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Sun W, Jin X, Zhu X. A novel SSR4 variant associated with congenital disorder of glycosylation: a case report and related analysis. Front Genet 2024; 15:1402883. [PMID: 39086474 PMCID: PMC11288868 DOI: 10.3389/fgene.2024.1402883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2024] [Accepted: 06/28/2024] [Indexed: 08/02/2024] Open
Abstract
Introduction Congenital disorders of glycosylation (CDG) refer to monogenetic diseases characterized by defective glycosylation of proteins or lipids causing multi-organ disorders. Here, we investigate the clinical features and genetic variants of SSR4-CDG and conduct a preliminary investigation of its pathogenesis. Methods We retrospectively report the clinical data of a male infant with early life respiratory distress, congenital diaphragmatic eventration, cosmetic deformities, and moderate growth retardation. Peripheral blood was collected from the case and parents, genomic DNA was extracted and whole-exome sequencing was performed. The mRNA expression of SSR4 gene was quantified by Real-time Quantitative PCR. RNA sequencing analysis was subsequently performed on the case and a healthy child. Results Whole-exome sequencing of the case and his parents' genomic DNA identified a hemizygous c.80_96del in SSR4, combined with the case's clinical features, the diagnosis of CDG was finally considered. In this case, the expression of SSR4 was downregulated. The case were present with 1,078 genes downregulated and 536 genes upregulated. SSR4 gene expression was significantly downregulated in the case. Meanwhile, gene set enrichment analysis (GSEA) revealed that SSR4-CDG may affect hemostasis, coagulation, catabolism, erythrocyte development and homeostatic regulation, and muscle contraction and regulation, etc. Improvement of growth retardation in case after high calorie formula feeding and rehabilitation training. Conclusion Our study expanded the SSR4-CDG variant spectrum and clinical phenotype and analyzed pathways potentially affected by SSR4-CDG, which may provide further insights into the function of SSR4 and help clinicians better understand this disorder.
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Affiliation(s)
| | | | - Xueping Zhu
- Department of Neonatology, Children’s Hospital of Soochow University, Suzhou, China
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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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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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Jaskolowski M, Jomaa A, Gamerdinger M, Shrestha S, Leibundgut M, Deuerling E, Ban N. Molecular basis of the TRAP complex function in ER protein biogenesis. Nat Struct Mol Biol 2023:10.1038/s41594-023-00990-0. [PMID: 37170030 DOI: 10.1038/s41594-023-00990-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 04/06/2023] [Indexed: 05/13/2023]
Abstract
The translocon-associated protein (TRAP) complex resides in the endoplasmic reticulum (ER) membrane and interacts with the Sec translocon and the ribosome to facilitate biogenesis of secretory and membrane proteins. TRAP plays a key role in the secretion of many hormones, including insulin. Here we reveal the molecular architecture of the mammalian TRAP complex and how it engages the translating ribosome associated with Sec61 translocon on the ER membrane. The TRAP complex is anchored to the ribosome via a long tether and its position is further stabilized by a finger-like loop. This positions a cradle-like lumenal domain of TRAP below the translocon for interactions with translocated nascent chains. Our structure-guided TRAP mutations in Caenorhabditis elegans lead to growth deficits associated with increased ER stress and defects in protein hormone secretion. These findings elucidate the molecular basis of the TRAP complex in the biogenesis and translocation of proteins at the ER.
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Affiliation(s)
- Mateusz Jaskolowski
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
| | - Ahmad Jomaa
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland.
- Department of Molecular Physiology and Biological Physics and the Center for Cell and Membrane Physiology, University of Virginia, Charlottesville, VA, USA.
| | - Martin Gamerdinger
- Department of Biology, Molecular Microbiology, University of Konstanz, Konstanz, Germany
| | - Sandeep Shrestha
- Department of Biology, Molecular Microbiology, University of Konstanz, Konstanz, Germany
| | - Marc Leibundgut
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
| | - Elke Deuerling
- Department of Biology, Molecular Microbiology, University of Konstanz, Konstanz, Germany.
| | - Nenad Ban
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland.
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5
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Wu Y, Yu Y, Sun Q, Yu Y, Chen J, Li T, Meng X, Pan G, Zhou Z. A Putative TRAPα Protein of Microsporidia Nosema bombycis Exhibits Non-Canonical Alternative Polyadenylation in Transcripts. J Fungi (Basel) 2023; 9:jof9040407. [PMID: 37108862 PMCID: PMC10142623 DOI: 10.3390/jof9040407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 03/22/2023] [Accepted: 03/23/2023] [Indexed: 03/29/2023] Open
Abstract
Microsporidia are obligate intracellular eukaryotic parasites that have significantly reduced genomes and that have lost most of their introns. In the current study, we characterized a gene in microsporidia Nosema bombycis, annotated as TRAPα (HNbTRAPα). The homologous of TRAPα are a functional component of ER translocon and facilitates the initiation of protein translocation in a substrate-specific manner, which is conserved in animals but absent from most fungi. The coding sequence of HNbTRAPα consists of 2226 nucleotides, longer than the majority of homologs in microsporidia. A 3′ RACE analysis indicated that there were two mRNA isoforms resulting from non-canonical alternative polyadenylation (APA), and the polyadenylate tail was synthesized after the C951 or C1167 nucleotide, respectively. Indirect immunofluorescence analysis showed two different localization characteristics of HNbTRAPα, which are mainly located around the nuclear throughout the proliferation stage and co-localized with the nuclear in mature spores. This study demonstrated that the post-transcriptional regulation mechanism exists in Microsporidia and expands the mRNA isoform repertoire.
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Affiliation(s)
- Yujiao Wu
- State Key Laboratory of Resource Insects, Southwest University, Beibei, Chongqing 400715, China
- Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Beibei, Chongqing 400715, China
- Key Laboratory of Sericultural Biology and Genetic Breeding, Ministry of Agriculture and Rural Affairs, Southwest University, Chongqing 400715, China
| | - Ying Yu
- State Key Laboratory of Resource Insects, Southwest University, Beibei, Chongqing 400715, China
- Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Beibei, Chongqing 400715, China
- Key Laboratory of Sericultural Biology and Genetic Breeding, Ministry of Agriculture and Rural Affairs, Southwest University, Chongqing 400715, China
| | - Quan Sun
- State Key Laboratory of Resource Insects, Southwest University, Beibei, Chongqing 400715, China
- Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Beibei, Chongqing 400715, China
- Key Laboratory of Sericultural Biology and Genetic Breeding, Ministry of Agriculture and Rural Affairs, Southwest University, Chongqing 400715, China
| | - Yixiang Yu
- State Key Laboratory of Resource Insects, Southwest University, Beibei, Chongqing 400715, China
- Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Beibei, Chongqing 400715, China
- Key Laboratory of Sericultural Biology and Genetic Breeding, Ministry of Agriculture and Rural Affairs, Southwest University, Chongqing 400715, China
| | - Jie Chen
- State Key Laboratory of Resource Insects, Southwest University, Beibei, Chongqing 400715, China
- Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Beibei, Chongqing 400715, China
- Key Laboratory of Sericultural Biology and Genetic Breeding, Ministry of Agriculture and Rural Affairs, Southwest University, Chongqing 400715, China
| | - Tian Li
- State Key Laboratory of Resource Insects, Southwest University, Beibei, Chongqing 400715, China
- Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Beibei, Chongqing 400715, China
- Key Laboratory of Sericultural Biology and Genetic Breeding, Ministry of Agriculture and Rural Affairs, Southwest University, Chongqing 400715, China
| | - Xianzhi Meng
- State Key Laboratory of Resource Insects, Southwest University, Beibei, Chongqing 400715, China
- Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Beibei, Chongqing 400715, China
- Key Laboratory of Sericultural Biology and Genetic Breeding, Ministry of Agriculture and Rural Affairs, Southwest University, Chongqing 400715, China
| | - Guoqing Pan
- State Key Laboratory of Resource Insects, Southwest University, Beibei, Chongqing 400715, China
- Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Beibei, Chongqing 400715, China
- Key Laboratory of Sericultural Biology and Genetic Breeding, Ministry of Agriculture and Rural Affairs, Southwest University, Chongqing 400715, China
- Correspondence: (G.P.); (Z.Z.)
| | - Zeyang Zhou
- State Key Laboratory of Resource Insects, Southwest University, Beibei, Chongqing 400715, China
- Chongqing Key Laboratory of Microsporidia Infection and Control, Southwest University, Beibei, Chongqing 400715, China
- Key Laboratory of Sericultural Biology and Genetic Breeding, Ministry of Agriculture and Rural Affairs, Southwest University, Chongqing 400715, China
- Key Laboratory of Conservation and Utilization of Pollinator Insect of the Upper Reaches of the Yangtze River (Co-Construction by Ministry and Province), Ministry of Agriculture and Rural Affairs, Chongqing Normal University, Chongqing 400047, China
- Correspondence: (G.P.); (Z.Z.)
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6
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Radford BN, Zhao X, Glazer T, Eaton M, Blackwell D, Mohammad S, Lo Vercio LD, Devine J, Shalom-Barak T, Hallgrimsson B, Cross JC, Sucov HM, Barak Y, Dean W, Hemberger M. Defects in placental syncytiotrophoblast cells are a common cause of developmental heart disease. Nat Commun 2023; 14:1174. [PMID: 36859534 PMCID: PMC9978031 DOI: 10.1038/s41467-023-36740-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Accepted: 02/15/2023] [Indexed: 03/03/2023] Open
Abstract
Placental abnormalities have been sporadically implicated as a source of developmental heart defects. Yet it remains unknown how often the placenta is at the root of congenital heart defects (CHDs), and what the cellular mechanisms are that underpin this connection. Here, we selected three mouse mutant lines, Atp11a, Smg9 and Ssr2, that presented with placental and heart defects in a recent phenotyping screen, resulting in embryonic lethality. To dissect phenotype causality, we generated embryo- and trophoblast-specific conditional knockouts for each of these lines. This was facilitated by the establishment of a new transgenic mouse, Sox2-Flp, that enables the efficient generation of trophoblast-specific conditional knockouts. We demonstrate a strictly trophoblast-driven cause of the CHD and embryonic lethality in one of the three lines (Atp11a) and a significant contribution of the placenta to the embryonic phenotypes in another line (Smg9). Importantly, our data reveal defects in the maternal blood-facing syncytiotrophoblast layer as a shared pathology in placentally induced CHD models. This study highlights the placenta as a significant source of developmental heart disorders, insights that will transform our understanding of the vast number of unexplained congenital heart defects.
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Affiliation(s)
- Bethany N Radford
- Dept. of Biochemistry and Molecular Biology, Cumming School of Medicine, Alberta Children's Hospital Research Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada
| | - Xiang Zhao
- Dept. of Cell Biology and Anatomy, Cumming School of Medicine, Alberta Children's Hospital Research Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada
| | - Tali Glazer
- Dept. of Biochemistry and Molecular Biology, Cumming School of Medicine, Alberta Children's Hospital Research Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada
| | - Malcolm Eaton
- Dept. of Biochemistry and Molecular Biology, Cumming School of Medicine, Alberta Children's Hospital Research Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada
| | - Danielle Blackwell
- Dept. of Biochemistry and Molecular Biology, Cumming School of Medicine, Alberta Children's Hospital Research Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada
| | - Shuhiba Mohammad
- Dept. of Biochemistry and Molecular Biology, Cumming School of Medicine, Alberta Children's Hospital Research Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada
| | - Lucas Daniel Lo Vercio
- Dept. of Cell Biology and Anatomy, Cumming School of Medicine, Alberta Children's Hospital Research Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada
| | - Jay Devine
- Dept. of Cell Biology and Anatomy, Cumming School of Medicine, Alberta Children's Hospital Research Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada
| | - Tali Shalom-Barak
- Magee-Women's Research Institute, Dept. of Obstetrics/Gynecology and Reproductive Sciences, University of Pittsburgh, 204 Craft Ave., Pittsburgh, PA, 15213, USA
| | - Benedikt Hallgrimsson
- Dept. of Cell Biology and Anatomy, Cumming School of Medicine, Alberta Children's Hospital Research Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada
| | - James C Cross
- Dept. of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, Alberta Children's Hospital Research Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada
| | - Henry M Sucov
- Dept. of Regenerative Medicine and Cell Biology, Division of Cardiology, Dept. of Medicine, Medical University of South Carolina, 173 Ashley Ave., Charleston, SC, 29403, USA
| | - Yaacov Barak
- Magee-Women's Research Institute, Dept. of Obstetrics/Gynecology and Reproductive Sciences, University of Pittsburgh, 204 Craft Ave., Pittsburgh, PA, 15213, USA
| | - Wendy Dean
- Dept. of Cell Biology and Anatomy, Cumming School of Medicine, Alberta Children's Hospital Research Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada.
| | - Myriam Hemberger
- Dept. of Biochemistry and Molecular Biology, Cumming School of Medicine, Alberta Children's Hospital Research Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada.
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Itskanov S, Park E. Mechanism of Protein Translocation by the Sec61 Translocon Complex. Cold Spring Harb Perspect Biol 2023; 15:a041250. [PMID: 35940906 PMCID: PMC9808579 DOI: 10.1101/cshperspect.a041250] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The endoplasmic reticulum (ER) is a major site for protein synthesis, folding, and maturation in eukaryotic cells, responsible for production of secretory proteins and most integral membrane proteins. The universally conserved protein-conducting channel Sec61 complex mediates core steps in these processes by translocating hydrophilic polypeptide segments of client proteins across the ER membrane and integrating hydrophobic transmembrane segments into the membrane. The Sec61 complex associates with several other molecular machines and enzymes to enable substrate engagement with the channel and coordination of protein translocation with translation, protein folding, and/or post-translational modifications. Recent cryo-electron microscopy and functional studies of these translocon complexes have greatly advanced our mechanistic understanding of Sec61-dependent protein biogenesis at the ER. Here, we will review the current models for how the Sec61 channel performs its functions in coordination with partner complexes.
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Affiliation(s)
- Samuel Itskanov
- Biophysics Graduate Program
- California Institute for Quantitative Biosciences
| | - Eunyong Park
- California Institute for Quantitative Biosciences
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California 94720, USA
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8
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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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9
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Dmello C, Sonabend A, Arrieta VA, Zhang DY, Kanojia D, Chen L, Gould A, Zhang J, Kang SJ, Winter J, Horbinski C, Amidei C, Győrffy B, Cordero A, Lee-Chang C, Castro B, Hsu P, Ahmed AU, Lesniak MS, Stupp R, Sonabend AM. Translocon-associated protein subunit SSR3 determines and predicts susceptibility to paclitaxel in breast cancer and glioblastoma. Clin Cancer Res 2022; 28:3156-3169. [PMID: 35552677 DOI: 10.1158/1078-0432.ccr-21-2563] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 12/13/2021] [Accepted: 05/09/2022] [Indexed: 11/16/2022]
Abstract
PURPOSE Paclitaxel (PTX) is one the most potent and commonly used chemotherapies for breast and pancreatic cancer. Several ongoing clinical trials are investigating means of enhancing delivery of PTX across the blood-brain barrier for glioblastomas (GBMs). Despite the widespread use of PTX for breast cancer, and the initiative to repurpose this drug for gliomas, there are no predictive biomarkers to inform which patients will likely benefit from this therapy. EXPERIMENTAL DESIGN To identify predictive biomarkers for susceptibility to PTX, we performed a genome-wide CRISPR knock-out (KO) screen using human glioma cells. The genes whose KO was most enriched in the CRISPR screen underwent further selection based on their correlation with survival in the breast cancer patient cohorts treated with PTX and not in patients treated with other chemotherapies, a finding that was validated on a second independent patient cohort using progression-free survival. RESULTS Combination of CRISPR screen results with outcomes from taxane-treated breast cancer patients led to the discovery of endoplasmic reticulum (ER) protein SSR3 as a putative predictive biomarker for PTX. SSR3 protein levels showed positive correlation with susceptibility to PTX in breast cancer cells, glioma cells and in multiple intracranial glioma xenografts models. Knockout of SSR3 turned the cells resistant to PTX while its overexpression sensitized the cells to PTX. Mechanistically, SSR3 confers susceptibility to PTX through regulation of phosphorylation of ER stress sensor IRE1α. CONCLUSION Our hypothesis generating study showed SSR3 as a putative biomarker for susceptibility to PTX, warranting its prospective clinical validation.
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Affiliation(s)
| | - Aarón Sonabend
- Harvard T. H. Chan School of Public Health, Boston, United States
| | | | | | | | - Li Chen
- Northwestern University, Chicago, United States
| | - Andrew Gould
- Northwestern University, Chicago, Illinois, United States
| | - Jiangshan Zhang
- Harvard T. H. Chan School of Public Health, Boston, United States
| | | | - Jan Winter
- German Cancer Research Center, Heidelberg, Germany
| | - Craig Horbinski
- Northwestern University, Feinberg School of Medicine, Chicago, IL, United States
| | | | | | | | - Catalina Lee-Chang
- Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | | | - Patrick Hsu
- Innovative Genomics Institute, University of California, Berkeley, United States
| | | | - Maciej S Lesniak
- Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States
| | - Roger Stupp
- Northwestern University, Feinberg School of Medicine, Chicago, IL, United States
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10
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Zábranská H, Zábranský A, Lubyová B, Hodek J, Křenková A, Hubálek M, Weber J, Pichová I. Biogenesis of hepatitis B virus e antigen is driven by translocon-associated protein complex and regulated by conserved cysteine residues within its signal peptide sequence. FEBS J 2021; 289:2895-2914. [PMID: 34839586 PMCID: PMC9300162 DOI: 10.1111/febs.16304] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 10/27/2021] [Accepted: 11/26/2021] [Indexed: 11/28/2022]
Abstract
Hepatitis B virus uses e antigen (HBe), which is dispensable for virus infectivity, to modulate host immune responses and achieve viral persistence in human hepatocytes. The HBe precursor (p25) is directed to the endoplasmic reticulum (ER), where cleavage of the signal peptide (sp) gives rise to the first processing product, p22. P22 can be retro-translocated back to the cytosol or enter the secretory pathway and undergo a second cleavage event, resulting in secreted p17 (HBe). Here, we report that translocation of p25 to the ER is promoted by translocon-associated protein complex. We have found that p25 is not completely translocated into the ER; a fraction of p25 is phosphorylated and remains in the cytoplasm and nucleus. Within the p25 sp sequence, we have identified three cysteine residues that control the efficiency of sp cleavage and contribute to proper subcellular distribution of the precore pool.
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Affiliation(s)
- Helena Zábranská
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czech Republic
| | - Aleš Zábranský
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czech Republic
| | - Barbora Lubyová
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czech Republic
| | - Jan Hodek
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czech Republic
| | - Alena Křenková
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czech Republic
| | - Martin Hubálek
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czech Republic
| | - Jan Weber
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czech Republic
| | - Iva Pichová
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czech Republic
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11
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Sicking M, Jung M, Lang S. Lights, Camera, Interaction: Studying Protein-Protein Interactions of the ER Protein Translocase in Living Cells. Int J Mol Sci 2021; 22:10358. [PMID: 34638699 PMCID: PMC8508666 DOI: 10.3390/ijms221910358] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 09/18/2021] [Accepted: 09/22/2021] [Indexed: 12/12/2022] Open
Abstract
Various landmark studies have revealed structures and functions of the Sec61/SecY complex in all domains of live demonstrating the conserved nature of this ancestral protein translocase. While the bacterial homolog of the Sec61 complex resides in the plasma membrane, the eukaryotic counterpart manages the transfer of precursor proteins into or across the membrane of the endoplasmic reticulum (ER). Sec61 complexes are accompanied by a set of dynamically recruited auxiliary proteins assisting the transport of certain precursor polypeptides. TRAP and Sec62/Sec63 are two auxiliary protein complexes in mammalian cells that have been characterized by structural and biochemical methods. Using these ER membrane protein complexes for our proof-of-concept study, we aimed to detect interactions of membrane proteins in living mammalian cells under physiological conditions. Bimolecular luminescence complementation and competition was used to demonstrate multiple protein-protein interactions of different topological layouts. In addition to the interaction of the soluble catalytic and regulatory subunits of the cytosolic protein kinase A, we detected interactions of ER membrane proteins that either belong to the same multimeric protein complex (intra-complex interactions: Sec61α-Sec61β, TRAPα-TRAPβ) or protein complexes in juxtaposition (inter-complex interactions: Sec61α-TRAPα, Sec61α-Sec63, and Sec61β-Sec63). In the process, we established further control elements like synthetic peptide complementation for expression profiling of fusion constructs and protease-mediated reporter degradation demonstrating the cytosolic localization of a reporter complementation. Ease of use and flexibility of the approach presented here will spur further research regarding the dynamics of protein-protein interactions in response to changing cellular conditions in living cells.
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Affiliation(s)
| | | | - Sven Lang
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (M.S.); (M.J.)
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12
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Huang Y, Xu X, Arvan P, Liu M. Deficient endoplasmic reticulum translocon-associated protein complex limits the biosynthesis of proinsulin and insulin. FASEB J 2021; 35:e21515. [PMID: 33811688 DOI: 10.1096/fj.202002774r] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 02/14/2021] [Accepted: 02/24/2021] [Indexed: 01/22/2023]
Abstract
The conserved endoplasmic reticulum (ER) membrane protein TRAPα (translocon-associated protein, also known as signal sequence receptor 1, SSR1) has been reported to play a critical but unclear role in insulin biosynthesis. TRAPα/SSR1 is one component of a four-protein complex including TRAPβ/SSR2, TRAPγ/SSR3, and TRAPδ/SSR4. The TRAP complex topologically has a small exposure on the cytosolic side of the ER via its TRAPγ/SSR3 subunit, whereas TRAPβ/SSR2 and TRAPδ/SSR4 function along with TRAPα/SSR1 largely on the luminal side of the ER membrane. Here, we have examined pancreatic β-cells with deficient expression of either TRAPβ/SSR2 or TRAPδ/SSR4, which does not perturb mRNA expression levels of other TRAP subunits, or insulin mRNA. However, deficient protein expression of TRAPβ/SSR2 and, to a lesser degree, TRAPδ/SSR4, diminishes the protein levels of other TRAP subunits, concomitant with deficient steady-state levels of proinsulin and insulin. Deficient TRAPβ/SSR2 or TRAPδ/SSR4 is not associated with any apparent defect of exocytotic mechanism but rather by a decreased abundance of the proinsulin and insulin that accompanies glucose-stimulated secretion. Amino acid pulse labeling directly establishes that much of the steady-state deficiency of intracellular proinsulin can be accounted for by diminished proinsulin biosynthesis, observed in a pulse-labeling as short as 5 minutes. The proinsulin and insulin levels in TRAPβ/SSR2 or TRAPδ/SSR4 null mutant β-cells are notably recovered upon re-expression of the missing TRAP subunit, accompanying a rebound of proinsulin biosynthesis. Remarkably, overexpression of TRAPα/SSR1 can also suppress defects in β-cells with diminished expression of TRAPβ/SSR2, strongly suggesting that TRAPβ/SSR2 is needed to support TRAPα/SSR1 function.
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Affiliation(s)
- Yumeng Huang
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China.,Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical Center, Ann Arbor, MI, USA
| | - Xiaoxi Xu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China.,Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical Center, Ann Arbor, MI, USA
| | - Peter Arvan
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical Center, Ann Arbor, MI, USA
| | - Ming Liu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China.,Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical Center, Ann Arbor, MI, USA
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13
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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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14
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Kriegler T, Kiburg G, Hessa T. Translocon-Associated Protein Complex (TRAP) is Crucial for Co-Translational Translocation of Pre-Proinsulin. J Mol Biol 2020; 432:166694. [PMID: 33137310 DOI: 10.1016/j.jmb.2020.10.028] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 10/11/2020] [Accepted: 10/22/2020] [Indexed: 01/23/2023]
Abstract
Many unanswered questions remain in understanding the biosynthesis of the peptide hormone insulin. Here we elucidate new aspects in the mechanism of co-translational translocation initiation of pre-proinsulin in the endoplasmic reticulum. We utilize a translational arrest peptide derived from the x-box-binding protein (Xbp1) to induce ribosomal stalling and generate translocation intermediates. We find that the insulin signal sequence is rather weakly gating and requires the assistance of auxiliary translocon components to initiate translocation. Probing the translational intermediates with chemical crosslinking, we identified an early interaction with the translocon-associated protein (TRAP) complex. The TRAPβ subunit interacts with pre-proinsulin before the peptide enters the Sec61 translocon channel in a signal sequence-dependent manner. We describe the substrate sequence determinants that are recognized by TRAP on the cytosolic site of the membrane to facilitate substrate-specific opening of the Sec61 translocon channel. Our findings support the hypothesis that the TRAP-dependence is in part determined by the content of glycine and proline residues mainly within the signal sequence.
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Affiliation(s)
- T Kriegler
- Department of Biochemistry and Biophysics, Arrhenius Laboratories of Natural Sciences, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden
| | - G Kiburg
- Department of Biochemistry and Biophysics, Arrhenius Laboratories of Natural Sciences, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden
| | - T Hessa
- Department of Biochemistry and Biophysics, Arrhenius Laboratories of Natural Sciences, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden.
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15
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Wang YH, Ding ZY, Cheng YJ, Chien CT, Huang ML. An Efficient Screen for Cell-Intrinsic Factors Identifies the Chaperonin CCT and Multiple Conserved Mechanisms as Mediating Dendrite Morphogenesis. Front Cell Neurosci 2020; 14:577315. [PMID: 33100975 PMCID: PMC7546278 DOI: 10.3389/fncel.2020.577315] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 09/02/2020] [Indexed: 12/25/2022] Open
Abstract
Dendritic morphology is inextricably linked to neuronal function. Systematic large-scale screens combined with genetic mapping have uncovered several mechanisms underlying dendrite morphogenesis. However, a comprehensive overview of participating molecular mechanisms is still lacking. Here, we conducted an efficient clonal screen using a collection of mapped P-element insertions that were previously shown to cause lethality and eye defects in Drosophila melanogaster. Of 280 mutants, 52 exhibited dendritic defects. Further database analyses, complementation tests, and RNA interference validations verified 40 P-element insertion genes as being responsible for the dendritic defects. Twenty-eight mutants presented severe arbor reduction, and the remainder displayed other abnormalities. The intrinsic regulators encoded by the identified genes participate in multiple conserved mechanisms and pathways, including the protein folding machinery and the chaperonin-containing TCP-1 (CCT) complex that facilitates tubulin folding. Mutant neurons in which expression of CCT4 or CCT5 was depleted exhibited severely retarded dendrite growth. We show that CCT localizes in dendrites and is required for dendritic microtubule organization and tubulin stability, suggesting that CCT-mediated tubulin folding occurs locally within dendrites. Our study also reveals novel mechanisms underlying dendrite morphogenesis. For example, we show that Drosophila Nogo signaling is required for dendrite development and that Mummy and Wech also regulate dendrite morphogenesis, potentially via Dpp- and integrin-independent pathways. Our methodology represents an efficient strategy for identifying intrinsic dendrite regulators, and provides insights into the plethora of molecular mechanisms underlying dendrite morphogenesis.
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Affiliation(s)
- Ying-Hsuan Wang
- Department of Biomedical Sciences, National Chung Cheng University, Chiayi, Taiwan.,Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Zhao-Ying Ding
- Department of Biomedical Sciences, National Chung Cheng University, Chiayi, Taiwan
| | - Ying-Ju Cheng
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | | | - Min-Lang Huang
- Department of Biomedical Sciences, National Chung Cheng University, Chiayi, Taiwan
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16
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Kriegler T, Lang S, Notari L, Hessa T. Prion Protein Translocation Mechanism Revealed by Pulling Force Studies. J Mol Biol 2020; 432:4447-4465. [PMID: 32502491 DOI: 10.1016/j.jmb.2020.05.022] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 05/10/2020] [Accepted: 05/28/2020] [Indexed: 11/26/2022]
Abstract
The mammalian prion protein (PrP) engages with the ribosome-Sec61 translocation channel complex to generate different topological variants that are either physiological, or involved in neurodegenerative diseases. Here, we describe cotranslational folding and translocation mechanisms of PrP coupled to an Xbp1-based arrest peptide as folding sensor, to measure forces acting on PrP nascent chain. Our data reveal two main pulling events followed by a minor third one exerted on the nascent chains during their translocation. Using those force landscapes, we show that a specific sequence within an intrinsically disordered region, containing a polybasic and glycine-proline rich residues, modulates the second pulling event by interacting with TRAP complex. This work also delineates the sequence of events involved in generation of PrP toxic transmembrane topologies during its synthesis. Our results shed new insight into the folding of such a topological complex protein, where marginal pulling by the signal sequence, together with the flanking downstream sequence in the mature domain, primarily drives an overall inefficient translocation resulting in the nascent chain to adopt alternative topologies.
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Affiliation(s)
- Theresa Kriegler
- Department of Biochemistry and Biophysics, Arrhenius Laboratories of Natural Sciences, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden
| | - Sven Lang
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Luigi Notari
- Department of Clinical Neuroscience, Therapeutic Immune Design Unit, CMM, L8:02, Karolinska Institutet, Sweden
| | - Tara Hessa
- Department of Biochemistry and Biophysics, Arrhenius Laboratories of Natural Sciences, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden.
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17
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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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18
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Dittner-Moormann S, Lourenco CM, Reunert J, Nishinakamura R, Tanaka SS, Werner C, Debus V, Zimmer KP, Wetzel G, Naim HY, Wada Y, Rust S, Marquardt T. TRAPγ-CDG shows asymmetric glycosylation and an effect on processing of proteins required in higher organisms. J Med Genet 2020; 58:213-216. [PMID: 32332102 DOI: 10.1136/jmedgenet-2019-106279] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 03/19/2020] [Accepted: 03/21/2020] [Indexed: 12/30/2022]
Abstract
Newly synthesised glycoproteins enter the rough endoplasmic reticulum through a translocation pore. The translocon associated protein (TRAP) complex is located close to the pore. In a patient with a homozygous start codon variant in TRAPγ (SSR3), absence of TRAPγ causes disruption of the TRAP complex, impairs protein translocation into the endoplasmic reticulum and affects transport, for example, into the brush-border membrane. Furthermore, we observed an unbalanced non-occupancy of N-glycosylation sites. The major clinical features are intrauterine growth retardation, facial dysmorphism, congenital diarrhoea, failure to thrive, pulmonary disease and severe psychomotor disability.
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Affiliation(s)
| | - Charles Marques Lourenco
- Department of Medical Genetics, School of Medicine, Neurogenetics Unit, University, Sao Paulo, Sao Paulo, Brazil
| | - Janine Reunert
- Department of Pediatrics, Universitätsklinikum Münster, Münster, Germany
| | - Ryuichi Nishinakamura
- Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto, Kumamoto, Japan
| | - Satomi S Tanaka
- Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto, Kumamoto, Japan
| | - Claudius Werner
- Department of Pediatrics, Universitätsklinikum Münster, Münster, Germany
| | - Volker Debus
- Department of Pediatrics, Universitätsklinikum Münster, Münster, Germany
| | - Klaus-Peter Zimmer
- Department of Pediatrics, Universitätsklinikum Gießen und Marburg Standort Gießen, Giessen, Hessen, Germany
| | - Gabriele Wetzel
- Department of Physiological Chemistry, University of Veterinary Medicine, Hannover, Germany, Hannover, Germany
| | - Hassan Y Naim
- Department of Physiological Chemistry, University of Veterinary Medicine, Hannover, Germany, Hannover, Germany
| | - Yoshinao Wada
- Osaka Medical Center and Research Institute for Maternal and Child Health, Izumi, Osaka, Japan
| | - Stephan Rust
- Department of Pediatrics, Universitätsklinikum Münster, Münster, Germany
| | - Thorsten Marquardt
- Department of Pediatrics, Universitätsklinikum Münster, Münster, Germany
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19
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Abstract
The endoplasmic reticulum (ER) translocon complex is the main gate into the secretory pathway, facilitating the translocation of nascent peptides into the ER lumen or their integration into the lipid membrane. Protein biogenesis in the ER involves additional processes, many of them occurring co-translationally while the nascent protein resides at the translocon complex, including recruitment of ER-targeted ribosome-nascent-chain complexes, glycosylation, signal peptide cleavage, membrane protein topogenesis and folding. To perform such varied functions on a broad range of substrates, the ER translocon complex has different accessory components that associate with it either stably or transiently. Here, we review recent structural and functional insights into this dynamically constituted central hub in the ER and its components. Recent cryo-electron microscopy (EM) studies have dissected the molecular organization of the co-translational ER translocon complex, comprising the Sec61 protein-conducting channel, the translocon-associated protein complex and the oligosaccharyl transferase complex. Complemented by structural characterization of the post-translational import machinery, key molecular principles emerge that distinguish co- and post-translational protein import and biogenesis. Further cryo-EM structures promise to expand our mechanistic understanding of the various biochemical functions involving protein biogenesis and quality control in the ER.
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Affiliation(s)
- Max Gemmer
- Cryo-Electron Microscopy, Bijvoet Center for Biomolecular Research, Utrecht University, 3584 CH Utrecht, The Netherlands
| | - Friedrich Förster
- Cryo-Electron Microscopy, Bijvoet Center for Biomolecular Research, Utrecht University, 3584 CH Utrecht, The Netherlands
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20
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Li X, Itani OA, Haataja L, Dumas KJ, Yang J, Cha J, Flibotte S, Shih HJ, Delaney CE, Xu J, Qi L, Arvan P, Liu M, Hu PJ. Requirement for translocon-associated protein (TRAP) α in insulin biogenesis. SCIENCE ADVANCES 2019; 5:eaax0292. [PMID: 31840061 PMCID: PMC6892615 DOI: 10.1126/sciadv.aax0292] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 10/07/2019] [Indexed: 05/26/2023]
Abstract
The mechanistic basis for the biogenesis of peptide hormones and growth factors is poorly understood. Here, we show that the conserved endoplasmic reticulum membrane translocon-associated protein α (TRAPα), also known as signal sequence receptor 1, plays a critical role in the biosynthesis of insulin. Genetic analysis in the nematode Caenorhabditis elegans and biochemical studies in pancreatic β cells reveal that TRAPα deletion impairs preproinsulin translocation while unexpectedly disrupting distal steps in insulin biogenesis including proinsulin processing and secretion. The association of common intronic single-nucleotide variants in the human TRAPα gene with susceptibility to type 2 diabetes and pancreatic β cell dysfunction suggests that impairment of preproinsulin translocation and proinsulin trafficking may contribute to the pathogenesis of type 2 diabetes.
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Affiliation(s)
- Xin Li
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Omar A. Itani
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Leena Haataja
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Kathleen J. Dumas
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Jing Yang
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Jeeyeon Cha
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
- Division of Diabetes, Endocrinology and Metabolism, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Stephane Flibotte
- Departments of Zoology and Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Hung-Jen Shih
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Colin E. Delaney
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Jialu Xu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
| | - Ling Qi
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Peter Arvan
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Ming Liu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
- Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Patrick J. Hu
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN, USA
- Division of Hematology and Oncology, Vanderbilt University Medical Center, Nashville, TN, USA
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21
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Marinko J, Huang H, Penn WD, Capra JA, Schlebach JP, Sanders CR. Folding and Misfolding of Human Membrane Proteins in Health and Disease: From Single Molecules to Cellular Proteostasis. Chem Rev 2019; 119:5537-5606. [PMID: 30608666 PMCID: PMC6506414 DOI: 10.1021/acs.chemrev.8b00532] [Citation(s) in RCA: 153] [Impact Index Per Article: 30.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2018] [Indexed: 12/13/2022]
Abstract
Advances over the past 25 years have revealed much about how the structural properties of membranes and associated proteins are linked to the thermodynamics and kinetics of membrane protein (MP) folding. At the same time biochemical progress has outlined how cellular proteostasis networks mediate MP folding and manage misfolding in the cell. When combined with results from genomic sequencing, these studies have established paradigms for how MP folding and misfolding are linked to the molecular etiologies of a variety of diseases. This emerging framework has paved the way for the development of a new class of small molecule "pharmacological chaperones" that bind to and stabilize misfolded MP variants, some of which are now in clinical use. In this review, we comprehensively outline current perspectives on the folding and misfolding of integral MPs as well as the mechanisms of cellular MP quality control. Based on these perspectives, we highlight new opportunities for innovations that bridge our molecular understanding of the energetics of MP folding with the nuanced complexity of biological systems. Given the many linkages between MP misfolding and human disease, we also examine some of the exciting opportunities to leverage these advances to address emerging challenges in the development of therapeutics and precision medicine.
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Affiliation(s)
- Justin
T. Marinko
- Department
of Biochemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
- Center
for Structural Biology, Vanderbilt University, Nashville, Tennessee 37240, United States
| | - Hui Huang
- Department
of Biochemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
- Center
for Structural Biology, Vanderbilt University, Nashville, Tennessee 37240, United States
| | - Wesley D. Penn
- Department
of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - John A. Capra
- Center
for Structural Biology, Vanderbilt University, Nashville, Tennessee 37240, United States
- Department
of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37245, United States
| | - Jonathan P. Schlebach
- Department
of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Charles R. Sanders
- Department
of Biochemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
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22
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Lang S, Nguyen D, Pfeffer S, Förster F, Helms V, Zimmermann R. Functions and Mechanisms of the Human Ribosome-Translocon Complex. Subcell Biochem 2019; 93:83-141. [PMID: 31939150 DOI: 10.1007/978-3-030-28151-9_4] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The membrane of the endoplasmic reticulum (ER) in human cells harbors the protein translocon, which facilitates membrane insertion and translocation of almost every newly synthesized polypeptide targeted to organelles of the secretory pathway. The translocon comprises the polypeptide-conducting Sec61 channel and several additional proteins, which are associated with the heterotrimeric Sec61 complex. This ensemble of proteins facilitates ER targeting of precursor polypeptides, Sec61 channel opening and closing, and modification of precursor polypeptides in transit through the Sec61 complex. Recently, cryoelectron tomography of translocons in native ER membranes has given unprecedented insights into the architecture and dynamics of the native, ribosome-associated translocon and the Sec61 channel. These structural data are discussed in light of different Sec61 channel activities including ribosome receptor function, membrane insertion or translocation of newly synthesized polypeptides as well as the possible roles of the Sec61 channel as a passive ER calcium leak channel and regulator of ATP/ADP exchange between cytosol and ER.
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Affiliation(s)
- Sven Lang
- Competence Center for Molecular Medicine, Saarland University Medical School, Building 44, 66421, Homburg, Germany.
| | - Duy Nguyen
- Center for Bioinformatics, Saarland University, 66041, Saarbrücken, Germany
| | - Stefan Pfeffer
- Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152, Martinsried, Germany
- ZMBH, 69120, Heidelberg, Germany
| | - Friedrich Förster
- Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, 82152, Martinsried, Germany
- Center for Biomolecular Research, Utrecht University, 3584 CH, Utrecht, The Netherlands
| | - Volkhard Helms
- Center for Bioinformatics, Saarland University, 66041, Saarbrücken, Germany
| | - Richard Zimmermann
- Competence Center for Molecular Medicine, Saarland University Medical School, Building 44, 66421, Homburg, Germany
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23
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Khan S, Godfrey V, Zaki MH. Cytosolic Nucleic Acid Sensors in Inflammatory and Autoimmune Disorders. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2018; 344:215-253. [PMID: 30798989 DOI: 10.1016/bs.ircmb.2018.10.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Innate immunity employs germline-encoded pattern recognition receptors (PRRs) to sense microbial pattern molecules. Recognition of pathogen-associated molecular patterns (PAMPs) by various PPRs located on the cell membrane or in the cytosol leads to the activation of cell signaling pathways and production of inflammatory mediators. Nucleic acids including DNA, RNA, and their derivatives are potent PAMPs which can be recognized by multiple PRRs to induce inflammatory responses. While nucleic acid sensors can also sense endogenous nucleic acids, they are capable of discriminating self from non-self. However, defects in nucleic acid sensing PRRs or dysregulation of nucleic acid sensing signaling pathways may cause excessive activation of the immune system resulting in the development of inflammatory and autoimmune diseases. This review will discuss the major pathways for sensing intracellular nucleic acids and how defects in these nucleic acid sensing are associated with different kinds of autoimmune and inflammatory disorders.
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Affiliation(s)
- Shahanshah Khan
- Department of Pathology, UT Southwestern Medical Center, Dallas, TX, United States
| | - Victoria Godfrey
- Department of Pathology, UT Southwestern Medical Center, Dallas, TX, United States
| | - Md Hasan Zaki
- Department of Pathology, UT Southwestern Medical Center, Dallas, TX, United States.
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24
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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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25
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Liu M, Weiss MA, Arunagiri A, Yong J, Rege N, Sun J, Haataja L, Kaufman RJ, Arvan P. Biosynthesis, structure, and folding of the insulin precursor protein. Diabetes Obes Metab 2018; 20 Suppl 2:28-50. [PMID: 30230185 PMCID: PMC6463291 DOI: 10.1111/dom.13378] [Citation(s) in RCA: 124] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 05/04/2018] [Accepted: 05/23/2018] [Indexed: 02/06/2023]
Abstract
Insulin synthesis in pancreatic β-cells is initiated as preproinsulin. Prevailing glucose concentrations, which oscillate pre- and postprandially, exert major dynamic variation in preproinsulin biosynthesis. Accompanying upregulated translation of the insulin precursor includes elements of the endoplasmic reticulum (ER) translocation apparatus linked to successful orientation of the signal peptide, translocation and signal peptide cleavage of preproinsulin-all of which are necessary to initiate the pathway of proper proinsulin folding. Evolutionary pressures on the primary structure of proinsulin itself have preserved the efficiency of folding ("foldability"), and remarkably, these evolutionary pressures are distinct from those protecting the ultimate biological activity of insulin. Proinsulin foldability is manifest in the ER, in which the local environment is designed to assist in the overall load of proinsulin folding and to favour its disulphide bond formation (while limiting misfolding), all of which is closely tuned to ER stress response pathways that have complex (beneficial, as well as potentially damaging) effects on pancreatic β-cells. Proinsulin misfolding may occur as a consequence of exuberant proinsulin biosynthetic load in the ER, proinsulin coding sequence mutations, or genetic predispositions that lead to an altered ER folding environment. Proinsulin misfolding is a phenotype that is very much linked to deficient insulin production and diabetes, as is seen in a variety of contexts: rodent models bearing proinsulin-misfolding mutants, human patients with Mutant INS-gene-induced Diabetes of Youth (MIDY), animal models and human patients bearing mutations in critical ER resident proteins, and, quite possibly, in more common variety type 2 diabetes.
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Affiliation(s)
- Ming Liu
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China 300052
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor 48105 MI USA
| | - Michael A. Weiss
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis 46202 IN USA
- Department of Biochemistry, Case-Western Reserve University, Cleveland 44016 OH USA
| | - Anoop Arunagiri
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor 48105 MI USA
| | - Jing Yong
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92307 USA
| | - Nischay Rege
- Department of Biochemistry, Case-Western Reserve University, Cleveland 44016 OH USA
| | - Jinhong Sun
- Department of Endocrinology and Metabolism, Tianjin Medical University General Hospital, Tianjin, China 300052
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor 48105 MI USA
| | - Leena Haataja
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor 48105 MI USA
| | - Randal J. Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92307 USA
| | - Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor 48105 MI USA
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26
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Lang S, Pfeffer S, Lee PH, Cavalié A, Helms V, Förster F, Zimmermann R. An Update on Sec61 Channel Functions, Mechanisms, and Related Diseases. Front Physiol 2017; 8:887. [PMID: 29163222 PMCID: PMC5672155 DOI: 10.3389/fphys.2017.00887] [Citation(s) in RCA: 95] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Accepted: 10/19/2017] [Indexed: 12/18/2022] Open
Abstract
The membrane of the endoplasmic reticulum (ER) of nucleated human cells harbors the protein translocon, which facilitates membrane integration or translocation of almost every newly synthesized polypeptide targeted to organelles of the endo- and exocytotic pathway. The translocon comprises the polypeptide-conducting Sec61 channel and several additional proteins and complexes that are permanently or transiently associated with the heterotrimeric Sec61 complex. This ensemble of proteins facilitates ER targeting of precursor polypeptides, modification of precursor polypeptides in transit through the Sec61 complex, and Sec61 channel gating, i.e., dynamic regulation of the pore forming subunit to mediate precursor transport and calcium efflux. Recently, cryoelectron tomography of translocons in native ER membrane vesicles, derived from human cell lines or patient fibroblasts, and even intact cells has given unprecedented insights into the architecture and dynamics of the native translocon and the Sec61 channel. These structural data are discussed in light of different Sec61 channel activities including ribosome receptor function, membrane insertion, and translocation of newly synthesized polypeptides as well as the putative physiological roles of the Sec61 channel as a passive ER calcium leak channel. Furthermore, the structural insights into the Sec61 channel are incorporated into an overview and update on Sec61 channel-related diseases—the Sec61 channelopathies—and novel therapeutic concepts for their treatment.
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Affiliation(s)
- Sven Lang
- Competence Center for Molecular Medicine, Saarland University Medical School, Homburg, Germany
| | - Stefan Pfeffer
- Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, Martinsried, Germany
| | - Po-Hsien Lee
- Center for Bioinformatics, Saarland University, Saarbrücken, Germany
| | - Adolfo Cavalié
- Experimental and Clinical Pharmacology and Toxicology, Saarland University, Homburg, Germany
| | - Volkhard Helms
- Center for Bioinformatics, Saarland University, Saarbrücken, Germany
| | - Friedrich Förster
- Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, Netherlands
| | - Richard Zimmermann
- Competence Center for Molecular Medicine, Saarland University Medical School, Homburg, Germany
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27
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Morgan MB, Edge SE, Venn AA, Jones RJ. Developing transcriptional profiles in Orbicella franksi exposed to copper: Characterizing responses associated with a spectrum of laboratory-controlled environmental conditions. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2017; 189:60-76. [PMID: 28599170 DOI: 10.1016/j.aquatox.2017.05.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 04/23/2017] [Accepted: 05/09/2017] [Indexed: 06/07/2023]
Affiliation(s)
- Michael B Morgan
- Department of Biology, Berry College, School of Mathematics and Natural Sciences, 2277 Martha Berry Hwy, Mount Berry, GA, 30149, USA.
| | - Sara E Edge
- Hawaii Pacific University, 45-045 Kamehameha Hwy, Kaneohe, HI, 96744, USA
| | - Alexander A Venn
- Marine Biology Department et Laboratoire International Associé 647 "BIOSENSIB", Centre Scientifique de Monaco, 8 Quai Antoine 1er, MC98000, Monaco
| | - Ross J Jones
- Australian Institute of Marine Science (AIMS), Perth, 6009, Australia
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28
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Abstract
Many proteins are translocated across the endoplasmic reticulum (ER) membrane in eukaryotes or the plasma membrane in prokaryotes. These proteins use hydrophobic signal sequences or transmembrane (TM) segments to trigger their translocation through the protein-conducting Sec61/SecY channel. Substrates are first directed to the channel by cytosolic targeting factors, which use hydrophobic pockets to bind diverse signal and TM sequences. Subsequently, these hydrophobic sequences insert into the channel, docking into a groove on the outside of the lateral gate of the channel, where they also interact with lipids. Structural data and biochemical experiments have elucidated how channel partners, the ribosome in cotranslational translocation, and the eukaryotic ER chaperone BiP or the prokaryotic cytosolic SecA ATPase in posttranslational translocation move polypeptides unidirectionally across the membrane. Structures of auxiliary components of the bacterial translocon, YidC and SecD/F, provide additional insight. Taken together, these recent advances result in mechanistic models of protein translocation.
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Affiliation(s)
- Tom A Rapoport
- Department of Cell Biology, Howard Hughes Medical Institute and Harvard Medical School, Boston, Massachusetts 02115; ,
| | - Long Li
- Department of Cell Biology, Howard Hughes Medical Institute and Harvard Medical School, Boston, Massachusetts 02115; ,
| | - Eunyong Park
- The Rockefeller University and Howard Hughes Medical Institute, New York, NY 10065;
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29
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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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30
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Bañó-Polo M, Martínez-Garay CA, Grau B, Martínez-Gil L, Mingarro I. Membrane insertion and topology of the translocon-associated protein (TRAP) gamma subunit. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:903-909. [PMID: 28132902 DOI: 10.1016/j.bbamem.2017.01.027] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Revised: 01/19/2017] [Accepted: 01/25/2017] [Indexed: 12/20/2022]
Abstract
Translocon-associated protein (TRAP) complex is intimately associated with the ER translocon for the insertion or translocation of newly synthesised proteins in eukaryotic cells. The TRAP complex is comprised of three single-spanning and one multiple-spanning subunits. We have investigated the membrane insertion and topology of the multiple-spanning TRAP-γ subunit by glycosylation mapping and green fluorescent protein fusions both in vitro and in cell cultures. Results demonstrate that TRAP-γ has four transmembrane (TM) segments, an Nt/Ct cytosolic orientation and that the less hydrophobic TM segment inserts efficiently into the membrane only in the cellular context of full-length protein.
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Affiliation(s)
- Manuel Bañó-Polo
- Departament de Bioquímica i Biologia Molecular, Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BioTecMed), Universitat de València, E-46 100 Burjassot, Spain
| | - Carlos A Martínez-Garay
- Departament de Bioquímica i Biologia Molecular, Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BioTecMed), Universitat de València, E-46 100 Burjassot, Spain
| | - Brayan Grau
- Departament de Bioquímica i Biologia Molecular, Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BioTecMed), Universitat de València, E-46 100 Burjassot, Spain
| | - Luis Martínez-Gil
- Departament de Bioquímica i Biologia Molecular, Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BioTecMed), Universitat de València, E-46 100 Burjassot, Spain
| | - Ismael Mingarro
- Departament de Bioquímica i Biologia Molecular, Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BioTecMed), Universitat de València, E-46 100 Burjassot, Spain.
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31
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Waite C, Mejia R, Ascoli M. Gq/11-Dependent Changes in the Murine Ovarian Transcriptome at the End of Gestation. Biol Reprod 2016; 94:62. [PMID: 26843449 PMCID: PMC4829089 DOI: 10.1095/biolreprod.115.136952] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Accepted: 02/01/2016] [Indexed: 11/26/2022] Open
Abstract
Parturition in rodents is highly dependent on the engagement of the luteal prostaglandin F2 alpha receptor, which, through activation of the Gq/11 family of G proteins, increases the expression of Akr1c18, leading to an increase in progesterone catabolism. To further understand the involvement of Gq/11 on luteolysis and parturition, we used microarray analysis to compare the ovarian transcriptome of mice with a granulosa/luteal cell-specific deletion of Galphaq/11 with their control littermates on Day 18 of pregnancy, when mice from both genotypes are pregnant, and on Day 22, when mice with a granulosa/luteal cell-specific deletion of Galphaq/11 are still pregnant but their control littermates are 1–2 days postpartum. Ovarian genes up-regulated at the end of gestation in a Galphaq/11 -dependent fashion include genes involved in focal adhesion and extracellular matrix interactions. Genes down-regulated at the end of gestation in a Galphaq/11-dependent manner include Serpina6 (which encodes corticosteroid-binding globulin); Enpp2 (which encodes autotaxin, the enzyme responsible for the synthesis of lysophosphatidic acid); genes involved in protein processing and export; reproductive genes, such as Lhcgr; the three genes needed to convert progesterone to estradiol (Cyp17a1, Hsd17b7, and Cyp19a1); and Inha. Activation of ovarian Gq/11 by engagement of the prostaglandin F2 alpha receptor on Day 18 of pregnancy recapitulated the regulation of many but not all of these genes. Thus, although the ovarian transcriptome at the end of gestation is highly dependent on the activation of Gq/11, not all of these changes are dependent on the actions of prostaglandin F2 alpha.
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Affiliation(s)
- Courtney Waite
- Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa
| | - Rachel Mejia
- Department of Obstetrics and Gynecology, Carver College of Medicine, University of Iowa, Iowa City, Iowa
| | - Mario Ascoli
- Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa
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32
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Stocki P, Sawicki M, Mays CE, Hong SJ, Chapman DC, Westaway D, Williams DB. Inhibition of the FKBP family of peptidyl prolyl isomerases induces abortive translocation and degradation of the cellular prion protein. Mol Biol Cell 2016; 27:757-67. [PMID: 26764098 PMCID: PMC4803302 DOI: 10.1091/mbc.e15-10-0729] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 01/04/2016] [Indexed: 11/11/2022] Open
Abstract
Prion diseases are fatal neurodegenerative disorders for which there is no effective treatment. Because the cellular prion protein (PrP(C)) is required for propagation of the infectious scrapie form of the protein, one therapeutic strategy is to reduce PrP(C) expression. Recently FK506, an inhibitor of the FKBP family of peptidyl prolyl isomerases, was shown to increase survival in animal models of prion disease, with proposed mechanisms including calcineurin inhibition, induction of autophagy, and reduced PrP(C) expression. We show that FK506 treatment results in a profound reduction in PrP(C) expression due to a defect in the translocation of PrP(C) into the endoplasmic reticulum with subsequent degradation by the proteasome. These phenotypes could be bypassed by replacing the PrP(C) signal sequence with that of prolactin or osteopontin. In mouse cells, depletion of ER luminal FKBP10 was almost as potent as FK506 in attenuating expression of PrP(C). However, this occurred at a later stage, after translocation of PrP(C) into the ER. Both FK506 treatment and FKBP10 depletion were effective in reducing PrP(Sc) propagation in cell models. These findings show the involvement of FKBP proteins at different stages of PrP(C) biogenesis and identify FKBP10 as a potential therapeutic target for the treatment of prion diseases.
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Affiliation(s)
- Pawel Stocki
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Maxime Sawicki
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Charles E Mays
- Centre for Prions and Protein Folding Diseases, University of Alberta, Edmonton, AB T6G 2M8, Canada
| | - Seo Jung Hong
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Daniel C Chapman
- Department of Immunology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - David Westaway
- Centre for Prions and Protein Folding Diseases, University of Alberta, Edmonton, AB T6G 2M8, Canada Division of Neurology and Departments of Chemistry and Biochemistry, University of Alberta, Edmonton, AB T6G 2M8, Canada
| | - David B Williams
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada Department of Immunology, University of Toronto, Toronto, ON M5S 1A8, Canada
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33
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Abstract
Secretion is the cellular process present in every organism that delivers soluble proteins and cargoes to the extracellular space. In eukaryotes, conventional protein secretion (CPS) is the trafficking route that secretory proteins undertake when are transported from the endoplasmic reticulum (ER) to the Golgi apparatus (GA), and subsequently to the plasma membrane (PM) via secretory vesicles or secretory granules. This book chapter recalls the fundamental steps in cell biology research contributing to the elucidation of CPS; it describes the most prominent examples of conventionally secreted proteins in eukaryotic cells and the molecular mechanisms necessary to regulate each step of this process.
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34
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Ng BG, Raymond K, Kircher M, Buckingham KJ, Wood T, Shendure J, Nickerson DA, Bamshad MJ, Wong JTS, Monteiro FP, Graham BH, Jackson S, Sparkes R, Scheuerle AE, Cathey S, Kok F, Gibson JB, Freeze HH. Expanding the Molecular and Clinical Phenotype of SSR4-CDG. Hum Mutat 2015; 36:1048-51. [PMID: 26264460 DOI: 10.1002/humu.22856] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Accepted: 08/02/2015] [Indexed: 01/16/2023]
Abstract
Congenital disorders of glycosylation (CDG) are a group of mostly autosomal recessive disorders primarily characterized by neurological abnormalities. Recently, we described a single CDG patient with a de novo mutation in the X-linked gene, Signal Sequence Receptor 4 (SSR4). We performed whole-exome sequencing to identify causal variants in several affected individuals who had either an undifferentiated neurological disorder or unsolved CDG of unknown etiology based on abnormal transferrin glycosylation. We now report eight affected males with either de novo (4) or inherited (4) loss of function mutations in SSR4. Western blot analysis revealed that the mutations caused a complete loss of SSR4 protein. In nearly all cases, the abnormal glycosylation of serum transferrin was only slightly above the accepted normal cutoff range.
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Affiliation(s)
- Bobby G Ng
- Human Genetics Program, Sanford - Burnham - Prebys Medical Discovery Institute, La Jolla, California
| | - Kimiyo Raymond
- Biochemical Genetics Laboratory, Mayo Clinic College of Medicine, Rochester, Minnesota
| | - Martin Kircher
- Department of Genome Sciences, University of Washington, Seattle, Washington
| | - Kati J Buckingham
- Department of Pediatrics, University of Washington, Seattle, Washington
| | - Tim Wood
- Department of Clinical Genetics, Greenwood Genetic Center, Charleston Office, North Charleston, South Caroline
| | - Jay Shendure
- Department of Genome Sciences, University of Washington, Seattle, Washington
| | - Deborah A Nickerson
- Department of Genome Sciences, University of Washington, Seattle, Washington
| | - Michael J Bamshad
- Department of Genome Sciences, University of Washington, Seattle, Washington.,Department of Pediatrics, University of Washington, Seattle, Washington
| | | | - Jonathan T S Wong
- Human Genetics Program, Sanford - Burnham - Prebys Medical Discovery Institute, La Jolla, California
| | - Fabiola Paoli Monteiro
- Department of Medical Genetics, University of Campinas (UNICAMP), São Paulo, Brazil.,Mendelics Genomic Analysis, São Paulo, São Paulo, Brazil
| | - Brett H Graham
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas
| | - Sheryl Jackson
- Department of Medical Genetics, University of Calgary, Calgary, AB, Canada
| | - Rebecca Sparkes
- Department of Medical Genetics, University of Calgary, Calgary, AB, Canada
| | - Angela E Scheuerle
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Sara Cathey
- Department of Clinical Genetics, Greenwood Genetic Center, Charleston Office, North Charleston, South Caroline
| | - Fernando Kok
- Mendelics Genomic Analysis, São Paulo, São Paulo, Brazil.,Department of Neurology, University of São Paulo, São Paulo, Brazil
| | - James B Gibson
- Clinical and Metabolic Genetics, Specially for Children, Austin, Texas
| | - Hudson H Freeze
- Human Genetics Program, Sanford - Burnham - Prebys Medical Discovery Institute, La Jolla, California
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35
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Jagannathan S, Hsu JCC, Reid DW, Chen Q, Thompson WJ, Moseley AM, Nicchitta CV. Multifunctional roles for the protein translocation machinery in RNA anchoring to the endoplasmic reticulum. J Biol Chem 2014; 289:25907-24. [PMID: 25063809 DOI: 10.1074/jbc.m114.580688] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Signal sequence-encoding mRNAs undergo translation-dependent localization to the endoplasmic reticulum (ER) and at the ER are anchored via translation on Sec61-bound ribosomes. Recent investigations into the composition and membrane association characteristics of ER-associated mRNAs have, however, revealed both ribosome-dependent (indirect) and ribosome-independent (direct) modes of mRNA association with the ER. These findings raise important questions regarding our understanding of how mRNAs are selected, localized, and anchored to the ER. Using semi-intact tissue culture cells, we performed a polysome solubilization screen and identified conditions that distinguish polysomes engaged in the translation of distinct cohorts of mRNAs. To gain insight into the molecular basis of direct mRNA anchoring to the ER, we performed RNA-protein UV photocross-linking studies in rough microsomes and demonstrate that numerous ER integral membrane proteins display RNA binding activity. Quantitative proteomic analyses of HeLa cytosolic and ER-bound polysome fractions identified translocon components as selective polysome-interacting proteins. Notably, the Sec61 complex was highly enriched in polysomes engaged in the translation of endomembrane organelle proteins, whereas translocon accessory proteins, such as ribophorin I, were present in all subpopulations of ER-associated polysomes. Analyses of the protein composition of oligo(dT)-selected UV photocross-linked ER protein-RNA adducts identified Sec61α,β and ribophorin I as ER-poly(A) mRNA-binding proteins, suggesting unexpected roles for the protein translocation and modification machinery in mRNA anchoring to the ER. In summary, we propose that multiple mechanisms of mRNA and ribosome association with ER operate to enable an mRNA transcriptome-wide function for the ER in protein synthesis.
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Affiliation(s)
| | | | | | - Qiang Chen
- From the Departments of Cell Biology and
| | - Will J Thompson
- the Duke Proteomics Core Facility, Duke University Medical Center, Durham, North Carolina 27710
| | - Arthur M Moseley
- the Duke Proteomics Core Facility, Duke University Medical Center, Durham, North Carolina 27710
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36
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Denks K, Vogt A, Sachelaru I, Petriman NA, Kudva R, Koch HG. The Sec translocon mediated protein transport in prokaryotes and eukaryotes. Mol Membr Biol 2014; 31:58-84. [DOI: 10.3109/09687688.2014.907455] [Citation(s) in RCA: 123] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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37
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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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38
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Losfeld ME, Ng BG, Kircher M, Buckingham KJ, Turner EH, Eroshkin A, Smith JD, Shendure J, Nickerson DA, Bamshad MJ, Freeze HH. A new congenital disorder of glycosylation caused by a mutation in SSR4, the signal sequence receptor 4 protein of the TRAP complex. Hum Mol Genet 2013; 23:1602-5. [PMID: 24218363 DOI: 10.1093/hmg/ddt550] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Nearly 50 congenital disorders of glycosylation (CDG) are known, but many patients biochemically diagnosed with CDG do not have mutations in known genes. Here, we describe a 16-year-old male who was born with microcephaly, developed intellectual disability, gastroesophageal reflux and a seizure disorder. We identified a de novo variant in the X-linked SSR4 gene which encodes a protein of the heterotetrameric translocon-associated protein (TRAP) complex. The c.316delT causes a p.F106Sfs*53 in SSR4 and also reduces expression of other TRAP complex proteins. The glycosylation marker Glyc-ER-GFP was used to confirm the underglycosylation in fibroblasts from the patient. Overexpression of the wild-type SSR4 allele partially restores glycosylation of the marker and of the other members of the TRAP complex. This is the first evidence that the TRAP complex, which binds to the oligosaccharyltransferase complex, is directly involved in N-glycosylation.
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Affiliation(s)
- Marie Estelle Losfeld
- Genetic Disease Program, Sanford Children's Health Research Center, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037, USA
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39
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Chen HZ, Wen Q, Wang WJ, He JP, Wu Q. The orphan nuclear receptor TR3/Nur77 regulates ER stress and induces apoptosis via interaction with TRAPγ. Int J Biochem Cell Biol 2013; 45:1600-9. [PMID: 23660295 DOI: 10.1016/j.biocel.2013.04.026] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Revised: 04/11/2013] [Accepted: 04/29/2013] [Indexed: 12/09/2022]
Abstract
The orphan nuclear receptor TR3 (also known as Nur77) belongs to the steroid/thyroid/retinoid nuclear receptor superfamily and plays important roles in regulating cell proliferation, differentiation and apoptosis. No physiological ligand for TR3 has been found thus far; the determination of its binding partners is therefore important to clarify the biological functions of TR3. Here, we identified translocon-associated protein subunit γ (TRAPγ) as a novel TR3 binding partner using a tandem affinity purification method. This interaction between TR3 and TRAPγ was further confirmed, and the interacting regions were mapped. The ligand-binding domain of TR3 was required for TRAPγ binding, and the C terminus of TRAPγ was responsible for its interaction with TR3. When stimulated with 12-O-tetradecanoylphorbol 13-acetate (TPA) or CD437, this TR3-TRAPγ interaction not only induced Ca(2+) depletion in the endoplasmic reticulum (ER) but also promoted the expression of the proapoptotic transcriptional regulator CHOP. Notably, both TR3 and TRAPγ were required for ER stress-induced apoptosis in HepG2 cells. Overall, this study demonstrated a novel, TR3-initiated signaling pathway in which TR3 regulates ER stress and induces apoptosis of hepatoma cells through its interaction with TRAPγ.
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Affiliation(s)
- Hang-zi Chen
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen 361102, Fujian Province, PR China.
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40
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Yoo JK, Choi SJ, Kim JK. Expression profiles of subtracted mRNAs during cellular senescence in human mesenchymal stem cells derived from bone marrow. Exp Gerontol 2013; 48:464-71. [PMID: 23466301 DOI: 10.1016/j.exger.2013.02.022] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Revised: 02/08/2013] [Accepted: 02/19/2013] [Indexed: 12/17/2022]
Abstract
Cellular senescence is an irreversible cell cycle arrest that limits the replicative lifespan of cells. Senescence suppresses development of tumors by regulating aging factors, such as cyclin dependent kinase inhibitor (CKI) and telomerase. Suppression subtractive hybridization (SSH) was used to identify genes that were differentially expressed between young human mesenchymal stem cells (Y-hMSCs) and senescent human mesenchymal stem cells (S-hMSCs). We selected positive clones that were functionally characterized by referring to public databases using NCBI BLAST tool. This search revealed that 19 genes were downregulated, and 43 genes were upregulated in S-hMSCs relative to Y-hMSCs. Among subtracted clones in Y-hMSCs, most of genes markedly were related to metabolic functions. These genes, PDIA3, WDR1, FSTL1, COPG1, LMAN1, and PDIA6, significantly downregulated. Conversely, genes for subtracted clones in S-hMSCs were mostly associated with cell adhesion. In particular, the expression levels of 9 genes, HSP90B1, EID1, ATP2B4, DDAH1, PRNP, RAB1A, PGS5, TM4SF1 and SSR3, gradually increased during senescence. These genes have not previously been identified as being related to cellular senescence, but they seemed to be potentially affected during cellular senescence.
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Affiliation(s)
- Jung Ki Yoo
- Department of Pharmacy, College of Pharmacy, CHA University, 222 Yatap-dong, Bundang-gu, Seongnam-si, Gyeonggi-do 463-836, Republic of Korea
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41
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Pfeffer S, Brandt F, Hrabe T, Lang S, Eibauer M, Zimmermann R, Förster F. Structure and 3D arrangement of endoplasmic reticulum membrane-associated ribosomes. Structure 2012; 20:1508-18. [PMID: 22819217 DOI: 10.1016/j.str.2012.06.010] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 05/14/2012] [Accepted: 06/11/2012] [Indexed: 12/22/2022]
Abstract
In eukaryotic cells, cotranslational protein translocation across the endoplasmic reticulum (ER) membrane requires an elaborate macromolecular machinery. While structural details of ribosomes bound to purified and solubilized constituents of the translocon have been elucidated in recent years, little structural knowledge of ribosomes bound to the complete ER protein translocation machinery in a native membrane environment exists. Here, we used cryoelectron tomography to provide a three-dimensional reconstruction of 80S ribosomes attached to functional canine pancreatic ER microsomes in situ. In the resulting subtomogram average at 31 Å resolution, we observe direct contact of ribosomal expansion segment ES27L and the membrane and distinguish several membrane-embedded and lumenal complexes, including Sec61, the TRAP complex and another large complex protruding 90 Å into the lumen. Membrane-associated ribosomes adopt a preferred three-dimensional arrangement that is likely specific for ER-associated polyribosomes and may explain the high translation efficiency of ER-associated ribosomes compared to their cytosolic counterparts.
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Affiliation(s)
- Stefan Pfeffer
- Department of Molecular Structural Biology, Max-Planck Institute of Biochemistry, D-82152 Martinsried, Germany
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42
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Higa A, Mulot A, Delom F, Bouchecareilh M, Nguyên DT, Boismenu D, Wise MJ, Chevet E. Role of pro-oncogenic protein disulfide isomerase (PDI) family member anterior gradient 2 (AGR2) in the control of endoplasmic reticulum homeostasis. J Biol Chem 2011; 286:44855-68. [PMID: 22025610 PMCID: PMC3248018 DOI: 10.1074/jbc.m111.275529] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Revised: 10/10/2011] [Indexed: 12/30/2022] Open
Abstract
The protein-disulfide isomerase (PDI) family member anterior gradient 2 (AGR2) is reportedly overexpressed in numerous cancers and plays a role in cancer development. However, to date the molecular functions of AGR2 remain to be characterized. Herein we have identified AGR2 as bound to newly synthesized cargo proteins using a proteomics analysis of endoplasmic reticulum (ER) membrane-bound ribosomes. Nascent protein chains that translocate into the ER associate with specific ER luminal proteins, which in turn ensures proper folding and posttranslational modifications. Using both imaging and biochemical approaches, we confirmed that AGR2 localizes to the lumen of the ER and indirectly associates with ER membrane-bound ribosomes through nascent protein chains. We showed that AGR2 expression is controlled by the unfolded protein response and is in turn is involved in the maintenance of ER homeostasis. Remarkably, we have demonstrated that siRNA-mediated knockdown of AGR2 significantly alters the expression of components of the ER-associated degradation machinery and reduces the ability of cells to cope with acute ER stress, properties that might be relevant to the role of AGR2 in cancer development.
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Affiliation(s)
- Arisa Higa
- From INSERM U1053, Avenir, 33076 Bordeaux, France
- the Université Bordeaux Segalen, 33076 Bordeaux, France
| | - Audrey Mulot
- From INSERM U1053, Avenir, 33076 Bordeaux, France
- the Université Bordeaux Segalen, 33076 Bordeaux, France
| | - Frédéric Delom
- the Department of Surgery, McGill University, Montreal, Quebec, Canada
| | - Marion Bouchecareilh
- From INSERM U1053, Avenir, 33076 Bordeaux, France
- the Université Bordeaux Segalen, 33076 Bordeaux, France
| | - Duc Thang Nguyên
- the Department of Surgery, McGill University, Montreal, Quebec, Canada
| | - Daniel Boismenu
- McGill University and the Génome Québec Innovation Centre, Montreal, Quebec, Canada, and
| | - Michael J. Wise
- the Department of Biomolecular, Biomedical, and Chemical Sciences, University of Western Australia, Perth, Australia
| | - Eric Chevet
- From INSERM U1053, Avenir, 33076 Bordeaux, France
- the Université Bordeaux Segalen, 33076 Bordeaux, France
- the Department of Surgery, McGill University, Montreal, Quebec, Canada
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43
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44
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Martínez-Gil L, Saurí A, Marti-Renom MA, Mingarro I. Membrane protein integration into the endoplasmic reticulum. FEBS J 2011; 278:3846-58. [PMID: 21592307 DOI: 10.1111/j.1742-4658.2011.08185.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Most integral membrane proteins are targeted, inserted and assembled in the endoplasmic reticulum membrane. The sequential and potentially overlapping events necessary for membrane protein integration take place at sites termed translocons, which comprise a specific set of membrane proteins acting in concert with ribosomes and, probably, molecular chaperones to ensure the success of the whole process. In this minireview, we summarize our current understanding of helical membrane protein integration at the endoplasmic reticulum, and highlight specific characteristics that affect the biogenesis of multispanning membrane proteins.
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Affiliation(s)
- Luis Martínez-Gil
- Departament de Bioquímica i Biologia Molecular, Universitat de València, Burjassot, Spain
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45
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Schülein R, Westendorf C, Krause G, Rosenthal W. Functional significance of cleavable signal peptides of G protein-coupled receptors. Eur J Cell Biol 2011; 91:294-9. [PMID: 21543132 DOI: 10.1016/j.ejcb.2011.02.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2010] [Revised: 02/25/2011] [Accepted: 02/25/2011] [Indexed: 01/22/2023] Open
Abstract
About 5-10% of the G protein-coupled receptors (GPCRs) contain N-terminal signal peptides that are cleaved off by the signal peptidases of the endoplasmic reticulum (ER) during the translocon-mediated receptor insertion into the ER membrane. The reason as to why only a subset of the GPCRs requires these additional signal peptides was addressed in the past decade only by a limited number of studies. Recent progress suggests that signal peptides of GPCRs do not only serve the classical ER targeting and translocon gating functions as described for the signal peptides of secretory proteins. In the case of GPCRs, uncleaved pseudo signal peptides may regulate receptor expression at the plasma membrane and may also influence G protein coupling. Moreover, signal peptides of GPCRs seem to match functionally with sequences of the mature N tails. In this review, we summarize the current knowledge about cleavable signal peptides of GPCRs and address the question whether these sequences may be future drug targets in pharmacology.
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Affiliation(s)
- Ralf Schülein
- Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany.
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46
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Barber GN. Innate immune DNA sensing pathways: STING, AIMII and the regulation of interferon production and inflammatory responses. Curr Opin Immunol 2011. [PMID: 21239155 DOI: 10.1016/j.coi.2010.1012.1015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The early detection of microbes is the responsibility of the innate immune system which has evolved to sense pathogen derived molecules such as lipopolysaccharides and non-self nucleic acid, to trigger host defense countermeasures. These sensors include the RIG-I-like helicase (RLH) family that specifically recognizes viral RNA, as well as the cytoplasmic, nucleotide binding oligermerization domain (NOD)-like receptor and Toll-like receptor (TLR) pathways that sense a variety of microbial derived molecules. Comprehending how the cell senses foreign DNA, generated by certain viruses, bacteria and possibly parasites has proven elusive but is of significant importance since such information could shed insight into the causes of microbial related disease, including viral associated cancers and autoimmune disorders. Plasmacytoid dendritic cells are known to utilize TLR9 to detect pathogen-associated DNA and to trigger the production of type I interferon (IFN), as well as other cytokines, although alternate key DNA detecting sensors remain to be identified. Recently however, a molecule referred to as AIM2 (absent in melanoma 2) was found to be essential for mediating inflammatory reactions triggered by cytoplasmic DNA. In addition, an endoplasmic reticulum associated protein referred to as STING (for stimulator of interferon genes) was demonstrated as being pivotal for facilitating IFN production in response to intracellular DNA and a variety of DNA pathogens. Here, we review recent discoveries relating to the detection of foreign DNA, including the importance of the STING and AIM2 and the activation of innate signaling pathways.
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Affiliation(s)
- Glen N Barber
- Department of Medicine and Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Miami, FL 33136, United States.
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47
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Barber GN. Innate immune DNA sensing pathways: STING, AIMII and the regulation of interferon production and inflammatory responses. Curr Opin Immunol 2011; 23:10-20. [PMID: 21239155 DOI: 10.1016/j.coi.2010.12.015] [Citation(s) in RCA: 190] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2010] [Revised: 12/23/2010] [Accepted: 12/27/2010] [Indexed: 01/20/2023]
Abstract
The early detection of microbes is the responsibility of the innate immune system which has evolved to sense pathogen derived molecules such as lipopolysaccharides and non-self nucleic acid, to trigger host defense countermeasures. These sensors include the RIG-I-like helicase (RLH) family that specifically recognizes viral RNA, as well as the cytoplasmic, nucleotide binding oligermerization domain (NOD)-like receptor and Toll-like receptor (TLR) pathways that sense a variety of microbial derived molecules. Comprehending how the cell senses foreign DNA, generated by certain viruses, bacteria and possibly parasites has proven elusive but is of significant importance since such information could shed insight into the causes of microbial related disease, including viral associated cancers and autoimmune disorders. Plasmacytoid dendritic cells are known to utilize TLR9 to detect pathogen-associated DNA and to trigger the production of type I interferon (IFN), as well as other cytokines, although alternate key DNA detecting sensors remain to be identified. Recently however, a molecule referred to as AIM2 (absent in melanoma 2) was found to be essential for mediating inflammatory reactions triggered by cytoplasmic DNA. In addition, an endoplasmic reticulum associated protein referred to as STING (for stimulator of interferon genes) was demonstrated as being pivotal for facilitating IFN production in response to intracellular DNA and a variety of DNA pathogens. Here, we review recent discoveries relating to the detection of foreign DNA, including the importance of the STING and AIM2 and the activation of innate signaling pathways.
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Affiliation(s)
- Glen N Barber
- Department of Medicine and Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Miami, FL 33136, United States.
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48
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Yamaguchi YL, Tanaka SS, Oshima N, Kiyonari H, Asashima M, Nishinakamura R. Translocon-associated protein subunit Trap-γ/Ssr3 is required for vascular network formation in the mouse placenta. Dev Dyn 2011; 240:394-403. [DOI: 10.1002/dvdy.22528] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/10/2010] [Indexed: 12/12/2022] Open
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49
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Ishikawa H, Barber GN. The STING pathway and regulation of innate immune signaling in response to DNA pathogens. Cell Mol Life Sci 2010; 68:1157-65. [PMID: 21161320 PMCID: PMC3056141 DOI: 10.1007/s00018-010-0605-2] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Revised: 11/19/2010] [Accepted: 11/25/2010] [Indexed: 12/24/2022]
Abstract
The innate immune system has evolved a variety of sensing mechanisms to detect and counter microbial invasion. These include the Toll-like receptor (TLR), cytoplasmic, nucleotide binding oligomerization domain (NOD)-like receptor and RIG-I-like helicase (RLH) pathways. However, how the cell detects pathogen-associated DNA to trigger host defense, including the production of interferon, remains to be fully clarified. Understanding these processes could have profound implications into how we understand and treat a variety of microbial-related disease, including viral-associated cancers, as well as autoimmune disorders. Recently, an endoplasmic reticulum-associated molecule referred to as STING (for stimulator of interferon genes) was isolated and shown to be critical for regulating the production of IFN in response to cytoplasmic DNA. Here, we review recent discoveries relating to the detection of foreign DNA, including the importance of the STING and inflammasome pathways and the triggering of innate signaling processes.
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Affiliation(s)
- Hiroki Ishikawa
- Department of Medicine and Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Rm 511 Papanicolaou Building [M700], 1550 NW 10th Ave, Miami, FL 33136 USA
| | - Glen N. Barber
- Department of Medicine and Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Rm 511 Papanicolaou Building [M700], 1550 NW 10th Ave, Miami, FL 33136 USA
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50
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Cheung VG, Nayak RR, Wang IX, Elwyn S, Cousins SM, Morley M, Spielman RS. Polymorphic cis- and trans-regulation of human gene expression. PLoS Biol 2010; 8. [PMID: 20856902 PMCID: PMC2939022 DOI: 10.1371/journal.pbio.1000480] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2010] [Accepted: 08/03/2010] [Indexed: 12/11/2022] Open
Abstract
Using genetic and molecular analyses, we identified over 1,000 polymorphic regulators that regulate expression levels of human genes. Expression levels of human genes vary extensively among individuals. This variation facilitates analyses of expression levels as quantitative phenotypes in genetic studies where the entire genome can be scanned for regulators without prior knowledge of the regulatory mechanisms, thus enabling the identification of unknown regulatory relationships. Here, we carried out such genetic analyses with a large sample size and identified cis- and trans-acting polymorphic regulators for about 1,000 human genes. We validated the cis-acting regulators by demonstrating differential allelic expression with sequencing of transcriptomes (RNA-Seq) and the trans-regulators by gene knockdown, metabolic assays, and chromosome conformation capture analysis. The majority of the regulators act in trans to the target (regulated) genes. Most of these trans-regulators were not known to play a role in gene expression regulation. The identification of these regulators enabled the characterization of polymorphic regulation of human gene expression at a resolution that was unattainable in the past. Cellular characteristics and functions are determined largely by gene expression and expression levels differ among individuals, however it is not clear how these levels are regulated. While many cis-acting DNA sequence variants in promoters and enhancers that influence gene expression have been identified, only a few polymorphic trans-regulators of human genes are known. Here, we used human B-cells from individuals belonging to large families and identified polymorphic trans-regulators for about 1,000 human genes. We validated these results by gene knockdown, metabolic perturbation studies and chromosome conformation capture assays. Although these regulatory relationships were identified in cultured B-cells, we show that some of the relationships were also found in primary fibroblasts. The large number of regulators allowed us to better understand gene expression regulation, to uncover new gene functions, and to identify their roles in disease processes. This study shows that genetic variation is a powerful tool not only for gene mapping but also to study gene interaction and regulation.
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Affiliation(s)
- Vivian G Cheung
- Howard Hughes Medical Institute, Philadelphia, Pennsylvania, USA.
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