51
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Farkas Á, De Laurentiis EI, Schwappach B. The natural history of Get3-like chaperones. Traffic 2020; 20:311-324. [PMID: 30972921 PMCID: PMC6593721 DOI: 10.1111/tra.12643] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Revised: 03/22/2019] [Accepted: 03/25/2019] [Indexed: 02/02/2023]
Abstract
Get3 in yeast or TRC40 in mammals is an ATPase that, in eukaryotes, is a central element of the GET or TRC pathway involved in the targeting of tail-anchored proteins. Get3 has also been shown to possess chaperone holdase activity. A bioinformatic assessment was performed across all domains of life on functionally important regions of Get3 including the TRC40-insert and the hydrophobic groove essential for tail-anchored protein binding. We find that such a hydrophobic groove is much more common in bacterial Get3 homologs than previously appreciated based on a directed comparison of bacterial ArsA and yeast Get3. Furthermore, our analysis shows that the region containing the TRC40-insert varies in length and methionine content to an unexpected extent within eukaryotes and also between different phylogenetic groups. In fact, since the TRC40-insert is present in all domains of life, we suggest that its presence does not automatically predict a tail-anchored protein targeting function. This opens up a new perspective on the function of organellar Get3 homologs in plants which feature the TRC40-insert but have not been demonstrated to function in tail-anchored protein targeting. Our analysis also highlights a large diversity of the ways Get3 homologs dimerize. Thus, based on the structural features of Get3 homologs, these proteins may have an unexplored functional diversity in all domains of life.
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Affiliation(s)
- Ákos Farkas
- Department of Molecular Biology, Göttingen University Medical Center, Göttingen, Germany
| | | | - Blanche Schwappach
- Department of Molecular Biology, Göttingen University Medical Center, Göttingen, Germany.,Max-Planck Institute for Biophysical Chemistry, Göttingen, Germany
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52
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O'Donnell JP, Phillips BP, Yagita Y, Juszkiewicz S, Wagner A, Malinverni D, Keenan RJ, Miller EA, Hegde RS. The architecture of EMC reveals a path for membrane protein insertion. eLife 2020; 9:e57887. [PMID: 32459176 PMCID: PMC7292650 DOI: 10.7554/elife.57887] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 05/26/2020] [Indexed: 12/29/2022] Open
Abstract
Approximately 25% of eukaryotic genes code for integral membrane proteins that are assembled at the endoplasmic reticulum. An abundant and widely conserved multi-protein complex termed EMC has been implicated in membrane protein biogenesis, but its mechanism of action is poorly understood. Here, we define the composition and architecture of human EMC using biochemical assays, crystallography of individual subunits, site-specific photocrosslinking, and cryo-EM reconstruction. Our results suggest that EMC's cytosolic domain contains a large, moderately hydrophobic vestibule that can bind a substrate's transmembrane domain (TMD). The cytosolic vestibule leads into a lumenally-sealed, lipid-exposed intramembrane groove large enough to accommodate a single substrate TMD. A gap between the cytosolic vestibule and intramembrane groove provides a potential path for substrate egress from EMC. These findings suggest how EMC facilitates energy-independent membrane insertion of TMDs, explain why only short lumenal domains are translocated by EMC, and constrain models of EMC's proposed chaperone function.
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Affiliation(s)
| | - Ben P Phillips
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | - Yuichi Yagita
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | | | | | | | - Robert J Keenan
- Department of Biochemistry and Molecular Biology, The University of ChicagoChicagoUnited States
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53
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Zhu X, Tang R, Wang S, Chen X, Hu J, Lei C, Huang Y, Wang H, Nie Z, Yao S. Protein@Inorganic Nanodumpling System for High-Loading Protein Delivery with Activatable Fluorescence and Magnetic Resonance Bimodal Imaging Capabilities. ACS NANO 2020; 14:2172-2182. [PMID: 31990525 DOI: 10.1021/acsnano.9b09024] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Efficient protein delivery into the target cell is highly desirable for protein therapeutics. Current approaches for protein delivery commonly suffer from low-loading protein capacity, poor specificity for target cells, and invisible protein release. Herein, we report a protein@inorganic nanodumpling (ND) system as an intracellular protein delivery platform. Similar to a traditional Chinese food, the dumpling, ND consists of a protein complex "filling" formed by metal-ion-directed self-assembly of protein cargos fused to histidine-rich green fluorescent proteins (H39GFPs), which are further encapsulated by an external surface "wrapper" of manganese dioxide (MnO2) via in situ biomineralization. This ND structure allows for a high loading capacity (>63 wt %) for protein cargos with enhanced stability. NDs can be targeted and internalized into cancer cells specifically through folic acid receptors by surface-tailored folic acid. The protein cargo release is in a bistimuli-responsive manner, triggered by an either reductive or acidic intracellular microenvironment. Moreover, the MnO2 nanowrapper is an efficient fluorescence quencher for inner fused GFPs and also a "switch-on" magnetic resonance imaging (MRI) agent via triggered release of Mn2+ ions, which enables activatable fluorescence/MRI bimodal imaging of protein release. Finally, the ND is highly potent and specific to deliver functional protein ribonuclease A (RNase A) into cultured target cells and the tumor site in a xenografted mouse model, eliminating the tumor cells with high therapeutic efficacy. Our approach provides a promising alternative to advance protein-based cancer therapeutics.
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Affiliation(s)
- Xiaohua Zhu
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology , Hunan University , Changsha 410082 , P. R. China
- Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education), College of Chemistry and Chemical Engineering , Hunan Normal University , Changsha 410081 , P. R. China
| | - Rui Tang
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology , Hunan University , Changsha 410082 , P. R. China
| | - Shigong Wang
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology , Hunan University , Changsha 410082 , P. R. China
| | - Xiaoye Chen
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology , Hunan University , Changsha 410082 , P. R. China
| | - Jiajun Hu
- College of Biology , Hunan University , Changsha 410082 , P. R. China
| | - Chunyang Lei
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology , Hunan University , Changsha 410082 , P. R. China
| | - Yan Huang
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology , Hunan University , Changsha 410082 , P. R. China
| | - Honghui Wang
- College of Biology , Hunan University , Changsha 410082 , P. R. China
| | - Zhou Nie
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology , Hunan University , Changsha 410082 , P. R. China
| | - Shouzhuo Yao
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology , Hunan University , Changsha 410082 , P. R. China
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54
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Ito K, Shimokawa-Chiba N, Chiba S. Sec translocon has an insertase-like function in addition to polypeptide conduction through the channel. F1000Res 2020; 8. [PMID: 32025287 PMCID: PMC6971846 DOI: 10.12688/f1000research.21065.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/17/2019] [Indexed: 11/20/2022] Open
Abstract
The Sec translocon provides a polypeptide-conducting channel, which is insulated from the hydrophobic lipidic environment of the membrane, for translocation of hydrophilic passenger polypeptides. Its lateral gate allows a downstream hydrophobic segment (stop-transfer sequence) to exit the channel laterally for integration into the lipid phase. We note that this channel model only partly accounts for the translocon function. The other essential role of translocon is to facilitate de novo insertion of the N-terminal topogenic segment of a substrate polypeptide into the membrane. Recent structural studies suggest that de novo insertion does not use the polypeptide-conducting channel; instead, it takes place directly at the lateral gate, which is prone to opening. We propose that the de novo insertion process, in concept, is similar to that of insertases (such as YidC in bacteria and EMC3 in eukaryotes), in which an intramembrane surface of the machinery provides the halfway point of insertion.
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Affiliation(s)
- Koreaki Ito
- Faculty of Life Sciences and Institute for Protein Dynamics, Kyoto Sangyo University, Kyoto, Japan
| | - Naomi Shimokawa-Chiba
- Faculty of Life Sciences and Institute for Protein Dynamics, Kyoto Sangyo University, Kyoto, Japan
| | - Shinobu Chiba
- Faculty of Life Sciences and Institute for Protein Dynamics, Kyoto Sangyo University, Kyoto, Japan
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55
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Telini BDP, Menoncin M, Bonatto D. Does Inter-Organellar Proteostasis Impact Yeast Quality and Performance During Beer Fermentation? Front Genet 2020; 11:2. [PMID: 32076433 PMCID: PMC7006503 DOI: 10.3389/fgene.2020.00002] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Accepted: 01/06/2020] [Indexed: 02/02/2023] Open
Abstract
During beer production, yeast generate ethanol that is exported to the extracellular environment where it accumulates. Depending on the initial carbohydrate concentration in the wort, the amount of yeast biomass inoculated, the fermentation temperature, and the yeast attenuation capacity, a high concentration of ethanol can be achieved in beer. The increase in ethanol concentration as a consequence of the fermentation of high gravity (HG) or very high gravity (VHG) worts promotes deleterious pleiotropic effects on the yeast cells. Moderate concentrations of ethanol (5% v/v) change the enzymatic kinetics of proteins and affect biological processes, such as the cell cycle and metabolism, impacting the reuse of yeast for subsequent fermentation. However, high concentrations of ethanol (> 5% v/v) dramatically alter protein structure, leading to unfolded proteins as well as amorphous protein aggregates. It is noteworthy that the effects of elevated ethanol concentrations generated during beer fermentation resemble those of heat shock stress, with similar responses observed in both situations, such as the activation of proteostasis and protein quality control mechanisms in different cell compartments, including endoplasmic reticulum (ER), mitochondria, and cytosol. Despite the extensive published molecular and biochemical data regarding the roles of proteostasis in different organelles of yeast cells, little is known about how this mechanism impacts beer fermentation and how different proteostasis mechanisms found in ER, mitochondria, and cytosol communicate with each other during ethanol/fermentative stress. Supporting this integrative view, transcriptome data analysis was applied using publicly available information for a lager yeast strain grown under beer production conditions. The transcriptome data indicated upregulation of genes that encode chaperones, co-chaperones, unfolded protein response elements in ER and mitochondria, ubiquitin ligases, proteasome components, N-glycosylation quality control pathway proteins, and components of processing bodies (p-bodies) and stress granules (SGs) during lager beer fermentation. Thus, the main purpose of this hypothesis and theory manuscript is to provide a concise picture of how inter-organellar proteostasis mechanisms are connected with one another and with biological processes that may modulate the viability and/or vitality of yeast populations during HG/VHG beer fermentation and serial repitching.
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Affiliation(s)
- Bianca de Paula Telini
- Brewing Yeast Research Group, Centro de Biotecnologia da UFRGS, Departamento de Biologia Molecular e Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil
| | - Marcelo Menoncin
- Brewing Yeast Research Group, Centro de Biotecnologia da UFRGS, Departamento de Biologia Molecular e Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil
| | - Diego Bonatto
- Brewing Yeast Research Group, Centro de Biotecnologia da UFRGS, Departamento de Biologia Molecular e Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil
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56
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Abstract
Due to their topology tail-anchored (TA) proteins must target to the membrane independently of the co-translational route defined by the signal sequence recognition particle (SRP), its receptor and the translocon Sec61. More than a decade of work has extensively characterized a highly conserved pathway, the yeast GET or mammalian TRC40 pathway, which is capable of countering the biogenetic challenge posed by the C-terminal TA anchor. In this review we briefly summarize current models of this targeting route and focus on emerging aspects such as the intricate interplay with the proteostatic network of cells and with other targeting pathways. Importantly, we consider the lessons provided by the in vivo analysis of the pathway in different model organisms and by the consideration of its full client spectrum in more recent studies. This analysis of the state of the field highlights directions in which the current models may be experimentally probed and conceptually extended.
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Affiliation(s)
- Nica Borgese
- Institute of Neuroscience and BIOMETRA Department, Consiglio Nazionale delle Ricerche and Università degli Studi di Milano, via Vanvitelli 32, 20129, Milan, Italy.
| | - Javier Coy-Vergara
- Department of Molecular Biology, University of Göttingen Medical Centre, Humboldtallee 23, 37073, Göttingen, Germany
| | - Sara Francesca Colombo
- Institute of Neuroscience and BIOMETRA Department, Consiglio Nazionale delle Ricerche and Università degli Studi di Milano, via Vanvitelli 32, 20129, Milan, Italy
| | - Blanche Schwappach
- Department of Molecular Biology, University of Göttingen Medical Centre, Humboldtallee 23, 37073, Göttingen, Germany.
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57
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Dearborn AD, Marcotrigiano J. Hepatitis C Virus Structure: Defined by What It Is Not. Cold Spring Harb Perspect Med 2020; 10:cshperspect.a036822. [PMID: 31501263 DOI: 10.1101/cshperspect.a036822] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Hepatitis C virus (HCV) represents an important and growing public health problem, chronically infecting an estimated 70 million people worldwide. This blood-borne pathogen is generating a new wave of infections in the United States, associated with increasing intravenous drug use over the last decade. In most cases, HCV establishes a chronic infection, sometimes causing cirrhosis, end-stage liver disease, and hepatocellular carcinoma. Although a curative therapy exists, it is extremely expensive and provides no barrier to reinfection; therefore, a vaccine is urgently needed. The virion is asymmetric and heterogeneous with the buoyancy and protein content similar to low-density lipoparticles. Core protein is unstructured, and of the two envelope glycoproteins, E1 and E2, the function of E1 remains enigmatic. E2 is responsible for specifically binding host receptors CD81 and scavenger receptor class B type I (SR-BI). This review will focus on structural progress on HCV virion, core protein, envelope glycoproteins, and specific host receptors.
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Affiliation(s)
- Altaira D Dearborn
- The Protein Expression Laboratory, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.,Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Joseph Marcotrigiano
- The Protein Expression Laboratory, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
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58
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Russo BC, Duncan JK, Wiscovitch AL, Hachey AC, Goldberg MB. Activation of Shigella flexneri type 3 secretion requires a host-induced conformational change to the translocon pore. PLoS Pathog 2019; 15:e1007928. [PMID: 31725799 PMCID: PMC6879154 DOI: 10.1371/journal.ppat.1007928] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2019] [Revised: 11/26/2019] [Accepted: 09/30/2019] [Indexed: 12/17/2022] Open
Abstract
Type 3 secretion systems (T3SSs) are conserved bacterial nanomachines that inject virulence proteins (effectors) into eukaryotic cells during infection. Due to their ability to inject heterologous proteins into human cells, these systems are being developed as therapeutic delivery devices. The T3SS assembles a translocon pore in the plasma membrane and then docks onto the pore. Docking activates effector secretion through the pore and into the host cytosol. Here, using Shigella flexneri, a model pathogen for the study of type 3 secretion, we determined the molecular mechanisms by which host intermediate filaments trigger docking and enable effector secretion. We show that the interaction of intermediate filaments with the translocon pore protein IpaC changed the pore's conformation in a manner that was required for docking. Intermediate filaments repositioned residues of the Shigella pore protein IpaC that are located on the surface of the pore and in the pore channel. Restricting these conformational changes blocked docking in an intermediate filament-dependent manner. These data demonstrate that a host-induced conformational change to the pore enables T3SS docking and effector secretion, providing new mechanistic insight into the regulation of type 3 secretion.
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Affiliation(s)
- Brian C. Russo
- Center for Bacterial Pathogenesis, Department of Medicine, Division of Infectious Diseases, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Microbiology, Blavatnik Institute, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jeffrey K. Duncan
- Center for Bacterial Pathogenesis, Department of Medicine, Division of Infectious Diseases, Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - Alexandra L. Wiscovitch
- Center for Bacterial Pathogenesis, Department of Medicine, Division of Infectious Diseases, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Research Scholar Initiative, The Graduate School of Arts and Sciences, Harvard University, Cambridge, Massachusetts, United States of America
| | - Austin C. Hachey
- Center for Bacterial Pathogenesis, Department of Medicine, Division of Infectious Diseases, Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - Marcia B. Goldberg
- Center for Bacterial Pathogenesis, Department of Medicine, Division of Infectious Diseases, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Microbiology, Blavatnik Institute, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
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59
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Shan SO. Guiding tail-anchored membrane proteins to the endoplasmic reticulum in a chaperone cascade. J Biol Chem 2019; 294:16577-16586. [PMID: 31575659 PMCID: PMC6851334 DOI: 10.1074/jbc.rev119.006197] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Newly synthesized integral membrane proteins must traverse the aqueous cytosolic environment before arrival at their membrane destination and are prone to aggregation, misfolding, and mislocalization during this process. The biogenesis of integral membrane proteins therefore poses acute challenges to protein homeostasis within a cell and requires the action of effective molecular chaperones. Chaperones that mediate membrane protein targeting not only need to protect the nascent transmembrane domains from improper exposure in the cytosol, but also need to accurately select client proteins and actively guide their clients to the appropriate target membrane. The mechanisms by which cellular chaperones work together to coordinate this complex process are only beginning to be delineated. Here, we summarize recent advances in studies of the tail-anchored membrane protein targeting pathway, which revealed a network of chaperones, cochaperones, and targeting factors that together drive and regulate this essential process. This pathway is emerging as an excellent model system to decipher the mechanism by which molecular chaperones overcome the multiple challenges during post-translational membrane protein biogenesis and to gain insights into the functional organization of multicomponent chaperone networks.
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Affiliation(s)
- Shu-Ou Shan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125
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60
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Abstract
One-fourth of eukaryotic genes code for integral membrane proteins, nearly all of which are inserted and assembled at the endoplasmic reticulum (ER). The defining feature of membrane proteins is one or more transmembrane domains (TMDs). During membrane protein biogenesis, TMDs are selectively recognized, shielded, and chaperoned into the lipid bilayer, where they often assemble with other TMDs. If maturation fails, exposed TMDs serve as a cue for engagement of degradation pathways. Thus, TMD-recognition factors in the cytosol and ER are essential for membrane protein biogenesis and quality control. Here, we discuss the growing assortment of cytosolic and membrane-embedded TMD-recognition factors, the pathways within which they operate, and mechanistic principles of recognition.
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61
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Carvalho HJF, Del Bondio A, Maltecca F, Colombo SF, Borgese N. The WRB Subunit of the Get3 Receptor is Required for the Correct Integration of its Partner CAML into the ER. Sci Rep 2019; 9:11887. [PMID: 31417168 PMCID: PMC6695381 DOI: 10.1038/s41598-019-48363-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 08/02/2019] [Indexed: 11/24/2022] Open
Abstract
Calcium-modulating cyclophilin ligand (CAML), together with Tryptophan rich basic protein (WRB, Get1 in yeast), constitutes the mammalian receptor for the Transmembrane Recognition Complex subunit of 40 kDa (TRC40, Get3 in yeast), a cytosolic ATPase with a central role in the post-translational targeting pathway of tail-anchored (TA) proteins to the endoplasmic reticulum (ER) membrane. CAML has also been implicated in other cell-specific processes, notably in immune cell survival, and has been found in molar excess over WRB in different cell types. Notwithstanding the stoichiometric imbalance, WRB and CAML depend strictly on each other for expression. Here, we investigated the mechanism by which WRB impacts CAML levels. We demonstrate that CAML, generated in the presence of sufficient WRB levels, is inserted into the ER membrane with three transmembrane segments (TMs) in its C-terminal region. By contrast, without sufficient levels of WRB, CAML fails to adopt this topology, and is instead incompletely integrated to generate two aberrant topoforms; these congregate in ER-associated clusters and are degraded by the proteasome. Our results suggest that WRB, a member of the recently proposed Oxa1 superfamily, acts catalytically to assist the topogenesis of CAML and may have wider functions in membrane biogenesis than previously appreciated.
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Affiliation(s)
- Hugo J F Carvalho
- Consiglio Nazionale delle Ricerche Institute of Neuroscience and BIOMETRA Department, Università degli Studi di Milano, I-20129, Milan, Italy.,Institute of Bioengineering, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland
| | - Andrea Del Bondio
- Division of Neuroscience, Ospedale San Raffaele, I-20132, Milan, Italy
| | | | - Sara F Colombo
- Consiglio Nazionale delle Ricerche Institute of Neuroscience and BIOMETRA Department, Università degli Studi di Milano, I-20129, Milan, Italy.
| | - Nica Borgese
- Consiglio Nazionale delle Ricerche Institute of Neuroscience and BIOMETRA Department, Università degli Studi di Milano, I-20129, Milan, Italy.
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62
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Lin TW, Chen CC, Wu SM, Chang YC, Li YC, Su YW, Hsiao CD, Chang HY. Structural analysis of chloroplast tail-anchored membrane protein recognition by ArsA1. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2019; 99:128-143. [PMID: 30891827 DOI: 10.1111/tpj.14316] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2018] [Revised: 02/26/2019] [Accepted: 03/11/2019] [Indexed: 06/09/2023]
Abstract
In mammals and yeast, tail-anchored (TA) membrane proteins destined for the post-translational pathway are safely delivered to the endoplasmic reticulum (ER) membrane by a well-known targeting factor, TRC40/Get3. In contrast, the underlying mechanism for translocation of TA proteins in plants remains obscure. How this unique eukaryotic membrane-trafficking system correctly distinguishes different subsets of TA proteins destined for various organelles, including mitochondria, chloroplasts and the ER, is a key question of long standing. Here, we present crystal structures of algal ArsA1 (the Get3 homolog) in a distinct nucleotide-free open state and bound to adenylyl-imidodiphosphate. This approximately 80-kDa protein possesses a monomeric architecture, with two ATPase domains in a single polypeptide chain. It is capable of binding chloroplast (TOC34 and TOC159) and mitochondrial (TOM7) TA proteins based on features of its transmembrane domain as well as the regions immediately before and after the transmembrane domain. Several helices located above the TA-binding groove comprise the interlocking hook-like motif implicated by mutational analyses in TA substrate recognition. Our data provide insights into the molecular basis of the highly specific selectivity of interactions of algal ArsA1 with the correct sets of TA substrates before membrane targeting in plant cells.
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Affiliation(s)
- Tai-Wen Lin
- Molecular and Cell Biology, International Graduate Program, Academia Sinica and Graduate Institute of Life Science, National Defense Medical Center, Taipei, Taiwan
- Institute of Molecular Biology, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei, 11529, Taiwan
| | - Chi-Chih Chen
- Department of Marine Biotechnology and Resources, National Sun Yat-sen University, Kaohsiung, 80424, Taiwan
- The Asia-Pacific Ocean Research Center, National Sun Yat-sen University, Kaohsiung, 80424, Taiwan
- Doctoral Degree Program in Marine Biotechnology, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei, 11529, Taiwan
- Doctoral Degree Program in Marine Biotechnology, National Sun Yat-Sen University, 70 Lien-Hai Road, Kaohsiung, 80424, Taiwan
| | - Shu-Mei Wu
- Department of Marine Biotechnology and Resources, National Sun Yat-sen University, Kaohsiung, 80424, Taiwan
| | - Yu-Ching Chang
- Department of Marine Biotechnology and Resources, National Sun Yat-sen University, Kaohsiung, 80424, Taiwan
| | - Yi-Chuan Li
- Molecular and Cell Biology, International Graduate Program, Academia Sinica and Graduate Institute of Life Science, National Defense Medical Center, Taipei, Taiwan
| | - Yu-Wang Su
- Department of Marine Biotechnology and Resources, National Sun Yat-sen University, Kaohsiung, 80424, Taiwan
| | - Chwan-Deng Hsiao
- Molecular and Cell Biology, International Graduate Program, Academia Sinica and Graduate Institute of Life Science, National Defense Medical Center, Taipei, Taiwan
- Institute of Molecular Biology, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei, 11529, Taiwan
- Doctoral Degree Program in Marine Biotechnology, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei, 11529, Taiwan
| | - Hsin-Yang Chang
- Department of Marine Biotechnology and Resources, National Sun Yat-sen University, Kaohsiung, 80424, Taiwan
- The Asia-Pacific Ocean Research Center, National Sun Yat-sen University, Kaohsiung, 80424, Taiwan
- Doctoral Degree Program in Marine Biotechnology, National Sun Yat-Sen University, 70 Lien-Hai Road, Kaohsiung, 80424, Taiwan
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63
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Bodensohn US, Simm S, Fischer K, Jäschke M, Groß LE, Kramer K, Ehmann C, Rensing SA, Ladig R, Schleiff E. The intracellular distribution of the components of the GET system in vascular plants. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1866:1650-1662. [PMID: 31233800 DOI: 10.1016/j.bbamcr.2019.06.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2019] [Revised: 06/17/2019] [Accepted: 06/19/2019] [Indexed: 12/16/2022]
Abstract
The guided entry of tail-anchored proteins (GET) pathway facilitates targeting and insertion of tail-anchored proteins into membranes. In plants, such a protein insertion machinery for the endoplasmic reticulum as well as constituents within mitochondrial and chloroplasts were discovered. Previous phylogenetic analysis revealed that Get3 sequences of Embryophyta form two clades representing cytosolic ("a") and organellar ("bc") GET3 homologs, respectively. Cellular fractionation of Arabidopsis thaliana seedlings and usage of the self-assembly GFP system in protoplasts verified the cytosolic (ATGet3a), plastidic (ATGet3b) and mitochondrial (ATGet3c) localization of the different homologs. The identified plant homologs of Get1 and Get4 in A. thaliana are localized in ER and cytosol, respectively, implicating a degree of conservation of the GET pathway in A. thaliana. Transient expression of Get3 homologs of Solanum lycopersicum, Medicago × varia or Physcomitrella patens with the self-assembly GFP technique in homologous and heterologous systems verified that multiple Get3 homologs with differing subcellular localizations are common in plants. Chloroplast localized Get3 homologs were detected in all tested plant systems. In contrast, mitochondrial localized Get3 homologs were not identified in S. lycopersicum, or P. patens, while we confirmed on the example of A. thaliana proteins that mitochondrial localized Get3 proteins are properly targeted in S. lycopersicum as well.
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Affiliation(s)
- Uwe S Bodensohn
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Stefan Simm
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany; Frankfurt Institute of Advanced Studies, Ruth-Moufang-Straße 1, D-60438 Frankfurt, Germany
| | - Ken Fischer
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Michelle Jäschke
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Lucia E Groß
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Katharina Kramer
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Christian Ehmann
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Stefan A Rensing
- Faculty of Biology, University of Marburg, Karl-von-Frisch-Str. 8, D-35043 Marburg, Germany
| | - Roman Ladig
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Enrico Schleiff
- Institute for Molecular Biosciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany; Buchman Institute for Molecular Life Sciences, Goethe University Frankfurt am Main, Max-von-Laue Str. 15, D-60438 Frankfurt, Germany; Frankfurt Institute of Advanced Studies, Ruth-Moufang-Straße 1, D-60438 Frankfurt, Germany.
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Topological Analysis of the Type 3 Secretion System Translocon Pore Protein IpaC following Its Native Delivery to the Plasma Membrane during Infection. mBio 2019; 10:mBio.00877-19. [PMID: 31138750 PMCID: PMC6538787 DOI: 10.1128/mbio.00877-19] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The type 3 secretion system (T3SS) is a nanomachine required for virulence of many bacterial pathogens that infect humans. The system delivers bacterial virulence proteins into the cytosol of human cells, where the virulence proteins promote bacterial infection. The T3SS forms a translocon pore in the membranes of target cells. This pore is the portal through which bacterial virulence proteins are delivered by the T3SS into the eukaryotic cytosol. The pore also regulates secretion of these virulence proteins. Our work defines the topology of translocon pore proteins in their native context during infection, resolves previously conflicting reports about the topology of the Shigella translocon pore protein IpaC, and provides new insights into how interactions of the pore with the T3SS likely produce signals that activate secretion of virulence proteins. Many Gram-negative bacterial pathogens require a type 3 secretion system (T3SS) to deliver effector proteins into eukaryotic cells. Contact of the tip complex of the T3SS with a target eukaryotic cell initiates secretion of the two bacterial proteins that assemble into the translocon pore in the plasma membrane. The translocon pore functions to regulate effector protein secretion and is the conduit for effector protein translocation across the plasma membrane. To generate insights into how the translocon pore regulates effector protein secretion, we defined the topology of the Shigella translocon pore protein IpaC in the plasma membrane following its native delivery by the T3SS. Using single cysteine substitution mutagenesis and site-directed labeling with a membrane-impermeant chemical probe, we mapped residues accessible from the extracellular surface of the cell. Our data support a model in which the N terminus of IpaC is extracellular and the C terminus of IpaC is intracellular. These findings resolve previously conflicting data on IpaC topology that were based on nonnative delivery of IpaC to membranes. Salmonella enterica serovar Typhimurium also requires the T3SS for effector protein delivery into eukaryotic cells. Although the sequence of IpaC is closely related to the Salmonella translocon pore protein SipC, the two proteins have unique functional attributes during infection. We showed a similar overall topology for SipC and IpaC and identified subtle topological differences between their transmembrane α-helixes and C-terminal regions. Together, our data suggest that topological differences among distinct translocon pore proteins may dictate organism-specific functional differences of the T3SSs during infection.
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65
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Tye BW, Commins N, Ryazanova LV, Wühr M, Springer M, Pincus D, Churchman LS. Proteotoxicity from aberrant ribosome biogenesis compromises cell fitness. eLife 2019; 8:43002. [PMID: 30843788 PMCID: PMC6453566 DOI: 10.7554/elife.43002] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Accepted: 03/06/2019] [Indexed: 12/31/2022] Open
Abstract
To achieve maximal growth, cells must manage a massive economy of ribosomal proteins (r-proteins) and RNAs (rRNAs) to produce thousands of ribosomes every minute. Although ribosomes are essential in all cells, natural disruptions to ribosome biogenesis lead to heterogeneous phenotypes. Here, we model these perturbations in Saccharomyces cerevisiae and show that challenges to ribosome biogenesis result in acute loss of proteostasis. Imbalances in the synthesis of r-proteins and rRNAs lead to the rapid aggregation of newly synthesized orphan r-proteins and compromise essential cellular processes, which cells alleviate by activating proteostasis genes. Exogenously bolstering the proteostasis network increases cellular fitness in the face of challenges to ribosome assembly, demonstrating the direct contribution of orphan r-proteins to cellular phenotypes. We propose that ribosome assembly is a key vulnerability of proteostasis maintenance in proliferating cells that may be compromised by diverse genetic, environmental, and xenobiotic perturbations that generate orphan r-proteins. Cells are made up of thousands of different proteins that perform unique roles required for life. To create all of these proteins, cells use machines called ribosomes that are partly formed of elements known as r-proteins. When cells grow and divide, the ribosomes have to make copies of themselves through a process called ribosome biogenesis. Although all cells need ribosomes, certain types of cells are especially sensitive to events that interfere with ribosome biogenesis. For example, patients that have mutations in genes needed for ribosome biogenesis produce fewer red blood cells, but their other cells and tissues are mostly healthy. It is not clear why some cells are more sensitive than others. Ribosome biogenesis is very similar between different organisms, so researchers often use budding yeast as a model to study the process. Here, Tye et al. used genetic and chemical tools to interfere with ribosome biogenesis on short time scales, which made it possible to detect early on what was going wrong in the cells. The experiments found that when ribosome biogenesis was disrupted, r-proteins that were waiting to be assembled into ribosomes quickly stuck to one another and formed clumps that reduced the ability of the yeast cells to grow. The cells responded by switching on a protein called Hsf1, which restored their ability to grow. Yeast cells that were growing quickly, and therefore making more ribosomes, were more sensitive to abnormal ribosome biogenesis than slow-growing cells. These results indicate that how actively a cell is growing, and its ability to cope with r-proteins sticking together, may in part explain why certain cells are more vulnerable to events that interfere with ribosome biogenesis. Since human cells also have Hsf1, future experiments could investigate whether turning it on might also protect fast-growing human cells from such events.
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Affiliation(s)
- Blake W Tye
- Department of Genetics, Harvard Medical School, Boston, United States.,Program in Chemical Biology, Harvard University, Cambridge, United States
| | - Nicoletta Commins
- Department of Systems Biology, Harvard Medical School, Boston, United States
| | - Lillia V Ryazanova
- Department of Molecular Biology, Princeton University, Princeton, United States.,Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, United States
| | - Martin Wühr
- Department of Molecular Biology, Princeton University, Princeton, United States.,Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, United States
| | - Michael Springer
- Department of Systems Biology, Harvard Medical School, Boston, United States
| | - David Pincus
- Whitehead Institute for Biomedical Research, Cambridge, United States.,Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, United States.,Center for Physics of Evolving Systems, University of Chicago, Chicago, United States
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66
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Chitwood PJ, Hegde RS. The Role of EMC during Membrane Protein Biogenesis. Trends Cell Biol 2019; 29:371-384. [PMID: 30826214 DOI: 10.1016/j.tcb.2019.01.007] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Revised: 01/27/2019] [Accepted: 01/28/2019] [Indexed: 12/11/2022]
Abstract
Ten years ago, high-throughput genetic interaction analyses revealed an abundant and widely conserved protein complex residing in the endoplasmic reticulum (ER) membrane. Dubbed the ER membrane protein complex (EMC), its disruption has since been found to affect wide-ranging processes, including protein trafficking, organelle communication, ER stress, viral maturation, lipid homeostasis, and others. However, its molecular function has remained enigmatic. Recent studies suggest a role for EMC during membrane protein biogenesis. Biochemical reconstitution experiments show that EMC can directly mediate the insertion of transmembrane domains (TMDs) into the lipid bilayer. Given the large proportion of genes encoding membrane proteins, a central role for EMC as a TMD insertion factor can explain its high abundance, wide conservation, and pleiotropic phenotypes.
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Affiliation(s)
- Patrick J Chitwood
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB20QH, UK
| | - Ramanujan S Hegde
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB20QH, UK.
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67
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Targeting of LRRC59 to the Endoplasmic Reticulum and the Inner Nuclear Membrane. Int J Mol Sci 2019; 20:ijms20020334. [PMID: 30650545 PMCID: PMC6359192 DOI: 10.3390/ijms20020334] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 01/08/2019] [Accepted: 01/10/2019] [Indexed: 01/12/2023] Open
Abstract
LRRC59 (leucine-rich repeat-containing protein 59) is a tail-anchored protein with a single transmembrane domain close to its C-terminal end that localizes to the endoplasmic reticulum (ER) and the nuclear envelope. Here, we investigate the mechanisms of membrane integration of LRRC59 and its targeting to the inner nuclear membrane (INM). Using purified microsomes, we show that LRRC59 can be post-translationally inserted into ER-derived membranes. The TRC-pathway, a major route for post-translational membrane insertion, is not required for LRRC59. Like emerin, another tail-anchored protein, LRRC59 reaches the INM, as demonstrated by rapamycin-dependent dimerization assays. Using different approaches to inhibit importin α/β-dependent nuclear import of soluble proteins, we show that the classic nuclear transport machinery does not play a major role in INM-targeting of LRRC59. Instead, the size of the cytoplasmic domain of LRRC59 is an important feature, suggesting that targeting is governed by passive diffusion.
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68
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Lang S, Nguyen D, Pfeffer S, Förster F, Helms V, Zimmermann R. Functions and Mechanisms of the Human Ribosome-Translocon Complex. Subcell Biochem 2019; 93:83-141. [PMID: 31939150 DOI: 10.1007/978-3-030-28151-9_4] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The membrane of the endoplasmic reticulum (ER) in human cells harbors the protein translocon, which facilitates membrane insertion and translocation of almost every newly synthesized polypeptide targeted to organelles of the secretory pathway. The translocon comprises the polypeptide-conducting Sec61 channel and several additional proteins, which are associated with the heterotrimeric Sec61 complex. This ensemble of proteins facilitates ER targeting of precursor polypeptides, Sec61 channel opening and closing, and modification of precursor polypeptides in transit through the Sec61 complex. Recently, cryoelectron tomography of translocons in native ER membranes has given unprecedented insights into the architecture and dynamics of the native, ribosome-associated translocon and the Sec61 channel. These structural data are discussed in light of different Sec61 channel activities including ribosome receptor function, membrane insertion or translocation of newly synthesized polypeptides as well as the possible roles of the Sec61 channel as a passive ER calcium leak channel and regulator of ATP/ADP exchange between cytosol and ER.
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Affiliation(s)
- Sven Lang
- Competence Center for Molecular Medicine, Saarland University Medical School, Building 44, 66421, Homburg, Germany.
| | - Duy Nguyen
- Center for Bioinformatics, Saarland University, 66041, Saarbrücken, Germany
| | - Stefan Pfeffer
- Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152, Martinsried, Germany
- ZMBH, 69120, Heidelberg, Germany
| | - Friedrich Förster
- Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152, Martinsried, Germany
- Center for Biomolecular Research, Utrecht University, 3584 CH, Utrecht, The Netherlands
| | - Volkhard Helms
- Center for Bioinformatics, Saarland University, 66041, Saarbrücken, Germany
| | - Richard Zimmermann
- Competence Center for Molecular Medicine, Saarland University Medical School, Building 44, 66421, Homburg, Germany
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69
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Farré JC, Mahalingam SS, Proietto M, Subramani S. Peroxisome biogenesis, membrane contact sites, and quality control. EMBO Rep 2018; 20:embr.201846864. [PMID: 30530632 DOI: 10.15252/embr.201846864] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2018] [Revised: 10/08/2018] [Accepted: 11/16/2018] [Indexed: 12/19/2022] Open
Abstract
Peroxisomes are conserved organelles of eukaryotic cells with important roles in cellular metabolism, human health, redox homeostasis, as well as intracellular metabolite transfer and signaling. We review here the current status of the different co-existing modes of biogenesis of peroxisomal membrane proteins demonstrating the fascinating adaptability in their targeting and sorting pathways. While earlier studies focused on peroxisomes as autonomous organelles, the necessity of the ER and potentially even mitochondria as sources of peroxisomal membrane proteins and lipids has come to light in recent years. Additionally, the intimate physical juxtaposition of peroxisomes with other organelles has transitioned from being viewed as random encounters to a growing appreciation of the expanding roles of such inter-organellar membrane contact sites in metabolic and regulatory functions. Peroxisomal quality control mechanisms have also come of age with a variety of mechanisms operating both during biogenesis and in the cellular response to environmental cues.
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Affiliation(s)
- Jean-Claude Farré
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, CA, USA
| | - Shanmuga S Mahalingam
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, CA, USA
| | - Marco Proietto
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, CA, USA
| | - Suresh Subramani
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, CA, USA
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70
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Onishi M, Nagumo S, Iwashita S, Okamoto K. The ER membrane insertase Get1/2 is required for efficient mitophagy in yeast. Biochem Biophys Res Commun 2018; 503:14-20. [PMID: 29673596 DOI: 10.1016/j.bbrc.2018.04.114] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 04/14/2018] [Indexed: 10/16/2022]
Abstract
Mitophagy is an evolutionarily conserved autophagy pathway that selectively eliminates mitochondria to control mitochondrial quality and quantity. Although mitophagy is thought to be crucial for cellular homeostasis, how this catabolic process is regulated remains largely unknown. Here we demonstrate that mitophagy during prolonged respiratory growth is strongly impaired in yeast cells lacking Get1/2, a transmembrane complex mediating insertion of tail-anchored (TA) proteins into the endoplasmic reticulum (ER) membrane. Under the same conditions, loss of Get1/2 caused only slight defects in other types of selective and bulk autophagy. In addition, mitophagy and other autophagy-related processes are mostly normal in cells lacking Get3, a cytosolic ATP-driven chaperone that promotes delivery of TA proteins to the Get1/2 complex. We also found that Get1/2-deficient cells exhibited wildtype-like induction and mitochondrial localization of Atg32, a protein essential for mitophagy. Notably, Get1/2 is important for Atg32-independent, ectopically promoted mitophagy. Together, we propose that Get1/2-dependent TA protein(s) and/or the Get1/2 complex itself may act specifically in mitophagy.
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Affiliation(s)
- Mashun Onishi
- Laboratory of Mitochondrial Dynamics, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
| | - Sachiyo Nagumo
- Laboratory of Mitochondrial Dynamics, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
| | - Shohei Iwashita
- Laboratory of Mitochondrial Dynamics, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
| | - Koji Okamoto
- Laboratory of Mitochondrial Dynamics, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan.
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71
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Mateja A, Keenan RJ. A structural perspective on tail-anchored protein biogenesis by the GET pathway. Curr Opin Struct Biol 2018; 51:195-202. [PMID: 30173121 DOI: 10.1016/j.sbi.2018.07.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 07/19/2018] [Accepted: 07/20/2018] [Indexed: 12/16/2022]
Abstract
Many tail-anchored (TA) membrane proteins are targeted to and inserted into the endoplasmic reticulum (ER) by the `guided entry of tail-anchored proteins' (GET) pathway. This post-translational pathway uses transmembrane-domain selective cytosolic chaperones for targeting, and a dedicated membrane protein complex for insertion. The past decade has seen rapid progress towards defining the molecular basis of TA protein biogenesis by the GET pathway. Here we review the mechanisms underlying each step of the pathway, emphasizing recent structural work and highlighting key questions that await future studies.
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Affiliation(s)
- Agnieszka Mateja
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Robert J Keenan
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA.
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72
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Shaaban S, MacKinnon S, Andrews C, Staffieri SE, Maconachie GDE, Chan WM, Whitman MC, Morton SU, Yazar S, MacGregor S, Elder JE, Traboulsi EI, Gottlob I, Hewitt AW, Hunter DG, Mackey DA, Engle EC. Genome-Wide Association Study Identifies a Susceptibility Locus for Comitant Esotropia and Suggests a Parent-of-Origin Effect. Invest Ophthalmol Vis Sci 2018; 59:4054-4064. [PMID: 30098192 PMCID: PMC6088800 DOI: 10.1167/iovs.18-24082] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Accepted: 06/19/2018] [Indexed: 11/24/2022] Open
Abstract
Purpose To identify genetic variants conferring susceptibility to esotropia. Esotropia is the most common form of comitant strabismus, has its highest incidence in European ancestry populations, and is believed to be inherited as a complex trait. Methods White European American discovery cohorts with nonaccommodative (826 cases and 2991 controls) or accommodative (224 cases and 749 controls) esotropia were investigated. White European Australian and United Kingdom cohorts with nonaccommodative (689 cases and 1448 controls) or accommodative (66 cases and 264 controls) esotropia were tested for replication. We performed a genome-wide case-control association study using a mixed linear additive model. Meta-analyses of discovery and replication cohorts were then conducted. Results A significant association with nonaccommodative esotropia was discovered (odds ratio [OR] = 1.41, P = 2.84 × 10-09) and replicated (OR = 1.23, P = 0.01) at rs2244352 [T] located within intron 1 of the WRB (tryptophan rich basic protein) gene on chromosome 21 (meta-analysis OR = 1.33, P = 9.58 × 10-11). This single nucleotide polymorphism (SNP) is differentially methylated, and there is a statistically significant skew toward paternal inheritance in the discovery cohort. Meta-analysis of the accommodative discovery and replication cohorts identified an association with rs912759 [T] (OR = 0.59, P = 1.89 × 10-08), an intergenic SNP on chromosome 1p31.1. Conclusions This is the first genome-wide association study (GWAS) to identify significant associations in esotropia and suggests a parent-of-origin effect. Additional cohorts will permit replication and extension of these findings. Future studies of rs2244352 and WRB should provide insight into pathophysiological mechanisms underlying comitant strabismus.
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Affiliation(s)
- Sherin Shaaban
- Department of Neurology, Boston Children's Hospital, Boston, Massachusetts, United States
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, Massachusetts, United States
- Department of Neurology, Harvard Medical School, Boston, Massachusetts, United States
- Dubai Harvard Foundation for Medical Research, Boston, Massachusetts, United States
| | - Sarah MacKinnon
- Department of Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, United States
| | - Caroline Andrews
- Department of Neurology, Boston Children's Hospital, Boston, Massachusetts, United States
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States
| | - Sandra E. Staffieri
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, Victoria, Australia
- Department of Ophthalmology, Royal Children's Hospital, University of Melbourne, Parkville, Victoria, Australia
| | - Gail D. E. Maconachie
- Department of Neuroscience, The University of Leicester Ulverscroft Eye Unit, University of Leicester, Leicester, United Kingdom
| | - Wai-Man Chan
- Department of Neurology, Boston Children's Hospital, Boston, Massachusetts, United States
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States
| | - Mary C. Whitman
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, Massachusetts, United States
- Department of Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, United States
- Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States
| | - Sarah U. Morton
- Division of Newborn Medicine, Boston Children's Hospital, Boston, Massachusetts, United States
| | - Seyhan Yazar
- Medical Research Council (MRC) Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine, The University of Edinburgh, Western General Hospital, Edinburgh, United Kingdom
- Centre for Ophthalmology and Visual Science, University of Western Australia, Lions Eye Institute, Perth, Western Australia, Australia
| | - Stuart MacGregor
- Stastical Genetics Laboratory, Queensland Institute of Medical Research (QIMR) Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - James E. Elder
- Department of Ophthalmology, Royal Children's Hospital, University of Melbourne, Parkville, Victoria, Australia
- Department of Pediatrics, The University of Melbourne, Parkville, Victoria, Australia
| | - Elias I. Traboulsi
- Department of Ophthalmology, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
| | - Irene Gottlob
- Department of Neuroscience, The University of Leicester Ulverscroft Eye Unit, University of Leicester, Leicester, United Kingdom
| | - Alex W. Hewitt
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, Victoria, Australia
- Centre for Ophthalmology and Visual Science, University of Western Australia, Lions Eye Institute, Perth, Western Australia, Australia
- Department of Ophthalmology, School of Medicine, Menzies Institute for Medical Research, University of Tasmania, Tasmania, Australia
| | - Strabismus Genetics Research Consortium
- Department of Neurology, Boston Children's Hospital, Boston, Massachusetts, United States
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, Massachusetts, United States
- Department of Neurology, Harvard Medical School, Boston, Massachusetts, United States
- Dubai Harvard Foundation for Medical Research, Boston, Massachusetts, United States
- Department of Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, United States
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, Victoria, Australia
- Department of Ophthalmology, Royal Children's Hospital, University of Melbourne, Parkville, Victoria, Australia
- Department of Neuroscience, The University of Leicester Ulverscroft Eye Unit, University of Leicester, Leicester, United Kingdom
- Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States
- Division of Newborn Medicine, Boston Children's Hospital, Boston, Massachusetts, United States
- Medical Research Council (MRC) Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine, The University of Edinburgh, Western General Hospital, Edinburgh, United Kingdom
- Centre for Ophthalmology and Visual Science, University of Western Australia, Lions Eye Institute, Perth, Western Australia, Australia
- Stastical Genetics Laboratory, Queensland Institute of Medical Research (QIMR) Berghofer Medical Research Institute, Brisbane, Queensland, Australia
- Department of Pediatrics, The University of Melbourne, Parkville, Victoria, Australia
- Department of Ophthalmology, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
- Department of Ophthalmology, School of Medicine, Menzies Institute for Medical Research, University of Tasmania, Tasmania, Australia
- Broad Institute of Massachusetts Institute of Technology (MIT) and Harvard, Cambridge, Massachusetts, United States
| | - David G. Hunter
- Department of Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, United States
- Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States
| | - David A. Mackey
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, Victoria, Australia
- Centre for Ophthalmology and Visual Science, University of Western Australia, Lions Eye Institute, Perth, Western Australia, Australia
- Department of Ophthalmology, School of Medicine, Menzies Institute for Medical Research, University of Tasmania, Tasmania, Australia
| | - Elizabeth C. Engle
- Department of Neurology, Boston Children's Hospital, Boston, Massachusetts, United States
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, Massachusetts, United States
- Department of Neurology, Harvard Medical School, Boston, Massachusetts, United States
- Department of Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, United States
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States
- Broad Institute of Massachusetts Institute of Technology (MIT) and Harvard, Cambridge, Massachusetts, United States
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Aviram N, Schuldiner M. Targeting and translocation of proteins to the endoplasmic reticulum at a glance. J Cell Sci 2018; 130:4079-4085. [PMID: 29246967 DOI: 10.1242/jcs.204396] [Citation(s) in RCA: 86] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The evolutionary emergence of organelles was a defining process in diversifying biochemical reactions within the cell and enabling multicellularity. However, compartmentalization also imposed a great challenge-the need to import proteins synthesized in the cytosol into their respective sites of function. For example, one-third of all genes encode for proteins that must be targeted and translocated into the endoplasmic reticulum (ER), which serves as the entry site to the majority of endomembrane compartments. Decades of research have set down the fundamental principles of how proteins get from the cytosol into the ER, and recent studies have brought forward new pathways and additional regulators enabling better definition of the rules governing substrate recognition. In this Cell Science at a Glance article and the accompanying poster, we give an overview of our current understanding of the multifaceted and regulated processes of protein targeting and translocation to the ER.
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Affiliation(s)
- Naama Aviram
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel 7610001
| | - Maya Schuldiner
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel 7610001
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74
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Cho H, Shan SO. Substrate relay in an Hsp70-cochaperone cascade safeguards tail-anchored membrane protein targeting. EMBO J 2018; 37:embj.201899264. [PMID: 29973361 DOI: 10.15252/embj.201899264] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Revised: 05/24/2018] [Accepted: 05/29/2018] [Indexed: 12/14/2022] Open
Abstract
Membrane proteins are aggregation-prone in aqueous environments, and their biogenesis poses acute challenges to cellular protein homeostasis. How the chaperone network effectively protects integral membrane proteins during their post-translational targeting is not well understood. Here, biochemical reconstitutions showed that the yeast cytosolic Hsp70 is responsible for capturing newly synthesized tail-anchored membrane proteins (TAs) in the soluble form. Moreover, direct interaction of Hsp70 with the cochaperone Sgt2 initiates a sequential series of TA relays to the dedicated TA targeting factor Get3. In contrast to direct loading of TAs to downstream chaperones, stepwise substrate loading via Hsp70 maintains the solubility and targeting competence of TAs, ensuring their efficient delivery to the endoplasmic reticulum (ER). Inactivation of cytosolic Hsp70 severely impairs TA translocation in vivo Our results demonstrate a new role of cytosolic Hsp70 in directly assisting the targeting of an essential class of integral membrane proteins and provide a paradigm for how "substrate funneling" through a chaperone cascade preserves the conformational quality of nascent membrane proteins during their biogenesis.
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Affiliation(s)
- Hyunju Cho
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Shu-Ou Shan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
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Manu M, Ghosh D, Chaudhari BP, Ramasamy S. Analysis of tail-anchored protein translocation pathway in plants. Biochem Biophys Rep 2018; 14:161-167. [PMID: 29872748 PMCID: PMC5986991 DOI: 10.1016/j.bbrep.2018.05.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Tail-anchored (TA) proteins are a special class of membrane proteins that carry out vital functions in all living cells. Targeting mechanisms of TA proteins are investigated as the best example for post-translational protein targeting in yeast. Of the several mechanisms, Guided Entry of Tail-anchored protein (GET) pathway plays a major role in TA protein targeting. Many in silico and in vivo analyses are geared to identify TA proteins and their targeting mechanisms in different systems including Arabidopsis thaliana. Yet, crop plants that grow in specific and/or different conditions are not investigated for the presence of TA proteins and GET pathway. This study majorly investigates GET pathway in two crop plants, Oryza sativa subsp. Indica and Solanum tuberosum, through detailed in silico analysis. 508 and 912 TA proteins are identified in Oryza sativa subsp. Indica and Solanum tuberosum respectively and their localization with respect to endoplasmic reticulum (ER), mitochondria, and chloroplast has been delineated. Similarly, the associated GET proteins are identified (Get1, Get3 and Get4) and their structural inferences are elucidated using homology modelling. Get3 models are based on yeast Get3. The cytoplasmic Get3 from O. sativa is identified to be very similar to yeast Get3 with conserved P-loop and TA binding groove. Three cytoplasmic Get3s are identified for S. tuberosum. Taken together, this is the first study to identify TA proteins and GET components in Oryza sativa subsp. Indica and Solanum tuberosum, forming the basis for any further experimental characterization of TA targeting and GET pathway mechanisms in crop plants.
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Affiliation(s)
- M.S. Manu
- Biochemical Sciences Division, CSIR-National Chemical Laboratory, Pune 411008 India
- Academy of Scientific and Innovative Research (AcSIR), CSIR-National Chemical Laboratory, Pune 411008, India
| | - Deepanjan Ghosh
- Biochemical Sciences Division, CSIR-National Chemical Laboratory, Pune 411008 India
- Academy of Scientific and Innovative Research (AcSIR), CSIR-National Chemical Laboratory, Pune 411008, India
| | - Bhushan P. Chaudhari
- Biochemical Sciences Division, CSIR-National Chemical Laboratory, Pune 411008 India
- Academy of Scientific and Innovative Research (AcSIR), CSIR-National Chemical Laboratory, Pune 411008, India
| | - Sureshkumar Ramasamy
- Biochemical Sciences Division, CSIR-National Chemical Laboratory, Pune 411008 India
- Academy of Scientific and Innovative Research (AcSIR), CSIR-National Chemical Laboratory, Pune 411008, India
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76
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Abstract
Proper localization of membrane proteins is essential for the function of biological membranes and for the establishment of organelle identity within a cell. Molecular machineries that mediate membrane protein biogenesis need to not only achieve a high degree of efficiency and accuracy, but also prevent off-pathway aggregation events that can be detrimental to cells. The posttranslational targeting of tail-anchored proteins (TAs) provides tractable model systems to probe these fundamental issues. Recent advances in understanding TA-targeting pathways reveal sophisticated molecular machineries that drive and regulate these processes. These findings also suggest how an interconnected network of targeting factors, cochaperones, and quality control machineries together ensures robust membrane protein biogenesis.
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Affiliation(s)
- Un Seng Chio
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125; , ,
| | - Hyunju Cho
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125; , ,
| | - Shu-Ou Shan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125; , ,
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77
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Zalisko BE, Chan C, Denic V, Rock RS, Keenan RJ. Tail-Anchored Protein Insertion by a Single Get1/2 Heterodimer. Cell Rep 2018; 20:2287-2293. [PMID: 28877464 DOI: 10.1016/j.celrep.2017.08.035] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 06/27/2017] [Accepted: 08/07/2017] [Indexed: 01/19/2023] Open
Abstract
The Get1/2 transmembrane complex drives the insertion of tail-anchored (TA) proteins from the cytosolic chaperone Get3 into the endoplasmic reticulum membrane. Mechanistic insight into how Get1/2 coordinates this process is confounded by a lack of understanding of the basic architecture of the complex. Here, we define the oligomeric state of full-length Get1/2 in reconstituted lipid bilayers by combining single-molecule and bulk fluorescence measurements with quantitative in vitro insertion analysis. We show that a single Get1/2 heterodimer is sufficient for insertion and demonstrate that the conserved cytosolic regions of Get1 and Get2 bind asymmetrically to opposing subunits of the Get3 homodimer. Altogether, our results define a simplified model for how Get1/2 and Get3 coordinate TA protein insertion.
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Affiliation(s)
- Benjamin E Zalisko
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Charlene Chan
- Department of Molecular and Cellular Biology, Northwest Labs, Harvard University, Cambridge, MA 02138, USA
| | - Vladimir Denic
- Department of Molecular and Cellular Biology, Northwest Labs, Harvard University, Cambridge, MA 02138, USA.
| | - Ronald S Rock
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA.
| | - Robert J Keenan
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA.
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78
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Guna A, Volkmar N, Christianson JC, Hegde RS. The ER membrane protein complex is a transmembrane domain insertase. Science 2018; 359:470-473. [PMID: 29242231 PMCID: PMC5788257 DOI: 10.1126/science.aao3099] [Citation(s) in RCA: 179] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Revised: 10/26/2017] [Accepted: 11/27/2017] [Indexed: 12/26/2022]
Abstract
Insertion of proteins into membranes is an essential cellular process. The extensive biophysical and topological diversity of membrane proteins necessitates multiple insertion pathways that remain incompletely defined. Here we found that known membrane insertion pathways fail to effectively engage tail-anchored membrane proteins with moderately hydrophobic transmembrane domains. These proteins are instead shielded in the cytosol by calmodulin. Dynamic release from calmodulin allowed sampling of the endoplasmic reticulum (ER), where the conserved ER membrane protein complex (EMC) was shown to be essential for efficient insertion in vitro and in cells. Purified EMC in synthetic liposomes catalyzed the insertion of its substrates in a reconstituted system. Thus, EMC is a transmembrane domain insertase, a function that may explain its widely pleiotropic membrane-associated phenotypes across organisms.
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Affiliation(s)
- Alina Guna
- Medical Research Council (MRC) Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK
| | - Norbert Volkmar
- Ludwig Institute for Cancer Research, University of Oxford, Old Road Campus Research Building, Headington, Oxford OX3 7DQ, UK
| | - John C Christianson
- Ludwig Institute for Cancer Research, University of Oxford, Old Road Campus Research Building, Headington, Oxford OX3 7DQ, UK
| | - Ramanujan S Hegde
- Medical Research Council (MRC) Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK.
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79
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Anghel SA, McGilvray PT, Hegde RS, Keenan RJ. Identification of Oxa1 Homologs Operating in the Eukaryotic Endoplasmic Reticulum. Cell Rep 2017; 21:3708-3716. [PMID: 29281821 PMCID: PMC5868721 DOI: 10.1016/j.celrep.2017.12.006] [Citation(s) in RCA: 95] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 10/18/2017] [Accepted: 12/01/2017] [Indexed: 12/23/2022] Open
Abstract
Members of the evolutionarily conserved Oxa1/Alb3/YidC family mediate membrane protein biogenesis at the mitochondrial inner membrane, chloroplast thylakoid membrane, and bacterial plasma membrane, respectively. Despite their broad phylogenetic distribution, no Oxa1/Alb3/YidC homologs are known to operate in eukaryotic cells outside the endosymbiotic organelles. Here, we present bioinformatic evidence that the tail-anchored protein insertion factor WRB/Get1, the "endoplasmic reticulum (ER) membrane complex" subunit EMC3, and TMCO1 are ER-resident homologs of the Oxa1/Alb3/YidC family. Topology mapping and co-evolution-based modeling demonstrate that Get1, EMC3, and TMCO1 share a conserved Oxa1-like architecture. Biochemical analysis of human TMCO1, the only homolog not previously linked to membrane protein biogenesis, shows that it associates with the Sec translocon and ribosomes. These findings suggest a specific biochemical function for TMCO1 and define a superfamily of proteins-the "Oxa1 superfamily"-whose shared function is to facilitate membrane protein biogenesis.
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Affiliation(s)
- S Andrei Anghel
- Department of Biochemistry and Molecular Biology , The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA; Cell and Molecular Biology Graduate Program , The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Philip T McGilvray
- Department of Biochemistry and Molecular Biology , The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Ramanujan S Hegde
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Robert J Keenan
- Department of Biochemistry and Molecular Biology , The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA.
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80
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Casson J, McKenna M, Haßdenteufel S, Aviram N, Zimmerman R, High S. Multiple pathways facilitate the biogenesis of mammalian tail-anchored proteins. J Cell Sci 2017; 130:3851-3861. [PMID: 29021347 PMCID: PMC5702047 DOI: 10.1242/jcs.207829] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Accepted: 09/17/2017] [Indexed: 12/24/2022] Open
Abstract
Tail-anchored (TA) proteins are transmembrane proteins with a single C-terminal transmembrane domain, which functions as both their subcellular targeting signal and membrane anchor. We show that knockout of TRC40 in cultured human cells has a relatively minor effect on endogenous TA proteins, despite their apparent reliance on this pathway in vitro. These findings support recent evidence that the canonical TRC40 pathway is not essential for TA protein biogenesis in vivo. We therefore investigated the possibility that other ER-targeting routes can complement the TRC40 pathway and identified roles for both the SRP pathway and the recently described mammalian SND pathway in TA protein biogenesis. We conclude that, although TRC40 normally plays an important role in TA protein biogenesis, it is not essential, and speculate that alternative pathways for TA protein biogenesis, including those identified in this study, contribute to the redundancy of the TRC40 pathway. Summary: In addition to the canonical TRC40-targeting pathway, mammalian tail-anchored proteins can also utilise the SRP and SND pathways to facilitate their insertion into the ER membrane.
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Affiliation(s)
- Joseph Casson
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Michael Smith Building, Manchester, M13 9PT, UK
| | - Michael McKenna
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Michael Smith Building, Manchester, M13 9PT, UK
| | - Sarah Haßdenteufel
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany
| | - Naama Aviram
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Richard Zimmerman
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany
| | - Stephen High
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Michael Smith Building, Manchester, M13 9PT, UK
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81
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Haßdenteufel S, Sicking M, Schorr S, Aviram N, Fecher-Trost C, Schuldiner M, Jung M, Zimmermann R, Lang S. hSnd2 protein represents an alternative targeting factor to the endoplasmic reticulum in human cells. FEBS Lett 2017; 591:3211-3224. [PMID: 28862756 DOI: 10.1002/1873-3468.12831] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 08/22/2017] [Accepted: 08/24/2017] [Indexed: 12/11/2022]
Abstract
Recently, understanding of protein targeting to the endoplasmic reticulum (ER) was expanded by the discovery of multiple pathways that function in parallel to the signal recognition particle (SRP). Guided entry of tail-anchored proteins and SRP independent (SND) are two such targeting pathways described in yeast. So far, no human SND component is functionally characterized. Here, we report hSnd2 as the first constituent of the human SND pathway able to support substrate-specific protein targeting to the ER. Similar to its yeast counterpart, hSnd2 is assumed to function as a membrane-bound receptor preferentially targeting precursors carrying C-terminal transmembrane domains. Our genetic and physical interaction studies show that hSnd2 is part of a complex network of targeting and translocation that is dynamically regulated.
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Affiliation(s)
- Sarah Haßdenteufel
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Mark Sicking
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Stefan Schorr
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Naama Aviram
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Claudia Fecher-Trost
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Saarland University, Homburg, Germany
| | - Maya Schuldiner
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Martin Jung
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Richard Zimmermann
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Sven Lang
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
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82
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Daniele LL, Emran F, Lobo GP, Gaivin RJ, Perkins BD. Mutation of wrb, a Component of the Guided Entry of Tail-Anchored Protein Pathway, Disrupts Photoreceptor Synapse Structure and Function. Invest Ophthalmol Vis Sci 2017; 57:2942-54. [PMID: 27273592 PMCID: PMC4898200 DOI: 10.1167/iovs.15-18996] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
PURPOSE Tail-anchored (TA) proteins contain a single hydrophobic domain at the C-terminus and are posttranslationally inserted into the ER membrane via the GET (guided entry of tail-anchored proteins) pathway. The role of the GET pathway in photoreceptors is unexplored. The goal of this study was to characterize the zebrafish pinball wizard mutant, which disrupts Wrb, a core component of the GET pathway. METHODS Electroretinography, optokinetic response measurements (OKR), immunohistochemistry, and electron microscopy analyses were employed to assess ribbon synapse function, protein expression, and ultrastructure in 5-day-old zebrafish larvae. Expression of wrb was investigated with real-time qRT-PCR and in situ hybridization. RESULTS Mutation of wrb abolished the OKR and greatly diminished the ERG b-wave, but not the a-wave. Ribeye and SV2 were partially mislocalized in both photoreceptors and hair cells of wrb mutants. Fewer contacts were seen between photoreceptors and bipolar cells in wrb-/- mutants. Expression of wrb was observed throughout the nervous system and Wrb localized to the ER and synaptic region of photoreceptors. Morpholino knockdown of the cytosolic ATPase trc40, which targets TA proteins to the ER, also diminished the OKR. Overexpression of wrb fully restored contrast sensitivity in mutants, while overexpression of mutant wrbR73A, which cannot bind Trc40, did not. CONCLUSIONS Proteins Wrb and Trc40 are required for synaptic transmission between photoreceptors and bipolar cells, indicating that TA protein insertion by the TRC pathway is a critical step in ribbon synapse assembly and function.
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Affiliation(s)
- Lauren L Daniele
- Department of Ophthalmic Research Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
| | - Farida Emran
- Centre for Research in Neuroscience, McGill University, Montreal, Quebec, Canada
| | - Glenn P Lobo
- Department of Ophthalmic Research Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
| | - Robert J Gaivin
- Department of Ophthalmic Research Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
| | - Brian D Perkins
- Department of Ophthalmic Research Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
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83
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Xing S, Mehlhorn DG, Wallmeroth N, Asseck LY, Kar R, Voss A, Denninger P, Schmidt VAF, Schwarzländer M, Stierhof YD, Grossmann G, Grefen C. Loss of GET pathway orthologs in Arabidopsis thaliana causes root hair growth defects and affects SNARE abundance. Proc Natl Acad Sci U S A 2017; 114:E1544-E1553. [PMID: 28096354 PMCID: PMC5338382 DOI: 10.1073/pnas.1619525114] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins are key players in cellular trafficking and coordinate vital cellular processes, such as cytokinesis, pathogen defense, and ion transport regulation. With few exceptions, SNAREs are tail-anchored (TA) proteins, bearing a C-terminal hydrophobic domain that is essential for their membrane integration. Recently, the Guided Entry of Tail-anchored proteins (GET) pathway was described in mammalian and yeast cells that serve as a blueprint of TA protein insertion [Schuldiner M, et al. (2008) Cell 134(4):634-645; Stefanovic S, Hegde RS (2007) Cell 128(6):1147-1159]. This pathway consists of six proteins, with the cytosolic ATPase GET3 chaperoning the newly synthesized TA protein posttranslationally from the ribosome to the endoplasmic reticulum (ER) membrane. Structural and biochemical insights confirmed the potential of pathway components to facilitate membrane insertion, but the physiological significance in multicellular organisms remains to be resolved. Our phylogenetic analysis of 37 GET3 orthologs from 18 different species revealed the presence of two different GET3 clades. We identified and analyzed GET pathway components in Arabidopsis thaliana and found reduced root hair elongation in Atget lines, possibly as a result of reduced SNARE biogenesis. Overexpression of AtGET3a in a receptor knockout (KO) results in severe growth defects, suggesting presence of alternative insertion pathways while highlighting an intricate involvement for the GET pathway in cellular homeostasis of plants.
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Affiliation(s)
- Shuping Xing
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany
| | - Dietmar Gerald Mehlhorn
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany
| | - Niklas Wallmeroth
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany
| | - Lisa Yasmin Asseck
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany
| | - Ritwika Kar
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany
| | - Alessa Voss
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany
| | - Philipp Denninger
- Centre for Organismal Studies, CellNetworks Excellence Cluster, University of Heidelberg, 69120 Heidelberg, Germany
| | - Vanessa Aphaia Fiona Schmidt
- Centre for Organismal Studies, CellNetworks Excellence Cluster, University of Heidelberg, 69120 Heidelberg, Germany
| | - Markus Schwarzländer
- Institute of Crop Science and Resource Conservation, University of Bonn, 53113 Bonn, Germany
| | - York-Dieter Stierhof
- Centre for Plant Molecular Biology, Microscopy, University of Tübingen, 72076 Tuebingen, Germany
| | - Guido Grossmann
- Centre for Organismal Studies, CellNetworks Excellence Cluster, University of Heidelberg, 69120 Heidelberg, Germany
| | - Christopher Grefen
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany;
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84
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Rivera-Monroy J, Musiol L, Unthan-Fechner K, Farkas Á, Clancy A, Coy-Vergara J, Weill U, Gockel S, Lin SY, Corey DP, Kohl T, Ströbel P, Schuldiner M, Schwappach B, Vilardi F. Mice lacking WRB reveal differential biogenesis requirements of tail-anchored proteins in vivo. Sci Rep 2016; 6:39464. [PMID: 28000760 PMCID: PMC5175141 DOI: 10.1038/srep39464] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 11/22/2016] [Indexed: 02/06/2023] Open
Abstract
Tail-anchored (TA) proteins are post-translationally inserted into membranes. The TRC40 pathway targets TA proteins to the endoplasmic reticulum via a receptor comprised of WRB and CAML. TRC40 pathway clients have been identified using in vitro assays, however, the relevance of the TRC40 pathway in vivo remains unknown. We followed the fate of TA proteins in two tissue-specific WRB knockout mouse models and found that their dependence on the TRC40 pathway in vitro did not predict their reaction to receptor depletion in vivo. The SNARE syntaxin 5 (Stx5) was extremely sensitive to disruption of the TRC40 pathway. Screening yeast TA proteins with mammalian homologues, we show that the particular sensitivity of Stx5 is conserved, possibly due to aggregation propensity of its cytoplasmic domain. We establish that Stx5 is an autophagy target that is inefficiently membrane-targeted by alternative pathways. Our results highlight an intimate relationship between the TRC40 pathway and cellular proteostasis.
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Affiliation(s)
- Jhon Rivera-Monroy
- Department of Molecular Biology, Universitätsmedizin Göttingen, D-37073 Göttingen, Germany
| | - Lena Musiol
- Department of Molecular Biology, Universitätsmedizin Göttingen, D-37073 Göttingen, Germany
| | - Kirsten Unthan-Fechner
- Department of Molecular Biology, Universitätsmedizin Göttingen, D-37073 Göttingen, Germany
| | - Ákos Farkas
- Department of Molecular Biology, Universitätsmedizin Göttingen, D-37073 Göttingen, Germany
| | - Anne Clancy
- Department of Molecular Biology, Universitätsmedizin Göttingen, D-37073 Göttingen, Germany
| | - Javier Coy-Vergara
- Department of Molecular Biology, Universitätsmedizin Göttingen, D-37073 Göttingen, Germany
| | - Uri Weill
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Sarah Gockel
- Department of Cardiology &Pulmonology, Universitätsmedizin Göttingen, D-37075 Göttingen, Germany
| | - Shuh-Yow Lin
- Howard Hughes Medical Institute and Department of Neurobiology, Harvard Medical School, Boston, MA, USA
| | - David P Corey
- Howard Hughes Medical Institute and Department of Neurobiology, Harvard Medical School, Boston, MA, USA
| | - Tobias Kohl
- Department of Cardiology &Pulmonology, Universitätsmedizin Göttingen, D-37075 Göttingen, Germany
| | - Philipp Ströbel
- Institute of Pathology, Universitätsmedizin Göttingen, D-37073 Göttingen, Germany
| | - Maya Schuldiner
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Blanche Schwappach
- Department of Molecular Biology, Universitätsmedizin Göttingen, D-37073 Göttingen, Germany.,Max-Planck Institute for Biophysical Chemistry, D-37077, Göttingen, Germany
| | - Fabio Vilardi
- Department of Molecular Biology, Universitätsmedizin Göttingen, D-37073 Göttingen, Germany
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85
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Rao M, Okreglak V, Chio US, Cho H, Walter P, Shan SO. Multiple selection filters ensure accurate tail-anchored membrane protein targeting. eLife 2016; 5. [PMID: 27925580 PMCID: PMC5214336 DOI: 10.7554/elife.21301] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Accepted: 12/06/2016] [Indexed: 11/13/2022] Open
Abstract
Accurate protein localization is crucial to generate and maintain organization in all cells. Achieving accuracy is challenging, as the molecular signals that dictate a protein's cellular destination are often promiscuous. A salient example is the targeting of an essential class of tail-anchored (TA) proteins, whose sole defining feature is a transmembrane domain near their C-terminus. Here we show that the Guided Entry of Tail-anchored protein (GET) pathway selects TA proteins destined to the endoplasmic reticulum (ER) utilizing distinct molecular steps, including differential binding by the co-chaperone Sgt2 and kinetic proofreading after ATP hydrolysis by the targeting factor Get3. Further, the different steps select for distinct physicochemical features of the TA substrate. The use of multiple selection filters may be general to protein biogenesis pathways that must distinguish correct and incorrect substrates based on minor differences.
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Affiliation(s)
- Meera Rao
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States
| | - Voytek Okreglak
- Howard Hughes Medical Institute, University of California, San Francisco, United States.,Department of Biochemistry and Biophysics, University of California, San Francisco, United States
| | - Un Seng Chio
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States
| | - Hyunju Cho
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States
| | - Peter Walter
- Howard Hughes Medical Institute, University of California, San Francisco, United States.,Department of Biochemistry and Biophysics, University of California, San Francisco, United States
| | - Shu-Ou Shan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States
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86
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ATPase and GTPase Tangos Drive Intracellular Protein Transport. Trends Biochem Sci 2016; 41:1050-1060. [PMID: 27658684 DOI: 10.1016/j.tibs.2016.08.012] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Revised: 08/18/2016] [Accepted: 08/23/2016] [Indexed: 11/24/2022]
Abstract
The GTPase superfamily of proteins provides molecular switches to regulate numerous cellular processes. The 'GTPase switch' paradigm, in which external regulatory factors control the switch of a GTPase between 'on' and 'off' states, has been used to interpret the regulatory mechanism of many GTPases. However, recent work unveiled a class of nucleotide hydrolases that do not adhere to this classical paradigm. Instead, they use nucleotide-dependent dimerization cycles to regulate key cellular processes. In this review article, recent studies of dimeric GTPases and ATPases involved in intracellular protein targeting are summarized. It is suggested that these proteins can use the conformational plasticity at their dimer interface to generate multiple points of regulation, thereby providing the driving force and spatiotemporal coordination of complex cellular pathways.
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87
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Pross E, Soussoula L, Seitl I, Lupo D, Kuhn A. Membrane Targeting and Insertion of the C-Tail Protein SciP. J Mol Biol 2016; 428:4218-4227. [PMID: 27600410 DOI: 10.1016/j.jmb.2016.09.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 08/22/2016] [Accepted: 09/01/2016] [Indexed: 11/27/2022]
Abstract
C-tailed membrane proteins insert into the bilayer post-translationally because the hydrophobic anchor segment leaves the ribosome at the end of translation. Nevertheless, we find here evidence that the targeting of SciP to the membrane of Escherichia coli occurs co-translationally since signal elements in the N-terminal part of the SciP protein sequence are present. Two short hydrophobic sequences were identified that targeted a green fluorescent protein-SciP fusion protein to the membrane involving the signal recognition particle. After targeting, the membrane insertion of SciP is catalyzed by YidC independent of the SecYEG translocase. However, when the C-terminal tail of SciP was extended to 21 aa residues, we found that SecYEG becomes involved and makes its membrane insertion more efficient.
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Affiliation(s)
- Eva Pross
- Institute of Microbiology and Molecular Biology, University of Hohenheim, 70599 Stuttgart, Germany
| | - Lavinia Soussoula
- Institute of Microbiology and Molecular Biology, University of Hohenheim, 70599 Stuttgart, Germany
| | - Ines Seitl
- Institute of Microbiology and Molecular Biology, University of Hohenheim, 70599 Stuttgart, Germany
| | - Domenico Lupo
- Institute of Microbiology and Molecular Biology, University of Hohenheim, 70599 Stuttgart, Germany
| | - Andreas Kuhn
- Institute of Microbiology and Molecular Biology, University of Hohenheim, 70599 Stuttgart, Germany.
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88
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Cotranslational Intersection between the SRP and GET Targeting Pathways to the Endoplasmic Reticulum of Saccharomyces cerevisiae. Mol Cell Biol 2016; 36:2374-83. [PMID: 27354063 DOI: 10.1128/mcb.00131-16] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 06/17/2016] [Indexed: 01/21/2023] Open
Abstract
Targeting of transmembrane proteins to the endoplasmic reticulum (ER) proceeds via either the signal recognition particle (SRP) or the guided entry of tail-anchored proteins (GET) pathway, consisting of Get1 to -5 and Sgt2. While SRP cotranslationally targets membrane proteins containing one or multiple transmembrane domains, the GET pathway posttranslationally targets proteins containing a single C-terminal transmembrane domain termed the tail anchor. Here, we dissect the roles of the SRP and GET pathways in the sorting of homologous, two-membrane-spanning K(+) channel proteins termed Kcv, Kesv, and Kesv-VV. We show that Kcv is targeted to the ER cotranslationally via its N-terminal transmembrane domain, while Kesv-VV is targeted posttranslationally via its C-terminal transmembrane domain, which recruits Get4-5/Sgt2 and Get3. Unexpectedly, nascent Kcv recruited not only SRP but also the Get4-5 module of the GET pathway to ribosomes. Ribosome binding of Get4-5 was independent of Sgt2 and was strongly outcompeted by SRP. The combined data indicate a previously unrecognized cotranslational interplay between the SRP and GET pathways.
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89
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Abstract
In this issue of Structure, Borowska et al. (2015) report the crystal structure and provide experimental evidence on an archaeal membrane insertase, the DUF106 protein from Methanocaldococcus jannaschii, demonstrating that YidC/Oxa1/Alb3-like insertases exist in the archaeal plasma membrane.
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Affiliation(s)
- Ross E Dalbey
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA.
| | - Andreas Kuhn
- Institute of Microbiology and Molecular Biology, University of Hohenheim, 70599 Stuttgart, Germany.
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90
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On the road to nowhere: cross-talk between post-translational protein targeting and cytosolic quality control. Biochem Soc Trans 2016; 44:796-801. [DOI: 10.1042/bst20160045] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Indexed: 02/06/2023]
Abstract
A well-defined co-translational pathway couples the synthesis and translocation of nascent polypeptides into and across the membrane of the endoplasmic reticulum (ER), thereby minimizing the possibility of the hydrophobic signals and transmembrane domains that such proteins contain from being exposed to the cytosol. Nevertheless, a proportion of these co-translational substrates may fail to reach the ER, and therefore mislocalize to the cytosol where their intrinsic hydrophobicity makes them aggregation-prone. A range of hydrophobic precursor proteins that employ alternative, post-translational, routes for ER translocation also contribute to the cytosolic pool of mislocalized proteins (MLPs). In this review, we detail how mammalian cells can efficiently deal with these MLPs by selectively targeting them for proteasomal degradation. Strikingly, this pathway for MLP degradation is regulated by cytosolic components that also facilitate the TRC40-dependent, post-translational, delivery of tail-anchored membrane proteins (TA proteins) to the ER. Among these components are small glutamine-rich tetratricopeptide repeat-containing protein α (SGTA) and Bcl-2-associated athanogene 6 (BAG6), which appear to play a decisive role in enforcing quality control over hydrophobic precursor proteins that have mislocalized to the cytosol, directing them to either productive membrane insertion or selective ubiquitination and proteasomal degradation.
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91
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Lin SY, Vollrath MA, Mangosing S, Shen J, Cardenas E, Corey DP. The zebrafish pinball wizard gene encodes WRB, a tail-anchored-protein receptor essential for inner-ear hair cells and retinal photoreceptors. J Physiol 2015; 594:895-914. [PMID: 26593130 DOI: 10.1113/jp271437] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 11/17/2015] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The zebrafish pinball wizard (pwi) mutant is deaf and blind. The pwi phenotype includes a reduced auditory startle response and reduced visual evoked potentials, suggesting fatigue of synaptic release at ribbon synapses in hair cells and photoreceptors. The gene defective in the pwi mutant is WRB, a protein homologous to the yeast protein Get1, which is involved in the insertion of 'tail-anchored' membrane proteins. Many tail-anchored proteins are associated with synaptic vesicles, and both vesicles and synaptic ribbons are reduced in synaptic regions of hair cells in pwi. Abnormal processing of synaptic vesicle proteins important for ribbon synapses can explain the pwi phenotype. ABSTRACT In a large-scale zebrafish insertional mutagenesis screen, we identified the pinball wizard (pwi) line, which displays a deafness and blindness phenotype. Although the gross morphology and structure of the pwi larval inner ear was near normal, acoustic startle stimuli evoked smaller postsynaptic responses in afferent neurons, which rapidly fatigued. In the retina, similarly, an abnormal electroretinogram suggested reduced transmission at the photoreceptor ribbon synapse. A functional deficit in these specialized synapses was further supported by a reduction of synaptic marker proteins Rab3 and cysteine-string protein (CSP/Dnajc5) in hair cells and photoreceptors, as well as by a reduction of the number of both ribbons and vesicles surrounding the ribbons in hair cells. The pwi gene encodes a homologue of the yeast Get1 and human tryptophan-rich basic (WRB) proteins, which are receptors for membrane insertion of tail-anchored (TA) proteins. We identified more than 100 TA proteins expressed in hair cells, including many synaptic proteins. The expression of synaptobrevin and syntaxin 3, TA proteins essential for vesicle fusion, was reduced in the synaptic layers of mutant retina, consistent with a role for the pwi/WRB protein in TA-protein processing. The WRB protein was located near the apical domain and the ribbons in hair cells, and in the inner segment and the axon of the photoreceptor, consistent with a role in vesicle biogenesis or trafficking. Taken together, our results suggest that WRB plays a critical role in synaptic functions in these two sensory cells, and that disrupted processing of synaptic vesicle TA proteins explains much of the mutant phenotype.
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Affiliation(s)
- Shuh-Yow Lin
- Department of Surgery, UC San Diego School of Medicine, La Jolla, CA, USA
| | - Melissa A Vollrath
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA.,Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Sara Mangosing
- Department of Surgery, UC San Diego School of Medicine, La Jolla, CA, USA
| | - Jun Shen
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA.,Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Elena Cardenas
- Department of Surgery, UC San Diego School of Medicine, La Jolla, CA, USA
| | - David P Corey
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA.,Howard Hughes Medical Institute, Chevy Chase, MD, USA
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92
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Abstract
Nuclease-based genome editing has proven to be a powerful and promising tool for disease modeling and gene therapy. Recent advances in CRISPR/Cas and TALE indicate that they could also be used as a targeted regulator of gene expression, as well as being utilized for illuminating specific chromosomal structures or genomic regions.
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Affiliation(s)
- Liping Deng
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101 China
| | - Ruotong Ren
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101 China
| | - Jun Wu
- Gene Expression Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037 USA
| | - Keiichiro Suzuki
- Gene Expression Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037 USA
| | - Juan Carlos Izpisua Belmote
- Gene Expression Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037 USA
| | - Guang-Hui Liu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101 China
- Beijing Institute for Brain Disorders, Beijing, 100069 China
- Center for Molecular and Translational Medicine, CMTM, Beijing, 100101 China
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93
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Conserved targeting information in mammalian and fungal peroxisomal tail-anchored proteins. Sci Rep 2015; 5:17420. [PMID: 26627908 PMCID: PMC4667187 DOI: 10.1038/srep17420] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Accepted: 10/22/2015] [Indexed: 11/22/2022] Open
Abstract
The targeting signals and mechanisms of soluble peroxisomal proteins are well understood, whereas less is known about the signals and targeting routes of peroxisomal membrane proteins (PMP). Pex15 and PEX26, tail-anchored proteins in yeast and mammals, respectively, exert a similar cellular function in the recruitment of AAA peroxins at the peroxisomal membrane. But despite their common role, Pex15 and PEX26 are neither homologs nor they are known to follow similar targeting principles. Here we show that Pex15 targets to peroxisomes in mammalian cells, and PEX26 reaches peroxisomes when expressed in yeast cells. In both proteins C-terminal targeting information is sufficient for correct sorting to the peroxisomal membrane. In yeast, PEX26 follows the pathway that also ensures correct targeting of Pex15: PEX26 enters the endoplasmic reticulum (ER) in a GET-dependent and Pex19-independent manner. Like in yeast, PEX26 enters the ER in mammalian cells, however, independently of GET/TRC40. These data show that conserved targeting information is employed in yeast and higher eukaryotes during the biogenesis of peroxisomal tail-anchored proteins.
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94
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Cui XA, Zhang H, Ilan L, Liu AX, Kharchuk I, Palazzo AF. mRNA encoding Sec61β, a tail-anchored protein, is localized on the endoplasmic reticulum. J Cell Sci 2015; 128:3398-410. [PMID: 26272916 PMCID: PMC4582399 DOI: 10.1242/jcs.168583] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 08/04/2015] [Indexed: 12/30/2022] Open
Abstract
Although one pathway for the post-translational targeting of tail-anchored proteins to the endoplasmic reticulum (ER) has been well defined, it is unclear whether additional pathways exist. Here, we provide evidence that a subset of mRNAs encoding tail-anchored proteins, including Sec61β and nesprin-2, is partially localized to the surface of the ER in mammalian cells. In particular, Sec61b mRNA can be targeted to, and later maintained on, the ER using both translation-dependent and -independent mechanisms. Our data suggests that this process is independent of p180 (also known as RRBP1), a known mRNA receptor on the ER, and the transmembrane domain recognition complex (TRC) pathway components, TRC40 (also known as ASNA1) and BAT3 (also known as BAG6). In addition, our data indicates that Sec61b mRNA might access translocon-bound ribosomes. Our results show that certain tail-anchored proteins are likely to be synthesized directly on the ER, and this facilitates their membrane insertion. Thus, it is clear that mammalian cells utilize multiple mechanisms to ensure efficient targeting of tail-anchored proteins to the surface of the ER. Highlighted Article: The mRNA encoding certain tail-anchored proteins is directly localized to the surface of the endoplasmic reticulum, facilitating the insertion of newly synthesized proteins into the membrane.
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Affiliation(s)
- Xianying A Cui
- University of Toronto, Department of Biochemistry, 1 King's College Circle, MSB Room 5336, Toronto, ON, M5S 1A8, Canada
| | - Hui Zhang
- University of Toronto, Department of Biochemistry, 1 King's College Circle, MSB Room 5336, Toronto, ON, M5S 1A8, Canada
| | - Lena Ilan
- University of Toronto, Department of Biochemistry, 1 King's College Circle, MSB Room 5336, Toronto, ON, M5S 1A8, Canada
| | - Ai Xin Liu
- University of Toronto, Department of Biochemistry, 1 King's College Circle, MSB Room 5336, Toronto, ON, M5S 1A8, Canada
| | - Iryna Kharchuk
- University of Toronto, Department of Biochemistry, 1 King's College Circle, MSB Room 5336, Toronto, ON, M5S 1A8, Canada
| | - Alexander F Palazzo
- University of Toronto, Department of Biochemistry, 1 King's College Circle, MSB Room 5336, Toronto, ON, M5S 1A8, Canada
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95
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Yamamoto Y, Sakisaka T. The emerging role of calcium-modulating cyclophilin ligand in posttranslational insertion of tail-anchored proteins into the endoplasmic reticulum membrane. J Biochem 2015; 157:419-29. [PMID: 25869254 DOI: 10.1093/jb/mvv035] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2015] [Accepted: 02/18/2015] [Indexed: 01/08/2023] Open
Abstract
Tail-anchored (TA) proteins, a class of membrane proteins having an N-terminal cytoplasmic region anchored to the membrane by a single C-terminal transmembrane domain, are posttranslationally inserted into the endoplasmic reticulum (ER) membrane. In yeasts, the posttranslational membrane insertion is mediated by the Guided Entry of TA Proteins (GET) complex. Get3, a cytosolic ATPase, targets newly synthesized TA proteins to the ER membrane, where Get2 and Get3 constitute the Get3 receptor driving the membrane insertion. While mammalian cells employ TRC40 and WRB, mammalian homologs of Get3 and Get1, respectively, they lack the gene homologous to Get2. We recently identified calcium-modulating cyclophilin ligand (CAML) as a TRC40 receptor, indicating that CAML was equivalent to Get2 in the context of the membrane insertion. On the other hand, CAML has been well characterized as a signaling molecule that regulates various biological processes, raising the question of how the two distinct actions of CAML, the membrane insertion and the signal transduction, are assembled. In this review, we summarize recent progress of the molecular mechanism of the membrane insertion of TA proteins and discuss the possibility that CAML could sense the various signals at the ER membrane, thereby controlling TA protein biogenesis.
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Affiliation(s)
- Yasunori Yamamoto
- Division of Membrane Dynamics, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
| | - Toshiaki Sakisaka
- Division of Membrane Dynamics, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
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96
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Mateja A, Paduch M, Chang HY, Szydlowska A, Kossiakoff AA, Hegde RS, Keenan RJ. Protein targeting. Structure of the Get3 targeting factor in complex with its membrane protein cargo. Science 2015; 347:1152-5. [PMID: 25745174 PMCID: PMC4413028 DOI: 10.1126/science.1261671] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Tail-anchored (TA) proteins are a physiologically important class of membrane proteins targeted to the endoplasmic reticulum by the conserved guided-entry of TA proteins (GET) pathway. During transit, their hydrophobic transmembrane domains (TMDs) are chaperoned by the cytosolic targeting factor Get3, but the molecular nature of the functional Get3-TA protein targeting complex remains unknown. We reconstituted the physiologic assembly pathway for a functional targeting complex and showed that it comprises a TA protein bound to a Get3 homodimer. Crystal structures of Get3 bound to different TA proteins showed an α-helical TMD occupying a hydrophobic groove that spans the Get3 homodimer. Our data elucidate the mechanism of TA protein recognition and shielding by Get3 and suggest general principles of hydrophobic domain chaperoning by cellular targeting factors.
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Affiliation(s)
- Agnieszka Mateja
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Marcin Paduch
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Hsin-Yang Chang
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Anna Szydlowska
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Anthony A Kossiakoff
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Ramanujan S Hegde
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK.
| | - Robert J Keenan
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA.
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97
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Chen Y, Pieuchot L, Loh RA, Yang J, Kari TMA, Wong JY, Jedd G. Hydrophobic handoff for direct delivery of peroxisome tail-anchored proteins. Nat Commun 2014; 5:5790. [PMID: 25517356 DOI: 10.1038/ncomms6790] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Accepted: 11/04/2014] [Indexed: 02/06/2023] Open
Abstract
Tail-anchored (TA) proteins are inserted into membranes post-translationally through a C-terminal transmembrane domain (TMD). The PEX19 protein binds peroxisome TA proteins in the cytoplasm and delivers them to the membrane through the PEX3 receptor protein. An amphipathic segment in PEX19 promotes docking on PEX3. However, how this leads to substrate insertion is unknown. Here we reconstitute peroxisome TA protein biogenesis into two sequential steps of substrate TMD engagement and membrane insertion. We identify a series of previously uncharacterized amphipathic segments in PEX19 and identify one whose hydrophobicity is required for membrane insertion, but not TMD chaperone activity or PEX3 binding. A membrane-proximal hydrophobic surface of PEX3 promotes an unconventional form of membrane intercalation, and is also required for TMD insertion. Together, these data support a mechanism in which hydrophobic moieties in the TMD chaperone and its membrane-associated receptor act in a concerted manner to prompt TMD release and membrane insertion.
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Affiliation(s)
- Yinxiao Chen
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Laurent Pieuchot
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Rachel Ann Loh
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Jing Yang
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Teuku Mahfuzh Aufar Kari
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Jie Yun Wong
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Gregory Jedd
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
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