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Hoh KL, Mu B, See T, Ng AYE, Ng AQE, Zhang D. VAP-mediated membrane-tethering mechanisms implicate ER-PM contact function in pH homeostasis. Cell Rep 2024; 43:114592. [PMID: 39110593 DOI: 10.1016/j.celrep.2024.114592] [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: 04/16/2024] [Revised: 06/03/2024] [Accepted: 07/22/2024] [Indexed: 09/01/2024] Open
Abstract
Vesicle-associated membrane protein (VAMP)-associated proteins (VAPs) are highly conserved endoplasmic reticulum (ER)-resident proteins that establish ER contacts with multiple membrane compartments in many eukaryotes. However, VAP-mediated membrane-tethering mechanisms remain ambiguous. Here, focusing on fission yeast ER-plasma membrane (PM) contact formation, using systematic interactome analyses and quantitative microscopy, we predict a non-VAP-protein direct binding-based ER-PM coupling. We further reveal that VAP-anionic phospholipid interactions may underlie ER-PM association and define the pH-responsive nature of VAP-tethered membrane contacts. Such conserved interactions with anionic phospholipids are generally defective in amyotrophic lateral sclerosis-associated human VAPB mutant. Moreover, we identify a conserved FFAT-like motif locating at the autoinhibitory hotspot of the essential PM proton pump Pma1. This modulatory VAP-Pma1 interaction appears crucial for pH homeostasis. We thus propose an ingenious strategy for maintaining intracellular pH by coupling Pma1 modulation with pH-sensory ER-PM contacts via VAP-mediated interactions.
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Affiliation(s)
- Kar Ling Hoh
- Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Singapore; Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore
| | - Baicong Mu
- Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Singapore; Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore
| | - Tingyi See
- Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Singapore
| | - Amanda Yunn Ee Ng
- Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Singapore; Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore
| | - Annabel Qi En Ng
- Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Singapore
| | - Dan Zhang
- Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Singapore; Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore.
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2
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Renna L, Stefano G, Puggioni MP, Kim SJ, Lavell A, Froehlich JE, Burkart G, Mancuso S, Benning C, Brandizzi F. ER-associated VAP27-1 and VAP27-3 proteins functionally link the lipid-binding ORP2A at the ER-chloroplast contact sites. Nat Commun 2024; 15:6008. [PMID: 39019917 PMCID: PMC11255254 DOI: 10.1038/s41467-024-50425-7] [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: 12/01/2022] [Accepted: 07/09/2024] [Indexed: 07/19/2024] Open
Abstract
The plant endoplasmic reticulum (ER) contacts heterotypic membranes at membrane contact sites (MCSs) through largely undefined mechanisms. For instance, despite the well-established and essential role of the plant ER-chloroplast interactions for lipid biosynthesis, and the reported existence of physical contacts between these organelles, almost nothing is known about the ER-chloroplast MCS identity. Here we show that the Arabidopsis ER membrane-associated VAP27 proteins and the lipid-binding protein ORP2A define a functional complex at the ER-chloroplast MCSs. Specifically, through in vivo and in vitro association assays, we found that VAP27 proteins interact with the outer envelope membrane (OEM) of chloroplasts, where they bind to ORP2A. Through lipidomic analyses, we established that VAP27 proteins and ORP2A directly interact with the chloroplast OEM monogalactosyldiacylglycerol (MGDG), and we demonstrated that the loss of the VAP27-ORP2A complex is accompanied by subtle changes in the acyl composition of MGDG and PG. We also found that ORP2A interacts with phytosterols and established that the loss of the VAP27-ORP2A complex alters sterol levels in chloroplasts. We propose that, by interacting directly with OEM lipids, the VAP27-ORP2A complex defines plant-unique MCSs that bridge ER and chloroplasts and are involved in chloroplast lipid homeostasis.
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Affiliation(s)
- Luciana Renna
- MSU-DOE Plant Research Lab, Michigan State University, East Lansing, MI, USA
- Department of Horticulture, University of Florence, Florence, Italy
| | - Giovanni Stefano
- MSU-DOE Plant Research Lab, Michigan State University, East Lansing, MI, USA
- Department of Plant Biology, Michigan State University, East Lansing, MI, USA
- Department of Biology, University of Florence, Florence, Italy
| | - Maria Paola Puggioni
- MSU-DOE Plant Research Lab, Michigan State University, East Lansing, MI, USA
- Department of Plant Physiology, Umeå Plant Science Centre, Umeå University, Umeå, Sweden
| | - Sang-Jin Kim
- MSU-DOE Plant Research Lab, Michigan State University, East Lansing, MI, USA
- Department of Plant Biology, Michigan State University, East Lansing, MI, USA
- Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI, USA
| | - Anastasiya Lavell
- MSU-DOE Plant Research Lab, Michigan State University, East Lansing, MI, USA
| | - John E Froehlich
- MSU-DOE Plant Research Lab, Michigan State University, East Lansing, MI, USA
- Biochemistry and Molecular Biology Department, Michigan State University, East Lansing, MI, USA
| | - Graham Burkart
- MSU-DOE Plant Research Lab, Michigan State University, East Lansing, MI, USA
| | - Stefano Mancuso
- Department of Horticulture, University of Florence, Florence, Italy
- Fondazione per il Futuro delle Città, Florence, Italy
| | - Christoph Benning
- MSU-DOE Plant Research Lab, Michigan State University, East Lansing, MI, USA
- Department of Plant Biology, Michigan State University, East Lansing, MI, USA
- Biochemistry and Molecular Biology Department, Michigan State University, East Lansing, MI, USA
| | - Federica Brandizzi
- MSU-DOE Plant Research Lab, Michigan State University, East Lansing, MI, USA.
- Department of Plant Biology, Michigan State University, East Lansing, MI, USA.
- Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI, USA.
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3
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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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4
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Deng Y, Zhu H, Wang Y, Dong Y, Du J, Yu Q, Li M. The Endoplasmic Reticulum-Plasma Membrane Tethering Protein Ice2 Controls Lipid Droplet Size via the Regulation of Phosphatidylcholine in Candida albicans. J Fungi (Basel) 2024; 10:87. [PMID: 38276033 PMCID: PMC10817647 DOI: 10.3390/jof10010087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 01/13/2024] [Accepted: 01/17/2024] [Indexed: 01/27/2024] Open
Abstract
Lipid droplets (LDs) are intracellular organelles that play important roles in cellular lipid metabolism; they change their sizes and numbers in response to both intracellular and extracellular signals. Changes in LD size reflect lipid synthesis and degradation and affect many cellular activities, including energy supply and membrane synthesis. Here, we focused on the function of the endoplasmic reticulum-plasma membrane tethering protein Ice2 in LD dynamics in the fungal pathogen Candida albicans (C. albicans). Nile red staining and size quantification showed that the LD size increased in the ice2Δ/Δ mutant, indicating the critical role of Ice2 in the regulation of LD dynamics. A lipid content analysis further demonstrated that the mutant had lower phosphatidylcholine levels. As revealed with GFP labeling and fluorescence microscopy, the methyltransferase Cho2, which is involved in phosphatidylcholine synthesis, had poorer localization in the plasma membrane in the mutant than in the wild-type strain. Interestingly, the addition of the phosphatidylcholine precursor choline led to the recovery of normal-sized LDs in the mutant. These results indicated that Ice2 regulates LD size by controlling intracellular phosphatidylcholine levels and that endoplasmic reticulum-plasma membrane tethering proteins play a role in lipid metabolism regulation in C. albicans. This study provides significant findings for further investigation of the lipid metabolism in fungi.
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Affiliation(s)
| | | | | | | | | | | | - Mingchun Li
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China; (Y.D.); (H.Z.); (Y.W.); (Y.D.); (J.D.)
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5
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Del Vecchio M, Amado L, Cogan AP, Meert E, Rosseels J, Franssens V, Govers SK, Winderickx J, Montoro AG. Multiple tethers of organelle contact sites are involved in α-synuclein toxicity in yeast. Mol Biol Cell 2023; 34:ar84. [PMID: 37074954 PMCID: PMC10398879 DOI: 10.1091/mbc.e23-01-0029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 04/05/2023] [Accepted: 04/12/2023] [Indexed: 04/20/2023] Open
Abstract
The protein α-synuclein (α-syn) is one of the major factors linked to Parkinson's disease, yet how its misfolding and deposition contribute to the pathology remains largely elusive. Recently, contact sites among organelles were implicated in the development of this disease. Here, we used the budding yeast Saccharomyces cerevisiae, in which organelle contact sites have been characterized extensively, as a model to investigate their role in α-syn cytotoxicity. We observed that lack of specific tethers that anchor the endoplasmic reticulum to the plasma membrane resulted in cells with increased resistance to α-syn expression. Additionally, we found that strains lacking two dual-function proteins involved in contact sites, Mdm10 and Vps39, were resistant to the expression of α-syn. In the case of Mdm10, we found that this is related to its function in mitochondrial protein biogenesis and not to its role as a contact site tether. In contrast, both functions of Vps39, in vesicular transport and as a tether of the vacuole-mitochondria contact site, were required to support α-syn toxicity. Overall, our findings support that interorganelle communication through membrane contact sites is highly relevant for α-syn-mediated toxicity.
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Affiliation(s)
- Mara Del Vecchio
- Department of Biology, Functional Biology Laboratory, KU Leuven, 3001 Heverlee, Belgium
- Department of Biology, Microbial Systems Cell Biology Laboratory, KU Leuven, 3001 Heverlee, Belgium
| | - Lucia Amado
- Department of Biology/Chemistry, Cellular Communication Laboratory, Osnabrück University, 49076 Osnabrück, Germany
| | - Alexandra P. Cogan
- Department of Biology/Chemistry, Cellular Communication Laboratory, Osnabrück University, 49076 Osnabrück, Germany
| | - Els Meert
- Department of Biology, Functional Biology Laboratory, KU Leuven, 3001 Heverlee, Belgium
| | - Joelle Rosseels
- Department of Biology, Functional Biology Laboratory, KU Leuven, 3001 Heverlee, Belgium
| | - Vanessa Franssens
- Department of Biology, Functional Biology Laboratory, KU Leuven, 3001 Heverlee, Belgium
| | - Sander K. Govers
- Department of Biology, Microbial Systems Cell Biology Laboratory, KU Leuven, 3001 Heverlee, Belgium
| | - Joris Winderickx
- Department of Biology, Functional Biology Laboratory, KU Leuven, 3001 Heverlee, Belgium
| | - Ayelén González Montoro
- Department of Biology/Chemistry, Cellular Communication Laboratory, Osnabrück University, 49076 Osnabrück, Germany
- Center of Cellular Nanoanalytics Osnabrück, 49076 Osnabrück, Germany
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6
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Li C, Qian T, He R, Wan C, Liu Y, Yu H. Endoplasmic Reticulum-Plasma Membrane Contact Sites: Regulators, Mechanisms, and Physiological Functions. Front Cell Dev Biol 2021; 9:627700. [PMID: 33614657 PMCID: PMC7889955 DOI: 10.3389/fcell.2021.627700] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Accepted: 01/13/2021] [Indexed: 12/13/2022] Open
Abstract
The endoplasmic reticulum (ER) forms direct membrane contact sites with the plasma membrane (PM) in eukaryotic cells. These ER-PM contact sites play essential roles in lipid homeostasis, ion dynamics, and cell signaling, which are carried out by protein-protein or protein-lipid interactions. Distinct tethering factors dynamically control the architecture of ER-PM junctions in response to intracellular signals or external stimuli. The physiological roles of ER-PM contact sites are dependent on a variety of regulators that individually or cooperatively perform functions in diverse cellular processes. This review focuses on proteins functioning at ER-PM contact sites and highlights the recent progress in their mechanisms and physiological roles.
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Affiliation(s)
- Chenlu Li
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Tiantian Qian
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Ruyue He
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Chun Wan
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO, United States
| | - Yinghui Liu
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Haijia Yu
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
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7
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Lin S, Meng T, Huang H, Zhuang H, He Z, Yang H, Feng D. Molecular machineries and physiological relevance of ER-mediated membrane contacts. Theranostics 2021; 11:974-995. [PMID: 33391516 PMCID: PMC7738843 DOI: 10.7150/thno.51871] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 10/22/2020] [Indexed: 02/06/2023] Open
Abstract
Membrane contact sites (MCSs) are defined as regions where two organelles are closely apposed, and most MCSs associated with each other via protein-protein or protein-lipid interactions. A number of key molecular machinery systems participate in mediating substance exchange and signal transduction, both of which are essential processes in terms of cellular physiology and pathophysiology. The endoplasmic reticulum (ER) is the largest reticulum network within the cell and has extensive communication with other cellular organelles, including the plasma membrane (PM), mitochondria, Golgi, endosomes and lipid droplets (LDs). The contacts and reactions between them are largely mediated by various protein tethers and lipids. Ions, lipids and even proteins can be transported between the ER and neighboring organelles or recruited to the contact site to exert their functions. This review focuses on the key molecules involved in the formation of different contact sites as well as their biological functions.
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Affiliation(s)
- Shiyin Lin
- Affiliated Cancer Hospital and Institute of Guangzhou Medical University, Guangzhou Municipal and Guangdong Provincial Key Laboratory of Protein Modification and Degradation, School of Basic Medical Sciences, Guangzhou Medical University, 511436, Guangzhou, China
- State Key Laboratory of Respiratory Disease, Guangzhou Medical University, 511436, Guangzhou, China
| | - Tian Meng
- Affiliated Cancer Hospital and Institute of Guangzhou Medical University, Guangzhou Municipal and Guangdong Provincial Key Laboratory of Protein Modification and Degradation, School of Basic Medical Sciences, Guangzhou Medical University, 511436, Guangzhou, China
- State Key Laboratory of Respiratory Disease, Guangzhou Medical University, 511436, Guangzhou, China
| | - Haofeng Huang
- Affiliated Cancer Hospital and Institute of Guangzhou Medical University, Guangzhou Municipal and Guangdong Provincial Key Laboratory of Protein Modification and Degradation, School of Basic Medical Sciences, Guangzhou Medical University, 511436, Guangzhou, China
| | - Haixia Zhuang
- Affiliated Cancer Hospital and Institute of Guangzhou Medical University, Guangzhou Municipal and Guangdong Provincial Key Laboratory of Protein Modification and Degradation, School of Basic Medical Sciences, Guangzhou Medical University, 511436, Guangzhou, China
| | - Zhengjie He
- Affiliated Cancer Hospital and Institute of Guangzhou Medical University, Guangzhou Municipal and Guangdong Provincial Key Laboratory of Protein Modification and Degradation, School of Basic Medical Sciences, Guangzhou Medical University, 511436, Guangzhou, China
- State Key Laboratory of Respiratory Disease, Guangzhou Medical University, 511436, Guangzhou, China
| | - Huan Yang
- Department of Pulmonary and Critical Care Medicine, Hunan Provincial People's Hospital, The First Affiliated Hospital of Hunan Normal University, Changsha 410021, China
| | - Du Feng
- Affiliated Cancer Hospital and Institute of Guangzhou Medical University, Guangzhou Municipal and Guangdong Provincial Key Laboratory of Protein Modification and Degradation, School of Basic Medical Sciences, Guangzhou Medical University, 511436, Guangzhou, China
- State Key Laboratory of Respiratory Disease, Guangzhou Medical University, 511436, Guangzhou, China
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8
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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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9
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Pankratenko AV, Atabekova AK, Morozov SY, Solovyev AG. Membrane Contacts in Plasmodesmata: Structural Components and Their Functions. BIOCHEMISTRY (MOSCOW) 2020; 85:531-544. [DOI: 10.1134/s0006297920050028] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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10
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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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11
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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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12
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Zhao YG, Liu N, Miao G, Chen Y, Zhao H, Zhang H. The ER Contact Proteins VAPA/B Interact with Multiple Autophagy Proteins to Modulate Autophagosome Biogenesis. Curr Biol 2018; 28:1234-1245.e4. [PMID: 29628370 DOI: 10.1016/j.cub.2018.03.002] [Citation(s) in RCA: 121] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 02/09/2018] [Accepted: 03/01/2018] [Indexed: 02/03/2023]
Abstract
The endoplasmic reticulum (ER) is the site of biogenesis of the isolation membrane (IM, autophagosome precursor) and forms extensive contacts with IMs during their expansion into double-membrane autophagosomes. Little is known about the molecular mechanism underlying the formation and/or maintenance of the ER/IM contact. The integral ER proteins VAPA and VAPB (VAPs) participate in establishing ER contacts with multiple membranes by interacting with different tethers. Here, we demonstrate that VAPs also modulate ER/IM contact formation. Depletion of VAPs impairs progression of IMs into autophagosomes. Upon autophagy induction, VAPs are recruited to autophagosome formation sites on the ER, a process mediated by their interactions with FIP200 and PI(3)P. VAPs directly interact with FIP200 and ULK1 through their conserved FFAT motifs and stabilize the ULK1/FIP200 complex at the autophagosome formation sites on the ER. The formation of ULK1 puncta is significantly reduced by VAPA/B depletion. VAPs also interact with WIPI2 and enhance the formation of the WIPI2/FIP200 ER/IM tethering complex. Depletion of VMP1, which increases the ER/IM contact, greatly elevates the interaction of VAPs with these autophagy proteins. The VAPB P56S mutation, which is associated with amyotrophic lateral sclerosis, reduces the ULK1/FIP200 interaction and impairs autophagy at an early step, similar to the effect seen in VAPA/B-depleted cells. Our study reveals that VAPs directly interact with multiple ATG proteins, thereby contributing to ER/IM contact formation for autophagosome biogenesis.
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Affiliation(s)
- Yan G Zhao
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Nan Liu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Guangyan Miao
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Yong Chen
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Hongyu Zhao
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Hong Zhang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China; College of Life Sciences, University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049, China.
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13
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Pitzalis N, Heinlein M. The roles of membranes and associated cytoskeleton in plant virus replication and cell-to-cell movement. JOURNAL OF EXPERIMENTAL BOTANY 2017; 69:117-132. [PMID: 29036578 DOI: 10.1093/jxb/erx334] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The infection of plants by viruses depends on cellular mechanisms that support the replication of the viral genomes, and the cell-to-cell and systemic movement of the virus via plasmodesmata (PD) and the connected phloem. While the propagation of some viruses requires the conventional endoplasmic reticulum (ER)-Golgi pathway, others replicate and spread between cells in association with the ER and are independent of this pathway. Using selected viruses as examples, this review re-examines the involvement of membranes and the cytoskeleton during virus infection and proposes potential roles of class VIII myosins and membrane-tethering proteins in controlling viral functions at specific ER subdomains, such as cortical microtubule-associated ER sites, ER-plasma membrane contact sites, and PD.
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14
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Ho CM, Paciorek T, Abrash E, Bergmann D. Modulators of Stomatal Lineage Signal Transduction Alter Membrane Contact Sites and Reveal Specialization among ERECTA Kinases. Dev Cell 2016; 38:345-57. [DOI: 10.1016/j.devcel.2016.07.016] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2015] [Revised: 05/18/2016] [Accepted: 07/21/2016] [Indexed: 11/29/2022]
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15
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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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16
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Tilsner J, Nicolas W, Rosado A, Bayer EM. Staying Tight: Plasmodesmal Membrane Contact Sites and the Control of Cell-to-Cell Connectivity in Plants. ANNUAL REVIEW OF PLANT BIOLOGY 2016; 67:337-64. [PMID: 26905652 DOI: 10.1146/annurev-arplant-043015-111840] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Multicellularity differs in plants and animals in that the cytoplasm, plasma membrane, and endomembrane of plants are connected between cells through plasmodesmal pores. Plasmodesmata (PDs) are essential for plant life and serve as conduits for the transport of proteins, small RNAs, hormones, and metabolites during developmental and defense signaling. They are also the only pathways available for viruses to spread within plant hosts. The membrane organization of PDs is unique, characterized by the close apposition of the endoplasmic reticulum and the plasma membrane and spoke-like filamentous structures linking the two membranes, which define PDs as membrane contact sites (MCSs). This specialized membrane arrangement is likely critical for PD function. Here, we review how PDs govern developmental and defensive signaling in plants, compare them with other types of MCSs, and discuss in detail the potential functional significance of the MCS nature of PDs.
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Affiliation(s)
- Jens Tilsner
- Biomedical Sciences Research Complex, University of St Andrews, Fife KY16 9ST, United Kingdom;
- Cell and Molecular Sciences, The James Hutton Institute, Dundee DD2 5DA, United Kingdom
| | - William Nicolas
- Laboratory of Membrane Biogenesis, UMR5200 CNRS, University of Bordeaux, 33883 Villenave d'Ornon Cedex, France; ,
| | - Abel Rosado
- Department of Botany, Faculty of Sciences, University of British Columbia, Vancouver V6T 1Z4, Canada;
| | - Emmanuelle M Bayer
- Laboratory of Membrane Biogenesis, UMR5200 CNRS, University of Bordeaux, 33883 Villenave d'Ornon Cedex, France; ,
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17
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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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18
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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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19
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Masuda M, Oshima A, Noguchi T, Kagiwada S. Induction of intranuclear membranes by overproduction of Opi1p and Scs2p, regulators for yeast phospholipid biosynthesis, suggests a mechanism for Opi1p nuclear translocation. J Biochem 2015; 159:351-61. [PMID: 26590299 DOI: 10.1093/jb/mvv105] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 09/24/2015] [Indexed: 12/17/2022] Open
Abstract
In the yeast Saccharomyces cerevisiae, the expression of phospholipid biosynthetic genes is suppressed by the Opi1p negative regulator. Opi1p enters into the nucleoplasm from the nuclear membrane to suppress the gene expression under repressing conditions. The binding of Opi1p to the nuclear membrane requires an integral membrane protein, Scs2p and phosphatidic acid (PA). Although it is demonstrated that the association of Opi1p with membranes is affected by PA levels, how Opi1p dissociates from Scs2p is unknown. Here, we found that fluorescently labelled Opi1p accumulated on a perinuclear region in an Scs2p-dependent manner. Electron microscopic analyses indicated that the perinuclear region consists of intranuclear membranes, which may be formed by the invagination of the nuclear membrane due to the accumulation of Opi1p and Scs2p in a restricted area. As expected, localization of Opi1p and Scs2p in the intranuclear membranes was detected by immunoelectron microscopy. Biochemical analysis showed that Opi1p recovered in the membrane fraction was detergent insoluble while Scs2p was soluble, implying that Opi1p behaves differently from Scs2p in the fraction. We hypothesize that Opi1p dissociates from Scs2p after targeting to the nuclear membrane, making it possible to be released from the membrane quickly when PA levels decrease.
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Affiliation(s)
- Miki Masuda
- Department of Biological Sciences, Faculty of Science, Nara Women's University, Nara 630-8506, Japan
| | - Ayaka Oshima
- Department of Biological Sciences, Faculty of Science, Nara Women's University, Nara 630-8506, Japan
| | - Tetsuko Noguchi
- Department of Biological Sciences, Faculty of Science, Nara Women's University, Nara 630-8506, Japan
| | - Satoshi Kagiwada
- Department of Biological Sciences, Faculty of Science, Nara Women's University, Nara 630-8506, Japan
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20
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Henne WM, Liou J, Emr SD. Molecular mechanisms of inter-organelle ER–PM contact sites. Curr Opin Cell Biol 2015; 35:123-30. [DOI: 10.1016/j.ceb.2015.05.001] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 04/23/2015] [Accepted: 05/01/2015] [Indexed: 10/23/2022]
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21
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Kajiwara K, Ikeda A, Aguilera-Romero A, Castillon GA, Kagiwada S, Hanada K, Riezman H, Muñiz M, Funato K. Osh proteins regulate COPII-mediated vesicular transport of ceramide from the endoplasmic reticulum in budding yeast. J Cell Sci 2013; 127:376-87. [PMID: 24213531 DOI: 10.1242/jcs.132001] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Lipids synthesized at the endoplasmic reticulum (ER) are delivered to the Golgi by vesicular and non-vesicular pathways. ER-to-Golgi transport is crucial for maintaining the different membrane lipid composition and identities of organelles. Despite their importance, mechanisms regulating transport remain elusive. Here we report that in yeast coat protein complex II (COPII) vesicle-mediated transport of ceramide from the ER to the Golgi requires oxysterol-binding protein homologs, Osh proteins, which have been implicated in lipid homeostasis. Because Osh proteins are not required to transport proteins to the Golgi, these results indicate a specific requirement for the Osh proteins in the transport of ceramide. In addition, we provide evidence that Osh proteins play a negative role in COPII vesicle biogenesis. Together, our data suggest that ceramide transport and sphingolipid levels between the ER and Golgi are maintained by two distinct functions of Osh proteins, which negatively regulate COPII vesicle formation and positively control a later stage, presumably fusion of ceramide-enriched vesicles with Golgi compartments.
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Affiliation(s)
- Kentaro Kajiwara
- Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Hiroshima 739-8528, Japan
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22
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Abstract
Phosphoinositides (PIs) make up only a small fraction of cellular phospholipids, yet they control almost all aspects of a cell's life and death. These lipids gained tremendous research interest as plasma membrane signaling molecules when discovered in the 1970s and 1980s. Research in the last 15 years has added a wide range of biological processes regulated by PIs, turning these lipids into one of the most universal signaling entities in eukaryotic cells. PIs control organelle biology by regulating vesicular trafficking, but they also modulate lipid distribution and metabolism via their close relationship with lipid transfer proteins. PIs regulate ion channels, pumps, and transporters and control both endocytic and exocytic processes. The nuclear phosphoinositides have grown from being an epiphenomenon to a research area of its own. As expected from such pleiotropic regulators, derangements of phosphoinositide metabolism are responsible for a number of human diseases ranging from rare genetic disorders to the most common ones such as cancer, obesity, and diabetes. Moreover, it is increasingly evident that a number of infectious agents hijack the PI regulatory systems of host cells for their intracellular movements, replication, and assembly. As a result, PI converting enzymes began to be noticed by pharmaceutical companies as potential therapeutic targets. This review is an attempt to give an overview of this enormous research field focusing on major developments in diverse areas of basic science linked to cellular physiology and disease.
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Affiliation(s)
- Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
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23
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Forrest S, Chai A, Sanhueza M, Marescotti M, Parry K, Georgiev A, Sahota V, Mendez-Castro R, Pennetta G. Increased levels of phosphoinositides cause neurodegeneration in a Drosophila model of amyotrophic lateral sclerosis. Hum Mol Genet 2013; 22:2689-704. [PMID: 23492670 PMCID: PMC3674808 DOI: 10.1093/hmg/ddt118] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The Vesicle-associated membrane protein (VAMP)-Associated Protein B (VAPB) is the causative gene of amyotrophic lateral sclerosis 8 (ALS8) in humans. Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by selective death of motor neurons leading to spasticity, muscle atrophy and paralysis. VAP proteins have been implicated in various cellular processes, including intercellular signalling, synaptic remodelling, lipid transport and membrane trafficking and yet, the molecular mechanisms underlying ALS8 pathogenesis remain poorly understood. We identified the conserved phosphoinositide phosphatase Sac1 as a Drosophila VAP (DVAP)-binding partner and showed that DVAP is required to maintain normal levels of phosphoinositides. Downregulating either Sac1 or DVAP disrupts axonal transport, synaptic growth, synaptic microtubule integrity and the localization of several postsynaptic components. Expression of the disease-causing allele (DVAP-P58S) in a fly model for ALS8 induces neurodegeneration, elicits synaptic defects similar to those of DVAP or Sac1 downregulation and increases phosphoinositide levels. Consistent with a role for Sac1-mediated increase of phosphoinositide levels in ALS8 pathogenesis, we found that Sac1 downregulation induces neurodegeneration in a dosage-dependent manner. In addition, we report that Sac1 is sequestered into the DVAP-P58S-induced aggregates and that reducing phosphoinositide levels rescues the neurodegeneration and suppresses the synaptic phenotypes associated with DVAP-P58S transgenic expression. These data underscore the importance of DVAP–Sac1 interaction in controlling phosphoinositide metabolism and provide mechanistic evidence for a crucial role of phosphoinositide levels in VAP-induced ALS.
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Affiliation(s)
- Stuart Forrest
- Center for Integrative Physiology and Euan MacDonald Center for Motor Neuron Disease Research, School of Biomedical Sciences, University of Edinburgh, Edinburgh, UK
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24
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Shetty A, Swaminathan A, Lopes JM. Transcription Regulation of a Yeast Gene from a Downstream Location. J Mol Biol 2013; 425:457-65. [DOI: 10.1016/j.jmb.2012.11.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Revised: 10/26/2012] [Accepted: 11/13/2012] [Indexed: 11/29/2022]
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25
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Manford A, Stefan C, Yuan H, MacGurn J, Emr S. ER-to-Plasma Membrane Tethering Proteins Regulate Cell Signaling and ER Morphology. Dev Cell 2012; 23:1129-40. [DOI: 10.1016/j.devcel.2012.11.004] [Citation(s) in RCA: 339] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Revised: 10/05/2012] [Accepted: 11/11/2012] [Indexed: 10/27/2022]
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26
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Zhang D, Vjestica A, Oliferenko S. Plasma membrane tethering of the cortical ER necessitates its finely reticulated architecture. Curr Biol 2012; 22:2048-52. [PMID: 23041194 DOI: 10.1016/j.cub.2012.08.047] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Revised: 08/02/2012] [Accepted: 08/22/2012] [Indexed: 11/27/2022]
Abstract
The cortical endoplasmic reticulum (ER) is an intricate network of tubules and cisternae tightly associated with the plasma membrane (PM) in plants, yeast, and the excitable cell types in metazoans [1-5]. How the ER is attached to the cell cortex and what necessitates its highly reticulated architecture remain largely unknown. Here, we identify the integral ER vesicle-associated membrane protein-associated proteins (VAPs), previously shown to control the composition of phosphoinositides at the ER-PM contact sites [6, 7], as major players in sustaining the ER-PM tethering in fission yeast. We show that genetic conversion of the reticulated ER structure to the cisternal morphology shields large areas of the PM, preventing the actomyosin division ring assembly at the equatorial cortex. Using a combination of VAP mutants where the cortical ER is detached from the PM and a set of artificial ER-PM tethers suppressing this phenotype, we demonstrate that the PM footprint of the cortical ER is functionally insulated from the cytosol. In cells with prominent ER-PM contacts, fine reticulation of the ER network may have emerged as a critical adaptation enabling a uniform access of peripheral protein complexes to the inner surface of the plasma membrane.
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Affiliation(s)
- Dan Zhang
- Temasek Life Sciences Laboratory, 1 Research Link, Singapore 117604, Singapore
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27
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Schuh AL, Audhya A. Phosphoinositide signaling during membrane transport in Saccharomyces cerevisiae. Subcell Biochem 2012; 59:35-63. [PMID: 22374087 DOI: 10.1007/978-94-007-3015-1_2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Phosphatidylinositol (PI) is distinct from other phospholipids, possessing a head group that can be modified by phosphorylation at multiple positions to generate unique signaling molecules collectively known as phosphoinositides. The set of kinases and phosphatases that regulate PI metabolism are conserved throughout eukaryotic evolution, and numerous studies have demonstrated that phosphoinositides regulate a diverse spectrum of cellular processes, including vesicle transport, cell proliferation, and cytoskeleton organization. Over the past two decades, nearly all PI derivatives have been shown to interact directly with cellular proteins to affect their localization and/or activity. Additionally, there is growing evidence, which suggests that phosphoinositides may also affect local membrane topology. Here, we focus on the role of phosphoinositides in membrane trafficking and underscore the significant role that yeast has played in the field.
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Affiliation(s)
- Amber L Schuh
- Department of Biomolecular Chemistry, University of Wisconsin-Madison Medical School, 1300 University Avenue, WI, 53706, Madison, USA
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28
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Stefan CJ, Manford AG, Baird D, Yamada-Hanff J, Mao Y, Emr SD. Osh proteins regulate phosphoinositide metabolism at ER-plasma membrane contact sites. Cell 2011; 144:389-401. [PMID: 21295699 DOI: 10.1016/j.cell.2010.12.034] [Citation(s) in RCA: 368] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Revised: 09/17/2010] [Accepted: 12/10/2010] [Indexed: 12/17/2022]
Abstract
Sac1 phosphoinositide (PI) phosphatases are essential regulators of PI-signaling networks. Yeast Sac1, an integral endoplasmic reticulum (ER) membrane protein, controls PI4P levels at the ER, Golgi, and plasma membrane (PM). Whether Sac1 can act in trans and turn over PI4P at the Golgi and PM from the ER remains a paradox. We find that Sac1-mediated PI4P metabolism requires the oxysterol-binding homology (Osh) proteins. The PH domain-containing family member, Osh3, localizes to PM/ER membrane contact sites dependent upon PM PI4P levels. We reconstitute Osh protein-stimulated Sac1 PI phosphatase activity in vitro. We also show that the ER membrane VAP proteins, Scs2/Scs22, control PM PI4P levels and Sac1 activity in vitro. We propose that Osh3 functions at ER/PM contact sites as both a sensor of PM PI4P and an activator of the ER Sac1 phosphatase. Our findings further suggest that the conserved Osh proteins control PI metabolism at additional membrane contact sites.
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Affiliation(s)
- Christopher J Stefan
- Weill Institute for Cell & Molecular Biology, Department of Molecular Biology & Genetics, Cornell University, Ithaca, NY 14853, USA
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29
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Murray JD, Muni RRD, Torres-Jerez I, Tang Y, Allen S, Andriankaja M, Li G, Laxmi A, Cheng X, Wen J, Vaughan D, Schultze M, Sun J, Charpentier M, Oldroyd G, Tadege M, Ratet P, Mysore KS, Chen R, Udvardi MK. Vapyrin, a gene essential for intracellular progression of arbuscular mycorrhizal symbiosis, is also essential for infection by rhizobia in the nodule symbiosis of Medicago truncatula. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2011; 65:244-52. [PMID: 21223389 DOI: 10.1111/j.1365-313x.2010.04415.x] [Citation(s) in RCA: 123] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Intracellular invasion of root cells is required for the establishment of successful endosymbioses in legumes of both arbuscular mycorrhizal (AM) fungi and rhizobial bacteria. In both interactions a requirement for successful entry is the activation of a common signalling pathway that includes five genes required to generate calcium oscillations and two genes required for the perception of the calcium response. Recently, it has been discovered that in Medicago truncatula, the Vapyrin (VPY) gene is essential for the establishment of the arbuscular mycorrhizal symbiosis. Here, we show by analyses of mutants that the same gene is also required for rhizobial colonization and nodulation. VPY encodes a protein featuring a Major Sperm Protein domain, typically featured on proteins involved in membrane trafficking and biogenesis, and a series of ankyrin repeats. Plants mutated in this gene have abnormal rhizobial infection threads and fewer nodules, and in the case of interactions with AM fungi, epidermal penetration defects and aborted arbuscule formation. Calcium spiking in root hairs in response to supplied Nod factors is intact in the vpy-1 mutant. This, and the elevation of VPY transcripts upon application of Nod factors which we show to be dependent on NFP, DMI1, and DMI3, indicates that VPY acts downstream of the common signalling pathway.
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Affiliation(s)
- Jeremy D Murray
- Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA
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Nakamichi S, Yamanaka K, Suzuki M, Watanabe T, Kagiwada S. Human VAPA and the yeast VAP Scs2p with an altered proline distribution can phenocopy amyotrophic lateral sclerosis-associated VAPB(P56S). Biochem Biophys Res Commun 2010; 404:605-9. [PMID: 21144830 DOI: 10.1016/j.bbrc.2010.12.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2010] [Accepted: 12/02/2010] [Indexed: 10/18/2022]
Abstract
A human isoform of the vesicle-associated membrane protein-associated proteins (VAPs), VAPB, causes amyotrophic lateral sclerosis eight due to the missense mutation of Pro-56, whereas human VAPA and the yeast VAP Scs2p proteins are not significantly affected by similar mutations. We have found that VAPA and Scs2p have three prolines present in a conserved region however VAPB has only two prolines in this region. Consequently, this mutation in VAPB (VAPB(P56S)) leaves a single proline in this region whereas other VAPs can retain two proline residues even if the proline equivalent to the Pro-56 is substituted. When Scs2p and VAPA were mutated to be equivalent to VAPB(P56S) in terms of the distribution of proline residues in this region, Scs2p became inactive and aggregated, and VAPA localize to membranous aggregates indistinguishable from those induced by VAPB(P56S). This suggests that the appropriate distribution of three conserved prolines, not the existence of a particular proline, confers VAPA and Scs2p resistance to the Pro-56 mutation and, therefore, is critical for VAP activities.
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Affiliation(s)
- Shoko Nakamichi
- Department of Biological Science and Environment, Graduate School of Humanities and Sciences, Nara Women's University, Nara 630-8506, Japan
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Derepression of INO1 transcription requires cooperation between the Ino2p-Ino4p heterodimer and Cbf1p and recruitment of the ISW2 chromatin-remodeling complex. EUKARYOTIC CELL 2010; 9:1845-55. [PMID: 20935143 DOI: 10.1128/ec.00144-10] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The Saccharomyces cerevisiae INO1 gene encodes the structural enzyme inositol-3-phosphate synthase for the synthesis de novo of inositol and inositol-containing phospholipids. The transcription of INO1 is completely derepressed in the absence of inositol and choline (I(-) C(-)). Derepression requires the binding of the Ino2p-Ino4p basic helix-loop-helix (bHLH) heterodimer to the UAS(INO) promoter element. We report here the requirement of a third bHLH protein, centromere-binding factor 1 (Cbf1p), for the complete derepression of INO1 transcription. We found that Cbf1p regulates INO1 transcription by binding to sites distal to the INO1 promoter and encompassing the upstream SNA3 open reading frame (ORF) and promoter. The binding of Cbf1p requires Ino2p-Ino4p binding to the UAS(INO) sites in the INO1 promoter and vice versa, suggesting a cooperative mechanism. Furthermore, Cbf1p binding to the upstream sites was required for the binding of the ISW2 chromatin-remodeling complex to the Ino2p-Ino4p-binding sites on the INO1 promoter. Consistent with this, ISW2 was also required for the complete derepression of INO1 transcription.
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Current awareness on yeast. Yeast 2008. [DOI: 10.1002/yea.1563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Lev S, Ben Halevy D, Peretti D, Dahan N. The VAP protein family: from cellular functions to motor neuron disease. Trends Cell Biol 2008; 18:282-90. [PMID: 18468439 DOI: 10.1016/j.tcb.2008.03.006] [Citation(s) in RCA: 171] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2008] [Revised: 03/24/2008] [Accepted: 03/31/2008] [Indexed: 01/10/2023]
Abstract
The VAMP-associated proteins (VAPs) are highly conserved integral endoplasmic reticulum membrane proteins implicated in diverse cellular functions, including the regulation of lipid transport and homeostasis, membrane trafficking, neurotransmitter release, stabilization of presynaptic microtubules, and the unfolded protein response. Recently, a single missense mutation within the human VAP-B gene was identified in three forms of familial motor neuron disease. In this review, we integrate results from studies of yeast, fly and mammalian VAPs that provide insight into the structural features of these proteins, the network of VAP-interacting proteins, their possible physiological functions, and their involvement in motor neuron disease.
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Affiliation(s)
- Sima Lev
- The Molecular Cell Biology Department, Weizmann Institute of Science, Rehovot 76100, Israel.
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