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Johnsen C, Tabatadze N, Radenkovic S, Botzo G, Kuschel B, Melikishvili G, Morava E. SSR4-CDG, an ultra-rare X-linked congenital disorder of glycosylation affecting the TRAP complex: Review of 22 affected individuals including the first adult patient. Mol Genet Metab 2024; 142:108477. [PMID: 38805916 DOI: 10.1016/j.ymgme.2024.108477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2024] [Revised: 04/12/2024] [Accepted: 04/16/2024] [Indexed: 05/30/2024]
Abstract
Congenital disorders of glycosylation (CDG) are a group of rare, often multi-systemic genetic disorders that result from disturbed protein and lipid glycosylation. SSR4-CDG is an ultra-rare, comparably mild subtype of CDG, presenting mostly in males. It is caused by pathogenic variants in the SSR4 gene, which is located on the X chromosome. SSR4 (signal sequence receptor protein 4) is a subunit of the translocon-associated protein (TRAP) complex, a structure that is needed for the translocation of proteins across the ER membrane. A deficiency of SSR4 leads to disturbed N-linked glycosylation of proteins in the endoplasmic reticulum. Here, we review the most common clinical, biochemical and genetic features of 18 previously published individuals and report four new cases diagnosed with SSR4-CDG, including the first adult affected by this disorder. Based on our review, developmental delay, speech delay, intellectual disability, muscular hypotonia, microcephaly and distinct facial features are key symptoms of SSR4-CDG that are present in all affected individuals. Although these symptoms overlap with many other neurodevelopmental disorders, their combination with additional clinical features, and a quite distinguishable facial appearance of affected individuals make this disorder a potentially recognizable type of CDG. Additional signs and symptoms include failure to thrive, feeding difficulties, connective tissue involvement, gastrointestinal problems, skeletal abnormalities, seizures and, in some cases, significant behavioral abnormalities. Due to lack of awareness of this rare disorder, and since biochemical testing can be normal in affected individuals, most are diagnosed through genetic studies, such as whole exome sequencing. With this article, we expand the phenotype of SSR4-CDG to include cardiac symptoms, laryngeal abnormalities, and teleangiectasia. We also provide insights into the prognosis into early adulthood and offer recommendations for adequate management and care. We emphasize the great need for causal therapies, as well as effective symptomatic therapies addressing the multitude of symptoms in this disease. In particular, behavioral problems can severely affect quality of life in individuals diagnosed with SSR4-CDG and need special attention. Finally, we aim to improve guidance and education for affected families and treating physicians and create a basis for future research in this disorder.
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Affiliation(s)
- Christin Johnsen
- Department of Pediatrics and Adolescent Medicine, Division of Pediatric Neurology, University Medical Center Göttingen, Georg August University, Göttingen, Germany; Department of Clinical Genomics, Mayo Clinic, Rochester, MN, USA.
| | - Nazi Tabatadze
- Department of Pediatrics, Medi Club Georgia Medical Center, Tbilisi, Georgia
| | | | - Grace Botzo
- Department of Clinical Genomics, Mayo Clinic, Rochester, MN, USA
| | - Bryce Kuschel
- Department of Clinical Genomics, Mayo Clinic, Rochester, MN, USA
| | - Gia Melikishvili
- Department of Pediatrics, Medi Club Georgia Medical Center, Tbilisi, Georgia
| | - Eva Morava
- Department of Clinical Genomics, Mayo Clinic, Rochester, MN, USA; Department of Genetic and Genomic Sciences, The Icahn School of Medicine at Mount Sinai, NY, USA
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2
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Karki S, Javanainen M, Rehan S, Tranter D, Kellosalo J, Huiskonen JT, Happonen L, Paavilainen V. Molecular view of ER membrane remodeling by the Sec61/TRAP translocon. EMBO Rep 2023; 24:e57910. [PMID: 37983950 DOI: 10.15252/embr.202357910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 10/27/2023] [Accepted: 11/01/2023] [Indexed: 11/22/2023] Open
Abstract
Protein translocation across the endoplasmic reticulum (ER) membrane is an essential step during protein entry into the secretory pathway. The conserved Sec61 protein-conducting channel facilitates polypeptide translocation and coordinates cotranslational polypeptide-processing events. In cells, the majority of Sec61 is stably associated with a heterotetrameric membrane protein complex, the translocon-associated protein complex (TRAP), yet the mechanism by which TRAP assists in polypeptide translocation remains unknown. Here, we present the structure of the core Sec61/TRAP complex bound to a mammalian ribosome by cryogenic electron microscopy (cryo-EM). Ribosome interactions anchor the Sec61/TRAP complex in a conformation that renders the ER membrane locally thinner by significantly curving its lumenal leaflet. We propose that TRAP stabilizes the ribosome exit tunnel to assist nascent polypeptide insertion through Sec61 and provides a ratcheting mechanism into the ER lumen mediated by direct polypeptide interactions.
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Affiliation(s)
- Sudeep Karki
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Matti Javanainen
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Shahid Rehan
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
- Protein Biochemistry and Structural Biology, Omass Therapeutics Ltd, Oxford, UK
| | - Dale Tranter
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Juho Kellosalo
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Juha T Huiskonen
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Lotta Happonen
- Division of Infection Medicine, Department of Clinical Sciences, Lund University, Lund, Sweden
| | - Ville Paavilainen
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
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3
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Jung M, Zimmermann R. Quantitative Mass Spectrometry Characterizes Client Spectra of Components for Targeting of Membrane Proteins to and Their Insertion into the Membrane of the Human ER. Int J Mol Sci 2023; 24:14166. [PMID: 37762469 PMCID: PMC10532041 DOI: 10.3390/ijms241814166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 09/07/2023] [Accepted: 09/12/2023] [Indexed: 09/29/2023] Open
Abstract
To elucidate the redundancy in the components for the targeting of membrane proteins to the endoplasmic reticulum (ER) and/or their insertion into the ER membrane under physiological conditions, we previously analyzed different human cells by label-free quantitative mass spectrometry. The HeLa and HEK293 cells had been depleted of a certain component by siRNA or CRISPR/Cas9 treatment or were deficient patient fibroblasts and compared to the respective control cells by differential protein abundance analysis. In addition to clients of the SRP and Sec61 complex, we identified membrane protein clients of components of the TRC/GET, SND, and PEX3 pathways for ER targeting, and Sec62, Sec63, TRAM1, and TRAP as putative auxiliary components of the Sec61 complex. Here, a comprehensive evaluation of these previously described differential protein abundance analyses, as well as similar analyses on the Sec61-co-operating EMC and the characteristics of the topogenic sequences of the various membrane protein clients, i.e., the client spectra of the components, are reported. As expected, the analysis characterized membrane protein precursors with cleavable amino-terminal signal peptides or amino-terminal transmembrane helices as predominant clients of SRP, as well as the Sec61 complex, while precursors with more central or even carboxy-terminal ones were found to dominate the client spectra of the SND and TRC/GET pathways for membrane targeting. For membrane protein insertion, the auxiliary Sec61 channel components indeed share the client spectra of the Sec61 complex to a large extent. However, we also detected some unexpected differences, particularly related to EMC, TRAP, and TRAM1. The possible mechanistic implications for membrane protein biogenesis at the human ER are discussed and can be expected to eventually advance our understanding of the mechanisms that are involved in the so-called Sec61-channelopathies, resulting from deficient ER protein import.
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Affiliation(s)
| | - Richard Zimmermann
- Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany;
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4
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Timm T, Hild C, Liebisch G, Rickert M, Lochnit G, Steinmeyer J. Functional Characterization of Lysophospholipids by Proteomic and Lipidomic Analysis of Fibroblast-like Synoviocytes. Cells 2023; 12:1743. [PMID: 37443777 PMCID: PMC10340184 DOI: 10.3390/cells12131743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 06/23/2023] [Accepted: 06/27/2023] [Indexed: 07/15/2023] Open
Abstract
Synovial fluid (SF) from human knee joints with osteoarthritis (OA) has elevated levels of lysophosphatidylcholine (LPC) species, but their functional role is not well understood. This in vitro study was designed to test the hypothesis that various LPCs found elevated in OA SF and their metabolites, lysophosphatidic acids (LPAs), modulate the abundance of proteins and phospholipids (PLs) in human fibroblast-like synoviocytes (FLSs), with even minute chemical variations in lysophospholipids determining the extent of regulation. Cultured FLSs (n = 5-7) were treated with one of the LPC species, LPA species, IL-1β, or a vehicle. Tandem mass tag peptide labeling coupled with LC-MS/MS/MS was performed to quantify proteins. The expression of mRNA from regulated proteins was analyzed using RT-PCR. PL synthesis was determined via ESI-MS/MS, and the release of radiolabeled PLs was determined by means of liquid scintillation counting. In total, 3960 proteins were quantified using multiplexed MS, of which 119, 8, and 3 were significantly and reproducibly regulated by IL-1β, LPC 16:0, and LPC 18:0, respectively. LPC 16:0 significantly inhibited the release of PLs and the synthesis of phosphatidylcholine, LPC, and sphingomyelin. Neither LPC metabolite-LPA 16:0 nor LPA 18:0-had any reproducible effect on the levels of each protein. In conclusion, small chemical variations in LPC species can result in the significantly altered expression and secretion of proteins and PLs from FLSs. IL-1β influenced all proteins that were reproducibly regulated by LPC 16:0. LPC species are likely to modulate FLS protein expression only in more advanced OA stages with low IL-1β levels. None of the eight proteins being significantly regulated by LPC 16:0 have been previously reported in OA. However, our in vitro findings show that the CD81 antigen, calumenin, and B4E2C1 are promising candidates for further study, focusing in particular on their potential ability to modulate inflammatory and catabolic mechanisms.
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Affiliation(s)
- Thomas Timm
- Protein Analytics Group, Institute of Biochemistry, Justus Liebig University Giessen, 35392 Giessen, Germany
| | - Christiane Hild
- Laboratory for Experimental Orthopedics, Department of Orthopedics, Justus Liebig University Giessen, 35392 Giessen, Germany
| | - Gerhard Liebisch
- Department for Clinical Chemistry and Laboratory Medicine, University Hospital Regensburg, 93053 Regensburg, Germany
| | - Markus Rickert
- Laboratory for Experimental Orthopedics, Department of Orthopedics, Justus Liebig University Giessen, 35392 Giessen, Germany
| | - Guenter Lochnit
- Protein Analytics Group, Institute of Biochemistry, Justus Liebig University Giessen, 35392 Giessen, Germany
| | - Juergen Steinmeyer
- Laboratory for Experimental Orthopedics, Department of Orthopedics, Justus Liebig University Giessen, 35392 Giessen, Germany
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Pauwels E, Shewakramani NR, De Wijngaert B, Camps A, Provinciael B, Stroobants J, Kalies KU, Hartmann E, Maes P, Vermeire K, Das K. Structural insights into TRAP association with ribosome-Sec61 complex and translocon inhibition by a CADA derivative. SCIENCE ADVANCES 2023; 9:eadf0797. [PMID: 36867692 PMCID: PMC9984176 DOI: 10.1126/sciadv.adf0797] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Accepted: 01/31/2023] [Indexed: 05/26/2023]
Abstract
During cotranslational translocation, the signal peptide of a nascent chain binds Sec61 translocon to initiate protein transport through the endoplasmic reticulum (ER) membrane. Our cryo-electron microscopy structure of ribosome-Sec61 shows binding of an ordered heterotetrameric translocon-associated protein (TRAP) complex, in which TRAP-γ is anchored at two adjacent positions of 28S ribosomal RNA and interacts with ribosomal protein L38 and Sec61α/γ. Four transmembrane helices (TMHs) of TRAP-γ cluster with one C-terminal helix of each α, β, and δ subunits. The seven TMH bundle helps position a crescent-shaped trimeric TRAP-α/β/δ core in the ER lumen, facing the Sec61 channel. Further, our in vitro assay establishes the cyclotriazadisulfonamide derivative CK147 as a translocon inhibitor. A structure of ribosome-Sec61-CK147 reveals CK147 binding the channel and interacting with the plug helix from the lumenal side. The CK147 resistance mutations surround the inhibitor. These structures help in understanding the TRAP functions and provide a new Sec61 site for designing translocon inhibitors.
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Affiliation(s)
- Eva Pauwels
- Department of Microbiology, Immunology, and Transplantation, KU Leuven, Leuven 3000, Belgium
- Laboratory of Virology and Chemotherapy, Rega Institute for Medical Research, KU Leuven, Leuven 3000, Belgium
| | - Neesha R. Shewakramani
- Department of Microbiology, Immunology, and Transplantation, KU Leuven, Leuven 3000, Belgium
- Laboratory of Virology and Chemotherapy, Rega Institute for Medical Research, KU Leuven, Leuven 3000, Belgium
| | - Brent De Wijngaert
- Department of Microbiology, Immunology, and Transplantation, KU Leuven, Leuven 3000, Belgium
- Laboratory of Virology and Chemotherapy, Rega Institute for Medical Research, KU Leuven, Leuven 3000, Belgium
| | - Anita Camps
- Department of Microbiology, Immunology, and Transplantation, KU Leuven, Leuven 3000, Belgium
- Laboratory of Virology and Chemotherapy, Rega Institute for Medical Research, KU Leuven, Leuven 3000, Belgium
| | - Becky Provinciael
- Department of Microbiology, Immunology, and Transplantation, KU Leuven, Leuven 3000, Belgium
- Laboratory of Virology and Chemotherapy, Rega Institute for Medical Research, KU Leuven, Leuven 3000, Belgium
| | - Joren Stroobants
- Department of Microbiology, Immunology, and Transplantation, KU Leuven, Leuven 3000, Belgium
- Laboratory of Virology and Chemotherapy, Rega Institute for Medical Research, KU Leuven, Leuven 3000, Belgium
| | - Kai-Uwe Kalies
- Centre for Structural and Cell Biology in Medicine, Institute of Biology, University of Lübeck, Lübeck 23562, Germany
| | - Enno Hartmann
- Centre for Structural and Cell Biology in Medicine, Institute of Biology, University of Lübeck, Lübeck 23562, Germany
| | - Piet Maes
- Department of Microbiology, Immunology, and Transplantation, KU Leuven, Leuven 3000, Belgium
- Laboratory of Clinical and Epidemiological Virology, Rega Institute for Medical Research, KU Leuven, Leuven 3000, Belgium
| | - Kurt Vermeire
- Department of Microbiology, Immunology, and Transplantation, KU Leuven, Leuven 3000, Belgium
- Laboratory of Virology and Chemotherapy, Rega Institute for Medical Research, KU Leuven, Leuven 3000, Belgium
| | - Kalyan Das
- Department of Microbiology, Immunology, and Transplantation, KU Leuven, Leuven 3000, Belgium
- Laboratory of Virology and Chemotherapy, Rega Institute for Medical Research, KU Leuven, Leuven 3000, Belgium
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Wang J, Gou X, Wang X, Zhang J, Zhao N, Wang X. Case Report: The novel hemizygous mutation in the SSR4 gene caused congenital disorder of glycosylation type iy: A case study and literature review. Front Genet 2022; 13:955732. [PMID: 36386804 PMCID: PMC9643473 DOI: 10.3389/fgene.2022.955732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Accepted: 10/10/2022] [Indexed: 12/05/2022] Open
Abstract
Background: Recently, the hemizygous variation of SSR4 gene has been reported to be associated with congenital disorder of glycosylation type Iy. To date, only 13 patients have been diagnosed with SSR4-CDG in the worldwide, but it has not been reported in the Chinese population. Methods: Whole-exome sequencing and gene copy number variation analysis were used to genetic analysis. The mRNA expression of SSR4 gene in blood was detected by Real-time Quantitative PCR. The clinical manifestations of all patients reported in the literature were reviewed. Results: WES analysis identified a de novo hemizygous variant c.269G>A (p.Trp90*) of SSR4 gene in the proband with psychomotor retardation, microcephaly, abnormal facial features, and nystagmus. This variant has not been reported in previous studies. The in vivo mRNA expression of SSR4 gene in patient was significantly decreased. Literature review showed that all 14 patients, including our patient, presented with hypotonia, intellectual disability, developmental delay, microcephaly, and abnormal facial features, while most patients had feeding difficulties, growth retardation, and ocular abnormalities, and epilepsy and skeletal abnormalities are less common. Conclusion: We reported the first case of SSR4-CDG caused by SSR4 variant in Chinese population, expanded the clinical and mutation spectra of the disorder, clarified the genetic etiology of the patient, and offered support for the prenatal diagnosis of the index family.
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7
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He W, Wang B, He J, Zhao Y, Zhao W. SSR4 as a prognostic biomarker and related with immune infiltration cells in colon adenocarcinoma. Expert Rev Mol Diagn 2021; 22:223-231. [PMID: 34904499 DOI: 10.1080/14737159.2022.2019015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
BACKGROUND Signal sequence receptor subunit delta (SSR4) gene is reported to encode the translocon-associated protein δ and related with the human immune regulation. However, the expression of SSR4 in colon adenocarcinoma (COAD) and its correlation with clinical treatment remains unclear. RESEARCH DESIGN AND METHODS SSR4 mRNA expression level and its relationship with tumor infiltrating lymphocytes (TILs) in COAD were evaluated through several databases. Furthermore, the study collected 238 cases of COAD tissue samples to detect the association of SSR4 protein expression level in TILs with clinical pathological information, and the prognosis of COAD. RESULTS SSR4 mRNA was significantly highly expressed in COAD tissues and significantly correlated with several types of TILs in COAD. Moreover, SSR4 highly expressed in many types of TILs, especially highly expressed in plasma cell from COAD patients with advanced TNM stage. High SSR4 protein expression in TILs was associated with lymph node metastasis, distant metastasis, American Joint Committee on Cancer (AJCC) staging, and Response Evaluation Criteria in Solid Tumors (RECIST) efficacy. COAD patients with high SSR4 expression in TILs had better overall survival. CONCLUSIONS In conclusion, high SSR4 mRNA and protein expression in TILs can be used as a prognostic biomarker for predicting better overall survival and treatment efficacy in COAD patients.
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Affiliation(s)
- Weiwei He
- Department of Oncology, Nanjing Hospital of Chinese Medicine Affiliated to Nanjing University of Chinese Medicine, Nanjing, China
| | - Bin Wang
- Department of Pathology, Nanjing First Hospital, Nanjing Medical University, Nanjing, China
| | - Jikai He
- Research Center for the Prevention and Treatment of Drug Resistant Microbial Infecting, Youjiang Medical University for Nationalities, Baise, China
| | - Youcai Zhao
- Department of Pathology, Nanjing First Hospital, Nanjing Medical University, Nanjing, China
| | - Wei Zhao
- Department of Pathology, Nanjing First Hospital, Nanjing Medical University, Nanjing, China.,Research Center for the Prevention and Treatment of Drug Resistant Microbial Infecting, Youjiang Medical University for Nationalities, Baise, China
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8
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Sicking M, Lang S, Bochen F, Roos A, Drenth JPH, Zakaria M, Zimmermann R, Linxweiler M. Complexity and Specificity of Sec61-Channelopathies: Human Diseases Affecting Gating of the Sec61 Complex. Cells 2021; 10:1036. [PMID: 33925740 PMCID: PMC8147068 DOI: 10.3390/cells10051036] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 04/15/2021] [Accepted: 04/17/2021] [Indexed: 12/14/2022] Open
Abstract
The rough endoplasmic reticulum (ER) of nucleated human cells has crucial functions in protein biogenesis, calcium (Ca2+) homeostasis, and signal transduction. Among the roughly one hundred components, which are involved in protein import and protein folding or assembly, two components stand out: The Sec61 complex and BiP. The Sec61 complex in the ER membrane represents the major entry point for precursor polypeptides into the membrane or lumen of the ER and provides a conduit for Ca2+ ions from the ER lumen to the cytosol. The second component, the Hsp70-type molecular chaperone immunoglobulin heavy chain binding protein, short BiP, plays central roles in protein folding and assembly (hence its name), protein import, cellular Ca2+ homeostasis, and various intracellular signal transduction pathways. For the purpose of this review, we focus on these two components, their relevant allosteric effectors and on the question of how their respective functional cycles are linked in order to reconcile the apparently contradictory features of the ER membrane, selective permeability for precursor polypeptides, and impermeability for Ca2+. The key issues are that the Sec61 complex exists in two conformations: An open and a closed state that are in a dynamic equilibrium with each other, and that BiP contributes to its gating in both directions in cooperation with different co-chaperones. While the open Sec61 complex forms an aqueous polypeptide-conducting- and transiently Ca2+-permeable channel, the closed complex is impermeable even to Ca2+. Therefore, we discuss the human hereditary and tumor diseases that are linked to Sec61 channel gating, termed Sec61-channelopathies, as disturbances of selective polypeptide-impermeability and/or aberrant Ca2+-permeability.
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Affiliation(s)
- Mark Sicking
- Department of Medical Biochemistry & Molecular Biology, Saarland University, D-66421 Homburg, Germany;
| | - Sven Lang
- Department of Medical Biochemistry & Molecular Biology, Saarland University, D-66421 Homburg, Germany;
| | - Florian Bochen
- Department of Otorhinolaryngology, Head and Neck Surgery, Saarland University Medical Center, D-66421 Homburg, Germany; (F.B.); (M.L.)
| | - Andreas Roos
- Department of Neuropediatrics, Essen University Hospital, D-45147 Essen, Germany;
| | - Joost P. H. Drenth
- Department of Molecular Gastroenterology and Hepatology, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands;
| | - Muhammad Zakaria
- Department of Genetics, Hazara University, Mansehra 21300, Pakistan;
| | - Richard Zimmermann
- Department of Medical Biochemistry & Molecular Biology, Saarland University, D-66421 Homburg, Germany;
| | - Maximilian Linxweiler
- Department of Otorhinolaryngology, Head and Neck Surgery, Saarland University Medical Center, D-66421 Homburg, Germany; (F.B.); (M.L.)
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9
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Phoomak C, Cui W, Hayman TJ, Yu SH, Zhao P, Wells L, Steet R, Contessa JN. The translocon-associated protein (TRAP) complex regulates quality control of N-linked glycosylation during ER stress. SCIENCE ADVANCES 2021; 7:eabc6364. [PMID: 33523898 PMCID: PMC7810369 DOI: 10.1126/sciadv.abc6364] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 11/24/2020] [Indexed: 05/04/2023]
Abstract
Asparagine (N)-linked glycosylation is required for endoplasmic reticulum (ER) homeostasis, but how this co- and posttranslational modification is maintained during ER stress is unknown. Here, we introduce a fluorescence-based strategy to detect aberrant N-glycosylation in individual cells and identify a regulatory role for the heterotetrameric translocon-associated protein (TRAP) complex. Unexpectedly, cells with knockout of SSR3 or SSR4 subunits restore N-glycosylation over time concurrent with a diminished ER stress transcriptional signature. Activation of ER stress or silencing of the ER chaperone BiP exacerbates or rescues the glycosylation defects, respectively, indicating that SSR3 and SSR4 enable N-glycosylation during ER stress. Protein levels of the SSR3 subunit are ER stress and UBE2J1 dependent, revealing a mechanism that coordinates upstream N-glycosylation proficiency with downstream ER-associated degradation and proteostasis. The fidelity of N-glycosylation is not static in both nontransformed and tumor cells, and the TRAP complex regulates ER glycoprotein quality control under conditions of stress.
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Affiliation(s)
- Chatchai Phoomak
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Wei Cui
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Thomas J Hayman
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Seok-Ho Yu
- Greenwood Genetic Center, Greenwood, SC 29646, USA
| | - Peng Zhao
- Complex Carbohydrate Research Center, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30601, USA
| | - Lance Wells
- Complex Carbohydrate Research Center, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30601, USA
| | | | - Joseph N Contessa
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06510, USA.
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06510, USA
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10
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Abstract
Folding of proteins is essential so that they can exert their functions. For proteins that transit the secretory pathway, folding occurs in the endoplasmic reticulum (ER) and various chaperone systems assist in acquiring their correct folding/subunit formation. N-glycosylation is one of the most conserved posttranslational modification for proteins, and in eukaryotes it occurs in the ER. Consequently, eukaryotic cells have developed various systems that utilize N-glycans to dictate and assist protein folding, or if they consistently fail to fold properly, to destroy proteins for quality control and the maintenance of homeostasis of proteins in the ER.
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11
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Castiglioni C, Feillet F, Barnerias C, Wiedemann A, Muchart J, Cortes F, Hernando-Davalillo C, Montero R, Dupré T, Bruneel A, Seta N, Vuillaumier-Barrot S, Serrano M. Expanding the phenotype of X-linked SSR4-CDG: Connective tissue implications. Hum Mutat 2020; 42:142-149. [PMID: 33300232 DOI: 10.1002/humu.24151] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 11/07/2020] [Accepted: 12/04/2020] [Indexed: 02/01/2023]
Abstract
Signal sequence receptor protein 4 (SSR4) is a subunit of the translocon-associated protein complex, which participates in the translocation of proteins across the endoplasmic reticulum membrane, enhancing the efficiency of N-linked glycosylation. Pathogenic variants in SSR4 cause a congenital disorder of glycosylation: SSR4-congenital disorders of glycosylation (CDG). We describe three SSR4-CDG boys and review the previously reported. All subjects presented with hypotonia, failure to thrive, developmental delay, and dysmorphic traits and showed a type 1 serum sialotransferrin profile, facilitating the diagnosis. Genetic confirmation of this X-linked CDG revealed one de novo hemizygous deletion, one maternally inherited deletion, and one de novo nonsense mutation of SSR4. The present subjects highlight the similarities with a connective tissue disorder (redundant skin, joint laxity, blue sclerae, and vascular tortuosity). The connective tissue problems are relevant, and require preventive rehabilitation measures. As an X-linked disorder, genetic counseling is essential.
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Affiliation(s)
- Claudia Castiglioni
- Department of Pediatric Neurology, Rare Disease Center, Clínica Las Condes, Santiago, Chile
| | - François Feillet
- Department of Pediatrics, Reference Center for Inborn Errors of Metabolism, University Hospital of Nancy, Nancy, France.,INSERM UMR_S 1256, Nutrition, Genetics, and Environmental Risk Exposure (NGERE), Faculty of Medicine of Nancy, University of Lorraine, Nancy, France
| | - Christine Barnerias
- Pediatric Neurology Department, Center de Référence Maladies Neuromusculaires (GNMH), Necker University Hospital, AP-HP, Paris, France
| | - Arnaud Wiedemann
- Department of Pediatrics, Reference Center for Inborn Errors of Metabolism, University Hospital of Nancy, Nancy, France.,INSERM UMR_S 1256, Nutrition, Genetics, and Environmental Risk Exposure (NGERE), Faculty of Medicine of Nancy, University of Lorraine, Nancy, France
| | - Jordi Muchart
- Department of Radiology, Hospital Sant Joan de Déu, Institut de Recerca Sant Joan de Déu, Barcelona, Spain
| | - Fanny Cortes
- Pediatric Department. Rare Diseases Center, Clínica Las Condes, Santiago, Chile
| | - Cristina Hernando-Davalillo
- Department of Genetic and Molecular Medicine and Pediatric Institute of Rare Diseases, Hospital Sant Joan de Déu, Barcelona, Spain
| | - Raquel Montero
- Clinical Biochemistry Department, Institut de Recerca Hospital Sant Joan de Déu Barcelona, Barcelona, Spain.,Unit-703 Center for Biomedical Research on Rare Diseases (CIBER-ER), Instituto de Salud Carlos III, Madrid, Spain
| | - Thierry Dupré
- Service de Biochimie Métabolique et Cellulaire, Hôpital Bichat-Claude Bernard, AP-HP, Paris, France.,INSERM UMR_S 1149, Faculté de Médecine Xavier Bichat, Université de Paris, Paris, France
| | - Arnaud Bruneel
- Service de Biochimie Métabolique et Cellulaire, Hôpital Bichat-Claude Bernard, AP-HP, Paris, France.,INSERM UMR1193, "Mécanismes cellulaires et moléculaires de l'adaptation au stress et cancérogenèse", Université Paris-Sud, Châtenay-Malabry, France
| | - Nathalie Seta
- Service de Biochimie Métabolique et Cellulaire, Hôpital Bichat-Claude Bernard, AP-HP, Paris, France
| | | | - Mercedes Serrano
- Unit-703 Center for Biomedical Research on Rare Diseases (CIBER-ER), Instituto de Salud Carlos III, Madrid, Spain.,Pediatric Neurology Department, Hospital Sant Joan de Déu, Institut de Recerca Sant Joan de Déu, Barcelona, Spain
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12
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Agopian AJ, Hoang TT, Goldmuntz E, Hakonarson H, Musfee FI, Mitchell LE. X-chromosome association studies of congenital heart defects. Am J Med Genet A 2020; 182:250-254. [PMID: 31729158 PMCID: PMC7539172 DOI: 10.1002/ajmg.a.61411] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 10/25/2019] [Accepted: 10/29/2019] [Indexed: 11/08/2022]
Affiliation(s)
- A. J. Agopian
- Human Genetics Center, Department of Epidemiology, Human Genetics, and Environmental Sciences, UTHealth School of Public Health, Houston, Texas
| | - Thanh T. Hoang
- Human Genetics Center, Department of Epidemiology, Human Genetics, and Environmental Sciences, UTHealth School of Public Health, Houston, Texas
| | - Elizabeth Goldmuntz
- Division of Cardiology, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
- Department of Pediatrics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
| | - Hakon Hakonarson
- Department of Pediatrics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
- Center for Applied Genomics, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Fadi I. Musfee
- Human Genetics Center, Department of Epidemiology, Human Genetics, and Environmental Sciences, UTHealth School of Public Health, Houston, Texas
| | - Laura E. Mitchell
- Human Genetics Center, Department of Epidemiology, Human Genetics, and Environmental Sciences, UTHealth School of Public Health, Houston, Texas
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13
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Ng BG, Lourenço CM, Losfeld ME, Buckingham KJ, Kircher M, Nickerson DA, Shendure J, Bamshad MJ, Freeze HH. Mutations in the translocon-associated protein complex subunit SSR3 cause a novel congenital disorder of glycosylation. J Inherit Metab Dis 2019; 42:993-997. [PMID: 30945312 PMCID: PMC6739144 DOI: 10.1002/jimd.12091] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Accepted: 03/25/2019] [Indexed: 12/16/2022]
Abstract
The translocon-associated protein (TRAP) complex facilitates the translocation of proteins across the endoplasmic reticulum membrane and associates with the oligosaccharyl transferase (OST) complex to maintain proper glycosylation of nascent polypeptides. Pathogenic variants in either complex cause a group of rare genetic disorders termed, congenital disorders of glycosylation (CDG). We report an individual who presented with severe intellectual and developmental disabilities and sensorineural deafness with an unsolved type I CDG, and sought to identify the underlying genetic basis. Exome sequencing identified a novel homozygous variant c.278_281delAGGA [p.Glu93Valfs*7] in the signal sequence receptor 3 (SSR3) subunit of the TRAP complex. Biochemical studies in patient fibroblasts showed the variant destabilized the TRAP complex with a complete loss of SSR3 protein and partial loss of SSR1 and SSR4. Importantly, all subunit levels were corrected by expression of wild-type SSR3. Abnormal glycosylation status in fibroblasts was confirmed using two markers proteins, GP130 and ICAM1. Our findings confirm mutations in SSR3 cause a novel CDG. A novel frameshift variant in the translocon associated protein, SSR3, disrupts the stability of the TRAP complex and causes a novel Congenital Disorder of Glycosylation.
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Affiliation(s)
- Bobby G. Ng
- Human Genetics Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA
| | - Charles Marques Lourenço
- Clinical Genetics and Neurogenetics, Centro Universitario Estacio de Ribeirao Preto, Ribeirao Preto, Brazil
| | - Marie-Estelle Losfeld
- Human Genetics Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA
| | - Kati J. Buckingham
- Department of Pediatrics, University of Washington, Seattle, WA 98195, USA
| | - Martin Kircher
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | | | - Jay Shendure
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
- Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195, USA
| | - Michael J. Bamshad
- Department of Pediatrics, University of Washington, Seattle, WA 98195, USA
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | | | - Hudson H. Freeze
- Human Genetics Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA
- Corresponding author: Hudson H. Freeze PhD, Sanford-Burnham-Prebys Medical Discovery Institute, 10901 N. Torrey Pines Rd. La Jolla, CA 92037, Phone: 858-646-3142;
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14
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Nguyen D, Stutz R, Schorr S, Lang S, Pfeffer S, Freeze HH, Förster F, Helms V, Dudek J, Zimmermann R. Proteomics reveals signal peptide features determining the client specificity in human TRAP-dependent ER protein import. Nat Commun 2018; 9:3765. [PMID: 30217974 PMCID: PMC6138672 DOI: 10.1038/s41467-018-06188-z] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 08/23/2018] [Indexed: 12/22/2022] Open
Abstract
In mammalian cells, one-third of all polypeptides are transported into or across the ER membrane via the Sec61 channel. While the Sec61 complex facilitates translocation of all polypeptides with amino-terminal signal peptides (SP) or transmembrane helices, the Sec61-auxiliary translocon-associated protein (TRAP) complex supports translocation of only a subset of precursors. To characterize determinants of TRAP substrate specificity, we here systematically identify TRAP-dependent precursors by analyzing cellular protein abundance changes upon TRAP depletion using quantitative label-free proteomics. The results are validated in independent experiments by western blotting, quantitative RT-PCR, and complementation analysis. The SPs of TRAP clients exhibit above-average glycine-plus-proline content and below-average hydrophobicity as distinguishing features. Thus, TRAP may act as SP receptor on the ER membrane’s cytosolic face, recognizing precursor polypeptides with SPs of high glycine-plus-proline content and/or low hydrophobicity, and triggering substrate-specific opening of the Sec61 channel through interactions with the ER-lumenal hinge of Sec61α. While Sec61 enables ER import of all polypeptides with N-terminal signal peptides, only selected clients are accepted for TRAP-assisted ER import. Here, the authors use a proteomics approach to characterize TRAP-dependent clients, identifying signal peptide features that govern recognition by TRAP.
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Affiliation(s)
- Duy Nguyen
- Center for Bioinformatics, Saarland University, 66041, Saarbrücken, Germany
| | - Regine Stutz
- Medical Biochemistry and Molecular Biology, Saarland University, 66421, Homburg, Germany
| | - Stefan Schorr
- Medical Biochemistry and Molecular Biology, Saarland University, 66421, Homburg, Germany
| | - Sven Lang
- Medical Biochemistry and Molecular Biology, Saarland University, 66421, Homburg, Germany
| | - Stefan Pfeffer
- Max-Planck Institute of Biochemistry, Department of Molecular Structural Biology, 82152, Martinsried, Germany
| | - Hudson H Freeze
- Sanford-Burnham-Prebys Medical Discovery Institute, La Jolla, CA, 92037, USA
| | - Friedrich Förster
- Bijvoet Center for Biomolecular Research, Utrecht University, 3584, CH, Utrecht, The Netherlands
| | - Volkhard Helms
- Center for Bioinformatics, Saarland University, 66041, Saarbrücken, Germany.
| | - Johanna Dudek
- Medical Biochemistry and Molecular Biology, Saarland University, 66421, Homburg, Germany.
| | - Richard Zimmermann
- Medical Biochemistry and Molecular Biology, Saarland University, 66421, Homburg, Germany.
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15
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Ng BG, Freeze HH. Perspectives on Glycosylation and Its Congenital Disorders. Trends Genet 2018; 34:466-476. [PMID: 29606283 DOI: 10.1016/j.tig.2018.03.002] [Citation(s) in RCA: 164] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 03/04/2018] [Accepted: 03/05/2018] [Indexed: 12/12/2022]
Abstract
Congenital disorders of glycosylation (CDG) are a rapidly expanding group of metabolic disorders that result from abnormal protein or lipid glycosylation. They are often difficult to clinically diagnose because they broadly affect many organs and functions and lack clinical uniformity. However, recent technological advances in next-generation sequencing have revealed a treasure trove of new genetic disorders, expanded the knowledge of known disorders, and showed a critical role in infectious diseases. More comprehensive genetic tools specifically tailored for mammalian cell-based models have revealed a critical role for glycosylation in pathogen-host interactions, while also identifying new CDG susceptibility genes. We highlight recent advancements that have resulted in a better understanding of human glycosylation disorders, perspectives for potential future therapies, and mysteries for which we continue to seek new insights and solutions.
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Affiliation(s)
- Bobby G Ng
- Human Genetics Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA
| | - Hudson H Freeze
- Human Genetics Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA.
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16
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Abstract
Congenital disorders of glycosylation (CDG) are one group among the disorders of glycosylation. The latter comprise defects associated with hypoglycosylation but also defects with hyperglycosylation. Genetic diseases with hypoglycosylation can be divided in primary congenital disorders of glycosylation (CDG) and in genetic diseases causing secondary hypoglycosylation. This review covers the human CDG highlights from the last 3 years (2014-2016) following a summary of the actual status of CDG. It expands on 23 novel CDG namely defects in SLC39A8, CAD, NANS, PGM3, SSR4, POGLUT1, NUS1, GANAB, PIGY, PIGW, PIGC, PIGG, PGAP1, PGAP3, VPS13B, CCDC115, TMEM199, ATP6AP1, ATP6V1A, ATP6V1E1, TRAPPC11, XYLT1 and XYLT2. Besides, it discusses novel phenotypes of known CDG (DHDDS-CDG, ALG9-CDG, EXT2-CDG, PIGA-CDG, PIGN-CDG), the elucidation of putative glycosyltransferase disorders as O-mannosylglycan synthesis disorders (TMEM5-CDG, ISPD-CDG, FKTN-CDG, FKRP-CDG), a novel CDG mechanism, advances in diagnosis, pathogenesis, treatment and finally an updated list of the 104 known CDG.
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Affiliation(s)
- Jaak Jaeken
- Center for Metabolic Diseases, University Hospital Gasthuisberg, KU Leuven, Herestraat 49, BE 3000, Leuven, Belgium.
| | - Romain Péanne
- Department of Human Genetics, University Hospital Gasthuisberg, KU Leuven, Leuven, Belgium
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17
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Pfeffer S, Dudek J, Schaffer M, Ng BG, Albert S, Plitzko JM, Baumeister W, Zimmermann R, Freeze HH, Engel BD, Förster F. Dissecting the molecular organization of the translocon-associated protein complex. Nat Commun 2017; 8:14516. [PMID: 28218252 PMCID: PMC5321747 DOI: 10.1038/ncomms14516] [Citation(s) in RCA: 101] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 01/05/2017] [Indexed: 12/26/2022] Open
Abstract
In eukaryotic cells, one-third of all proteins must be transported across or inserted into the endoplasmic reticulum (ER) membrane by the ER protein translocon. The translocon-associated protein (TRAP) complex is an integral component of the translocon, assisting the Sec61 protein-conducting channel by regulating signal sequence and transmembrane helix insertion in a substrate-dependent manner. Here we use cryo-electron tomography (CET) to study the structure of the native translocon in evolutionarily divergent organisms and disease-linked TRAP mutant fibroblasts from human patients. The structural differences detected by subtomogram analysis form a basis for dissecting the molecular organization of the TRAP complex. We assign positions to the four TRAP subunits within the complex, providing insights into their individual functions. The revealed molecular architecture of a central translocon component advances our understanding of membrane protein biogenesis and sheds light on the role of TRAP in human congenital disorders of glycosylation.
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Affiliation(s)
- Stefan Pfeffer
- Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Johanna Dudek
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Building 44, 66421 Homburg, Germany
| | - Miroslava Schaffer
- Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Bobby G Ng
- Human Genetics Program, Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Pines Road, La Jolla, California 92037, USA
| | - Sahradha Albert
- Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Jürgen M Plitzko
- Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Wolfgang Baumeister
- Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Richard Zimmermann
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Building 44, 66421 Homburg, Germany
| | - Hudson H Freeze
- Human Genetics Program, Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Pines Road, La Jolla, California 92037, USA
| | - Benjamin D Engel
- Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Friedrich Förster
- Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.,Cryo-Electron Microscopy, Bijvoet Center for Biomolecular Research, Department of Chemistry, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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18
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Pfeffer S, Dudek J, Zimmermann R, Förster F. Organization of the native ribosome-translocon complex at the mammalian endoplasmic reticulum membrane. Biochim Biophys Acta Gen Subj 2016; 1860:2122-9. [PMID: 27373685 DOI: 10.1016/j.bbagen.2016.06.024] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 06/24/2016] [Accepted: 06/28/2016] [Indexed: 11/17/2022]
Abstract
BACKGROUND In eukaryotic cells, many proteins have to be transported across or inserted into the endoplasmic reticulum membrane during their biogenesis on the ribosome. This process is facilitated by the protein translocon, a highly dynamic multi-subunit membrane protein complex. SCOPE OF REVIEW The aim of this review is to summarize the current structural knowledge about protein translocon components in mammals. MAJOR CONCLUSIONS Various structural biology approaches have been used in synergy to characterize the translocon in recent years. X-ray crystallography and cryoelectron microscopy single particle analysis have yielded highly detailed insights into the structure and functional mechanism of the protein-conducting channel Sec61, which constitutes the functional core of the translocon. Cryoelectron tomography and subtomogram analysis have advanced our understanding of the overall structure, molecular organization and compositional heterogeneity of the translocon in a native membrane environment. Tomography densities at subnanometer resolution revealed an intricate network of interactions between the ribosome, Sec61 and accessory translocon components that assist in protein transport, membrane insertion and maturation. GENERAL SIGNIFICANCE The protein translocon is a gateway for approximately one third of all synthesized proteins and numerous human diseases are associated with malfunctioning of its components. Thus, detailed insights into the structure and molecular organization of the translocon will not only advance our understanding of membrane protein biogenesis in general, but they can potentially pave the way for novel therapeutic approaches against human diseases.
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Affiliation(s)
- Stefan Pfeffer
- Max-Planck Institute of Biochemistry, Department of Molecular Structural Biology, D-82152 Martinsried, Germany
| | - Johanna Dudek
- Saarland University, Medical Biochemistry and Molecular Biology, D-66421 Homburg, Germany
| | - Richard Zimmermann
- Saarland University, Medical Biochemistry and Molecular Biology, D-66421 Homburg, Germany.
| | - Friedrich Förster
- Max-Planck Institute of Biochemistry, Department of Molecular Structural Biology, D-82152 Martinsried, Germany; Cryo-Electron Microscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
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19
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Cherepanova N, Shrimal S, Gilmore R. N-linked glycosylation and homeostasis of the endoplasmic reticulum. Curr Opin Cell Biol 2016; 41:57-65. [PMID: 27085638 DOI: 10.1016/j.ceb.2016.03.021] [Citation(s) in RCA: 166] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 03/24/2016] [Accepted: 03/30/2016] [Indexed: 01/17/2023]
Abstract
As a major site of protein biosynthesis, homeostasis of the endoplasmic reticulum is critical for cell viability. Asparagine linked glycosylation of newly synthesized proteins by the oligosaccharyltransferase plays a central role in ER homeostasis due to the use of protein-linked oligosaccharides as recognition and timing markers for glycoprotein quality control pathways that discriminate between correctly folded proteins and terminally malfolded proteins destined for ER associated degradation. Recent findings indicate how the oligosaccharyltransferase achieves efficient and accurate glycosylation of the diverse proteins that enter the endoplasmic reticulum. In metazoan organisms two distinct OST complexes cooperate to maximize the glycosylation of nascent proteins. The STT3B complex glycosylates acceptor sites that have been skipped by the translocation channel associated STT3A complex.
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Affiliation(s)
- Natalia Cherepanova
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, United States
| | - Shiteshu Shrimal
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, United States
| | - Reid Gilmore
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, United States.
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