1
|
Page KR, Nguyen VN, Pleiner T, Tomaleri GP, Wang ML, Guna A, Hazu M, Wang TY, Chou TF, Voorhees RM. Role of a holo-insertase complex in the biogenesis of biophysically diverse ER membrane proteins. Mol Cell 2024:S1097-2765(24)00659-2. [PMID: 39173640 DOI: 10.1016/j.molcel.2024.08.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 04/19/2024] [Accepted: 08/02/2024] [Indexed: 08/24/2024]
Abstract
Mammalian membrane proteins perform essential physiologic functions that rely on their accurate insertion and folding at the endoplasmic reticulum (ER). Using forward and arrayed genetic screens, we systematically studied the biogenesis of a panel of membrane proteins, including several G-protein-coupled receptors (GPCRs). We observed a central role for the insertase, the ER membrane protein complex (EMC), and developed a dual-guide approach to identify genetic modifiers of the EMC. We found that the back of Sec61 (BOS) complex, a component of the multipass translocon, was a physical and genetic interactor of the EMC. Functional and structural analysis of the EMC⋅BOS holocomplex showed that characteristics of a GPCR's soluble domain determine its biogenesis pathway. In contrast to prevailing models, no single insertase handles all substrates. We instead propose a unifying model for coordination between the EMC, the multipass translocon, and Sec61 for the biogenesis of diverse membrane proteins in human cells.
Collapse
Affiliation(s)
- Katharine R Page
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 E. California Ave., Pasadena, CA 91125, USA
| | - Vy N Nguyen
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 E. California Ave., Pasadena, CA 91125, USA
| | - Tino Pleiner
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 E. California Ave., Pasadena, CA 91125, USA
| | - Giovani Pinton Tomaleri
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 E. California Ave., Pasadena, CA 91125, USA
| | - Maxine L Wang
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 E. California Ave., Pasadena, CA 91125, USA
| | - Alina Guna
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 E. California Ave., Pasadena, CA 91125, USA
| | - Masami Hazu
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 E. California Ave., Pasadena, CA 91125, USA
| | - Ting-Yu Wang
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 E. California Ave., Pasadena, CA 91125, USA
| | - Tsui-Fen Chou
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 E. California Ave., Pasadena, CA 91125, USA
| | - Rebecca M Voorhees
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 E. California Ave., Pasadena, CA 91125, USA; Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125, USA.
| |
Collapse
|
2
|
Gemmer M, Chaillet ML, Förster F. Exploring the molecular composition of the multipass translocon in its native membrane environment. Life Sci Alliance 2024; 7:e202302496. [PMID: 38866426 PMCID: PMC11169918 DOI: 10.26508/lsa.202302496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Revised: 05/22/2024] [Accepted: 05/23/2024] [Indexed: 06/14/2024] Open
Abstract
Multispanning membrane proteins are inserted into the endoplasmic reticulum membrane by the ribosome-bound multipass translocon (MPT) machinery. Based on cryo-electron tomography and extensive subtomogram analysis, we reveal the composition and arrangement of ribosome-bound MPT components in their native membrane environment. The intramembrane chaperone complex PAT and the translocon-associated protein (TRAP) complex associate substoichiometrically with the MPT in a translation-dependent manner. Although PAT is preferentially part of MPTs bound to translating ribosomes, the abundance of TRAP is highest in MPTs associated with non-translating ribosomes. The subtomogram average of the TRAP-containing MPT reveals intermolecular contacts between the luminal domains of TRAP and an unknown subunit of the back-of-Sec61 complex. AlphaFold modeling suggests this protein is nodal modulator, bridging the luminal domains of nicalin and TRAPα. Collectively, our results visualize the variability of MPT factors in the native membrane environment dependent on the translational activity of the bound ribosome.
Collapse
Affiliation(s)
- Max Gemmer
- https://ror.org/04pp8hn57 Structural Biochemistry, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
| | - Marten L Chaillet
- https://ror.org/04pp8hn57 Structural Biochemistry, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
| | - Friedrich Förster
- https://ror.org/04pp8hn57 Structural Biochemistry, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
| |
Collapse
|
3
|
Chamness LM, Kuntz CP, McKee AG, Penn WD, Hemmerich CM, Rusch DB, Woods H, Dyotima, Meiler J, Schlebach JP. Divergent folding-mediated epistasis among unstable membrane protein variants. eLife 2024; 12:RP92406. [PMID: 39078397 PMCID: PMC11288631 DOI: 10.7554/elife.92406] [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] [Indexed: 07/31/2024] Open
Abstract
Many membrane proteins are prone to misfolding, which compromises their functional expression at the plasma membrane. This is particularly true for the mammalian gonadotropin-releasing hormone receptor GPCRs (GnRHR). We recently demonstrated that evolutionary GnRHR modifications appear to have coincided with adaptive changes in cotranslational folding efficiency. Though protein stability is known to shape evolution, it is unclear how cotranslational folding constraints modulate the synergistic, epistatic interactions between mutations. We therefore compared the pairwise interactions formed by mutations that disrupt the membrane topology (V276T) or tertiary structure (W107A) of GnRHR. Using deep mutational scanning, we evaluated how the plasma membrane expression of these variants is modified by hundreds of secondary mutations. An analysis of 251 mutants in three genetic backgrounds reveals that V276T and W107A form distinct epistatic interactions that depend on both the severity and the mechanism of destabilization. V276T forms predominantly negative epistatic interactions with destabilizing mutations in soluble loops. In contrast, W107A forms positive interactions with mutations in both loops and transmembrane domains that reflect the diminishing impacts of the destabilizing mutations in variants that are already unstable. These findings reveal how epistasis is remodeled by conformational defects in membrane proteins and in unstable proteins more generally.
Collapse
Affiliation(s)
- Laura M Chamness
- Department of Chemistry, Indiana UniversityBloomingtonUnited States
| | - Charles P Kuntz
- The James Tarpo Jr. and Margaret Tarpo Department of Chemistry, Purdue UniversityWest LafayetteUnited States
| | - Andrew G McKee
- Department of Chemistry, Indiana UniversityBloomingtonUnited States
| | - Wesley D Penn
- Department of Chemistry, Indiana UniversityBloomingtonUnited States
| | | | - Douglas B Rusch
- Center for Genomics and Bioinformatics, Indiana UniversityBloomingtonUnited States
| | - Hope Woods
- Department of Chemistry, Vanderbilt UniversityNashvilleUnited States
- Chemical and Physical Biology Program, Vanderbilt UniversityNashvilleUnited States
| | - Dyotima
- Department of Chemistry, Indiana UniversityBloomingtonUnited States
| | - Jens Meiler
- Department of Chemistry, Vanderbilt UniversityNashvilleUnited States
- Institute for Drug Discovery, Leipzig UniversityLeipzigGermany
| | - Jonathan P Schlebach
- The James Tarpo Jr. and Margaret Tarpo Department of Chemistry, Purdue UniversityWest LafayetteUnited States
| |
Collapse
|
4
|
van der Sluijs P, Hoelen H, Schmidt A, Braakman I. The Folding Pathway of ABC Transporter CFTR: Effective and Robust. J Mol Biol 2024; 436:168591. [PMID: 38677493 DOI: 10.1016/j.jmb.2024.168591] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Revised: 04/16/2024] [Accepted: 04/23/2024] [Indexed: 04/29/2024]
Abstract
De novo protein folding into a native three-dimensional structure is indispensable for biological function, is instructed by its amino acid sequence, and occurs along a vectorial trajectory. The human proteome contains thousands of membrane-spanning proteins, whose biosynthesis begins on endoplasmic reticulum-associated ribosomes. Nearly half of all membrane proteins traverse the membrane more than once, including therapeutically important protein families such as solute carriers, G-protein-coupled receptors, and ABC transporters. These mediate a variety of functions like signal transduction and solute transport and are often of vital importance for cell function and tissue homeostasis. Missense mutations in multispan membrane proteins can lead to misfolding and cause disease; an example is the ABC transporter Cystic Fibrosis Transmembrane Conductance Regulator (CFTR). Even though our understanding of multispan membrane-protein folding still is rather rudimental, the cumulative knowledge of 20 years of basic research on CFTR folding has led to development of drugs that modulate the misfolded protein. This has provided the prospect of a life without CF to the vast majority of patients. In this review we describe our understanding of the folding pathway of CFTR in cells, which is modular and tolerates many defects, making it effective and robust. We address how modulator drugs affect folding and function of CFTR, and distinguish protein stability from its folding process. Since the domain architecture of (mammalian) ABC transporters are highly conserved, we anticipate that the insights we discuss here for folding of CFTR may lay the groundwork for understanding the general rules of ABC-transporter folding.
Collapse
Affiliation(s)
- Peter van der Sluijs
- Cellular Protein Chemistry, Bijvoet Centre for Biomolecular Research, Utrecht University, 3584 CH Utrecht, the Netherlands.
| | - Hanneke Hoelen
- Cellular Protein Chemistry, Bijvoet Centre for Biomolecular Research, Utrecht University, 3584 CH Utrecht, the Netherlands; Present address: GenDx, Yalelaan 48, 3584 CM Utrecht, The Netherlands
| | - Andre Schmidt
- Cellular Protein Chemistry, Bijvoet Centre for Biomolecular Research, Utrecht University, 3584 CH Utrecht, the Netherlands; 3D-Pharmxchange, Tilburg, the Netherlands
| | - Ineke Braakman
- Cellular Protein Chemistry, Bijvoet Centre for Biomolecular Research, Utrecht University, 3584 CH Utrecht, the Netherlands
| |
Collapse
|
5
|
Hegde RS, Keenan RJ. A unifying model for membrane protein biogenesis. Nat Struct Mol Biol 2024; 31:1009-1017. [PMID: 38811793 PMCID: PMC7616256 DOI: 10.1038/s41594-024-01296-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [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.
Collapse
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.
| |
Collapse
|
6
|
Egly CL, Barny LA, Do T, McDonald EF, Knollmann BC, Plate L. The proteostasis interactomes of trafficking-deficient variants of the voltage-gated potassium channel K V11.1 associated with long QT syndrome. J Biol Chem 2024; 300:107465. [PMID: 38876300 PMCID: PMC11284683 DOI: 10.1016/j.jbc.2024.107465] [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: 03/28/2024] [Revised: 05/16/2024] [Accepted: 06/04/2024] [Indexed: 06/16/2024] Open
Abstract
The voltage-gated potassium ion channel KV11.1 plays a critical role in cardiac repolarization. Genetic variants that render Kv11.1 dysfunctional cause long QT syndrome (LQTS), which is associated with fatal arrhythmias. Approximately 90% of LQTS-associated variants cause intracellular protein transport (trafficking) dysfunction, which pharmacological chaperones like E-4031 can rescue. Protein folding and trafficking decisions are regulated by chaperones, protein quality control factors, and trafficking machinery comprising the cellular proteostasis network. Here, we test whether trafficking dysfunction is associated with alterations in the proteostasis network of pathogenic Kv11.1 variants and whether pharmacological chaperones can normalize the proteostasis network of responsive variants. We used affinity-purification coupled with tandem mass tag-based quantitative mass spectrometry to assess protein interaction changes of WT KV11.1 or trafficking-deficient channel variants in the presence or absence of E-4031. We identified 572 core KV11.1 protein interactors. Trafficking-deficient variants KV11.1-G601S and KV11.1-G601S-G965∗ had significantly increased interactions with proteins responsible for folding, trafficking, and degradation compared to WT. We confirmed previous findings that the proteasome is critical for KV11.1 degradation. Our report provides the first comprehensive characterization of protein quality control mechanisms of KV11.1. We find extensive interactome remodeling associated with trafficking-deficient KV11.1 variants and with pharmacological chaperone rescue of KV11.1 cell surface expression. The identified protein interactions could be targeted therapeutically to improve KV11.1 trafficking and treat LQTS.
Collapse
Affiliation(s)
- Christian L Egly
- Department of Medicine, Vanderbilt University Medical Center, Nasville, Tennessee, USA
| | - Lea A Barny
- Program in Chemical and Physical Biology, Vanderbilt University, Nashville, Tennessee, USA; Department of Chemistry, Vanderbilt University, Nashville, Tennessee, USA
| | - Tri Do
- Department of Medicine, Vanderbilt University Medical Center, Nasville, Tennessee, USA
| | - Eli F McDonald
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee, USA
| | - Björn C Knollmann
- Department of Medicine, Vanderbilt University Medical Center, Nasville, Tennessee, USA.
| | - Lars Plate
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee, USA; Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, USA; Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA.
| |
Collapse
|
7
|
Lewis AJO, Zhong F, Keenan RJ, Hegde RS. Structural analysis of the dynamic ribosome-translocon complex. eLife 2024; 13:RP95814. [PMID: 38896445 PMCID: PMC11186639 DOI: 10.7554/elife.95814] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2024] Open
Abstract
The protein translocon at the endoplasmic reticulum comprises the Sec61 translocation channel and numerous accessory factors that collectively facilitate the biogenesis of secretory and membrane proteins. Here, we leveraged recent advances in cryo-electron microscopy (cryo-EM) and structure prediction to derive insights into several novel configurations of the ribosome-translocon complex. We show how a transmembrane domain (TMD) in a looped configuration passes through the Sec61 lateral gate during membrane insertion; how a nascent chain can bind and constrain the conformation of ribosomal protein uL22; and how the translocon-associated protein (TRAP) complex can adjust its position during different stages of protein biogenesis. Most unexpectedly, we find that a large proportion of translocon complexes contains RAMP4 intercalated into Sec61's lateral gate, widening Sec61's central pore and contributing to its hydrophilic interior. These structures lead to mechanistic hypotheses for translocon function and highlight a remarkably plastic machinery whose conformations and composition adjust dynamically to its diverse range of substrates.
Collapse
Affiliation(s)
- Aaron JO Lewis
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | - Frank Zhong
- Department of Molecular Genetics and Cell Biology, The University of ChicagoChicagoUnited States
| | - Robert J Keenan
- Department of Biochemistry and Molecular Biology, The University of ChicagoChicagoUnited States
| | | |
Collapse
|
8
|
Mattos D, Neves WD, Kitamura T, Pradhan R, Wan X, da Hora CC, Tranter D, Kazemi S, Yu X, Tripathy N, Paavilainen VO, McPhail KL, Oishi S, Badr CE, Ishmael JE. Diastereomers of Coibamide A Show Altered Sec61 Client Selectivity and Ligand-Dependent Activity against Patient-Derived Glioma Stem-like Cells. ACS Pharmacol Transl Sci 2024; 7:1823-1838. [PMID: 38898945 PMCID: PMC11184607 DOI: 10.1021/acsptsci.4c00049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 04/23/2024] [Accepted: 04/29/2024] [Indexed: 06/21/2024]
Abstract
Coibamide A (CbA) is a cyanobacterial lariat depsipeptide that selectively inhibits multiple secreted and integral membrane proteins from entering the endoplasmic reticulum secretory pathway through binding the alpha subunit of the Sec61 translocon. As a complex peptide-based macrocycle with 13 stereogenic centers, CbA is presumed to adopt a conformationally restricted orientation in the ligand-bound state, resulting in potent antitumor and antiangiogenic bioactivity. A stereochemical structure-activity relationship for CbA was previously defined based on cytotoxicity against established cancer cell lines. However, the ability of synthetic isomers to inhibit the biosynthesis of specific Sec61 substrates was unknown. Here, we report that two less toxic diastereomers of CbA, [L-Hiv2]-CbA and [L-Hiv2, L-MeAla11]-CbA, are pharmacologically active Sec61 inhibitors. Both compounds inhibited the expression of a secreted reporter (Gaussia luciferase), VEGF-A, and a Type 1 membrane protein (VCAM1), while [L-Hiv2]-CbA also decreased the expression of ICAM1 and BiP/GRP78. Analysis of 43 different chemokines in the secretome of SF-268 glioblastoma cells revealed different inhibitory profiles for the two diastereomers. When the cytotoxic potential of CbA compounds was compared against a panel of patient-derived glioblastoma stem-like cells (GSCs), Sec61 inhibitors were remarkably toxic to five of the six GSCs tested. Each ligand showed a distinct cytotoxic potency and selectivity pattern for CbA-sensitive GSCs, with IC50 values ranging from subnanomolar to low micromolar concentrations. Together, these findings highlight the extreme sensitivity of GSCs to Sec61 modulation and the importance of ligand stereochemistry in determining the spectrum of inhibited Sec61 client proteins.
Collapse
Affiliation(s)
- Daphne
R. Mattos
- Department
of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon 97331, United States
| | - Willian das Neves
- Department
of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02129, United States
| | - Takashi Kitamura
- Graduate
School of Pharmaceutical Sciences, Kyoto
University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Richa Pradhan
- Department
of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02129, United States
| | - Xuemei Wan
- Department
of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon 97331, United States
| | - Cintia Carla da Hora
- Department
of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02129, United States
| | - Dale Tranter
- Institute
of Biotechnology, University of Helsinki, Helsinki 00014, Finland
| | - Soheila Kazemi
- Department
of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon 97331, United States
| | - Xinhui Yu
- Department
of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon 97331, United States
| | - Nirmalya Tripathy
- Department
of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon 97331, United States
| | | | - Kerry L. McPhail
- Department
of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon 97331, United States
| | - Shinya Oishi
- Graduate
School of Pharmaceutical Sciences, Kyoto
University, Sakyo-ku, Kyoto 606-8501, Japan
- Laboratory
of Medicinal Chemistry, Kyoto Pharmaceutical
University, Yamashina-ku, Kyoto 607-8412, Japan
| | - Christian E. Badr
- Department
of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02129, United States
| | - Jane E. Ishmael
- Department
of Pharmaceutical Sciences, College of Pharmacy, Oregon State University, Corvallis, Oregon 97331, United States
| |
Collapse
|
9
|
Duart G, Graña-Montes R, Pastor-Cantizano N, Mingarro I. Experimental and computational approaches for membrane protein insertion and topology determination. Methods 2024; 226:102-119. [PMID: 38604415 DOI: 10.1016/j.ymeth.2024.03.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 03/13/2024] [Accepted: 03/22/2024] [Indexed: 04/13/2024] Open
Abstract
Membrane proteins play pivotal roles in a wide array of cellular processes and constitute approximately a quarter of the protein-coding genes across all organisms. Despite their ubiquity and biological significance, our understanding of these proteins remains notably less comprehensive compared to their soluble counterparts. This disparity in knowledge can be attributed, in part, to the inherent challenges associated with employing specialized techniques for the investigation of membrane protein insertion and topology. This review will center on a discussion of molecular biology methodologies and computational prediction tools designed to elucidate the insertion and topology of helical membrane proteins.
Collapse
Affiliation(s)
- Gerard Duart
- Departament de Bioquímica i Biologia Molecular, Institut Universitari de Biotecnologia i Biomedicina (BIOTECMED), Universitat de València, E-46100 Burjassot, Spain
| | - Ricardo Graña-Montes
- Departament de Bioquímica i Biologia Molecular, Institut Universitari de Biotecnologia i Biomedicina (BIOTECMED), Universitat de València, E-46100 Burjassot, Spain
| | - Noelia Pastor-Cantizano
- Departament de Bioquímica i Biologia Molecular, Institut Universitari de Biotecnologia i Biomedicina (BIOTECMED), Universitat de València, E-46100 Burjassot, Spain
| | - Ismael Mingarro
- Departament de Bioquímica i Biologia Molecular, Institut Universitari de Biotecnologia i Biomedicina (BIOTECMED), Universitat de València, E-46100 Burjassot, Spain.
| |
Collapse
|
10
|
Huang Y, Gou T, Li W, Han F. Unraveling the immune functions of large yellow croaker Tmem208 in response to Pseudomonas plecoglossicida: Insights from cloning, expression profiling, and transcriptome analysis. FISH & SHELLFISH IMMUNOLOGY 2024; 149:109584. [PMID: 38670411 DOI: 10.1016/j.fsi.2024.109584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Revised: 04/22/2024] [Accepted: 04/22/2024] [Indexed: 04/28/2024]
Abstract
Pseudomonas plecoglossicida, the causative agent of Visceral White Spot Disease, poses substantial risks to large yellow croaker (Larimichthys crocea) aquaculture. Previous genome-wide association studies (GWAS), directed towards elucidating the resistance mechanisms of large yellow croaker against this affliction, suggested that the transmembrane protein 208 (named Lctmem208) may confer a potential advantage. TMEM proteins, particularly TMEM208 located in the endoplasmic reticulum, plays significant roles in autophagy, ER stress, and dynamics of cancer cell. However, research on TMEM's function in teleost fish immunity remains sparse, highlighting a need for further study. This study embarks on a comprehensive examination of LcTmem208, encompassing cloning, molecular characterization, and its dynamics in immune function in response to Pseudomonas plecoglossicida infection. Our findings reveal that LcTmem208 is highly conserved across teleost species, exhibiting pronounced expression in immune-relevant tissues, which escalates significantly upon pathogenic challenge. Transcriptome analysis subsequent to LcTmem208 overexpression in kidney cells unveiled its pivotal role in modulating immune-responsive processes, notably the p53 signaling pathway and cytokine-mediated interactions. Enhanced phagocytic activity in macrophages overexpressing LcTmem208 underscores its importance in innate immunity. Taken together, this is the first time reported the critical involvement of LcTmem208 in regulating innate immune responses of defensing P. plecoglossicida, thereby offering valuable insights into teleost fish immunity and potential strategies for the selective breeding of disease-resistant strains of large yellow croaker in aquaculture practices.
Collapse
Affiliation(s)
- Ying Huang
- State Key Laboratory of Mariculture Breeding, Fujian Provincial Key Laboratory of Marine Fishery Resources and Eco-Environment, Fisheries College, Jimei University, Xiamen, 361000, PR China
| | - Tao Gou
- State Key Laboratory of Mariculture Breeding, Fujian Provincial Key Laboratory of Marine Fishery Resources and Eco-Environment, Fisheries College, Jimei University, Xiamen, 361000, PR China
| | - Wanbo Li
- State Key Laboratory of Mariculture Breeding, Fujian Provincial Key Laboratory of Marine Fishery Resources and Eco-Environment, Fisheries College, Jimei University, Xiamen, 361000, PR China
| | - Fang Han
- State Key Laboratory of Mariculture Breeding, Fujian Provincial Key Laboratory of Marine Fishery Resources and Eco-Environment, Fisheries College, Jimei University, Xiamen, 361000, PR China.
| |
Collapse
|
11
|
Vismpas D, Förster F. RAMPing up knowledge of the translocon. eLife 2024; 13:e98548. [PMID: 38787756 PMCID: PMC11126307 DOI: 10.7554/elife.98548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2024] Open
Abstract
Advanced cryo-EM approaches reveal surprising insights into the molecular structure that allows nascent proteins to be inserted into the membrane of the endoplasmic reticulum.
Collapse
Affiliation(s)
- Dimitrios Vismpas
- Bijvoet Center for Biomolecular Research, Utrecht UniversityUtrechtNetherlands
| | - Friedrich Förster
- Bijvoet Center for Biomolecular Research, Utrecht UniversityUtrechtNetherlands
| |
Collapse
|
12
|
Ji J, Cui MK, Zou R, Wu MZ, Ge MX, Li J, Zhang ZR. An ATP13A1-assisted topogenesis pathway for folding multi-spanning membrane proteins. Mol Cell 2024; 84:1917-1931.e15. [PMID: 38723633 DOI: 10.1016/j.molcel.2024.04.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 02/15/2024] [Accepted: 04/17/2024] [Indexed: 05/19/2024]
Abstract
Many multi-spanning membrane proteins contain poorly hydrophobic transmembrane domains (pTMDs) protected from phospholipid in mature structure. Nascent pTMDs are difficult for translocon to recognize and insert. How pTMDs are discerned and packed into mature, muti-spanning configuration remains unclear. Here, we report that pTMD elicits a post-translational topogenesis pathway for its recognition and integration. Using six-spanning protein adenosine triphosphate-binding cassette transporter G2 (ABCG2) and cultured human cells as models, we show that ABCG2's pTMD2 can pass through translocon into the endoplasmic reticulum (ER) lumen, yielding an intermediate with inserted yet mis-oriented downstream TMDs. After translation, the intermediate recruits P5A-ATPase ATP13A1, which facilitates TMD re-orientation, allowing further folding and the integration of the remaining lumen-exposed pTMD2. Depleting ATP13A1 or disrupting pTMD-characteristic residues arrests intermediates with mis-oriented and exposed TMDs. Our results explain how a "difficult" pTMD is co-translationally skipped for insertion and post-translationally buried into the final correct structure at the late folding stage to avoid excessive lipid exposure.
Collapse
Affiliation(s)
- Jia Ji
- Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 100 Haike Road, Shanghai 201210, China; University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100101, China
| | - Meng-Ke Cui
- Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 100 Haike Road, Shanghai 201210, China; University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100101, China
| | - Rong Zou
- Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 100 Haike Road, Shanghai 201210, China; University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100101, China
| | - Ming-Zhi Wu
- Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 100 Haike Road, Shanghai 201210, China; University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100101, China
| | - Man-Xi Ge
- Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 100 Haike Road, Shanghai 201210, China; University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100101, China
| | - Jiqiang Li
- Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 100 Haike Road, Shanghai 201210, China; University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100101, China
| | - Zai-Rong Zhang
- Interdisciplinary Research Center on Biology and Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 100 Haike Road, Shanghai 201210, China; University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100101, China.
| |
Collapse
|
13
|
Yao J, Hong H. Steric trapping strategy for studying the folding of helical membrane proteins. Methods 2024; 225:1-12. [PMID: 38428472 PMCID: PMC11107808 DOI: 10.1016/j.ymeth.2024.02.007] [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: 11/16/2023] [Revised: 02/11/2024] [Accepted: 02/18/2024] [Indexed: 03/03/2024] Open
Abstract
Elucidating the folding energy landscape of membrane proteins is essential to the understanding of the proteins' stabilizing forces, folding mechanisms, biogenesis, and quality control. This is not a trivial task because the reversible control of folding is inherently difficult in a lipid bilayer environment. Recently, novel methods have been developed, each of which has a unique strength in investigating specific aspects of membrane protein folding. Among such methods, steric trapping is a versatile strategy allowing a reversible control of membrane protein folding with minimal perturbation of native protein-water and protein-lipid interactions. In a nutshell, steric trapping exploits the coupling of spontaneous denaturation of a doubly biotinylated protein to the simultaneous binding of bulky monovalent streptavidin molecules. This strategy has been evolved to investigate key elements of membrane protein folding such as thermodynamic stability, spontaneous denaturation rates, conformational features of the denatured states, and cooperativity of stabilizing interactions. In this review, we describe the critical methodological advancement, limitation, and outlook of the steric trapping strategy.
Collapse
Affiliation(s)
- Jiaqi Yao
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
| | - Heedeok Hong
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA; Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI 48824, USA.
| |
Collapse
|
14
|
Li D, Rocha-Roa C, Schilling MA, Reinisch KM, Vanni S. Lipid scrambling is a general feature of protein insertases. Proc Natl Acad Sci U S A 2024; 121:e2319476121. [PMID: 38621120 PMCID: PMC11047089 DOI: 10.1073/pnas.2319476121] [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: 11/07/2023] [Accepted: 03/13/2024] [Indexed: 04/17/2024] Open
Abstract
Glycerophospholipids are synthesized primarily in the cytosolic leaflet of the endoplasmic reticulum (ER) membrane and must be equilibrated between bilayer leaflets to allow the ER and membranes derived from it to grow. Lipid equilibration is facilitated by integral membrane proteins called "scramblases." These proteins feature a hydrophilic groove allowing the polar heads of lipids to traverse the hydrophobic membrane interior, similar to a credit card moving through a reader. Nevertheless, despite their fundamental role in membrane expansion and dynamics, the identity of most scramblases has remained elusive. Here, combining biochemical reconstitution and molecular dynamics simulations, we show that lipid scrambling is a general feature of protein insertases, integral membrane proteins which insert polypeptide chains into membranes of the ER and organelles disconnected from vesicle trafficking. Our data indicate that lipid scrambling occurs in the same hydrophilic channel through which protein insertion takes place and that scrambling is abolished in the presence of nascent polypeptide chains. We propose that protein insertases could have a so-far-overlooked role in membrane dynamics as scramblases.
Collapse
Affiliation(s)
- Dazhi Li
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT06520
| | - Cristian Rocha-Roa
- Department of Biology, University of Fribourg, FribourgCH-1700, Switzerland
| | - Matthew A. Schilling
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT06520
| | - Karin M. Reinisch
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT06520
| | - Stefano Vanni
- Department of Biology, University of Fribourg, FribourgCH-1700, Switzerland
- Swiss National Center for Competence in Research Bio-Inspired Materials, University of Fribourg, FribourgCH-1700, Switzerland
| |
Collapse
|
15
|
Zhu Q, Zhu X, Zhang L. ER membrane complex (EMC): Structure, functions, and roles in diseases. FASEB J 2024; 38:e23539. [PMID: 38498340 DOI: 10.1096/fj.202302266r] [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: 11/02/2023] [Revised: 01/22/2024] [Accepted: 02/21/2024] [Indexed: 03/20/2024]
Abstract
The endoplasmic reticulum (ER) is the largest membrane system in eukaryotic cells and is the primary site for the biosynthesis of lipids and carbohydrates, as well as for the folding, assembly, modification, and transport of secreted and integrated membrane proteins. The ER membrane complex (EMC) on the ER membrane is an ER multiprotein complex that affects the quality control of membrane proteins, which is abundant and widely preserved. Its disruption has been found to affect a wide range of processes, including protein and lipid synthesis, organelle communication, endoplasmic reticulum stress, and viral maturation, and may lead to neurodevelopmental disorders and cancer. Therefore, EMC has attracted the attention of many scholars and become a hot field. In this paper, we summarized the main contributions of the research of EMC in the past nearly 15 years, and reviewed the structure and function of EMC as well as its related diseases. We hope this review will promote further progress of research on EMC.
Collapse
Affiliation(s)
- Qi Zhu
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan, China
| | - Xianjun Zhu
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan, China
| | - Lin Zhang
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan, China
- Qinghai Provincial Key Laboratory of Tibetan Medicine Research, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining, Qinghai, China
| |
Collapse
|
16
|
DaRosa PA, Penchev I, Gumbin SC, Scavone F, Wąchalska M, Paulo JA, Ordureau A, Peter JJ, Kulathu Y, Harper JW, Becker T, Beckmann R, Kopito RR. UFM1 E3 ligase promotes recycling of 60S ribosomal subunits from the ER. Nature 2024; 627:445-452. [PMID: 38383785 DOI: 10.1038/s41586-024-07073-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Accepted: 01/15/2024] [Indexed: 02/23/2024]
Abstract
Reversible modification of target proteins by ubiquitin and ubiquitin-like proteins (UBLs) is widely used by eukaryotic cells to control protein fate and cell behaviour1. UFM1 is a UBL that predominantly modifies a single lysine residue on a single ribosomal protein, uL24 (also called RPL26), on ribosomes at the cytoplasmic surface of the endoplasmic reticulum (ER)2,3. UFM1 conjugation (UFMylation) facilitates the rescue of 60S ribosomal subunits (60S) that are released after ribosome-associated quality-control-mediated splitting of ribosomes that stall during co-translational translocation of secretory proteins into the ER3,4. Neither the molecular mechanism by which the UFMylation machinery achieves such precise target selection nor how this ribosomal modification promotes 60S rescue is known. Here we show that ribosome UFMylation in vivo occurs on free 60S and we present sequential cryo-electron microscopy snapshots of the heterotrimeric UFM1 E3 ligase (E3(UFM1)) engaging its substrate uL24. E3(UFM1) binds the L1 stalk, empty transfer RNA-binding sites and the peptidyl transferase centre through carboxy-terminal domains of UFL1, which results in uL24 modification more than 150 Å away. After catalysing UFM1 transfer, E3(UFM1) remains stably bound to its product, UFMylated 60S, forming a C-shaped clamp that extends all the way around the 60S from the transfer RNA-binding sites to the polypeptide tunnel exit. Our structural and biochemical analyses suggest a role for E3(UFM1) in post-termination release and recycling of the large ribosomal subunit from the ER membrane.
Collapse
Affiliation(s)
- Paul A DaRosa
- Department of Biology, Stanford University, Stanford, CA, USA
| | - Ivan Penchev
- Department of Biochemistry, Gene Center, University of Munich, Munich, Germany
| | | | | | - Magda Wąchalska
- Department of Biology, Stanford University, Stanford, CA, USA
| | - Joao A Paulo
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Alban Ordureau
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
- Cell Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Joshua J Peter
- Medical Research Council Protein Phosphorylation and Ubiquitylation Unit (MRC-PPU), School of Life Sciences, University of Dundee, Dundee, UK
| | - Yogesh Kulathu
- Medical Research Council Protein Phosphorylation and Ubiquitylation Unit (MRC-PPU), School of Life Sciences, University of Dundee, Dundee, UK
| | - J Wade Harper
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Thomas Becker
- Department of Biochemistry, Gene Center, University of Munich, Munich, Germany
| | - Roland Beckmann
- Department of Biochemistry, Gene Center, University of Munich, Munich, Germany.
| | - Ron R Kopito
- Department of Biology, Stanford University, Stanford, CA, USA.
| |
Collapse
|
17
|
Chamness LM, Kuntz CP, McKee AG, Penn WD, Hemmerich CM, Rusch DB, Woods H, Dyotima, Meiler J, Schlebach JP. Divergent Folding-Mediated Epistasis Among Unstable Membrane Protein Variants. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.08.25.554866. [PMID: 37662415 PMCID: PMC10473758 DOI: 10.1101/2023.08.25.554866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
Many membrane proteins are prone to misfolding, which compromises their functional expression at the plasma membrane. This is particularly true for the mammalian gonadotropin-releasing hormone receptor GPCRs (GnRHR). We recently demonstrated that evolutionary GnRHR modifications appear to have coincided with adaptive changes in cotranslational folding efficiency. Though protein stability is known to shape evolution, it is unclear how cotranslational folding constraints modulate the synergistic, epistatic interactions between mutations. We therefore compared the pairwise interactions formed by mutations that disrupt the membrane topology (V276T) or tertiary structure (W107A) of GnRHR. Using deep mutational scanning, we evaluated how the plasma membrane expression of these variants is modified by hundreds of secondary mutations. An analysis of 251 mutants in three genetic backgrounds reveals that V276T and W107A form distinct epistatic interactions that depend on both the severity and the mechanism of destabilization. V276T forms predominantly negative epistatic interactions with destabilizing mutations in soluble loops. In contrast, W107A forms positive interactions with mutations in both loops and transmembrane domains that reflect the diminishing impacts of the destabilizing mutations in variants that are already unstable. These findings reveal how epistasis is remodeled by conformational defects in membrane proteins and in unstable proteins more generally.
Collapse
Affiliation(s)
- Laura M. Chamness
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
| | - Charles P. Kuntz
- Department of Chemistry, Purdue University, West Lafayette, Indiana, USA
| | - Andrew G. McKee
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
| | - Wesley D. Penn
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
| | | | - Douglas B. Rusch
- Center for Genomics and Bioinformatics, Indiana University, Bloomington, Indiana, USA
| | - Hope Woods
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee, USA
- Chemical and Physical Biology Program, Vanderbilt University, Nashville, Tennessee, USA
| | - Dyotima
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
| | - Jens Meiler
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee, USA
- Institute for Drug Discovery, Leipzig University, Leipzig, SAC, Germany
| | - Jonathan P. Schlebach
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA
- Department of Chemistry, Purdue University, West Lafayette, Indiana, USA
| |
Collapse
|
18
|
Gamerdinger M, Deuerling E. Cotranslational sorting and processing of newly synthesized proteins in eukaryotes. Trends Biochem Sci 2024; 49:105-118. [PMID: 37919225 DOI: 10.1016/j.tibs.2023.10.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 09/28/2023] [Accepted: 10/06/2023] [Indexed: 11/04/2023]
Abstract
Ribosomes interact with a variety of different protein biogenesis factors that guide newly synthesized proteins to their native 3D shapes and cellular localization. Depending on the type of translated substrate, a distinct set of cotranslational factors must interact with the ribosome in a timely and coordinated manner to ensure proper protein biogenesis. While cytonuclear proteins require cotranslational maturation and folding factors, secretory proteins must be maintained in an unfolded state and processed cotranslationally by transport and membrane translocation factors. Here we explore the specific cotranslational processing steps for cytonuclear, secretory, and membrane proteins in eukaryotes and then discuss how the nascent polypeptide-associated complex (NAC) cotranslationally sorts these proteins into the correct protein biogenesis pathway.
Collapse
Affiliation(s)
- Martin Gamerdinger
- Department of Biology, Molecular Microbiology, University of Konstanz, 78457 Konstanz, Germany.
| | - Elke Deuerling
- Department of Biology, Molecular Microbiology, University of Konstanz, 78457 Konstanz, Germany.
| |
Collapse
|
19
|
Poerschke S, Oeljeklaus S, Cruz-Zaragoza LD, Schenzielorz A, Dahal D, Hillen HS, Das H, Kremer LS, Valpadashi A, Breuer M, Sattmann J, Richter-Dennerlein R, Warscheid B, Dennerlein S, Rehling P. Identification of TMEM126A as OXA1L-interacting protein reveals cotranslational quality control in mitochondria. Mol Cell 2024; 84:345-358.e5. [PMID: 38199007 PMCID: PMC10805001 DOI: 10.1016/j.molcel.2023.12.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 10/17/2023] [Accepted: 12/08/2023] [Indexed: 01/12/2024]
Abstract
Cellular proteostasis requires transport of polypeptides across membranes. Although defective transport processes trigger cytosolic rescue and quality control mechanisms that clear translocases and membranes from unproductive cargo, proteins that are synthesized within mitochondria are not accessible to these mechanisms. Mitochondrial-encoded proteins are inserted cotranslationally into the inner membrane by the conserved insertase OXA1L. Here, we identify TMEM126A as a OXA1L-interacting protein. TMEM126A associates with mitochondrial ribosomes and translation products. Loss of TMEM126A leads to the destabilization of mitochondrial translation products, triggering an inner membrane quality control process, in which newly synthesized proteins are degraded by the mitochondrial iAAA protease. Our data reveal that TMEM126A cooperates with OXA1L in protein insertion into the membrane. Upon loss of TMEM126A, the cargo-blocked OXA1L insertase complexes undergo proteolytic clearance by the iAAA protease machinery together with its cargo.
Collapse
Affiliation(s)
- Sabine Poerschke
- Institute for Cellular Biochemistry, University of Goettingen, 37073 Goettingen, Germany
| | - Silke Oeljeklaus
- Faculty of Chemistry and Pharmacy, Biochemistry II, Theodor Boveri-Institute, University of Würzburg, 97074 Wuerzburg, Germany
| | | | - Alexander Schenzielorz
- Institute for Biology II, Faculty for Biology, Functional Proteomics, University of Freiburg, 79104 Freiburg, Germany
| | - Drishan Dahal
- Institute for Cellular Biochemistry, University of Goettingen, 37073 Goettingen, Germany
| | - Hauke Sven Hillen
- Institute for Cellular Biochemistry, University of Goettingen, 37073 Goettingen, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Goettingen, Goettingen, Germany; Research Group Structure and Function of Molecular Machines, Max Planck Institute for Multidisciplinary Sciences, 37077 Goettingen, Germany
| | - Hirak Das
- Faculty of Chemistry and Pharmacy, Biochemistry II, Theodor Boveri-Institute, University of Würzburg, 97074 Wuerzburg, Germany
| | - Laura Sophie Kremer
- Institute for Cellular Biochemistry, University of Goettingen, 37073 Goettingen, Germany
| | - Anusha Valpadashi
- Institute for Cellular Biochemistry, University of Goettingen, 37073 Goettingen, Germany
| | - Mirjam Breuer
- Institute for Cellular Biochemistry, University of Goettingen, 37073 Goettingen, Germany
| | - Johannes Sattmann
- Institute for Cellular Biochemistry, University of Goettingen, 37073 Goettingen, Germany
| | - Ricarda Richter-Dennerlein
- Institute for Cellular Biochemistry, University of Goettingen, 37073 Goettingen, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Goettingen, Goettingen, Germany; Goettingen Center for Molecular Biosciences, University of Goettingen, 37077 Goettingen, Germany
| | - Bettina Warscheid
- Faculty of Chemistry and Pharmacy, Biochemistry II, Theodor Boveri-Institute, University of Würzburg, 97074 Wuerzburg, Germany; Cluster of Excellence CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Sven Dennerlein
- Institute for Cellular Biochemistry, University of Goettingen, 37073 Goettingen, Germany.
| | - Peter Rehling
- Institute for Cellular Biochemistry, University of Goettingen, 37073 Goettingen, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Goettingen, Goettingen, Germany; Goettingen Center for Molecular Biosciences, University of Goettingen, 37077 Goettingen, Germany; Fraunhofer Institute for Translational Medicine and Pharmacology ITMP, Translational Neuroinflammation and Automated Microscopy, Goettingen, Germany; Max Planck Institute for Multidisciplinary Sciences, 37077 Goettingen, Germany.
| |
Collapse
|
20
|
Wu H, Smalinskaitė L, Hegde RS. EMC rectifies the topology of multipass membrane proteins. Nat Struct Mol Biol 2024; 31:32-41. [PMID: 37957425 PMCID: PMC10803268 DOI: 10.1038/s41594-023-01120-6] [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: 04/25/2023] [Accepted: 09/08/2023] [Indexed: 11/15/2023]
Abstract
Most eukaryotic multipass membrane proteins are inserted into the membrane of the endoplasmic reticulum. Their transmembrane domains (TMDs) are thought to be inserted co-translationally as they emerge from a membrane-bound ribosome. Here we find that TMDs near the carboxyl terminus of mammalian multipass proteins are inserted post-translationally by the endoplasmic reticulum membrane protein complex (EMC). Site-specific crosslinking shows that the EMC's cytosol-facing hydrophilic vestibule is adjacent to a pre-translocated C-terminal tail. EMC-mediated insertion is mostly agnostic to TMD hydrophobicity, favored for short uncharged C-tails and stimulated by a preceding unassembled TMD bundle. Thus, multipass membrane proteins can be released by the ribosome-translocon complex in an incompletely inserted state, requiring a separate EMC-mediated post-translational insertion step to rectify their topology, complete biogenesis and evade quality control. This sequential co-translational and post-translational mechanism may apply to ~250 diverse multipass proteins, including subunits of the pentameric ion channel family that are crucial for neurotransmission.
Collapse
Affiliation(s)
- Haoxi Wu
- MRC Laboratory of Molecular Biology, Cambridge, UK
| | | | | |
Collapse
|
21
|
Guay KP, Ke H, Canniff NP, George GT, Eyles SJ, Mariappan M, Contessa JN, Gershenson A, Gierasch LM, Hebert DN. ER chaperones use a protein folding and quality control glyco-code. Mol Cell 2023; 83:4524-4537.e5. [PMID: 38052210 PMCID: PMC10790639 DOI: 10.1016/j.molcel.2023.11.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Revised: 10/18/2023] [Accepted: 11/07/2023] [Indexed: 12/07/2023]
Abstract
N-glycans act as quality control tags by recruiting lectin chaperones to assist protein maturation in the endoplasmic reticulum. The location and composition of N-glycans (glyco-code) are key to the chaperone-selection process. Serpins, a class of serine protease inhibitors, fold non-sequentially to achieve metastable active states. Here, the role of the glyco-code in assuring successful maturation and quality control of two human serpins, alpha-1 antitrypsin (AAT) and antithrombin III (ATIII), is described. We find that AAT, which has glycans near its N terminus, is assisted by early lectin chaperone binding. In contrast, ATIII, which has more C-terminal glycans, is initially helped by BiP and then later by lectin chaperones mediated by UGGT reglucosylation. UGGT action is increased for misfolding-prone disease variants, and these clients are preferentially glucosylated on their most C-terminal glycan. Our study illustrates how serpins utilize N-glycan presence, position, and composition to direct their proper folding, quality control, and trafficking.
Collapse
Affiliation(s)
- Kevin P Guay
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA; Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA, USA
| | - Haiping Ke
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA
| | - Nathan P Canniff
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA; Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA, USA
| | - Gracie T George
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA
| | - Stephen J Eyles
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA; Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA, USA; Institute for Applied Life Sciences, Mass Spectrometry Center, University of Massachusetts Amherst, Amherst, MA, USA
| | - Malaiyalam Mariappan
- Department of Cell Biology, Nanobiology Institute, Yale School of Medicine, West Haven, CT, USA
| | - Joseph N Contessa
- Departments of Therapeutic Radiology and Pharmacology, Yale School of Medicine, New Haven, CT, USA
| | - Anne Gershenson
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA; Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA, USA
| | - Lila M Gierasch
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA; Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA, USA; Department of Chemistry, University of Massachusetts Amherst, Amherst, MA, USA
| | - Daniel N Hebert
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA; Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA, USA.
| |
Collapse
|
22
|
Karki S, Javanainen M, Rehan S, Tranter D, Kellosalo J, Huiskonen JT, Happonen L, Paavilainen V. Molecular view of ER membrane remodeling by the Sec61/TRAP translocon. EMBO Rep 2023; 24:e57910. [PMID: 37983950 DOI: 10.15252/embr.202357910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 10/27/2023] [Accepted: 11/01/2023] [Indexed: 11/22/2023] Open
Abstract
Protein translocation across the endoplasmic reticulum (ER) membrane is an essential step during protein entry into the secretory pathway. The conserved Sec61 protein-conducting channel facilitates polypeptide translocation and coordinates cotranslational polypeptide-processing events. In cells, the majority of Sec61 is stably associated with a heterotetrameric membrane protein complex, the translocon-associated protein complex (TRAP), yet the mechanism by which TRAP assists in polypeptide translocation remains unknown. Here, we present the structure of the core Sec61/TRAP complex bound to a mammalian ribosome by cryogenic electron microscopy (cryo-EM). Ribosome interactions anchor the Sec61/TRAP complex in a conformation that renders the ER membrane locally thinner by significantly curving its lumenal leaflet. We propose that TRAP stabilizes the ribosome exit tunnel to assist nascent polypeptide insertion through Sec61 and provides a ratcheting mechanism into the ER lumen mediated by direct polypeptide interactions.
Collapse
Affiliation(s)
- Sudeep Karki
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Matti Javanainen
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Shahid Rehan
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
- Protein Biochemistry and Structural Biology, Omass Therapeutics Ltd, Oxford, UK
| | - Dale Tranter
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Juho Kellosalo
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Juha T Huiskonen
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Lotta Happonen
- Division of Infection Medicine, Department of Clinical Sciences, Lund University, Lund, Sweden
| | - Ville Paavilainen
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| |
Collapse
|
23
|
Zhou X, Yang Y, Wang G, Wang S, Sun D, Ou X, Lian Y, Li L. Molecular pathway of mitochondrial preprotein import through the TOM-TIM23 supercomplex. Nat Struct Mol Biol 2023; 30:1996-2008. [PMID: 37696957 DOI: 10.1038/s41594-023-01103-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Accepted: 08/18/2023] [Indexed: 09/13/2023]
Abstract
Over half of mitochondrial proteins are imported from the cytosol via the pre-sequence pathway, controlled by the TOM complex in the outer membrane and the TIM23 complex in the inner membrane. The mechanisms through which proteins are translocated via the TOM and TIM23 complexes remain unclear. Here we report the assembly of the active TOM-TIM23 supercomplex of Saccharomyces cerevisiae with translocating polypeptide substrates. Electron cryo-microscopy analyses reveal that the polypeptide substrates pass the TOM complex through the center of a Tom40 subunit, interacting with a glutamine-rich region. Structural and biochemical analyses show that the TIM23 complex contains a heterotrimer of the subunits Tim23, Tim17 and Mgr2. The polypeptide substrates are shielded from lipids by Mgr2 and Tim17, which creates a translocation pathway characterized by a negatively charged entrance and a central hydrophobic region. These findings reveal an unexpected pre-sequence pathway through the TOM-TIM23 supercomplex spanning the double membranes of mitochondria.
Collapse
Affiliation(s)
- Xueyin Zhou
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Yuqi Yang
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing, China
| | - Guopeng Wang
- School of Life Sciences, Peking University, Beijing, China
| | - Shanshan Wang
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing, China
| | - Dongjie Sun
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing, China
| | - Xiaomin Ou
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing, China
| | - Yuke Lian
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing, China
| | - Long Li
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing, China.
| |
Collapse
|
24
|
Kleizen B, de Mattos E, Papaioannou O, Monti M, Tartaglia GG, van der Sluijs P, Braakman I. Transmembrane Helices 7 and 8 Confer Aggregation Sensitivity to the Cystic Fibrosis Transmembrane Conductance Regulator. Int J Mol Sci 2023; 24:15741. [PMID: 37958724 PMCID: PMC10648718 DOI: 10.3390/ijms242115741] [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: 09/04/2023] [Revised: 10/18/2023] [Accepted: 10/19/2023] [Indexed: 11/15/2023] Open
Abstract
The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) is a large multi-spanning membrane protein that is susceptible to misfolding and aggregation. We have identified here the region responsible for this instability. Temperature-induced aggregation of C-terminally truncated versions of CFTR demonstrated that all truncations up to the second transmembrane domain (TMD2), including the R region, largely resisted aggregation. Limited proteolysis identified a folded structure that was prone to aggregation and consisted of TMD2 and at least part of the Regulatory Region R. Only when both TM7 (TransMembrane helix 7) and TM8 were present, TMD2 fragments became as aggregation-sensitive as wild-type CFTR, in line with increased thermo-instability of late CFTR nascent chains and in silico prediction of aggregation propensity. In accord, isolated TMD2 was degraded faster in cells than isolated TMD1. We conclude that TMD2 extended at its N-terminus with part of the R region forms a protease-resistant structure that induces heat instability in CFTR and may be responsible for its limited intracellular stability.
Collapse
Affiliation(s)
- Bertrand Kleizen
- Cellular Protein Chemistry, Bijvoet Centre for Biomolecular Research, Utrecht University, 3584 CH Utrecht, The Netherlands; (B.K.); (E.d.M.); (O.P.); (P.v.d.S.)
| | - Eduardo de Mattos
- Cellular Protein Chemistry, Bijvoet Centre for Biomolecular Research, Utrecht University, 3584 CH Utrecht, The Netherlands; (B.K.); (E.d.M.); (O.P.); (P.v.d.S.)
| | - Olga Papaioannou
- Cellular Protein Chemistry, Bijvoet Centre for Biomolecular Research, Utrecht University, 3584 CH Utrecht, The Netherlands; (B.K.); (E.d.M.); (O.P.); (P.v.d.S.)
| | - Michele Monti
- Center for Life Nano- & Neuro-Science, Fondazione Istituto Italiano di Tecnologia (IIT), 00161 Rome, Italy; (M.M.); (G.G.T.)
- Centre for Human Technologies (CHT), Istituto Italiano di Tecnologia (IIT), 16152 Genoa, Italy
| | - Gian Gaetano Tartaglia
- Center for Life Nano- & Neuro-Science, Fondazione Istituto Italiano di Tecnologia (IIT), 00161 Rome, Italy; (M.M.); (G.G.T.)
- Centre for Human Technologies (CHT), Istituto Italiano di Tecnologia (IIT), 16152 Genoa, Italy
| | - Peter van der Sluijs
- Cellular Protein Chemistry, Bijvoet Centre for Biomolecular Research, Utrecht University, 3584 CH Utrecht, The Netherlands; (B.K.); (E.d.M.); (O.P.); (P.v.d.S.)
| | - Ineke Braakman
- Cellular Protein Chemistry, Bijvoet Centre for Biomolecular Research, Utrecht University, 3584 CH Utrecht, The Netherlands; (B.K.); (E.d.M.); (O.P.); (P.v.d.S.)
| |
Collapse
|
25
|
Ghorashi T, Darvish H, Bakhtiari S, Tafakhori A, Kruer MC, Mozdarani H. A biallelic loss-of-function variant in TMEM147 causes profound intellectual disability and spasticity. Neurogenetics 2023; 24:311-316. [PMID: 37668766 DOI: 10.1007/s10048-023-00734-8] [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: 05/24/2023] [Accepted: 08/27/2023] [Indexed: 09/06/2023]
Abstract
Intellectual disability (ID), occurring in syndromic or non-syndromic forms, is the most common neurodevelopmental disorder. Although many cases are caused by single gene defects, ID is highly genetically heterogeneous. Biallelic variants in the transmembrane protein TMEM147 have recently been linked to intellectual disability with dysmorphic facial features. TMEM147 is believed to localize to the endoplasmic reticulum membrane and nuclear envelope and also involved in biogenesis of multi-pass membrane proteins. Here, we report two patients born to a consanguineous family with a novel loss-of-function variant; (NM_001242597.2:c.193-197del) in TMEM147 causing intellectual disability and spasticity. Whole exome sequencing and validating Sanger sequencing were utilized to confirm the identified causal variant. Our findings were in line with the previously described patients with TMEM147 variants manifesting intellectual disability as a major clinical sign but also featured spasticity as a phenotypic expansion. This study provides additional evidence for the pathogenicity of TMEM147 mutations in intellectual disability and expands the phenotypic and variant spectrum linked to this gene.
Collapse
Affiliation(s)
- Tahereh Ghorashi
- Department of Medical Genetics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Hossein Darvish
- Neuroscience Research Center, Faculty of Medicine, Golestan University of Medical Sciences, Gorgan, Iran
| | - Somayeh Bakhtiari
- Pediatric Movement Disorders Program, Division of Pediatric Neurology, Barrow Neurological Institute, Phoenix Children's Hospital, Phoenix, AZ, USA
- Departments of Child Health, Neurology, and Cellular & Molecular Medicine, and Program in Genetics, University of Arizona College of Medicine-Phoenix, Phoenix, AZ, USA
| | - Abbas Tafakhori
- Iranian Center of Neurological Research, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - Michael C Kruer
- Pediatric Movement Disorders Program, Division of Pediatric Neurology, Barrow Neurological Institute, Phoenix Children's Hospital, Phoenix, AZ, USA.
- Departments of Child Health, Neurology, and Cellular & Molecular Medicine, and Program in Genetics, University of Arizona College of Medicine-Phoenix, Phoenix, AZ, USA.
| | - Hossein Mozdarani
- Department of Medical Genetics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran.
| |
Collapse
|
26
|
Jung M, Zimmermann R. Quantitative Mass Spectrometry Characterizes Client Spectra of Components for Targeting of Membrane Proteins to and Their Insertion into the Membrane of the Human ER. Int J Mol Sci 2023; 24:14166. [PMID: 37762469 PMCID: PMC10532041 DOI: 10.3390/ijms241814166] [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: 08/09/2023] [Revised: 09/07/2023] [Accepted: 09/12/2023] [Indexed: 09/29/2023] Open
Abstract
To elucidate the redundancy in the components for the targeting of membrane proteins to the endoplasmic reticulum (ER) and/or their insertion into the ER membrane under physiological conditions, we previously analyzed different human cells by label-free quantitative mass spectrometry. The HeLa and HEK293 cells had been depleted of a certain component by siRNA or CRISPR/Cas9 treatment or were deficient patient fibroblasts and compared to the respective control cells by differential protein abundance analysis. In addition to clients of the SRP and Sec61 complex, we identified membrane protein clients of components of the TRC/GET, SND, and PEX3 pathways for ER targeting, and Sec62, Sec63, TRAM1, and TRAP as putative auxiliary components of the Sec61 complex. Here, a comprehensive evaluation of these previously described differential protein abundance analyses, as well as similar analyses on the Sec61-co-operating EMC and the characteristics of the topogenic sequences of the various membrane protein clients, i.e., the client spectra of the components, are reported. As expected, the analysis characterized membrane protein precursors with cleavable amino-terminal signal peptides or amino-terminal transmembrane helices as predominant clients of SRP, as well as the Sec61 complex, while precursors with more central or even carboxy-terminal ones were found to dominate the client spectra of the SND and TRC/GET pathways for membrane targeting. For membrane protein insertion, the auxiliary Sec61 channel components indeed share the client spectra of the Sec61 complex to a large extent. However, we also detected some unexpected differences, particularly related to EMC, TRAP, and TRAM1. The possible mechanistic implications for membrane protein biogenesis at the human ER are discussed and can be expected to eventually advance our understanding of the mechanisms that are involved in the so-called Sec61-channelopathies, resulting from deficient ER protein import.
Collapse
Affiliation(s)
| | - Richard Zimmermann
- Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany;
| |
Collapse
|
27
|
Njenga R, Boele J, Öztürk Y, Koch HG. Coping with stress: How bacteria fine-tune protein synthesis and protein transport. J Biol Chem 2023; 299:105163. [PMID: 37586589 PMCID: PMC10502375 DOI: 10.1016/j.jbc.2023.105163] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 08/08/2023] [Accepted: 08/10/2023] [Indexed: 08/18/2023] Open
Abstract
Maintaining a functional proteome under different environmental conditions is challenging for every organism, in particular for unicellular organisms, such as bacteria. In order to cope with changing environments and stress conditions, bacteria depend on strictly coordinated proteostasis networks that control protein production, folding, trafficking, and degradation. Regulation of ribosome biogenesis and protein synthesis are cornerstones of this cellular adaptation in all domains of life, which is rationalized by the high energy demand of both processes and the increased resistance of translationally silent cells against internal or external poisons. Reduced protein synthesis ultimately also reduces the substrate load for protein transport systems, which are required for maintaining the periplasmic, inner, and outer membrane subproteomes. Consequences of impaired protein transport have been analyzed in several studies and generally induce a multifaceted response that includes the upregulation of chaperones and proteases and the simultaneous downregulation of protein synthesis. In contrast, generally less is known on how bacteria adjust the protein targeting and transport machineries to reduced protein synthesis, e.g., when cells encounter stress conditions or face nutrient deprivation. In the current review, which is mainly focused on studies using Escherichia coli as a model organism, we summarize basic concepts on how ribosome biogenesis and activity are regulated under stress conditions. In addition, we highlight some recent developments on how stress conditions directly impair protein targeting to the bacterial membrane. Finally, we describe mechanisms that allow bacteria to maintain the transport of stress-responsive proteins under conditions when the canonical protein targeting pathways are impaired.
Collapse
Affiliation(s)
- Robert Njenga
- Faculty of Medicine, Institute for Biochemistry and Molecular Biology, ZBMZ, Albert-Ludwigs University Freiburg, Freiburg, Germany; Faculty of Biology, Albert-Ludwigs University Freiburg, Freiburg, Germany
| | - Julian Boele
- Faculty of Medicine, Institute for Biochemistry and Molecular Biology, ZBMZ, Albert-Ludwigs University Freiburg, Freiburg, Germany
| | - Yavuz Öztürk
- Faculty of Medicine, Institute for Biochemistry and Molecular Biology, ZBMZ, Albert-Ludwigs University Freiburg, Freiburg, Germany
| | - Hans-Georg Koch
- Faculty of Medicine, Institute for Biochemistry and Molecular Biology, ZBMZ, Albert-Ludwigs University Freiburg, Freiburg, Germany.
| |
Collapse
|
28
|
Li D, Rocha-Roa C, Schilling MA, Reinisch KM, Vanni S. Lipid scrambling is a general feature of protein insertases. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.01.555937. [PMID: 37693532 PMCID: PMC10491306 DOI: 10.1101/2023.09.01.555937] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
Glycerophospholipids are synthesized primarily in the cytosolic leaflet of the endoplasmic reticulum (ER) membrane and must be equilibrated between bilayer leaflets to allow the ER and membranes derived from it to grow. Lipid equilibration is facilitated by integral membrane proteins called "scramblases". These proteins feature a hydrophilic groove allowing the polar heads of lipids to traverse the hydrophobic membrane interior, similar to a credit-card moving through a reader. Nevertheless, despite their fundamental role in membrane expansion and dynamics, the identity of most scramblases has remained elusive. Here, combining biochemical reconstitution and molecular dynamics simulations, we show that lipid scrambling is a general feature of protein insertases, integral membrane proteins which insert polypeptide chains into membranes of the ER and organelles disconnected from vesicle trafficking. Our data indicate that lipid scrambling occurs in the same hydrophilic channel through which protein insertion takes place, and that scrambling is abolished in the presence of nascent polypeptide chains. We propose that protein insertases could have a so-far overlooked role in membrane dynamics as scramblases.
Collapse
Affiliation(s)
- Dazhi Li
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | | | - Matthew A Schilling
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Karin M Reinisch
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Stefano Vanni
- Department of Biology, University of Fribourg, Switzerland
| |
Collapse
|
29
|
Abstract
Protein translocases, such as the bacterial SecY complex, the Sec61 complex of the endoplasmic reticulum (ER) and the mitochondrial translocases, facilitate the transport of proteins across membranes. In addition, they catalyze the insertion of integral membrane proteins into the lipid bilayer. Several membrane insertases cooperate with these translocases, thereby promoting the topogenesis, folding and assembly of membrane proteins. Oxa1 and BamA family members serve as core components in the two major classes of membrane insertases. They facilitate the integration of proteins with α-helical transmembrane domains and of β-barrel proteins into lipid bilayers, respectively. Members of the Oxa1 family were initially found in the internal membranes of bacteria, mitochondria and chloroplasts. Recent studies, however, also identified several Oxa1-type insertases in the ER, where they serve as catalytically active core subunits in the ER membrane protein complex (EMC), the guided entry of tail-anchored (GET) and the GET- and EMC-like (GEL) complex. The outer membrane of bacteria, mitochondria and chloroplasts contain β-barrel proteins, which are inserted by members of the BamA family. In this Cell Science at a Glance article and the accompanying poster, we provide an overview of these different types of membrane insertases and discuss their function.
Collapse
Affiliation(s)
- Büsra Kizmaz
- Cell Biology, University of Kaiserslautern, Kaiserslautern 67663, Germany
| | | |
Collapse
|
30
|
Müller MBD, Kasturi P, Jayaraj GG, Hartl FU. Mechanisms of readthrough mitigation reveal principles of GCN1-mediated translational quality control. Cell 2023:S0092-8674(23)00587-1. [PMID: 37339632 PMCID: PMC10364623 DOI: 10.1016/j.cell.2023.05.035] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 05/17/2023] [Accepted: 05/24/2023] [Indexed: 06/22/2023]
Abstract
Readthrough into the 3' untranslated region (3' UTR) of the mRNA results in the production of aberrant proteins. Metazoans efficiently clear readthrough proteins, but the underlying mechanisms remain unknown. Here, we show in Caenorhabditis elegans and mammalian cells that readthrough proteins are targeted by a coupled, two-level quality control pathway involving the BAG6 chaperone complex and the ribosome-collision-sensing protein GCN1. Readthrough proteins with hydrophobic C-terminal extensions (CTEs) are recognized by SGTA-BAG6 and ubiquitylated by RNF126 for proteasomal degradation. Additionally, cotranslational mRNA decay initiated by GCN1 and CCR4/NOT limits the accumulation of readthrough products. Unexpectedly, selective ribosome profiling uncovered a general role of GCN1 in regulating translation dynamics when ribosomes collide at nonoptimal codons, enriched in 3' UTRs, transmembrane proteins, and collagens. GCN1 dysfunction increasingly perturbs these protein classes during aging, resulting in mRNA and proteome imbalance. Our results define GCN1 as a key factor acting during translation in maintaining protein homeostasis.
Collapse
Affiliation(s)
- Martin B D Müller
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Prasad Kasturi
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Gopal G Jayaraj
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
| | - F Ulrich Hartl
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany; Munich Cluster for Systems Neurology (SyNergy), Munich, Germany.
| |
Collapse
|
31
|
Cheng S, Li J, Xu M, Bao Q, Wu J, Sun P, Han B. TMEM147 Correlates with Immune Infiltration and Serve as a Potential Prognostic Biomarker in Hepatocellular Carcinoma. Anal Cell Pathol (Amst) 2023; 2023:4413049. [PMID: 37305689 PMCID: PMC10257544 DOI: 10.1155/2023/4413049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 05/06/2023] [Accepted: 05/23/2023] [Indexed: 06/13/2023] Open
Abstract
Background Hepatocellular carcinoma (HCC) is one of the most prevalent malignancies and is associated with high mortality. Transmembrane protein 147 (TMEM147) is a seven-transmembrane protein that may mediate immune regulation. However, the relevance of TMEM147 to immune regulation in HCC and the prognosis of HCC patients are unclear. Methods We analyzed TMEM147 expression in HCC by using the Wilcoxon rank-sum test. Real time quantitative PCR (RT-qPCR) and Western blot analysis of tumor tissues and cell lines were used to verify TMEM147 expression in HCC. The influence of TMEM147 on HCC prognosis was assessed using Kaplan-Meier analysis, Cox regression analysis, and a prognostic nomogram. The functions of the TMEM147-related differentially expressed genes (DEGs) were identified by Gene Ontology (GO)/Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses and gene set enrichment analysis (GSEA). In addition, we examined the associations between TMEM147 expression and immune infiltration using single-sample gene set enrichment analysis (ssGSEA) and immunofluorescence staining of HCC tissues. Results Our results showed that the expression of TMEM147 was significantly higher in human HCC tissues than in adjacent normal liver tissues, with similar findings in human HCC cell lines. High TMEM147 expression was correlated with T stage, pathological stage, histological grade, race, alpha-fetoprotein level, and vascular invasion in HCC. Moreover, we revealed that high TMEM147 expression was associated with shorter survival times and that TMEM147 could be a risk factor for overall survival, along with T stage, M stage, pathological stage, and tumor status. Mechanistic studies revealed that high TMEM147 expression was linked to the B lymphocyte, antigen response, IL6 signaling pathway, cell cycle, Kirsten rat sarcoma viral oncogene homolog (KRAS) signaling pathway, and myelocytomatosis oncogene (MYC) targets. Correspondingly, TMEM147 expression was positively associated with the infiltration of immune cells, including Th2 cells, follicular helper T cells, macrophages, and NK CD56 bright cells in HCC. Conclusions TMEM147 might be a biomarker for poor prognosis and is related to immune cell infiltration in HCC.
Collapse
Affiliation(s)
- Sheng Cheng
- Department of General Surgery, Tongren Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200336, China
- Key Laboratory for Translational Research and Innovative Therapeutics of Gastrointestinal Oncology, Hongqiao International Institute of Medicine, Tongren Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200336, China
| | - Jutang Li
- Key Laboratory for Translational Research and Innovative Therapeutics of Gastrointestinal Oncology, Hongqiao International Institute of Medicine, Tongren Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200336, China
| | - Ming Xu
- Department of General Surgery, Tongren Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200336, China
| | - Qun Bao
- Department of General Surgery, Tongren Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200336, China
| | - Jiaoxiang Wu
- Key Laboratory for Translational Research and Innovative Therapeutics of Gastrointestinal Oncology, Hongqiao International Institute of Medicine, Tongren Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200336, China
- Department of Clinical Laboratory, Tongren Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200336, China
| | - Peng Sun
- Department of General Surgery, Tongren Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200336, China
| | - Bo Han
- Department of General Surgery, Tongren Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200336, China
- Key Laboratory for Translational Research and Innovative Therapeutics of Gastrointestinal Oncology, Hongqiao International Institute of Medicine, Tongren Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200336, China
| |
Collapse
|
32
|
Bai L, Li H. Structural insights into the membrane chaperones for multi-pass membrane protein biogenesis. Curr Opin Struct Biol 2023; 79:102563. [PMID: 36863267 DOI: 10.1016/j.sbi.2023.102563] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2022] [Revised: 01/22/2023] [Accepted: 01/28/2023] [Indexed: 03/04/2023]
Abstract
Certain transmembrane α-helices of multi-pass membrane proteins line substrate transport paths or catalytic pockets and, therefore, are partially hydrophilic. Sec61 alone is insufficient to insert these less hydrophobic segments into the membrane and needs to work with dedicated membrane chaperones. Three such membrane chaperones have been described in the literature-the endoplasmic reticulum membrane protein complex (EMC), the TMCO1 complex, and the PAT complex. Recent structural studies on these membrane chaperones have revealed their overall architecture, multi-subunit assembly, putative substrate transmembrane helix-binding pockets, and cooperative mechanisms with the ribosome and Sec61 translocon. These structures are providing initial insights into the poorly understood processes of multi-pass membrane protein biogenesis.
Collapse
Affiliation(s)
- Lin Bai
- Department of Biochemistry and Biophysics, School of Basic Medical Sciences, Peking University, Beijing, 100083, China.
| | - Huilin Li
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, 49503, United States.
| |
Collapse
|
33
|
Overduin M, Kervin TA, Klarenbach Z, Adra TRC, Bhat RK. Comprehensive classification of proteins based on structures that engage lipids by COMPOSEL. Biophys Chem 2023; 295:106971. [PMID: 36801589 DOI: 10.1016/j.bpc.2023.106971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2022] [Accepted: 02/05/2023] [Indexed: 02/11/2023]
Abstract
Structures can now be predicted for any protein using programs like AlphaFold and Rosetta, which rely on a foundation of experimentally determined structures of architecturally diverse proteins. The accuracy of such artificial intelligence and machine learning (AI/ML) approaches benefits from the specification of restraints which assist in navigating the universe of folds to converge on models most representative of a given protein's physiological structure. This is especially pertinent for membrane proteins, with structures and functions that depend on their presence in lipid bilayers. Structures of proteins in their membrane environments could conceivably be predicted from AI/ML approaches with user-specificized parameters that describe each element of the architecture of a membrane protein accompanied by its lipid environment. We propose the Classification Of Membrane Proteins based On Structures Engaging Lipids (COMPOSEL), which builds on existing nomenclature types for monotopic, bitopic, polytopic and peripheral membrane proteins as well as lipids. Functional and regulatory elements are also defined in the scripts, as shown with membrane fusing synaptotagmins, multidomain PDZD8 and Protrudin proteins that recognize phosphoinositide (PI) lipids, the intrinsically disordered MARCKS protein, caveolins, the β barrel assembly machine (BAM), an adhesion G-protein coupled receptor (aGPCR) and two lipid modifying enzymes - diacylglycerol kinase DGKε and fatty aldehyde dehydrogenase FALDH. This demonstrates how COMPOSEL communicates lipid interactivity as well as signaling mechanisms and binding of metabolites, drug molecules, polypeptides or nucleic acids to describe the operations of any protein. Moreover COMPOSEL can be scaled to express how genomes encode membrane structures and how our organs are infiltrated by pathogens such as SARS-CoV-2.
Collapse
Affiliation(s)
- Michael Overduin
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada.
| | - Troy A Kervin
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada
| | | | - Trixie Rae C Adra
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada
| | - Rakesh K Bhat
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada
| |
Collapse
|
34
|
Hsieh LTH, Hall BS, Newcombe J, Mendum TA, Umrania Y, Deery MJ, Shi WQ, Salguero FJ, Simmonds RE. Mycolactone causes catastrophic Sec61-dependent loss of the endothelial glycocalyx and basement membrane: a new indirect mechanism driving tissue necrosis in Mycobacterium ulcerans infection. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.21.529382. [PMID: 36865118 PMCID: PMC9980099 DOI: 10.1101/2023.02.21.529382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
The drivers of tissue necrosis in Mycobacterium ulcerans infection (Buruli ulcer disease) have historically been ascribed solely to the directly cytotoxic action of the diffusible exotoxin, mycolactone. However, its role in the clinically-evident vascular component of disease aetiology remains poorly explained. We have now dissected mycolactone's effects on primary vascular endothelial cells in vitro and in vivo. We show that mycolactone-induced changes in endothelial morphology, adhesion, migration, and permeability are dependent on its action at the Sec61 translocon. Unbiased quantitative proteomics identified a profound effect on proteoglycans, driven by rapid loss of type II transmembrane proteins of the Golgi, including enzymes required for glycosaminoglycan (GAG) synthesis, combined with a reduction in the core proteins themselves. Loss of the glycocalyx is likely to be of particular mechanistic importance, since knockdown of galactosyltransferase II (beta-1,3-galactotransferase 6; B3Galt6), the GAG linker-building enzyme, phenocopied the permeability and phenotypic changes induced by mycolactone. Additionally, mycolactone depleted many secreted basement membrane components and microvascular basement membranes were disrupted in vivo. Remarkably, exogenous addition of laminin-511 reduced endothelial cell rounding, restored cell attachment and reversed the defective migration caused by mycolactone. Hence supplementing mycolactone-depleted extracellular matrix may be a future therapeutic avenue, to improve wound healing rates.
Collapse
Affiliation(s)
| | - Belinda S Hall
- Dept of Microbial Sciences, School of Bioscience and Medicine, University of Surrey
| | - Jane Newcombe
- Dept of Microbial Sciences, School of Bioscience and Medicine, University of Surrey
| | - Tom A Mendum
- Dept of Microbial Sciences, School of Bioscience and Medicine, University of Surrey
| | - Yagnesh Umrania
- Cambridge Centre for Proteomics, University of Cambridge, Cambridge, UK
| | - Michael J Deery
- Cambridge Centre for Proteomics, University of Cambridge, Cambridge, UK
| | - Wei Q Shi
- Department of Chemistry, Ball State University, Muncie, IN 47306, USA
| | | | - Rachel E Simmonds
- Dept of Microbial Sciences, School of Bioscience and Medicine, University of Surrey
| |
Collapse
|
35
|
Factors That Control the Force Needed to Unfold a Membrane Protein in Silico Depend on the Mode of Denaturation. Int J Mol Sci 2023; 24:ijms24032654. [PMID: 36768981 PMCID: PMC9917119 DOI: 10.3390/ijms24032654] [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: 12/30/2022] [Revised: 01/23/2023] [Accepted: 01/24/2023] [Indexed: 02/01/2023] Open
Abstract
Single-molecule force spectroscopy methods, such as AFM and magnetic tweezers, have proved extremely beneficial in elucidating folding pathways for soluble and membrane proteins. To identify factors that determine the force rupture levels in force-induced membrane protein unfolding, we applied our near-atomic-level Upside molecular dynamics package to study the vertical and lateral pulling of bacteriorhodopsin (bR) and GlpG, respectively. With our algorithm, we were able to selectively alter the magnitudes of individual interaction terms and identify that, for vertical pulling, hydrogen bond strength had the strongest effect, whereas other non-bonded protein and membrane-protein interactions had only moderate influences, except for the extraction of the last helix where the membrane-protein interactions had a stronger influence. The up-down topology of the transmembrane helices caused helices to be pulled out as pairs. The rate-limiting rupture event often was the loss of H-bonds and the ejection of the first helix, which then propagated tension to the second helix, which rapidly exited the bilayer. The pulling of the charged linkers across the membrane had minimal influence, as did changing the bilayer thickness. For the lateral pulling of GlpG, the rate-limiting rupture corresponded to the separation of the helices within the membrane, with the H-bonds generally being broken only afterward. Beyond providing a detailed picture of the rupture events, our study emphasizes that the pulling mode greatly affects the factors that determine the forces needed to unfold a membrane protein.
Collapse
|
36
|
Eisenack TJ, Trentini DB. Ending a bad start: Triggers and mechanisms of co-translational protein degradation. Front Mol Biosci 2023; 9:1089825. [PMID: 36660423 PMCID: PMC9846516 DOI: 10.3389/fmolb.2022.1089825] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Accepted: 12/15/2022] [Indexed: 01/05/2023] Open
Abstract
Proteins are versatile molecular machines that control and execute virtually all cellular processes. They are synthesized in a multilayered process requiring transfer of information from DNA to RNA and finally into polypeptide, with many opportunities for error. In addition, nascent proteins must successfully navigate a complex folding-energy landscape, in which their functional native state represents one of many possible outcomes. Consequently, newly synthesized proteins are at increased risk of misfolding and toxic aggregation. To maintain proteostasis-the state of proteome balance-cells employ a plethora of molecular chaperones that guide proteins along a productive folding pathway and quality control factors that direct misfolded species for degradation. Achieving the correct balance between folding and degradation therefore represents a fundamental task for the proteostasis network. While many chaperones act co-translationally, protein quality control is generally considered to be a post-translational process, as the majority of proteins will only achieve their final native state once translation is completed. Nevertheless, it has been observed that proteins can be ubiquitinated during synthesis. The extent and the relevance of co-translational protein degradation, as well as the underlying molecular mechanisms, remain areas of open investigation. Recent studies made seminal advances in elucidating ribosome-associated quality control processes, and how their loss of function can lead to proteostasis failure and disease. Here, we discuss current understanding of the situations leading to the marking of nascent proteins for degradation before synthesis is completed, and the emerging quality controls pathways engaged in this task in eukaryotic cells. We also highlight the methods used to study co-translational quality control.
Collapse
Affiliation(s)
- Tom Joshua Eisenack
- University of Cologne, Faculty of Medicine, University Hospital of Cologne, Center for Molecular Medicine Cologne (CMMC), Cologne, Germany
| | - Débora Broch Trentini
- University of Cologne, Faculty of Medicine, University Hospital of Cologne, Center for Molecular Medicine Cologne (CMMC), Cologne, Germany,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany,*Correspondence: Débora Broch Trentini,
| |
Collapse
|
37
|
Visualization of translation and protein biogenesis at the ER membrane. Nature 2023; 614:160-167. [PMID: 36697828 PMCID: PMC9892003 DOI: 10.1038/s41586-022-05638-5] [Citation(s) in RCA: 58] [Impact Index Per Article: 58.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Accepted: 12/07/2022] [Indexed: 01/26/2023]
Abstract
The dynamic ribosome-translocon complex, which resides at the endoplasmic reticulum (ER) membrane, produces a major fraction of the human proteome1,2. It governs the synthesis, translocation, membrane insertion, N-glycosylation, folding and disulfide-bond formation of nascent proteins. Although individual components of this machinery have been studied at high resolution in isolation3-7, insights into their interplay in the native membrane remain limited. Here we use cryo-electron tomography, extensive classification and molecular modelling to capture snapshots of mRNA translation and protein maturation at the ER membrane at molecular resolution. We identify a highly abundant classical pre-translocation intermediate with eukaryotic elongation factor 1a (eEF1a) in an extended conformation, suggesting that eEF1a may remain associated with the ribosome after GTP hydrolysis during proofreading. At the ER membrane, distinct polysomes bind to different ER translocons specialized in the synthesis of proteins with signal peptides or multipass transmembrane proteins with the translocon-associated protein complex (TRAP) present in both. The near-complete atomic model of the most abundant ER translocon variant comprising the protein-conducting channel SEC61, TRAP and the oligosaccharyltransferase complex A (OSTA) reveals specific interactions of TRAP with other translocon components. We observe stoichiometric and sub-stoichiometric cofactors associated with OSTA, which are likely to include protein isomerases. In sum, we visualize ER-bound polysomes with their coordinated downstream machinery.
Collapse
|
38
|
Guay KP, Williams RV, Hebert DN. Calnexin reveals a sugar-free taste within the lipid bilayer. EMBO J 2022; 41:e113003. [PMID: 36377534 PMCID: PMC9753440 DOI: 10.15252/embj.2022113003] [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: 11/07/2022] [Accepted: 11/08/2022] [Indexed: 11/16/2022] Open
Abstract
Maturation of membrane proteins is complicated by the need to fold in three distinct environments. While much is known about folding in the two aqueous milieus constituted by cytoplasm and ER lumen, our knowledge of the folding, arrangement, and quality control of transmembrane regions within the lipid bilayer, and its facilitation by molecular chaperones, is limited. New work by Bloemeke et al now reveals an expanded role of the ER chaperone calnexin acting within the lipid bilayer in a carbohydrate-independent manner.
Collapse
Affiliation(s)
- Kevin P Guay
- Department of Biochemistry and Molecular BiologyUniversity of MassachusettsAmherstMAUSA
- Program in Molecular and Cellular BiologyUniversity of MassachusettsAmherstMAUSA
| | - Robert V Williams
- Department of Biochemistry and Molecular BiologyUniversity of MassachusettsAmherstMAUSA
| | - Daniel N Hebert
- Department of Biochemistry and Molecular BiologyUniversity of MassachusettsAmherstMAUSA
- Program in Molecular and Cellular BiologyUniversity of MassachusettsAmherstMAUSA
| |
Collapse
|
39
|
Abstract
More than 30% of eukaryotic proteins contain domains that must translocate across or integrate into the endoplasmic reticulum (ER) membrane. With few exceptions, protein translocation and transmembrane domain integration at the ER require the conserved Sec61 translocon. Decades of studies have established a clear mechanistic model for how the Sec61 translocon functions. The biosynthesis of distinct subsets of proteins at the ER also involves accessory factors that interact with the Sec61 translocon and translocating nascent proteins. However, assigning specific functions to many translocon accessory factors has been a persistent challenge in the field. This Perspective discusses recent insights into mechanisms that promote protein biosynthesis at the ER through accessory factors that directly regulate the Sec61 translocon or chaperone nascent proteins within the ER membrane. These translocon accessory factor functions, and more still to be discovered, are essential for producing a diverse and high-fidelity proteome at the ER.
Collapse
Affiliation(s)
- Sichen Shao
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115,*Address correspondence to: Sichen Shao ()
| |
Collapse
|