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Balla T. Phosphatidylinositol 4-phosphate; A minor lipid with multiple personalities. Biochim Biophys Acta Mol Cell Biol Lipids 2025; 1870:159615. [PMID: 40262701 DOI: 10.1016/j.bbalip.2025.159615] [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: 02/26/2025] [Revised: 04/08/2025] [Accepted: 04/18/2025] [Indexed: 04/24/2025]
Abstract
Phosphorylated products of phosphatidylinositol (PI), named Diphosphoinositide (DPI) and triphosphoinositide (TPI) were identified long time ago and found to exhibit high turnover rates based on their rapid 32P-phosphate labeling. The PI kinase activities that were responsible for their production were subsequently identified and found to be associated with different organelle membranes, including the plasma membrane. These activities were then linked with a certain group of cell surface receptors that activated phospholipase C enzymes to hydrolyze PI and used calcium or cGMP as a second messenger. This visionary concept was introduced in the seminal BBA review written by Robert Michell, exactly 50 years ago. The enzymology and functional diversity of PI 4-phosphate (PI4P) (the term that has replaced DPI) has since underwent an expansion that could not have been foreseen. In this review I will attempt to revisit this expansion with some historical reflections celebrating the 50th anniversary of the Michell review.
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Affiliation(s)
- Tamas Balla
- Section on Molecular Signal Transduction, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
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2
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Fresquez T, Tam BM, Eshelman SC, Moritz OL, Robichaux MA, Deretic D. Rabin8 phosphorylated by NDR2, the canine early retinal degeneration gene product, directs rhodopsin Golgi-to-cilia trafficking. J Cell Sci 2025; 138:JCS263401. [PMID: 39774853 PMCID: PMC11828469 DOI: 10.1242/jcs.263401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2024] [Accepted: 12/20/2024] [Indexed: 01/11/2025] Open
Abstract
The Rab11-Rabin8-Rab8 ciliogenesis complex regulates the expansion of cilia-derived light-sensing organelles, the rod outer segments, via post-Golgi rhodopsin transport carriers (RTCs). Rabin8 (also known as RAB3IP), an effector of Rab11 proteins and a nucleotide exchange factor (GEF) for Rab8 proteins, is phosphorylated at S272 by NDR2 kinase (also known as STK38L), the canine early retinal degeneration (erd) gene product linked to the human ciliopathy Leber congenital amaurosis (LCA). Here, we define the step at which NDR2 phosphorylates Rabin8 and regulates Rab11-to-Rab8 succession in Xenopus laevis transgenic rod photoreceptors expressing human GFP-Rabin8 and its mutants. GFP-Rabin8 accumulated with endogenous Rabin8 at the Golgi-apposed exit sites (GESs), also known as the trans-Golgi network (TGN). Rabin8 mutants deficient in Rab11 binding prevented membrane association of GFP-Rabin8. GFP-Rabin8 and NDR2 kinase both interacted with the RTC-associated R-SNARE VAMP7 at the trans-Golgi and the GESs. Here, GFP-Rabin8 and the phosphomimetic GFP-Rabin8-S272E integrated into RTCs, which were subsequently functionalized by Rabin8 Rab8 GEF activity. Non-phosphorylatable GFP-Rabin8-S272A caused significant GES enlargement and deformation, possibly leading to unconventional membrane advancement toward the cilium, bypassing RTCs. Rabin8 phosphorylation loss due to an NDR2 gene disruption thereby likely causes dysfunctional rhodopsin Golgi-to-cilia trafficking underlying retinal degeneration and early-onset blindness.
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Affiliation(s)
- Theresa Fresquez
- Department of Ophthalmology and Visual Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA
| | - Beatrice M. Tam
- Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, BC V5Z 3N9, Canada
| | - Shannon C. Eshelman
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia 26506, USA
| | - Orson L. Moritz
- Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, BC V5Z 3N9, Canada
| | - Michael A. Robichaux
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia 26506, USA
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia 26506, USA
| | - Dusanka Deretic
- Department of Ophthalmology and Visual Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA
- Department of Cell Biology and Physiology, University of New Mexico, Albuquerque, New Mexico 87131, USA
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3
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Dong J, Tong W, Liu M, Liu M, Liu J, Jin X, Chen J, Jia H, Gao M, Wei M, Duan Y, Zhong X. Endosomal traffic disorders: a driving force behind neurodegenerative diseases. Transl Neurodegener 2024; 13:66. [PMID: 39716330 DOI: 10.1186/s40035-024-00460-7] [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: 05/15/2024] [Accepted: 12/05/2024] [Indexed: 12/25/2024] Open
Abstract
Endosomes are crucial sites for intracellular material sorting and transportation. Endosomal transport is a critical process involved in the selective uptake, processing, and intracellular transport of substances. The equilibrium between endocytosis and circulation mediated by the endosome-centered transport pathway plays a significant role in cell homeostasis, signal transduction, and immune response. In recent years, there have been hints linking endosomal transport abnormalities to neurodegenerative diseases, including Alzheimer's disease. Nonetheless, the related mechanisms remain unclear. Here, we provide an overview of endosomal-centered transport pathways and highlight potential physiological processes regulated by these pathways, with a particular focus on the correlation of endosomal trafficking disorders with common pathological features of neurodegenerative diseases. Additionally, we summarize potential therapeutic agents targeting endosomal trafficking for the treatment of neurodegenerative diseases.
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Affiliation(s)
- Jianru Dong
- School of Pharmacy, China Medical University, Shenyang, 110122, China
- Weifang Hospital of Traditional Chinese Medicine, Weifang, 261000, China
| | - Weiwei Tong
- Department of Laboratory Medicine, Shengjing Hospital of China Medical University, Shenyang, 110069, China
| | - Mingyan Liu
- School of Pharmacy, China Medical University, Shenyang, 110122, China
| | - Mengyu Liu
- School of Pharmacy, China Medical University, Shenyang, 110122, China
| | - Jinyue Liu
- School of Pharmacy, China Medical University, Shenyang, 110122, China
| | - Xin Jin
- School of Pharmacy, China Medical University, Shenyang, 110122, China
| | - Ju Chen
- School of Pharmacy, China Medical University, Shenyang, 110122, China
| | - Huachao Jia
- School of Pharmacy, China Medical University, Shenyang, 110122, China
| | - Menglin Gao
- School of Pharmacy, China Medical University, Shenyang, 110122, China
| | - Minjie Wei
- School of Pharmacy, China Medical University, Shenyang, 110122, China.
- Liaoning Medical Diagnosis and Treatment Center, Shenyang, 110167, China.
| | - Ying Duan
- Liaoning Maternal and Child Health Hospital, Shenyang, 110005, China.
| | - Xin Zhong
- School of Pharmacy, China Medical University, Shenyang, 110122, China.
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4
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Volpiana MW, Nenadic A, Beh CT. Regulation of yeast polarized exocytosis by phosphoinositide lipids. Cell Mol Life Sci 2024; 81:457. [PMID: 39560727 DOI: 10.1007/s00018-024-05483-x] [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: 08/18/2024] [Revised: 10/01/2024] [Accepted: 10/18/2024] [Indexed: 11/20/2024]
Abstract
Phosphoinositides help steer membrane trafficking routes within eukaryotic cells. In polarized exocytosis, which targets vesicular cargo to sites of polarized growth at the plasma membrane (PM), the two phosphoinositides phosphatidylinositol 4-phosphate (PI4P) and its derivative phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) pave the pathway for vesicle transport from the Golgi to the PM. PI4P is a critical regulator of mechanisms that shape late Golgi membranes for vesicle biogenesis and release. Although enriched in vesicle membranes, PI4P is inexplicably removed from post-Golgi vesicles during their transit to the PM, which drives subsequent steps in exocytosis. At the PM, PI(4,5)P2 recruits effectors that establish polarized membrane sites for targeting the vesicular delivery of secretory cargo. The budding yeast Saccharomyces cerevisiae provides an elegant model to unravel the complexities of phosphoinositide regulation during polarized exocytosis. Here, we review how PI4P and PI(4,5)P2 promote yeast vesicle biogenesis, exocyst complex assembly and vesicle docking at polarized cortical sites, and suggest how these steps might impact related mechanisms of human disease.
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Affiliation(s)
- Matthew W Volpiana
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| | - Aleksa Nenadic
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| | - Christopher T Beh
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada.
- Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, BC, Canada.
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5
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Rossi G, Puller GC, Brennwald P. Asymmetric tethering by exocyst in vitro requires a Rab GTPase, an R-SNARE and a Sac1-sensitive phosphoinositide lipid. Mol Biol Cell 2024; 35:br8. [PMID: 38198574 PMCID: PMC10916868 DOI: 10.1091/mbc.e23-08-0311] [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: 08/09/2023] [Revised: 12/22/2023] [Accepted: 01/05/2024] [Indexed: 01/12/2024] Open
Abstract
Tethering factors play a critical role in deciphering the correct combination of vesicle and target membrane, before SNARE complex formation and membrane fusion. The exocyst plays a central role in tethering post-Golgi vesicles to the plasma membrane, although the mechanism by which this occurs is poorly understood. We recently established an assay for measuring exocyst-mediated vesicle tethering in vitro and we have adapted this assay to examine the ability of exocyst to tether vesicles in an asymmetric manner. We demonstrate that exocyst differs from another post-Golgi vesicle tethering protein, Sro7, in that it is fully capable of tethering vesicles with a functional Rab GTPase, Sec4, to vesicles lacking a functional Rab GTPase. Using this assay, we show that exocyst requires both the Rab and R-SNARE, Snc1, to be present on the same membrane surface. Using Sac1 phosphatase treatment, we demonstrate a likely role for phosphoinositides on the opposing Rab-deficient membrane. This suggests a specific model for exocyst orientation and its points of contact between membranes during heterotypic tethering of post-Golgi vesicles with the plasma membrane.
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Affiliation(s)
- Guendalina Rossi
- Department of Cell Biology and Physiology, University of North Carolina School of Medicine, Chapel Hill, NC 27599
| | - Gabrielle C. Puller
- Department of Cell Biology and Physiology, University of North Carolina School of Medicine, Chapel Hill, NC 27599
- Curriculum in Genetics and Molecular Biology, University of North Carolina School of Medicine, Chapel Hill, NC 27599
| | - Patrick Brennwald
- Department of Cell Biology and Physiology, University of North Carolina School of Medicine, Chapel Hill, NC 27599
- Curriculum in Genetics and Molecular Biology, University of North Carolina School of Medicine, Chapel Hill, NC 27599
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6
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Liu DA, Tao K, Wu B, Yu Z, Szczepaniak M, Rames M, Yang C, Svitkina T, Zhu Y, Xu F, Nan X, Guo W. A phosphoinositide switch mediates exocyst recruitment to multivesicular endosomes for exosome secretion. Nat Commun 2023; 14:6883. [PMID: 37898620 PMCID: PMC10613218 DOI: 10.1038/s41467-023-42661-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 10/17/2023] [Indexed: 10/30/2023] Open
Abstract
Exosomes are secreted to the extracellular milieu when multivesicular endosomes (MVEs) dock and fuse with the plasma membrane. However, MVEs are also known to fuse with lysosomes for degradation. How MVEs are directed to the plasma membrane for exosome secretion rather than to lysosomes is unclear. Here we report that a conversion of phosphatidylinositol-3-phosphate (PI(3)P) to phosphatidylinositol-4-phosphate (PI(4)P) catalyzed sequentially by Myotubularin 1 (MTM1) and phosphatidylinositol 4-kinase type IIα (PI4KIIα) on the surface of MVEs mediates the recruitment of the exocyst complex. The exocyst then targets the MVEs to the plasma membrane for exosome secretion. We further demonstrate that disrupting PI(4)P generation or exocyst function blocked exosomal secretion of Programmed death-ligand 1 (PD-L1), a key immune checkpoint protein in tumor cells, and led to its accumulation in lysosomes. Together, our study suggests that the PI(3)P to PI(4)P conversion on MVEs and the recruitment of the exocyst direct the exocytic trafficking of MVEs for exosome secretion.
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Affiliation(s)
- Di-Ao Liu
- Department of Biology, School of Arts & Sciences, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Kai Tao
- Program in Quantitative and Systems Biology, Department of Biomedical Engineering, Oregon Health and Science University, 2730 S. Moody Ave, Portland, OR, 97201, USA
| | - Bin Wu
- Department of Biology, School of Arts & Sciences, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Ziyan Yu
- Department of Biology, School of Arts & Sciences, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Malwina Szczepaniak
- Program in Quantitative and Systems Biology, Department of Biomedical Engineering, Oregon Health and Science University, 2730 S. Moody Ave, Portland, OR, 97201, USA
| | - Matthew Rames
- Cancer Early Detection Advanced Research Center, Knight Cancer Institute, Oregon Health and Science University, 2720 S. Moody Ave., Portland, OR, 97201, USA
| | - Changsong Yang
- Department of Biology, School of Arts & Sciences, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Tatyana Svitkina
- Department of Biology, School of Arts & Sciences, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Yueyao Zhu
- Department of Biology, School of Arts & Sciences, University of Pennsylvania, Philadelphia, PA, 19104, USA
- Department of Pathology & Laboratory Medicine, Children's Hospital of Philadelphia Research Institute, Philadelphia, PA, 19104, USA
| | - Fengyuan Xu
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Xiaolin Nan
- Program in Quantitative and Systems Biology, Department of Biomedical Engineering, Oregon Health and Science University, 2730 S. Moody Ave, Portland, OR, 97201, USA
- Cancer Early Detection Advanced Research Center, Knight Cancer Institute, Oregon Health and Science University, 2720 S. Moody Ave., Portland, OR, 97201, USA
| | - Wei Guo
- Department of Biology, School of Arts & Sciences, University of Pennsylvania, Philadelphia, PA, 19104, USA.
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7
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Heckle LA, Kozminski KG. Osh-dependent and -independent Regulation of PI4P Levels During Polarized Growth of Saccharomyces cerevisiae. Mol Biol Cell 2023; 34:ar104. [PMID: 37556206 PMCID: PMC10559303 DOI: 10.1091/mbc.e23-03-0089] [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: 03/10/2023] [Revised: 07/03/2023] [Accepted: 07/31/2023] [Indexed: 08/11/2023] Open
Abstract
Polarized secretion facilitates polarized cell growth. For a secretory vesicle to dock at the plasma membrane, it must mature with a progressive association or dissociation of molecules that are, respectively, necessary for or inhibitory to vesicle docking, including an exchange of Rab GTPases. In current models, oxysterol-binding protein homologue 4 (Osh4p) establishes a phosphatidylinositol 4-phosphate (PI4P) gradient along the secretory trafficking pathway such that vesicles have higher PI4P levels after budding from the trans-Golgi relative to when vesicles arrive at the plasma membrane. In this study, using the lipid-binding domain P4M and live-cell imaging, we show that secretory vesicle-associated PI4P levels remain constant when vesicles traffic from the trans-Golgi to the plasma membrane. We also show that deletion of OSH4 does not alter vesicle-associated PI4P levels, though loss of any individual member of the OSH family or complete loss of OSH family function alters the intracellular distribution of PI4P. We propose a model in which the Rab GTPases Ypt32p and Sec4p remain associated with a secretory vesicle during trafficking, independent of PI4P levels and Osh4p. Together these data indicate the necessity of experiments revealing the location and timing of events required for vesicle maturation.
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Affiliation(s)
- Lindsay A. Heckle
- Department of Biology, University of Virginia, Charlottesville, VA 22904
| | - Keith G. Kozminski
- Department of Biology, University of Virginia, Charlottesville, VA 22904
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22908
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8
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Li X, Liu D, Griffis E, Novick P. Exploring the consequences of redirecting an exocytic Rab onto endocytic vesicles. Mol Biol Cell 2023; 34:ar38. [PMID: 36857153 PMCID: PMC10162416 DOI: 10.1091/mbc.e23-01-0037] [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: 02/01/2023] [Accepted: 02/22/2023] [Indexed: 03/02/2023] Open
Abstract
Bidirectional vesicular traffic links compartments along the exocytic and endocytic pathways. Rab GTPases have been implicated in specifying the direction of vesicular transport. To explore this possibility, we sought to redirect an exocytic Rab, Sec4, onto endocytic vesicles by fusing the catalytic domain of the Sec4 GEF, Sec2, onto the CUE localization domain of Vps9, a GEF for the endocytic Rab Ypt51. The Sec2GEF-GFP-CUE construct localized to bright puncta predominantly near sites of polarized growth, and this localization was dependent on the ability of the CUE domain to bind to the ubiquitin moieties added to the cytoplasmic tails of proteins destined for endocytic internalization. Sec4 and Sec4 effectors were recruited to these puncta with various efficiencies. Cells expressing Sec2GEF-GFP-CUE grew surprisingly well and secreted protein at near-normal efficiency, implying that Golgi-derived secretory vesicles were delivered to polarized sites of cell growth despite the misdirection of Sec4 and its effectors. A low efficiency mechanism for localization of Sec2 to secretory vesicles that is independent of known cues might be responsible. In total, the results suggest that while Rabs may play a critical role in specifying the direction of vesicular transport, cells are remarkably tolerant of Rab misdirection.
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Affiliation(s)
- Xia Li
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093-0644
| | - Dongmei Liu
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093-0644
| | - Eric Griffis
- Nikon Imaging Center, University of California, San Diego, La Jolla, CA 92093-0694
| | - Peter Novick
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093-0644
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9
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McPhail JA, Burke JE. Molecular mechanisms of PI4K regulation and their involvement in viral replication. Traffic 2023; 24:131-145. [PMID: 35579216 DOI: 10.1111/tra.12841] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 03/07/2022] [Accepted: 03/30/2022] [Indexed: 11/28/2022]
Abstract
Lipid phosphoinositides are master signaling molecules in eukaryotic cells and key markers of organelle identity. Because of these important roles, the kinases and phosphatases that generate phosphoinositides must be tightly regulated. Viruses can manipulate this regulation, with the Type III phosphatidylinositol 4-kinases (PI4KA and PI4KB) being hijacked by many RNA viruses to mediate their intracellular replication through the formation of phosphatidylinositol 4-phosphate (PI4P)-enriched replication organelles (ROs). Different viruses have evolved unique approaches toward activating PI4K enzymes to form ROs, through both direct binding of PI4Ks and modulation of PI4K accessory proteins. This review will focus on PI4KA and PI4KB and discuss their roles in signaling, functions in membrane trafficking and manipulation by viruses. Our focus will be the molecular basis for how PI4KA and PI4KB are activated by both protein-binding partners and post-translational modifications, with an emphasis on understanding the different molecular mechanisms viruses have evolved to usurp PI4Ks. We will also discuss the chemical tools available to study the role of PI4Ks in viral infection.
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Affiliation(s)
- Jacob A McPhail
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - John E Burke
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada.,Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia, Canada
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10
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Li X, Liu D, Griffis E, Novick P. Exploring the consequences of redirecting an exocytic Rab onto endocytic vesicles. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.09.527811. [PMID: 36798320 PMCID: PMC9934678 DOI: 10.1101/2023.02.09.527811] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
Bidirectional vesicular traffic links compartments along the exocytic and endocytic pathways. Rab GTPases have been implicated in specifying the direction of vesicular transport because anterograde vesicles are marked with a different Rab than retrograde vesicles. To explore this proposal, we sought to redirect an exocytic Rab, Sec4, onto endocytic vesicles by fusing the catalytic domain of the Sec4 GEF, Sec2, onto the CUE localization domain of Vps9, a GEF for the endocytic Rab, Ypt51. The Sec2GEF-GFP-CUE construct was found to localize to bright puncta predominantly near sites of polarized growth and this localization was strongly dependent upon the ability of the CUE domain to bind to the ubiquitin moieties added to the cytoplasmic tails of proteins destined for endocytic internalization. Sec4 and Sec4 effectors were recruited to these puncta with varying efficiency. The puncta appeared to consist of clusters of 80 nm vesicles and although the puncta are largely static, FRAP analysis suggests that traffic into and out of these clusters continues. Cells expressing Sec2GEF-GFP-CUE grew surprisingly well and secreted protein at near normal efficiency, implying that Golgi derived secretory vesicles were delivered to polarized sites of cell growth, where they tethered and fused with the plasma membrane despite the misdirection of Sec4 and its effectors. In total, the results suggest that while Rabs play a critical role in regulating vesicular transport, cells are remarkably tolerant of Rab misdirection.
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Affiliation(s)
- Xia Li
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California, United States
| | - Dongmei Liu
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California, United States
| | - Eric Griffis
- Nikon Imaging Center, University of California at San Diego, La Jolla, California, United States
| | - Peter Novick
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California, United States
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11
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Advances in measuring cancer cell metabolism with subcellular resolution. Nat Methods 2022; 19:1048-1063. [PMID: 36008629 DOI: 10.1038/s41592-022-01572-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2021] [Accepted: 07/05/2022] [Indexed: 11/08/2022]
Abstract
Characterizing metabolism in cancer is crucial for understanding tumor biology and for developing potential therapies. Although most metabolic investigations analyze averaged metabolite levels from all cell compartments, subcellular metabolomics can provide more detailed insight into the biochemical processes associated with the disease. Methodological limitations have historically prevented the wider application of subcellular metabolomics in cancer research. Recently, however, ways to distinguish and identify metabolic pathways within organelles have been developed, including state-of-the-art methods to monitor metabolism in situ (such as mass spectrometry-based imaging, Raman spectroscopy and fluorescence microscopy), to isolate key organelles via new approaches and to use tailored isotope-tracing strategies. Herein, we examine the advantages and limitations of these developments and look to the future of this field of research.
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12
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A mechanism for exocyst-mediated tethering via Arf6 and PIP5K1C-driven phosphoinositide conversion. Curr Biol 2022; 32:2821-2833.e6. [PMID: 35609603 PMCID: PMC9382030 DOI: 10.1016/j.cub.2022.04.089] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 03/08/2022] [Accepted: 04/28/2022] [Indexed: 11/22/2022]
Abstract
Polarized trafficking is necessary for the development of eukaryotes and is regulated by a conserved molecular machinery. Late steps of cargo delivery are mediated by the exocyst complex, which integrates lipid and protein components to tether vesicles for plasma membrane fusion. However, the molecular mechanisms of this process are poorly defined. Here, we reconstitute functional octameric human exocyst, demonstrating the basis for holocomplex coalescence and biochemically stable subcomplexes. We determine that each subcomplex independently binds to phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2), which is minimally sufficient for membrane tethering. Through reconstitution and epithelial cell biology experiments, we show that Arf6-mediated recruitment of the lipid kinase PIP5K1C rapidly converts phosphatidylinositol 4-phosphate (PI(4)P) to PI(4,5)P2, driving exocyst recruitment and membrane tethering. These results provide a molecular mechanism of exocyst-mediated tethering and a unique functional requirement for phosphoinositide signaling on late-stage vesicles in the vicinity of the plasma membrane. Complete reconstitution and subunit connectivity of the human exocyst complex Binding to PI(4,5)P2 in trans by each subcomplex enables membrane tethering PI(4)P to PI(4,5)P2 conversion is sufficient for exocyst recruitment and tethering Arf6 controls phosphoinositide conversion by PIP5K1C in cells and in vitro
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13
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Bankaitis VA, Tripathi A, Chen XR, Igumenova TI. New strategies for combating fungal infections: Inhibiting inositol lipid signaling by targeting Sec14 phosphatidylinositol transfer proteins. Adv Biol Regul 2022; 84:100891. [PMID: 35240534 PMCID: PMC9149032 DOI: 10.1016/j.jbior.2022.100891] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 02/22/2022] [Indexed: 12/13/2022]
Abstract
Virulent fungi represent a particularly difficult problem in the infectious disease arena as these organisms are eukaryotes that share many orthologous activities with their human hosts. The fact that these activities are often catalyzed by conserved proteins places additional demands on development of pharmacological strategies for specifically inhibiting target fungal activities without imposing undesirable secondary effects on the host. While deployment of a limited set of anti-mycotics has to date satisfied the clinical needs for treatment of fungal infections, the recent emergence of multi-drug resistant fungal 'superbugs' now poses a serious global health threat with rapidly diminishing options for treatment. This escalating infectious disease problem emphasizes the urgent need for development of new classes of anti-mycotics. In that regard, Sec14 phosphatidylinositol transfer proteins offer interesting possibilities for interfering with fungal phosphoinositide signaling with exquisite specificity and without targeting the highly conserved lipid kinases responsible for phosphoinositide production. Herein, we review the establishment of proof-of-principle that demonstrates the feasibility of such an approach. We also describe the lead compounds of four chemotypes that directly target fungal Sec14 proteins. The rules that pertain to the mechanism(s) of Sec14 inhibition by validated small molecule inhibitors, and the open questions that remain, are discussed - as are the challenges that face development of next generation Sec14-directed inhibitors.
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Affiliation(s)
- Vytas A Bankaitis
- Department of Molecular & Cellular Medicine, Texas A&M University, College Station, TX, 77843-0014, USA; Department of Biochemistry & Biophysics, Texas A&M University, College Station, TX, 77843-0014, USA.
| | - Ashutosh Tripathi
- Department of Molecular & Cellular Medicine, Texas A&M University, College Station, TX, 77843-0014, USA
| | - Xiao-Ru Chen
- Department of Biochemistry & Biophysics, Texas A&M University, College Station, TX, 77843-0014, USA
| | - Tatyana I Igumenova
- Department of Biochemistry & Biophysics, Texas A&M University, College Station, TX, 77843-0014, USA
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14
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Casler JC, Johnson N, Krahn AH, Pantazopoulou A, Day KJ, Glick BS. Clathrin adaptors mediate two sequential pathways of intra-Golgi recycling. J Cell Biol 2022; 221:212747. [PMID: 34739034 PMCID: PMC8576872 DOI: 10.1083/jcb.202103199] [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: 03/29/2021] [Revised: 09/16/2021] [Accepted: 10/26/2021] [Indexed: 01/11/2023] Open
Abstract
The pathways of membrane traffic within the Golgi apparatus are not fully known. This question was addressed using the yeast Saccharomyces cerevisiae, in which the maturation of individual Golgi cisternae can be visualized. We recently proposed that the AP-1 clathrin adaptor mediates intra-Golgi recycling late in the process of cisternal maturation. Here, we demonstrate that AP-1 cooperates with the Ent5 clathrin adaptor to recycle a set of Golgi transmembrane proteins, including some that were previously thought to pass through endosomes. This recycling can be detected by removing AP-1 and Ent5, thereby diverting the AP-1/Ent5-dependent Golgi proteins into an alternative recycling loop that involves traffic to the plasma membrane followed by endocytosis. Unexpectedly, various AP-1/Ent5-dependent Golgi proteins show either intermediate or late kinetics of residence in maturing cisternae. We infer that the AP-1/Ent5 pair mediates two sequential intra-Golgi recycling pathways that define two classes of Golgi proteins. This insight can explain the polarized distribution of transmembrane proteins in the Golgi.
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Affiliation(s)
- Jason C Casler
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL
| | - Natalie Johnson
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL
| | - Adam H Krahn
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL
| | - Areti Pantazopoulou
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL
| | - Kasey J Day
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL
| | - Benjamin S Glick
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL
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15
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Abstract
Phosphoinositides are signalling lipids derived from phosphatidylinositol, a ubiquitous phospholipid in the cytoplasmic leaflet of eukaryotic membranes. Initially discovered for their roles in cell signalling, phosphoinositides are now widely recognized as key integrators of membrane dynamics that broadly impact on all aspects of cell physiology and on disease. The past decade has witnessed a vast expansion of our knowledge of phosphoinositide biology. On the endocytic and exocytic routes, phosphoinositides direct the inward and outward flow of membrane as vesicular traffic is coupled to the conversion of phosphoinositides. Moreover, recent findings on the roles of phosphoinositides in autophagy and the endolysosomal system challenge our view of lysosome biology. The non-vesicular exchange of lipids, ions and metabolites at membrane contact sites in between organelles has also been found to depend on phosphoinositides. Here we review our current understanding of how phosphoinositides shape and direct membrane dynamics to impact on cell physiology, and provide an overview of emerging concepts in phosphoinositide regulation.
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16
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Laquel P, Testet E, Tuphile K, Cullin C, Fouillen L, Bessoule JJ, Doignon F. Phosphoinositides containing stearic acid are required for interaction between Rho GTPases and the exocyst to control the late steps of polarised exocytosis. Traffic 2021; 23:120-136. [PMID: 34908215 DOI: 10.1111/tra.12829] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 11/18/2021] [Accepted: 12/07/2021] [Indexed: 11/27/2022]
Abstract
Cell polarity is achieved by regulators such as small G proteins, exocyst members and phosphoinositides, with the latter playing a key role when bound to the exocyst proteins Sec3p and Exo70p, and Rho GTPases. This ensures asymmetric growth via the routing of proteins and lipids to the cell surface using actin cables. Previously, using a yeast mutant for a lysophosphatidylinositol acyl transferase encoded by the PSI1 gene, we demonstrated the role of stearic acid in the acyl chain of phosphoinositides in cytoskeletal organisation and secretion. Here, we use a genetic approach to characterise the effect on late steps of the secretory pathway. The constitutive overexpression of PSI1 in mutants affecting kinases involved in the phosphoinositide pathway demonstrated the role of molecular species containing stearic acid in bypassing a lack of phosphatidylinositol-4-phosphate PI(4)P at the plasma membrane, which is essential for the function of the Cdc42p module. Decreasing the levels of stearic acid-containing phosphoinositides modifies the environment of the actors involved in the control of late steps in the secretory pathway. This leads to decreased interactions between Exo70p and Sec3p, with Cdc42p, Rho1p and Rho3p, due to disruption of the GTP/GDP ratio of at least Rho1p and Rho3p GTPases, thereby preventing activation of the exocyst.
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Affiliation(s)
- P Laquel
- Univ. Bordeaux, CNRS, Laboratoire de Biogenèse Membranaire, UMR 5200, F-33140 Villenave d'Ornon, France
| | - E Testet
- Univ. Bordeaux, CNRS, Laboratoire de Biogenèse Membranaire, UMR 5200, F-33140 Villenave d'Ornon, France
| | - K Tuphile
- Univ. Bordeaux, CNRS, Laboratoire de Biogenèse Membranaire, UMR 5200, F-33140 Villenave d'Ornon, France
| | - C Cullin
- Univ. Bordeaux, CNRS, Laboratoire de Chimie Biologie des Membranes & des Nano-objets, UMR 5248, Pessac, France
| | - L Fouillen
- Univ. Bordeaux, CNRS, Laboratoire de Biogenèse Membranaire, UMR 5200, F-33140 Villenave d'Ornon, France.,Metabolome Facility of Bordeaux, Functional Genomics Centre, F-33883 Villenave d'Ornon, France
| | - J J Bessoule
- Univ. Bordeaux, CNRS, Laboratoire de Biogenèse Membranaire, UMR 5200, F-33140 Villenave d'Ornon, France
| | - F Doignon
- Univ. Bordeaux, CNRS, Laboratoire de Biogenèse Membranaire, UMR 5200, F-33140 Villenave d'Ornon, France
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17
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Schechter M, Sharon R. An Emerging Role for Phosphoinositides in the Pathophysiology of Parkinson’s Disease. JOURNAL OF PARKINSON'S DISEASE 2021; 11:1725-1750. [PMID: 34151859 PMCID: PMC8609718 DOI: 10.3233/jpd-212684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Recent data support an involvement of defects in homeostasis of phosphoinositides (PIPs) in the pathophysiology of Parkinson’s disease (PD). Genetic mutations have been identified in genes encoding for PIP-regulating and PIP-interacting proteins, that are associated with familial and sporadic PD. Many of these proteins are implicated in vesicular membrane trafficking, mechanisms that were recently highlighted for their close associations with PD. PIPs are phosphorylated forms of the membrane phospholipid, phosphatidylinositol. Their composition in the vesicle’s membrane of origin, as well as membrane of destination, controls vesicular membrane trafficking. We review the converging evidence that points to the involvement of PIPs in PD. The review describes PD- and PIP-associated proteins implicated in clathrin-mediated endocytosis and autophagy, and highlights the involvement of α-synuclein in these mechanisms.
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Affiliation(s)
- Meir Schechter
- Department of Biochemistry and Molecular Biology, IMRIC, The Hebrew University-Hadassah Medical School, Ein Kerem, Jerusalem, Israel
| | - Ronit Sharon
- Department of Biochemistry and Molecular Biology, IMRIC, The Hebrew University-Hadassah Medical School, Ein Kerem, Jerusalem, Israel
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18
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Nakamura TS, Suda Y, Muneshige K, Fujieda Y, Okumura Y, Inoue I, Tanaka T, Takahashi T, Nakanishi H, Gao XD, Okada Y, Neiman AM, Tachikawa H. Suppression of Vps13 adaptor protein mutants reveals a central role for PI4P in regulating prospore membrane extension. PLoS Genet 2021; 17:e1009727. [PMID: 34407079 PMCID: PMC8372973 DOI: 10.1371/journal.pgen.1009727] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 07/20/2021] [Indexed: 01/19/2023] Open
Abstract
Vps13 family proteins are proposed to function in bulk lipid transfer between membranes, but little is known about their regulation. During sporulation of Saccharomyces cerevisiae, Vps13 localizes to the prospore membrane (PSM) via the Spo71–Spo73 adaptor complex. We previously reported that loss of any of these proteins causes PSM extension and subsequent sporulation defects, yet their precise function remains unclear. Here, we performed a genetic screen and identified genes coding for a fragment of phosphatidylinositol (PI) 4-kinase catalytic subunit and PI 4-kinase noncatalytic subunit as multicopy suppressors of spo73Δ. Further genetic and cytological analyses revealed that lowering PI4P levels in the PSM rescues the spo73Δ defects. Furthermore, overexpression of VPS13 and lowering PI4P levels synergistically rescued the defect of a spo71Δ spo73Δ double mutant, suggesting that PI4P might regulate Vps13 function. In addition, we show that an N-terminal fragment of Vps13 has affinity for the endoplasmic reticulum (ER), and ER-plasma membrane (PM) tethers localize along the PSM in a manner dependent on Vps13 and the adaptor complex. These observations suggest that Vps13 and the adaptor complex recruit ER-PM tethers to ER-PSM contact sites. Our analysis revealed that involvement of a phosphoinositide, PI4P, in regulation of Vps13, and also suggest that distinct contact site proteins function cooperatively to promote de novo membrane formation. Vps13 family proteins are conserved lipid transfer proteins that function at organelle contact sites and have been implicated in a number of different neurological diseases. In the yeast Saccharomyces cerevisiae, Vps13 is encoded by a single gene and is localized to various contact sites by interaction with different adaptor proteins and/or lipids, however its regulation is yet to be clarified. We have previously shown that during the developmental process of sporulation, Vps13 is recruited to de novo membrane structures called prospore membranes (PSMs) by a specific adaptor complex, and Vps13 and its adaptors are required for PSM extension. Here we reveal that loss of an adaptor can be overcome by lowering phosphatidylinositol-4-phosphate (PI4P) levels, either by inhibiting PI 4-kinase on the PSM or recruiting PI 4-phospatase to the PSM and that PI4P levels in the PSM affect Vps13 function. Further, we show that Vps13 forms endoplasmic reticulum (ER)-PSM contact sites, that ER-plasma membrane tethering proteins are recruited to ER-PSM contacts, and these proteins may function in conjunction with Vps13. Thus, our work shines light on both the mechanisms of intracellular remodeling and the function of this important class of lipid transfer proteins.
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Affiliation(s)
- Tsuyoshi S. Nakamura
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Kanagawa, Japan
| | - Yasuyuki Suda
- Department of Molecular Cell Biology, Graduate School of Comprehensive Human Sciences and Institute of Basic Medical Sciences, University of Tsukuba, Ibaraki, Japan
- Live Cell Super-Resolution Imaging Research Team, RIKEN Center for Advanced Photonics, Saitama, Japan
| | - Kenji Muneshige
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Yuji Fujieda
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Yuuya Okumura
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Ichiro Inoue
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Takayuki Tanaka
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Tetsuo Takahashi
- Laboratory of Glycobiology and Glycotechnology, Department of Applied Biochemistry, School of Engineering, Tokai University, Kanagawa, Japan
| | - Hideki Nakanishi
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China
| | - Xiao-Dong Gao
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China
| | - Yasushi Okada
- Laboratory for Cell Dynamics Observation, Center for Biosystems Dynamics Research, RIKEN, Osaka, Japan
- Department of Physics and Universal Biology Institute, Graduate School of Science, The University of Tokyo, Tokyo, Japan
- Department of Physics, Universal Biology Institute, and the International Research Center for Neurointelligence (WPI-IRCN), The University of Tokyo, Tokyo, Japan
| | - Aaron M. Neiman
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, United States of America
| | - Hiroyuki Tachikawa
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Tokyo, Japan
- * E-mail:
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19
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Borchers AC, Langemeyer L, Ungermann C. Who's in control? Principles of Rab GTPase activation in endolysosomal membrane trafficking and beyond. J Cell Biol 2021; 220:212549. [PMID: 34383013 PMCID: PMC8366711 DOI: 10.1083/jcb.202105120] [Citation(s) in RCA: 91] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 07/08/2021] [Accepted: 07/08/2021] [Indexed: 12/12/2022] Open
Abstract
The eukaryotic endomembrane system consists of multiple interconnected organelles. Rab GTPases are organelle-specific markers that give identity to these membranes by recruiting transport and trafficking proteins. During transport processes or along organelle maturation, one Rab is replaced by another, a process termed Rab cascade, which requires at its center a Rab-specific guanine nucleotide exchange factor (GEF). The endolysosomal system serves here as a prime example for a Rab cascade. Along with endosomal maturation, the endosomal Rab5 recruits and activates the Rab7-specific GEF Mon1-Ccz1, resulting in Rab7 activation on endosomes and subsequent fusion of endosomes with lysosomes. In this review, we focus on the current idea of Mon1-Ccz1 recruitment and activation in the endolysosomal and autophagic pathway. We compare identified principles to other GTPase cascades on endomembranes, highlight the importance of regulation, and evaluate in this context the strength and relevance of recent developments in in vitro analyses to understand the underlying foundation of organelle biogenesis and maturation.
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Affiliation(s)
- Ann-Christin Borchers
- Department of Biology/Chemistry, Biochemistry Section, Osnabrück University, Osnabrück, Germany
| | - Lars Langemeyer
- Department of Biology/Chemistry, Biochemistry Section, Osnabrück University, Osnabrück, Germany
| | - Christian Ungermann
- Department of Biology/Chemistry, Biochemistry Section, Osnabrück University, Osnabrück, Germany.,Center of Cellular Nanoanalytics Osnabrück (CellNanOs), Osnabrück University, Osnabrück, Germany
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20
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Borgese N, Iacomino N, Colombo SF, Navone F. The Link between VAPB Loss of Function and Amyotrophic Lateral Sclerosis. Cells 2021; 10:1865. [PMID: 34440634 PMCID: PMC8392409 DOI: 10.3390/cells10081865] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 07/16/2021] [Accepted: 07/16/2021] [Indexed: 02/06/2023] Open
Abstract
The VAP proteins are integral adaptor proteins of the endoplasmic reticulum (ER) membrane that recruit a myriad of interacting partners to the ER surface. Through these interactions, the VAPs mediate a large number of processes, notably the generation of membrane contact sites between the ER and essentially all other cellular membranes. In 2004, it was discovered that a mutation (p.P56S) in the VAPB paralogue causes a rare form of dominantly inherited familial amyotrophic lateral sclerosis (ALS8). The mutant protein is aggregation-prone, non-functional and unstable, and its expression from a single allele appears to be insufficient to support toxic gain-of-function effects within motor neurons. Instead, loss-of-function of the single wild-type allele is required for pathological effects, and VAPB haploinsufficiency may be the main driver of the disease. In this article, we review the studies on the effects of VAPB deficit in cellular and animal models. Several basic cell physiological processes are affected by downregulation or complete depletion of VAPB, impinging on phosphoinositide homeostasis, Ca2+ signalling, ion transport, neurite extension, and ER stress. In the future, the distinction between the roles of the two VAP paralogues (A and B), as well as studies on motor neurons generated from induced pluripotent stem cells (iPSC) of ALS8 patients will further elucidate the pathogenic basis of p.P56S familial ALS, as well as of other more common forms of the disease.
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Affiliation(s)
- Nica Borgese
- CNR Institute of Neuroscience, Via Follereau 3, Bldg U28, 20854 Vedano al Lambro, Italy; (N.I.); (S.F.C.)
| | | | | | - Francesca Navone
- CNR Institute of Neuroscience, Via Follereau 3, Bldg U28, 20854 Vedano al Lambro, Italy; (N.I.); (S.F.C.)
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21
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Emerging Prospects for Combating Fungal Infections by Targeting Phosphatidylinositol Transfer Proteins. Int J Mol Sci 2021; 22:ijms22136754. [PMID: 34201733 PMCID: PMC8269425 DOI: 10.3390/ijms22136754] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 06/11/2021] [Accepted: 06/11/2021] [Indexed: 12/27/2022] Open
Abstract
The emergence of fungal “superbugs” resistant to the limited cohort of anti-fungal agents available to clinicians is eroding our ability to effectively treat infections by these virulent pathogens. As the threat of fungal infection is escalating worldwide, this dwindling response capacity is fueling concerns of impending global health emergencies. These developments underscore the urgent need for new classes of anti-fungal drugs and, therefore, the identification of new targets. Phosphoinositide signaling does not immediately appear to offer attractive targets due to its evolutionary conservation across the Eukaryota. However, recent evidence argues otherwise. Herein, we discuss the evidence identifying Sec14-like phosphatidylinositol transfer proteins (PITPs) as unexplored portals through which phosphoinositide signaling in virulent fungi can be chemically disrupted with exquisite selectivity. Recent identification of lead compounds that target fungal Sec14 proteins, derived from several distinct chemical scaffolds, reveals exciting inroads into the rational design of next generation Sec14 inhibitors. Development of appropriately refined next generation Sec14-directed inhibitors promises to expand the chemical weaponry available for deployment in the shifting field of engagement between fungal pathogens and their human hosts.
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22
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Highland CM, Fromme JC. Arf1 directly recruits the Pik1-Frq1 PI4K complex to regulate the final stages of Golgi maturation. Mol Biol Cell 2021; 32:1064-1080. [PMID: 33788598 PMCID: PMC8101487 DOI: 10.1091/mbc.e21-02-0069] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 03/11/2021] [Accepted: 03/12/2021] [Indexed: 12/21/2022] Open
Abstract
Proper Golgi complex function depends on the activity of Arf1, a GTPase whose effectors assemble and transport outgoing vesicles. Phosphatidylinositol 4-phosphate (PI4P) generated at the Golgi by the conserved PI 4-kinase Pik1 (PI4KIIIβ) is also essential for Golgi function, although its precise roles in vesicle formation are less clear. Arf1 has been reported to regulate PI4P production, but whether Pik1 is a direct Arf1 effector is not established. Using a combination of live-cell time-lapse imaging analyses, acute PI4P depletion experiments, and in vitro protein-protein interaction assays on Golgi-mimetic membranes, we present evidence for a model in which Arf1 initiates the final stages of Golgi maturation by tightly controlling PI4P production through direct recruitment of the Pik1-Frq1 PI4-kinase complex. This PI4P serves as a critical signal for AP-1 and secretory vesicle formation, the final events at maturing Golgi compartments. This work therefore establishes the regulatory and temporal context surrounding Golgi PI4P production and its precise roles in Golgi maturation.
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Affiliation(s)
- Carolyn M. Highland
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853
| | - J. Christopher Fromme
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853
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23
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Nitzsche A, Pietilä R, Love DT, Testini C, Ninchoji T, Smith RO, Ekvärn E, Larsson J, Roche FP, Egaña I, Jauhiainen S, Berger P, Claesson‐Welsh L, Hellström M. Paladin is a phosphoinositide phosphatase regulating endosomal VEGFR2 signalling and angiogenesis. EMBO Rep 2021; 22:e50218. [PMID: 33369848 PMCID: PMC7857541 DOI: 10.15252/embr.202050218] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 11/07/2020] [Accepted: 11/18/2020] [Indexed: 12/19/2022] Open
Abstract
Cell signalling governs cellular behaviour and is therefore subject to tight spatiotemporal regulation. Signalling output is modulated by specialized cell membranes and vesicles which contain unique combinations of lipids and proteins. The phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2 ), an important component of the plasma membrane as well as other subcellular membranes, is involved in multiple processes, including signalling. However, which enzymes control the turnover of non-plasma membrane PI(4,5)P2 , and their impact on cell signalling and function at the organismal level are unknown. Here, we identify Paladin as a vascular PI(4,5)P2 phosphatase regulating VEGFR2 endosomal signalling and angiogenesis. Paladin is localized to endosomal and Golgi compartments and interacts with vascular endothelial growth factor receptor 2 (VEGFR2) in vitro and in vivo. Loss of Paladin results in increased internalization of VEGFR2, over-activation of extracellular regulated kinase 1/2, and hypersprouting of endothelial cells in the developing retina of mice. These findings suggest that inhibition of Paladin, or other endosomal PI(4,5)P2 phosphatases, could be exploited to modulate VEGFR2 signalling and angiogenesis, when direct and full inhibition of the receptor is undesirable.
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Affiliation(s)
- Anja Nitzsche
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
- Present address:
Université de ParisParis Cardiovascular Research CenterINSERM U970ParisFrance
| | - Riikka Pietilä
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
| | - Dominic T Love
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
| | - Chiara Testini
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
- Present address:
Division of NephrologyDepartment of MedicineBoston Children’s HospitalBostonMAUSA
| | - Takeshi Ninchoji
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
| | - Ross O Smith
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
| | - Elisabet Ekvärn
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
- Present address:
Cepheid ABSolnaSweden
| | - Jimmy Larsson
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
- Present address:
Department of Cell and Molecular BiologyUppsala UniversityUppsalaSweden
| | - Francis P Roche
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
| | - Isabel Egaña
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
| | - Suvi Jauhiainen
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
| | - Philipp Berger
- Laboratory of Nanoscale BiologyPaul‐Scherrer InstituteVilligenSwitzerland
| | - Lena Claesson‐Welsh
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
| | - Mats Hellström
- Science for Life LaboratoryThe Rudbeck LaboratoryDepartment of Immunology, Genetics and PathologyUppsala UniversityUppsalaSweden
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24
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Koch PA, Dornan GL, Hessenberger M, Haucke V. The molecular mechanisms mediating class II PI 3-kinase function in cell physiology. FEBS J 2021; 288:7025-7042. [PMID: 33387369 DOI: 10.1111/febs.15692] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 12/14/2020] [Accepted: 12/30/2020] [Indexed: 12/13/2022]
Abstract
The phosphoinositide 3-kinase (PI3K) family of lipid-modifying enzymes plays vital roles in cell signaling and membrane trafficking through the production of 3-phosphorylated phosphoinositides. Numerous studies have analyzed the structure and function of class I and class III PI3Ks. In contrast, we know comparably little about the structure and physiological functions of the class II enzymes. Only recent studies have begun to unravel their roles in development, endocytic and endolysosomal membrane dynamics, signal transduction, and cell migration, while the mechanisms that control their localization and enzymatic activity remain largely unknown. Here, we summarize our current knowledge of the class II PI3Ks and outline open questions related to their structure, enzymatic activity, and their physiological and pathophysiological functions.
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Affiliation(s)
- Philipp Alexander Koch
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany.,Faculty of Biology, Chemistry and Pharmacy, Freie Universität Berlin, Germany
| | | | - Manuel Hessenberger
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Volker Haucke
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany.,Faculty of Biology, Chemistry and Pharmacy, Freie Universität Berlin, Germany
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25
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Delfosse V, Bourguet W, Drin G. Structural and Functional Specialization of OSBP-Related Proteins. ACTA ACUST UNITED AC 2020. [DOI: 10.1177/2515256420946627] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Lipids are precisely distributed in the eukaryotic cell where they help to define organelle identity and function, in addition to their structural role. Once synthesized, many lipids must be delivered to other compartments by non-vesicular routes, a process that is undertaken by proteins called Lipid Transfer Proteins (LTPs). OSBP and the closely-related ORP and Osh proteins constitute a major, evolutionarily conserved family of LTPs in eukaryotes. Most of these target one or more subcellular regions, and membrane contact sites in particular, where two organelle membranes are in close proximity. It was initially thought that such proteins were strictly dedicated to sterol sensing or transport. However, over the last decade, numerous studies have revealed that these proteins have many more functions, and we have expanded our understanding of their mechanisms. In particular, many of them are lipid exchangers that exploit PI(4)P or possibly other phosphoinositide gradients to directionally transfer sterol or PS between two compartments. Importantly, these transfer activities are tightly coupled to processes such as lipid metabolism, cellular signalling and vesicular trafficking. This review describes the molecular architecture of OSBP/ORP/Osh proteins, showing how their specific structural features and internal configurations impart unique cellular functions.
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Affiliation(s)
- Vanessa Delfosse
- Centre de Biochimie Structurale, Inserm, CNRS, Univ Montpellier, Montpellier, France
| | - William Bourguet
- Centre de Biochimie Structurale, Inserm, CNRS, Univ Montpellier, Montpellier, France
| | - Guillaume Drin
- CNRS, Institut de Pharmacologie Moléculaire et Cellulaire, Université Côte d’Azur, Valbonne, France
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26
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Stalder D, Gershlick DC. Direct trafficking pathways from the Golgi apparatus to the plasma membrane. Semin Cell Dev Biol 2020; 107:112-125. [PMID: 32317144 PMCID: PMC7152905 DOI: 10.1016/j.semcdb.2020.04.001] [Citation(s) in RCA: 82] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 04/03/2020] [Accepted: 04/06/2020] [Indexed: 12/19/2022]
Abstract
In eukaryotic cells, protein sorting is a highly regulated mechanism important for many physiological events. After synthesis in the endoplasmic reticulum and trafficking to the Golgi apparatus, proteins sort to many different cellular destinations including the endolysosomal system and the extracellular space. Secreted proteins need to be delivered directly to the cell surface. Sorting of secreted proteins from the Golgi apparatus has been a topic of interest for over thirty years, yet there is still no clear understanding of the machinery that forms the post-Golgi carriers. Most evidence points to these post-Golgi carriers being tubular pleomorphic structures that bud from the trans-face of the Golgi. In this review, we present the background studies and highlight the key components of this pathway, we then discuss the machinery implicated in the formation of these carriers, their translocation across the cytosol, and their fusion at the plasma membrane.
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Key Words
- ATP, adenosine triphosphate
- BFA, Brefeldin A
- CARTS, CARriers of the TGN to the cell Surface
- CI-MPR, cation-independent mannose-6 phosphate receptor
- Constitutive Secretion
- CtBP3/BARS, C-terminus binding protein 3/BFA adenosine diphosphate–ribosylated substrate
- ER, endoplasmic reticulum
- GPI-anchored proteins, glycosylphosphatidylinositol-anchored proteins
- GlcCer, glucosylceramidetol
- Golgi to plasma membrane sorting
- PAUF, pancreatic adenocarcinoma up-regulated factor
- PKD, Protein Kinase D
- RUSH, retention using selective hooks
- SBP, streptavidin-binding peptide
- SM, sphingomyelin
- SNARE, soluble N-ethylmaleimide sensitive fusion protein attachment protein receptor
- SPCA1, secretory pathway calcium ATPase 1
- Secretion
- TGN, trans-Golgi Network
- TIRF, total internal reflection fluorescence
- VSV, vesicular stomatitis virus
- pleomorphic tubular carriers
- post-Golgi carriers
- ts, temperature sensitive
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Affiliation(s)
- Danièle Stalder
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
| | - David C Gershlick
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
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27
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Nguyen PM, Gandasi NR, Xie B, Sugahara S, Xu Y, Idevall-Hagren O. The PI(4)P phosphatase Sac2 controls insulin granule docking and release. J Cell Biol 2019; 218:3714-3729. [PMID: 31533953 PMCID: PMC6829663 DOI: 10.1083/jcb.201903121] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 06/20/2019] [Accepted: 08/08/2019] [Indexed: 12/12/2022] Open
Abstract
Insulin granule biogenesis involves transport to, and stable docking at, the plasma membrane before priming and fusion. Defects in this pathway result in impaired insulin secretion and are a hallmark of type 2 diabetes. We now show that the phosphatidylinositol 4-phosphate phosphatase Sac2 localizes to insulin granules in a substrate-dependent manner and that loss of Sac2 results in impaired insulin secretion. Sac2 operates upstream of granule docking, since loss of Sac2 prevented granule tethering to the plasma membrane and resulted in both reduced granule density and number of exocytic events. Sac2 levels correlated positively with the number of docked granules and exocytic events in clonal β cells and with insulin secretion in human pancreatic islets, and Sac2 expression was reduced in islets from type 2 diabetic subjects. Taken together, we identified a phosphoinositide switch on the surface on insulin granules that is required for stable granule docking at the plasma membrane and impaired in human type 2 diabetes.
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Affiliation(s)
- Phuoc My Nguyen
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Nikhil R Gandasi
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Beichen Xie
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Sari Sugahara
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden.,Laboratory of Health Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan
| | - Yingke Xu
- Department of Biomedical Engineering, Key Laboratory of Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, Zhejiang University, Hangzhou, China
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28
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Wang Y, Mousley CJ, Lete MG, Bankaitis VA. An equal opportunity collaboration between lipid metabolism and proteins in the control of membrane trafficking in the trans-Golgi and endosomal systems. Curr Opin Cell Biol 2019; 59:58-72. [PMID: 31039522 DOI: 10.1016/j.ceb.2019.03.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 03/25/2019] [Accepted: 03/27/2019] [Indexed: 12/18/2022]
Abstract
Recent years have witnessed the evolution of the cell biology of lipids into an extremely active area of investigation. Deciphering the involvement of lipid metabolism and lipid signaling in membrane trafficking pathways defines a major nexus of contemporary experimental activity on this front. Significant effort in that direction is invested in understanding the trans-Golgi network/endosomal system where unambiguous connections between membrane trafficking and inositol lipid and phosphatidylcholine metabolism were first discovered. However, powered by new advances in contemporary cell biology, the march of science is rapidly expanding that window of inquiry to include ever more diverse arms of the lipid metabolome, and to include other compartments of the secretory pathway as well.
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Affiliation(s)
- Yaxi Wang
- Department of Biochemistry & Biophysics, Texas A&M University, College Station, TX 77843-2128, USA
| | - Carl J Mousley
- School of Biomedical Sciences, Curtin Health Innovation Research Institute (CHIRI), Faculty of Health Sciences, Curtin University, Bentley, WA 6102, Australia
| | - Marta G Lete
- Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, TX 77843-1114, USA
| | - Vytas A Bankaitis
- Department of Biochemistry & Biophysics, Texas A&M University, College Station, TX 77843-2128, USA; Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, TX 77843-1114, USA.
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29
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Genevini P, Colombo MN, Venditti R, Marcuzzo S, Colombo SF, Bernasconi P, De Matteis MA, Borgese N, Navone F. VAPB depletion alters neuritogenesis and phosphoinositide balance in motoneuron-like cells: relevance to VAPB-linked amyotrophic lateral sclerosis. J Cell Sci 2019; 132:jcs.220061. [PMID: 30745341 DOI: 10.1242/jcs.220061] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 02/01/2019] [Indexed: 12/12/2022] Open
Abstract
VAPB and VAPA are ubiquitously expressed endoplasmic reticulum membrane proteins that play key roles in lipid exchange at membrane contact sites. A mutant, aggregation-prone, form of VAPB (P56S) is linked to a dominantly inherited form of amyotrophic lateral sclerosis; however, it has been unclear whether its pathogenicity is due to toxic gain of function, to negative dominance, or simply to insufficient levels of the wild-type protein produced from a single allele (haploinsufficiency). To investigate whether reduced levels of functional VAPB, independently from the presence of the mutant form, affect the physiology of mammalian motoneuron-like cells, we generated NSC34 clones, from which VAPB was partially or nearly completely depleted. VAPA levels, determined to be over fourfold higher than those of VAPB in untransfected cells, were unaffected. Nonetheless, cells with even partially depleted VAPB showed an increase in Golgi- and acidic vesicle-localized phosphatidylinositol-4-phosphate (PI4P) and reduced neurite extension when induced to differentiate. Conversely, the PI4 kinase inhibitors PIK93 and IN-10 increased neurite elongation. Thus, for long-term survival, motoneurons might require the full dose of functional VAPB, which may have unique function(s) that VAPA cannot perform.
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Affiliation(s)
- Paola Genevini
- Consiglio Nazionale delle Ricerche Neuroscience Institute and BIOMETRA Department, Università degli Studi di Milano, Milan 20129, Italy
| | - Maria Nicol Colombo
- Consiglio Nazionale delle Ricerche Neuroscience Institute and BIOMETRA Department, Università degli Studi di Milano, Milan 20129, Italy
| | | | - Stefania Marcuzzo
- Neurology IV - Neuroimmunology and Neuromuscular Diseases Unit, Fondazione Istituto Neurologico 'Carlo Besta', Milan 20133, Italy
| | - Sara Francesca Colombo
- Consiglio Nazionale delle Ricerche Neuroscience Institute and BIOMETRA Department, Università degli Studi di Milano, Milan 20129, Italy
| | - Pia Bernasconi
- Neurology IV - Neuroimmunology and Neuromuscular Diseases Unit, Fondazione Istituto Neurologico 'Carlo Besta', Milan 20133, Italy
| | - Maria Antonietta De Matteis
- Telethon Institute of Genetics and Medicine, Pozzuoli 80078, Italy.,Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Naples 80133, Italy
| | - Nica Borgese
- Consiglio Nazionale delle Ricerche Neuroscience Institute and BIOMETRA Department, Università degli Studi di Milano, Milan 20129, Italy
| | - Francesca Navone
- Consiglio Nazionale delle Ricerche Neuroscience Institute and BIOMETRA Department, Università degli Studi di Milano, Milan 20129, Italy
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30
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Qiu S, Zeng B. Advances in understanding of the oxysterol-binding protein homologous in yeast and filamentous fungi. Int Microbiol 2019; 22:169-179. [PMID: 30810998 DOI: 10.1007/s10123-019-00056-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 01/02/2019] [Accepted: 01/03/2019] [Indexed: 01/14/2023]
Abstract
Oxysterol-binding protein is an important non-vesicular trafficking protein involved in the transportation of lipids in eukaryotic cells. Oxysterol-binding protein is identified as oxysterol-binding protein-related proteins (ORPs) in mammals and oxysterol-binding protein homologue (Osh) in yeast. Research has described the function and structure of oxysterol-binding protein in mammals and yeast, but little information about the protein's structure and function in filamentous fungi has been reported. This article focuses on recent advances in the research of Osh proteins in yeast and filamentous fungi, such as Aspergillus oryzae, Aspergillus nidulans, and Candida albicans. Furthermore, we point out some problems in the field, summarizing the membrane contact sites (MCS) of Osh proteins in yeast, and consider the future of Osh protein development.
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Affiliation(s)
- Shangkun Qiu
- Jiangxi Province Key Laboratory Bioprocess Engineering, Jiangxi Science and Technology Normal University, Nanchang, 330013, China
| | - Bin Zeng
- Jiangxi Province Key Laboratory Bioprocess Engineering, Jiangxi Science and Technology Normal University, Nanchang, 330013, China.
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31
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Maerz LD, Burkhalter MD, Schilpp C, Wittekindt OH, Frick M, Philipp M. Pharmacological cholesterol depletion disturbs ciliogenesis and ciliary function in developing zebrafish. Commun Biol 2019; 2:31. [PMID: 30729178 PMCID: PMC6351647 DOI: 10.1038/s42003-018-0272-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Accepted: 12/20/2018] [Indexed: 12/30/2022] Open
Abstract
Patients with an inherited inability to synthesize sufficient amounts of cholesterol develop congenital malformations of the skull, toes, kidney and heart. As development of these structures depends on functional cilia we investigated whether cholesterol regulates ciliogenesis through inhibition of hydroxymethylglutaryl-Coenzyme A reductase (HMG-CoA-R), the rate-limiting enzyme in cholesterol synthesis. HMG-CoA-R is efficiently inhibited by statins, a standard medication for hyperlipidemia. When zebrafish embryos are treated with statins cilia dysfunction phenotypes including heart defects, left-right asymmetry defects and malformation of ciliated organs develop, which are ameliorated by cholesterol replenishment. HMG-CoA-R inhibition and other means of cholesterol reduction lowered ciliation frequency and cilia length in zebrafish as well as several mammalian cell types. Cholesterol depletion further triggers an inability for ciliary signalling. Because of a reduction of the transition zone component Pi(4,5)P2 we propose that cholesterol governs crucial steps of cilium extension. Taken together, we report that cholesterol abrogation provokes cilia defects.
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Affiliation(s)
- Lars D. Maerz
- Institute of Biochemistry and Molecular Biology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Martin D. Burkhalter
- Institute of Biochemistry and Molecular Biology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Carolin Schilpp
- Institute of General Physiology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Oliver H. Wittekindt
- Institute of General Physiology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Manfred Frick
- Institute of General Physiology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Melanie Philipp
- Institute of Biochemistry and Molecular Biology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
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32
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Grabon A, Bankaitis VA, McDermott MI. The interface between phosphatidylinositol transfer protein function and phosphoinositide signaling in higher eukaryotes. J Lipid Res 2018; 60:242-268. [PMID: 30504233 DOI: 10.1194/jlr.r089730] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Revised: 11/12/2018] [Indexed: 12/22/2022] Open
Abstract
Phosphoinositides are key regulators of a large number of diverse cellular processes that include membrane trafficking, plasma membrane receptor signaling, cell proliferation, and transcription. How a small number of chemically distinct phosphoinositide signals are functionally amplified to exert specific control over such a diverse set of biological outcomes remains incompletely understood. To this end, a novel mechanism is now taking shape, and it involves phosphatidylinositol (PtdIns) transfer proteins (PITPs). The concept that PITPs exert instructive regulation of PtdIns 4-OH kinase activities and thereby channel phosphoinositide production to specific biological outcomes, identifies PITPs as central factors in the diversification of phosphoinositide signaling. There are two evolutionarily distinct families of PITPs: the Sec14-like and the StAR-related lipid transfer domain (START)-like families. Of these two families, the START-like PITPs are the least understood. Herein, we review recent insights into the biochemical, cellular, and physiological function of both PITP families with greater emphasis on the START-like PITPs, and we discuss the underlying mechanisms through which these proteins regulate phosphoinositide signaling and how these actions translate to human health and disease.
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Affiliation(s)
- Aby Grabon
- E. L. Wehner-Welch Laboratory, Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, TX 77843-1114
| | - Vytas A Bankaitis
- E. L. Wehner-Welch Laboratory, Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, TX 77843-1114
| | - Mark I McDermott
- E. L. Wehner-Welch Laboratory, Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, TX 77843-1114
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33
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Tied up: Does altering phosphoinositide-mediated membrane trafficking influence neurodegenerative disease phenotypes? J Genet 2018. [DOI: 10.1007/s12041-018-0961-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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34
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Nadiminti SSP, Kamak M, Koushika SP. Tied up: Does altering phosphoinositide-mediated membrane trafficking influence neurodegenerative disease phenotypes? J Genet 2018; 97:753-771. [PMID: 30027907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Phosphoinositides are a class of membrane lipids that are found on several intracellular compartments and play diverse roles inside cells, such as vesicle formation, protein trafficking, endocytosis etc. Intracellular distribution and levels of phosphoinositides are regulated by enzymes that generate and breakdown these lipids as well as other proteins that associate with phosphoinositides. These events lead to differing levels of specific phosphoinositides on different intracellular compartments. At these intracellular locations, phosphoinositides and their associated proteins, such as Rab GTPases, dynamin and BAR domain-containing proteins, regulate a variety of membrane trafficking pathways. Neurodegenerative phenotypes in disorders such as Parkinson's disease (PD) can arise as a consequence of altered or hampered intracellular trafficking. Altered trafficking can cause proteins such as α-synuclein to aggregate intracellularly. Several trafficking pathways are regulated bymaster regulators such as LRRK2,which is known to regulate the activity of phosphoinositide effector proteins. Perturbing either the levels of phosphoinositides or their interactions with different proteins disrupts intracellular trafficking pathways, contributing to phenotypes often observed in disorders such as Alzheimer's or PDs. Thus, studying phosphoinositide regulation and its role in trafficking can give us a deeper understanding of the contribution of disrupted trafficking to neurodegenerative phenotypes.
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Affiliation(s)
- Sravanthi S P Nadiminti
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai 400 005, India.
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35
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Del Bel LM, Griffiths N, Wilk R, Wei HC, Blagoveshchenskaya A, Burgess J, Polevoy G, Price JV, Mayinger P, Brill JA. The phosphoinositide phosphatase Sac1 regulates cell shape and microtubule stability in the developing Drosophila eye. Development 2018; 145:dev151571. [PMID: 29752385 PMCID: PMC6031321 DOI: 10.1242/dev.151571] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 04/30/2018] [Indexed: 12/15/2022]
Abstract
Epithelial patterning in the developing Drosophila melanogaster eye requires the Neph1 homolog Roughest (Rst), an immunoglobulin family cell surface adhesion molecule expressed in interommatidial cells (IOCs). Here, using a novel temperature-sensitive (ts) allele, we show that the phosphoinositide phosphatase Sac1 is also required for IOC patterning. Sac1ts mutants have rough eyes and retinal patterning defects that resemble rst mutants. Sac1ts retinas exhibit elevated levels of phosphatidylinositol 4-phosphate (PI4P), consistent with the role of Sac1 as a PI4P phosphatase. Indeed, genetic rescue and interaction experiments reveal that restriction of PI4P levels by Sac1 is crucial for normal eye development. Rst is delivered to the cell surface in Sac1ts mutants. However, Sac1ts mutant IOCs exhibit severe defects in microtubule organization, associated with accumulation of Rst and the exocyst subunit Sec8 in enlarged intracellular vesicles upon cold fixation ex vivo Together, our data reveal a novel requirement for Sac1 in promoting microtubule stability and suggest that Rst trafficking occurs in a microtubule- and exocyst-dependent manner.
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Affiliation(s)
- Lauren M Del Bel
- Cell Biology Program, The Hospital for Sick Children, PGCRL Building, 686 Bay Street, Toronto, Ontario, M5G 0A4, Canada
- Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Nigel Griffiths
- Cell Biology Program, The Hospital for Sick Children, PGCRL Building, 686 Bay Street, Toronto, Ontario, M5G 0A4, Canada
- Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Ronit Wilk
- Cell Biology Program, The Hospital for Sick Children, PGCRL Building, 686 Bay Street, Toronto, Ontario, M5G 0A4, Canada
| | - Ho-Chun Wei
- Cell Biology Program, The Hospital for Sick Children, PGCRL Building, 686 Bay Street, Toronto, Ontario, M5G 0A4, Canada
- Department of Molecular Biology and Biochemistry, Simon Fraser University, South Sciences Building Room 8166, 8888 University Drive, Burnaby, British Columbia, V5A 1S6, Canada
| | - Anastasia Blagoveshchenskaya
- Division of Nephrology & Hypertension, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Rd., Portland, Oregon 97239-3098, USA
| | - Jason Burgess
- Cell Biology Program, The Hospital for Sick Children, PGCRL Building, 686 Bay Street, Toronto, Ontario, M5G 0A4, Canada
- Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Gordon Polevoy
- Cell Biology Program, The Hospital for Sick Children, PGCRL Building, 686 Bay Street, Toronto, Ontario, M5G 0A4, Canada
| | - James V Price
- Department of Molecular Biology and Biochemistry, Simon Fraser University, South Sciences Building Room 8166, 8888 University Drive, Burnaby, British Columbia, V5A 1S6, Canada
| | - Peter Mayinger
- Division of Nephrology & Hypertension, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Rd., Portland, Oregon 97239-3098, USA
| | - Julie A Brill
- Cell Biology Program, The Hospital for Sick Children, PGCRL Building, 686 Bay Street, Toronto, Ontario, M5G 0A4, Canada
- Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, M5S 1A8, Canada
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36
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Nanoscale domain formation of phosphatidylinositol 4-phosphate in the plasma and vacuolar membranes of living yeast cells. Eur J Cell Biol 2018; 97:269-278. [PMID: 29609807 DOI: 10.1016/j.ejcb.2018.03.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 02/27/2018] [Accepted: 03/20/2018] [Indexed: 12/31/2022] Open
Abstract
In budding yeast Saccharomyces cerevisiae, PtdIns(4)P serves as an essential signalling molecule in the Golgi complex, endosomal system, and plasma membrane, where it is involved in the control of multiple cellular functions via direct interactions with PtdIns(4)P-binding proteins. To analyse the distribution of PtdIns(4)P in yeast cells at a nanoscale level, we employed an electron microscopy technique that specifically labels PtdIns(4)P on the freeze-fracture replica of the yeast membrane. This method minimizes the possibility of artificial perturbation, because molecules in the membrane are physically immobilised in situ. We observed that PtdIns(4)P is localised on the cytoplasmic leaflet, but not the exoplasmic leaflet, of the plasma membrane, Golgi body, vacuole, and vesicular structure membranes. PtdIns(4)P labelling was not observed in the membrane of the endoplasmic reticulum, and in the outer and inner membranes of the nuclear envelope or mitochondria. PtdIns(4)P forms clusters of <100 nm in diameter in the plasma membrane and vacuolar membrane according to point pattern analysis of immunogold labelling. There are three kinds of compartments in the cytoplasmic leaflet of the plasma membrane. In the present study, we showed that PtdIns(4)P is specifically localised in the flat undifferentiated plasma membrane compartment. In the vacuolar membrane, PtdIns(4)P was concentrated in intramembrane particle (IMP)-deficient raft-like domains, which are tightly bound to lipid droplets, but not surrounding IMP-rich non-raft domains in geometrical IMP-distributed patterns in the stationary phase. This is the first report showing microdomain formations of PtdIns(4)P in the plasma membrane and vacuolar membrane of budding yeast cells at a nanoscale level, which will illuminate the functionality of PtdIns(4)P in each membrane.
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37
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Del Bel LM, Brill JA. Sac1, a lipid phosphatase at the interface of vesicular and nonvesicular transport. Traffic 2018; 19:301-318. [PMID: 29411923 DOI: 10.1111/tra.12554] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 02/02/2018] [Accepted: 02/02/2018] [Indexed: 12/14/2022]
Abstract
The lipid phosphatase Sac1 dephosphorylates phosphatidylinositol 4-phosphate (PI4P), thereby holding levels of this crucial membrane signaling molecule in check. Sac1 regulates multiple cellular processes, including cytoskeletal organization, membrane trafficking and cell signaling. Here, we review the structure and regulation of Sac1, its roles in cell signaling and development and its links to health and disease. Remarkably, many of the diverse roles attributed to Sac1 can be explained by the recent discovery of its requirement at membrane contact sites, where its consumption of PI4P is proposed to drive interorganelle transfer of other cellular lipids, thereby promoting normal lipid homeostasis within cells.
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Affiliation(s)
- Lauren M Del Bel
- Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Julie A Brill
- Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
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38
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Suda Y, Tachikawa H, Inoue I, Kurita T, Saito C, Kurokawa K, Nakano A, Irie K. Activation of Rab GTPase Sec4 by its GEF Sec2 is required for prospore membrane formation during sporulation in yeast Saccharomyces cerevisiae. FEMS Yeast Res 2017; 18:4780275. [DOI: 10.1093/femsyr/fox095] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 12/24/2017] [Indexed: 12/20/2022] Open
Affiliation(s)
- Yasuyuki Suda
- Faculty of medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan
- Live Cell Super-Resolution Imaging Research Team, RIKEN Center for Advanced Photonics, Wako, Saitama 351-0198, Japan
| | - Hiroyuki Tachikawa
- Laboratory of Biochemistry, Graduate School of Agriculture and Life Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Ichiro Inoue
- Laboratory of Biochemistry, Graduate School of Agriculture and Life Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Tomokazu Kurita
- Live Cell Super-Resolution Imaging Research Team, RIKEN Center for Advanced Photonics, Wako, Saitama 351-0198, Japan
| | - Chieko Saito
- Live Cell Super-Resolution Imaging Research Team, RIKEN Center for Advanced Photonics, Wako, Saitama 351-0198, Japan
| | - Kazuo Kurokawa
- Live Cell Super-Resolution Imaging Research Team, RIKEN Center for Advanced Photonics, Wako, Saitama 351-0198, Japan
| | - Akihiko Nakano
- Live Cell Super-Resolution Imaging Research Team, RIKEN Center for Advanced Photonics, Wako, Saitama 351-0198, Japan
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Kenji Irie
- Faculty of medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan
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39
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Abstract
Polarized exocytosis is generally considered as the multistep vesicular trafficking process in which membrane-bounded carriers are transported from the Golgi or endosomal compartments to specific sites of the plasma membrane. Polarized exocytosis in cells is achieved through the coordinated actions of membrane trafficking machinery and cytoskeleton orchestrated by signaling molecules such as the Rho family of small GTPases. Elucidating the molecular mechanisms of polarized exocytosis is essential to our understanding of a wide range of pathophysiological processes from neuronal development to tumor invasion.
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Affiliation(s)
- Jingwen Zeng
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018
| | - Shanshan Feng
- Key Laboratory for Regenerative Medicine of Ministry of Education and Department of Developmental & Regenerative Biology, Jinan University, Guangzhou 510632, P.R. China
| | - Bin Wu
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018
| | - Wei Guo
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018
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40
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Langemeyer L, Perz A, Kümmel D, Ungermann C. A guanine nucleotide exchange factor (GEF) limits Rab GTPase-driven membrane fusion. J Biol Chem 2017; 293:731-739. [PMID: 29184002 DOI: 10.1074/jbc.m117.812941] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 11/14/2017] [Indexed: 11/06/2022] Open
Abstract
The identity of organelles in the endomembrane system of any eukaryotic cell critically depends on the correctly localized Rab GTPase, which binds effectors and thus promotes membrane remodeling or fusion. However, it is still unresolved which factors are required and therefore define the localization of the correct fusion machinery. Using SNARE-decorated proteoliposomes that cannot fuse on their own, we now demonstrate that full fusion activity can be achieved by just four soluble factors: a soluble SNARE (Vam7), a guanine nucleotide exchange factor (GEF, Mon1-Ccz1), a Rab-GDP dissociation inhibitor (GDI) complex (prenylated Ypt7-GDI), and a Rab effector complex (HOPS). Our findings reveal that the GEF Mon1-Ccz1 is necessary and sufficient for stabilizing prenylated Ypt7 on membranes. HOPS binding to Ypt7-GTP then drives SNARE-mediated fusion, which is fully GTP-dependent. We conclude that an entire fusion cascade can be controlled by a GEF.
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Affiliation(s)
| | | | - Daniel Kümmel
- Structural Biochemistry, Department of Biology/Chemistry, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück, Germany
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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: 57] [Impact Index Per Article: 7.1] [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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42
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Smindak RJ, Heckle LA, Chittari SS, Hand MA, Hyatt DM, Mantus GE, Sanfelippo WA, Kozminski KG. Lipid-dependent regulation of exocytosis in S. cerevisiae by OSBP homolog (Osh) 4. J Cell Sci 2017; 130:3891-3906. [PMID: 28993464 DOI: 10.1242/jcs.205435] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 10/04/2017] [Indexed: 11/20/2022] Open
Abstract
Polarized exocytosis is an essential process in many organisms and cell types for correct cell division or functional specialization. Previous studies established that homologs of the oxysterol-binding protein (OSBP) in S. cerevisiae, which comprise the Osh protein family, are necessary for efficient polarized exocytosis by supporting a late post-Golgi step. We define this step as the docking of a specific sub-population of exocytic vesicles with the plasma membrane. In the absence of other Osh proteins, yeast Osh4p can support this process in a manner dependent upon two lipid ligands, PI4P and sterol. Osh6p, which binds PI4P and phosphatidylserine, is also sufficient to support polarized exocytosis, again in a lipid-dependent manner. These data suggest that Osh-mediated exocytosis depends upon lipid binding and exchange without a strict requirement for sterol. We propose a two-step mechanism for Osh protein-mediated regulation of polarized exocytosis by using Osh4p as a model. We describe a specific in vivo role for lipid binding by an OSBP-related protein (ORP) in the process of polarized exocytosis, guiding our understanding of where and how OSBP and ORPs may function in more complex organisms.
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Affiliation(s)
- Richard J Smindak
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Lindsay A Heckle
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Supraja S Chittari
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Marissa A Hand
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Dylan M Hyatt
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Grace E Mantus
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | | | - Keith G Kozminski
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA .,Department of Cell Biology, University of Virginia, Charlottesville, VA 22908, USA
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43
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Choy CH, Han BK, Botelho RJ. Phosphoinositide Diversity, Distribution, and Effector Function: Stepping Out of the Box. Bioessays 2017; 39. [PMID: 28977683 DOI: 10.1002/bies.201700121] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 08/31/2017] [Indexed: 12/26/2022]
Abstract
Phosphoinositides (PtdInsPs) modulate a plethora of functions including signal transduction and membrane trafficking. PtdInsPs are thought to consist of seven interconvertible species that localize to a specific organelle, to which they recruit a set of cognate effector proteins. Here, in reviewing the literature, we argue that this model needs revision. First, PtdInsPs can carry a variety of acyl chains, greatly boosting their molecular diversity. Second, PtdInsPs are more promiscuous in their localization than is usually acknowledged. Third, PtdInsP interconversion is likely achieved through kinase-phosphatase enzyme complexes that coordinate their activities and channel substrates without affecting bulk substrate population. Additionally, we contend that despite hundreds of PtdInsP effectors, our attention is biased toward few proteins. Lastly, we recognize that PtdInsPs can act to nucleate coincidence detection at the effector level, as in PDK1 and Akt. Overall, better integrated models of PtdInsP regulation and function are not only possible but needed.
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Affiliation(s)
- Christopher H Choy
- Graduate Program in Molecular Science, Ryerson University, Toronto, ON, Canada M5B2K3.,Department of Chemistry and Biology, Ryerson University, Toronto, ON, Canada M5B2K3
| | - Bong-Kwan Han
- The Intelligent Synthetic Biology Center, Korea Advanced Institute of Science and Technology, Daejeon 34141, South Korea
| | - Roberto J Botelho
- Graduate Program in Molecular Science, Ryerson University, Toronto, ON, Canada M5B2K3.,Department of Chemistry and Biology, Ryerson University, Toronto, ON, Canada M5B2K3
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44
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Rewiring a Rab regulatory network reveals a possible inhibitory role for the vesicle tether, Uso1. Proc Natl Acad Sci U S A 2017; 114:E8637-E8645. [PMID: 28973856 DOI: 10.1073/pnas.1708394114] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ypt1 and Sec4 are essential Rab GTPases that control the early and late stages of the yeast secretory pathway, respectively. A chimera consisting of Ypt1 with the switch I domain of Sec4, Ypt1-SW1Sec4, is efficiently activated in vitro by the Sec4 exchange factor, Sec2. This should lead to its ectopic activation in vivo and thereby disrupt membrane traffic. Nonetheless early studies found that yeast expressing Ypt1-SW1Sec4 as the sole copy of YPT1 exhibit no growth defect. To resolve this conundrum, we have analyzed yeast expressing various levels of Ypt1-SW1Sec4 We show that even normal expression of Ypt1-SW1Sec4 leads to kinetic transport defects at a late stage of the pathway, with secretory vesicles accumulating near exocytic sites. Higher levels are toxic. Toxicity is suppressed by truncation of Uso1, a vesicle tether required for endoplasmic reticulum-Golgi traffic. The globular head of Uso1 binds to Ypt1 and its coiled-coil tail binds to the Golgi-associated SNARE, Sed5. We propose that when Uso1 is inappropriately recruited to secretory vesicles by Ypt1-SW1Sec4, the extended coiled-coil tail blocks docking to the plasma membrane. This putative inhibitory function could serve to increase the fidelity of vesicle docking.
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45
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De Craene JO, Bertazzi DL, Bär S, Friant S. Phosphoinositides, Major Actors in Membrane Trafficking and Lipid Signaling Pathways. Int J Mol Sci 2017; 18:ijms18030634. [PMID: 28294977 PMCID: PMC5372647 DOI: 10.3390/ijms18030634] [Citation(s) in RCA: 145] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Revised: 03/02/2017] [Accepted: 03/06/2017] [Indexed: 11/30/2022] Open
Abstract
Phosphoinositides are lipids involved in the vesicular transport of proteins and lipids between the different compartments of eukaryotic cells. They act by recruiting and/or activating effector proteins and thus are involved in regulating various cellular functions, such as vesicular budding, membrane fusion and cytoskeleton dynamics. Although detected in small concentrations in membranes, their role is essential to cell function, since imbalance in their concentrations is a hallmark of many cancers. Their synthesis involves phosphorylating/dephosphorylating positions D3, D4 and/or D5 of their inositol ring by specific lipid kinases and phosphatases. This process is tightly regulated and specific to the different intracellular membranes. Most enzymes involved in phosphoinositide synthesis are conserved between yeast and human, and their loss of function leads to severe diseases (cancer, myopathy, neuropathy and ciliopathy).
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Affiliation(s)
- Johan-Owen De Craene
- Department of Molecular and Cellular Genetics, Université de Strasbourg, CNRS, GMGM UMR 7156, F-67000 Strasbourg, France.
| | - Dimitri L Bertazzi
- Department of Molecular and Cellular Genetics, Université de Strasbourg, CNRS, GMGM UMR 7156, F-67000 Strasbourg, France.
| | - Séverine Bär
- Department of Molecular and Cellular Genetics, Université de Strasbourg, CNRS, GMGM UMR 7156, F-67000 Strasbourg, France.
| | - Sylvie Friant
- Department of Molecular and Cellular Genetics, Université de Strasbourg, CNRS, GMGM UMR 7156, F-67000 Strasbourg, France.
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Thomas LL, Fromme JC. GTPase cross talk regulates TRAPPII activation of Rab11 homologues during vesicle biogenesis. J Cell Biol 2016; 215:499-513. [PMID: 27872253 PMCID: PMC5119942 DOI: 10.1083/jcb.201608123] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 10/07/2016] [Accepted: 10/14/2016] [Indexed: 11/22/2022] Open
Abstract
Rab GTPases control vesicle formation and transport, but which proteins are important for their regulation is incompletely understood. Thomas and Fromme provide definitive evidence that TRAPPII is a GEF for the yeast Rab11 homologues Ypt31/32 and implicate the GTPase Arf1 in TRAPPII recruitment, suggesting that a bidirectional cross talk mechanism drives vesicle biogenesis. Rab guanosine triphosphatases (GTPases) control cellular trafficking pathways by regulating vesicle formation, transport, and tethering. Rab11 and its paralogs regulate multiple secretory and endocytic recycling pathways, yet the guanine nucleotide exchange factor (GEF) that activates Rab11 in most eukaryotic cells is unresolved. The large multisubunit transport protein particle (TRAPP) II complex has been proposed to act as a GEF for Rab11 based on genetic evidence, but conflicting biochemical experiments have created uncertainty regarding Rab11 activation. Using physiological Rab-GEF reconstitution reactions, we now provide definitive evidence that TRAPPII is a bona fide GEF for the yeast Rab11 homologues Ypt31/32. We also uncover a direct role for Arf1, a distinct GTPase, in recruiting TRAPPII to anionic membranes. Given the known role of Ypt31/32 in stimulating activation of Arf1, a bidirectional cross talk mechanism appears to drive biogenesis of secretory and endocytic recycling vesicles. By coordinating simultaneous activation of two essential GTPase pathways, this mechanism ensures recruitment of the complete set of effectors needed for vesicle formation, transport, and tethering.
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Affiliation(s)
- Laura L Thomas
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853
| | - J Christopher Fromme
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853
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47
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Running up that hill: How to create cellular lipid gradients by lipid counter-flows. Biochimie 2016; 130:115-121. [DOI: 10.1016/j.biochi.2016.08.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 08/07/2016] [Indexed: 11/21/2022]
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48
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Lipid transfer proteins and the tuning of compartmental identity in the Golgi apparatus. Chem Phys Lipids 2016; 200:42-61. [DOI: 10.1016/j.chemphyslip.2016.06.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2016] [Revised: 06/21/2016] [Accepted: 06/22/2016] [Indexed: 11/23/2022]
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49
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Imada K, Nakamura T. The exocytic Rabs Ypt3 and Ypt2 regulate the early step of biogenesis of the spore plasma membrane in fission yeast. Mol Biol Cell 2016; 27:3317-3328. [PMID: 27630265 PMCID: PMC5170864 DOI: 10.1091/mbc.e16-03-0162] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 09/07/2016] [Indexed: 11/24/2022] Open
Abstract
Two Rabs, Ypt3 and Ypt2, regulating the trafficking of Golgi-derived secretory vesicles have key roles in biogenesis of the spore plasma membrane in fission yeast. During sporulation, the Rabs and secretory vesicles relocalize at the meiotic spindle pole body, where spore plasma membrane formation subsequently initiates. During fission yeast sporulation, a membrane compartment called the forespore membrane (FSM) is newly formed on the spindle pole body (SPB). The FSM expands by membrane vesicle fusion, encapsulates the daughter nucleus resulting from meiosis, and eventually matures into the plasma membrane of the spore. Although many of the genes involved in FSM formation have been identified, its molecular mechanism is not fully understood. Here a genetic screen for sporulation-deficient mutations identified Ypt3, a Rab-family small GTPase known to function in the exocytic pathway. The ypt3-ki8 mutant showed defects in both the initiation of FSM biogenesis and FSM expansion. We also show that a mutation in Ypt2, another Rab protein that may function in the same pathway as Ypt3, compromises the initiation of FSM formation. As meiosis proceeds, both GFP-Ypt3 and GFP-Ypt2 are observed at the SPB and then relocalize to the FSM. Their localizations at the SPB precede FSM formation and depend on the meiotic SPB component Spo13, a putative GDP/GTP exchange factor for Ypt2. Given that Spo13 is essential for initiating FSM formation, these results suggest that two exocytic Rabs, Ypt3 and Ypt2, regulate the initiation of FSM formation on the SPB in concert with Spo13.
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Affiliation(s)
- Kazuki Imada
- Department of Biology, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Taro Nakamura
- Department of Biology, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan
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50
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Abstract
Most functions of eukaryotic cells are controlled by cellular membranes, which are not static entities but undergo frequent budding, fission, fusion, and sculpting reactions collectively referred to as membrane dynamics. Consequently, regulation of membrane dynamics is crucial for cellular functions. A key mechanism in such regulation is the reversible recruitment of cytosolic proteins or protein complexes to specific membranes at specific time points. To a large extent this recruitment is orchestrated by phosphorylated derivatives of the membrane lipid phosphatidylinositol, known as phosphoinositides. The seven phosphoinositides found in nature localize to distinct membrane domains and recruit distinct effectors, thereby contributing strongly to the maintenance of membrane identity. Many of the phosphoinositide effectors are proteins that control membrane dynamics, and in this review we discuss the functions of phosphoinositides in membrane dynamics during exocytosis, endocytosis, autophagy, cell division, cell migration, and epithelial cell polarity, with emphasis on protein effectors that are recruited by specific phosphoinositides during these processes.
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Affiliation(s)
- Kay O Schink
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, N-0379 Oslo, Norway; , .,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, N-0379 Oslo, Norway
| | - Kia-Wee Tan
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, N-0379 Oslo, Norway; , .,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, N-0379 Oslo, Norway
| | - Harald Stenmark
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, N-0379 Oslo, Norway; , .,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, N-0379 Oslo, Norway.,Centre of Molecular Inflammation Research, Faculty of Medicine, Norwegian University of Science and Technology, N-7491 Trondheim, Norway
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