1
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Abstract
The endoplasmic reticulum (ER) is the site of membrane protein insertion, folding, and assembly in eukaryotes. Over the past few years, a combination of genetic and biochemical studies have implicated an abundant factor termed the ER membrane protein complex (EMC) in several aspects of membrane protein biogenesis. This large nine-protein complex is built around a deeply conserved core formed by the EMC3-EMC6 subcomplex. EMC3 belongs to the universally conserved Oxa1 superfamily of membrane protein transporters, whereas EMC6 is an ancient, widely conserved obligate partner. EMC has an established role in the insertion of transmembrane domains (TMDs) and less understood roles during the later steps of membrane protein folding and assembly. Several recent structures suggest hypotheses about the mechanism(s) of TMD insertion by EMC, with various biochemical and proteomics studies beginning to reveal the range of EMC's membrane protein substrates. Expected final online publication date for the Annual Review of Biochemistry, Volume 91 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Ramanujan S Hegde
- Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom;
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2
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Jung SJ, Kim H. Emerging View on the Molecular Functions of Sec62 and Sec63 in Protein Translocation. Int J Mol Sci 2021; 22:ijms222312757. [PMID: 34884562 PMCID: PMC8657602 DOI: 10.3390/ijms222312757] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 11/23/2021] [Accepted: 11/23/2021] [Indexed: 12/18/2022] Open
Abstract
Most secreted and membrane proteins are targeted to and translocated across the endoplasmic reticulum (ER) membrane through the Sec61 protein-conducting channel. Evolutionarily conserved Sec62 and Sec63 associate with the Sec61 channel, forming the Sec complex and mediating translocation of a subset of proteins. For the last three decades, it has been thought that ER protein targeting and translocation occur via two distinct pathways: signal recognition particle (SRP)-dependent co-translational or SRP-independent, Sec62/Sec63 dependent post-translational translocation pathway. However, recent studies have suggested that ER protein targeting and translocation through the Sec translocon are more intricate than previously thought. This review summarizes the current understanding of the molecular functions of Sec62/Sec63 in ER protein translocation.
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Affiliation(s)
| | - Hyun Kim
- Correspondence: ; Tel.: +82-2-880-4440; Fax: +82-2-872-1993
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3
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Jung SJ, Kim JEH, Junne T, Spiess M, Kim H. Cotranslational Targeting and Posttranslational Translocation can Cooperate in Spc3 Topogenesis. J Mol Biol 2021; 433:167109. [PMID: 34153287 DOI: 10.1016/j.jmb.2021.167109] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 06/11/2021] [Accepted: 06/11/2021] [Indexed: 11/19/2022]
Abstract
Secretory and membrane proteins follow either the signal recognition particle (SRP)-dependent cotranslational translocation pathway or the SRP-independent Sec62/Sec63-dependent posttranslational pathway for their translocation across the endoplasmic reticulum (ER). However, increasing evidence suggests that most proteins are cotranslationally targeted to the ER, suggesting mixed mechanisms. It remains unclear how these two pathways cooperate. Previous studies have shown that Spc3, a signal-anchored protein, requires SRP and Sec62 for its biogenesis. This study investigated the targeting and topogenesis of Spc3 and the step at which SRP and Sec62 act using in vivo and in vitro translocation assays and co-immunoprecipitation. Our data suggest that Spc3 reaches its final topology in two steps: it enters the ER lumen head-first and then inverts its orientation. The first step is partially dependent on SRP, although independent of the Sec62/Sec63 complex. The second step is mediated by the Sec62/Sec63 complex. These data suggest that SRP and Sec62 act on a distinct step in the topogenesis of Spc3.
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Affiliation(s)
- Sung-Jun Jung
- School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul 08826, South Korea
| | - Ji Eun Hani Kim
- School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul 08826, South Korea
| | - Tina Junne
- Biozentrum, University of Basel, Basel, Switzerland
| | | | - Hyun Kim
- School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul 08826, South Korea.
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4
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Arneth B. Insulin gene mutations and posttranslational and translocation defects: associations with diabetes. Endocrine 2020; 70:488-497. [PMID: 32656694 DOI: 10.1007/s12020-020-02413-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Accepted: 07/01/2020] [Indexed: 02/06/2023]
Abstract
The mechanism underlying the pathogenesis of diabetes is complex and poorly understood. Recent investigations have revealed that insulin gene mutations can lead to the development of specific subtypes of diabetes. This systematic review aimed to explore the associations of insulin gene mutations and insulin translocation defects with diabetes. This review was generated using articles from PsycINFO, PubMed, Web of Science, and CINAHL. Search terms and phrases such as "diabetes," "mutations," "insulin," "preproinsulin," "INS gene," "role," "VNTR polymorphisms," and "INS promotor" were used to identify articles relevant to the research topic. The gathered data showed the significant role of insulin gene mutations and insulin translocation defects during diabetes development and progression. Genetic changes can adversely affect the development of various types of diabetes, such as neonatal diabetes mellitus and MIDY. Genetic alterations can affect insulin production, thus compromising the regulation of glucose utilization by tissues. Targeting insulin gene mutations is a potential new avenue for diagnosing and managing diabetes. There are specific subcategories of diabetes, such as MIDY and neonatal diabetes mellitus, caused by insulin gene mutations and defects in posttranslational modification. Further investigations are needed to examine the diagnostic and therapeutic potential of mutation-based biomarkers.
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Affiliation(s)
- Borros Arneth
- Institute of Laboratory Medicine and Pathobiochemistry, Molecular Diagnostics, University Hospital of Giessen and Marburg (UKGM), Justus Liebig University Giessen, Feulgenstr 12, 35332, Giessen, Germany.
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5
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Abstract
In eukaryotic cells, about one-third of the synthesized proteins are translocated into the endoplasmic reticulum; they are membrane or lumen resident proteins and proteins direct to the Golgi apparatus. The co-translational translocation takes place through the heterotrimeric protein-conducting channel Sec61 which is associated with the ribosome and many accessory components, such as the heterotetrameric translocon-associated protein (TRAP) complex. Recently, microscopic techniques, such as cryo-electron microscopy and cryo-electron tomography, have enabled the determination of the translocation machinery structure. However, at present, there is a lack of understanding regarding the roles of some of its components; indeed, the TRAP complex function during co-translational translocation needs to be established. In addition, TRAP may play a role during unfolded protein response, endoplasmic-reticulum-associated protein degradation and congenital disorder of glycosylation (ssr4 CDG). In this article, I describe the current understanding of the TRAP complex in the light of its possible function(s).
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Affiliation(s)
- Antonietta Russo
- Medical Biochemistry and Molecular Biology, UKS, University of Saarland, Homburg, Germany
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6
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Van Puyenbroeck V, Pauwels E, Provinciael B, Bell TW, Schols D, Kalies KU, Hartmann E, Vermeire K. Preprotein signature for full susceptibility to the co-translational translocation inhibitor cyclotriazadisulfonamide. Traffic 2019; 21:250-264. [PMID: 31675144 DOI: 10.1111/tra.12713] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 10/24/2019] [Accepted: 10/26/2019] [Indexed: 01/13/2023]
Abstract
Cyclotriazadisulfonamide (CADA) inhibits the co-translational translocation of human CD4 (huCD4) into the endoplasmic reticulum lumen in a signal peptide (SP)-dependent way. We propose that CADA binds the nascent huCD4 SP in a folded conformation within the translocon resembling a normally transitory state during translocation. Here, we used alanine scanning on the huCD4 SP to identify the signature for full susceptibility to CADA. In accordance with our previous work, we demonstrate that residues in the vicinity of the hydrophobic h-region are critical for sensitivity to CADA. In particular, exchanging Gln-15, Val-17 or Pro-20 in the huCD4 SP for Ala resulted in a resistant phenotype. Together with positively charged residues at the N-terminal portion of the mature protein, these residues mediate full susceptibility to the co-translational translocation inhibitory activity of CADA towards huCD4. In addition, sensitivity to CADA is inversely related to hydrophobicity in the huCD4 SP. In vitro translocation experiments confirmed that the general hydrophobicity of the h-domain and positive charges in the mature protein are key elements that affect both the translocation efficiency of huCD4 and the sensitivity towards CADA. Besides these two general SP parameters that determine the functionality of the signal sequence, unique amino acid pairs (L14/Q15 and L19/P20) in the SP hydrophobic core add specificity to the sensitivity signature for a co-translational translocation inhibitor.
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Affiliation(s)
- Victor Van Puyenbroeck
- KU Leuven Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Laboratory of Virology and Chemotherapy, Leuven, Belgium
| | - Eva Pauwels
- KU Leuven Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Laboratory of Virology and Chemotherapy, Leuven, Belgium
| | - Becky Provinciael
- KU Leuven Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Laboratory of Virology and Chemotherapy, Leuven, Belgium
| | - Thomas W Bell
- Department of Chemistry, University of Nevada, Reno, Nevada
| | - Dominique Schols
- KU Leuven Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Laboratory of Virology and Chemotherapy, Leuven, Belgium
| | - Kai-Uwe Kalies
- Centre for Structural and Cell Biology in Medicine, Institute of Biology, University of Lübeck, Lübeck, Germany
| | - Enno Hartmann
- Centre for Structural and Cell Biology in Medicine, Institute of Biology, University of Lübeck, Lübeck, Germany
| | - Kurt Vermeire
- KU Leuven Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, Laboratory of Virology and Chemotherapy, Leuven, Belgium
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7
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Spiess M, Junne T, Janoschke M. Membrane Protein Integration and Topogenesis at the ER. Protein J 2019; 38:306-316. [DOI: 10.1007/s10930-019-09827-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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8
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Yim C, Jung SJ, Kim JEH, Jung Y, Jeong SD, Kim H. Profiling of signal sequence characteristics and requirement of different translocation components. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2018; 1865:1640-1648. [DOI: 10.1016/j.bbamcr.2018.08.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 08/23/2018] [Accepted: 08/27/2018] [Indexed: 11/25/2022]
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9
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Niesen MJM, Wang CY, Van Lehn RC, Miller TF. Structurally detailed coarse-grained model for Sec-facilitated co-translational protein translocation and membrane integration. PLoS Comput Biol 2017; 13:e1005427. [PMID: 28328943 PMCID: PMC5381951 DOI: 10.1371/journal.pcbi.1005427] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 04/05/2017] [Accepted: 02/28/2017] [Indexed: 01/05/2023] Open
Abstract
We present a coarse-grained simulation model that is capable of simulating the minute-timescale dynamics of protein translocation and membrane integration via the Sec translocon, while retaining sufficient chemical and structural detail to capture many of the sequence-specific interactions that drive these processes. The model includes accurate geometric representations of the ribosome and Sec translocon, obtained directly from experimental structures, and interactions parameterized from nearly 200 μs of residue-based coarse-grained molecular dynamics simulations. A protocol for mapping amino-acid sequences to coarse-grained beads enables the direct simulation of trajectories for the co-translational insertion of arbitrary polypeptide sequences into the Sec translocon. The model reproduces experimentally observed features of membrane protein integration, including the efficiency with which polypeptide domains integrate into the membrane, the variation in integration efficiency upon single amino-acid mutations, and the orientation of transmembrane domains. The central advantage of the model is that it connects sequence-level protein features to biological observables and timescales, enabling direct simulation for the mechanistic analysis of co-translational integration and for the engineering of membrane proteins with enhanced membrane integration efficiency.
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Affiliation(s)
- Michiel J. M. Niesen
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, United States of America
| | - Connie Y. Wang
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, United States of America
| | - Reid C. Van Lehn
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, United States of America
| | - Thomas F. Miller
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, United States of America
- * E-mail:
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10
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McKenna M, Simmonds RE, High S. Mycolactone reveals the substrate-driven complexity of Sec61-dependent transmembrane protein biogenesis. J Cell Sci 2017; 130:1307-1320. [PMID: 28219954 PMCID: PMC5399781 DOI: 10.1242/jcs.198655] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 02/02/2017] [Indexed: 12/22/2022] Open
Abstract
Mycolactone is the exotoxin virulence factor produced by Mycobacterium ulcerans, the pathogen responsible for Buruli ulcer. The skin lesions and immunosuppression that are characteristic of this disease result from the action of mycolactone, which targets the Sec61 complex and inhibits the co-translational translocation of secretory proteins into the endoplasmic reticulum. In this study, we investigate the effect of mycolactone on the Sec61-dependent biogenesis of different classes of transmembrane protein (TMP). Our data suggest that the effect of mycolactone on TMP biogenesis depends on how the nascent chain initially engages the Sec61 complex. For example, the translocation of TMP lumenal domains driven by an N-terminal cleavable signal sequence is efficiently inhibited by mycolactone. In contrast, the effect of mycolactone on protein translocation that is driven solely by a non-cleavable signal anchor/transmembrane domain depends on which flanking region is translocated. For example, while translocation of the region N-terminal to a signal anchor/transmembrane domain is refractive to mycolactone, C-terminal translocation is efficiently inhibited. Our findings highlight the diversity of Sec61-dependent translocation and provide a molecular basis for understanding the effect of mycolactone on the biogenesis of different TMPs. Highlighted Article: The exotoxin mycolactone interferes with the biogenesis of the majority of transmembrane proteins and its actions highlight differences in how distinct classes of these proteins initially engage the Sec61 translocon.
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Affiliation(s)
- 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
| | - Rachel E Simmonds
- Department of Microbial Sciences, School of Bioscience and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7XH, UK
| | - 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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11
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Chawla R, Van Puyenbroeck V, Pflug NC, Sama A, Ali R, Schols D, Vermeire K, Bell TW. Tuning Side Arm Electronics in Unsymmetrical Cyclotriazadisulfonamide (CADA) Endoplasmic Reticulum (ER) Translocation Inhibitors to Improve their Human Cluster of Differentiation 4 (CD4) Receptor Down-Modulating Potencies. J Med Chem 2016; 59:2633-47. [PMID: 26974263 DOI: 10.1021/acs.jmedchem.5b01832] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cyclotriazadisulfonamide prevents HIV entry into cells by down-modulating surface CD4 receptor expression through binding to the CD4 signal peptide. According to a two-site binding model, 28 new unsymmetrical analogues bearing a benzyl tail group and nine bearing a cyclohexylmethyl tail have been designed and synthesized. The most potent new CD4 down-modulator (40 (CK147); IC50 63 nM) has a 4-dimethylaminobenzenesulfonyl side arm. One of the two side arms was varied with substituents in different positions. This gave a range of CD4 down-modulation potencies that correlated well with anti-HIV-1 activities. The side arms of 21 of the new benzyl-tailed analogues were modeled by means of quantum mechanical calculations. For CADA analogues with arenesulfonamide side arms, the pIC50 values for CD4 down-modulation correlated with the component of the electric dipole moment in the aromatic ring, suggesting that an attractive electronic interaction is a major factor determining the stability of the complex between the molecule and its target.
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Affiliation(s)
- Reena Chawla
- Department of Chemistry, University of Nevada , 1664 North Virginia Street, Reno, Nevada 89557-0216 United States
| | - Victor Van Puyenbroeck
- Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Virology and Chemotherapy, KU Leuven-University of Leuven , 3000 Leuven, Belgium
| | - Nicholas C Pflug
- Department of Chemistry, University of Nevada , 1664 North Virginia Street, Reno, Nevada 89557-0216 United States
| | - Alekhya Sama
- Department of Chemistry, University of Nevada , 1664 North Virginia Street, Reno, Nevada 89557-0216 United States
| | - Rameez Ali
- Department of Chemistry, University of Nevada , 1664 North Virginia Street, Reno, Nevada 89557-0216 United States
| | - Dominique Schols
- Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Virology and Chemotherapy, KU Leuven-University of Leuven , 3000 Leuven, Belgium
| | - Kurt Vermeire
- Department of Microbiology and Immunology, Rega Institute for Medical Research, Laboratory of Virology and Chemotherapy, KU Leuven-University of Leuven , 3000 Leuven, Belgium
| | - Thomas W Bell
- Department of Chemistry, University of Nevada , 1664 North Virginia Street, Reno, Nevada 89557-0216 United States
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12
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Junne T, Spiess M. Integration of transmembrane domains is regulated by their downstream sequences. J Cell Sci 2016; 130:372-381. [DOI: 10.1242/jcs.194472] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 11/10/2016] [Indexed: 12/31/2022] Open
Abstract
The Sec61 translocon catalyzes translocation of proteins into the endoplasmic reticulum and the lateral integration of transmembrane segments into the lipid bilayer. Integration is mediated by the hydrophobicity of a polypeptide segment consistent with thermodynamic equilibration between the translocon and the lipid membrane. Integration efficiency of a generic series of increasingly hydrophobic sequences (H-segments) was found to diverge significantly in different reporter constructs as a function of the ∼100 residues carboxyterminal of the H-segments. The hydrophobicity threshold of integration was considerably lowered by insertion of generic ∼20-residue peptides either made of flexible glycine-serine repeats, containing multiple negative charges, or consisting of an oligo-proline stretch. A highly flexible, 100-residue glycine-serine stretch maximally enhanced this effect. The apparent free energy of integration was found to be changed by more than 3 kcal/mol with the downstream sequences tested. The C-terminal sequences could also be shown to affect integration of natural mildly hydrophobic sequences. The results suggest that the conformation of the nascent polypeptide in the protected cavity between ribosome and translocon significantly influences the release of the H-segment into the bilayer.
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Affiliation(s)
- Tina Junne
- Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland
| | - Martin Spiess
- Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland
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13
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Liu M, Sun J, Cui J, Chen W, Guo H, Barbetti F, Arvan P. INS-gene mutations: from genetics and beta cell biology to clinical disease. Mol Aspects Med 2014; 42:3-18. [PMID: 25542748 DOI: 10.1016/j.mam.2014.12.001] [Citation(s) in RCA: 91] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 12/02/2014] [Accepted: 12/04/2014] [Indexed: 02/06/2023]
Abstract
A growing list of insulin gene mutations causing a new form of monogenic diabetes has drawn increasing attention over the past seven years. The mutations have been identified in the untranslated regions of the insulin gene as well as the coding sequence of preproinsulin including within the signal peptide, insulin B-chain, C-peptide, insulin A-chain, and the proteolytic cleavage sites both for signal peptidase and the prohormone convertases. These mutations affect a variety of different steps of insulin biosynthesis in pancreatic beta cells. Importantly, although many of these mutations cause proinsulin misfolding with early onset autosomal dominant diabetes, some of the mutant alleles appear to engage different cellular and molecular mechanisms that underlie beta cell failure and diabetes. In this article, we review the most recent advances in the field and discuss challenges as well as potential strategies to prevent/delay the development and progression of autosomal dominant diabetes caused by INS-gene mutations. It is worth noting that although diabetes caused by INS gene mutations is rare, increasing evidence suggests that defects in the pathway of insulin biosynthesis may also be involved in the progression of more common types of diabetes. Collectively, the (pre)proinsulin mutants provide insightful molecular models to better understand the pathogenesis of all forms of diabetes in which preproinsulin processing defects, proinsulin misfolding, and ER stress are involved.
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Affiliation(s)
- Ming Liu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, 300052, China; Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI, 48105, USA.
| | - Jinhong Sun
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI, 48105, USA
| | - Jinqiu Cui
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, 300052, China
| | - Wei Chen
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI, 48105, USA
| | - Huan Guo
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI, 48105, USA
| | - Fabrizio Barbetti
- Department of Experimental Medicine, University of Tor Vergata, Rome and Bambino Gesù Children's Hospital, Rome, Italy
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI, 48105, USA.
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14
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Vermeire K, Bell TW, Van Puyenbroeck V, Giraut A, Noppen S, Liekens S, Schols D, Hartmann E, Kalies KU, Marsh M. Signal peptide-binding drug as a selective inhibitor of co-translational protein translocation. PLoS Biol 2014; 12:e1002011. [PMID: 25460167 PMCID: PMC4251836 DOI: 10.1371/journal.pbio.1002011] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Accepted: 10/21/2014] [Indexed: 11/24/2022] Open
Abstract
In eukaryotic cells, surface expression of most type I transmembrane proteins requires translation and simultaneous insertion of the precursor protein into the endoplasmic reticulum (ER) membrane for subsequent routing to the cell surface. This co-translational translocation pathway is initiated when a hydrophobic N-terminal signal peptide (SP) on the nascent protein emerges from the ribosome, binds the cytosolic signal recognition particle (SRP), and targets the ribosome-nascent chain complex to the Sec61 translocon, a universally conserved protein-conducting channel in the ER-membrane. Despite their common function in Sec61 targeting and ER translocation, SPs have diverse but unique primary sequences. Thus, drugs that recognise SPs could be exploited to inhibit translocation of specific proteins into the ER. Here, through flow cytometric analysis the small-molecule macrocycle cyclotriazadisulfonamide (CADA) is identified as a highly selective human CD4 (hCD4) down-modulator. We show that CADA inhibits CD4 biogenesis and that this is due to its ability to inhibit co-translational translocation of CD4 into the lumen of the ER, both in cells as in a cell-free in vitro translation/translocation system. The activity of CADA maps to the cleavable N-terminal SP of hCD4. Moreover, through surface plasmon resonance analysis we were able to show direct binding of CADA to the SP of hCD4 and identify this SP as the target of our drug. Furthermore, CADA locks the SP in the translocon during a post-targeting step, possibly in a folded state, and prevents the translocation of the associated protein into the ER lumen. Instead, the precursor protein is routed to the cytosol for degradation. These findings demonstrate that a synthetic, cell-permeable small-molecule can be developed as a SP-binding drug to selectively inhibit protein translocation and to reversibly regulate the expression of specific target proteins.
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Affiliation(s)
- Kurt Vermeire
- KU Leuven – University of Leuven, Department of Microbiology and Immunology, Virology and Chemotherapy, Rega Institute for Medical Research, Leuven, Belgium
- Institute of Biology, CSCM, University of Lübeck, Lübeck, Germany
- MRC-Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
| | - Thomas W. Bell
- Department of Chemistry, University of Nevada, Reno, Nevada, United States of America
| | - Victor Van Puyenbroeck
- KU Leuven – University of Leuven, Department of Microbiology and Immunology, Virology and Chemotherapy, Rega Institute for Medical Research, Leuven, Belgium
| | - Anne Giraut
- KU Leuven – University of Leuven, Department of Microbiology and Immunology, Virology and Chemotherapy, Rega Institute for Medical Research, Leuven, Belgium
| | - Sam Noppen
- KU Leuven – University of Leuven, Department of Microbiology and Immunology, Virology and Chemotherapy, Rega Institute for Medical Research, Leuven, Belgium
| | - Sandra Liekens
- KU Leuven – University of Leuven, Department of Microbiology and Immunology, Virology and Chemotherapy, Rega Institute for Medical Research, Leuven, Belgium
| | - Dominique Schols
- KU Leuven – University of Leuven, Department of Microbiology and Immunology, Virology and Chemotherapy, Rega Institute for Medical Research, Leuven, Belgium
| | - Enno Hartmann
- Institute of Biology, CSCM, University of Lübeck, Lübeck, Germany
| | - Kai-Uwe Kalies
- Institute of Biology, CSCM, University of Lübeck, Lübeck, Germany
| | - Mark Marsh
- MRC-Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
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15
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Dou D, da Silva DV, Nordholm J, Wang H, Daniels R. Type II transmembrane domain hydrophobicity dictates the cotranslational dependence for inversion. Mol Biol Cell 2014; 25:3363-74. [PMID: 25165139 PMCID: PMC4214783 DOI: 10.1091/mbc.e14-04-0874] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The cellular hydrophobicity threshold for the inversion of Sec-dependent Nin-Cout (type II) transmembrane domains is dictated by whether their membrane integration occurs cotranslationally or posttranslationally. Membrane insertion by the Sec61 translocon in the endoplasmic reticulum (ER) is highly dependent on hydrophobicity. This places stringent hydrophobicity requirements on transmembrane domains (TMDs) from single-spanning membrane proteins. On examining the single-spanning influenza A membrane proteins, we found that the strict hydrophobicity requirement applies to the Nout-Cin HA and M2 TMDs but not the Nin-Cout TMDs from the type II membrane protein neuraminidase (NA). To investigate this discrepancy, we analyzed NA TMDs of varying hydrophobicity, followed by increasing polypeptide lengths, in mammalian cells and ER microsomes. Our results show that the marginally hydrophobic NA TMDs (ΔGapp > 0 kcal/mol) require the cotranslational insertion process for facilitating their inversion during translocation and a positively charged N-terminal flanking residue and that NA inversion enhances its plasma membrane localization. Overall the cotranslational inversion of marginally hydrophobic NA TMDs initiates once ∼70 amino acids past the TMD are synthesized, and the efficiency reaches 50% by ∼100 amino acids, consistent with the positioning of this TMD class in type II human membrane proteins. Inversion of the M2 TMD, achieved by elongating its C-terminus, underscores the contribution of cotranslational synthesis to TMD inversion.
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Affiliation(s)
- Dan Dou
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University,
SE-106 91 Stockholm, Sweden
| | - Diogo V da Silva
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University,
SE-106 91 Stockholm, Sweden
| | - Johan Nordholm
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University,
SE-106 91 Stockholm, Sweden
| | - Hao Wang
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University,
SE-106 91 Stockholm, Sweden
| | - Robert Daniels
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University,
SE-106 91 Stockholm, Sweden
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16
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Lee H, Kim H. Membrane topology of transmembrane proteins: determinants and experimental tools. Biochem Biophys Res Commun 2014; 453:268-76. [PMID: 24938127 DOI: 10.1016/j.bbrc.2014.05.111] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2014] [Accepted: 05/27/2014] [Indexed: 10/25/2022]
Abstract
Membrane topology refers to the two-dimensional structural information of a membrane protein that indicates the number of transmembrane (TM) segments and the orientation of soluble domains relative to the plane of the membrane. Since membrane proteins are co-translationally translocated across and inserted into the membrane, the TM segments orient themselves properly in an early stage of membrane protein biogenesis. Each membrane protein must contain some topogenic signals, but the translocation components and the membrane environment also influence the membrane topology of proteins. We discuss the factors that affect membrane protein orientation and have listed available experimental tools that can be used in determining membrane protein topology.
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Affiliation(s)
- Hunsang Lee
- School of Biological Sciences, Seoul National University, Seoul 151-747, South Korea
| | - Hyun Kim
- School of Biological Sciences, Seoul National University, Seoul 151-747, South Korea.
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17
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Guo H, Xiong Y, Witkowski P, Cui J, Wang LJ, Sun J, Lara-Lemus R, Haataja L, Hutchison K, Shan SO, Arvan P, Liu M. Inefficient translocation of preproinsulin contributes to pancreatic β cell failure and late-onset diabetes. J Biol Chem 2014; 289:16290-302. [PMID: 24770419 DOI: 10.1074/jbc.m114.562355] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Among the defects in the early events of insulin biosynthesis, proinsulin misfolding and endoplasmic reticulum (ER) stress have drawn increasing attention as causes of β cell failure. However, no studies have yet addressed potential defects at the cytosolic entry point of preproinsulin into the secretory pathway. Here, we provide the first evidence that inefficient translocation of preproinsulin (caused by loss of a positive charge in the n region of its signal sequence) contributes to β cell failure and diabetes. Specifically, we find that, after targeting to the ER membrane, preproinsulin signal peptide (SP) mutants associated with autosomal dominant late-onset diabetes fail to be fully translocated across the ER membrane. The newly synthesized, untranslocated preproinsulin remains strongly associated with the ER membrane, exposing its proinsulin moiety to the cytosol. Rather than accumulating in the ER and inducing ER stress, untranslocated preproinsulin accumulates in a juxtanuclear compartment distinct from the Golgi complex, induces the expression of heat shock protein 70 (HSP70), and promotes β cell death. Restoring an N-terminal positive charge to the mutant preproinsulin SP significantly improves the translocation defect. These findings not only reveal a novel molecular pathogenesis of β cell failure and diabetes but also provide the first evidence of the physiological and pathological significance of the SP n region positive charge of secretory proteins.
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Affiliation(s)
- Huan Guo
- From the Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Yi Xiong
- From the Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Piotr Witkowski
- the Division of Organ Transplantation, University of Chicago, Chicago, Illinois 60637
| | - Jingqing Cui
- From the Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105, the Division of Metabolism, Tianjin Medical University General Hospital, Tianjin, China 300052
| | - Ling-jia Wang
- the Division of Organ Transplantation, University of Chicago, Chicago, Illinois 60637
| | - Jinhong Sun
- From the Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Roberto Lara-Lemus
- From the Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105, the Department of Research in Biochemistry, National Institute of Respiratory Diseases "Ismael Cosío Villegas", Mexico City 14080, Mexico, and
| | - Leena Haataja
- From the Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Kathryn Hutchison
- From the Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
| | - Shu-ou Shan
- the Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125
| | - Peter Arvan
- From the Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105,
| | - Ming Liu
- From the Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105, the Division of Metabolism, Tianjin Medical University General Hospital, Tianjin, China 300052,
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18
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Sommer N, Junne T, Kalies KU, Spiess M, Hartmann E. TRAP assists membrane protein topogenesis at the mammalian ER membrane. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:3104-3111. [DOI: 10.1016/j.bbamcr.2013.08.018] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Revised: 08/26/2013] [Accepted: 08/27/2013] [Indexed: 01/03/2023]
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19
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Reithinger JH, Kim JEH, Kim H. Sec62 protein mediates membrane insertion and orientation of moderately hydrophobic signal anchor proteins in the endoplasmic reticulum (ER). J Biol Chem 2013; 288:18058-67. [PMID: 23632075 DOI: 10.1074/jbc.m113.473009] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Nascent chains are known to be targeted to the endoplasmic reticulum membrane either by a signal recognition particle (SRP)-dependent co-translational or by an SRP-independent post-translational translocation route depending on signal sequences. Using a set of model and cellular proteins carrying an N-terminal signal anchor sequence of controlled hydrophobicity and yeast mutant strains defective in SRP or Sec62 function, the hydrophobicity-dependent targeting efficiency and targeting pathway preference were systematically evaluated. Our results suggest that an SRP-dependent co-translational and an SRP-independent post-translational translocation are not mutually exclusive for signal anchor proteins and that moderately hydrophobic ones require both SRP and Sec62 for proper targeting and translocation to the endoplasmic reticulum. Further, defect in Sec62 selectively reduced signal sequences inserted in an N(in)-C(out) (type II) membrane topology, implying an undiscovered role of Sec62 in regulating the orientation of the signal sequence in an early stage of translocation.
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