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Tanaka T, Chung HL. Exploiting fly models to investigate rare human neurological disorders. Neural Regen Res 2025; 20:21-28. [PMID: 38767473 PMCID: PMC11246155 DOI: 10.4103/nrr.nrr-d-23-01847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Revised: 02/05/2024] [Accepted: 03/02/2024] [Indexed: 05/22/2024] Open
Abstract
Rare neurological diseases, while individually are rare, collectively impact millions globally, leading to diverse and often severe neurological symptoms. Often attributed to genetic mutations that disrupt protein function or structure, understanding their genetic basis is crucial for accurate diagnosis and targeted therapies. To investigate the underlying pathogenesis of these conditions, researchers often use non-mammalian model organisms, such as Drosophila (fruit flies), which is valued for their genetic manipulability, cost-efficiency, and preservation of genes and biological functions across evolutionary time. Genetic tools available in Drosophila, including CRISPR-Cas9, offer a means to manipulate gene expression, allowing for a deep exploration of the genetic underpinnings of rare neurological diseases. Drosophila boasts a versatile genetic toolkit, rapid generation turnover, and ease of large-scale experimentation, making it an invaluable resource for identifying potential drug candidates. Researchers can expose flies carrying disease-associated mutations to various compounds, rapidly pinpointing promising therapeutic agents for further investigation in mammalian models and, ultimately, clinical trials. In this comprehensive review, we explore rare neurological diseases where fly research has significantly contributed to our understanding of their genetic basis, pathophysiology, and potential therapeutic implications. We discuss rare diseases associated with both neuron-expressed and glial-expressed genes. Specific cases include mutations in CDK19 resulting in epilepsy and developmental delay, mutations in TIAM1 leading to a neurodevelopmental disorder with seizures and language delay, and mutations in IRF2BPL causing seizures, a neurodevelopmental disorder with regression, loss of speech, and abnormal movements. And we explore mutations in EMC1 related to cerebellar atrophy, visual impairment, psychomotor retardation, and gain-of-function mutations in ACOX1 causing Mitchell syndrome. Loss-of-function mutations in ACOX1 result in ACOX1 deficiency, characterized by very-long-chain fatty acid accumulation and glial degeneration. Notably, this review highlights how modeling these diseases in Drosophila has provided valuable insights into their pathophysiology, offering a platform for the rapid identification of potential therapeutic interventions. Rare neurological diseases involve a wide range of expression systems, and sometimes common phenotypes can be found among different genes that cause abnormalities in neurons or glia. Furthermore, mutations within the same gene may result in varying functional outcomes, such as complete loss of function, partial loss of function, or gain-of-function mutations. The phenotypes observed in patients can differ significantly, underscoring the complexity of these conditions. In conclusion, Drosophila represents an indispensable and cost-effective tool for investigating rare neurological diseases. By facilitating the modeling of these conditions, Drosophila contributes to a deeper understanding of their genetic basis, pathophysiology, and potential therapies. This approach accelerates the discovery of promising drug candidates, ultimately benefiting patients affected by these complex and understudied diseases.
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Affiliation(s)
- Tomomi Tanaka
- Department of Neurology, Houston Methodist Research Institute, Houston, TX, USA
| | - Hyung-Lok Chung
- Department of Neurology, Houston Methodist Research Institute, Houston, TX, USA
- Department of Neurology, Weill Cornell Medical College, New York, NY, USA
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2
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Chen K, Wang Y, Yang J, Klöting N, Liu C, Dai J, Jin S, Chen L, Liu S, Liu Y, Yu Y, Liu X, Miao Q, Liew CW, Wang Y, Dietrich A, Blüher M, Wang X. EMC10 modulates hepatic ER stress and steatosis in an isoform-specific manner. J Hepatol 2024; 81:479-491. [PMID: 38599383 DOI: 10.1016/j.jhep.2024.03.047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 03/26/2024] [Accepted: 03/27/2024] [Indexed: 04/12/2024]
Abstract
BACKGROUND & AIMS Endoplasmic reticulum (ER) membrane protein complex subunit 10 (EMC10) has been implicated in obesity. Here we investigated the roles of the two isoforms of EMC10, including a secreted isoform (scEMC10) and an ER membrane-bound isoform (mEMC10), in metabolic dysfunction-associated steatotic liver disease (MASLD). METHODS Manifold steatotic mouse models and HepG2 cells were employed to investigate the role of EMC10 in the regulation of hepatic PERK-eIF2α-ATF4 signaling and hepatosteatosis. The therapeutic effect of scEMC10-neutralizing antibody on mouse hepatosteatosis was explored. Associations of MASLD with serum scEMC10 and hepatic mEMC10 were determined in two cohorts of participants with MASLD. RESULTS scEMC10 promoted, while mEMC10 suppressed, the activation of hepatic PERK-eIF2α-ATF4 signaling. Emc10 gene knockout exacerbated, while hepatic overexpression of mEMC10 ameliorated, hepatic ER stress and steatosis in mice challenged with either a methionine- and choline-deficient diet or tunicamycin, highlighting a direct, suppressive role of mEMC10 in MASLD via modulation of hepatic ER stress. Overexpression of scEMC10 promoted, whereas neutralization of circulating scEMC10 prevented, hepatosteatosis in mice with fatty liver, suggesting a role of scEMC10 in MASLD development. Clinically, serum scEMC10 was increased, while hepatic mEMC10 was decreased, in participants with MASLD. Correlative analysis indicated that serum scEMC10 positively, whereas hepatic mEMC10 negatively, correlated with liver fat content and serum ALT, AST, and GGT. CONCLUSIONS These findings demonstrate a novel isoform-specific role for EMC10 in the pathogenesis of MASLD and identify the secreted isoform as a tractable therapeutic target for MASLD via antibody-based neutralization. IMPACT AND IMPLICATIONS We have shown the role of EMC10 in the regulation of energy homeostasis and obesity. In this study, we determine the distinct roles of the two isoforms of EMC10 in the regulation of hepatic endoplasmic reticulum stress and steatosis in mice, and report on the associations of the different EMC10 isoforms with metabolic dysfunction-associated steatotic liver disease in humans. Our findings delineate a novel regulatory axis for hepatosteatosis and identify EMC10 as a modulator of the PERK-eIF2α-ATF4 signaling cascade that may be of broad physiological significance. Moreover, our pre-clinical and clinical studies provide evidence of the therapeutic potential of targeting scEMC10 in MASLD.
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Affiliation(s)
- Kuangyang Chen
- Department of Endocrinology, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China; Department of Endocrinology, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Yahao Wang
- Department of Endocrinology, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China
| | - Jia Yang
- Department of Endocrinology, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China
| | - Nora Klöting
- Helmholtz Institute for Metabolic, Obesity and Vascular Research (HI-MAG) of the Helmholtz Zentrum München at the University of Leipzig and University Hospital Leipzig, Leipzig, Germany; Medical Department III - Endocrinology, Nephrology, Rheumatology, University of Leipzig Medical Center, Leipzig, Germany
| | - Chuanfeng Liu
- Department of Endocrinology and Metabolism, The Affiliated Hospital of Qingdao University, Qingdao, China
| | - Jiarong Dai
- Department of Endocrinology, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China
| | - Shuoshuo Jin
- Department of Endocrinology, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China
| | - Lijiao Chen
- Department of Endocrinology, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China
| | - Shan Liu
- Department of Endocrinology, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China
| | - Yuzhao Liu
- Department of Endocrinology and Metabolism, The Affiliated Hospital of Qingdao University, Qingdao, China
| | - Yongzhuo Yu
- Department of Endocrinology and Metabolism, The Affiliated Hospital of Qingdao University, Qingdao, China
| | - Xiaoxia Liu
- Department of Endocrinology, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China
| | - Qing Miao
- Department of Endocrinology, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China
| | - Chong Wee Liew
- Department of Physiology & Biophysics, University of Illinois at Chicago, Chicago, IL, USA
| | - Yangang Wang
- Department of Endocrinology and Metabolism, The Affiliated Hospital of Qingdao University, Qingdao, China
| | - Arne Dietrich
- Department of Visceral, Transplant, Thoracic and Vascular Surgery, University Hospital Leipzig, Leipzig, Germany
| | - Matthias Blüher
- Helmholtz Institute for Metabolic, Obesity and Vascular Research (HI-MAG) of the Helmholtz Zentrum München at the University of Leipzig and University Hospital Leipzig, Leipzig, Germany; Medical Department III - Endocrinology, Nephrology, Rheumatology, University of Leipzig Medical Center, Leipzig, Germany
| | - Xuanchun Wang
- Department of Endocrinology, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China.
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3
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Sun K, Liu L, Jiang X, Wang H, Wang L, Yang Y, Liu W, Zhang L, Zhao X, Zhu X. The endoplasmic reticulum membrane protein complex subunit Emc6 is essential for rhodopsin localization and photoreceptor cell survival. Genes Dis 2024; 11:1035-1049. [PMID: 37692493 PMCID: PMC10492031 DOI: 10.1016/j.gendis.2023.03.033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 02/17/2023] [Accepted: 03/29/2023] [Indexed: 09/12/2023] Open
Abstract
The endoplasmic reticulum (ER) membrane protein complex (EMC) is responsible for monitoring the biogenesis and synthetic quality of membrane proteins with tail-anchored or multiple transmembrane domains. The EMC subunit EMC6 is one of the core members of EMC and forms an enclosed hydrophilic vestibule in cooperation with EMC3. Despite studies demonstrating that deletion of EMC3 led to rhodopsin mislocalization in rod photoreceptors of mice, the precise mechanism leading to the failure of rhodopsin trafficking remains unclear. Here, we generated the first rod photoreceptor-specific knockout of Emc6 (RKO) and cone photoreceptor-specific knockout of Emc6 (CKO) mouse models. Deficiency of Emc6 in rod photoreceptors led to progressive shortening of outer segments (OS), impaired visual function, mislocalization and reduced expression of rhodopsin, and increased gliosis in rod photoreceptors. In addition, CKO mice displayed the progressive death of cone photoreceptors and abnormal localization of cone opsin protein. Subsequently, proteomics analysis of the RKO mouse retina illustrated that several cilium-related proteins, particularly anoctamin-2 (ANO2) and transmembrane protein 67 (TMEM67), were significantly down-regulated prior to OS degeneration. Detrimental rod photoreceptor cilia and mislocalized membrane disc proteins were evident in RKO mice. Our data revealed that in addition to monitoring the synthesis of rhodopsin-dominated membrane disc proteins, EMC6 also impacted rod photoreceptors' ciliogenesis by regulating the synthesis of membrane proteins associated with cilia, contributing to the mislocalization of membrane disc proteins.
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Affiliation(s)
- Kuanxiang Sun
- Health Management Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
- Key Laboratory of Tibetan Medicine Research, Chinese Academy of Sciences and Qinghai Provincial Key Laboratory of Tibetan Medicine Research, Northwest Institute of Plateau Biology, Xining, Qinghai 810008, China
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
- Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, Sichuan 610072, China
| | - Lu Liu
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Xiaoyan Jiang
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Heting Wang
- Health Management Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Lin Wang
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Yeming Yang
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Wenjing Liu
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Lin Zhang
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
| | - Xiaohui Zhao
- Key Laboratory of Tibetan Medicine Research, Chinese Academy of Sciences and Qinghai Provincial Key Laboratory of Tibetan Medicine Research, Northwest Institute of Plateau Biology, Xining, Qinghai 810008, China
| | - Xianjun Zhu
- Health Management Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
- Key Laboratory of Tibetan Medicine Research, Chinese Academy of Sciences and Qinghai Provincial Key Laboratory of Tibetan Medicine Research, Northwest Institute of Plateau Biology, Xining, Qinghai 810008, China
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 610072, China
- Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, Sichuan 610072, China
- Department of Ophthalmology, The First People's Hospital of Shangqiu, Shangqiu, Henan 476000, China
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4
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Wu H, Smalinskaitė L, Hegde RS. EMC rectifies the topology of multipass membrane proteins. Nat Struct Mol Biol 2024; 31:32-41. [PMID: 37957425 PMCID: PMC10803268 DOI: 10.1038/s41594-023-01120-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 09/08/2023] [Indexed: 11/15/2023]
Abstract
Most eukaryotic multipass membrane proteins are inserted into the membrane of the endoplasmic reticulum. Their transmembrane domains (TMDs) are thought to be inserted co-translationally as they emerge from a membrane-bound ribosome. Here we find that TMDs near the carboxyl terminus of mammalian multipass proteins are inserted post-translationally by the endoplasmic reticulum membrane protein complex (EMC). Site-specific crosslinking shows that the EMC's cytosol-facing hydrophilic vestibule is adjacent to a pre-translocated C-terminal tail. EMC-mediated insertion is mostly agnostic to TMD hydrophobicity, favored for short uncharged C-tails and stimulated by a preceding unassembled TMD bundle. Thus, multipass membrane proteins can be released by the ribosome-translocon complex in an incompletely inserted state, requiring a separate EMC-mediated post-translational insertion step to rectify their topology, complete biogenesis and evade quality control. This sequential co-translational and post-translational mechanism may apply to ~250 diverse multipass proteins, including subunits of the pentameric ion channel family that are crucial for neurotransmission.
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Affiliation(s)
- Haoxi Wu
- MRC Laboratory of Molecular Biology, Cambridge, UK
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5
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Shi L, Ma H, Wang J, Ma M, Zhao H, Li Z, Wang JH, Wu S, Zhou Z, Dong MQ, Li Z. An EMC-Hpo-Yki axis maintains intestinal homeostasis under physiological and pathological conditions. Development 2023; 150:dev201958. [PMID: 38031990 DOI: 10.1242/dev.201958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2023] [Accepted: 11/08/2023] [Indexed: 12/01/2023]
Abstract
Balanced control of stem cell proliferation and differentiation underlines tissue homeostasis. Disruption of tissue homeostasis often results in many diseases. However, how endogenous factors influence the proliferation and differentiation of intestinal stem cells (ISCs) under physiological and pathological conditions remains poorly understood. Here, we find that the evolutionarily conserved endoplasmic reticulum membrane protein complex (EMC) negatively regulates ISC proliferation and intestinal homeostasis. Compromising EMC function in progenitors leads to excessive ISC proliferation and intestinal homeostasis disruption. Mechanistically, the EMC associates with and stabilizes Hippo (Hpo) protein, the key component of the Hpo signaling pathway. In the absence of EMC, Yorkie (Yki) is activated to promote ISC proliferation due to Hpo destruction. The EMC-Hpo-Yki axis also functions in enterocytes to maintain intestinal homeostasis. Importantly, the levels of the EMC are dramatically diminished in tunicamycin-treated animals, leading to Hpo destruction, thereby resulting in intestinal homeostasis disruption due to Yki activation. Thus, our study uncovers the molecular mechanism underlying the action of the EMC in intestinal homeostasis maintenance under physiological and pathological conditions and provides new insight into the pathogenesis of tunicamycin-induced tumorigenesis.
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Affiliation(s)
- Lin Shi
- Laboratory of Stem Cell Biology, College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Hubing Ma
- Laboratory of Stem Cell Biology, College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Jinjun Wang
- Laboratory of Stem Cell Biology, College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Meifang Ma
- Laboratory of Stem Cell Biology, College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Hang Zhao
- Laboratory of Stem Cell Biology, College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Zhengran Li
- Laboratory of Stem Cell Biology, College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Jian-Hua Wang
- National Institute of Biological Sciences, Beijing 102206, China
| | - Shian Wu
- College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Zizhang Zhou
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an 271018, China
| | - Meng-Qiu Dong
- National Institute of Biological Sciences, Beijing 102206, China
| | - Zhouhua Li
- Laboratory of Stem Cell Biology, College of Life Sciences, Capital Normal University, Beijing 100048, China
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6
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Florin F, Bonneau B, Briseño-Roa L, Bessereau JL, Jospin M. Calcineurin-Dependent Homeostatic Response of C. elegans Muscle Cells upon Prolonged Activation of Acetylcholine Receptors. Cells 2023; 12:2201. [PMID: 37681933 PMCID: PMC10486475 DOI: 10.3390/cells12172201] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 08/29/2023] [Accepted: 08/30/2023] [Indexed: 09/09/2023] Open
Abstract
Pharmacological adaptation is a common phenomenon observed during prolonged drug exposure and often leads to drug resistance. Understanding the cellular events involved in adaptation could provide new strategies to circumvent this resistance issue. We used the nematode Caenorhabditis elegans to analyze the adaptation to levamisole, an ionotropic acetylcholine receptor agonist, used for decades to treat nematode parasitic infections. Genetic screens in C. elegans identified "adapting mutants" that initially paralyze upon exposure to levamisole as the wild type (WT), but recover locomotion after a few hours whereas WT remain paralyzed. Here, we show that levamisole induces a sustained increase in cytosolic calcium concentration in the muscle cells of adapting mutants, lasting several hours and preceding a decrease in levamisole-sensitive acetylcholine receptors (L-AChR) at the muscle plasma membrane. This decrease correlated with a drop in calcium concentration, a relaxation of the animal's body and a resumption of locomotion. The decrease in calcium and L-AChR content depends on calcineurin activation in muscle cells. We also showed that levamisole adaptation triggers homeostatic mechanisms in muscle cells including mitochondria remodeling, lysosomal tubulation and an increase in autophagic activity. Levamisole adaptation thus provides a new experimental paradigm for studying how cells cope with calcium stress.
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Affiliation(s)
- Franklin Florin
- Institut NeuroMyoGène, CNRS UMR-5284, INSERM U-1314, MeLiS, Université Lyon, Université Claude Bernard Lyon 1, F-69008 Lyon, France (B.B.); (J.-L.B.)
| | - Benjamin Bonneau
- Institut NeuroMyoGène, CNRS UMR-5284, INSERM U-1314, MeLiS, Université Lyon, Université Claude Bernard Lyon 1, F-69008 Lyon, France (B.B.); (J.-L.B.)
- Institut Curie, CNRS UMR3347, INSERM U1021, Université Paris-Saclay, F-91405 Orsay, France
| | - Luis Briseño-Roa
- Institut NeuroMyoGène, CNRS UMR-5284, INSERM U-1314, MeLiS, Université Lyon, Université Claude Bernard Lyon 1, F-69008 Lyon, France (B.B.); (J.-L.B.)
- Medetia Pharmaceuticals, Institut Imagine, F-75015 Paris, France
| | - Jean-Louis Bessereau
- Institut NeuroMyoGène, CNRS UMR-5284, INSERM U-1314, MeLiS, Université Lyon, Université Claude Bernard Lyon 1, F-69008 Lyon, France (B.B.); (J.-L.B.)
| | - Maëlle Jospin
- Institut NeuroMyoGène, CNRS UMR-5284, INSERM U-1314, MeLiS, Université Lyon, Université Claude Bernard Lyon 1, F-69008 Lyon, France (B.B.); (J.-L.B.)
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Li X, Jiang Z, Su Y, Wang K, Jiang X, Sun K, Yang Y, Zhou Y, Zhu X, Zhang L. Deletion of Emc1 in photoreceptor cells causes retinal degeneration in mice. FEBS J 2023; 290:4356-4370. [PMID: 37098815 DOI: 10.1111/febs.16807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 03/30/2023] [Accepted: 04/25/2023] [Indexed: 04/27/2023]
Abstract
The endoplasmic reticulum membrane protein complex (EMC) plays a critical role in the synthesis of multipass membrane proteins. Genetic studies indicated that mutations in EMC1 gene were associated with retinal degeneration diseases; however, the role of EMC1 in photoreceptor has not been confirmed. Here, we show that Emc1 ablation in the photoreceptor cells of mice recapitulated the retinitis pigmentosa phenotypes, including an attenuated scotopic electroretinogram response and the progressive degeneration of rod cells and cone cells. Histopathological examination of tissues from rod-specific Emc1 knockout mice revealed mislocalized rhodopsin and irregularly arranged cone cells at the age of 2 months. Further immunoblotting analysis revealed decreased levels of membrane proteins and endoplasmic reticulum chaperones in 1-month-old rod-specific Emc1 knockout mice retinae, and this led us to speculate that the loss of membrane proteins is the main cause of the degeneration of photoreceptors. EMC1 most likely regulated the membrane protein levels at an earlier step in the biosynthetic process before the proteins translocated into the endoplasmic reticulum. The present study demonstrates the essential roles of Emc1 in photoreceptor cells, and reveals the mechanism through which EMC1 mutations are linked to retinitis pigmentosa.
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Affiliation(s)
- Xiao Li
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Zhilin Jiang
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Yujing Su
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Kaifang Wang
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Xiaoyan Jiang
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Kuanxiang Sun
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Yeming Yang
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Yu Zhou
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Xianjun Zhu
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
- Key Laboratory of Tibetan Medicine Research, Chinese Academy of Sciences and Qinghai Provincial Key Laboratory of Tibetan Medicine Research, Northwest Institute of Plateau Biology, Xining, China
- Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, China
| | - Lin Zhang
- The Sichuan Provincial Key Laboratory for Human Disease Gene Study and Department of Laboratory Medicine, Center for Medical Genetics, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
- Key Laboratory of Tibetan Medicine Research, Chinese Academy of Sciences and Qinghai Provincial Key Laboratory of Tibetan Medicine Research, Northwest Institute of Plateau Biology, Xining, China
- Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, China
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8
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Marquez J, Aslam F, Khokha MK. Expanding EMC foldopathies: Topogenesis deficits alter the neural crest. Genesis 2023; 61:e23520. [PMID: 37318954 PMCID: PMC10524326 DOI: 10.1002/dvg.23520] [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: 06/23/2022] [Revised: 04/13/2023] [Accepted: 05/02/2023] [Indexed: 06/17/2023]
Abstract
The endoplasmic reticulum (ER) membrane protein complex (EMC) is essential for the insertion of a wide variety of transmembrane proteins into the plasma membrane across cell types. Each EMC is composed of Emc1-7, Emc10, and either Emc8 or Emc9. Recent human genetics studies have implicated variants in EMC genes as the basis for a group of human congenital diseases. The patient phenotypes are varied but appear to affect a subset of tissues more prominently than others. Namely, craniofacial development seems to be commonly affected. We previously developed an array of assays in Xenopus tropicalis to assess the effects of emc1 depletion on the neural crest, craniofacial cartilage, and neuromuscular function. We sought to extend this approach to additional EMC components identified in patients with congenital malformations. Through this approach, we determine that EMC9 and EMC10 are important for neural crest development and the development of craniofacial structures. The phenotypes observed in patients and our Xenopus model phenotypes similar to EMC1 loss of function likely due to a similar mechanism of dysfunction in transmembrane protein topogenesis.
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Affiliation(s)
- Jonathan Marquez
- Pediatric Genomics Discovery Program, Department of Pediatrics and Genetics, Yale University School of Medicine, New Haven, CT, USA
| | - Faiza Aslam
- Pediatric Genomics Discovery Program, Department of Pediatrics and Genetics, Yale University School of Medicine, New Haven, CT, USA
| | - Mustafa K. Khokha
- Pediatric Genomics Discovery Program, Department of Pediatrics and Genetics, Yale University School of Medicine, New Haven, CT, USA
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9
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Chen Z, Mondal A, Abderemane-Ali F, Jang S, Niranjan S, Montaño JL, Zaro BW, Minor DL. EMC chaperone-Ca V structure reveals an ion channel assembly intermediate. Nature 2023; 619:410-419. [PMID: 37196677 PMCID: PMC10896479 DOI: 10.1038/s41586-023-06175-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Accepted: 05/05/2023] [Indexed: 05/19/2023]
Abstract
Voltage-gated ion channels (VGICs) comprise multiple structural units, the assembly of which is required for function1,2. Structural understanding of how VGIC subunits assemble and whether chaperone proteins are required is lacking. High-voltage-activated calcium channels (CaVs)3,4 are paradigmatic multisubunit VGICs whose function and trafficking are powerfully shaped by interactions between pore-forming CaV1 or CaV2 CaVα1 (ref. 3), and the auxiliary CaVβ5 and CaVα2δ subunits6,7. Here we present cryo-electron microscopy structures of human brain and cardiac CaV1.2 bound with CaVβ3 to a chaperone-the endoplasmic reticulum membrane protein complex (EMC)8,9-and of the assembled CaV1.2-CaVβ3-CaVα2δ-1 channel. These structures provide a view of an EMC-client complex and define EMC sites-the transmembrane (TM) and cytoplasmic (Cyto) docks; interaction between these sites and the client channel causes partial extraction of a pore subunit and splays open the CaVα2δ-interaction site. The structures identify the CaVα2δ-binding site for gabapentinoid anti-pain and anti-anxiety drugs6, show that EMC and CaVα2δ interactions with the channel are mutually exclusive, and indicate that EMC-to-CaVα2δ hand-off involves a divalent ion-dependent step and CaV1.2 element ordering. Disruption of the EMC-CaV complex compromises CaV function, suggesting that the EMC functions as a channel holdase that facilitates channel assembly. Together, the structures reveal a CaV assembly intermediate and EMC client-binding sites that could have wide-ranging implications for the biogenesis of VGICs and other membrane proteins.
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Affiliation(s)
- Zhou Chen
- Cardiovascular Research Institute, University of California, San Francisco, CA, USA
| | - Abhisek Mondal
- Cardiovascular Research Institute, University of California, San Francisco, CA, USA
| | - Fayal Abderemane-Ali
- Cardiovascular Research Institute, University of California, San Francisco, CA, USA
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Seil Jang
- Cardiovascular Research Institute, University of California, San Francisco, CA, USA
| | - Sangeeta Niranjan
- Cardiovascular Research Institute, University of California, San Francisco, CA, USA
| | - José L Montaño
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
| | - Balyn W Zaro
- Cardiovascular Research Institute, University of California, San Francisco, CA, USA
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
| | - Daniel L Minor
- Cardiovascular Research Institute, University of California, San Francisco, CA, USA.
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA.
- California Institute for Quantitative Biomedical Research, University of California, San Francisco, CA, USA.
- Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, CA, USA.
- Molecular Biophysics and Integrated Bio-imaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA, USA.
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10
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Liu N, Huang M, Liang X, Cao M, Lun Z, Zhang Y, Yang J, Bhadauria V, Zhao W, Yan J, Peng YL, Lu X. Magnaporthe oryzae endoplasmic reticulum membrane complex regulates the biogenesis of membrane proteins for pathogenicity. THE NEW PHYTOLOGIST 2023; 238:1163-1181. [PMID: 36772852 DOI: 10.1111/nph.18810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Accepted: 02/03/2023] [Indexed: 06/18/2023]
Abstract
In eukaryotes, the majority of newly synthesized integral membrane proteins are inserted into the endoplasmic reticulum (ER) membrane before transferred to their functional sites. The conserved ER membrane complex (EMC) takes part in the insertion process for tail-anchored membrane proteins. However, the function of EMC in phytopathogenic fungi has not been characterized. Here, we report the identification and functional characterization of two EMC subunits MoEmc5 and MoEmc2 in Magnaporthe oryzae. The knockout mutants ΔMoemc5 and ΔMoemc2 exhibit substantial defect in autophagy, pathogenicity, cell wall integrity, and magnesium ion sensitivity. We demonstrate that the autophagy process was severely impaired in the ΔMoemc5 and ΔMoemc2 mutants because of the low-protein steady-state level of Atg9, the sole membrane-associated autophagy protein. Furthermore, the protein level of membrane proteins Chs4, Fks1, and MoMnr2 is also significantly reduced in the ΔMoemc5 and ΔMoemc2 strains, leading to their supersensitivity to Calcofluor white, Congo red, and magnesium. In addition, MoEmc5, but not MoEmc2, acts as a magnesium transporter independent of its EMC function. Magnaporthe oryzae EMC regulates the biogenesis of membrane proteins for autophagy and virulence; therefore, EMC subunits could be potential targets for fungicide design in the future.
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Affiliation(s)
- Ning Liu
- State Key Laboratory of Agrobiotechnology and MOA Key Laboratory of Pest Monitoring and Green Management, China Agricultural University, Beijing, 100193, China
- Beijing Key Laboratory of Environment Friendly Management on Fruit Diseases and Pests in North China, Institute of Plant Protection, Beijing Academy of Agriculture and Forestry Sciences, Beijing, 100097, China
| | - Manna Huang
- State Key Laboratory of Agrobiotechnology and MOA Key Laboratory of Pest Monitoring and Green Management, China Agricultural University, Beijing, 100193, China
| | - Xinyuan Liang
- State Key Laboratory of Agrobiotechnology and MOA Key Laboratory of Pest Monitoring and Green Management, China Agricultural University, Beijing, 100193, China
| | - Miao Cao
- State Key Laboratory of Agrobiotechnology and MOA Key Laboratory of Pest Monitoring and Green Management, China Agricultural University, Beijing, 100193, China
| | - Zhiqin Lun
- State Key Laboratory of Agrobiotechnology and MOA Key Laboratory of Pest Monitoring and Green Management, China Agricultural University, Beijing, 100193, China
| | - Yan Zhang
- State Key Laboratory of Agrobiotechnology and MOA Key Laboratory of Pest Monitoring and Green Management, China Agricultural University, Beijing, 100193, China
| | - Jun Yang
- State Key Laboratory of Agrobiotechnology and MOA Key Laboratory of Pest Monitoring and Green Management, China Agricultural University, Beijing, 100193, China
| | - Vijai Bhadauria
- State Key Laboratory of Agrobiotechnology and MOA Key Laboratory of Pest Monitoring and Green Management, China Agricultural University, Beijing, 100193, China
| | - Wensheng Zhao
- State Key Laboratory of Agrobiotechnology and MOA Key Laboratory of Pest Monitoring and Green Management, China Agricultural University, Beijing, 100193, China
| | - Jiye Yan
- Beijing Key Laboratory of Environment Friendly Management on Fruit Diseases and Pests in North China, Institute of Plant Protection, Beijing Academy of Agriculture and Forestry Sciences, Beijing, 100097, China
| | - You-Liang Peng
- State Key Laboratory of Agrobiotechnology and MOA Key Laboratory of Pest Monitoring and Green Management, China Agricultural University, Beijing, 100193, China
| | - Xunli Lu
- State Key Laboratory of Agrobiotechnology and MOA Key Laboratory of Pest Monitoring and Green Management, China Agricultural University, Beijing, 100193, China
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11
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Bai L, Li H. Structural insights into the membrane chaperones for multi-pass membrane protein biogenesis. Curr Opin Struct Biol 2023; 79:102563. [PMID: 36863267 DOI: 10.1016/j.sbi.2023.102563] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2022] [Revised: 01/22/2023] [Accepted: 01/28/2023] [Indexed: 03/04/2023]
Abstract
Certain transmembrane α-helices of multi-pass membrane proteins line substrate transport paths or catalytic pockets and, therefore, are partially hydrophilic. Sec61 alone is insufficient to insert these less hydrophobic segments into the membrane and needs to work with dedicated membrane chaperones. Three such membrane chaperones have been described in the literature-the endoplasmic reticulum membrane protein complex (EMC), the TMCO1 complex, and the PAT complex. Recent structural studies on these membrane chaperones have revealed their overall architecture, multi-subunit assembly, putative substrate transmembrane helix-binding pockets, and cooperative mechanisms with the ribosome and Sec61 translocon. These structures are providing initial insights into the poorly understood processes of multi-pass membrane protein biogenesis.
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Affiliation(s)
- Lin Bai
- Department of Biochemistry and Biophysics, School of Basic Medical Sciences, Peking University, Beijing, 100083, China.
| | - Huilin Li
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, 49503, United States.
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12
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Crespo-Piazuelo D, Acloque H, González-Rodríguez O, Mongellaz M, Mercat MJ, Bink MCAM, Huisman AE, Ramayo-Caldas Y, Sánchez JP, Ballester M. Identification of transcriptional regulatory variants in pig duodenum, liver, and muscle tissues. Gigascience 2022; 12:giad042. [PMID: 37354463 PMCID: PMC10290502 DOI: 10.1093/gigascience/giad042] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 04/13/2023] [Accepted: 05/25/2023] [Indexed: 06/26/2023] Open
Abstract
BACKGROUND In humans and livestock species, genome-wide association studies (GWAS) have been applied to study the association between variants distributed across the genome and a phenotype of interest. To discover genetic polymorphisms affecting the duodenum, liver, and muscle transcriptomes of 300 pigs from 3 different breeds (Duroc, Landrace, and Large White), we performed expression GWAS between 25,315,878 polymorphisms and the expression of 13,891 genes in duodenum, 12,748 genes in liver, and 11,617 genes in muscle. RESULTS More than 9.68 × 1011 association tests were performed, yielding 14,096,080 significantly associated variants, which were grouped in 26,414 expression quantitative trait locus (eQTL) regions. Over 56% of the variants were within 1 Mb of their associated gene. In addition to the 100-kb region upstream of the transcription start site, we identified the importance of the 100-kb region downstream of the 3'UTR for gene regulation, as most of the cis-regulatory variants were located within these 2 regions. We also observed 39,874 hotspot regulatory polymorphisms associated with the expression of 10 or more genes that could modify the protein structure or the expression of a regulator gene. In addition, 2 motifs (5'-GATCCNGYGTTGCYG-3' and a poly(A) sequence) were enriched across the 3 tissues within the neighboring sequences of the most significant single-nucleotide polymorphisms in each cis-eQTL region. CONCLUSIONS The 14 million significant associations obtained in this study are publicly available and have enabled the identification of expression-associated cis-, trans-, and hotspot regulatory variants within and across tissues, thus shedding light on the molecular mechanisms of regulatory variations that shape end-trait phenotypes.
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Affiliation(s)
- Daniel Crespo-Piazuelo
- Animal Breeding and Genetics Program, IRTA, Torre Marimon, Caldes de Montbui (08140), Spain
| | - Hervé Acloque
- GABI, Université Paris-Saclay, INRAE, AgroParisTech, Jouy-en-Josas (78350), France
| | | | - Mayrone Mongellaz
- GABI, Université Paris-Saclay, INRAE, AgroParisTech, Jouy-en-Josas (78350), France
| | | | - Marco C A M Bink
- Hendrix Genetics Research Technology & Services B.V., Boxmeer (5830 AC), The Netherlands
| | | | - Yuliaxis Ramayo-Caldas
- Animal Breeding and Genetics Program, IRTA, Torre Marimon, Caldes de Montbui (08140), Spain
| | - Juan Pablo Sánchez
- Animal Breeding and Genetics Program, IRTA, Torre Marimon, Caldes de Montbui (08140), Spain
| | - Maria Ballester
- Animal Breeding and Genetics Program, IRTA, Torre Marimon, Caldes de Montbui (08140), Spain
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13
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Murphy A, Vyavahare S, Kumar S, Lee TJ, Sharma A, Adusumilli S, Hamrick M, Isales CM, Fulzele S. Dietary interventions and molecular mechanisms for healthy musculoskeletal aging. Biogerontology 2022; 23:681-698. [PMID: 35727468 DOI: 10.1007/s10522-022-09970-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Accepted: 05/18/2022] [Indexed: 12/13/2022]
Abstract
Over the past decade, extensive efforts have focused on understanding age-associated diseases and how to prolong a healthy lifespan. The induction of dietary protocols such as caloric restriction (CR) and protein restriction (PR) has positively affected a healthy lifespan. These intervention ideas (nutritional protocols) have been the subject of human cohort studies and clinical trials to evaluate their effectiveness in alleviating age-related diseases (such as type II diabetes, cardiovascular disease, obesity, and musculoskeletal fragility) and promoting human longevity. This study summarizes the literature on the nutritional protocols, emphasizing their impacts on bone and muscle biology. In addition, we analyzed several CR studies using Gene Expression Omnibus (GEO) database and identified common transcriptome changes to understand the signaling pathway involved in musculoskeletal tissue. We identified nine novel common genes, out of which five were upregulated (Emc3, Fam134b, Fbxo30, Pip5k1a, and Retsat), and four were downregulated (Gstm2, Per2, Fam78a, and Sel1l3) with CR in muscles. Gene Ontology enrichment analysis revealed that CR regulates several signaling pathways (e.g., circadian gene regulation and rhythm, energy reserve metabolic process, thermogenesis) involved in energy metabolism. In conclusion, this study summarizes the beneficiary role of CR and identifies novel genes and signaling pathways involved in musculoskeletal biology.
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Affiliation(s)
- Andrew Murphy
- Department of Medicine, Augusta University, Augusta, GA, 30912, USA
| | - Sagar Vyavahare
- Department of Cell Biology and Anatomy, Augusta University, Augusta, GA, USA
| | - Sandeep Kumar
- Department of Cell Biology and Anatomy, Augusta University, Augusta, GA, USA
| | - Tae Jin Lee
- Center for Biotechnology and Genomic Medicine, Augusta University, Augusta, GA, 30912, USA
| | - Ashok Sharma
- Center for Biotechnology and Genomic Medicine, Augusta University, Augusta, GA, 30912, USA
| | | | - Mark Hamrick
- Department of Cell Biology and Anatomy, Augusta University, Augusta, GA, USA.,Center for Healthy Aging, Augusta University, Augusta, GA, USA
| | - Carlos M Isales
- Department of Medicine, Augusta University, Augusta, GA, 30912, USA.,Center for Healthy Aging, Augusta University, Augusta, GA, USA
| | - Sadanand Fulzele
- Department of Medicine, Augusta University, Augusta, GA, 30912, USA. .,Department of Cell Biology and Anatomy, Augusta University, Augusta, GA, USA. .,Center for Healthy Aging, Augusta University, Augusta, GA, USA.
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14
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Reconstitution of an N-AChR from Brugia malayi an evolved change in acetylcholine receptor accessory protein requirements in filarial parasites. PLoS Pathog 2022; 18:e1010962. [DOI: 10.1371/journal.ppat.1010962] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Revised: 12/01/2022] [Accepted: 10/29/2022] [Indexed: 11/15/2022] Open
Abstract
Neurotransmission is an important target for anthelmintic drugs, where receptor characteristics and response can be examined through reconstitution ex vivo in Xenopus laevis oocytes. The homomeric ACR-16 nicotine sensitive acetylcholine receptors (N-AChRs) of several helminth species have been characterized in this way. Our efforts to reconstitute the N-AChR from the clade III filarial parasite, Brugia malayi using similar conditions, initially produced no detectable response. A robust response to acetylcholine is obtained from the closely related clade III parasite Ascaris suum, suggesting that specific changes have occurred between Ascaris and Brugia. N-AChRs from three species intermediate between A. suum and B. malayi were characterized to provide information on the cause. Maximal response to acetylcholine did not change abruptly, consistent with a discrete event, but rather decreased progressively from A. suum through Dracunculus medinensis, Gonglylonema pulchrum and Thelazia callipaeda. Receptor responses to the characteristic nicotine, and other agonists were generally similar. The decrease in maximal current did correlate with a delayed time to reach larger response. Together, this suggested that the failure to reconstitute the B. malayi N-AChR was one extreme of a progressive decrease and that an issue with synthesis of the receptor in oocytes was responsible. Addition of accessory proteins EMC-6, NRA-2 and NRA-4, in addition to RIC-3, produced a small, but measurable B. malayi N-AChR response. Pharmacological properties of a chimeric B. malayi N-AChR were equivalent to the other species, confirming the receptor response remains unchanged while its production is increasingly dependent on accessory proteins. One possibility is that loss of many subunits for acetylcholine receptors from the filarial nematode genome is linked to new subunit combinations that lead to such a dependence. This novel phylogenetic approach allowed the first characterization of a B. malayi AChR ex vivo and in doing so, provides a framework for the successful characterization of other receptors that have yet to be reconstituted.
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15
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O'Keefe S, Pool MR, High S. Membrane protein biogenesis at the ER: the highways and byways. FEBS J 2022; 289:6835-6862. [PMID: 33960686 DOI: 10.1111/febs.15905] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 04/19/2021] [Accepted: 04/28/2021] [Indexed: 01/13/2023]
Abstract
The Sec61 complex is the major protein translocation channel of the endoplasmic reticulum (ER), where it plays a central role in the biogenesis of membrane and secretory proteins. Whilst Sec61-mediated protein translocation is typically coupled to polypeptide synthesis, suggestive of significant complexity, an obvious characteristic of this core translocation machinery is its surprising simplicity. Over thirty years after its initial discovery, we now understand that the Sec61 complex is in fact the central piece of an elaborate jigsaw puzzle, which can be partly solved using new research findings. We propose that the Sec61 complex acts as a dynamic hub for co-translational protein translocation at the ER, proactively recruiting a range of accessory complexes that enhance and regulate its function in response to different protein clients. It is now clear that the Sec61 complex does not have a monopoly on co-translational insertion, with some transmembrane proteins preferentially utilising the ER membrane complex instead. We also have a better understanding of post-insertion events, where at least one membrane-embedded chaperone complex can capture the newly inserted transmembrane domains of multi-span proteins and co-ordinate their assembly into a native structure. Having discovered this array of Sec61-associated components and competitors, our next challenge is to understand how they act together in order to expand the range and complexity of the membrane proteins that can be synthesised at the ER. Furthermore, this diversity of components and pathways may open up new opportunities for targeted therapeutic interventions designed to selectively modulate protein biogenesis at the ER.
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Affiliation(s)
- Sarah O'Keefe
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, UK
| | - Martin R Pool
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, UK
| | - Stephen High
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, UK
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16
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Whittsette AL, Wang YJ, Mu TW. The endoplasmic reticulum membrane complex promotes proteostasis of GABA A receptors. iScience 2022; 25:104754. [PMID: 35938049 PMCID: PMC9352529 DOI: 10.1016/j.isci.2022.104754] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 06/30/2022] [Accepted: 07/07/2022] [Indexed: 11/29/2022] Open
Abstract
The endoplasmic reticulum membrane complex (EMC) plays a critical role in the biogenesis of tail-anchored proteins and a subset of multi-pass membrane proteins in the endoplasmic reticulum (ER). However, because of nearly exclusive expression of neurotransmitter-gated ion channels in the central nervous system (CNS), the role of the EMC in their biogenesis is not well understood. In this study, we demonstrated that the EMC positively regulates the surface trafficking and thus function of endogenous γ-aminobutyric acid type A (GABAA) receptors, the primary inhibitory ion channels in the mammalian brain. Moreover, among ten EMC subunits, EMC3 and EMC6 have the most prominent effect, and overexpression of EMC3 or EMC6 is sufficient to restore the function of epilepsy-associated GABAA receptor variants. In addition, EMC3 and EMC6 demonstrate endogenous interactions with major neuroreceptors, which depends on their transmembrane domains, suggesting a general role of the EMC in the biogenesis of neuroreceptors.
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Affiliation(s)
- Angela L. Whittsette
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106, USA
| | - Ya-Juan Wang
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106, USA
| | - Ting-Wei Mu
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106, USA
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17
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An extracellular scaffolding complex confers unusual rectification upon an ionotropic acetylcholine receptor in C. elegans. Proc Natl Acad Sci U S A 2022; 119:e2113545119. [PMID: 35858330 PMCID: PMC9304021 DOI: 10.1073/pnas.2113545119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Biophysical properties of ligand-gated receptors can be profoundly modified by auxiliary subunits or by the lipid microenvironment of the membrane. Hence, it is sometimes challenging to relate the properties of receptors reconstituted in heterologous expression systems to those of their native counterparts. Here we show that the properties of Caenorhabditis elegans levamisole-sensitive acetylcholine receptors (L-AChRs), the ionotropic acetylcholine receptors targeted by the cholinergic anthelmintic levamisole at neuromuscular junctions, can be profoundly modified by their clustering machinery. We uncovered that L-AChRs exhibit a strong outward rectification in vivo, which was not previously described in heterologous systems. This unusual feature for an ionotropic AChR is abolished by disrupting the interaction of the receptors with the extracellular complex required for their synaptic clustering. When recorded at -60 mV, levamisole-induced currents are similar in the wild type and in L-AChR-clustering-defective mutants, while they are halved in these mutants at more depolarized physiological membrane potentials. Consequently, levamisole causes a strong muscle depolarization in the wild type, which leads to complete inactivation of the voltage-gated calcium channels and to an irreversible flaccid paralysis. In mutants defective for L-AChR clustering, the levamisole-induced depolarization is weaker, allowing voltage-gated calcium channels to remain partially active, which eventually leads to adaptation and survival of the worms. This explains why historical screens for C. elegans mutants resistant to levamisole identified the components of the L-AChR clustering machinery, in addition to proteins required for receptor biosynthesis or efficacy. This work further emphasizes the importance of pursuing ligand-gated channel characterization in their native environment.
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18
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Khan S. Endoplasmic Reticulum in Metaplasticity: From Information Processing to Synaptic Proteostasis. Mol Neurobiol 2022; 59:5630-5655. [PMID: 35739409 DOI: 10.1007/s12035-022-02916-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 06/05/2022] [Indexed: 11/29/2022]
Abstract
The ER (endoplasmic reticulum) is a Ca2+ reservoir and the unique protein-synthesizing machinery which is distributed throughout the neuron and composed of multiple different structural domains. One such domain is called EMC (endoplasmic reticulum membrane protein complex), pleiotropic nature in cellular functions. The ER/EMC position inside the neurons unmasks its contribution to synaptic plasticity via regulating various cellular processes from protein synthesis to Ca2+ signaling. Since presynaptic Ca2+ channels and postsynaptic ionotropic receptors are organized into the nanodomains, thus ER can be a crucial player in establishing TMNCs (transsynaptic molecular nanocolumns) to shape efficient neural communications. This review hypothesized that ER is not only involved in stress-mediated neurodegeneration but also axon regrowth, remyelination, neurotransmitter switching, information processing, and regulation of pre- and post-synaptic functions. Thus ER might not only be a protein-synthesizing and quality control machinery but also orchestrates plasticity of plasticity (metaplasticity) within the neuron to execute higher-order brain functions and neural repair.
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Affiliation(s)
- Shumsuzzaman Khan
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA.
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19
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Chung HL, Rump P, Lu D, Glassford MR, Mok JW, Fatih J, Basal A, Marcogliese PC, Kanca O, Rapp M, Fock JM, Kamsteeg EJ, Lupski JR, Larson A, Haninbal MC, Bellen H, Harel T. De novo variants in EMC1 lead to neurodevelopmental delay and cerebellar degeneration and affect glial function in Drosophila. Hum Mol Genet 2022; 31:3231-3244. [PMID: 35234901 PMCID: PMC9523557 DOI: 10.1093/hmg/ddac053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 02/22/2022] [Accepted: 02/23/2022] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND The endoplasmic reticulum (ER)-membrane protein complex (EMC) is a multi-protein transmembrane complex composed of 10 subunits that functions as a membrane-protein chaperone. Variants in EMC1 lead to neurodevelopmental delay and cerebellar degeneration. Multiple families with biallelic variants have been published, yet to date, only a single report of a monoallelic variant has been described, and functional evidence is sparse. METHODS Exome sequencing was used to investigate the genetic cause underlying severe developmental delay in three unrelated children. EMC1 variants were modeled in Drosophila, using loss-of-function (LoF) and overexpression studies. Glial-specific and neuronal-specific assays were used to determine whether the dysfunction was specific to one cell type. RESULTS Exome sequencing identified de novo variants in EMC1 in three individuals affected by global developmental delay, hypotonia, seizures, visual impairment and cerebellar atrophy. All variants were located at Pro582 or Pro584. Drosophila studies indicated that imbalance of EMC1-either overexpression or knockdown-results in pupal lethality and suggest that the tested homologous variants are LoF alleles. In addition, glia-specific gene dosage, overexpression or knockdown, of EMC1 led to lethality, whereas neuron-specific alterations were tolerated. DISCUSSION We establish de novo monoallelic EMC1 variants as causative of a neurological disease trait by providing functional evidence in a Drosophila model. The identified variants failed to rescue the lethality of a null allele. Variations in dosage of the wild-type EMC1, specifically in glia, lead to pupal lethality, which we hypothesize results from the altered stoichiometry of the multi-subunit protein complex EMC.
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Affiliation(s)
- Hyung-Lok Chung
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA,Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX 77030, USA,Howard Hughes Medical Institute, Baylor College of Medicine, Houston, TX 77030, USA
| | - Patrick Rump
- University of Groningen, University Medical Centre Groningen, Department of Genetics, Groningen 9700 RB, The Netherlands
| | - Di Lu
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA,Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX 77030, USA
| | - Megan R Glassford
- Division of Pediatric Genetics, Metabolism & Genomic Medicine, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Jung-Wan Mok
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA,Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX 77030, USA
| | - Jawid Fatih
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Adily Basal
- Department of Genetics, Hadassah Medical Organization, Jerusalem 9112001, Israel
| | - Paul C Marcogliese
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA,Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX 77030, USA
| | - Oguz Kanca
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA,Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX 77030, USA
| | - Michele Rapp
- University of Colorado Anschutz Medical Campus, Aurora, CO 60045, USA
| | - Johanna M Fock
- University of Groningen, University Medical Centre Groningen, Department of Neurology, Groningen 9700 RB, The Netherlands
| | - Erik-Jan Kamsteeg
- Department of Human Genetics, Radboud University Medical Centre, Nijmegen 6500 HB, The Netherlands
| | - James R Lupski
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA,Human Genome Sequencing Center, Baylor College of Medicine, Houston, TX 77030, USA,Department of Pediatrics, Texas Children's Hospital, Houston, TX 77030, USA
| | - Austin Larson
- University of Colorado School of Medicine and Children's Hospital Colorado, Aurora, CO 60045, United States
| | - Mark C Haninbal
- Division of Pediatric Genetics, Metabolism & Genomic Medicine, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Hugo Bellen
- To whom correspondence should be addressed at: Department of Genetics, Hadassah-Hebrew University Medical Center, POB 12000, Jerusalem 9112001, Israel. Tel: +(972)-2-6776329; Fax: +(972)-2-6777618; ; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA. Tel: +1 832824-8750; Fax: +1832825-1240;
| | - Tamar Harel
- To whom correspondence should be addressed at: Department of Genetics, Hadassah-Hebrew University Medical Center, POB 12000, Jerusalem 9112001, Israel. Tel: +(972)-2-6776329; Fax: +(972)-2-6777618; ; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA. Tel: +1 832824-8750; Fax: +1832825-1240;
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20
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Abstract
The endoplasmic reticulum (ER) is the site of membrane protein insertion, folding, and assembly in eukaryotes. Over the past few years, a combination of genetic and biochemical studies have implicated an abundant factor termed the ER membrane protein complex (EMC) in several aspects of membrane protein biogenesis. This large nine-protein complex is built around a deeply conserved core formed by the EMC3-EMC6 subcomplex. EMC3 belongs to the universally conserved Oxa1 superfamily of membrane protein transporters, whereas EMC6 is an ancient, widely conserved obligate partner. EMC has an established role in the insertion of transmembrane domains (TMDs) and less understood roles during the later steps of membrane protein folding and assembly. Several recent structures suggest hypotheses about the mechanism(s) of TMD insertion by EMC, with various biochemical and proteomics studies beginning to reveal the range of EMC's membrane protein substrates. Expected final online publication date for the Annual Review of Biochemistry, Volume 91 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Ramanujan S Hegde
- Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom;
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21
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Hegde RS, Keenan RJ. The mechanisms of integral membrane protein biogenesis. Nat Rev Mol Cell Biol 2022; 23:107-124. [PMID: 34556847 DOI: 10.1038/s41580-021-00413-2] [Citation(s) in RCA: 84] [Impact Index Per Article: 42.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/06/2021] [Indexed: 02/08/2023]
Abstract
Roughly one quarter of all genes code for integral membrane proteins that are inserted into the plasma membrane of prokaryotes or the endoplasmic reticulum membrane of eukaryotes. Multiple pathways are used for the targeting and insertion of membrane proteins on the basis of their topological and biophysical characteristics. Multipass membrane proteins span the membrane multiple times and face the additional challenges of intramembrane folding. In many cases, integral membrane proteins require assembly with other proteins to form multi-subunit membrane protein complexes. Recent biochemical and structural analyses have provided considerable clarity regarding the molecular basis of membrane protein targeting and insertion, with tantalizing new insights into the poorly understood processes of multipass membrane protein biogenesis and multi-subunit protein complex assembly.
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Affiliation(s)
- Ramanujan S Hegde
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, UK.
| | - Robert J Keenan
- Gordon Center for Integrative Science, The University of Chicago, Chicago, IL, USA.
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22
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Gaspar CJ, Vieira LC, Santos CC, Christianson JC, Jakubec D, Strisovsky K, Adrain C, Domingos PM. EMC is required for biogenesis of Xport-A, an essential chaperone of Rhodopsin-1 and the TRP channel. EMBO Rep 2022; 23:e53210. [PMID: 34918864 PMCID: PMC8728618 DOI: 10.15252/embr.202153210] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 10/26/2021] [Accepted: 11/10/2021] [Indexed: 01/07/2023] Open
Abstract
The ER membrane protein complex (EMC) is required for the biogenesis of a subset of tail anchored (TA) and polytopic membrane proteins, including Rhodopsin-1 (Rh1) and the TRP channel. To understand the physiological implications of EMC-dependent membrane protein biogenesis, we perform a bioinformatic identification of Drosophila TA proteins. From 254 predicted TA proteins, screening in larval eye discs identified two proteins that require EMC for their biogenesis: fan and Xport-A. Fan is required for male fertility in Drosophila and we show that EMC is also required for this process. Xport-A is essential for the biogenesis of both Rh1 and TRP, raising the possibility that disruption of Rh1 and TRP biogenesis in EMC mutants is secondary to the Xport-A defect. We show that EMC is required for Xport-A TMD membrane insertion and that EMC-independent Xport-A mutants rescue Rh1 and TRP biogenesis in EMC mutants. Finally, our work also reveals a role for Xport-A in a glycosylation-dependent triage mechanism during Rh1 biogenesis in the endoplasmic reticulum.
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Affiliation(s)
- Catarina J Gaspar
- Instituto de Tecnologia Química e Biológica da Universidade Nova de Lisboa (ITQB‐NOVA)OeirasPortugal
- Membrane Traffic LabInstituto Gulbenkian de Ciência (IGC)OeirasPortugal
| | - Lígia C Vieira
- Instituto de Tecnologia Química e Biológica da Universidade Nova de Lisboa (ITQB‐NOVA)OeirasPortugal
- Present address:
Center for Genomics and Systems BiologyNew York University Abu DhabiAbu DhabiUnited Arab Emirates
| | - Cristiana C Santos
- Instituto de Tecnologia Química e Biológica da Universidade Nova de Lisboa (ITQB‐NOVA)OeirasPortugal
| | - John C Christianson
- Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal SciencesBotnar Research CentreUniversity of OxfordOxfordUK
| | - David Jakubec
- Institute of Organic Chemistry and BiochemistryCzech Academy of SciencesPragueCzech Republic
| | - Kvido Strisovsky
- Institute of Organic Chemistry and BiochemistryCzech Academy of SciencesPragueCzech Republic
| | - Colin Adrain
- Membrane Traffic LabInstituto Gulbenkian de Ciência (IGC)OeirasPortugal
- Patrick G Johnston Centre for Cancer ResearchQueen’s UniversityBelfastUK
| | - Pedro M Domingos
- Instituto de Tecnologia Química e Biológica da Universidade Nova de Lisboa (ITQB‐NOVA)OeirasPortugal
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23
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Bai L, Li H. Cryo-EM structures of the endoplasmic reticulum membrane complex. FEBS J 2022; 289:102-112. [PMID: 33629497 PMCID: PMC8382784 DOI: 10.1111/febs.15786] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 02/13/2021] [Accepted: 02/23/2021] [Indexed: 01/03/2023]
Abstract
The transmembrane α-helices of membrane proteins are in general highly hydrophobic, and they enter the lipid bilayer through a lateral gate in the Sec61 translocon. However, some transmembrane α-helices are less hydrophobic and form membrane channels or substrate-binding pockets. Insertion of these amphipathic transmembrane α-helices into the membrane requires the specific membrane-embedded insertase called the endoplasmic reticulum membrane complex (EMC), which is a multi-subunit chaperone distinct from the GET insertase complex. Four recent cryo-electron microscopy studies on the eukaryotic EMC have revealed their remarkable architectural conservation from yeast to humans; a general consensus on the substrate transmembrane helix-binding pocket; and the evolutionary link to the prokaryotic insertases of the tail-anchored membrane proteins. These structures provide a solid framework for future mechanistic investigation.
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Affiliation(s)
- Lin Bai
- Department of Biochemistry and Biophysics, School of Basic Medical Sciences, Peking University, Beijing 100083, China
| | - Huilin Li
- Department of Structural Biology, Van Andel Institute, Grand Rapids, Michigan 49503, United States
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24
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Tirincsi A, Sicking M, Hadzibeganovic D, Haßdenteufel S, Lang S. The Molecular Biodiversity of Protein Targeting and Protein Transport Related to the Endoplasmic Reticulum. Int J Mol Sci 2021; 23:143. [PMID: 35008565 PMCID: PMC8745461 DOI: 10.3390/ijms23010143] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 12/19/2021] [Accepted: 12/20/2021] [Indexed: 12/15/2022] Open
Abstract
Looking at the variety of the thousands of different polypeptides that have been focused on in the research on the endoplasmic reticulum from the last five decades taught us one humble lesson: no one size fits all. Cells use an impressive array of components to enable the safe transport of protein cargo from the cytosolic ribosomes to the endoplasmic reticulum. Safety during the transit is warranted by the interplay of cytosolic chaperones, membrane receptors, and protein translocases that together form functional networks and serve as protein targeting and translocation routes. While two targeting routes to the endoplasmic reticulum, SRP (signal recognition particle) and GET (guided entry of tail-anchored proteins), prefer targeting determinants at the N- and C-terminus of the cargo polypeptide, respectively, the recently discovered SND (SRP-independent) route seems to preferentially cater for cargos with non-generic targeting signals that are less hydrophobic or more distant from the termini. With an emphasis on targeting routes and protein translocases, we will discuss those functional networks that drive efficient protein topogenesis and shed light on their redundant and dynamic nature in health and disease.
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Affiliation(s)
- Andrea Tirincsi
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (A.T.); (M.S.); (D.H.)
| | - Mark Sicking
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (A.T.); (M.S.); (D.H.)
| | - Drazena Hadzibeganovic
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (A.T.); (M.S.); (D.H.)
| | - Sarah Haßdenteufel
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Sven Lang
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (A.T.); (M.S.); (D.H.)
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25
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O’Keefe S, Zong G, Duah KB, Andrews LE, Shi WQ, High S. An alternative pathway for membrane protein biogenesis at the endoplasmic reticulum. Commun Biol 2021; 4:828. [PMID: 34211117 PMCID: PMC8249459 DOI: 10.1038/s42003-021-02363-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Accepted: 06/17/2021] [Indexed: 02/06/2023] Open
Abstract
The heterotrimeric Sec61 complex is a major site for the biogenesis of transmembrane proteins (TMPs), accepting nascent TMP precursors that are targeted to the endoplasmic reticulum (ER) by the signal recognition particle (SRP). Unlike most single-spanning membrane proteins, the integration of type III TMPs is completely resistant to small molecule inhibitors of the Sec61 translocon. Using siRNA-mediated depletion of specific ER components, in combination with the potent Sec61 inhibitor ipomoeassin F (Ipom-F), we show that type III TMPs utilise a distinct pathway for membrane integration at the ER. Hence, following SRP-mediated delivery to the ER, type III TMPs can uniquely access the membrane insertase activity of the ER membrane complex (EMC) via a mechanism that is facilitated by the Sec61 translocon. This alternative EMC-mediated insertion pathway allows type III TMPs to bypass the Ipom-F-mediated blockade of membrane integration that is seen with obligate Sec61 clients.
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Affiliation(s)
- Sarah O’Keefe
- grid.5379.80000000121662407School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Guanghui Zong
- grid.164295.d0000 0001 0941 7177Department of Chemistry and Biochemistry, University of Maryland, College Park, MD USA
| | - Kwabena B. Duah
- grid.252754.30000 0001 2111 9017Department of Chemistry, Ball State University, Muncie, IN USA
| | - Lauren E. Andrews
- grid.252754.30000 0001 2111 9017Department of Chemistry, Ball State University, Muncie, IN USA
| | - Wei Q. Shi
- grid.252754.30000 0001 2111 9017Department of Chemistry, Ball State University, Muncie, IN USA
| | - Stephen High
- grid.5379.80000000121662407School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
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26
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The ER membrane protein complex subunit Emc3 controls angiogenesis via the FZD4/WNT signaling axis. SCIENCE CHINA-LIFE SCIENCES 2021; 64:1868-1883. [PMID: 34128175 DOI: 10.1007/s11427-021-1941-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 04/29/2021] [Indexed: 02/08/2023]
Abstract
The endoplasmic reticulum (ER) membrane protein complex (EMC) regulates the synthesis and quality control of membrane proteins with multiple transmembrane domains. One of the membrane spanning subunits, EMC3, is a core member of the EMC complex that provides essential hydrophilic vestibule for substrate insertion. Here, we show that the EMC subunit Emc3 plays critical roles in the retinal vascular angiogenesis by regulating Norrin/Wnt signaling. Postnatal endothelial cell (EC)-specific deletion of Emc3 led to retarded retinal vascular development with a hyperpruned vascular network, the appearance of blunt-ended, aneurysm-like tip endothelial cells (ECs) with reduced numbers of filopodia and leakage of erythrocytes at the vascular front. Diminished tube formation and cell proliferation were also observed in EMC3 depleted human retinal endothelial cells (HRECs). We then discovered a critical role for EMC3 in expression of FZD4 receptor of β-catenin signaling using RNA sequencing, real-time quantitative PCR (RT-qPCR) and luciferase reporter assay. Moreover, augmentation of Wnt activity via lithium chloride (LiCl) treatment remarkably enhanced β-catenin signaling and cell proliferation of HRECs. Additionally, LiCl partially reversed the angiogenesis defects in Emc3-cKO mice. Our data reveal that Emc3 plays essential roles in angiogenesis through direct control of FZD4 expression and Norrin/β-catenin signaling.
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27
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Kawata K, Baba A, Shiota M, Wanibuchi H, Baba Y. ER membrane protein complex 1 interacts with STIM1 and regulates store-operated Ca2+ entry. J Biochem 2021; 170:483-488. [PMID: 34015095 DOI: 10.1093/jb/mvab063] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Accepted: 05/14/2021] [Indexed: 11/14/2022] Open
Abstract
Store-operated calcium entry (SOCE) is the process by which the emptying of endoplasmic reticulum (ER) Ca2+ stores causes an influx of Ca2+ across the plasma membrane. It is the major Ca2+ influx pathway in non-excitable cells and has a wide array of physiological functions. Upon store depletion, stromal interaction molecule 1 (STIM1), an ER calcium sensor relocates into discrete puncta at the ER-plasma membrane junction region, which results in the coupling of Ca2+ channels to initiate SOCE. However, the mechanism regulating STIM1 activity remains poorly understood. Here, we performed affinity purification of STIM1 and uncovered ER membrane protein complex 1 (EMC1) as a STIM1 binding partner. We showed that this interaction occurred in the ER through the intraluminal region of STIM1. After store depletion, EMC1 does not cluster adjacent to the plasma membrane, which suggests that it is distributed differently from STIM1. EMC1 knockdown with small interfering RNA resulted in a marked decrease in SOCE. Thus, these findings suggest that EMC1 functions as a positive regulator of SOCE.
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Affiliation(s)
- Kazuhiko Kawata
- Division of Immunology and Genome Biology, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan
| | - Akemi Baba
- Division of Immunology and Genome Biology, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan
| | - Masayuki Shiota
- Department of Molecular Biology of Medicine, Osaka City University Medical School, Osaka, 545-8585, Japan
| | - Hideki Wanibuchi
- Department of Pathology, Osaka City University Medical School, Osaka, 545-8585, Japan
| | - Yoshihiro Baba
- Division of Immunology and Genome Biology, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan
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28
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Pérez-Rodriguez S, Wulff T, Voldborg BG, Altamirano C, Trujillo-Roldán MA, Valdez-Cruz NA. Compartmentalized Proteomic Profiling Outlines the Crucial Role of the Classical Secretory Pathway during Recombinant Protein Production in Chinese Hamster Ovary Cells. ACS OMEGA 2021; 6:12439-12458. [PMID: 34056395 PMCID: PMC8154153 DOI: 10.1021/acsomega.0c06030] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 02/24/2021] [Indexed: 05/11/2023]
Abstract
Different cellular processes that contribute to protein production in Chinese hamster ovary (CHO) cells have been previously investigated by proteomics. However, although the classical secretory pathway (CSP) has been well documented as a bottleneck during recombinant protein (RP) production, it has not been well represented in previous proteomic studies. Hence, the significance of this pathway for production of RP was assessed by identifying its own proteins that were associated to changes in RP production, through subcellular fractionation coupled to shot-gun proteomics. Two CHO cell lines producing a monoclonal antibody with different specific productivities were used as cellular models, from which 4952 protein groups were identified, which represent a coverage of 59% of the Chinese hamster proteome. Data are available via ProteomeXchange with identifier PXD021014. By using SAM and ROTS algorithms, 493 proteins were classified as differentially expressed, of which about 80% was proposed as novel targets and one-third were assigned to the CSP. Endoplasmic reticulum (ER) stress, unfolded protein response, calcium homeostasis, vesicle traffic, glycosylation, autophagy, proteasomal activity, protein synthesis and translocation into ER lumen, and secretion of extracellular matrix components were some of the affected processes that occurred in the secretory pathway. Processes from other cellular compartments, such as DNA replication, transcription, cytoskeleton organization, signaling, and metabolism, were also modified. This study gives new insights into the molecular traits of higher producer cells and provides novel targets for development of new sub-lines with improved phenotypes for RP production.
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Affiliation(s)
- Saumel Pérez-Rodriguez
- Programa
de Investigación de Producción de Biomoléculas,
Departamento de Biología Molecular y Biotecnología,
Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán 04510 Ciudad de
México, México
| | - Tune Wulff
- The
Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kgs. Lyngby 2800, Denmark
| | - Bjørn G. Voldborg
- The
Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kgs. Lyngby 2800, Denmark
| | - Claudia Altamirano
- Laboratorio
de Cultivos Celulares, Escuela de Ingeniería Bioquímica, Pontificia Universidad Católica de Valparaíso, Avenida Brasil 2085 Valparaíso, Chile
| | - Mauricio A. Trujillo-Roldán
- Programa
de Investigación de Producción de Biomoléculas,
Departamento de Biología Molecular y Biotecnología,
Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán 04510 Ciudad de
México, México
| | - Norma A. Valdez-Cruz
- Programa
de Investigación de Producción de Biomoléculas,
Departamento de Biología Molecular y Biotecnología,
Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán 04510 Ciudad de
México, México
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29
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Chaya T, Patel S, Smith EM, Lam A, Miller EN, Clupper M, Kervin K, Tanis JE. A C. elegans genome-wide RNAi screen for altered levamisole sensitivity identifies genes required for muscle function. G3-GENES GENOMES GENETICS 2021; 11:6169532. [PMID: 33713125 PMCID: PMC8049432 DOI: 10.1093/g3journal/jkab047] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 02/09/2021] [Indexed: 01/17/2023]
Abstract
At the neuromuscular junction (NMJ), postsynaptic ionotropic acetylcholine receptors (AChRs) transduce a chemical signal released from a cholinergic motor neuron into an electrical signal to induce muscle contraction. To identify regulators of postsynaptic function, we conducted a genome-wide RNAi screen for genes required for proper response to levamisole, a pharmacological agonist of ionotropic L-AChRs at the Caenorhabditis elegans NMJ. A total of 117 gene knockdowns were found to cause levamisole hypersensitivity, while 18 resulted in levamisole resistance. Our screen identified conserved genes important for muscle function including some that are mutated in congenital myasthenic syndrome, congenital muscular dystrophy, congenital myopathy, myotonic dystrophy, and mitochondrial myopathy. Of the genes found in the screen, we further investigated those predicted to play a role in endocytosis of cell surface receptors. Loss of the Epsin homolog epn-1 caused levamisole hypersensitivity and had opposing effects on the levels of postsynaptic L-AChRs and GABAA receptors, resulting in increased and decreased abundance, respectively. We also examined other genes that resulted in a levamisole-hypersensitive phenotype when knocked down including gas-1, which functions in Complex I of the mitochondrial electron transport chain. Consistent with altered ATP synthesis impacting levamisole response, treatment of wild-type animals with levamisole resulted in L-AChR–dependent depletion of ATP levels. These results suggest that the paralytic effects of levamisole ultimately lead to metabolic exhaustion.
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Affiliation(s)
- Timothy Chaya
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Shrey Patel
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Erin M Smith
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Andy Lam
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Elaine N Miller
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Michael Clupper
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Kirsten Kervin
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Jessica E Tanis
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.,Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
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30
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Knowland D, Gu S, Eckert WA, Dawe GB, Matta JA, Limberis J, Wickenden AD, Bhattacharya A, Bredt DS. Functional α6β4 acetylcholine receptor expression enables pharmacological testing of nicotinic agonists with analgesic properties. J Clin Invest 2021; 130:6158-6170. [PMID: 33074244 DOI: 10.1172/jci140311] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 08/06/2020] [Indexed: 01/25/2023] Open
Abstract
The α6β4 nicotinic acetylcholine receptor (nAChR) is enriched in dorsal root ganglia neurons and is an attractive non-opioid therapeutic target for pain. However, difficulty expressing human α6β4 receptors in recombinant systems has precluded drug discovery. Here, genome-wide screening identified accessory proteins that enable reconstitution of human α6β4 nAChRs. BARP, an auxiliary subunit of voltage-dependent calcium channels, promoted α6β4 surface expression while IRE1α, an unfolded protein response sensor, enhanced α6β4 receptor assembly. Effects on α6β4 involve BARP's N-terminal region and IRE1α's splicing of XBP1 mRNA. Furthermore, clinical efficacy of nicotinic agents in relieving neuropathic pain best correlated with their activity on α6β4. Finally, BARP-knockout, but not NACHO-knockout mice lacked nicotine-induced antiallodynia, highlighting the functional importance of α6β4 in pain. These results identify roles for IRE1α and BARP in neurotransmitter receptor assembly and unlock drug discovery for the previously elusive α6β4 receptor.
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31
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Cao X, An J, Cao Y, Lv J, Wang J, Ding Y, Lin X, Zhou X. EMC3 Is Essential for Retinal Organization and Neurogenesis During Mouse Retinal Development. Invest Ophthalmol Vis Sci 2021; 62:31. [PMID: 33605987 PMCID: PMC7900856 DOI: 10.1167/iovs.62.2.31] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Accepted: 01/18/2021] [Indexed: 12/15/2022] Open
Abstract
Purpose We used a mouse model to explore the role of the endoplasmic reticulum membrane protein complex subunit 3 (EMC3) in mammalian retinal development. Methods The transcription pattern of Emc3 in C57BL/6 mice was analyzed by in situ hybridization. To explore the effects of EMC3 absence on retinal development, the Cre-loxP system was used to generate retina-specific Emc3 in knockout mice (Emc3flox/flox, Six3-cre+; CKO). Morphological changes in the retina of E13.5, E17.5, P0.5, and P7 mice were observed via hematoxylin and eosin staining. Immunofluorescence staining was used to assess protein distribution and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining to assess apoptosis changes. Proteins were identified and quantified by Western blotting and proteomic analysis. Electroretinogram (ERG), fundus color photography, and optical coherence tomography were performed on 5-week-old mice to evaluate retinal function and structure. Results The Emc3 mRNA was widely distributed in the whole retina during development. Loss of retinal EMC3 led to retinal rosette degeneration with mislocalization of cell junction molecules (β-catenin, N-cadherin, and zonula occludens-1) and polarity molecules (Par3 and PKCζ). Endoplasmic reticulum stress and TUNEL apoptosis signals were present in retinal rosette-forming cells. Although the absence of EMC3 promoted the production of photoreceptor cells, 5-week-old mice lost all visual function and had severe retinal morphological degeneration. Conclusions EMC3 regulates retinal structure by maintaining the polarity of retinal progenitor cells and regulating retinal cell apoptosis.
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Affiliation(s)
- Xiaowen Cao
- School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, Wenzhou, Zhejiang, China
| | - Jianhong An
- School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, Wenzhou, Zhejiang, China
| | - Yuqing Cao
- School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, Wenzhou, Zhejiang, China
| | - Juan Lv
- School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, Wenzhou, Zhejiang, China
| | - Jiawei Wang
- School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, Wenzhou, Zhejiang, China
| | - Yang Ding
- School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, Wenzhou, Zhejiang, China
| | - Xinhua Lin
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Xiangtian Zhou
- School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
- State Key Laboratory of Optometry, Ophthalmology and Vision Science, Wenzhou, Zhejiang, China
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Huang M, Yang L, Jiang N, Dai Q, Li R, Zhou Z, Zhao B, Lin X. Emc3 maintains intestinal homeostasis by preserving secretory lineages. Mucosal Immunol 2021; 14:873-886. [PMID: 33785873 PMCID: PMC8222001 DOI: 10.1038/s41385-021-00399-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 02/23/2021] [Accepted: 03/08/2021] [Indexed: 02/04/2023]
Abstract
Intestinal exocrine secretory lineages, including goblet cells and Paneth cells, provide vital innate host defense to pathogens. However, how these cells are specified and maintained to ensure intestinal barrier function remains poorly defined. Here we show that endoplasmic reticulum membrane protein complex subunit 3 (Emc3) is essential for differentiation and function of exocrine secretory lineages. Deletion of Emc3 in intestinal epithelium decreases mucus production by goblet cells and Paneth cell population, along with gut microbial dysbiosis, which result in spontaneous inflammation and increased susceptibility to DSS-induced colitis. Moreover, Emc3 deletion impairs stem cell niche function of Paneth cells, thus resulting in intestinal organoid culture failure. Mechanistically, Emc3 deficiency leads to increased endoplasmic reticulum (ER) stress. Mitigating ER stress with tauroursodeoxycholate acid alleviates secretory dysfunction and restores organoid formation. Our study identifies a dominant role of Emc3 in maintaining intestinal mucosal homeostasis.
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Affiliation(s)
- Meina Huang
- grid.8547.e0000 0001 0125 2443State Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai, China ,grid.8547.e0000 0001 0125 2443National Health Commission (NHC) Key Laboratory of Reproduction Regulation, Shanghai Institute of Planned Parenthood Research, Fudan University, Shanghai, China
| | - Li Yang
- grid.8547.e0000 0001 0125 2443State Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Ning Jiang
- grid.8547.e0000 0001 0125 2443State Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Quanhui Dai
- grid.8547.e0000 0001 0125 2443State Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Runsheng Li
- grid.8547.e0000 0001 0125 2443National Health Commission (NHC) Key Laboratory of Reproduction Regulation, Shanghai Institute of Planned Parenthood Research, Fudan University, Shanghai, China
| | - Zhaocai Zhou
- grid.8547.e0000 0001 0125 2443State Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Bing Zhao
- grid.8547.e0000 0001 0125 2443State Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Xinhua Lin
- grid.8547.e0000 0001 0125 2443State Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai, China
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Sharma S, Sourirajan A, Baumler DJ, Dev K. Saccharomyces cerevisiae ER membrane protein complex subunit 4 (EMC4) plays a crucial role in eIF2B-mediated translation regulation and survival under stress conditions. J Genet Eng Biotechnol 2020; 18:15. [PMID: 32476094 PMCID: PMC7261713 DOI: 10.1186/s43141-020-00029-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 04/22/2020] [Indexed: 11/10/2022]
Abstract
Background Eukaryotic initiation factor 2B (eIF2B) initiates and regulates translation initiation in eukaryotes. eIF2B gene mutations cause leukoencephalopathy called vanishing white matter disease (VWM) in humans and slow growth (Slg−) and general control derepression (Gcd−) phenotypes in Saccharomyces cerevisiae. Results To suppress eIF2B mutations, S. cerevisiae genomic DNA library was constructed in high-copy vector (YEp24) and transformed into eIF2B mutant S. cerevisiae strains. The library was screened for wild-type genes rescuing S. cerevisiae (Slg−) and (Gcd−) phenotypes. A genomic clone, Suppressor-I (Sup-I), rescued S. cerevisiae Slg− and Gcd− phenotypes (gcd7-201 gcn2∆). The YEp24/Sup-I construct contained truncated TAN1, full length EMC4, full length YGL230C, and truncated SAP4 genes. Full length EMC4 (chaperone protein) gene was sub-cloned into pEG (KG) yeast expression vector and overexpressed in gcd7-201 gcn2∆ strain which suppressed the Slg− and Gcd− phenotype. A GST-Emc4 fusion protein of 47 kDa was detected by western blotting using α-GST antibodies. Suppression was specific to gcd7-201 gcn2∆ mutation in eIF2Bβ and Gcd1-502 gcn2∆ in eIF2Bγ subunit. Emc4p overexpression also protected the wild type and mutant (gcd7-201 gcn2∆, GCD7 gcn2∆, and GCD7 GCN2∆) strains from H2O2, ethanol, and caffeine stress. Conclusions Our results suggest that Emc4p is involved in eIF2B-mediated translational regulation under stress and could provide an amenable tool to understand the eIF2B-mediated defects.
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Phillips BP, Miller EA. Ribosome-associated quality control of membrane proteins at the endoplasmic reticulum. J Cell Sci 2020; 133:133/22/jcs251983. [PMID: 33247003 PMCID: PMC7116877 DOI: 10.1242/jcs.251983] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Protein synthesis is an energetically costly, complex and risky process. Aberrant protein biogenesis can result in cellular toxicity and disease, with membrane-embedded proteins being particularly challenging for the cell. In order to protect the cell from consequences of defects in membrane proteins, quality control systems act to maintain protein homeostasis. The majority of these pathways act post-translationally; however, recent evidence reveals that membrane proteins are also subject to co-translational quality control during their synthesis in the endoplasmic reticulum (ER). This newly identified quality control pathway employs components of the cytosolic ribosome-associated quality control (RQC) machinery but differs from canonical RQC in that it responds to biogenesis state of the substrate rather than mRNA aberrations. This ER-associated RQC (ER-RQC) is sensitive to membrane protein misfolding and malfunctions in the ER insertion machinery. In this Review, we discuss the advantages of co-translational quality control of membrane proteins, as well as potential mechanisms of substrate recognition and degradation. Finally, we discuss some outstanding questions concerning future studies of ER-RQC of membrane proteins.
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Affiliation(s)
- Ben P Phillips
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
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Miller-Vedam LE, Bräuning B, Popova KD, Schirle Oakdale NT, Bonnar JL, Prabu JR, Boydston EA, Sevillano N, Shurtleff MJ, Stroud RM, Craik CS, Schulman BA, Frost A, Weissman JS. Structural and mechanistic basis of the EMC-dependent biogenesis of distinct transmembrane clients. eLife 2020; 9:e62611. [PMID: 33236988 PMCID: PMC7785296 DOI: 10.7554/elife.62611] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Accepted: 11/17/2020] [Indexed: 12/11/2022] Open
Abstract
Membrane protein biogenesis in the endoplasmic reticulum (ER) is complex and failure-prone. The ER membrane protein complex (EMC), comprising eight conserved subunits, has emerged as a central player in this process. Yet, we have limited understanding of how EMC enables insertion and integrity of diverse clients, from tail-anchored to polytopic transmembrane proteins. Here, yeast and human EMC cryo-EM structures reveal conserved intricate assemblies and human-specific features associated with pathologies. Structure-based functional studies distinguish between two separable EMC activities, as an insertase regulating tail-anchored protein levels and a broader role in polytopic membrane protein biogenesis. These depend on mechanistically coupled yet spatially distinct regions including two lipid-accessible membrane cavities which confer client-specific regulation, and a non-insertase EMC function mediated by the EMC lumenal domain. Our studies illuminate the structural and mechanistic basis of EMC's multifunctionality and point to its role in differentially regulating the biogenesis of distinct client protein classes.
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Affiliation(s)
- Lakshmi E Miller-Vedam
- Molecular, Cellular, and Computational Biophysics Graduate Program, University of California, San FranciscoSan FranciscoUnited States
- Department of Biochemistry and Biophysics, University of California, San FranciscoSan FranciscoUnited States
- Department of Biology, Whitehead Institute, MITCambridgeUnited States
- Department of Cellular and Molecular Pharmacology, University of California, San FranciscoSan FranciscoUnited States
| | - Bastian Bräuning
- Department of Molecular Machines and Signaling, Max Planck Institute of BiochemistryMartinsriedGermany
| | - Katerina D Popova
- Department of Biology, Whitehead Institute, MITCambridgeUnited States
- Department of Cellular and Molecular Pharmacology, University of California, San FranciscoSan FranciscoUnited States
- Biomedical Sciences Graduate Program, University of California, San FranciscoSan FranciscoUnited States
| | - Nicole T Schirle Oakdale
- Department of Cellular and Molecular Pharmacology, University of California, San FranciscoSan FranciscoUnited States
| | - Jessica L Bonnar
- Department of Biology, Whitehead Institute, MITCambridgeUnited States
- Department of Cellular and Molecular Pharmacology, University of California, San FranciscoSan FranciscoUnited States
| | - Jesuraj R Prabu
- Department of Molecular Machines and Signaling, Max Planck Institute of BiochemistryMartinsriedGermany
| | - Elizabeth A Boydston
- Department of Cellular and Molecular Pharmacology, University of California, San FranciscoSan FranciscoUnited States
| | - Natalia Sevillano
- Department of Pharmaceutical Chemistry, University of California, San FranciscoSan FranciscoUnited States
| | - Matthew J Shurtleff
- Department of Cellular and Molecular Pharmacology, University of California, San FranciscoSan FranciscoUnited States
| | - Robert M Stroud
- Department of Biochemistry and Biophysics, University of California, San FranciscoSan FranciscoUnited States
| | - Charles S Craik
- Department of Pharmaceutical Chemistry, University of California, San FranciscoSan FranciscoUnited States
| | - Brenda A Schulman
- Department of Molecular Machines and Signaling, Max Planck Institute of BiochemistryMartinsriedGermany
| | - Adam Frost
- Department of Biochemistry and Biophysics, University of California, San FranciscoSan FranciscoUnited States
| | - Jonathan S Weissman
- Department of Biology, Whitehead Institute, MITCambridgeUnited States
- Department of Cellular and Molecular Pharmacology, University of California, San FranciscoSan FranciscoUnited States
- Howard Hughes Medical InstituteChevy ChaseUnited States
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Tan JH, Cao RC, Zhou L, Zhou ZT, Chen HJ, Xu J, Chen XM, Jin YC, Lin JY, Qi ZC, Zeng JL, Li SJ, Luo M, Hu GD, Jin J, Zhang GW. EMC6 regulates acinar apoptosis via APAF1 in acute and chronic pancreatitis. Cell Death Dis 2020; 11:966. [PMID: 33177505 PMCID: PMC7658364 DOI: 10.1038/s41419-020-03177-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 10/24/2020] [Accepted: 10/27/2020] [Indexed: 02/07/2023]
Abstract
Treatment of acute pancreatitis (AP) and chronic pancreatitis (CP) remains problematic due to a lack of knowledge about disease-specific regulatory targets and mechanisms. The purpose of this study was to screen proteins related to endoplasmic reticulum (ER) stress and apoptosis pathways that may play a role in pancreatitis. Human pancreatic tissues including AP, CP, and healthy volunteers were collected during surgery. Humanized PRSS1 (protease serine 1) transgenic (PRSS1Tg) mice were constructed and treated with caerulein to mimic the development of human AP and CP. Potential regulatory proteins in pancreatitis were identified by proteomic screen using pancreatic tissues of PRSS1Tg AP mice. Adenoviral shRNA-mediated knockdown of identified proteins, followed by functional assays was performed to validate their roles. Functional analyses included transmission electron microscopy for ultrastructural analysis; qRT-PCR, western blotting, co-immunoprecipitation, immunohistochemistry, and immunofluorescence for assessment of gene or protein expression, and TUNEL assays for assessment of acinar cell apoptosis. Humanized PRSS1Tg mice could mimic the development of human pancreatic inflammatory diseases. EMC6 and APAF1 were identified as potential regulatory molecules in AP and CP models by proteomic analysis. Both EMC6 and APAF1 regulated apoptosis and inflammatory injury in pancreatic inflammatory diseases. Moreover, APAF1 was regulated by EMC6, induced apoptosis to injure acinar cells and promoted inflammation. In the progression of pancreatitis, EMC6 was activated and then upregulated APAF1 to induce acinar cell apoptosis and inflammatory injury. These findings suggest that EMC6 may be a new therapeutic target for the treatment of pancreatic inflammatory diseases.
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Affiliation(s)
- Jie-Hui Tan
- Division of Hepatobiliopancreatic Surgery, Department of General Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Rong-Chang Cao
- Division of Hepatobiliopancreatic Surgery, Department of General Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Lei Zhou
- Division of Hepatobiliopancreatic Surgery, Department of General Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Zhi-Tao Zhou
- Department of the Electronic Microscope Room, Central Laboratory, Southern Medical University, Guangzhou, China
| | - Huo-Ji Chen
- School of Traditional Chinese Medicine, Southern Medical University, Guangzhou, China
| | - Jia Xu
- Department of Pathophysiology, Southern Medical University, Guangzhou, China
| | - Xue-Mei Chen
- Department of Occupational Health and Medicine, Guangdong Provincial Key Laboratory of Tropical Disease Research, School of Public Health, Southern Medical University, Guangzhou, China
| | - Yang-Chen Jin
- The First Clinical Medical College, Southern Medical University, Guangzhou, China
| | - Jia-Yu Lin
- The First Clinical Medical College, Southern Medical University, Guangzhou, China
| | - Zhao-Chang Qi
- The First Clinical Medical College, Southern Medical University, Guangzhou, China
| | - Jun-Ling Zeng
- Laboratory Animal Research Center of Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Shu-Ji Li
- Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Southern Medical University, Guangzhou, China
| | - Min Luo
- Department of Laboratory Medicine, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Guo-Dong Hu
- Department of Respiratory and Crit Care Medicine, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Jin Jin
- Department of Gynaecology and Obstetrics, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Guo-Wei Zhang
- Division of Hepatobiliopancreatic Surgery, Department of General Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, China.
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Umair M, Ballow M, Asiri A, Alyafee Y, Al Tuwaijri A, Alhamoudi KM, Aloraini T, Abdelhakim M, Althagafi AT, Kafkas S, Alsubaie L, Alrifai MT, Hoehndorf R, Alfares A, Alfadhel M. EMC10 homozygous variant identified in a family with global developmental delay, mild intellectual disability, and speech delay. Clin Genet 2020; 98:555-561. [PMID: 32869858 PMCID: PMC7756316 DOI: 10.1111/cge.13842] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 08/27/2020] [Accepted: 08/28/2020] [Indexed: 12/27/2022]
Abstract
In recent years, several genes have been implicated in the variable disease presentation of global developmental delay (GDD) and intellectual disability (ID). The endoplasmic reticulum membrane protein complex (EMC) family is known to be involved in GDD and ID. Homozygous variants of EMC1 are associated with GDD, scoliosis, and cerebellar atrophy, indicating the relevance of this pathway for neurogenetic disorders. EMC10 is a bone marrow‐derived angiogenic growth factor that plays an important role in infarct vascularization and promoting tissue repair. However, this gene has not been previously associated with human disease. Herein, we describe a Saudi family with two individuals segregating a recessive neurodevelopmental disorder. Both of the affected individuals showed mild ID, speech delay, and GDD. Whole‐exome sequencing (WES) and Sanger sequencing were performed to identify candidate genes. Further, to elucidate the functional effects of the variant, quantitative real‐time PCR (RT‐qPCR)‐based expression analysis was performed. WES revealed a homozygous splice acceptor site variant (c.679‐1G>A) in EMC10 (chromosome 19q13.33) that segregated perfectly within the family. RT‐qPCR showed a substantial decrease in the relative EMC10 gene expression in the patients, indicating the pathogenicity of the identified variant. For the first time in the literature, the EMC10 gene variant was associated with mild ID, speech delay, and GDD. Thus, this gene plays a key role in developmental milestones, with the potential to cause neurodevelopmental disorders in humans.
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Affiliation(s)
- Muhammad Umair
- Medical Genomics Research Department, King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences, Ministry of National Guard Health Affairs (MNGH), Riyadh, Saudi Arabia
| | - Mariam Ballow
- Medical Genomics Research Department, King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences, Ministry of National Guard Health Affairs (MNGH), Riyadh, Saudi Arabia
| | - Abdulaziz Asiri
- Medical Genomics Research Department, King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences, Ministry of National Guard Health Affairs (MNGH), Riyadh, Saudi Arabia
| | - Yusra Alyafee
- Medical Genomics Research Department, King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences, Ministry of National Guard Health Affairs (MNGH), Riyadh, Saudi Arabia
| | - Abeer Al Tuwaijri
- Medical Genomics Research Department, King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences, Ministry of National Guard Health Affairs (MNGH), Riyadh, Saudi Arabia
| | - Kheloud M Alhamoudi
- Medical Genomics Research Department, King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences, Ministry of National Guard Health Affairs (MNGH), Riyadh, Saudi Arabia
| | - Taghrid Aloraini
- Department of Pathology and Laboratory Medicine, King Abdulaziz Medical City, Riyadh, Saudi Arabia
| | - Marwa Abdelhakim
- Computer, Electrical and Mathematical Sciences & Engineering Division, Computational Bioscience Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
| | - Azza Thamer Althagafi
- Computer, Electrical and Mathematical Sciences & Engineering Division, Computational Bioscience Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.,College of Computers and Information Technology, Taif University, Taif, Saudi Arabia
| | - Senay Kafkas
- Computer, Electrical and Mathematical Sciences & Engineering Division, Computational Bioscience Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
| | - Lamia Alsubaie
- Division of Genetics, Department of Pediatrics, King Abdulaziz Medical City, Riyadh, Saudi Arabia
| | - Muhammad Talal Alrifai
- Department of Pediatrics, Division of Neurology, King Saud Bin Abdulaziz University for Health Sciences, King Abdulaziz Medical City, Ministry of National Guard Health Affairs (MNGH), Riyadh, Saudi Arabia
| | - Robert Hoehndorf
- Computer, Electrical and Mathematical Sciences & Engineering Division, Computational Bioscience Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
| | - Ahmed Alfares
- Department of Pediatrics, College of Medicine, Qassim University, Saudi Arabia
| | - Majid Alfadhel
- Medical Genomics Research Department, King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences, Ministry of National Guard Health Affairs (MNGH), Riyadh, Saudi Arabia.,Division of Genetics, Department of Pediatrics, King Abdullah Specialized Children's Hospital, King Abdulaziz Medical City, Riyadh, Saudi Arabia
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38
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Tian S, Wu Q, Zhou B, Choi MY, Ding B, Yang W, Dong M. Proteomic Analysis Identifies Membrane Proteins Dependent on the ER Membrane Protein Complex. Cell Rep 2020; 28:2517-2526.e5. [PMID: 31484065 PMCID: PMC6749609 DOI: 10.1016/j.celrep.2019.08.006] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 06/18/2019] [Accepted: 07/30/2019] [Indexed: 02/04/2023] Open
Abstract
The endoplasmic reticulum (ER) membrane protein complex (EMC) is a key contributor to biogenesis and membrane integration of transmembrane proteins, but our understanding of its mechanisms and the range of EMC-dependent proteins remains incomplete. Here, we carried out an unbiased mass spectrometry (MS)-based quantitative proteomic analysis comparing membrane proteins in EMC-deficient cells to wild-type (WT) cells and identified 36 EMC-dependent membrane proteins and 171 EMC-independent membrane proteins. Of these, six EMC-dependent and six EMC-independent proteins were further independently validated. We found that a common feature among EMC-dependent proteins is that they contain transmembrane domains (TMDs) with polar and/or charged residues. Mutagenesis studies demonstrate that EMC dependency can be converted in cells by removing or introducing polar and/or charged residues within TMDs. Our studies expand the list of validated EMC-dependent and EMC-independent proteins and suggest that the EMC is involved in handling TMDs with residues challenging for membrane integration. The endoplasmic reticulum membrane protein complex (EMC) contributes to the biogenesis of transmembrane proteins. Using mass spectrometry-based quantitative proteomic analysis, Tian et al. identify EMC-dependent and EMC-independent proteins. The authors find evidence that the EMC is involved in handling transmembrane domains with polar and/or charged residues that are challenging for membrane integration.
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Affiliation(s)
- Songhai Tian
- Department of Urology, Boston Children's Hospital, and Department of Surgery and Department of Microbiology, Harvard Medical School, Boston, MA 02115, USA
| | - Quan Wu
- Department of Urology, Boston Children's Hospital, and Department of Surgery and Department of Microbiology, Harvard Medical School, Boston, MA 02115, USA; Central Laboratory of Medical Research Centre, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230001, People's Republic of China
| | - Bo Zhou
- Division of Cancer Biology and Therapeutics, Departments of Surgery and Biomedical Sciences, Samuel Oschin Comprehensive Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Mei Yuk Choi
- Division of Genetics, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02115, USA
| | - Bo Ding
- Bonacept LLC, San Diego, CA 92122, USA
| | - Wei Yang
- Division of Cancer Biology and Therapeutics, Departments of Surgery and Biomedical Sciences, Samuel Oschin Comprehensive Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Min Dong
- Department of Urology, Boston Children's Hospital, and Department of Surgery and Department of Microbiology, Harvard Medical School, Boston, MA 02115, USA.
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39
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Marquez J, Criscione J, Charney RM, Prasad MS, Hwang WY, Mis EK, García-Castro MI, Khokha MK. Disrupted ER membrane protein complex-mediated topogenesis drives congenital neural crest defects. J Clin Invest 2020; 130:813-826. [PMID: 31904590 DOI: 10.1172/jci129308] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 10/22/2019] [Indexed: 12/20/2022] Open
Abstract
Multipass membrane proteins have a myriad of functions, including transduction of cell-cell signals, ion transport, and photoreception. Insertion of these proteins into the membrane depends on the endoplasmic reticulum (ER) membrane protein complex (EMC). Recently, birth defects have been observed in patients with variants in the gene encoding a member of this complex, EMC1. Patient phenotypes include congenital heart disease, craniofacial malformations, and neurodevelopmental disease. However, a molecular connection between EMC1 and these birth defects is lacking. Using Xenopus, we identified defects in neural crest cells (NCCs) upon emc1 depletion. We then used unbiased proteomics and discovered a critical role for emc1 in WNT signaling. Consistent with this, readouts of WNT signaling and Frizzled (Fzd) levels were reduced in emc1-depleted embryos, while NCC defects could be rescued with β-catenin. Interestingly, other transmembrane proteins were mislocalized upon emc1 depletion, providing insight into additional patient phenotypes. To translate our findings back to humans, we found that EMC1 was necessary for human NCC development in vitro. Finally, we tested patient variants in our Xenopus model and found the majority to be loss-of-function alleles. Our findings define molecular mechanisms whereby EMC1 dysfunction causes disease phenotypes through dysfunctional multipass membrane protein topogenesis.
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Affiliation(s)
- Jonathan Marquez
- Pediatric Genomics Discovery Program, Department of Pediatrics and Genetics, Yale University School of Medicine, New Haven, Connecticut, USA
| | - June Criscione
- Pediatric Genomics Discovery Program, Department of Pediatrics and Genetics, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Rebekah M Charney
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, California, USA
| | - Maneeshi S Prasad
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, California, USA
| | - Woong Y Hwang
- Pediatric Genomics Discovery Program, Department of Pediatrics and Genetics, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Emily K Mis
- Pediatric Genomics Discovery Program, Department of Pediatrics and Genetics, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Martín I García-Castro
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, California, USA
| | - Mustafa K Khokha
- Pediatric Genomics Discovery Program, Department of Pediatrics and Genetics, Yale University School of Medicine, New Haven, Connecticut, USA
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40
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Loss of the ER membrane protein complex subunit Emc3 leads to retinal bipolar cell degeneration in aged mice. PLoS One 2020; 15:e0238435. [PMID: 32886670 PMCID: PMC7473584 DOI: 10.1371/journal.pone.0238435] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2020] [Accepted: 08/17/2020] [Indexed: 02/05/2023] Open
Abstract
The endoplasmic reticulum (ER) membrane protein complex (EMC) is a conserved protein complex involved in inserting the transmembrane domain of membrane proteins into membranes in the ER. EMC3 is an essential component of EMC and is important for rhodopsin synthesis in photoreceptor cells. However, the in vivo function of Emc3 in bipolar cells (BCs) has not been determined. To explore the role of Emc3 in BCs, we generated a BC-specific Emc3 knockout mouse model (named Emc3 cKO) using the Purkinje cell protein 2 (Pcp2) Cre line. Although normal electroretinography (ERG) b-waves were observed in Emc3 cKO mice at 6 months of age, Emc3 cKO mice exhibited reduced b-wave amplitudes at 12 months of age, as determined by scotopic and photopic ERG, and progressive death of BCs, whereas the ERG a-wave amplitudes were preserved. PKCa staining of retinal cryosections from Emc3 cKO mice revealed death of rod BCs. Loss of Emc3 led to the presence of the synaptic protein mGLuR6 in the outer nuclear layer (ONL). Immunostaining analysis of presynaptic protein postsynaptic density protein 95 (PSD95) revealed rod terminals retracted to the ONL in Emc3 cKO mice at 12 months of age. In addition, deletion of Emc3 resulted in elevated glial fibrillary acidic protein, indicating reactive gliosis in the retina. Our data demonstrate that loss of Emc3 in BCs leads to decreased ERG response, increased astrogliosis and disruption of the retinal inner nuclear layer in mice of 12 months of age. Taken together, our studies indicate that Emc3 is not required for the development of BCs but is important for long-term survival of BCs.
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41
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Treinin M, Jin Y. Cholinergic transmission in C. elegans: Functions, diversity, and maturation of ACh-activated ion channels. J Neurochem 2020; 158:1274-1291. [PMID: 32869293 DOI: 10.1111/jnc.15164] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 08/13/2020] [Accepted: 08/21/2020] [Indexed: 02/06/2023]
Abstract
Acetylcholine is an abundant neurotransmitter in all animals. Effects of acetylcholine are excitatory, inhibitory, or modulatory depending on the receptor and cell type. Research using the nematode C. elegans has made ground-breaking contributions to the mechanistic understanding of cholinergic transmission. Powerful genetic screens for behavioral mutants or for responses to pharmacological reagents identified the core cellular machinery for synaptic transmission. Pharmacological reagents that perturb acetylcholine-mediated processes led to the discovery and also uncovered the composition and regulators of acetylcholine-activated channels and receptors. From a combination of electrophysiological and molecular cellular studies, we have gained a profound understanding of cholinergic signaling at the levels of synapses, neural circuits, and animal behaviors. This review will begin with a historical overview, then cover in-depth current knowledge on acetylcholine-activated ionotropic receptors, mechanisms regulating their functional expression and their functions in regulating locomotion.
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Affiliation(s)
- Millet Treinin
- Department of Medical Neurobiology, Hadassah Medical school - Hebrew University, Jerusalem, Israel
| | - Yishi Jin
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, CA, USA
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The ER Membrane Protein Complex Promotes Biogenesis of Dengue and Zika Virus Non-structural Multi-pass Transmembrane Proteins to Support Infection. Cell Rep 2020; 27:1666-1674.e4. [PMID: 31067454 PMCID: PMC6521869 DOI: 10.1016/j.celrep.2019.04.051] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 03/05/2019] [Accepted: 04/09/2019] [Indexed: 01/01/2023] Open
Abstract
Although flaviviruses co-opt the function of the host endoplasmic reticulum (ER) membrane protein complex (EMC) during infection, a mechanistic explanation for this observation remains unclear. Here, we show that the EMC promotes biogenesis of dengue virus (DENV) and Zika virus (ZIKV) non-structural multi-pass transmembrane proteins NS4A and NS4B, which are necessary for viral replication. The EMC binds to NS4B and colocalizes with the DENV replication organelle. Mapping analysis reveals that the two N-terminal marginally hydrophobic domains of NS4B confer EMC dependency. Furthermore, altering the hydrophobicity of these two marginally hydrophobic domains relieves NS4B’s EMC dependency. We demonstrate that NS4B biogenesis, but not its stability, is reduced in EMC-depleted cells. Our data suggest that the EMC acts as a multi-pass transmembrane chaperone required for expression of at least two virally encoded proteins essential for flavivirus infection and point to a shared vulnerability during the viral life cycle that could be exploited for antiviral therapy. Multiple genetic screens have identified the ER membrane protein complex (EMC) as essential for infection by dengue and Zika flaviviruses. Lin et al. demonstrate that efficient biogenesis of the viral non-structural proteins NS4A and NS4B requires the EMC.
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Bai L, You Q, Feng X, Kovach A, Li H. Structure of the ER membrane complex, a transmembrane-domain insertase. Nature 2020; 584:475-478. [PMID: 32494008 PMCID: PMC7442705 DOI: 10.1038/s41586-020-2389-3] [Citation(s) in RCA: 77] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 04/07/2020] [Indexed: 11/24/2022]
Abstract
The ER membrane complex (EMC) cooperates with the Sec61 translocon to co-translationally insert a transmembrane helix (TMH) of many multi-pass integral membrane proteins into the ER membrane, and it is also responsible for inserting the TMH of some tail-anchored proteins 1–3. How EMC accomplishes this feat has been unclear. Here we report the first cryo-EM structure of the eukaryotic EMC. We found that the Saccharomyces cerevisiae EMC contains eight subunits (Emc1–6, 7, and 10); has a large lumenal region and a smaller cytosolic region; and has a transmembrane region formed by Emc4, 5, and 6 plus the transmembrane domains (TMDs) of Emc1 and 3. We identified a 5-TMH fold centered around Emc3 that resembles the prokaryotic insertase YidC and that delineates a largely hydrophilic client pocket. The TMD of Emc4 tilts away from the main transmembrane region of EMC and is partially mobile. Mutational studies demonstrated that Emc4 flexibility and the hydrophilicity of the client pocket are required for EMC function. The EMC structure reveals a remarkable evolutionary conservation with the prokaryotic insertases 4,5; suggests a similar mechanism of TMH insertion; and provides a framework for detailed understanding of membrane insertion for numerous eukaryotic integral membrane proteins and tail-anchored proteins.
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Affiliation(s)
- Lin Bai
- Structural Biology Program, Van Andel Institute, Grand Rapids, MI, USA.
| | - Qinglong You
- Structural Biology Program, Van Andel Institute, Grand Rapids, MI, USA
| | - Xiang Feng
- Structural Biology Program, Van Andel Institute, Grand Rapids, MI, USA
| | - Amanda Kovach
- Structural Biology Program, Van Andel Institute, Grand Rapids, MI, USA
| | - Huilin Li
- Structural Biology Program, Van Andel Institute, Grand Rapids, MI, USA.
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O'Donnell JP, Phillips BP, Yagita Y, Juszkiewicz S, Wagner A, Malinverni D, Keenan RJ, Miller EA, Hegde RS. The architecture of EMC reveals a path for membrane protein insertion. eLife 2020; 9:e57887. [PMID: 32459176 PMCID: PMC7292650 DOI: 10.7554/elife.57887] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 05/26/2020] [Indexed: 12/29/2022] Open
Abstract
Approximately 25% of eukaryotic genes code for integral membrane proteins that are assembled at the endoplasmic reticulum. An abundant and widely conserved multi-protein complex termed EMC has been implicated in membrane protein biogenesis, but its mechanism of action is poorly understood. Here, we define the composition and architecture of human EMC using biochemical assays, crystallography of individual subunits, site-specific photocrosslinking, and cryo-EM reconstruction. Our results suggest that EMC's cytosolic domain contains a large, moderately hydrophobic vestibule that can bind a substrate's transmembrane domain (TMD). The cytosolic vestibule leads into a lumenally-sealed, lipid-exposed intramembrane groove large enough to accommodate a single substrate TMD. A gap between the cytosolic vestibule and intramembrane groove provides a potential path for substrate egress from EMC. These findings suggest how EMC facilitates energy-independent membrane insertion of TMDs, explain why only short lumenal domains are translocated by EMC, and constrain models of EMC's proposed chaperone function.
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Affiliation(s)
| | - Ben P Phillips
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | - Yuichi Yagita
- MRC Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | | | | | | | - Robert J Keenan
- Department of Biochemistry and Molecular Biology, The University of ChicagoChicagoUnited States
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45
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Volkmar N, Christianson JC. Squaring the EMC - how promoting membrane protein biogenesis impacts cellular functions and organismal homeostasis. J Cell Sci 2020; 133:133/8/jcs243519. [PMID: 32332093 PMCID: PMC7188443 DOI: 10.1242/jcs.243519] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Integral membrane proteins play key functional roles at organelles and the plasma membrane, necessitating their efficient and accurate biogenesis to ensure appropriate targeting and activity. The endoplasmic reticulum membrane protein complex (EMC) has recently emerged as an important eukaryotic complex for biogenesis of integral membrane proteins by promoting insertion and stability of atypical and sub-optimal transmembrane domains (TMDs). Although confirmed as a bona fide complex almost a decade ago, light is just now being shed on the mechanism and selectivity underlying the cellular responsibilities of the EMC. In this Review, we revisit the myriad of functions attributed the EMC through the lens of these new mechanistic insights, to address questions of the cellular and organismal roles the EMC has evolved to undertake. Summary: The EMC is an important factor facilitating membrane protein biogenesis. Here we discuss the broad cellular and organismal responsibilities overseen by client proteins requiring the EMC for maturation.
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Affiliation(s)
- Norbert Volkmar
- Jeffrey Cheah Biomedical Centre, Department of Medicine, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0XY, UK
| | - John C Christianson
- Oxford Centre for Translational Myeloma Research, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Botnar Research Centre, Headington, Oxford OX3 7LD, UK
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Selective EMC subunits act as molecular tethers of intracellular organelles exploited during viral entry. Nat Commun 2020; 11:1127. [PMID: 32111841 PMCID: PMC7048770 DOI: 10.1038/s41467-020-14967-w] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 02/10/2020] [Indexed: 12/22/2022] Open
Abstract
Although viruses must navigate the complex host endomembrane system to infect cells, the strategies used to achieve this is unclear. During entry, polyomavirus SV40 is sorted from the late endosome (LE) to the endoplasmic reticulum (ER) to cause infection, yet how this is accomplished remains enigmatic. Here we find that EMC4 and EMC7, two ER membrane protein complex (EMC) subunits, support SV40 infection by promoting LE-to-ER targeting of the virus. They do this by engaging LE-associated Rab7, presumably to stabilize contact between the LE and ER. These EMC subunits also bind to the ER-resident fusion machinery component syntaxin18, which is required for SV40-arrival to the ER. Our data suggest that EMC4 and EMC7 act as molecular tethers, inter-connecting two intracellular compartments to enable efficient transport of a virus between these compartments. As LE-to-ER transport of cellular cargos is unclear, our results have broad implications for illuminating inter-organelle cargo transport. The endoplasmic reticulum membrane protein complex (EMC) is known to play a role in SV40 viral infection but precise mechanisms are unclear. Here, the authors report that the EMC acts as tether of late endosome–endoplasmic reticulum interorganellar membrane contact sites to promote SV40 viral infection.
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Abstract
Due to their topology tail-anchored (TA) proteins must target to the membrane independently of the co-translational route defined by the signal sequence recognition particle (SRP), its receptor and the translocon Sec61. More than a decade of work has extensively characterized a highly conserved pathway, the yeast GET or mammalian TRC40 pathway, which is capable of countering the biogenetic challenge posed by the C-terminal TA anchor. In this review we briefly summarize current models of this targeting route and focus on emerging aspects such as the intricate interplay with the proteostatic network of cells and with other targeting pathways. Importantly, we consider the lessons provided by the in vivo analysis of the pathway in different model organisms and by the consideration of its full client spectrum in more recent studies. This analysis of the state of the field highlights directions in which the current models may be experimentally probed and conceptually extended.
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Affiliation(s)
- Nica Borgese
- Institute of Neuroscience and BIOMETRA Department, Consiglio Nazionale delle Ricerche and Università degli Studi di Milano, via Vanvitelli 32, 20129, Milan, Italy.
| | - Javier Coy-Vergara
- Department of Molecular Biology, University of Göttingen Medical Centre, Humboldtallee 23, 37073, Göttingen, Germany
| | - Sara Francesca Colombo
- Institute of Neuroscience and BIOMETRA Department, Consiglio Nazionale delle Ricerche and Università degli Studi di Milano, via Vanvitelli 32, 20129, Milan, Italy
| | - Blanche Schwappach
- Department of Molecular Biology, University of Göttingen Medical Centre, Humboldtallee 23, 37073, Göttingen, Germany.
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Abstract
One-fourth of eukaryotic genes code for integral membrane proteins, nearly all of which are inserted and assembled at the endoplasmic reticulum (ER). The defining feature of membrane proteins is one or more transmembrane domains (TMDs). During membrane protein biogenesis, TMDs are selectively recognized, shielded, and chaperoned into the lipid bilayer, where they often assemble with other TMDs. If maturation fails, exposed TMDs serve as a cue for engagement of degradation pathways. Thus, TMD-recognition factors in the cytosol and ER are essential for membrane protein biogenesis and quality control. Here, we discuss the growing assortment of cytosolic and membrane-embedded TMD-recognition factors, the pathways within which they operate, and mechanistic principles of recognition.
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Hiramatsu N, Tago T, Satoh T, Satoh AK. ER membrane protein complex is required for the insertions of late-synthesized transmembrane helices of Rh1 in Drosophila photoreceptors. Mol Biol Cell 2019; 30:2890-2900. [PMID: 31553680 PMCID: PMC6822582 DOI: 10.1091/mbc.e19-08-0434] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Most membrane proteins are synthesized on and inserted into the membrane of the endoplasmic reticulum (ER), in eukaryote. The widely conserved ER membrane protein complex (EMC) facilitates the biogenesis of a wide range of membrane proteins. In this study, we investigated the EMC function using Drosophila photoreceptor as a model system. We found that the EMC was necessary only for the biogenesis of a subset of multipass membrane proteins such as rhodopsin (Rh1), TRP, TRPL, Csat, Cni, SERCA, and Na+K+ATPase α, but not for that of secretory or single-pass membrane proteins. Additionally, in EMC-deficient cells, Rh1 was translated to its C terminus but degraded independently from ER-associated degradation. Thus, EMC exerted its effect after translation but before or during the membrane integration of transmembrane domains (TMDs). Finally, we found that EMC was not required for the stable expression of the first three TMDs of Rh1 but was required for that of the fourth and fifth TMDs. Our results suggested that EMC is required for the ER membrane insertion of succeeding TMDs of multipass membrane proteins.
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Affiliation(s)
- Naoki Hiramatsu
- Program of Life and Environmental Sciences, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
| | - Tatsuya Tago
- Program of Life and Environmental Sciences, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
| | - Takunori Satoh
- Program of Life and Environmental Sciences, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
| | - Akiko K Satoh
- Program of Life and Environmental Sciences, Graduate School of Integral Science for Life, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
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50
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Zhou Y, Wu F, Zhang M, Xiong Z, Yin Q, Ru Y, Shi H, Li J, Mao S, Li Y, Cao X, Hu R, Liew CW, Ding Q, Wang X, Zhang Y. EMC10 governs male fertility via maintaining sperm ion balance. J Mol Cell Biol 2019; 10:503-514. [PMID: 29659949 DOI: 10.1093/jmcb/mjy024] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Accepted: 04/05/2018] [Indexed: 02/01/2023] Open
Abstract
Infertility is a severe public health problem worldwide that prevails up to 15% in reproductive-age couples, and male infertility accounts for half of total infertility. Studies on genetically modified animal models have identified lots of genes involved in the pathogenesis of male infertility. The underlying causes, however, remain largely unclear. In this study, we provide evidence that EMC10, one subunit of endoplasmic reticulum (ER) membrane protein complex (EMC), is required for male fertility. EMC10 is significantly decreased in spermatozoa from patients with asthenozoospermia and positively associated with human sperm motility. Male mice lacking Emc10 gene are completely sterile. Emc10-null spermatozoa exhibit multiple defects including abnormal morphology, decreased motility, impaired capacitation, and impotency of acrosome reaction, thereby which are incapable of fertilizing intact or ZP-free oocytes. However, intracytoplasmic sperm injection could rescue this defect caused by EMC10 deletion. Mechanistically, EMC10 deficiency leads to inactivation of Na/K-ATPase, in turn giving rise to an increased level of intracellular Na+ in spermatozoa, which contributes to decreased sperm motility and abnormal morphology. Other mechanistic investigations demonstrate that the absence of EMC10 results in a reduction of HCO3- entry and subsequent decreases of both cAMP-dependent protein kinase A substrate phosphorylation and protein tyrosine phosphorylation. These data demonstrate that EMC10 is indispensable to male fertility via maintaining sperm ion balance of Na+ and HCO3-, and also suggest that EMC10 is a promising biomarker for male fertility and a potential pharmaceutical target to treat male infertility.
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Affiliation(s)
- Yuchuan Zhou
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Fei Wu
- Department of Urology, Huashan Hospital, Fudan University, Shanghai, China
| | - Man Zhang
- State Key Laboratory of Cell Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Zuquan Xiong
- Department of Urology, Huashan Hospital, Fudan University, Shanghai, China
| | - Qianqian Yin
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Yanfei Ru
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Huijuan Shi
- China National Population and Family Planning Key Laboratory of Contraceptive Drugs and Devices, Shanghai Institute of Planned Parenthood Research, Shanghai, China
| | - Jinsong Li
- State Key Laboratory of Cell Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Shanhua Mao
- Department of Urology, Huashan Hospital, Fudan University, Shanghai, China
| | - Yanliang Li
- Department of Endocrinology, Huashan Hospital, Fudan University, Shanghai, China
| | - Xinyi Cao
- Department of Endocrinology, Huashan Hospital, Fudan University, Shanghai, China
| | - Renming Hu
- Department of Endocrinology, Huashan Hospital, Fudan University, Shanghai, China
| | - Chong Wee Liew
- Department of Physiology & Biophysics, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA
| | - Qiang Ding
- Department of Urology, Huashan Hospital, Fudan University, Shanghai, China
| | - Xuanchun Wang
- Department of Endocrinology, Huashan Hospital, Fudan University, Shanghai, China
| | - Yonglian Zhang
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
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