological Chemistry, University of Michigan, Ann Arbor, MI48109, USA
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30
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Leznicki P, High S. SGTA associates with nascent membrane protein precursors. EMBO Rep 2020; 21:e48835. [PMID: 32216016 PMCID: PMC7202230 DOI: 10.15252/embr.201948835] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 02/25/2020] [Accepted: 02/28/2020] [Indexed: 01/15/2023] Open
Abstract
The endoplasmic reticulum (ER) is a major site for membrane protein synthesis in eukaryotes. The majority of integral membrane proteins are delivered to the ER membrane via the co‐translational, signal recognition particle (SRP)‐dependent route. However, tail‐anchored proteins employ an alternative, post‐translational route(s) that relies on distinct factors such as a cytosolic protein quality control component, SGTA. We now show that SGTA is selectively recruited to ribosomes synthesising a diverse range of membrane proteins, suggesting that its biosynthetic client base also includes precursors on the co‐translational ER delivery pathway. Strikingly, SGTA is recruited to nascent membrane proteins before their transmembrane domain emerges from the ribosome. Hence, SGTA is ideally placed to capture these aggregation prone regions shortly after their synthesis. For nascent membrane proteins on the co‐translational pathway, SGTA complements the role of SRP by reducing the co‐translational ubiquitination of clients with multiple hydrophobic signal sequences. On this basis, we propose that SGTA acts to mask specific transmembrane domains located in complex membrane proteins until they can engage the ER translocon and become membrane inserted.
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Affiliation(s)
- Pawel Leznicki
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Stephen High
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
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31
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A Chaperone Lid Ensures Efficient and Privileged Client Transfer during Tail-Anchored Protein Targeting. Cell Rep 2020; 26:37-44.e7. [PMID: 30605684 DOI: 10.1016/j.celrep.2018.12.035] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2018] [Revised: 09/20/2018] [Accepted: 12/07/2018] [Indexed: 11/20/2022] Open
Abstract
Molecular chaperones play key roles in maintaining cellular proteostasis. In addition to preventing client aggregation, chaperones often relay substrates within a network while preventing off-pathway chaperones from accessing the substrate. Here we show that a conserved lid motif lining the substrate-binding groove of the Get3 ATPase enables these important functions during the targeted delivery of tail-anchored membrane proteins (TAs) to the endoplasmic reticulum. The lid prevents promiscuous TA handoff to off-pathway chaperones, and more importantly, it cooperates with the Get4/5 scaffolding complex to enable rapid and privileged TA transfer from the upstream co-chaperone Sgt2 to Get3. These findings provide a molecular mechanism by which chaperones maintain the pathway specificity of client proteins in the crowded cytosolic environment.
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32
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Abstract
Due to their topology tail-anchored (TA) proteins must target to the membrane independently of the co-translational route defined by the signal sequence recognition particle (SRP), its receptor and the translocon Sec61. More than a decade of work has extensively characterized a highly conserved pathway, the yeast GET or mammalian TRC40 pathway, which is capable of countering the biogenetic challenge posed by the C-terminal TA anchor. In this review we briefly summarize current models of this targeting route and focus on emerging aspects such as the intricate interplay with the proteostatic network of cells and with other targeting pathways. Importantly, we consider the lessons provided by the in vivo analysis of the pathway in different model organisms and by the consideration of its full client spectrum in more recent studies. This analysis of the state of the field highlights directions in which the current models may be experimentally probed and conceptually extended.
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Affiliation(s)
- Nica Borgese
- Institute of Neuroscience and BIOMETRA Department, Consiglio Nazionale delle Ricerche and Università degli Studi di Milano, via Vanvitelli 32, 20129, Milan, Italy.
| | - Javier Coy-Vergara
- Department of Molecular Biology, University of Göttingen Medical Centre, Humboldtallee 23, 37073, Göttingen, Germany
| | - Sara Francesca Colombo
- Institute of Neuroscience and BIOMETRA Department, Consiglio Nazionale delle Ricerche and Università degli Studi di Milano, via Vanvitelli 32, 20129, Milan, Italy
| | - Blanche Schwappach
- Department of Molecular Biology, University of Göttingen Medical Centre, Humboldtallee 23, 37073, Göttingen, Germany.
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33
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Shan SO. Guiding tail-anchored membrane proteins to the endoplasmic reticulum in a chaperone cascade. J Biol Chem 2019; 294:16577-16586. [PMID: 31575659 PMCID: PMC6851334 DOI: 10.1074/jbc.rev119.006197] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Newly synthesized integral membrane proteins must traverse the aqueous cytosolic environment before arrival at their membrane destination and are prone to aggregation, misfolding, and mislocalization during this process. The biogenesis of integral membrane proteins therefore poses acute challenges to protein homeostasis within a cell and requires the action of effective molecular chaperones. Chaperones that mediate membrane protein targeting not only need to protect the nascent transmembrane domains from improper exposure in the cytosol, but also need to accurately select client proteins and actively guide their clients to the appropriate target membrane. The mechanisms by which cellular chaperones work together to coordinate this complex process are only beginning to be delineated. Here, we summarize recent advances in studies of the tail-anchored membrane protein targeting pathway, which revealed a network of chaperones, cochaperones, and targeting factors that together drive and regulate this essential process. This pathway is emerging as an excellent model system to decipher the mechanism by which molecular chaperones overcome the multiple challenges during post-translational membrane protein biogenesis and to gain insights into the functional organization of multicomponent chaperone networks.
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Affiliation(s)
- Shu-Ou Shan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125
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34
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Hwang Fu YH, Chandrasekar S, Lee JH, Shan SO. A molecular recognition feature mediates ribosome-induced SRP-receptor assembly during protein targeting. J Cell Biol 2019; 218:3307-3319. [PMID: 31537711 PMCID: PMC6781444 DOI: 10.1083/jcb.201901001] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2019] [Revised: 06/28/2019] [Accepted: 08/26/2019] [Indexed: 12/21/2022] Open
Abstract
Molecular recognition features (MoRFs) provide interaction motifs in intrinsically disordered protein regions to mediate diverse cellular functions. Here we report that a MoRF element, located in the disordered linker domain of the mammalian signal recognition particle (SRP) receptor and conserved among eukaryotes, plays an essential role in sensing the ribosome during cotranslational protein targeting to the endoplasmic reticulum. Loss of the MoRF in the SRP receptor (SR) largely abolishes the ability of the ribosome to activate SRP-SR assembly and impairs cotranslational protein targeting. These results demonstrate a novel role for MoRF elements and provide a mechanism for the ribosome-induced activation of the mammalian SRP pathway. Kinetic analyses and comparison with the bacterial SRP further suggest that the SR MoRF functionally replaces the essential GNRA tetraloop in the bacterial SRP RNA, providing an example for the replacement of RNA function by proteins during the evolution of ancient ribonucleoprotein particles.
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Affiliation(s)
- Yu-Hsien Hwang Fu
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA
| | - Sowmya Chandrasekar
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA
| | - Jae Ho Lee
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA
| | - Shu-Ou Shan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA
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35
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Becker T, Song J, Pfanner N. Versatility of Preprotein Transfer from the Cytosol to Mitochondria. Trends Cell Biol 2019; 29:534-548. [PMID: 31030976 DOI: 10.1016/j.tcb.2019.03.007] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 03/27/2019] [Accepted: 03/28/2019] [Indexed: 11/16/2022]
Abstract
Mitochondrial biogenesis requires the import of a large number of precursor proteins from the cytosol. Although specific membrane-bound preprotein translocases have been characterized in detail, it was assumed that protein transfer from the cytosol to mitochondria mainly involved unselective binding to molecular chaperones. Recent findings suggest an unexpected versatility of protein transfer to mitochondria. Cytosolic factors have been identified that bind to selected subsets of preproteins and guide them to mitochondrial receptors in a post-translational manner. Cotranslational import processes are emerging. Mechanisms for crosstalk between protein targeting to mitochondria and other cell organelles, in particular the endoplasmic reticulum (ER) and peroxisomes, have been uncovered. We discuss how a network of cytosolic machineries and targeting pathways promote and regulate preprotein transfer into mitochondria.
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Affiliation(s)
- Thomas Becker
- Institute of Biochemistry and Molecular Biology, Centre for Biochemistry and Molecular Cell Research (ZBMZ), Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; Centre for Integrative Biological Signaling Studies (CIBSS), University of Freiburg, 79104 Freiburg, Germany.
| | - Jiyao Song
- Institute of Biochemistry and Molecular Biology, Centre for Biochemistry and Molecular Cell Research (ZBMZ), Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Nikolaus Pfanner
- Institute of Biochemistry and Molecular Biology, Centre for Biochemistry and Molecular Cell Research (ZBMZ), Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; Centre for Integrative Biological Signaling Studies (CIBSS), University of Freiburg, 79104 Freiburg, Germany.
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36
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Dederer V, Khmelinskii A, Huhn AG, Okreglak V, Knop M, Lemberg MK. Cooperation of mitochondrial and ER factors in quality control of tail-anchored proteins. eLife 2019; 8:45506. [PMID: 31172943 PMCID: PMC6586462 DOI: 10.7554/elife.45506] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Accepted: 06/06/2019] [Indexed: 01/04/2023] Open
Abstract
Tail-anchored (TA) proteins insert post-translationally into the endoplasmic reticulum (ER), the outer mitochondrial membrane (OMM) and peroxisomes. Whereas the GET pathway controls ER-targeting, no dedicated factors are known for OMM insertion, posing the question of how accuracy is achieved. The mitochondrial AAA-ATPase Msp1 removes mislocalized TA proteins from the OMM, but it is unclear, how Msp1 clients are targeted for degradation. Here we screened for factors involved in degradation of TA proteins mislocalized to mitochondria. We show that the ER-associated degradation (ERAD) E3 ubiquitin ligase Doa10 controls cytoplasmic level of Msp1 clients. Furthermore, we identified the uncharacterized OMM protein Fmp32 and the ectopically expressed subunit of the ER-mitochondria encounter structure (ERMES) complex Gem1 as native clients for Msp1 and Doa10. We propose that productive localization of TA proteins to the OMM is ensured by complex assembly, while orphan subunits are extracted by Msp1 and eventually degraded by Doa10.
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Affiliation(s)
- Verena Dederer
- Centre for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Anton Khmelinskii
- Centre for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, Heidelberg, Germany.,Institute of Molecular Biology (IMB), Mainz, Germany
| | - Anna Gesine Huhn
- Centre for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Voytek Okreglak
- Calico Life Sciences LLC, South San Francisco, United States
| | - Michael Knop
- Centre for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, Heidelberg, Germany.,Cell Morphogenesis and Signal Transduction, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Marius K Lemberg
- Centre for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, Heidelberg, Germany
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37
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Rada P, Makki A, Žárský V, Tachezy J. Targeting of tail-anchored proteins to Trichomonas vaginalis hydrogenosomes. Mol Microbiol 2019; 111:588-603. [PMID: 30506591 DOI: 10.1111/mmi.14175] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/25/2018] [Indexed: 01/17/2023]
Abstract
Tail-anchored (TA) proteins are membrane proteins that are found in all domains of life. They consist of an N-terminal domain that performs various functions and a single transmembrane domain (TMD) near the C-terminus. In eukaryotes, TA proteins are targeted to the membranes of mitochondria, the endoplasmic reticulum (ER), peroxisomes and in plants, chloroplasts. The targeting of these proteins to their specific destinations correlates with the properties of the C-terminal domain, mainly the TMD hydrophobicity and the net charge of the flanking regions. Trichomonas vaginalis is a human parasite that has adapted to oxygen-poor environment. This adaptation is reflected by the presence of highly modified mitochondria (hydrogenosomes) and the absence of peroxisomes. The proteome of hydrogenosomes is considerably reduced; however, our bioinformatic analysis predicted 120 putative hydrogenosomal TA proteins. Seven proteins were selected to prove their localization. The elimination of the net positive charge in the C-tail of the hydrogenosomal TA4 protein resulted in its dual localization to hydrogenosomes and the ER, causing changes in ER morphology. Domain mutation and swap experiments with hydrogenosomal (TA4) and ER (TAPDI) proteins indicated that the general principles for specific targeting are conserved across eukaryotic lineages, including T. vaginalis; however, there are also significant lineage-specific differences.
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Affiliation(s)
- Petr Rada
- Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Průmyslová 595, Vestec, 25242, Czech Republic
| | - Abhijith Makki
- Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Průmyslová 595, Vestec, 25242, Czech Republic
| | - Vojtěch Žárský
- Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Průmyslová 595, Vestec, 25242, Czech Republic
| | - Jan Tachezy
- Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Průmyslová 595, Vestec, 25242, Czech Republic
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38
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Mayer MP, Gierasch LM. Recent advances in the structural and mechanistic aspects of Hsp70 molecular chaperones. J Biol Chem 2018; 294:2085-2097. [PMID: 30455352 DOI: 10.1074/jbc.rev118.002810] [Citation(s) in RCA: 169] [Impact Index Per Article: 28.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Hsp70 chaperones are central hubs of the protein quality control network and collaborate with co-chaperones having a J-domain (an ∼70-residue-long helical hairpin with a flexible loop and a conserved His-Pro-Asp motif required for ATP hydrolysis by Hsp70s) and also with nucleotide exchange factors to facilitate many protein-folding processes that (re)establish protein homeostasis. The Hsp70s are highly dynamic nanomachines that modulate the conformation of their substrate polypeptides by transiently binding to short, mostly hydrophobic stretches. This interaction is regulated by an intricate allosteric mechanism. The J-domain co-chaperones target Hsp70 to their polypeptide substrates, and the nucleotide exchange factors regulate the lifetime of the Hsp70-substrate complexes. Significant advances in recent years are beginning to unravel the molecular mechanism of this chaperone machine and how they treat their substrate proteins.
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Affiliation(s)
- Matthias P Mayer
- From the Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH-Alliance, 69120 Heidelberg, Germany and
| | - Lila M Gierasch
- the Departments of Biochemistry and Molecular Biology and.,Chemistry, University of Massachusetts, Amherst, Massachusetts 01003
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