1
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Liu Y, Hu J, Yan B. Enrichment of ER tubule-derived microsomes by differential centrifugation and immunoprecipitation. BIOPHYSICS REPORTS 2024; 10:61-66. [PMID: 38774354 PMCID: PMC11103718 DOI: 10.52601/bpr.2023.230031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 12/15/2023] [Indexed: 05/24/2024] Open
Abstract
The endoplasmic reticulum (ER) is an essential component of the endomembrane system in eukaryotes and plays a crucial role in protein and lipid synthesis, as well as the maintenance of calcium homeostasis. Morphologically, the ER is composed primarily of sheets and tubules. The tubular ER is composed of a network of tubular membrane structures, each with diameters ranging from 30 to 50 nanometers. In recent years, there has been in-depth research on the molecular mechanisms of membrane shaping and membrane fusion of the tubular ER. However, there is still limited understanding of the specific physiological functions of the tubular ER. Here, we report a protocol that combines differential centrifugation and immunoprecipitation to specifically enrich microsomes originating from the tubular ER in yeast. The ER tubule-derived microsomes can be further used for proteomic and lipidomic studies or other biochemical analyses.
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Affiliation(s)
- Yiduo Liu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 101408, China
| | - Junjie Hu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 101408, China
| | - Bing Yan
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
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2
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Martínez-Andrade JM, Roberson RW, Riquelme M. A bird's-eye view of the endoplasmic reticulum in filamentous fungi. Microbiol Mol Biol Rev 2024; 88:e0002723. [PMID: 38372526 PMCID: PMC10966943 DOI: 10.1128/mmbr.00027-23] [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] [Indexed: 02/20/2024] Open
Abstract
SUMMARYThe endoplasmic reticulum (ER) is one of the most extensive organelles in eukaryotic cells. It performs crucial roles in protein and lipid synthesis and Ca2+ homeostasis. Most information on ER types, functions, organization, and domains comes from studies in uninucleate animal, plant, and yeast cells. In contrast, there is limited information on the multinucleate cells of filamentous fungi, i.e., hyphae. We provide an analytical review of existing literature to categorize different types of ER described in filamentous fungi while emphasizing the research techniques and markers used. Additionally, we identify the knowledge gaps that need to be resolved better to understand the structure-function correlation of ER in filamentous fungi. Finally, advanced technologies that can provide breakthroughs in understanding the ER in filamentous fungi are discussed.
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Affiliation(s)
- Juan M. Martínez-Andrade
- Department of Microbiology, Centro de Investigación Científica y Educación Superior de Ensenada (CICESE), Ensenada, Baja California, Mexico
| | | | - Meritxell Riquelme
- Department of Microbiology, Centro de Investigación Científica y Educación Superior de Ensenada (CICESE), Ensenada, Baja California, Mexico
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3
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Merta H, Isogai T, Paul B, Danuser G, Henne WM. Spatial proteomics of ER tubules reveals CLMN, an ER-actin tether at focal adhesions that promotes cell migration. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.24.577043. [PMID: 38328045 PMCID: PMC10849733 DOI: 10.1101/2024.01.24.577043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
The endoplasmic reticulum (ER) is structurally and functionally diverse, yet how its functions are organized within morphological subdomains is incompletely understood. Utilizing TurboID-based proximity labeling and CRISPR knock-in technologies, here we map the proteomic landscape of the human ER and nuclear envelope. Spatial proteomics reveals enrichments of proteins into ER tubules, sheets, and nuclear envelope. We uncover an ER-enriched actin-binding protein, Calmin (CLMN), and define it as an ER-actin tether that localizes to focal adhesions adjacent to ER tubules. CLMN depletion perturbs focal adhesion disassembly, actin dynamics, and cell movement. Mechanistically, CLMN-depleted cells also exhibit defects in calcium signaling near ER-actin interfaces, suggesting CLMN promotes calcium signaling near adhesions to facilitate their disassembly. Collectively, we map the sub-organelle proteome landscape of the ER, identify CLMN as an ER-actin tether, and describe a non-canonical mechanism by which ER tubules engage actin to regulate cell migration.
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Affiliation(s)
- Holly Merta
- Department of Cell Biology, UT Southwestern Medical Center, Dallas TX 75390
| | - Tadamoto Isogai
- Lyda Hill Department of Bioinformatics and Cecil H. and Ida Green Center for Systems Biology, UT Southwestern Medical Center, Dallas TX 75390
| | - Blessy Paul
- Department of Cell Biology, UT Southwestern Medical Center, Dallas TX 75390
| | - Gaudenz Danuser
- Department of Cell Biology, UT Southwestern Medical Center, Dallas TX 75390
- Lyda Hill Department of Bioinformatics and Cecil H. and Ida Green Center for Systems Biology, UT Southwestern Medical Center, Dallas TX 75390
| | - W Mike Henne
- Department of Cell Biology, UT Southwestern Medical Center, Dallas TX 75390
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4
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Xiang Y, Lyu R, Hu J. Oligomeric scaffolding for curvature generation by ER tubule-forming proteins. Nat Commun 2023; 14:2617. [PMID: 37147312 PMCID: PMC10162974 DOI: 10.1038/s41467-023-38294-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2022] [Accepted: 04/24/2023] [Indexed: 05/07/2023] Open
Abstract
The reticulons and receptor expression-enhancing proteins (REEPs) in the endoplasmic reticulum (ER) are necessary and sufficient for generating ER tubules. However, the mechanism of curvature generation remains elusive. Here, we systematically analyze components of the REEP family based on AI-predicted structures. In yeast REEP Yop1p, TM1/2 and TM3/4 form hairpins and TM2-4 exist as a bundle. Site-directed cross-linking reveals that TM2 and TM4 individually mediate homotypic dimerization, allowing further assembly into a curved shape. Truncated Yop1p lacking TM1 (equivalent to REEP1) retains the curvature-generating capability, undermining the role of the intrinsic wedge. Unexpectedly, both REEP1 and REEP5 fail to replace Yop1p in the maintenance of ER morphology, mostly due to a subtle difference in oligomerization tendency, which involves not only the TM domains, but also the TM-connecting cytosolic loop and previously neglected C-terminal helix. Several hereditary spastic paraplegia-causing mutations in REEP1 appear at the oligomeric interfaces identified here, suggesting compromised self-association of REEP as a pathogenic mechanism. These results indicate that membrane curvature stabilization by integral membrane proteins is dominantly achieved by curved, oligomeric scaffolding.
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Affiliation(s)
- Yun Xiang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100101, China
| | - Rui Lyu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100101, China
| | - Junjie Hu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.
- University of Chinese Academy of Sciences, Beijing, 100101, China.
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5
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Wang Y, Li Z, Wang X, Zhao Z, Jiao L, Liu R, Wang K, Ma R, Yang Y, Chen G, Wang Y, Bian X. Insights into membrane association of the SMP domain of extended synaptotagmin. Nat Commun 2023; 14:1504. [PMID: 36932127 PMCID: PMC10023780 DOI: 10.1038/s41467-023-37202-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 03/06/2023] [Indexed: 03/19/2023] Open
Abstract
The Synaptotagmin-like Mitochondrial-lipid-binding Protein (SMP) domain is a newly identified lipid transfer module present in proteins that regulate lipid homeostasis at membrane contact sites (MCSs). However, how the SMP domain associates with the membrane to extract and unload lipids is unclear. Here, we performed in vitro DNA brick-assisted lipid transfer assays and in silico molecular dynamics simulations to investigate the molecular basis of the membrane association by the SMP domain of extended synaptotagmin (E-Syt), which tethers the tubular endoplasmic reticulum (ER) to the plasma membrane (PM). We demonstrate that the SMP domain uses its tip region to recognize the extremely curved subdomain of tubular ER and the acidic-lipid-enriched PM for highly efficient lipid transfer. Supporting these findings, disruption of these mechanisms results in a defect in autophagosome biogenesis contributed by E-Syt. Our results suggest a model that provides a coherent picture of the action of the SMP domain at MCSs.
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Affiliation(s)
- Yunyun Wang
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Frontiers Science Center for Cell Responses, Nankai University, Tianjin, China
| | - Zhenni Li
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Frontiers Science Center for Cell Responses, Nankai University, Tianjin, China
| | - Xinyu Wang
- College of Life Sciences, Nankai University, Tianjin, China
| | - Ziyuan Zhao
- College of Life Sciences, Nankai University, Tianjin, China
| | - Li Jiao
- College of Life Sciences, Nankai University, Tianjin, China
| | - Ruming Liu
- College of Life Sciences, Nankai University, Tianjin, China
| | - Keying Wang
- College of Life Sciences, Zhejiang University, Hangzhou, China
| | - Rui Ma
- College of Physical Science and Technology, Xiamen University, Xiamen, China
| | - Yang Yang
- Institute of Molecular Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Guo Chen
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Frontiers Science Center for Cell Responses, Nankai University, Tianjin, China
| | - Yong Wang
- College of Life Sciences, Zhejiang University, Hangzhou, China.
- The Provincial International Science and Technology Cooperation Base on Engineering Biology, International Campus of Zhejiang University, Haining, China.
| | - Xin Bian
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Frontiers Science Center for Cell Responses, Nankai University, Tianjin, China.
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6
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Peng J, Chan C, Zhang S, Sklavounos AA, Olson ME, Scott EY, Hu Y, Rajesh V, Li BB, Chamberlain MD, Zhang S, Peng H, Wheeler AR. All-in-One digital microfluidics pipeline for proteomic sample preparation and analysis. Chem Sci 2023; 14:2887-2900. [PMID: 36937585 PMCID: PMC10016607 DOI: 10.1039/d3sc00560g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Accepted: 02/07/2023] [Indexed: 02/24/2023] Open
Abstract
Highly sensitive and reproducible analysis of samples containing low amounts of protein is restricted by sample loss and the introduction of contaminants during processing. Here, we report an All-in-One digital microfluidic (DMF) pipeline for proteomic sample reduction, alkylation, digestion, isotopic labeling and analysis. The system features end-to-end automation, with integrated thermal control for digestion, optimized droplet additives for sample manipulation and analysis, and an automated interface to liquid chromatography with tandem mass spectrometry (HPLC-MS/MS). Dimethyl labeling was integrated into the pipeline to allow for relative quantification of the trace samples at the nanogram level, and the new pipeline was applied to evaluating cancer cell lines and cancer tissue samples. Several known proteins (including HSP90AB1, HSPB1, LDHA, ENO1, PGK1, KRT18, and AKR1C2) and pathways were observed between model breast cancer cell lines related to hormone response, cell metabolism, and cell morphology. Furthermore, differentially quantified proteins (such as PGS2, UGDH, ASPN, LUM, COEA1, and PRELP) were found in comparisons of healthy and cancer breast tissues, suggesting potential utility of the All-in-One pipeline for the emerging application of proteomic cancer sub-typing. In sum, the All-in-One pipeline represents a powerful new tool for automated proteome processing and analysis, with the potential to be useful for evaluating mass-limited samples for a wide range of applications.
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Affiliation(s)
- Jiaxi Peng
- Department of Chemistry, University of Toronto 80 St. George Street Toronto ON M5S 3H6 Canada +1-416-946-3865 +1-416-946-3866
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto 160 College Street Toronto ON M5S 3E1 Canada
- Institute of Biomedical Engineering, University of Toronto 164 College Street Toronto ON M5S 3G9 Canada
| | - Calvin Chan
- Department of Chemistry, University of Toronto 80 St. George Street Toronto ON M5S 3H6 Canada +1-416-946-3865 +1-416-946-3866
| | - Shuailong Zhang
- Department of Chemistry, University of Toronto 80 St. George Street Toronto ON M5S 3H6 Canada +1-416-946-3865 +1-416-946-3866
- School of Mechatronical Engineering, Beijing Institute of Technology Beijing 100081 China
- Beijing Advanced Innovation Center for Intelligent Robots and Systems, Beijing Institute of Technology Beijing 100081 China
| | - Alexandros A Sklavounos
- Department of Chemistry, University of Toronto 80 St. George Street Toronto ON M5S 3H6 Canada +1-416-946-3865 +1-416-946-3866
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto 160 College Street Toronto ON M5S 3E1 Canada
| | - Maxwell E Olson
- Department of Chemistry, University of Toronto 80 St. George Street Toronto ON M5S 3H6 Canada +1-416-946-3865 +1-416-946-3866
| | - Erica Y Scott
- Department of Chemistry, University of Toronto 80 St. George Street Toronto ON M5S 3H6 Canada +1-416-946-3865 +1-416-946-3866
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto 160 College Street Toronto ON M5S 3E1 Canada
- Institute of Biomedical Engineering, University of Toronto 164 College Street Toronto ON M5S 3G9 Canada
| | - Yechen Hu
- Department of Chemistry, University of Toronto 80 St. George Street Toronto ON M5S 3H6 Canada +1-416-946-3865 +1-416-946-3866
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto 160 College Street Toronto ON M5S 3E1 Canada
- Institute of Biomedical Engineering, University of Toronto 164 College Street Toronto ON M5S 3G9 Canada
| | - Vigneshwar Rajesh
- Department of Chemistry, University of Toronto 80 St. George Street Toronto ON M5S 3H6 Canada +1-416-946-3865 +1-416-946-3866
| | - Bingyu B Li
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto 160 College Street Toronto ON M5S 3E1 Canada
- Institute of Biomedical Engineering, University of Toronto 164 College Street Toronto ON M5S 3G9 Canada
| | - M Dean Chamberlain
- Department of Chemistry, University of Toronto 80 St. George Street Toronto ON M5S 3H6 Canada +1-416-946-3865 +1-416-946-3866
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto 160 College Street Toronto ON M5S 3E1 Canada
- Institute of Biomedical Engineering, University of Toronto 164 College Street Toronto ON M5S 3G9 Canada
- Saskatchewan Cancer Agency, University of Saskatchewan 107 Wiggins Road Saskatoon SK S7N 5E5 Canada
| | - Shen Zhang
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital 600 University Avenue Toronto ON M5G 1X5 Canada
- Clinical Research Center for Reproduction and Genetics in Hunan Province, Reproductive and Genetic Hospital of CITIC-XIANGYA Changsha Hunan 410000 China
| | - Hui Peng
- Department of Chemistry, University of Toronto 80 St. George Street Toronto ON M5S 3H6 Canada +1-416-946-3865 +1-416-946-3866
- School of Environment, University of Toronto 33 Willcocks Street Toronto ON M5S 3E8 Canada
| | - Aaron R Wheeler
- Department of Chemistry, University of Toronto 80 St. George Street Toronto ON M5S 3H6 Canada +1-416-946-3865 +1-416-946-3866
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto 160 College Street Toronto ON M5S 3E1 Canada
- Institute of Biomedical Engineering, University of Toronto 164 College Street Toronto ON M5S 3G9 Canada
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7
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Arruda AP, Parlakgül G. Endoplasmic Reticulum Architecture and Inter-Organelle Communication in Metabolic Health and Disease. Cold Spring Harb Perspect Biol 2023; 15:cshperspect.a041261. [PMID: 35940911 PMCID: PMC9899651 DOI: 10.1101/cshperspect.a041261] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The endoplasmic reticulum (ER) is a key organelle involved in the regulation of lipid and glucose metabolism, proteostasis, Ca2+ signaling, and detoxification. The structural organization of the ER is very dynamic and complex, with distinct subdomains such as the nuclear envelope and the peripheral ER organized into ER sheets and tubules. ER also forms physical contact sites with all other cellular organelles and with the plasma membrane. Both form and function of the ER are highly adaptive, with a potent capacity to respond to transient changes in environmental cues such as nutritional fluctuations. However, under obesity-induced chronic stress, the ER fails to adapt, leading to ER dysfunction and the development of metabolic pathologies such as insulin resistance and fatty liver disease. Here, we discuss how the remodeling of ER structure and contact sites with other organelles results in diversification of metabolic function and how perturbations to this structural flexibility by chronic overnutrition contribute to ER dysfunction and metabolic pathologies in obesity.
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Affiliation(s)
- Ana Paula Arruda
- Department of Nutritional Sciences and Toxicology, University of California Berkeley, Berkeley, California 94720, USA.,Chan Zuckerberg Biohub, San Francisco, California 94158, USA
| | - Güneş Parlakgül
- Department of Nutritional Sciences and Toxicology, University of California Berkeley, Berkeley, California 94720, USA.,Sabri Ülker Center for Metabolic Research and Department of Molecular Metabolism, Harvard T.H. Chan School of Public Health, Boston, Massachusetts 02115, USA
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8
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Sandoz PA, Denhardt-Eriksson RA, Abrami L, Abriata LA, Spreemann G, Maclachlan C, Ho S, Kunz B, Hess K, Knott G, S Mesquita F, Hatzimanikatis V, van der Goot FG. Dynamics of CLIMP-63 S-acylation control ER morphology. Nat Commun 2023; 14:264. [PMID: 36650170 PMCID: PMC9844198 DOI: 10.1038/s41467-023-35921-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 01/06/2023] [Indexed: 01/19/2023] Open
Abstract
The complex architecture of the endoplasmic reticulum (ER) comprises distinct dynamic features, many at the nanoscale, that enable the coexistence of the nuclear envelope, regions of dense sheets and a branched tubular network that spans the cytoplasm. A key player in the formation of ER sheets is cytoskeleton-linking membrane protein 63 (CLIMP-63). The mechanisms by which CLIMP-63 coordinates ER structure remain elusive. Here, we address the impact of S-acylation, a reversible post-translational lipid modification, on CLIMP-63 cellular distribution and function. Combining native mass-spectrometry, with kinetic analysis of acylation and deacylation, and data-driven mathematical modelling, we obtain in-depth understanding of the CLIMP-63 life cycle. In the ER, it assembles into trimeric units. These occasionally exit the ER to reach the plasma membrane. However, the majority undergoes S-acylation by ZDHHC6 in the ER where they further assemble into highly stable super-complexes. Using super-resolution microscopy and focused ion beam electron microscopy, we show that CLIMP-63 acylation-deacylation controls the abundance and fenestration of ER sheets. Overall, this study uncovers a dynamic lipid post-translational regulation of ER architecture.
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Affiliation(s)
- Patrick A Sandoz
- Global Health Institute, School of Life Sciences, EPFL, Lausanne, Switzerland
| | | | - Laurence Abrami
- Global Health Institute, School of Life Sciences, EPFL, Lausanne, Switzerland
| | - Luciano A Abriata
- Laboratory for Biomolecular Modelling, Institute of Bioengineering, EPFL and Swiss Institute of Bioinformatics, Lausanne, Switzerland.,Protein Production and Structure Core Facility, School of Life Sciences, EPFL, Lausanne, Switzerland
| | | | | | - Sylvia Ho
- Global Health Institute, School of Life Sciences, EPFL, Lausanne, Switzerland
| | - Béatrice Kunz
- Global Health Institute, School of Life Sciences, EPFL, Lausanne, Switzerland
| | - Kathryn Hess
- Brain Mind Institute, EPFL, Lausanne, Switzerland
| | - Graham Knott
- BioEM Facility, School of Life Sciences, EPFL, Lausanne, Switzerland
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9
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Jeyasimman D, Ercan B, Dharmawan D, Naito T, Sun J, Saheki Y. PDZD-8 and TEX-2 regulate endosomal PI(4,5)P 2 homeostasis via lipid transport to promote embryogenesis in C. elegans. Nat Commun 2021; 12:6065. [PMID: 34663803 PMCID: PMC8523718 DOI: 10.1038/s41467-021-26177-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 09/22/2021] [Indexed: 11/10/2022] Open
Abstract
Different types of cellular membranes have unique lipid compositions that are important for their functional identity. PI(4,5)P2 is enriched in the plasma membrane where it contributes to local activation of key cellular events, including actomyosin contraction and cytokinesis. However, how cells prevent PI(4,5)P2 from accumulating in intracellular membrane compartments, despite constant intermixing and exchange of lipid membranes, is poorly understood. Using the C. elegans early embryo as our model system, we show that the evolutionarily conserved lipid transfer proteins, PDZD-8 and TEX-2, act together with the PI(4,5)P2 phosphatases, OCRL-1 and UNC-26/synaptojanin, to prevent the build-up of PI(4,5)P2 on endosomal membranes. In the absence of these four proteins, large amounts of PI(4,5)P2 accumulate on endosomes, leading to embryonic lethality due to ectopic recruitment of proteins involved in actomyosin contractility. PDZD-8 localizes to the endoplasmic reticulum and regulates endosomal PI(4,5)P2 levels via its lipid harboring SMP domain. Accumulation of PI(4,5)P2 on endosomes is accompanied by impairment of their degradative capacity. Thus, cells use multiple redundant systems to maintain endosomal PI(4,5)P2 homeostasis.
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Affiliation(s)
- Darshini Jeyasimman
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
| | - Bilge Ercan
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
| | - Dennis Dharmawan
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
| | - Tomoki Naito
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
| | - Jingbo Sun
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
| | - Yasunori Saheki
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore.
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, 860-8556, Japan.
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10
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Hai L, Shi X, Wang Q. Attenuated T Cell Responses Are Associated With the Blockade of Cerebral Malaria Development by YOP1-Deficient Plasmodium berghei ANKA. Front Immunol 2021; 12:642585. [PMID: 34025654 PMCID: PMC8134684 DOI: 10.3389/fimmu.2021.642585] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 04/21/2021] [Indexed: 11/13/2022] Open
Abstract
Reticulon and the REEP family of proteins stabilize the high curvature of endoplasmic reticulum tubules. The REEP5 homolog in Plasmodium, Plasmodium berghei YOP1 (PbYOP1), plays an important role in the erythrocytic cycle of the P. berghei ANKA and the pathogenesis of experimental cerebral malaria (ECM), but the mechanisms are largely unknown. Here, we show that protection from ECM in Pbyop1Δ-infected mice is associated with reduced intracerebral Th1 accumulation, decreased expression of pro-inflammatory cytokines and chemokines, and attenuated pathologies in the brainstem, though the total number of CD4+ and CD8+ T cells sequestered in the brain are not reduced. Expression of adhesive molecules on brain endothelial cells, including ICAM-1, VCAM-1, and CD36, are decreased, particularly in the brainstem, where fatal pathology is always induced during ECM. Subsequently, CD8+ T cell-mediated cell apoptosis in the brain is compromised. These findings suggest that Pbyop1Δ parasites can be a useful tool for mechanistic investigation of cerebral malaria pathogenesis.
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Affiliation(s)
- Lei Hai
- Department of Immunology, School of Basic Medical Sciences, and Tianjin Key Laboratory of Cellular and Molecular Immunology, Key Laboratory of Immune Microenvironment and Diseases of Educational Ministry of China, Tianjin Medical University, Tianjin, China
| | - Xiaoyu Shi
- Department of Immunology, School of Basic Medical Sciences, and Tianjin Key Laboratory of Cellular and Molecular Immunology, Key Laboratory of Immune Microenvironment and Diseases of Educational Ministry of China, Tianjin Medical University, Tianjin, China
| | - Qian Wang
- Department of Immunology, School of Basic Medical Sciences, and Tianjin Key Laboratory of Cellular and Molecular Immunology, Key Laboratory of Immune Microenvironment and Diseases of Educational Ministry of China, Tianjin Medical University, Tianjin, China.,National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
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11
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Chen F, Yan B, Ren J, Lyu R, Wu Y, Guo Y, Li D, Zhang H, Hu J. FIT2 organizes lipid droplet biogenesis with ER tubule-forming proteins and septins. J Cell Biol 2021; 220:211999. [PMID: 33861319 PMCID: PMC8056755 DOI: 10.1083/jcb.201907183] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Revised: 12/29/2020] [Accepted: 02/09/2021] [Indexed: 12/20/2022] Open
Abstract
Lipid droplets (LDs) are critical for lipid storage and energy metabolism. LDs form in the endoplasmic reticulum (ER). However, the molecular basis for LD biogenesis remains elusive. Here, we show that fat storage–inducing transmembrane protein 2 (FIT2) interacts with ER tubule-forming proteins Rtn4 and REEP5. The association is mainly transmembrane domain based and stimulated by oleic acid. Depletion of ER tubule-forming proteins decreases the number and size of LDs in cells and Caenorhabditis elegans, mimicking loss of FIT2. Through cytosolic loops, FIT2 binds to cytoskeletal protein septin 7, an interaction that is also required for normal LD biogenesis. Depletion of ER tubule-forming proteins or septins delays nascent LD formation. In addition, FIT2-interacting proteins are up-regulated during adipocyte differentiation, and ER tubule-forming proteins, septin 7, and FIT2 are transiently enriched at LD formation sites. Thus, FIT2-mediated nascent LD biogenesis is facilitated by ER tubule-forming proteins and septins.
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Affiliation(s)
- Fang Chen
- National Laboratory of Biomacromolecules, Chinese Academy of Sciences Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Bing Yan
- National Laboratory of Biomacromolecules, Chinese Academy of Sciences Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Jie Ren
- National Laboratory of Biomacromolecules, Chinese Academy of Sciences Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Rui Lyu
- National Laboratory of Biomacromolecules, Chinese Academy of Sciences Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Yanfang Wu
- National Laboratory of Biomacromolecules, Chinese Academy of Sciences Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Yuting Guo
- National Laboratory of Biomacromolecules, Chinese Academy of Sciences Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Dong Li
- National Laboratory of Biomacromolecules, Chinese Academy of Sciences Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Hong Zhang
- National Laboratory of Biomacromolecules, Chinese Academy of Sciences Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Junjie Hu
- National Laboratory of Biomacromolecules, Chinese Academy of Sciences Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
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12
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Ganesan S, Tavassoli M, Shabits BN, Zaremberg V. Tubular ER Associates With Diacylglycerol-Rich Structures During Lipid Droplet Consumption. Front Cell Dev Biol 2020; 8:700. [PMID: 32850820 PMCID: PMC7403446 DOI: 10.3389/fcell.2020.00700] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Accepted: 07/09/2020] [Indexed: 11/13/2022] Open
Abstract
Growth resumption from stationary phase in Saccharomyces cerevisiae, is characterized by lipid droplet (LD) consumption and channeling of lipid precursors toward synthesis of membranes. We have previously determined that triacylglycerol lipolysis contributes to a pool of diacylglycerol (DAG) associated with the yeast vacuole that is enriched in structures that are in close proximity to LDs. In this study we have monitored these structures using a DAG sensor fused to GFP during isolation of LDs. A unique fraction containing the DAG sensor, with low presence of LDs, was identified. Membranes enriched in the DAG probe were obtained by immunoaffinity purification using a GFP nanobody, and the associated proteome was investigated by mass spectrometry. It was determined this LD-associated fraction was enriched in proteins known to shape the tubular endoplasmic reticulum (ER) like Yop1, Sey1, Rtn1, and Rtn2. Consistently, cells lacking three of these proteins (rtn1Δ rtn2Δ yop1Δ) exhibited delayed LD consumption, larger LDs and abnormal LD distribution. In addition, the triple mutant displayed aberrant localization of the DAG sensor after 5 h of growth resumption from stationary phase. Manipulation of DAG levels by overexpression of the DAG kinase Dgk1, impacted localization of the DAG probe and affected fitness of the triple mutant. Altogether these results link LD consumption to tubular ER expansion as a gateway of lipid precursors that otherwise accumulate in vacuolar associated membranes or other internal compartments. Furthermore, conversion of DAG to phosphatidic acid (PA) in the absence of a functional tubular ER was toxic to cells, suggesting the ratio of PA to DAG is critical to allow growth progression.
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Affiliation(s)
| | - Marjan Tavassoli
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Brittney N Shabits
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Vanina Zaremberg
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
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13
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Nthiga TM, Kumar Shrestha B, Sjøttem E, Bruun J, Bowitz Larsen K, Bhujabal Z, Lamark T, Johansen T. CALCOCO1 acts with VAMP-associated proteins to mediate ER-phagy. EMBO J 2020; 39:e103649. [PMID: 32525583 PMCID: PMC7396842 DOI: 10.15252/embj.2019103649] [Citation(s) in RCA: 91] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 05/01/2020] [Accepted: 05/06/2020] [Indexed: 12/20/2022] Open
Abstract
The endoplasmic reticulum (ER) plays important roles in protein synthesis and folding, and calcium storage. The volume of the ER and expression of its resident proteins are increased in response to nutrient stress. ER-phagy, a selective form of autophagy, is involved in the degradation of the excess components of the ER to restore homeostasis. Six ER-resident proteins have been identified as ER-phagy receptors so far. In this study, we have identified CALCOCO1 as a novel ER-phagy receptor for the degradation of the tubular ER in response to proteotoxic and nutrient stress. CALCOCO1 is a homomeric protein that binds directly to ATG8 proteins via LIR- and UDS-interacting region (UIR) motifs acting co-dependently. CALCOCO1-mediated ER-phagy requires interaction with VAMP-associated proteins VAPA and VAPB on the ER membranes via a conserved FFAT-like motif. Depletion of CALCOCO1 causes expansion of the ER and inefficient basal autophagy flux. Unlike the other ER-phagy receptors, CALCOCO1 is peripherally associated with the ER. Therefore, we define CALCOCO1 as a soluble ER-phagy receptor.
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Affiliation(s)
- Thaddaeus Mutugi Nthiga
- Department of Medical BiologyMolecular Cancer Research GroupUniversity of Tromsø—The Arctic University of NorwayTromsøNorway
| | - Birendra Kumar Shrestha
- Department of Medical BiologyMolecular Cancer Research GroupUniversity of Tromsø—The Arctic University of NorwayTromsøNorway
| | - Eva Sjøttem
- Department of Medical BiologyMolecular Cancer Research GroupUniversity of Tromsø—The Arctic University of NorwayTromsøNorway
| | - Jack‐Ansgar Bruun
- Department of Medical BiologyMolecular Cancer Research GroupUniversity of Tromsø—The Arctic University of NorwayTromsøNorway
| | - Kenneth Bowitz Larsen
- Department of Medical BiologyMolecular Cancer Research GroupUniversity of Tromsø—The Arctic University of NorwayTromsøNorway
| | - Zambarlal Bhujabal
- Department of Medical BiologyMolecular Cancer Research GroupUniversity of Tromsø—The Arctic University of NorwayTromsøNorway
| | - Trond Lamark
- Department of Medical BiologyMolecular Cancer Research GroupUniversity of Tromsø—The Arctic University of NorwayTromsøNorway
| | - Terje Johansen
- Department of Medical BiologyMolecular Cancer Research GroupUniversity of Tromsø—The Arctic University of NorwayTromsøNorway
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14
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Shi X, Hai L, Govindasamy K, Gao J, Coppens I, Hu J, Wang Q, Bhanot P. A Plasmodium homolog of ER tubule-forming proteins is required for parasite virulence. Mol Microbiol 2020; 114:454-467. [PMID: 32432369 DOI: 10.1111/mmi.14526] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 05/04/2020] [Accepted: 05/05/2020] [Indexed: 01/27/2023]
Abstract
Reticulon and REEP family of proteins stabilize the high curvature of endoplasmic reticulum (ER) tubules. Plasmodium berghei Yop1 (PbYop1) is a REEP5 homolog in Plasmodium. Here, we characterize its function using a gene-knockout (Pbyop1∆). Pbyop1∆ asexual stage parasites display abnormal ER architecture and an enlarged digestive vacuole. The erythrocytic cycle of Pbyop1∆ parasites is severely attenuated and the incidence of experimental cerebral malaria is significantly decreased in Pbyop1∆-infected mice. Pbyop1∆ sporozoites have reduced speed, are slower to invade host cells but give rise to equal numbers of infected HepG2 cells, as WT sporozoites. We propose that PbYOP1's disruption may lead to defects in trafficking and secretion of a subset of proteins required for parasite development and invasion of erythrocytes. Furthermore, the maintenance of ER morphology in different parasite stages is likely to depend on different proteins.
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Affiliation(s)
- Xiaoyu Shi
- Department of Immunology, School of Basic Medical Sciences, Tianjin Key Laboratory of Cellular and Molecular Immunology, Key Laboratory of Immune Microenvironment and Diseases of Educational Ministry of China, Tianjin Medical University, Tianjin, China
| | - Lei Hai
- Department of Immunology, School of Basic Medical Sciences, Tianjin Key Laboratory of Cellular and Molecular Immunology, Key Laboratory of Immune Microenvironment and Diseases of Educational Ministry of China, Tianjin Medical University, Tianjin, China
| | - Kavitha Govindasamy
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers New Jersey Medical School, Newark, NJ, USA
| | - Jian Gao
- Department of Immunology, School of Basic Medical Sciences, Tianjin Key Laboratory of Cellular and Molecular Immunology, Key Laboratory of Immune Microenvironment and Diseases of Educational Ministry of China, Tianjin Medical University, Tianjin, China
| | - Isabelle Coppens
- Department of Molecular Microbiology and Immunology, The Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD, USA
| | - Junjie Hu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Qian Wang
- Department of Immunology, School of Basic Medical Sciences, Tianjin Key Laboratory of Cellular and Molecular Immunology, Key Laboratory of Immune Microenvironment and Diseases of Educational Ministry of China, Tianjin Medical University, Tianjin, China.,National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Purnima Bhanot
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers New Jersey Medical School, Newark, NJ, USA
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15
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Yamanaka T, Nishiyama R, Shimogori T, Nukina N. Proteomics-Based Approach Identifies Altered ER Domain Properties by ALS-Linked VAPB Mutation. Sci Rep 2020; 10:7610. [PMID: 32376919 PMCID: PMC7203144 DOI: 10.1038/s41598-020-64517-z] [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: 12/29/2019] [Accepted: 04/17/2020] [Indexed: 12/13/2022] Open
Abstract
An ER transmembrane protein, vesicle-associated membrane protein-associated protein B (VAPB), binds to several organelle-resident membrane proteins to mediate ER-organelle tethering. Mutation in amyotrophic lateral sclerosis (ALS) induces protein misfolding and aggregation, leading to ER disorganization. Gain or loss of function is suggested for VAPB mutation, however comprehensive study focusing on VAPB-ER domain has yet been performed. We here conducted proteomic characterization of the ER containing VAPB and its ALS-linked P56S mutant. For this purpose, we first optimized the proteomics of different ER domains immuno-isolated from cultured cells, and identified ER sheet- and tubule-specific proteomes. By using these as references, we found that VAPB-ER proteome had intermediate ER domain properties but its tubular property was specifically decreased by its mutation. Biochemical, immunofluorescence and proximity ligation assays suggested this was mediated by delocalization of VAPB from ER tubules. The VAPB-ER proteomics further suggested reduced incorporation of multiple proteins located in different organelles, which was confirmed by proximity ligation assay. Taken together, our proteomics-based approach indicates altered ER domain properties and impaired ER-organelle tethering by VAPB mutation.
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Affiliation(s)
- Tomoyuki Yamanaka
- Laboratory of Structural Neuropathology, Doshisha University Graduate School of Brain Science, Kyoto, Japan.
| | - Risa Nishiyama
- Laboratory of Structural Neuropathology, Doshisha University Graduate School of Brain Science, Kyoto, Japan
| | - Tomomi Shimogori
- Molecular Mechanisms of Brain Development, RIKEN Center for Brain Science, Saitama, 351-0198, Japan
| | - Nobuyuki Nukina
- Laboratory of Structural Neuropathology, Doshisha University Graduate School of Brain Science, Kyoto, Japan.
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16
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Abstract
Subcellular proteomics include, in its experimental workflow, steps aimed at purifying organelles. The purity of the subcellular fraction should be assessed before mass spectrometry analysis, in order to confidently conclude the presence of associated specific proteoforms, deepening the knowledge of its biological function. In this chapter, a protocol for isolating endoplasmic reticulum (ER) and purity assessment is reported, and it precedes the proteomic analysis through a gel-free/label-free proteomic approach. Dysfunction of quality-control mechanisms of protein metabolism in ER leads to ER stress. Additionally, ER, which is a calcium-storage organelle, is responsible for signaling and homeostatic function, and calcium homeostasis is required for plant tolerance. With such predominant cell functions, effective protocols to fractionate highly purified ER are needed. Here, isolation methods and purity assessments of ER are described. In addition, a gel-free/label-free proteomic approach of ER is presented.
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Affiliation(s)
- Xin Wang
- College of Agronomy and Biotechnology, China Agricultural University, Beijing, China
| | - Setsuko Komatsu
- Faculty of Environmental and Information Sciences, Fukui University of Technology, Fukui, Japan.
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17
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18
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Beal DM, Bastow EL, Staniforth GL, von der Haar T, Freedman RB, Tuite MF. Quantitative Analyses of the Yeast Oxidative Protein Folding Pathway In Vitro and In Vivo. Antioxid Redox Signal 2019; 31:261-274. [PMID: 30880408 PMCID: PMC6602113 DOI: 10.1089/ars.2018.7615] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 03/14/2019] [Accepted: 03/14/2019] [Indexed: 12/11/2022]
Abstract
Aims: Efficient oxidative protein folding (OPF) in the endoplasmic reticulum (ER) is a key requirement of the eukaryotic secretory pathway. In particular, protein folding linked to the formation of disulfide bonds, an activity dependent on the enzyme protein disulfide isomerase (PDI), is crucial. For the de novo formation of disulfide bonds, reduced PDI must be reoxidized by an ER-located oxidase (ERO1). Despite some knowledge of this pathway, the kinetic parameters with which these components act and the importance of specific parameters, such as PDI reoxidation by Ero1, for the overall performance of OPF in vivo remain poorly understood. Results: We established an in vitro system using purified yeast (Saccharomyces cerevisiae) PDI (Pdi1p) and ERO1 (Ero1p) to investigate OPF. This necessitated the development of a novel reduction/oxidation processing strategy to generate homogenously oxidized recombinant yeast Ero1p. This new methodology enabled the quantitative assessment of the interaction of Pdi1p and Ero1p in vitro by measuring oxygen consumption and reoxidation of reduced RNase A. The resulting quantitative data were then used to generate a simple model that can describe the oxidizing capacity of Pdi1p and Ero1p in vitro and predict the in vivo effect of modulation of the levels of these proteins. Innovation: We describe a model that can be used to explore the OPF pathway and its control in a quantitative way. Conclusion: Our study informs and provides new insights into how OPF works at a molecular level and provides a platform for the design of more efficient heterologous protein expression systems in yeast.
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Affiliation(s)
- Dave M. Beal
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - Emma L. Bastow
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - Gemma L. Staniforth
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - Tobias von der Haar
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - Robert B. Freedman
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, United Kingdom
- School of Life Sciences, Gibbet Hill Campus, University of Warwick, Coventry, United Kingdom
| | - Mick F. Tuite
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, United Kingdom
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19
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Atlastin-mediated membrane tethering is critical for cargo mobility and exit from the endoplasmic reticulum. Proc Natl Acad Sci U S A 2019; 116:14029-14038. [PMID: 31239341 PMCID: PMC6628656 DOI: 10.1073/pnas.1908409116] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
In the early secretory pathway, newly synthesized proteins undergo folding and modifications and then leave the ER through COPII-coated vesicles. How these processes are coordinated and maintained are important but mostly unclear. We show here that ATL, a GTPase that connects ER tubules, controls ER protein mobility and regulates cargo packaging and coat assembly of COPII vesicles. The tethering and fusion activity by ATL likely maintains tension and other necessary parameters for COPII formation in ER membranes. These findings reveal a role of ER shaping in the early secretory pathway and provide insight into behaviors of ER exportation. Endoplasmic reticulum (ER) membrane junctions are formed by the dynamin-like GTPase atlastin (ATL). Deletion of ATL results in long unbranched ER tubules in cells, and mutation of human ATL1 is linked to hereditary spastic paraplegia. Here, we demonstrate that COPII formation is drastically decreased in the periphery of ATL-deleted cells. ER export of cargo proteins becomes defective; ER exit site initiation is not affected, but many of the sites fail to recruit COPII subunits. The efficiency of cargo packaging into COPII vesicles is significantly reduced in cells lacking ATLs, or when the ER is transiently fragmented. Cargo is less mobile in the ER in the absence of ATL, but the cargo mobility and COPII formation can be restored by ATL R77A, which is capable of tethering, but not fusing, ER tubules. These findings suggest that the generation of ER junctions by ATL plays a critical role in maintaining the necessary mobility of ER contents to allow efficient packaging of cargo proteins into COPII vesicles.
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20
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Nightingale DJ, Geladaki A, Breckels LM, Oliver SG, Lilley KS. The subcellular organisation of Saccharomyces cerevisiae. Curr Opin Chem Biol 2019; 48:86-95. [PMID: 30503867 PMCID: PMC6391909 DOI: 10.1016/j.cbpa.2018.10.026] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 10/29/2018] [Accepted: 10/31/2018] [Indexed: 01/06/2023]
Abstract
Subcellular protein localisation is essential for the mechanisms that govern cellular homeostasis. The ability to understand processes leading to this phenomenon will therefore enhance our understanding of cellular function. Here we review recent developments in this field with regard to mass spectrometry, fluorescence microscopy and computational prediction methods. We highlight relative strengths and limitations of current methodologies focussing particularly on studies in the yeast Saccharomyces cerevisiae. We further present the first cell-wide spatial proteome map of S. cerevisiae, generated using hyperLOPIT, a mass spectrometry-based protein correlation profiling technique. We compare protein subcellular localisation assignments from this map, with two published fluorescence microscopy studies and show that confidence in localisation assignment is attained using multiple orthogonal methods that provide complementary data.
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Affiliation(s)
- Daniel Jh Nightingale
- Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QR, United Kingdom; Cambridge Systems Biology Centre, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1GA, United Kingdom
| | - Aikaterini Geladaki
- Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QR, United Kingdom; Cambridge Systems Biology Centre, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1GA, United Kingdom; Department of Genetics, University of Cambridge, Downing Street, Cambridge, CB2 3EH, United Kingdom
| | - Lisa M Breckels
- Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QR, United Kingdom; Cambridge Systems Biology Centre, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1GA, United Kingdom
| | - Stephen G Oliver
- Cambridge Systems Biology Centre, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1GA, United Kingdom
| | - Kathryn S Lilley
- Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QR, United Kingdom; Cambridge Systems Biology Centre, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1GA, United Kingdom.
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21
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Reciprocal regulation between lunapark and atlastin facilitates ER three-way junction formation. Protein Cell 2018; 10:510-525. [PMID: 30498943 PMCID: PMC6588657 DOI: 10.1007/s13238-018-0595-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Accepted: 10/23/2018] [Indexed: 11/12/2022] Open
Abstract
Three-way junctions are characteristic structures of the tubular endoplasmic reticulum (ER) network. Junctions are formed through atlastin (ATL)-mediated membrane fusion and stabilized by lunapark (Lnp). However, how Lnp is preferentially enriched at three-way junctions remains elusive. Here, we showed that Lnp loses its junction localization when ATLs are deleted. Reintroduction of ATL1 R77A and ATL3, which have been shown to cluster at the junctions, but not wild-type ATL1, relocates Lnp to the junctions. Mutations in the N-myristoylation site or hydrophobic residues in the coiled coil (CC1) of Lnp N-terminus (NT) cause mis-targeting of Lnp. Conversely, deletion of the lunapark motif in the C-terminal zinc finger domain, which affects the homo-oligomerization of Lnp, does not alter its localization. Purified Lnp-NT attaches to the membrane in a myristoylation-dependent manner. The mutation of hydrophobic residues in CC1 does not affect membrane association, but compromises ATL interactions. In addition, Lnp-NT inhibits ATL-mediated vesicle fusion in vitro. These results suggest that CC1 in Lnp-NT contacts junction-enriched ATLs for proper localization; subsequently, further ATL activity is limited by Lnp after the junction is formed. The proposed mechanism ensures coordinated actions of ATL and Lnp in generating and maintaining three-way junctions.
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22
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Lee M, Moon Y, Lee S, Lee C, Jun Y. Ergosterol interacts with Sey1p to promote atlastin-mediated endoplasmic reticulum membrane fusion in Saccharomyces cerevisiae. FASEB J 2018; 33:3590-3600. [PMID: 30462528 DOI: 10.1096/fj.201800779rr] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Sterols play critical roles in various membrane fusion events, including soluble NSF attachment protein receptor-mediated membrane fusion, mainly by modulating the physical properties of biologic membranes; however, it remains unclear whether they also function in atlastin-mediated endoplasmic reticulum (ER) membrane fusion. Although ergosterol, the major sterol in yeast, is essential for fusion of Sey1p (yeast atlastin)-containing liposomes with an ER-mimicking lipid composition, fusion of phosphatidylcholine/phosphatidylserine liposomes does not require sterols. Here, we examined whether sterols are important for Sey1p-mediated ER fusion in Saccharomyces cerevisiae using an in vitro ER fusion assay with isolated yeast ER microsomes. Ergosterol-specific ligands inhibited microsome fusion, indicating that ergosterol is critical for ER fusion. However, microsomes isolated from yeast strains lacking genes that encode enzymes involved in synthesis of ergosterol from lanosterol still fused, suggesting that other sterols can replace ergosterol and support Sey1p-mediated ER fusion. Importantly, disruption of sterol-binding motifs in the transmembrane regions of Sey1p markedly reduced ER fusion. Sey1p physically interacted with Erg11p and Erg4p, which function in ergosterol biosynthesis, suggesting that Sey1p recruits ergosterol-synthesizing enzymes to fusion sites and thereby enriches ergosterol, which, in turn, may recruit more Sey1p. This positive feedback loop may facilitate ER membrane fusion by concentrating fusion factors at fusion sites.-Lee, M., Moon, Y., Lee, S., Lee, C., Jun, Y. Ergosterol interacts with Sey1p to promote atlastin-mediated endoplasmic reticulum membrane fusion in Saccharomyces cerevisiae.
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Affiliation(s)
- Miriam Lee
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju, South Korea.,Silver Health Bio Research Center, Gwangju Institute of Science and Technology, Gwangju, South Korea.,Cell Logistics Research Center, Gwangju Institute of Science and Technology, Gwangju, South Korea
| | - Yeojin Moon
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju, South Korea.,Silver Health Bio Research Center, Gwangju Institute of Science and Technology, Gwangju, South Korea.,Cell Logistics Research Center, Gwangju Institute of Science and Technology, Gwangju, South Korea
| | - Sanghwa Lee
- Cell Logistics Research Center, Gwangju Institute of Science and Technology, Gwangju, South Korea.,Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju, South Korea; and
| | - Changwook Lee
- Cell Logistics Research Center, Gwangju Institute of Science and Technology, Gwangju, South Korea.,Department of Biological Sciences, School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, South Korea
| | - Youngsoo Jun
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju, South Korea.,Silver Health Bio Research Center, Gwangju Institute of Science and Technology, Gwangju, South Korea.,Cell Logistics Research Center, Gwangju Institute of Science and Technology, Gwangju, South Korea
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23
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Transmembrane E3 ligase RNF183 mediates ER stress-induced apoptosis by degrading Bcl-xL. Proc Natl Acad Sci U S A 2018; 115:E2762-E2771. [PMID: 29507230 PMCID: PMC5866564 DOI: 10.1073/pnas.1716439115] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The accumulation of misfolded proteins in the endoplasmic reticulum (ER) causes ER stress and triggers the unfolded protein response (UPR). Failure to resolve ER stress leads to apoptotic cell death via a yet unclear mechanism. Here, we show that RNF183, a membrane-spanning RING finger protein, localizes to the ER and exhibits classic E3 ligase activities. Sustained ER stress induced by different treatments increases RNF183 protein levels posttranscriptionally in an IRE1α-dependent manner. Activated IRE1 reduces the level of miR-7, which increases the stability of RNF183 transcripts. In addition, overexpression of RNF183 leads to increased apoptosis and its depletion alleviates ER stress-induced apoptosis. Furthermore, RNF183 interacts with Bcl-xL, an antiapoptotic member of the Bcl-2 family, and polyubiquitinates Bcl-xL for degradation. Thus, RNF183 plays an important role in executing programmed cell death upon prolonged ER stress, likely by inducing apoptosis through Bcl-xL.
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24
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Sec61β facilitates the maintenance of endoplasmic reticulum homeostasis by associating microtubules. Protein Cell 2017; 9:616-628. [PMID: 29168059 PMCID: PMC6019657 DOI: 10.1007/s13238-017-0492-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 11/13/2017] [Indexed: 10/25/2022] Open
Abstract
Sec61β, a subunit of the Sec61 translocon complex, is not essential in yeast and commonly used as a marker of endoplasmic reticulum (ER). In higher eukaryotes, such as Drosophila, deletion of Sec61β causes lethality, but its physiological role is unclear. Here, we show that Sec61β interacts directly with microtubules. Overexpression of Sec61β containing small epitope tags, but not a RFP tag, induces dramatic bundling of the ER and microtubule. A basic region in the cytosolic domain of Sec61β is critical for microtubule association. Depletion of Sec61β induces ER stress in both mammalian cells and Caenorhabditis elegans, and subsequent restoration of ER homeostasis correlates with the microtubule binding ability of Sec61β. Loss of Sec61β causes increased mobility of translocon complexes and reduced level of membrane-bound ribosomes. These results suggest that Sec61β may stabilize protein translocation by linking translocon complex to microtubule and provide insight into the physiological function of ER-microtubule interaction.
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