1
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Casler JC, Harper CS, White AJ, Anderson HL, Lackner LL. Mitochondria-ER-PM contacts regulate mitochondrial division and PI(4)P distribution. J Cell Biol 2024; 223:e202308144. [PMID: 38781029 PMCID: PMC11116812 DOI: 10.1083/jcb.202308144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Revised: 12/13/2023] [Accepted: 05/07/2024] [Indexed: 05/25/2024] Open
Abstract
The mitochondria-ER-cortex anchor (MECA) forms a tripartite membrane contact site between mitochondria, the endoplasmic reticulum (ER), and the plasma membrane (PM). The core component of MECA, Num1, interacts with the PM and mitochondria via two distinct lipid-binding domains; however, the molecular mechanism by which Num1 interacts with the ER is unclear. Here, we demonstrate that Num1 contains a FFAT motif in its C-terminus that interacts with the integral ER membrane protein Scs2. While dispensable for Num1's functions in mitochondrial tethering and dynein anchoring, the FFAT motif is required for Num1's role in promoting mitochondrial division. Unexpectedly, we also reveal a novel function of MECA in regulating the distribution of phosphatidylinositol-4-phosphate (PI(4)P). Breaking Num1 association with any of the three membranes it tethers results in an accumulation of PI(4)P on the PM, likely via disrupting Sac1-mediated PI(4)P turnover. This work establishes MECA as an important regulatory hub that spatially organizes mitochondria, ER, and PM to coordinate crucial cellular functions.
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Affiliation(s)
- Jason C. Casler
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Clare S. Harper
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Antoineen J. White
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Heidi L. Anderson
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Laura L. Lackner
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
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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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Pan X, Ren L, Yang Y, Xu Y, Ning L, Zhang Y, Luo H, Zou Q, Zhang Y. MCSdb, a database of proteins residing in membrane contact sites. Sci Data 2024; 11:281. [PMID: 38459036 PMCID: PMC10923927 DOI: 10.1038/s41597-024-03104-7] [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: 05/08/2023] [Accepted: 02/29/2024] [Indexed: 03/10/2024] Open
Abstract
Organelles do not act as autonomous discrete units but rather as interconnected hubs that engage in extensive communication by forming close contacts called "membrane contact sites (MCSs)". And many proteins have been identified as residing in MCS and playing important roles in maintaining and fulfilling specific functions within these microdomains. However, a comprehensive compilation of these MCS proteins is still lacking. Therefore, we developed MCSdb, a manually curated resource of MCS proteins and complexes from publications. MCSdb documents 7010 MCS protein entries and 263 complexes, involving 24 organelles and 44 MCSs across 11 species. Additionally, MCSdb orchestrates all data into different categories with multitudinous information for presenting MCS proteins. In summary, MCSdb provides a valuable resource for accelerating MCS functional interpretation and interorganelle communication deciphering.
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Affiliation(s)
- Xianrun Pan
- College of Medical Technology, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Liping Ren
- School of Healthcare Technology, Chengdu Neusoft University, Chengdu, China
| | - Yu Yang
- School of Healthcare Technology, Chengdu Neusoft University, Chengdu, China
| | - Yi Xu
- School of Life Science and Technology, University of Electronic Science and Technology of China, Chengdu, China
| | - Lin Ning
- School of Healthcare Technology, Chengdu Neusoft University, Chengdu, China
- School of Life Science and Technology, University of Electronic Science and Technology of China, Chengdu, China
| | - Yibing Zhang
- Glasgow College, University of Electronic Science and Technology of China, Chengdu, China
| | - Huaichao Luo
- Department of Clinical Laboratory, Sichuan Clinical Research Center for Cancer, Sichuan Cancer Hospital & Institute, Sichuan Cancer Center, Affiliated Cancer Hospital of University of Electronic Science and Technology of China, Chengdu, China.
| | - Quan Zou
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, China.
| | - Yang Zhang
- Innovative Institute of Chinese Medicine and Pharmacy, Academy for Interdiscipline, Chengdu University of Traditional Chinese Medicine, Chengdu, China.
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4
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Nenadic A, Zaman MF, Johansen J, Volpiana MW, Beh CT. Increased Phospholipid Flux Bypasses Overlapping Essential Requirements for the Yeast Sac1p Phosphoinositide Phosphatase and ER-PM Membrane Contact Sites. J Biol Chem 2023; 299:105092. [PMID: 37507017 PMCID: PMC10470028 DOI: 10.1016/j.jbc.2023.105092] [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: 08/21/2022] [Revised: 07/13/2023] [Accepted: 07/17/2023] [Indexed: 07/30/2023] Open
Abstract
In budding yeast cells, much of the inner surface of the plasma membrane (PM) is covered with the endoplasmic reticulum (ER). This association is mediated by seven ER membrane proteins that confer cortical ER-PM association at membrane contact sites (MCSs). Several of these membrane "tether" proteins are known to physically interact with the phosphoinositide phosphatase Sac1p. However, it is unclear how or if these interactions are necessary for their interdependent functions. We find that SAC1 inactivation in cells lacking the homologous synaptojanin-like genes INP52 and INP53 results in a significant increase in cortical ER-PM MCSs. We show in sac1Δ, sac1tsinp52Δ inp53Δ, or Δ-super-tether (Δ-s-tether) cells lacking all seven ER-PM tethering genes that phospholipid biosynthesis is disrupted and phosphoinositide distribution is altered. Furthermore, SAC1 deletion in Δ-s-tether cells results in lethality, indicating a functional overlap between SAC1 and ER-PM tethering genes. Transcriptomic profiling indicates that SAC1 inactivation in either Δ-s-tether or inp52Δ inp53Δ cells induces an ER membrane stress response and elicits phosphoinositide-dependent changes in expression of autophagy genes. In addition, by isolating high-copy suppressors that rescue sac1Δ Δ-s-tether lethality, we find that key phospholipid biosynthesis genes bypass the overlapping function of SAC1 and ER-PM tethers and that overexpression of the phosphatidylserine/phosphatidylinositol-4-phosphate transfer protein Osh6 also provides limited suppression. Combined with lipidomic analysis and determinations of intracellular phospholipid distributions, these results suggest that Sac1p and ER phospholipid flux controls lipid distribution to drive Osh6p-dependent phosphatidylserine/phosphatidylinositol-4-phosphate counter-exchange at ER-PM MCSs.
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Affiliation(s)
- Aleksa Nenadic
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Mohammad F Zaman
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Jesper Johansen
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Matthew W Volpiana
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Christopher T Beh
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada; Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, British Columbia, Canada.
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5
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Stump AL, Rioux DJ, Albright R, Melki GL, Prosser DC. Yeast Models of Amyotrophic Lateral Sclerosis Type 8 Mimic Phenotypes Seen in Mammalian Cells Expressing Mutant VAPB P56S. Biomolecules 2023; 13:1147. [PMID: 37509182 PMCID: PMC10377116 DOI: 10.3390/biom13071147] [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: 05/14/2023] [Revised: 07/09/2023] [Accepted: 07/17/2023] [Indexed: 07/30/2023] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a complex neurodegenerative disease that results in the loss of motor neurons and can occur sporadically or due to genetic mutations. Among the 30 genes linked to familial ALS, a P56S mutation in VAPB, an ER-resident protein that functions at membrane contact sites, causes ALS type 8. Mammalian cells expressing VAPBP56S have distinctive phenotypes, including ER collapse, protein and/or membrane-containing inclusions, and sensitivity to ER stress. VAPB is conserved through evolution and has two homologs in budding yeast, SCS2 and SCS22. Previously, a humanized version of SCS2 bearing disease-linked mutations was described, and it caused Scs2-containing inclusions when overexpressed in yeast. Here, we describe a yeast model for ALS8 in which the two SCS genes are deleted and replaced with a single chromosomal copy of either wild-type or mutant yeast SCS2 or human VAPB expressed from the SCS2 promoter. These cells display ER collapse, the formation of inclusion-like structures, and sensitivity to tunicamycin, an ER stress-inducing drug. Based on the phenotypic similarity to mammalian cells expressing VAPBP56S, we propose that these models can be used to study the molecular basis of cell death or dysfunction in ALS8. Moreover, other conserved ALS-linked genes may create opportunities for the generation of yeast models of disease.
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Affiliation(s)
- AnnaMari L. Stump
- Department of Biology, Virginia Commonwealth University, Richmond, VA 23284, USA
- VCU Life Sciences, Virginia Commonwealth University, Richmond, VA 23284, USA
| | - Daniel J. Rioux
- Department of Biology, Virginia Commonwealth University, Richmond, VA 23284, USA
- VCU Life Sciences, Virginia Commonwealth University, Richmond, VA 23284, USA
| | - Richard Albright
- Department of Biology, Virginia Commonwealth University, Richmond, VA 23284, USA
| | - Guiliano L. Melki
- Department of Biology, Virginia Commonwealth University, Richmond, VA 23284, USA
| | - Derek C. Prosser
- Department of Biology, Virginia Commonwealth University, Richmond, VA 23284, USA
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6
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Wang P, Duckney P, Gao E, Hussey PJ, Kriechbaumer V, Li C, Zang J, Zhang T. Keep in contact: multiple roles of endoplasmic reticulum-membrane contact sites and the organelle interaction network in plants. THE NEW PHYTOLOGIST 2023; 238:482-499. [PMID: 36651025 DOI: 10.1111/nph.18745] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Accepted: 12/02/2022] [Indexed: 06/17/2023]
Abstract
Functional regulation and structural maintenance of the different organelles in plants contribute directly to plant development, reproduction and stress responses. To ensure these activities take place effectively, cells have evolved an interconnected network amongst various subcellular compartments, regulating rapid signal transduction and the exchange of biomaterial. Many proteins that regulate membrane connections have recently been identified in plants, and this is the first step in elucidating both the mechanism and function of these connections. Amongst all organelles, the endoplasmic reticulum is the key structure, which likely links most of the different subcellular compartments through membrane contact sites (MCS) and the ER-PM contact sites (EPCS) have been the most intensely studied in plants. However, the molecular composition and function of plant MCS are being found to be different from other eukaryotic systems. In this article, we will summarise the most recent advances in this field and discuss the mechanism and biological relevance of these essential links in plants.
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Affiliation(s)
- Pengwei Wang
- National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, College of Horticulture & Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, China
- Hubei Hongshan Laboratory, Wuhan, 430070, China
| | - Patrick Duckney
- Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK
| | - Erlin Gao
- National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, College of Horticulture & Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, China
- Hubei Hongshan Laboratory, Wuhan, 430070, China
| | - Patrick J Hussey
- Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK
| | - Verena Kriechbaumer
- Endomembrane Structure and Function Research Group, Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
| | - Chengyang Li
- National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, College of Horticulture & Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, China
- Hubei Hongshan Laboratory, Wuhan, 430070, China
| | - Jingze Zang
- National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, College of Horticulture & Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, China
- Hubei Hongshan Laboratory, Wuhan, 430070, China
| | - Tong Zhang
- National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, College of Horticulture & Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, China
- Hubei Hongshan Laboratory, Wuhan, 430070, China
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7
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Yang L, Zhu H, Li M, Yu Q. The Tricalbin-Family Endoplasmic Reticulum-Plasma Membrane Tethering Proteins Attenuate ROS-Involved Caspofungin Sensitivity in Candida albicans. Microbiol Spectr 2022; 10:e0207922. [PMID: 36445092 PMCID: PMC9769562 DOI: 10.1128/spectrum.02079-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 11/07/2022] [Indexed: 12/02/2022] Open
Abstract
The endoplasmic reticulum-plasma membrane (ER-PM) contacts are one kind of important membrane contact structures in eukaryotic cells, which mediate material and message exchange between the ER and the PM. However, the specific types and functions of ER-PM tethering proteins are poorly understood in the human fungal pathogen Candida albicans. In this study, we observed that the two tricalbin-family proteins, i.e., Tcb1 and Tcb3, were colocalized with the ER-PM contacts in C. albicans. Deletion of the tricalbin-encoding genes TCB1 and TCB3 remarkably reduced ER-PM contacts, suggesting that tricalbins are ER-PM tethering proteins of C. albicans. Stress sensitivity assays showed that the TCB-deleted strains, including tcb1Δ/Δ, tcb3Δ/Δ, and tcb1Δ/Δ tcb3Δ/Δ, exhibited hypersensitivity to cell wall stress induced by caspofungin. Further investigation revealed that caspofungin induced drastic reactive oxygen species (ROS) accumulation in the mutants, which was attributed to enhanced oxidation of Ero1 in the ER lumen. Removal of intracellular ROS by the ROS scavenger vitamin C rescued the growth of the mutants under caspofungin treatment, indicating that Ero1 oxidation-related ROS accumulation was involved in caspofungin hypersensitivity of the mutants. Moreover, deletion of the TCB genes decreased secretion of extracellular aspartyl proteinases, reduced transport of the cell wall protein Hwp1 from the cytoplasm to the cell wall, and attenuated virulence of the fungal pathogen. This study sheds a light on the role of ER-PM tethering proteins in maintenance of cell wall integrity and virulence in fungal pathogens. IMPORTANCE The endoplasmic reticulum-plasma membrane contacts are important membrane contact structures in eukaryotic cells, functioning in material and message exchange between the ER and the PM. We observed that the two tricalbin-family endoplasmic reticulum-plasma membrane contact proteins are required for tolerance to caspofungin-induced cell wall stress in the pathogenic fungus Candida albicans. The tricalbin mutants exhibited hypersensitivity to cell wall stress induced by caspofungin. Further investigation revealed that Ero1 oxidation-related reactive species oxygen accumulation was involved in caspofungin hypersensitivity of the tricalbin mutants. Moreover, loss of tricalbins reduced secretion of extracellular aspartyl proteinases, decreased transport of the cell wall proteins from the cytoplasm to the cell wall, and attenuated virulence of the fungal pathogen. This study uncovers the role of ER-PM tethering proteins in sustaining protein secretion, maintenance of cell wall integrity and virulence in fungal pathogens.
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Affiliation(s)
- Li Yang
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, People’s Republic of China
| | - Hangqi Zhu
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, People’s Republic of China
| | - Mingchun Li
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, People’s Republic of China
| | - Qilin Yu
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, People’s Republic of China
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8
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TraB family proteins are components of ER-mitochondrial contact sites and regulate ER-mitochondrial interactions and mitophagy. Nat Commun 2022; 13:5658. [PMID: 36163196 PMCID: PMC9513094 DOI: 10.1038/s41467-022-33402-w] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Accepted: 09/16/2022] [Indexed: 01/18/2023] Open
Abstract
ER-mitochondrial contact sites (EMCSs) are important for mitochondrial function. Here, we have identified a EMCS complex, comprising a family of uncharacterised mitochondrial outer membrane proteins, TRB1, TRB2, and the ER protein, VAP27-1. In Arabidopsis, there are three TraB family isoforms and the trb1/trb2 double mutant exhibits abnormal mitochondrial morphology, strong starch accumulation, and impaired energy metabolism, indicating that these proteins are essential for normal mitochondrial function. Moreover, TRB1 and TRB2 proteins also interact with ATG8 in order to regulate mitochondrial degradation (mitophagy). The turnover of depolarised mitochondria is significantly reduced in both trb1/trb2 and VAP27 mutants (vap27-1,3,4,6) under mitochondrial stress conditions, with an increased population of dysfunctional mitochondria present in the cytoplasm. Consequently, plant recovery after stress is significantly perturbed, suggesting that TRB1-regulated mitophagy and ER-mitochondrial interaction are two closely related processes. Taken together, we ascribe a dual role to TraB family proteins which are component of the EMCS complex in eukaryotes, regulating both interaction of the mitochondria to the ER and mitophagy.
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9
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Zhang J, Chen X, Yang Z, Xu H, Weng S, Wang Z, Tang W. Endoplasmic reticulum membrane protein MoScs2 is important for asexual development and pathogenesis of Magnaporthe oryzae. Front Microbiol 2022; 13:906784. [PMID: 35992683 PMCID: PMC9386004 DOI: 10.3389/fmicb.2022.906784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 07/11/2022] [Indexed: 11/13/2022] Open
Abstract
Most secretory proteins are folded and modified in the endoplasmic reticulum (ER). In Saccharomyces cerevisiae, the absence of Scs2 protein will lead to the separation of the endoplasmic reticulum and plasma membrane, resulting in endoplasmic reticulum dysfunction, but its function is not clear in rice blast fungus or even filamentous fungus. In this study, we report the identification and characterization of MoSCS2 in the pathogenesis of the rice blast fungus Magnaporthe oryzae. Protein subcellular localization showed that MoSCS2 is mainly localized in the endoplasmic reticulum. Compared to the wild-type strain Guy11, the deletion mutant ΔMoscs2 showed a significant reduction in growth and conidiation. MoSCS2 deficiency also resulted in abnormal conidial morphology and septum formation. The ΔMoscs2 mutant shows delayed appressorium formation, and the appressorium of ΔMoscs2 mutant could not form huge turgor pressure to penetrate the host epidermal cell wall. Pathogenicity and plant leave infection assays showed that knockout of MoSCS2 significantly inhibited the expansion of the invasive hyphae in host cells, ultimately leading to the decline of pathogenicity. Moreover, MoSCS2 gene is also involved in the regulation of cell wall and endoplasmic reticulum stress response. In conclusion, MoSCS2 plays an important role in the growth, asexual production, conidia morphogenesis, infection-related morphogenesis and pathogenicity of M. oryzae.
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Affiliation(s)
- Jun Zhang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Xuehang Chen
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Zifeng Yang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Huxiao Xu
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Shuning Weng
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Zonghua Wang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- Institute of Oceanography, Minjiang University, Fuzhou, China
- Zonghua Wang,
| | - Wei Tang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- Institute of Oceanography, Minjiang University, Fuzhou, China
- Fujian Key Laboratory for Monitoring and Integrated Management of Crop Pests, Fuzhou, China
- *Correspondence: Wei Tang,
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10
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Bean BDM, Whiteway M, Martin VJJ. The MyLO CRISPR-Cas9 toolkit: a markerless yeast localization and overexpression CRISPR-Cas9 toolkit. G3 (BETHESDA, MD.) 2022; 12:jkac154. [PMID: 35708612 PMCID: PMC9339301 DOI: 10.1093/g3journal/jkac154] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 06/13/2022] [Indexed: 12/28/2022]
Abstract
The genetic tractability of the yeast Saccharomyces cerevisiae has made it a key model organism for basic research and a target for metabolic engineering. To streamline the introduction of tagged genes and compartmental markers with powerful Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) - CRISPR-associated protein 9 (Cas9)-based genome editing tools, we constructed a Markerless Yeast Localization and Overexpression (MyLO) CRISPR-Cas9 toolkit with 3 components: (1) a set of optimized Streptococcus pyogenes Cas9-guide RNA expression vectors with 5 selectable markers and the option to either preclone or cotransform the gRNAs; (2) vectors for the one-step construction of integration cassettes expressing an untagged or green fluorescent protein/red fluorescent protein/hemagglutinin-tagged gene of interest at one of 3 levels, supporting localization and overexpression studies; and (3) integration cassettes containing moderately expressed green fluorescent protein- or red fluorescent protein-tagged compartmental markers for colocalization experiments. These components allow rapid, high-efficiency genomic integrations and modifications with only transient selection for the Cas9 vector, resulting in markerless transformations. To demonstrate the ease of use, we applied our complete set of compartmental markers to colabel all target subcellular compartments with green fluorescent protein and red fluorescent protein. Thus, the MyLO toolkit packages CRISPR-Cas9 technology into a flexible, optimized bundle that allows the stable genomic integration of DNA with the ease of use approaching that of transforming plasmids.
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Affiliation(s)
- Björn D M Bean
- Department of Biology, Centre for Applied Synthetic Biology, Concordia University, Montréal, QC H4B1R6, Canada
| | - Malcolm Whiteway
- Department of Biology, Centre for Applied Synthetic Biology, Concordia University, Montréal, QC H4B1R6, Canada
| | - Vincent J J Martin
- Department of Biology, Centre for Applied Synthetic Biology, Concordia University, Montréal, QC H4B1R6, Canada
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11
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Thomas FB, Omnus DJ, Bader JM, Chung GH, Kono N, Stefan CJ. Tricalbin proteins regulate plasma membrane phospholipid homeostasis. Life Sci Alliance 2022; 5:5/8/e202201430. [PMID: 35440494 PMCID: PMC9018018 DOI: 10.26508/lsa.202201430] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 04/03/2022] [Accepted: 04/04/2022] [Indexed: 12/26/2022] Open
Abstract
The evolutionarily conserved extended synaptotagmin (E-Syt) proteins are calcium-activated lipid transfer proteins that function at contacts between the ER and plasma membrane (ER-PM contacts). However, roles of the E-Syt family members in PM lipid organisation remain incomplete. Among the E-Syt family, the yeast tricalbin (Tcb) proteins are essential for PM integrity upon heat stress, but it is not known how they contribute to PM maintenance. Using quantitative lipidomics and microscopy, we find that the Tcb proteins regulate phosphatidylserine homeostasis at the PM. Moreover, upon heat-induced membrane stress, Tcb3 co-localises with the PM protein Sfk1 that is implicated in PM phospholipid asymmetry and integrity. The Tcb proteins also control the PM targeting of the known phosphatidylserine effector Pkc1 upon heat-induced stress. Phosphatidylserine has evolutionarily conserved roles in PM organisation, integrity, and repair. We propose that phospholipid regulation is an ancient essential function of E-Syt family members required for PM integrity.
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Affiliation(s)
- Ffion B Thomas
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Deike J Omnus
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Jakob M Bader
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Gary Hc Chung
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Nozomu Kono
- Department of Health Chemistry, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Christopher J Stefan
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
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12
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Chidambaram R, Ramachandran G, Rajasekharan R, Nachiappan V. Impairment of transcription factor Gcr1p binding motif perturbs OPI3 transcription in Saccharomyces cerevisiae. J Cell Biochem 2022; 123:1032-1052. [PMID: 35416329 DOI: 10.1002/jcb.30245] [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: 08/22/2021] [Revised: 03/09/2022] [Accepted: 03/16/2022] [Indexed: 11/08/2022]
Abstract
In Saccharomyces cerevisiae, the transcription factor GCR1 plays a vital role in carbohydrate metabolism and in the current study we tried to elucidate its role in lipid metabolism. In silico analysis revealed the upstream activation sequence (UAS) in the promoter region of OPI3 possessed six conserved recognition sequences for Gcr1p and the ChIP assay confirmed the binding of Gcr1p on the OPI3 promoter region. The real-time quantitative polymerase chain reaction and promoter-reporter activity revealed a substantial reduction in OPI3 expression and was supported with decreased phosphatidylcholine (PC) level that is rescued with exogenous choline supplementation in gcr1∆ cells. Simultaneously, there was an increase in triacylglycerol level, accompanied with increased number and size of lipid droplets in gcr1∆ cells. The expression of pT1, pT2 truncations in opi3∆ cells revealed the -1 to -500 bp in the promoter region is essential for the activation of OPI3 transcription. The mutation specifically at UASCT box (-265) in the OPI3 promoter region displayed a reduction in the PC level and the additional mutation at UASINO (-165) further reduced the PC level. Collectively, our data suggest that the GCR1 transcription factor also regulates the OPI3 expression and has an impact on lipid homeostasis.
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Affiliation(s)
- Ravi Chidambaram
- Department of Biochemistry, School of Life Sciences, Bharathidasan University, Tiruchirappalli, Tamil Nadu, India
| | - Gowsalya Ramachandran
- Department of Biochemistry, School of Life Sciences, Bharathidasan University, Tiruchirappalli, Tamil Nadu, India
| | - Ram Rajasekharan
- Department of Microbiology, Central University of Tamil Nadu, Tamil Nadu, India
| | - Vasanthi Nachiappan
- Department of Biochemistry, School of Life Sciences, Bharathidasan University, Tiruchirappalli, Tamil Nadu, India
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13
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Quon E, Nenadic A, Zaman MF, Johansen J, Beh CT. ER-PM membrane contact site regulation by yeast ORPs and membrane stress pathways. PLoS Genet 2022; 18:e1010106. [PMID: 35239652 PMCID: PMC8923467 DOI: 10.1371/journal.pgen.1010106] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 03/15/2022] [Accepted: 02/16/2022] [Indexed: 02/01/2023] Open
Abstract
In yeast, at least seven proteins (Ice2p, Ist2p, Scs2/22p, Tcb1-Tcb3p) affect cortical endoplasmic reticulum (ER) tethering and contact with the plasma membrane (PM). In Δ-super-tether (Δ-s-tether) cells that lack these tethers, cortical ER-PM association is all but gone. Yeast OSBP homologue (Osh) proteins are also implicated in membrane contact site (MCS) assembly, perhaps as subunits for multicomponent tethers, though their function at MCSs involves intermembrane lipid transfer. Paradoxically, when analyzed by fluorescence and electron microscopy, the elimination of the OSH gene family does not reduce cortical ER-PM association but dramatically increases it. In response to the inactivation of all Osh proteins, the yeast E-Syt (extended-synaptotagmin) homologue Tcb3p is post-transcriptionally upregulated thereby generating additional Tcb3p-dependent ER-PM MCSs for recruiting more cortical ER to the PM. Although the elimination of OSH genes and the deletion of ER-PM tether genes have divergent effects on cortical ER-PM association, both elicit the Environmental Stress Response (ESR). Through comparisons of transcriptomic profiles of cells lacking OSH genes or ER-PM tethers, changes in ESR expression are partially manifested through the induction of the HOG (high-osmolarity glycerol) PM stress pathway or the ER-specific UPR (unfolded protein response) pathway, respectively. Defects in either UPR or HOG pathways also increase ER-PM MCSs, and expression of extra “artificial ER-PM membrane staples” rescues growth of UPR mutants challenged with lethal ER stress. Transcriptome analysis of OSH and Δ-s-tether mutants also revealed dysregulation of inositol-dependent phospholipid gene expression, and the combined lethality of osh4Δ and Δ-s-tether mutations is suppressed by overexpression of the phosphatidic acid biosynthetic gene, DGK1. These findings establish that the Tcb3p tether is induced by ER and PM stresses and ER-PM MCSs augment responses to membrane stresses, which are integrated through the broader ESR pathway. Membrane contact sites (MCSs) between the two largest cellular membranes, the endoplasmic reticulum (ER) and the plasma membrane (PM), are regulatory interfaces for lipid synthesis and bidirectional transport. The yeast Osh protein family, which represents the seven yeast oxysterol-binding protein related proteins (ORPs), is implicated in MCS regulation and lipid transfer between membranes. Ironically, we find that when all Osh proteins eliminated, ER-PM association is not reduced but significantly increases. We hypothesized this increase is due to compensatory increases in levels of tether proteins that physically link the ER and PM. In fact, in response to inactivating Osh protein expression, amounts of the tether protein Tcb3 increase and more ER-PM MCSs are produced. By testing the genomic transcriptional responses to the elimination of OSH and ER-PM tether genes, we find these mutants disrupt phospholipid regulation and they elicit the Environmental Stress Response (ESR) pathway, which integrates many different responses needed for recovery after cellular stress. OSH and ER-PM tether genes affect specific stress response pathways that impact the PM and ER, respectively. Combining OSH and tether mutations results in cell lethality, but these cells survive by increased expression of a key phospholipid biosynthetic gene. Based on these results, we propose that OSH and ER-PM tether genes affect phospholipid regulation and protect the PM and ER through membrane stress responses integrated through the ESR pathway.
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Affiliation(s)
- Evan Quon
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Aleksa Nenadic
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Mohammad F. Zaman
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Jesper Johansen
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Christopher T. Beh
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
- Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, Canada
- * E-mail:
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14
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Ptak C, Saik NO, Premashankar A, Lapetina DL, Aitchison JD, Montpetit B, Wozniak RW. Phosphorylation-dependent mitotic SUMOylation drives nuclear envelope-chromatin interactions. J Cell Biol 2021; 220:212843. [PMID: 34787675 PMCID: PMC8641411 DOI: 10.1083/jcb.202103036] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 07/30/2021] [Accepted: 09/22/2021] [Indexed: 12/15/2022] Open
Abstract
In eukaryotes, chromatin binding to the inner nuclear membrane (INM) and nuclear pore complexes (NPCs) contributes to spatial organization of the genome and epigenetic programs important for gene expression. In mitosis, chromatin–nuclear envelope (NE) interactions are lost and then formed again as sister chromosomes segregate to postmitotic nuclei. Investigating these processes in S. cerevisiae, we identified temporally and spatially controlled phosphorylation-dependent SUMOylation events that positively regulate postmetaphase chromatin association with the NE. Our work establishes a phosphorylation-mediated targeting mechanism of the SUMO ligase Siz2 to the INM during mitosis, where Siz2 binds to and SUMOylates the VAP protein Scs2. The recruitment of Siz2 through Scs2 is further responsible for a wave of SUMOylation along the INM that supports the assembly and anchorage of subtelomeric chromatin at the INM and localization of an active gene (INO1) to NPCs during the later stages of mitosis and into G1-phase.
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Affiliation(s)
- Christopher Ptak
- Department of Cell Biology, University of Alberta, Edmonton, Alberta, Canada
| | - Natasha O Saik
- Department of Cell Biology, University of Alberta, Edmonton, Alberta, Canada
| | | | - Diego L Lapetina
- Department of Cell Biology, University of Alberta, Edmonton, Alberta, Canada
| | | | - Ben Montpetit
- Department of Cell Biology, University of Alberta, Edmonton, Alberta, Canada.,Department of Viticulture and Enology, University of California Davis, Davis, CA
| | - Richard W Wozniak
- Department of Cell Biology, University of Alberta, Edmonton, Alberta, Canada
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15
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Papagiannidis D, Bircham PW, Lüchtenborg C, Pajonk O, Ruffini G, Brügger B, Schuck S. Ice2 promotes ER membrane biogenesis in yeast by inhibiting the conserved lipin phosphatase complex. EMBO J 2021; 40:e107958. [PMID: 34617598 PMCID: PMC8591542 DOI: 10.15252/embj.2021107958] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Revised: 09/01/2021] [Accepted: 09/03/2021] [Indexed: 11/30/2022] Open
Abstract
Cells dynamically adapt organelle size to current physiological demand. Organelle growth requires membrane biogenesis and therefore needs to be coordinated with lipid metabolism. The endoplasmic reticulum (ER) can undergo massive expansion, but the underlying regulatory mechanisms are largely unclear. Here, we describe a genetic screen for factors involved in ER membrane expansion in budding yeast and identify the ER transmembrane protein Ice2 as a strong hit. We show that Ice2 promotes ER membrane biogenesis by opposing the phosphatidic acid phosphatase Pah1, called lipin in metazoa. Specifically, Ice2 inhibits the conserved Nem1‐Spo7 complex and thus suppresses the dephosphorylation and activation of Pah1. Furthermore, Ice2 cooperates with the transcriptional regulation of lipid synthesis genes and helps to maintain cell homeostasis during ER stress. These findings establish the control of the lipin phosphatase complex as an important mechanism for regulating ER membrane biogenesis.
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Affiliation(s)
- Dimitrios Papagiannidis
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance and Cell Networks Cluster of Excellence, Heidelberg, Germany.,Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Peter W Bircham
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance and Cell Networks Cluster of Excellence, Heidelberg, Germany
| | | | - Oliver Pajonk
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance and Cell Networks Cluster of Excellence, Heidelberg, Germany.,Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Giulia Ruffini
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance and Cell Networks Cluster of Excellence, Heidelberg, Germany.,Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Britta Brügger
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Sebastian Schuck
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance and Cell Networks Cluster of Excellence, Heidelberg, Germany.,Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
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16
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Li KW, Lu MS, Iwamoto Y, Drubin DG, Pedersen RTA. A preferred sequence for organelle inheritance during polarized cell growth. J Cell Sci 2021; 134:272417. [PMID: 34622919 PMCID: PMC8627559 DOI: 10.1242/jcs.258856] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 09/27/2021] [Indexed: 12/25/2022] Open
Abstract
Some organelles cannot be synthesized anew, so they are segregated into daughter cells during cell division. In Saccharomyces cerevisiae, daughter cells bud from mother cells and are populated by organelles inherited from the mothers. To determine whether this organelle inheritance occurs in a stereotyped manner, we tracked organelles using fluorescence microscopy. We describe a program for organelle inheritance in budding yeast. The cortical endoplasmic reticulum (ER) and peroxisomes are inherited concomitantly with bud emergence. Next, vacuoles are inherited in small buds, followed closely by mitochondria. Finally, the nucleus and perinuclear ER are inherited when buds have nearly reached their maximal size. Because organelle inheritance timing correlates with bud morphology, which is coupled to the cell cycle, we tested whether disrupting the cell cycle alters organelle inheritance order. By arresting cell cycle progression but allowing continued bud growth, we determined that organelle inheritance still occurs when DNA replication is blocked, and that the general inheritance order is maintained. Thus, organelle inheritance follows a preferred order during polarized cell division and does not require completion of S-phase. Summary: Organelles are interconnected by contact sites, but they must be inherited from mother cells into buds during budding yeast mitosis. We report that this process occurs in a preferred sequence.
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Affiliation(s)
- Kathryn W Li
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Michelle S Lu
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Yuichiro Iwamoto
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - David G Drubin
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Ross T A Pedersen
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
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17
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Wong AKO, Young BP, Loewen CJ. Ist2 recruits the lipid transporters Osh6/7 to ER-PM contacts to maintain phospholipid metabolism. J Cell Biol 2021; 220:e201910161. [PMID: 34259806 PMCID: PMC8282664 DOI: 10.1083/jcb.201910161] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 04/13/2021] [Accepted: 06/15/2021] [Indexed: 12/26/2022] Open
Abstract
ER-plasma membrane (PM) contacts are proposed to be held together by distinct families of tethering proteins, which in yeast include the VAP homologues Scs2/22, the extended-synaptotagmin homologues Tcb1/2/3, and the TMEM16 homologue Ist2. It is unclear whether these tethers act redundantly or whether individual tethers have specific functions at contacts. Here, we show that Ist2 directly recruits the phosphatidylserine (PS) transport proteins and ORP family members Osh6 and Osh7 to ER-PM contacts through a binding site located in Ist2's disordered C-terminal tethering region. This interaction is required for phosphatidylethanolamine (PE) production by the PS decarboxylase Psd2, whereby PS transported from the ER to the PM by Osh6/7 is endocytosed to the site of Psd2 in endosomes/Golgi/vacuoles. This role for Ist2 and Osh6/7 in nonvesicular PS transport is specific, as other tethers/transport proteins do not compensate. Thus, we identify a molecular link between the ORP and TMEM16 families and a role for endocytosis of PS in PE synthesis.
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Affiliation(s)
| | | | - Christopher J.R. Loewen
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
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18
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Chao JT, Pina F, Niwa M. Regulation of the early stages of endoplasmic reticulum inheritance during ER stress. Mol Biol Cell 2021; 32:109-119. [PMID: 33448894 PMCID: PMC8120693 DOI: 10.1091/mbc.e20-08-0558] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The endoplasmic reticulum (ER) is one of the largest cytoplasmic organelles in eukaryotic cells and plays a role in many cellular processes, such as the production and quality control of secretory protein, lipid synthesis, and calcium homeostasis. The ER cannot be generated de novo, and thus its proper inheritance during cell division is paramount to the health and survival of the daughter cells. Although previous work has uncovered the cytoskeletal components involved, we still lack a comprehensive understanding of the intricate steps of and the cytoplasmic and membrane-bound components involved in ER inheritance. To directly address these issues, we utilized microfluidics and genetic analyses to show that before nuclear migration, early ER inheritance can be further divided into three distinctive steps. Moreover, we demonstrated that perturbing each of these steps affects the cell's ability to mitigate ER stress. Thus, proper ER inheritance is essential to ensuring a healthy, functional cell.
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Affiliation(s)
- Jesse T Chao
- Division of Biological Sciences, Section of Molecular Biology, University of California, San Diego, La Jolla, CA 92093-0377.,Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada V6T 1Z3
| | - Francisco Pina
- Division of Biological Sciences, Section of Molecular Biology, University of California, San Diego, La Jolla, CA 92093-0377.,Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada V6T 1Z3
| | - Maho Niwa
- Division of Biological Sciences, Section of Molecular Biology, University of California, San Diego, La Jolla, CA 92093-0377
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19
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Alli-Balogun GO, Levine TP. Fungal Ice2p is in the same superfamily as SERINCs, restriction factors for HIV and other viruses. Proteins 2021; 89:1240-1250. [PMID: 33982326 DOI: 10.1002/prot.26145] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 05/10/2021] [Indexed: 12/13/2022]
Abstract
Ice2p is an integral endoplasmic reticulum (ER) membrane protein in budding yeast S. cerevisiae named ICE because it is required for Inheritance of Cortical ER. Ice2p has also been reported to be involved in an ER metabolic branch-point that regulates the flux of lipid either to be stored in lipid droplets or to be used as membrane components. Alternately, Ice2p has been proposed to act as a tether that physically bridges the ER at contact sites with both lipid droplets and the plasma membrane via a long loop on the protein's cytoplasmic face that contains multiple predicted amphipathic helices. Here we carried out a bioinformatic analysis to increase understanding of Ice2p. First, regarding topology, we found that diverse members of the fungal Ice2 family have 10 transmembrane helices (TMHs), which places the long loop on the exofacial face of Ice2p, where it cannot form inter-organelle bridges. Second, we identified Ice2p as a full-length homolog of SERINC (serine incorporator), a family of proteins with 10 TMHs found universally in eukaryotes. Since SERINCs are potent restriction factors for HIV and other viruses, study of Ice2p may reveal functions or mechanisms that shed light on viral restriction by SERINCs.
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Affiliation(s)
| | - Tim P Levine
- UCL Institute of Ophthalmology, University College London, London, UK
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20
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Yap WS, Shyu P, Gaspar ML, Jesch SA, Marvalim C, Prinz WA, Henry SA, Thibault G. The yeast FIT2 homologs are necessary to maintain cellular proteostasis and membrane lipid homeostasis. J Cell Sci 2020; 133:jcs248526. [PMID: 33033181 PMCID: PMC7657468 DOI: 10.1242/jcs.248526] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 10/01/2020] [Indexed: 12/12/2022] Open
Abstract
Lipid droplets (LDs) are implicated in conditions of lipid and protein dysregulation. The fat storage-inducing transmembrane (FIT; also known as FITM) family induces LD formation. Here, we establish a model system to study the role of the Saccharomyces cerevisiae FIT homologues (ScFIT), SCS3 and YFT2, in the proteostasis and stress response pathways. While LD biogenesis and basal endoplasmic reticulum (ER) stress-induced unfolded protein response (UPR) remain unaltered in ScFIT mutants, SCS3 was found to be essential for proper stress-induced UPR activation and for viability in the absence of the sole yeast UPR transducer IRE1 Owing to not having a functional UPR, cells with mutated SCS3 exhibited an accumulation of triacylglycerol within the ER along with aberrant LD morphology, suggesting that there is a UPR-dependent compensatory mechanism that acts to mitigate lack of SCS3 Additionally, SCS3 was necessary to maintain phospholipid homeostasis. Strikingly, global protein ubiquitylation and the turnover of both ER and cytoplasmic misfolded proteins is impaired in ScFITΔ cells, while a screen for interacting partners of Scs3 identifies components of the proteostatic machinery as putative targets. Together, our data support a model where ScFITs play an important role in lipid metabolism and proteostasis beyond their defined roles in LD biogenesis.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Wei Sheng Yap
- School of Biological Sciences Nanyang Technological University, Singapore, 637551
| | - Peter Shyu
- School of Biological Sciences Nanyang Technological University, Singapore, 637551
| | - Maria Laura Gaspar
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Stephen A Jesch
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Charlie Marvalim
- School of Biological Sciences Nanyang Technological University, Singapore, 637551
| | - William A Prinz
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA
| | - Susan A Henry
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Guillaume Thibault
- School of Biological Sciences Nanyang Technological University, Singapore, 637551
- Institute of Molecular and Cell Biology, A*STAR, Singapore, 138673
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21
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Nath VR, Mishra S, Basak B, Trivedi D, Raghu P. Extended synaptotagmin regulates membrane contact site structure and lipid transfer function in vivo. EMBO Rep 2020; 21:e50264. [PMID: 32716137 DOI: 10.15252/embr.202050264] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 06/12/2020] [Accepted: 06/22/2020] [Indexed: 12/20/2022] Open
Abstract
Inter-organelle communication between closely apposed membranes is proposed at membrane contact sites (MCS). However, the regulation of MCS structure and their functional relevance in vivo remain debated. The extended synaptotagmins (Esyt) are evolutionarily conserved proteins proposed to function at MCS. However, loss of all three Esyts in yeast or mammals shows minimal phenotypes questioning the functional importance of Esyt. We report that in Drosophila photoreceptors, MCS number is regulated by PLCβ activity. Photoreceptors of a null allele of Drosophila extended synaptotagmin (dEsyt) show loss of ER-PM MCS. Loss of dEsyt results in mislocalization of RDGB, an MCS localized lipid transfer protein, required for photoreceptor structure and function, ultimately leading to retinal degeneration. dEsyt depletion enhanced the retinal degeneration, reduced light responses and slower rates of plasma membrane PIP2 resynthesis seen in rdgB mutants. Thus, dEsyt function and PLCβ signaling regulate ER-PM MCS structure and lipid transfer in Drosophila photoreceptors.
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Affiliation(s)
- Vaisaly R Nath
- National Centre for Biological Sciences-TIFR, Bangalore, India.,School of Biotechnology, Amrita Vishwa Vidyapeetham, Amritapuri, Kollam, Kerala, India
| | - Shirish Mishra
- National Centre for Biological Sciences-TIFR, Bangalore, India
| | - Bishal Basak
- National Centre for Biological Sciences-TIFR, Bangalore, India
| | - Deepti Trivedi
- National Centre for Biological Sciences-TIFR, Bangalore, India
| | - Padinjat Raghu
- National Centre for Biological Sciences-TIFR, Bangalore, India
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22
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Zaman MF, Nenadic A, Radojičić A, Rosado A, Beh CT. Sticking With It: ER-PM Membrane Contact Sites as a Coordinating Nexus for Regulating Lipids and Proteins at the Cell Cortex. Front Cell Dev Biol 2020; 8:675. [PMID: 32793605 PMCID: PMC7387695 DOI: 10.3389/fcell.2020.00675] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Accepted: 07/03/2020] [Indexed: 12/31/2022] Open
Abstract
Membrane contact sites between the cortical endoplasmic reticulum (ER) and the plasma membrane (PM) provide a direct conduit for small molecule transfer and signaling between the two largest membranes of the cell. Contact is established through ER integral membrane proteins that physically tether the two membranes together, though the general mechanism is remarkably non-specific given the diversity of different tethering proteins. Primary tethers including VAMP-associated proteins (VAPs), Anoctamin/TMEM16/Ist2p homologs, and extended synaptotagmins (E-Syts), are largely conserved in most eukaryotes and are both necessary and sufficient for establishing ER-PM association. In addition, other species-specific ER-PM tether proteins impart unique functional attributes to both membranes at the cell cortex. This review distils recent functional and structural findings about conserved and species-specific tethers that form ER-PM contact sites, with an emphasis on their roles in the coordinate regulation of lipid metabolism, cellular structure, and responses to membrane stress.
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Affiliation(s)
- Mohammad F Zaman
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada
| | - Aleksa Nenadic
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada
| | - Ana Radojičić
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada.,Department of Botany, University of British Columbia, Vancouver, BC, Canada
| | - Abel Rosado
- Department of Botany, University of British Columbia, Vancouver, BC, Canada
| | - Christopher T Beh
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada.,The Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, BC, Canada
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23
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Klecker T, Westermann B. Asymmetric inheritance of mitochondria in yeast. Biol Chem 2020; 401:779-791. [DOI: 10.1515/hsz-2019-0439] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 01/15/2020] [Indexed: 01/27/2023]
Abstract
AbstractMitochondria are essential organelles of virtually all eukaryotic organisms. As they cannot be made de novo, they have to be inherited during cell division. In this review, we provide an overview on mitochondrial inheritance in Saccharomyces cerevisiae, a powerful model organism to study asymmetric cell division. Several processes have to be coordinated during mitochondrial inheritance: mitochondrial transport along the actin cytoskeleton into the emerging bud is powered by a myosin motor protein; cell cortex anchors retain a critical fraction of mitochondria in the mother cell and bud to ensure proper partitioning; and the quantity of mitochondria inherited by the bud is controlled during cell cycle progression. Asymmetric division of yeast cells produces rejuvenated daughter cells and aging mother cells that die after a finite number of cell divisions. We highlight the critical role of mitochondria in this process and discuss how asymmetric mitochondrial partitioning and cellular aging are connected.
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Affiliation(s)
- Till Klecker
- Institut für Zellbiologie, Universität Bayreuth, 95440 Bayreuth, Germany
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24
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Omnus DJ, Cadou A, Thomas FB, Bader JM, Soh N, Chung GHC, Vaughan AN, Stefan CJ. A heat-sensitive Osh protein controls PI4P polarity. BMC Biol 2020; 18:28. [PMID: 32169085 PMCID: PMC7071650 DOI: 10.1186/s12915-020-0758-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2019] [Accepted: 02/26/2020] [Indexed: 01/28/2023] Open
Abstract
BACKGROUND Phosphoinositide lipids provide spatial landmarks during polarized cell growth and migration. Yet how phosphoinositide gradients are oriented in response to extracellular cues and environmental conditions is not well understood. Here, we elucidate an unexpected mode of phosphatidylinositol 4-phosphate (PI4P) regulation in the control of polarized secretion. RESULTS We show that PI4P is highly enriched at the plasma membrane of growing daughter cells in budding yeast where polarized secretion occurs. However, upon heat stress conditions that redirect secretory traffic, PI4P rapidly increases at the plasma membrane in mother cells resulting in a more uniform PI4P distribution. Precise control of PI4P distribution is mediated through the Osh (oxysterol-binding protein homology) proteins that bind and present PI4P to a phosphoinositide phosphatase. Interestingly, Osh3 undergoes a phase transition upon heat stress conditions, resulting in intracellular aggregates and reduced cortical localization. Both the Osh3 GOLD and ORD domains are sufficient to form heat stress-induced aggregates, indicating that Osh3 is highly tuned to heat stress conditions. Upon loss of Osh3 function, the polarized distribution of both PI4P and the exocyst component Exo70 are impaired. Thus, an intrinsically heat stress-sensitive PI4P regulatory protein controls the spatial distribution of phosphoinositide lipid metabolism to direct secretory trafficking as needed. CONCLUSIONS Our results suggest that control of PI4P metabolism by Osh proteins is a key determinant in the control of polarized growth and secretion.
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Affiliation(s)
- Deike J Omnus
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, United Kingdom
- Present address: Science for Life Laboratory, Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Angela Cadou
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, United Kingdom
| | - Ffion B Thomas
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, United Kingdom
| | - Jakob M Bader
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, United Kingdom
- Present address: Department of Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Nathaniel Soh
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, United Kingdom
| | - Gary H C Chung
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, United Kingdom
| | - Andrew N Vaughan
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, United Kingdom
| | - Christopher J Stefan
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, United Kingdom.
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25
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Kozlova NV, Pichon C, Rahmouni AR. mRNA with Mammalian Codon Bias Accumulates in Yeast Mutants with Constitutive Stress Granules. Int J Mol Sci 2020; 21:ijms21041234. [PMID: 32059599 PMCID: PMC7072924 DOI: 10.3390/ijms21041234] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 02/04/2020] [Accepted: 02/04/2020] [Indexed: 11/19/2022] Open
Abstract
Stress granules and P bodies are cytoplasmic structures assembled in response to various stress factors and represent sites of temporary storage or decay of mRNAs. Depending on the source of stress, the formation of these structures may be driven by distinct mechanisms, but several stresses have been shown to stabilize mRNAs via inhibition of deadenylation. A recent study identified yeast gene deletion mutants with constitutive stress granules and elevated P bodies; however, the mechanisms which trigger its formation remain poorly understood. Here, we investigate the possibility of accumulating mRNA with mammalian codon bias, which we termed the model RNA, in these mutants. We found that the model RNA accumulates in dcp2 and xrn1 mutants and in four mutants with constitutive stress granules overlapping with P bodies. However, in eight other mutants with constitutive stress granules, the model RNA is downregulated, or its steady state levels vary. We further suggest that the accumulation of the model RNA is linked to its protection from the main mRNA surveillance path. However, there is no obvious targeting of the model RNA to stress granules or P bodies. Thus, accumulation of the model RNA and formation of constitutive stress granules occur independently and only some paths inducing formation of constitutive stress granules will stabilize mRNA as well.
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Affiliation(s)
- Natalia V. Kozlova
- Centre de Biophysique Moléculaire, UPR 4301 du CNRS, Rue Charles Sadron, 45071 Orléans, France;
- Correspondence: (N.V.K.); (A.R.R.)
| | - Chantal Pichon
- Centre de Biophysique Moléculaire, UPR 4301 du CNRS, Rue Charles Sadron, 45071 Orléans, France;
- Colléguim Sciences et Techniques, Université d’Orléans, 45071 Orléans, France
| | - A. Rachid Rahmouni
- Centre de Biophysique Moléculaire, UPR 4301 du CNRS, Rue Charles Sadron, 45071 Orléans, France;
- Correspondence: (N.V.K.); (A.R.R.)
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26
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Manchalu S, Mittal N, Spang A, Jansen RP. Local translation of yeast ERG4 mRNA at the endoplasmic reticulum requires the brefeldin A resistance protein Bfr1. RNA (NEW YORK, N.Y.) 2019; 25:1661-1672. [PMID: 31455610 PMCID: PMC6859859 DOI: 10.1261/rna.072017.119] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Accepted: 08/20/2019] [Indexed: 05/13/2023]
Abstract
Brefeldin A resistance factor 1 (Bfr1p) is a nonessential RNA-binding protein and multicopy suppressor of brefeldin A sensitivity in Saccharomyces cerevisiae Deletion of BFR1 leads to multiple defects, including altered cell shape and size, change in ploidy, induction of P-bodies and chromosomal missegregation. Bfr1p has been shown to associate with polysomes, binds to several hundred mRNAs, and can target some of them to P-bodies. Although this implies a role of Bfr1p in translational control of mRNAs, its molecular function remains elusive. In the present study, we show that mutations in RNA-binding residues of Bfr1p impede its RNA-dependent colocalization with ER, yet do not mimic the known cellular defects seen upon BFR1 deletion. However, a Bfr1 RNA-binding mutant is impaired in binding to ERG4 mRNA, which encodes an enzyme required for the final step of ergosterol biosynthesis. Consistently, bfr1Δ strains show a strong reduction in Erg4p protein levels, most likely because of degradation of misfolded Erg4p. Polysome profiling of bfr1Δ or bfr1 mutant strains reveals a strong shift of ERG4 mRNA to polysomes, consistent with a function of Bfr1p in elongation or increased ribosome loading. Collectively, our data reveal that Bfr1 has at least two separable functions: one in RNA binding and cotranslational protein translocation into the ER and one in ploidy control or chromosome segregation.
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Affiliation(s)
- Srinivas Manchalu
- Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen 72076, Germany
| | - Nitish Mittal
- Biozentrum, University of Basel, Basel 4056, Switzerland
| | - Anne Spang
- Biozentrum, University of Basel, Basel 4056, Switzerland
| | - Ralf-Peter Jansen
- Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen 72076, Germany
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27
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Collado J, Kalemanov M, Campelo F, Bourgoint C, Thomas F, Loewith R, Martínez-Sánchez A, Baumeister W, Stefan CJ, Fernández-Busnadiego R. Tricalbin-Mediated Contact Sites Control ER Curvature to Maintain Plasma Membrane Integrity. Dev Cell 2019; 51:476-487.e7. [PMID: 31743662 PMCID: PMC6863395 DOI: 10.1016/j.devcel.2019.10.018] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Revised: 09/23/2019] [Accepted: 10/16/2019] [Indexed: 12/23/2022]
Abstract
Membrane contact sites (MCS) between the endoplasmic reticulum (ER) and the plasma membrane (PM) play fundamental roles in all eukaryotic cells. ER-PM MCS are particularly abundant in Saccharomyces cerevisiae, where approximately half of the PM surface is covered by cortical ER (cER). Several proteins, including Ist2, Scs2/22, and Tcb1/2/3 are implicated in cER formation, but the specific roles of these molecules are poorly understood. Here, we use cryo-electron tomography to show that ER-PM tethers are key determinants of cER morphology. Notably, Tcb proteins (tricalbins) form peaks of extreme curvature on the cER membrane facing the PM. Combined modeling and functional assays suggest that Tcb-mediated cER peaks facilitate the transport of lipids between the cER and the PM, which is necessary to maintain PM integrity under heat stress. ER peaks were also present at other MCS, implying that membrane curvature enforcement may be a widespread mechanism to regulate MCS function.
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Affiliation(s)
- Javier Collado
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Martinsried 82152, Germany; Institute of Neuropathology, University Medical Center Göttingen, Göttingen 37099, Germany; Graduate School of Quantitative Biosciences Munich, Munich 81337, Germany
| | - Maria Kalemanov
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Martinsried 82152, Germany; Graduate School of Quantitative Biosciences Munich, Munich 81337, Germany
| | - Felix Campelo
- ICFO, Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels 08860, Spain
| | - Clélia Bourgoint
- Department of Molecular Biology, University of Geneva, Geneva 1211, Switzerland
| | - Ffion Thomas
- MRC Laboratory for Molecular Cell Biology, University College London, London, WC1E 6BT, UK
| | - Robbie Loewith
- Department of Molecular Biology, University of Geneva, Geneva 1211, Switzerland; Swiss National Centre for Competence in Research, Program Chemical Biology, Geneva 1211, Switzerland
| | - Antonio Martínez-Sánchez
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Martinsried 82152, Germany
| | - Wolfgang Baumeister
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Martinsried 82152, Germany
| | - Christopher J Stefan
- MRC Laboratory for Molecular Cell Biology, University College London, London, WC1E 6BT, UK
| | - Rubén Fernández-Busnadiego
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Martinsried 82152, Germany; Institute of Neuropathology, University Medical Center Göttingen, Göttingen 37099, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany.
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28
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Hoffmann PC, Bharat TAM, Wozny MR, Boulanger J, Miller EA, Kukulski W. Tricalbins Contribute to Cellular Lipid Flux and Form Curved ER-PM Contacts that Are Bridged by Rod-Shaped Structures. Dev Cell 2019; 51:488-502.e8. [PMID: 31743663 PMCID: PMC6863393 DOI: 10.1016/j.devcel.2019.09.019] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Revised: 08/06/2019] [Accepted: 09/25/2019] [Indexed: 11/25/2022]
Abstract
Lipid flow between cellular organelles occurs via membrane contact sites. Extended-synaptotagmins, known as tricalbins in yeast, mediate lipid transfer between the endoplasmic reticulum (ER) and plasma membrane (PM). How these proteins regulate membrane architecture to transport lipids across the aqueous space between bilayers remains unknown. Using correlative microscopy, electron cryo-tomography, and high-throughput genetics, we address the interplay of architecture and function in budding yeast. We find that ER-PM contacts differ in protein composition and membrane morphology, not in intermembrane distance. In situ electron cryo-tomography reveals the molecular organization of tricalbin-mediated contacts, suggesting a structural framework for putative lipid transfer. Genetic analysis uncovers functional overlap with cellular lipid routes, such as maintenance of PM asymmetry. Further redundancies are suggested for individual tricalbin protein domains. We propose a modularity of molecular and structural functions of tricalbins and of their roles within the cellular network of lipid distribution pathways.
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Affiliation(s)
- Patrick C Hoffmann
- Cell Biology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Tanmay A M Bharat
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK; Central Oxford Structural Microscopy and Imaging Centre, South Parks Road, Oxford OX1 3RE, UK
| | - Michael R Wozny
- Cell Biology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Jerome Boulanger
- Cell Biology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Elizabeth A Miller
- Cell Biology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Wanda Kukulski
- Cell Biology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK.
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29
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Wang P, Pleskot R, Zang J, Winkler J, Wang J, Yperman K, Zhang T, Wang K, Gong J, Guan Y, Richardson C, Duckney P, Vandorpe M, Mylle E, Fiserova J, Van Damme D, Hussey PJ. Plant AtEH/Pan1 proteins drive autophagosome formation at ER-PM contact sites with actin and endocytic machinery. Nat Commun 2019; 10:5132. [PMID: 31723129 PMCID: PMC6853982 DOI: 10.1038/s41467-019-12782-6] [Citation(s) in RCA: 68] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Accepted: 09/25/2019] [Indexed: 12/16/2022] Open
Abstract
The Arabidopsis EH proteins (AtEH1/Pan1 and AtEH2/Pan1) are components of the endocytic TPLATE complex (TPC) which is essential for endocytosis. Both proteins are homologues of the yeast ARP2/3 complex activator, Pan1p. Here, we show that these proteins are also involved in actin cytoskeleton regulated autophagy. Both AtEH/Pan1 proteins localise to the plasma membrane and autophagosomes. Upon induction of autophagy, AtEH/Pan1 proteins recruit TPC and AP-2 subunits, clathrin, actin and ARP2/3 proteins to autophagosomes. Increased expression of AtEH/Pan1 proteins boosts autophagosome formation, suggesting independent and redundant pathways for actin-mediated autophagy in plants. Moreover, AtEHs/Pan1-regulated autophagosomes associate with ER-PM contact sites (EPCS) where AtEH1/Pan1 interacts with VAP27-1. Knock-down expression of either AtEH1/Pan1 or VAP27-1 makes plants more susceptible to nutrient depleted conditions, indicating that the autophagy pathway is perturbed. In conclusion, we identify the existence of an autophagy-dependent pathway in plants to degrade endocytic components, starting at the EPCS through the interaction among AtEH/Pan1, actin cytoskeleton and the EPCS resident protein VAP27-1. Arabidopsis EH/Pan1 proteins are part of the TPLATE complex (TPC) that is required for endocytosis in plants. Here, the authors show AtEH/Pan1 proteins also act in actin-mediated autophagy, by interacting with VAP27-1 at ER-PM contact sites and recruiting TPLATE and AP-2 complex subunits, clathrin and ARP2/3/ proteins to autophagosomes.
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Affiliation(s)
- Pengwei Wang
- Department of Biosciences, Durham University, South road, Durham, DH1 3LE, UK.,Key Laboratory of Horticultural Plant Biology (MOE), College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, Hubei Province, PR China
| | - Roman Pleskot
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 71, 9052, Ghent, Belgium.,VIB Center for Plant Systems Biology, Technologiepark 71, 9052, Ghent, Belgium
| | - Jingze Zang
- Department of Biosciences, Durham University, South road, Durham, DH1 3LE, UK.,Key Laboratory of Horticultural Plant Biology (MOE), College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, Hubei Province, PR China
| | - Joanna Winkler
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 71, 9052, Ghent, Belgium.,VIB Center for Plant Systems Biology, Technologiepark 71, 9052, Ghent, Belgium
| | - Jie Wang
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 71, 9052, Ghent, Belgium
| | - Klaas Yperman
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 71, 9052, Ghent, Belgium.,VIB Center for Plant Systems Biology, Technologiepark 71, 9052, Ghent, Belgium
| | - Tong Zhang
- Key Laboratory of Horticultural Plant Biology (MOE), College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, Hubei Province, PR China
| | - Kun Wang
- Key Laboratory of Horticultural Plant Biology (MOE), College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, Hubei Province, PR China
| | - Jinli Gong
- Key Laboratory of Horticultural Plant Biology (MOE), College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, Hubei Province, PR China
| | - Yajie Guan
- Key Laboratory of Horticultural Plant Biology (MOE), College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, Hubei Province, PR China
| | | | - Patrick Duckney
- Department of Biosciences, Durham University, South road, Durham, DH1 3LE, UK
| | - Michael Vandorpe
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 71, 9052, Ghent, Belgium.,VIB Center for Plant Systems Biology, Technologiepark 71, 9052, Ghent, Belgium
| | - Evelien Mylle
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 71, 9052, Ghent, Belgium.,VIB Center for Plant Systems Biology, Technologiepark 71, 9052, Ghent, Belgium
| | - Jindriska Fiserova
- Department of Biosciences, Durham University, South road, Durham, DH1 3LE, UK.,Department of Biology of the Cell Nucleus, Institute of Molecular Genetics CAS, v.v.i., Vídeňská 1083, Prague, 14200, Czech Republic
| | - Daniel Van Damme
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 71, 9052, Ghent, Belgium. .,VIB Center for Plant Systems Biology, Technologiepark 71, 9052, Ghent, Belgium.
| | - Patrick J Hussey
- Department of Biosciences, Durham University, South road, Durham, DH1 3LE, UK.
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30
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Omer S, Greenberg SR, Lee WL. Cortical dynein pulling mechanism is regulated by differentially targeted attachment molecule Num1. eLife 2018; 7:36745. [PMID: 30084355 PMCID: PMC6080947 DOI: 10.7554/elife.36745] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2018] [Accepted: 07/05/2018] [Indexed: 12/17/2022] Open
Abstract
Cortical dynein generates pulling forces via microtubule (MT) end capture-shrinkage and lateral MT sliding mechanisms. In Saccharomyces cerevisiae, the dynein attachment molecule Num1 interacts with endoplasmic reticulum (ER) and mitochondria to facilitate spindle positioning across the mother-bud neck, but direct evidence for how these cortical contacts regulate dynein-dependent pulling forces is lacking. We show that loss of Scs2/Scs22, ER tethering proteins, resulted in defective Num1 distribution and loss of dynein-dependent MT sliding, the hallmark of dynein function. Cells lacking Scs2/Scs22 performed spindle positioning via MT end capture-shrinkage mechanism, requiring dynein anchorage to an ER- and mitochondria-independent population of Num1, dynein motor activity, and CAP-Gly domain of dynactin Nip100/p150Glued subunit. Additionally, a CAAX-targeted Num1 rescued loss of lateral patches and MT sliding in the absence of Scs2/Scs22. These results reveal distinct populations of Num1 and underline the importance of their spatial distribution as a critical factor for regulating dynein pulling force. Cells must divide so that organisms can grow, repair damaged tissues or reproduce. Before dividing, a cell creates two identical copies of its genetic information – one for each daughter. A molecular machine known as the mitotic spindle then moves each set of genetic material to where it will be needed when the daughter cells form. For the process to work properly, however, a motor protein known as dynein must correctly position the spindle by pulling it into place from the outskirts of the cell. When a baker’s yeast cell divides, it first forms a ‘bump’, which grows into a bud that will ultimately become another yeast. The spindle needs to be precisely placed at the midpoint between the original cell and the bud, so the genetic material can get into the future daughter cell. To do so, dynein travels to the bud, where a protein called Num1 helps it attach to the periphery and pull the filaments of the mitotic spindle (known as microtubules) to the correct position. Num1 also attaches to other cellular structures in the bud, including one known as the endoplasmic reticulum. It was unclear how this connection changes where dynein is located, and how it can pull on the spindle. To study this, Omer et al. labeled Num1, dynein and microtubules with fluorescent markers so they could be followed in living baker’s yeast using time-lapse microscopy. Mutant yeast strains were also used to disrupt how these proteins associate, which helps to tease out their roles. The experiments show that there are several populations of Num1 in the bud. One associates with the endoplasmic reticulum, and it helps dynein grab the side of a microtubule and make it slide into the bud. The other does not attach to the reticulum, but instead is located at the very tip of the bud. There, it makes dynein capture the end of the microtubule; this destabilizes the filament, which starts to shorten. As the microtubule shrinks, the spindle is pulled closer to the bud’s tip, which aligns it in the right position. The yeast cells thus need Num1 in both locations to fine-tune the pulling activity of dynein, and the spindle’s final positioning. In the human body, not all divisions create two identical cells; for example, the daughters of stem cells can have different fates. This is due to a precise asymmetric division which dynein partly controls. The results by Omer et al. could help to unravel this mechanism.
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Affiliation(s)
- Safia Omer
- Molecular and Cellular Biology Graduate Program, University of Massachusetts, Amherst, United States
| | - Samuel R Greenberg
- Department of Biological Sciences, Dartmouth College, Hanover, United States
| | - Wei-Lih Lee
- Department of Biological Sciences, Dartmouth College, Hanover, United States
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31
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Mitochondrial junctions with cellular organelles: Ca 2+ signalling perspective. Pflugers Arch 2018; 470:1181-1192. [PMID: 29982949 PMCID: PMC6060751 DOI: 10.1007/s00424-018-2179-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 06/27/2018] [Accepted: 06/29/2018] [Indexed: 01/21/2023]
Abstract
Cellular organelles form multiple junctional complexes with one another and the emerging research area dealing with such structures and their functions is undergoing explosive growth. A new research journal named “Contact” has been recently established to facilitate the development of this research field. The current consensus is to define an organellar junction by the maximal distance between the participating organelles; and the gap of 30 nm or less is considered appropriate for classifying such structures as junctions or membrane contact sites. Ideally, the organellar junction should have a functional significance, i.e. facilitate transfer of calcium, sterols, phospholipids, iron and possibly other substances between the organelles (Carrasco and Meyer in Annu Rev Biochem 80:973–1000, 2011; Csordas et al. in Trends Cell Biol 28:523–540, 2018; Phillips and Voeltz in Nat Rev Mol Cell Biol 17:69–82, 2016; Prinz in J Cell Biol 205:759–769, 2014). It is also important to note that the junction is not just a result of a random organelle collision but have active and specific formation, stabilisation and disassembly mechanisms. The nature of these mechanisms and their role in physiology/pathophysiology are the main focus of an emerging research field. In this review, we will briefly describe junctional complexes formed by cellular organelles and then focus on the junctional complexes that are formed by mitochondria with other organelles and the role of these complexes in regulating Ca2+ signalling.
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32
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Quon E, Sere YY, Chauhan N, Johansen J, Sullivan DP, Dittman JS, Rice WJ, Chan RB, Di Paolo G, Beh CT, Menon AK. Endoplasmic reticulum-plasma membrane contact sites integrate sterol and phospholipid regulation. PLoS Biol 2018; 16:e2003864. [PMID: 29782498 PMCID: PMC5983861 DOI: 10.1371/journal.pbio.2003864] [Citation(s) in RCA: 101] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Revised: 06/01/2018] [Accepted: 04/20/2018] [Indexed: 01/21/2023] Open
Abstract
Tether proteins attach the endoplasmic reticulum (ER) to other cellular membranes, thereby creating contact sites that are proposed to form platforms for regulating lipid homeostasis and facilitating non-vesicular lipid exchange. Sterols are synthesized in the ER and transported by non-vesicular mechanisms to the plasma membrane (PM), where they represent almost half of all PM lipids and contribute critically to the barrier function of the PM. To determine whether contact sites are important for both sterol exchange between the ER and PM and intermembrane regulation of lipid metabolism, we generated Δ-super-tether (Δ-s-tether) yeast cells that lack six previously identified tethering proteins (yeast extended synatotagmin [E-Syt], vesicle-associated membrane protein [VAMP]-associated protein [VAP], and TMEM16-anoctamin homologues) as well as the presumptive tether Ice2. Despite the lack of ER-PM contacts in these cells, ER-PM sterol exchange is robust, indicating that the sterol transport machinery is either absent from or not uniquely located at contact sites. Unexpectedly, we found that the transport of exogenously supplied sterol to the ER occurs more slowly in Δ-s-tether cells than in wild-type (WT) cells. We pinpointed this defect to changes in sterol organization and transbilayer movement within the PM bilayer caused by phospholipid dysregulation, evinced by changes in the abundance and organization of PM lipids. Indeed, deletion of either OSH4, which encodes a sterol/phosphatidylinositol-4-phosphate (PI4P) exchange protein, or SAC1, which encodes a PI4P phosphatase, caused synthetic lethality in Δ-s-tether cells due to disruptions in redundant PI4P and phospholipid regulatory pathways. The growth defect of Δ-s-tether cells was rescued with an artificial "ER-PM staple," a tether assembled from unrelated non-yeast protein domains, indicating that endogenous tether proteins have nonspecific bridging functions. Finally, we discovered that sterols play a role in regulating ER-PM contact site formation. In sterol-depleted cells, levels of the yeast E-Syt tether Tcb3 were induced and ER-PM contact increased dramatically. These results support a model in which ER-PM contact sites provide a nexus for coordinating the complex interrelationship between sterols, sphingolipids, and phospholipids that maintain PM composition and integrity. Almost half of the inner surface area of the yeast plasma membrane (PM) is covered with closely associated cortical endoplasmic reticulum (ER). In yeast and human cells, it has been proposed that ER-anchored tether proteins staple the ER to the PM, creating membrane contact sites at which lipid transport between the ER and PM and membrane lipid synthesis are coordinately regulated, but the potential mechanisms are unclear. Here, we test this idea by creating yeast cells that lack all ER-PM tethers. We find that whereas the bidirectional transport of sterols between the ER and PM is unaffected in these cells, sterols within the PM are disorganized due to disruptions in phospholipid biosynthesis that alter PM lipid composition. In particular, we show that phosphatidylinositol-4-phosphate, a phospholipid needed for intracellular signaling and membrane trafficking, accumulates within the PM. Some of these defects can be rescued by reinstating membrane contacts via expression of an artificial tether. However, correction is also achieved without the creation of contacts by supplementing the growth medium with a precursor of membrane phospholipids. Based on these results, we propose that ER-PM contacts do not play a major role as physical conduits for lipid exchange but rather serve as regulatory interfaces to integrate lipid synthesis pathways.
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Affiliation(s)
- Evan Quon
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Yves Y. Sere
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, United States of America
| | - Neha Chauhan
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, United States of America
| | - Jesper Johansen
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - David P. Sullivan
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, United States of America
| | - Jeremy S. Dittman
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, United States of America
| | - William J. Rice
- Simons Electron Microscopy Center at the New York Structural Biology Center, New York, New York, United States of America
| | - Robin B. Chan
- Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
| | - Gilbert Di Paolo
- Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
- Denali Therapeutics, South San Francisco, California, United States of America
| | - Christopher T. Beh
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
- Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, British Columbia, Canada
- * E-mail: (AKM); (CTB)
| | - Anant K. Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, United States of America
- * E-mail: (AKM); (CTB)
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ER-PM Contacts Restrict Exocytic Sites for Polarized Morphogenesis. Curr Biol 2017; 28:146-153.e5. [PMID: 29290560 DOI: 10.1016/j.cub.2017.11.055] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 10/31/2017] [Accepted: 11/22/2017] [Indexed: 01/04/2023]
Abstract
Spatial control of exocytosis underlies polarized cell morphogenesis. In rod-shaped fission yeast, exocytic vesicles are conveyed along the actin cytoskeleton by myosin V motors toward growing cell ends [1, 2], the major sites for exocytosis. However, actomyosin-based vesicle delivery is dispensable for polarized secretion and cylindrical cell shape of fission yeast [3]. Thus, additional mechanisms should function in the spatial confinement of exocytosis. Here we report a novel role of endoplasmic reticulum (ER)-plasma membrane (PM) contacts in restricting exocytic sites for polarized fission yeast morphogenesis. We show that fission yeast cells deficient in both ER-PM contacts and actomyosin-based secretory vesicle transport display aberrant globular cell shape due to delocalized exocytosis. By artificially manipulating the strength and extent of ER-PM contacts in wild-type and mutant cells that exhibit induced ectopic exocytosis, we demonstrate that exocytosis and ER-PM contact formation are spatially incompatible. Furthermore, extensive ER-PM junctions at the non-growing lateral cell cortex prevent the PM from exocytic vesicle tethering and hence attenuate growth potential at cell sides. We thus propose that ER-PM contacts function as a new morphogenetic module by limiting exocytosis to growing cell tips in fission yeast. A similar mechanism could apply to other cell types with prominent ER-PM contacts.
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Hayes M, Choudhary V, Ojha N, Shin JJ, Han GS, Carman GM, Loewen CJ, Prinz WA, Levine T. Fat storage-inducing transmembrane (FIT or FITM) proteins are related to lipid phosphatase/phosphotransferase enzymes. ACTA ACUST UNITED AC 2017; 5:88-103. [PMID: 29417057 PMCID: PMC5798408 DOI: 10.15698/mic2018.02.614] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Fat storage-inducing transmembrane (FIT or FITM) proteins have been implicated in the partitioning of triacylglycerol to lipid droplets and the budding of lipid droplets from the ER. At the molecular level, the sole relevant interaction is that FITMs directly bind to triacyglycerol and diacylglycerol, but how they function at the molecular level is not known. Saccharomyces cerevisiae has two FITM homologues: Scs3p and Yft2p. Scs3p was initially identified because deletion leads to inositol auxotrophy, with an unusual sensitivity to addition of choline. This strongly suggests a role for Scs3p in phospholipid biosynthesis. Looking at the FITM family as widely as possible, we found that FITMs are widespread throughout eukaryotes, indicating presence in the last eukaryotic common ancestor. Protein alignments also showed that FITM sequences contain the active site of lipid phosphatase/phosphotransferase (LPT) enzymes. This large family transfers phosphate-containing headgroups either between lipids or in exchange for water. We confirmed the prediction that FITMs are related to LPTs by showing that single amino-acid substitutions in the presumptive catalytic site prevented their ability to rescue growth of the mutants on low inositol/high choline media when over-expressed. The substitutions also prevented rescue of other phenotypes associated with loss of FITM in yeast, including mistargeting of Opi1p, defective ER morphology, and aberrant lipid droplet budding. These results suggest that Scs3p, Yft2p and FITMs in general are LPT enzymes involved in an as yet unknown critical step in phospholipid metabolism.
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Affiliation(s)
- Matthew Hayes
- University College London Institute of Ophthalmology. 11-43 Bath Street, London, EC1V 9EL, UK
| | - Vineet Choudhary
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Namrata Ojha
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - John Jh Shin
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Gil-Soo Han
- Department of Food Science and Rutgers Center for Lipid Research, Rutgers University, New Brunswick, New Jersey 08901, USA
| | - George M Carman
- Department of Food Science and Rutgers Center for Lipid Research, Rutgers University, New Brunswick, New Jersey 08901, USA
| | - Christopher Jr Loewen
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - William A Prinz
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Timothy Levine
- University College London Institute of Ophthalmology. 11-43 Bath Street, London, EC1V 9EL, UK
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Stefan CJ, Trimble WS, Grinstein S, Drin G, Reinisch K, De Camilli P, Cohen S, Valm AM, Lippincott-Schwartz J, Levine TP, Iaea DB, Maxfield FR, Futter CE, Eden ER, Judith D, van Vliet AR, Agostinis P, Tooze SA, Sugiura A, McBride HM. Membrane dynamics and organelle biogenesis-lipid pipelines and vesicular carriers. BMC Biol 2017; 15:102. [PMID: 29089042 PMCID: PMC5663033 DOI: 10.1186/s12915-017-0432-0] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Discoveries spanning several decades have pointed to vital membrane lipid trafficking pathways involving both vesicular and non-vesicular carriers. But the relative contributions for distinct membrane delivery pathways in cell growth and organelle biogenesis continue to be a puzzle. This is because lipids flow from many sources and across many paths via transport vesicles, non-vesicular transfer proteins, and dynamic interactions between organelles at membrane contact sites. This forum presents our latest understanding, appreciation, and queries regarding the lipid transport mechanisms necessary to drive membrane expansion during organelle biogenesis and cell growth.
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Affiliation(s)
- Christopher J. Stefan
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT UK
| | - William S. Trimble
- Cell Biology Program, The Hospital for Sick Children and Department of Biochemistry, University of Toronto, Toronto, Canada
| | - Sergio Grinstein
- Cell Biology Program, The Hospital for Sick Children and Department of Biochemistry, University of Toronto, Toronto, Canada
| | - Guillaume Drin
- Université Côte d’Azur, CNRS, Institut de Pharmacologie Moléculaire et Cellulaire, Valbonne, France
| | - Karin Reinisch
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520 USA
| | - Pietro De Camilli
- Department of Neuroscience and Cell Biology, Howard Hughes Medical Institute, Kavli Institute for Neuroscience and Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT 06510 USA
| | | | | | | | - Tim P. Levine
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL UK
| | - David B. Iaea
- Genentech, 1 DNA Way, South San Francisco, CA 94080 USA
| | - Frederick R. Maxfield
- Department of Biochemistry, Weill Cornell Medical College, 1300 York Ave, New York, NY 10065 USA
| | - Clare E. Futter
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL UK
| | - Emily R. Eden
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL UK
| | - Delphine Judith
- Molecular Cell Biology of Autophagy Laboratory, The Francis Crick Institute, London, UK
| | - Alexander R. van Vliet
- Molecular Cell Biology of Autophagy Laboratory, The Francis Crick Institute, London, UK
- Laboratory of Cell Death Research and Therapy, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Patrizia Agostinis
- Laboratory of Cell Death Research and Therapy, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Sharon A. Tooze
- Molecular Cell Biology of Autophagy Laboratory, The Francis Crick Institute, London, UK
| | - Ayumu Sugiura
- Kobe University Graduate School of Medicine, 1-5-6 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047 Japan
| | - Heidi M. McBride
- Montreal Neurological Institute, McGill University, 3801 University Avenue, Montreal, Quebec H3A 2B4 Canada
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36
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Hoffmann PC, Kukulski W. Perspective on architecture and assembly of membrane contact sites. Biol Cell 2017; 109:400-408. [PMID: 28960356 DOI: 10.1111/boc.201700031] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 09/21/2017] [Accepted: 09/21/2017] [Indexed: 01/25/2023]
Abstract
Membrane contact sites (MCS) are platforms of physical contact between different organelles. They are formed through interactions involving lipids and proteins, and function in processes such as calcium and lipid exchange, metabolism and organelle biogenesis. In this article, we discuss emerging questions regarding the architecture, organisation and assembly of MCS, such as: What is the contribution of different components to the interaction between organelles? How is the specific composition of different types of membrane contacts sites established and maintained? How are proteins and lipids spatially organised at MCS and how does that influence their function? How dynamic are MCS on the molecular and ultrastructural level? We highlight current state of research and point out experimental approaches that promise to contribute to a spatiomechanistic understanding of MCS functions.
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Affiliation(s)
- Patrick C Hoffmann
- Cell Biology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK
| | - Wanda Kukulski
- Cell Biology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK
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37
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Gaspar ML, Chang YF, Jesch SA, Aregullin M, Henry SA. Interaction between repressor Opi1p and ER membrane protein Scs2p facilitates transit of phosphatidic acid from the ER to mitochondria and is essential for INO1 gene expression in the presence of choline. J Biol Chem 2017; 292:18713-18728. [PMID: 28924045 DOI: 10.1074/jbc.m117.809970] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 09/08/2017] [Indexed: 12/20/2022] Open
Abstract
In the yeast Saccharomyces cerevisiae, the Opi1p repressor controls the expression of INO1 via the Opi1p/Ino2p-Ino4p regulatory circuit. Inositol depletion favors Opi1p interaction with both Scs2p and phosphatidic acid at the endoplasmic reticulum (ER) membrane. Inositol supplementation, however, favors the translocation of Opi1p from the ER into the nucleus, where it interacts with the Ino2p-Ino4p complex, attenuating transcription of INO1 A strain devoid of Scs2p (scs2Δ) and a mutant, OPI1FFAT, lacking the ability to interact with Scs2p were utilized to examine the specific role(s) of the Opi1p-Scs2p interaction in the regulation of INO1 expression and overall lipid metabolism. Loss of the Opi1p-Scs2p interaction reduced INO1 expression and conferred inositol auxotrophy. Moreover, inositol depletion in strains lacking this interaction resulted in Opi1p being localized to sites of lipid droplet formation, coincident with increased synthesis of triacylglycerol. Supplementation of choline to inositol-depleted growth medium led to decreased TAG synthesis in all three strains. However, in strains lacking the Opi1p-Scs2p interaction, Opi1p remained in the nucleus, preventing expression of INO1 These data support the conclusion that a specific pool of phosphatidic acid, associated with lipid droplet formation in the perinuclear ER, is responsible for the initial rapid exit of Opi1p from the nucleus to the ER and is required for INO1 expression in the presence of choline. Moreover, the mitochondria-specific phospholipid, cardiolipin, was significantly reduced in both strains compromised for Opi1p-Scs2p interaction, indicating that this interaction is required for the transfer of phosphatidic acid from the ER to the mitochondria for cardiolipin synthesis.
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Affiliation(s)
- Maria L Gaspar
- From the Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853
| | - Yu-Fang Chang
- From the Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853
| | - Stephen A Jesch
- From the Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853
| | - Manuel Aregullin
- From the Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853
| | - Susan A Henry
- From the Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853
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38
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The Role of Mitochondria in the Activation/Maintenance of SOCE: Membrane Contact Sites as Signaling Hubs Sustaining Store-Operated Ca2+ Entry. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 993:277-296. [DOI: 10.1007/978-3-319-57732-6_15] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/10/2023]
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39
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Noroviruses Co-opt the Function of Host Proteins VAPA and VAPB for Replication via a Phenylalanine-Phenylalanine-Acidic-Tract-Motif Mimic in Nonstructural Viral Protein NS1/2. mBio 2017; 8:mBio.00668-17. [PMID: 28698274 PMCID: PMC5513711 DOI: 10.1128/mbio.00668-17] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The Norovirus genus contains important human pathogens, but the role of host pathways in norovirus replication is largely unknown. Murine noroviruses provide the opportunity to study norovirus replication in cell culture and in small animals. The human norovirus nonstructural protein NS1/2 interacts with the host protein VAMP-associated protein A (VAPA), but the significance of the NS1/2-VAPA interaction is unexplored. Here we report decreased murine norovirus replication in VAPA- and VAPB-deficient cells. We characterized the role of VAPA in detail. VAPA was required for the efficiency of a step(s) in the viral replication cycle after entry of viral RNA into the cytoplasm but before the synthesis of viral minus-sense RNA. The interaction of VAPA with viral NS1/2 proteins is conserved between murine and human noroviruses. Murine norovirus NS1/2 directly bound the major sperm protein (MSP) domain of VAPA through its NS1 domain. Mutations within NS1 that disrupted interaction with VAPA inhibited viral replication. Structural analysis revealed that the viral NS1 domain contains a mimic of the phenylalanine–phenylalanine-acidic-tract (FFAT) motif that enables host proteins to bind to the VAPA MSP domain. The NS1/2-FFAT mimic region interacted with the VAPA-MSP domain in a manner similar to that seen with bona fide host FFAT motifs. Amino acids in the FFAT mimic region of the NS1 domain that are important for viral replication are highly conserved across murine norovirus strains. Thus, VAPA interaction with a norovirus protein that functionally mimics host FFAT motifs is important for murine norovirus replication. Human noroviruses are a leading cause of gastroenteritis worldwide, but host factors involved in norovirus replication are incompletely understood. Murine noroviruses have been studied to define mechanisms of norovirus replication. Here we defined the importance of the interaction between the hitherto poorly studied NS1/2 norovirus protein and the VAPA host protein. The NS1/2-VAPA interaction is conserved between murine and human noroviruses and was important for early steps in murine norovirus replication. Using structure-function analysis, we found that NS1/2 contains a short sequence that molecularly mimics the FFAT motif that is found in multiple host proteins that bind VAPA. This represents to our knowledge the first example of functionally important mimicry of a host FFAT motif by a microbial protein.
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40
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Chang CL, Chen YJ, Liou J. ER-plasma membrane junctions: Why and how do we study them? BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017; 1864:1494-1506. [PMID: 28554772 DOI: 10.1016/j.bbamcr.2017.05.018] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 05/09/2017] [Accepted: 05/17/2017] [Indexed: 12/17/2022]
Abstract
Endoplasmic reticulum (ER)-plasma membrane (PM) junctions are membrane microdomains important for communication between the ER and the PM. ER-PM junctions were first reported in muscle cells in 1957, but mostly ignored in non-excitable cells due to their scarcity and lack of functional significance. In 2005, the discovery of stromal interaction molecule 1 (STIM1) mediating a universal Ca2+ feedback mechanism at ER-PM junctions in mammalian cells led to a resurgence of research interests toward ER-PM junctions. In the past decade, several major advancements have been made in this emerging topic in cell biology, including the generation of tools for labeling ER-PM junctions and the unraveling of mechanisms underlying regulation and functions of ER-PM junctions. This review summarizes early studies, recently developed tools, and current advances in the characterization and understanding of ER-PM junctions. This article is part of a Special Issue entitled: Membrane Contact Sites edited by Christian Ungermann and Benoit Kornmann.
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Affiliation(s)
- Chi-Lun Chang
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Yu-Ju Chen
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jen Liou
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX 75390, USA.
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41
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Piecing Together the Patchwork of Contact Sites. Trends Cell Biol 2016; 27:214-229. [PMID: 27717534 DOI: 10.1016/j.tcb.2016.08.010] [Citation(s) in RCA: 120] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 08/10/2016] [Accepted: 08/25/2016] [Indexed: 11/23/2022]
Abstract
Contact sites are places where two organelles join together to carry out a shared activity requiring nonvesicular communication. A large number of contact sites have been discovered, and almost any two organelles can contact each other. General rules about contacts include constraints on bridging proteins, with only a minority of bridges physically creating contacts by acting as 'tethers'. The downstream effects of contacts include changing the physical behaviour of organelles, and also forming biochemically heterogeneous subdomains. However, some functions typically localized to contact sites, such as lipid transfer, have no absolute requirement to be situated there. Therefore, the key aspect of contacts is the directness of communication, which allows metabolic channelling and collective regulation.
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42
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Ruggiano A, Mora G, Buxó L, Carvalho P. Spatial control of lipid droplet proteins by the ERAD ubiquitin ligase Doa10. EMBO J 2016; 35:1644-55. [PMID: 27357570 PMCID: PMC4969576 DOI: 10.15252/embj.201593106] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 06/02/2016] [Indexed: 01/20/2023] Open
Abstract
The endoplasmic reticulum (ER) plays a central role in the biogenesis of most membrane proteins. Among these are proteins localized to the surface of lipid droplets (LDs), fat storage organelles delimited by a phospholipid monolayer. The LD monolayer is often continuous with the membrane of the ER allowing certain membrane proteins to diffuse between the two organelles. In these connected organelles, how some proteins concentrate specifically at the surface of LDs is not known. Here, we show that the ERAD ubiquitin ligase Doa10 controls the levels of some LD proteins. Their degradation is dependent on the localization to the ER and appears independent of the folding state. Moreover, we show that by degrading the ER pool of these LD proteins, ERAD contributes to restrict their localization to LDs. The signals for LD targeting and Doa10‐mediated degradation overlap, indicating that these are competing events. This spatial control of protein localization is a novel function of ERAD that might contribute to generate functional diversity in a continuous membrane system.
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Affiliation(s)
- Annamaria Ruggiano
- Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Barcelona, Spain Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Gabriel Mora
- Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Barcelona, Spain Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Laura Buxó
- Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Barcelona, Spain Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Pedro Carvalho
- Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Barcelona, Spain Universitat Pompeu Fabra (UPF), Barcelona, Spain
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43
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Wang P, Richardson C, Hawkins TJ, Sparkes I, Hawes C, Hussey PJ. Plant VAP27 proteins: domain characterization, intracellular localization and role in plant development. THE NEW PHYTOLOGIST 2016; 210:1311-26. [PMID: 27159525 DOI: 10.1111/nph.13857] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Accepted: 12/14/2015] [Indexed: 05/24/2023]
Abstract
The endoplasmic reticulum (ER) is connected to the plasma membrane (PM) through the plant-specific NETWORKED protein, NET3C, and phylogenetically conserved vesicle-associated membrane protein-associated proteins (VAPs). Ten VAP homologues (VAP27-1 to 27-10) can be identified in the Arabidopsis genome and can be divided into three clades. Representative members from each clade were tagged with fluorescent protein and expressed in Nicotiana benthamiana. Proteins from clades I and III localized to the ER as well as to ER/PM contact sites (EPCSs), whereas proteins from clade II were found only at the PM. Some of the VAP27-labelled EPCSs localized to plasmodesmata, and we show that the mobility of VAP27 at EPCSs is influenced by the cell wall. EPCSs closely associate with the cytoskeleton, but their structure is unaffected when the cytoskeleton is removed. VAP27-labelled EPCSs are found in most cell types in Arabidopsis, with the exception of cells in early trichome development. Arabidopsis plants expressing VAP27-GFP fusions exhibit pleiotropic phenotypes, including defects in root hair morphogenesis. A similar effect is also observed in plants expressing VAP27 RNAi. Taken together, these data indicate that VAP27 proteins used at EPCSs are essential for normal ER-cytoskeleton interaction and for plant development.
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Affiliation(s)
- Pengwei Wang
- School of Biological and Biomedical Sciences, Durham University, South Road, Durham, DH1 3LE, UK
| | - Christine Richardson
- School of Biological and Biomedical Sciences, Durham University, South Road, Durham, DH1 3LE, UK
| | - Timothy J Hawkins
- School of Biological and Biomedical Sciences, Durham University, South Road, Durham, DH1 3LE, UK
| | - Imogen Sparkes
- College of Life and Environmental Sciences, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK
| | - Chris Hawes
- Department of Biological and Biomedical Sciences, Oxford Brookes University, Gipsy Lane, Oxford, OX3 0BP, UK
| | - Patrick J Hussey
- School of Biological and Biomedical Sciences, Durham University, South Road, Durham, DH1 3LE, UK
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Gallo A, Vannier C, Galli T. Endoplasmic Reticulum-Plasma Membrane Associations:Structures and Functions. Annu Rev Cell Dev Biol 2016; 32:279-301. [PMID: 27298092 DOI: 10.1146/annurev-cellbio-111315-125024] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Inside eukaryotic cells, membrane contact sites (MCSs), regions where two membrane-bound organelles are apposed at less than 30 nm, generate regions of important lipid and calcium exchange. This review principally focuses on the structure and the function of MCSs between the endoplasmic reticulum (ER) and the plasma membrane (PM). Here we describe how tethering structures form and maintain these junctions and, in some instances, participate in their function. We then discuss recent insights into the mechanisms by which specific classes of proteins mediate nonvesicular lipid exchange between the ER and PM and how such phenomena, already known to be crucial for maintaining organelle identity, are also emerging as regulators of cell growth and development.
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Affiliation(s)
- Alessandra Gallo
- Membrane Traffic in Health & Disease Group (INSERM ERL U950), F-75013 Paris, France;
| | - Christian Vannier
- Membrane Traffic in Health & Disease Group (INSERM ERL U950), F-75013 Paris, France;
| | - Thierry Galli
- Membrane Traffic in Health & Disease Group (INSERM ERL U950), F-75013 Paris, France;
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45
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Okeke E, Dingsdale H, Parker T, Voronina S, Tepikin AV. Endoplasmic reticulum-plasma membrane junctions: structure, function and dynamics. J Physiol 2016; 594:2837-47. [PMID: 26939537 DOI: 10.1113/jp271142] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 02/13/2016] [Indexed: 12/20/2022] Open
Abstract
Endoplasmic reticulum (ER)-plasma membrane (PM) junctions are contact sites between the ER and the PM; the distance between the two organelles in the junctions is below 40 nm and the membranes are connected by protein tethers. A number of molecular tools and technical approaches have been recently developed to visualise, modify and characterise properties of ER-PM junctions. The junctions serve as the platforms for lipid exchange between the organelles and for cell signalling, notably Ca(2+) and cAMP signalling. Vice versa, signalling events regulate the development and properties of the junctions. Two Ca(2+) -dependent mechanisms of de novo formation of ER-PM junctions have been recently described and characterised. The junction-forming proteins and lipids are currently the focus of vigorous investigation. Junctions can be relatively short-lived and simple structures, forming and dissolving on the time scale of a few minutes. However, complex, sophisticated and multifunctional ER-PM junctions, capable of attracting numerous protein residents and other cellular organelles, have been described in some cell types. The road from simplicity to complexity, i.e. the transformation from simple 'nascent' ER-PM junctions to advanced stable multiorganellar complexes, is likely to become an attractive research avenue for current and future junctologists. Another area of considerable research interest is the downstream cellular processes that can be activated by specific local signalling events in the ER-PM junctions. Studies of the cell physiology and indeed pathophysiology of ER-PM junctions have already produced some surprising discoveries, likely to expand with advances in our understanding of these remarkable organellar contact sites.
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Affiliation(s)
- Emmanuel Okeke
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool, L69 3BX, UK
| | - Hayley Dingsdale
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool, L69 3BX, UK
| | - Tony Parker
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool, L69 3BX, UK
| | - Svetlana Voronina
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool, L69 3BX, UK
| | - Alexei V Tepikin
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool, L69 3BX, UK
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New Insight Into the Roles of Membrane Microdomains in Physiological Activities of Fungal Cells. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 325:119-80. [PMID: 27241220 DOI: 10.1016/bs.ircmb.2016.02.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The organization of biological membranes into structurally and functionally distinct lateral microdomains is generally accepted. From bacteria to mammals, laterally compartmentalized membranes seem to be a vital attribute of life. The crucial fraction of our current knowledge about the membrane microdomains has been gained from studies on fungi. In this review we summarize the evidence of the microdomain organization of membranes from fungal cells, with accent on their enormous diversity in composition, temporal dynamics, modes of formation, and recognized engagement in the cell physiology. A special emphasis is laid on the fact that in addition to their other biological functions, membrane microdomains also mediate the communication among different membranes within a eukaryotic cell and coordinate their functions. Involvement of fungal membrane microdomains in stress sensing, regulation of lipid homeostasis, and cell differentiation is discussed more in detail.
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Quon E, Beh CT. Membrane Contact Sites: Complex Zones for Membrane Association and Lipid Exchange. Lipid Insights 2016; 8:55-63. [PMID: 26949334 PMCID: PMC4772907 DOI: 10.4137/lpi.s37190] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 01/28/2016] [Accepted: 01/31/2016] [Indexed: 11/07/2022] Open
Abstract
Lipid transport between membranes within cells involves vesicle and protein carriers, but as agents of nonvesicular lipid transfer, the role of membrane contact sites has received increasing attention. As zones for lipid metabolism and exchange, various membrane contact sites mediate direct associations between different organelles. In particular, membrane contact sites linking the plasma membrane (PM) and the endoplasmic reticulum (ER) represent important regulators of lipid and ion transfer. In yeast, cortical ER is stapled to the PM through membrane-tethering proteins, which establish a direct connection between the membranes. In this review, we consider passive and facilitated models for lipid transfer at PM–ER contact sites. Besides the tethering proteins, we examine the roles of an additional repertoire of lipid and protein regulators that prime and propagate PM–ER membrane association. We conclude that instead of being simple mediators of membrane association, regulatory components of membrane contact sites have complex and multilayered functions.
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Affiliation(s)
- Evan Quon
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada
| | - Christopher T Beh
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada.; Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, BC, Canada
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Chang CL, Liou J. Homeostatic regulation of the PI(4,5)P2-Ca(2+) signaling system at ER-PM junctions. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:862-873. [PMID: 26924250 DOI: 10.1016/j.bbalip.2016.02.015] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Revised: 02/17/2016] [Accepted: 02/19/2016] [Indexed: 10/22/2022]
Abstract
The phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2)-Ca(2+) signaling system is important for cell activation in response to various extracellular stimuli. This signaling system is initiated by receptor-induced hydrolysis of PI(4,5)P2 in the plasma membrane (PM) to generate the soluble second messenger inositol 1,4,5-trisphosphate (IP3). IP3 subsequently triggers the release of Ca(2+) from the endoplasmic reticulum (ER) store to the cytosol to activate Ca(2+)-mediated responses, such as secretion and proliferation. The consumed PM PI(4,5)P2 and ER Ca(2+) must be quickly restored to sustain signaling responses, and to maintain the homeostasis of PI(4,5)P2 and Ca(2+). Since phosphatidylinositol (PI), the precursor lipid for PM PI(4,5)P2, is synthesized in the ER membrane, and a Ca(2+) influx across the PM is required to refill the ER Ca(2+) store, efficient communications between the ER and the PM are critical for the homeostatic regulation of the PI(4,5)P2-Ca(2+) signaling system. This review describes the major findings that established the framework of the PI(4,5)P2-Ca(2+) signaling system, and recent discoveries on feedback control mechanisms at ER-PM junctions that sustain the PI(4,5)P2-Ca(2+) signaling system. Particular emphasis is placed on the characterization of ER-PM junctions where efficient communications between the ER and the PM occur, and the activation mechanisms of proteins that dynamically localize to ER-PM junctions to provide the feedback control during PI(4,5)P2-Ca(2+) signaling, including the ER Ca(2+) sensor STIM1, the extended synaptotagmin E-Syt1, and the PI transfer protein Nir2. This article is part of a Special Issue entitled: The cellular lipid landscape edited by Tim P. Levine and Anant K. Menon.
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Affiliation(s)
- Chi-Lun Chang
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jen Liou
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX 75390, USA.
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VAP, a Versatile Access Point for the Endoplasmic Reticulum: Review and analysis of FFAT-like motifs in the VAPome. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:952-961. [PMID: 26898182 DOI: 10.1016/j.bbalip.2016.02.009] [Citation(s) in RCA: 215] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 02/12/2016] [Accepted: 02/12/2016] [Indexed: 11/24/2022]
Abstract
Dysfunction of VAMP-associated protein (VAP) is associated with neurodegeneration, both Amyotrophic Lateral Sclerosis and Parkinson's disease. Here we summarize what is known about the intracellular interactions of VAP in humans and model organisms. VAP is a simple, small and highly conserved protein on the cytoplasmic face of the endoplasmic reticulum (ER). It is the sole protein on that large organelle that acts as a receptor for cytoplasmic proteins. This may explain the extremely wide range of interacting partners of VAP, with components of many cellular pathways binding it to access the ER. Many proteins that bind VAP also target other intracellular membranes, so VAP is a component of multiple molecular bridges at membrane contact sites between the ER and other organelles. So far approximately 100 proteins have been identified in the VAP interactome (VAPome), of which a small minority have a "two phenylalanines in an acidic tract" (FFAT) motif as it was originally defined. We have analyzed the entire VAPome in humans and yeast using a simple algorithm that identifies many more FFAT-like motifs. We show that approximately 50% of the VAPome binds directly or indirectly via the VAP-FFAT interaction. We also review evidence on pathogenesis in genetic disorders of VAP, which appear to arise from reduced overall VAP levels, leading to ER stress. It is not possible to identify one single interaction that underlies disease. This article is part of a Special Issue entitled: The cellular lipid landscape edited by Tim P. Levine and Anant K. Menon.
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TMEM110 regulates the maintenance and remodeling of mammalian ER-plasma membrane junctions competent for STIM-ORAI signaling. Proc Natl Acad Sci U S A 2015; 112:E7083-92. [PMID: 26644574 DOI: 10.1073/pnas.1521924112] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The stromal interaction molecule (STIM)-ORAI calcium release-activated calcium modulator (ORAI) pathway controls store-dependent calcium entry, a major mechanism of physiological calcium signaling in mammalian cells. The core elements of the pathway are the regulatory protein STIM1, located in the endoplasmic reticulum (ER) membrane, the calcium channel ORAI1 in the plasma membrane, and sites of close contact between the ER and the plasma membrane that permit the two proteins to interact. Research on calcium signaling has centered on STIM1, ORAI1, and a few proteins that directly modulate STIM-ORAI function. However, little is known about proteins that organize ER-plasma membrane junctions for STIM-ORAI-dependent calcium signaling. Here, we report that an ER-resident membrane protein identified in a previous genome-wide RNAi screen, transmembrane protein 110 (TMEM110), regulates the long-term maintenance of ER-plasma membrane junctions and the short-term physiological remodeling of the junctions during store-dependent calcium signaling.
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