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Foo S, Cazenave-Gassiot A, Wenk MR, Oliferenko S. Diacylglycerol at the inner nuclear membrane fuels nuclear envelope expansion in closed mitosis. J Cell Sci 2023; 136:286881. [PMID: 36695178 DOI: 10.1242/jcs.260568] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 12/22/2022] [Indexed: 01/26/2023] Open
Abstract
Nuclear envelope (NE) expansion must be controlled to maintain nuclear shape and function. The nuclear membrane expands massively during closed mitosis, enabling chromosome segregation within an intact NE. Phosphatidic acid (PA) and diacylglycerol (DG) can both serve as biosynthetic precursors for membrane lipid synthesis. How they are regulated in time and space and what the implications are of changes in their flux for mitotic fidelity are largely unknown. Using genetically encoded PA and DG probes, we show that DG is depleted from the inner nuclear membrane during mitosis in the fission yeast Schizosaccharomyces pombe, but PA does not accumulate, indicating that it is rerouted to membrane synthesis. We demonstrate that DG-to-PA conversion catalyzed by the diacylglycerol kinase Dgk1 (also known as Ptp4) and direct glycerophospholipid synthesis from DG by diacylglycerol cholinephosphotransferase/ethanolaminephosphotransferase Ept1 reinforce NE expansion. We conclude that DG consumption through both the de novo pathway and the Kennedy pathway fuels a spike in glycerophospholipid biosynthesis, controlling NE expansion and, ultimately, mitotic fidelity.
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Affiliation(s)
- Sherman Foo
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.,Randall Centre for Cell and Molecular Biophysics, School of Basic and Medical Biosciences, King's College London, London SE1 1UL, UK
| | - Amaury Cazenave-Gassiot
- Singapore Lipidomics Incubator, Life Sciences Institute and Precision Medicine Translational Research Program, Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, MD7, 8 Medical Drive, 117596 Singapore
| | - Markus R Wenk
- Singapore Lipidomics Incubator, Life Sciences Institute and Precision Medicine Translational Research Program, Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, MD7, 8 Medical Drive, 117596 Singapore
| | - Snezhana Oliferenko
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.,Randall Centre for Cell and Molecular Biophysics, School of Basic and Medical Biosciences, King's College London, London SE1 1UL, UK
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2
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Pang C, Wen L, Lu X, Luo S, Qin H, Zhang X, Zhu B, Luo S. Ruboxistaurin maintains the bone mass of subchondral bone for blunting osteoarthritis progression by inhibition of osteoclastogenesis and bone resorption activity. Biomed Pharmacother 2020; 131:110650. [PMID: 32882584 DOI: 10.1016/j.biopha.2020.110650] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2020] [Revised: 08/12/2020] [Accepted: 08/17/2020] [Indexed: 12/20/2022] Open
Abstract
Osteoarthritis (OA) is a common degenerative disease with a series of changes occurring in aging cartilage, such as increased oxidative stress, decreased markers of healthy cartilage and alterations in the autophagy pathway. And increasing evidence indicates that osteoarthritis affects the whole joint, including both cartilage and subchondral bone. The agents that can effectively suppress chondrocyte degradation and subchondral bone deterioration are crucial for the prevention and treatment of OA. Ruboxistaurin (RU), an orally active protein kinase C inhibitor, can reduce macrophage adhesion to endothelial cells and relieve the local inflammation when applicating in diabetes and kinds of aging-related vasculopathy, which were realized by its effects on decreasing inflammatory cytokines' expression and increasing cell anti-oxidative stress ability. However, whether ruboxistaurin protects against OA remains unknown. In this study, we investigated the therapeutic effects of ruboxistaurin in an anterior cruciate ligament transection (ACLT)-induced OA model by preventing the bone mass loss of subchondral bone. We found that ruboxistaurin can effectively alleviate ACLT-induced osteoarthritis, as demonstrated by the phenomenon of correcting pathological bone loss caused by osteoclasts overactivated in the early stage of osteoarthritis and protecting against articular cartilage degeneration. Moreover, we found that ruboxistaurin inhibited osteoclast formation and resorption activity by suppressing the expressions of osteoclast-related genes and (PKCδ/MAPKs) signaling cascade. Taken together, these results show that ruboxistaurin may be a potential therapeutic agent for rescuing abnormal subchondral bone deterioration and cartilage degradation in OA and reverses the vicious cycle related to osteoarthritis.
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Affiliation(s)
- Cong Pang
- Department of Orthopedics, The Ninth Affiliated Hospital of Guangxi Medical University, Beihai, Guangxi, China; Department of Orthopedics, Shaoxing People's Hospital (Shaoxing Hospital, Zhejiang University School of Medicine), Shaoxing, Zhejiang, China
| | - Liangbao Wen
- Department of Neurosurgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi, China
| | - Xuanyuan Lu
- Department of Orthopedics, Shaoxing People's Hospital (Shaoxing Hospital, Zhejiang University School of Medicine), Shaoxing, Zhejiang, China
| | - Shanchao Luo
- Guangxi Postdoctoral Innovation Practice Base, The Ninth Affiliated Hospital of Guangxi Medical University, Beihai, Guangxi, China
| | - Haikuo Qin
- Department of Orthopedics, The Ninth Affiliated Hospital of Guangxi Medical University, Beihai, Guangxi, China
| | - Xuehui Zhang
- Department of Nuclear Medicine, The Ninth Affiliated Hospital of Guangxi Medical University, Beihai, Guangxi, China
| | - Bikang Zhu
- Department of Orthopedics, The Ninth Affiliated Hospital of Guangxi Medical University, Beihai, Guangxi, China
| | - Shixing Luo
- Department of Orthopedics, The Ninth Affiliated Hospital of Guangxi Medical University, Beihai, Guangxi, China.
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3
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Ventimiglia LN, Cuesta-Geijo MA, Martinelli N, Caballe A, Macheboeuf P, Miguet N, Parnham IM, Olmos Y, Carlton JG, Weissenhorn W, Martin-Serrano J. CC2D1B Coordinates ESCRT-III Activity during the Mitotic Reformation of the Nuclear Envelope. Dev Cell 2018; 47:547-563.e6. [PMID: 30513301 PMCID: PMC6286407 DOI: 10.1016/j.devcel.2018.11.012] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 08/13/2018] [Accepted: 11/02/2018] [Indexed: 11/29/2022]
Abstract
The coordinated reformation of the nuclear envelope (NE) after mitosis re-establishes the structural integrity and the functionality of the nuclear compartment. The endosomal sorting complex required for transport (ESCRT) machinery, a membrane remodeling pathway that is highly conserved in eukaryotes, has been recently involved in NE resealing by mediating the annular fusion of the nuclear membrane (NM). We show here that CC2D1B, a regulator of ESCRT polymerization, is required to re-establish the nuclear compartmentalization by coordinating endoplasmic reticulum (ER) membrane deposition around chromatin disks with ESCRT-III recruitment to the reforming NE. Accordingly, CC2D1B determines the spatiotemporal distribution of the CHMP7-ESCRT-III axis during NE reformation. Crucially, in CC2D1B-depleted cells, ESCRT activity is uncoupled from Spastin-mediated severing of spindle microtubules, resulting in persisting microtubules that compromise nuclear morphology. Therefore, we reveal CC2D1B as an essential regulatory factor that licenses the formation of ESCRT-III polymers to ensure the orderly reformation of the NE.
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Affiliation(s)
- Leandro N Ventimiglia
- Department of Infectious Diseases, King's College London, Faculty of Life Sciences & Medicine, London SE1 9RT, UK
| | - Miguel Angel Cuesta-Geijo
- Department of Infectious Diseases, King's College London, Faculty of Life Sciences & Medicine, London SE1 9RT, UK
| | - Nicolas Martinelli
- CNRS, University Grenoble Alpes, CEA, Institut de Biologie Structurale (IBS), 38000 Grenoble, France
| | - Anna Caballe
- Department of Infectious Diseases, King's College London, Faculty of Life Sciences & Medicine, London SE1 9RT, UK
| | - Pauline Macheboeuf
- CNRS, University Grenoble Alpes, CEA, Institut de Biologie Structurale (IBS), 38000 Grenoble, France
| | - Nolwenn Miguet
- CNRS, University Grenoble Alpes, CEA, Institut de Biologie Structurale (IBS), 38000 Grenoble, France
| | - Ian M Parnham
- Department of Infectious Diseases, King's College London, Faculty of Life Sciences & Medicine, London SE1 9RT, UK
| | - Yolanda Olmos
- Division of Cancer Studies, King's College London, London SE1 1UL, UK
| | - Jeremy G Carlton
- Division of Cancer Studies, King's College London, London SE1 1UL, UK
| | - Winfried Weissenhorn
- CNRS, University Grenoble Alpes, CEA, Institut de Biologie Structurale (IBS), 38000 Grenoble, France
| | - Juan Martin-Serrano
- Department of Infectious Diseases, King's College London, Faculty of Life Sciences & Medicine, London SE1 9RT, UK.
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4
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Chung GHC, Domart MC, Peddie C, Mantell J, Mclaverty K, Arabiotorre A, Hodgson L, Byrne RD, Verkade P, Arkill K, Collinson LM, Larijani B. Acute depletion of diacylglycerol from the cis-Golgi affects localized nuclear envelope morphology during mitosis. J Lipid Res 2018; 59:1402-1413. [PMID: 29895700 PMCID: PMC6071775 DOI: 10.1194/jlr.m083899] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 06/12/2018] [Indexed: 12/28/2022] Open
Abstract
Dysregulation of nuclear envelope (NE) assembly results in various cancers; for example, renal and some lung carcinomas ensue due to NE malformation. The NE is a dynamic membrane compartment and its completion during mitosis is a highly regulated process, but the detailed mechanism still remains incompletely understood. Previous studies have found that isolated diacylglycerol (DAG)-containing vesicles are essential for completing the fusion of the NE in nonsomatic cells. We investigated the impact of DAG depletion from the cis-Golgi in mammalian cells on NE reassembly. Using advanced electron microscopy, we observed an enriched DAG population of vesicles at the vicinity of the NE gaps of telophase mammalian cells. We applied a mini singlet oxygen generator-C1-domain tag that localized DAG-enriched vesicles at the perinuclear region, which suggested the existence of NE fusogenic vesicles. We quantified the impact of Golgi-DAG depletion by measuring the in situ NE rim curvature of the reforming NE. The rim curvature in these cells was significantly reduced compared with controls, which indicated a localized defect in NE morphology. Our novel results demonstrate the significance of the role of DAG from the cis-Golgi for the regulation of NE assembly.
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Affiliation(s)
- Gary Hong Chun Chung
- Cell Biophysics Laboratory, Ikerbasque Basque Foundation for Science, Research Centre for Experimental Marine Biology and Biotechnology (PiE) and Biofísika Institute (UPV/EHU, CSIC), University of the Basque Country, Barrio Sarriena s/n 48940, Leioa, Spain
| | - Marie-Charlotte Domart
- Electron Microscopy Science Technology Platform, Francis Crick Institute, London, United Kingdom
| | - Christopher Peddie
- Electron Microscopy Science Technology Platform, Francis Crick Institute, London, United Kingdom
| | - Judith Mantell
- School of Biochemistry, Faculty of Biomedical Sciences, University of Bristol, Bristol, United Kingdom
| | - Kieran Mclaverty
- Cell Biophysics Laboratory, Ikerbasque Basque Foundation for Science, Research Centre for Experimental Marine Biology and Biotechnology (PiE) and Biofísika Institute (UPV/EHU, CSIC), University of the Basque Country, Barrio Sarriena s/n 48940, Leioa, Spain
- School of Biochemistry, Faculty of Biomedical Sciences, University of Bristol, Bristol, United Kingdom
| | - Angela Arabiotorre
- Cell Biophysics Laboratory, Ikerbasque Basque Foundation for Science, Research Centre for Experimental Marine Biology and Biotechnology (PiE) and Biofísika Institute (UPV/EHU, CSIC), University of the Basque Country, Barrio Sarriena s/n 48940, Leioa, Spain
| | - Lorna Hodgson
- School of Biochemistry, Faculty of Biomedical Sciences, University of Bristol, Bristol, United Kingdom
| | - Richard D Byrne
- Cell Biophysics Laboratory, Ikerbasque Basque Foundation for Science, Research Centre for Experimental Marine Biology and Biotechnology (PiE) and Biofísika Institute (UPV/EHU, CSIC), University of the Basque Country, Barrio Sarriena s/n 48940, Leioa, Spain
| | - Paul Verkade
- School of Biochemistry, Faculty of Biomedical Sciences, University of Bristol, Bristol, United Kingdom
- Wolfson Bioimaging Facility, University of Bristol, Bristol, United Kingdom
| | - Kenton Arkill
- Cell Biophysics Laboratory, Ikerbasque Basque Foundation for Science, Research Centre for Experimental Marine Biology and Biotechnology (PiE) and Biofísika Institute (UPV/EHU, CSIC), University of the Basque Country, Barrio Sarriena s/n 48940, Leioa, Spain
- Division of Cancer and Stem Cells, The Queen's Medical Centre, University of Nottingham, Nottingham, United Kingdom
| | - Lucy M Collinson
- Electron Microscopy Science Technology Platform, Francis Crick Institute, London, United Kingdom
| | - Banafshé Larijani
- Cell Biophysics Laboratory, Ikerbasque Basque Foundation for Science, Research Centre for Experimental Marine Biology and Biotechnology (PiE) and Biofísika Institute (UPV/EHU, CSIC), University of the Basque Country, Barrio Sarriena s/n 48940, Leioa, Spain
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5
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Lete MG, Byrne RD, Alonso A, Poccia D, Larijani B. Vesicular PtdIns(3,4,5)P3 and Rab7 are key effectors of sea urchin zygote nuclear membrane fusion. J Cell Sci 2016; 130:444-452. [PMID: 27927752 DOI: 10.1242/jcs.193771] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 11/14/2016] [Indexed: 12/26/2022] Open
Abstract
Regulation of nuclear envelope dynamics is an important example of the universal phenomena of membrane fusion. The signalling molecules involved in nuclear membrane fusion might also be conserved during the formation of both pronuclear and zygote nuclear envelopes in the fertilised egg. Here, we determine that class-I phosphoinositide 3-kinases (PI3Ks) are needed for in vitro nuclear envelope formation. We show that, in vivo, PtdIns(3,4,5)P3 is transiently located in vesicles around the male pronucleus at the time of nuclear envelope formation, and around male and female pronuclei before membrane fusion. We illustrate that class-I PI3K activity is also necessary for fusion of the female and male pronuclear membranes. We demonstrate, using coincidence amplified Förster resonance energy transfer (FRET) monitored using fluorescence lifetime imaging microscopy (FLIM), a protein-lipid interaction of Rab7 GTPase and PtdIns(3,4,5)P3 that occurs during pronuclear membrane fusion to create the zygote nuclear envelope. We present a working model, which includes several molecular steps in the pathways controlling fusion of nuclear envelope membranes.
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Affiliation(s)
- Marta G Lete
- Cell Biophysics Laboratory, Ikerbasque Basque Foundation for Science, Research Centre for Experimental Marine Biology and Biotechnology (PiE) and Biofísika Instituto (UPV/EHU, CSIC), University of the Basque Country, Areatza Hiribidea, 47, 48620 Plentzia, Spain.,Biofísika Instituto (UPV/EHU, CSIC) and Departamento de Bioquímica, University of the Basque Country, Barrio Sarriena s/n, Leioa 48940, Spain.,Cell Biophysics Laboratory, Research Centre for Experimental Marine Biology and Biotechnology (PiE), Biofisika Instituto (UPV/EHU,CSIC) and, University of the Basque Country, Leioa 48940, Spain
| | - Richard D Byrne
- The Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, London NW7 1AA, UK
| | - Alicia Alonso
- Biofísika Instituto (UPV/EHU, CSIC) and Departamento de Bioquímica, University of the Basque Country, Barrio Sarriena s/n, Leioa 48940, Spain
| | - Dominic Poccia
- Department of Biology, Amherst College, Amherst, MA 01002, USA
| | - Banafshé Larijani
- Cell Biophysics Laboratory, Research Centre for Experimental Marine Biology and Biotechnology (PiE), Biofisika Instituto (UPV/EHU,CSIC) and, University of the Basque Country, Leioa 48940, Spain
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6
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Abstract
FRET-FLIM techniques have wide application in the study of protein and protein-lipid interactions in cells. We have pioneered an imaging platform for accurate detection of functional states of proteins and their interactions in fixed cells. This platform, two-site-amplified Förster resonance energy transfer (a-FRET), allows greater signal generation while retaining minimal noise thus enabling application of fluorescence lifetime imaging microscopy (FLIM) to be routinely deployed in different types of cells and tissue. We have used the method described here, time-resolved FRET monitored by two-photon FLIM, to demonstrate the direct interaction of Phospholipase Cγ (PLCγ) by Src Family Kinase 1 (SFK1) during nuclear envelope formation and during male and female pronuclear membrane fusion in fertilized sea urchin eggs. We describe here a generic method that can be applied to monitor any proteins of interest.
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Affiliation(s)
| | - Banafshé Larijani
- Cell Biophysics Laboratory, Ikerbasque Basque Foundation for Science, Unidad de Biofísica (CSIC UPV/EHU), Leioa, Bizkaia, Spain
- Research Centre for Experimental Marine Biology and Biotechnology (PiE), University of the Basque Country (UPV), Leioa, Bizkaia, Spain
| | - Dominic L Poccia
- Department of Biology, Amherst College, 324 McGuire Life Sciences Building, P.O. Box: AC# 2237, Amherst, MA, 01002, USA.
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7
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Lete MG, Sot J, Gil D, Valle M, Medina M, Goñi FM, Alonso A. Histones cause aggregation and fusion of lipid vesicles containing phosphatidylinositol-4-phosphate. Biophys J 2015; 108:863-871. [PMID: 25692591 DOI: 10.1016/j.bpj.2014.12.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Revised: 12/07/2014] [Accepted: 12/09/2014] [Indexed: 12/13/2022] Open
Abstract
In a previous article, we demonstrated that histones (H1 or histone octamers) interact with negatively charged bilayers and induce extensive aggregation of vesicles containing phosphatidylinositol-4-phosphate (PIP) and, to a lesser extent, vesicles containing phosphatidylinositol (PI). Here, we found that vesicles containing PIP, but not those containing PI, can undergo fusion induced by histones. Fusion was demonstrated through the observation of intervesicular mixing of total lipids and inner monolayer lipids, and by ultrastructural and confocal microscopy studies. Moreover, in both PI- and PIP-containing vesicles, histones caused permeabilization and release of vesicular aqueous contents, but the leakage mechanism was different (all-or-none for PI and graded release for PIP vesicles). These results indicate that histones could play a role in the remodeling of the nuclear envelope that takes place during the mitotic cycle.
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Affiliation(s)
- Marta G Lete
- Unidad de Biofísica (CSIC, UPV/EHU), Universidad del País Vasco, Leioa, Spain; Departamento de Bioquímica, Universidad del País Vasco, Leioa, Spain
| | - Jesus Sot
- Unidad de Biofísica (CSIC, UPV/EHU), Universidad del País Vasco, Leioa, Spain; Departamento de Bioquímica, Universidad del País Vasco, Leioa, Spain
| | - David Gil
- Structural Biology Unit, Center for Cooperative Research in Biosciences, CIC bioGUNE, Derio, Spain
| | - Mikel Valle
- Structural Biology Unit, Center for Cooperative Research in Biosciences, CIC bioGUNE, Derio, Spain
| | - Milagros Medina
- Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Ciencias, Universidad de Zaragoza, Zaragoza, Spain; Instituto de Biocomputación y Física de Sistemas Complejos, Unidad Asociada BIFI-IQFR, Universidad de Zaragoza, Zaragoza, Spain
| | - Felix M Goñi
- Unidad de Biofísica (CSIC, UPV/EHU), Universidad del País Vasco, Leioa, Spain; Departamento de Bioquímica, Universidad del País Vasco, Leioa, Spain
| | - Alicia Alonso
- Unidad de Biofísica (CSIC, UPV/EHU), Universidad del País Vasco, Leioa, Spain; Departamento de Bioquímica, Universidad del País Vasco, Leioa, Spain.
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8
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Abstract
The fusogenic lipid diacylglycerol is essential for remodeling gamete and zygote nuclear envelopes (NE) during early embryogenesis. It is unclear whether upstream signaling molecules are likewise conserved. Here we demonstrate PLCγ and its activator SFK1, which co-operate during male pronuclear envelope formation, also promote the subsequent male and female pronuclear fusion. PLCγ and SFK1 interact directly at the fusion site leading to PLCγ activation. This is accompanied by a spatially restricted reduction of PtdIns(4,5)P2. Consequently, pronuclear fusion is blocked by PLCγ or SFK1 inhibition. These findings identify new regulators of events in the early embryo and suggest a conserved "toolkit" of fusion machinery drives successive NE fusion events during embryogenesis.
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Affiliation(s)
- Richard D Byrne
- a Cell Biophysics Laboratory; Cancer Research UK; London Research Institute; London, UK
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9
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Jethwa N, Chung GHC, Lete MG, Alonso A, Byrne RD, Calleja V, Larijani B. Endomembrane PtdIns(3,4,5)P3 activates the PI3K-Akt pathway. J Cell Sci 2015; 128:3456-65. [PMID: 26240177 DOI: 10.1242/jcs.172775] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Accepted: 07/29/2015] [Indexed: 12/18/2022] Open
Abstract
PKB/Akt activation is a common step in tumour growth, proliferation and survival. Akt activation is understood to occur at the plasma membrane of cells in response to growth factor stimulation and local production of the phosphoinositide lipid phosphatidylinositol (3,4,5)-trisphosphate [PtdIns(3,4,5)P3] following phosphoinositide 3-kinase (PI3K) activation. The metabolism and turnover of phosphoinositides is complex--they act as signalling molecules as well as structural components of biological membranes. The localisation and significance of internal pools of PtdIns(3,4,5)P3 has long been speculated upon. By using transfected and recombinant protein probes for PtdIns(3,4,5)P3, we show that PtdIns(3,4,5)P3 is enriched in the nuclear envelope and early endosomes. By exploiting an inducible dimerisation device to recruit Akt to these compartments, we demonstrate that Akt can be locally activated in a PtdIns(3,4,5)P3-dependent manner and has the potential to phosphorylate compartmentally localised downstream substrates. This could be an important mechanism to regulate Akt isoform substrate specificity or influence the timing and duration of PI3K pathway signalling. Defects in phosphoinositide metabolism and localisation are known to contribute to cancer, suggesting that interactions at subcellular compartments might be worthwhile targets for therapeutic intervention.
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Affiliation(s)
- Nirmal Jethwa
- Cell Biophysics Laboratory, Cancer Research UK, London WC2A 3LY, UK
| | - Gary H C Chung
- Cell Biophysics Laboratory, Cancer Research UK, London WC2A 3LY, UK
| | - Marta G Lete
- Cell Biophysics Laboratory, Cancer Research UK, London WC2A 3LY, UK Unidad de Biofísica (CSIC, UPV/EHU), Universidad del País Vasco, Barrio Sarriena s/n, Leioa 48940, Spain Cell Biophysics Laboratory, Ikerbasque Basque Foundation for Science, Unidad de Biofísica (CSIC, UPV/EHU) and Research Centre for Experimental Marine Biology and Biotechnology (PiE), University of the Basque Country (UPV/EHU), Leioa 48940, Spain
| | - Alicia Alonso
- Unidad de Biofísica (CSIC, UPV/EHU), Universidad del País Vasco, Barrio Sarriena s/n, Leioa 48940, Spain
| | - Richard D Byrne
- Cell Biophysics Laboratory, Cancer Research UK, London WC2A 3LY, UK Signalling Programme, The Babraham Institute, Cambridge CB22 3AT, UK
| | - Véronique Calleja
- Cell Biophysics Laboratory, Cancer Research UK, London WC2A 3LY, UK Protein Phosphorylation Laboratory, The Francis Crick Institute, London WC2A 3LY, UK
| | - Banafshé Larijani
- Cell Biophysics Laboratory, Cancer Research UK, London WC2A 3LY, UK Cell Biophysics Laboratory, Ikerbasque Basque Foundation for Science, Unidad de Biofísica (CSIC, UPV/EHU) and Research Centre for Experimental Marine Biology and Biotechnology (PiE), University of the Basque Country (UPV/EHU), Leioa 48940, Spain
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10
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Larijani B, Hamati F, Kundu A, Chung GC, Domart MC, Collinson L, Poccia DL. Principle of duality in phospholipids: regulators of membrane morphology and dynamics. Biochem Soc Trans 2014; 42:1335-42. [PMID: 25233412 DOI: 10.1042/BST20140224] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
To suggest and develop intelligent strategies to comprehend the regulation of organelle formation, a deeper mechanistic interpretation requires more than just the involvement of proteins. Our approaches link the formation of endomembranes with both signalling and membrane physical properties. Hitherto, membrane morphology, local physical structure and signalling have not been well integrated. Our studies derive from a cross-disciplinary approach undertaken to determine the molecular mechanisms of nuclear envelope assembly in echinoderm and mammalian cells. Our findings have led to the demonstration of a direct role for phosphoinositides and their derivatives in nuclear membrane formation. We have shown that phosphoinositides and their derivatives, as well as acting as second messengers, are modulators of membrane morphology, and their modifying enzymes regulate nuclear envelope formation. In addition, we have shown that echinoderm eggs can be exploited as a milieu to directly study the roles of phospholipids in maintaining organelle shape. The use of the echinoderm egg is a significant step forward in obtaining direct information about membrane physical properties in situ rather than using simpler models which do not provide a complete mechanistic insight into the role of phospholipids in membrane dynamics.
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11
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Abstract
The initial steps of the Human Immunodeficiency Virus (HIV) replication cycle play a crucial role that arbitrates viral tropism and infection efficiency. Before the release of its genome into the host cell cytoplasm, viruses operate a complex sequence of events that take place at the plasma membrane of the target cell. The first step is the binding of the HIV protein envelope (Env) to the cellular receptor CD4. This triggers conformational changes of the gp120 viral protein that allow its interaction with a co-receptor that can be either CCR5 or CXCR4, defining the tropism of the virus entering the cell. This sequential interaction finally drives the fusion of the viral and host cell membrane or to the endocytosis of the viruses. Here, we discuss how the membrane composition and organization of both the virus and the target cell can affect these steps and thus influence the capability of the viruses to infect cells. An overview of lipid role in HIV infection is proposed. We discuss the influence of lipid composition on HIV early steps of infection. We discuss the role of membrane organization an dynamics in HIV entry.
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Affiliation(s)
- Fabrice Dumas
- CNRS, IPBS (Institut de Pharmacologie et de Biologie Structurale), 205 route de Narbonne, F-31077 Toulouse, France; Université de Toulouse, UPS, IPBS, F-31077 Toulouse, France.
| | - Pascal Preira
- CNRS, IPBS (Institut de Pharmacologie et de Biologie Structurale), 205 route de Narbonne, F-31077 Toulouse, France
| | - Laurence Salomé
- CNRS, IPBS (Institut de Pharmacologie et de Biologie Structurale), 205 route de Narbonne, F-31077 Toulouse, France.
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12
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Peddie CJ, Blight K, Wilson E, Melia C, Marrison J, Carzaniga R, Domart MC, O'Toole P, Larijani B, Collinson LM. Correlative and integrated light and electron microscopy of in-resin GFP fluorescence, used to localise diacylglycerol in mammalian cells. Ultramicroscopy 2014; 143:3-14. [PMID: 24637200 PMCID: PMC4045205 DOI: 10.1016/j.ultramic.2014.02.001] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Revised: 02/10/2014] [Accepted: 02/12/2014] [Indexed: 12/11/2022]
Abstract
Fluorescence microscopy of GFP-tagged proteins is a fundamental tool in cell biology, but without seeing the structure of the surrounding cellular space, functional information can be lost. Here we present a protocol that preserves GFP and mCherry fluorescence in mammalian cells embedded in resin with electron contrast to reveal cellular ultrastructure. Ultrathin in-resin fluorescence (IRF) sections were imaged simultaneously for fluorescence and electron signals in an integrated light and scanning electron microscope. We show, for the first time, that GFP is stable and active in resin sections in vacuo. We applied our protocol to study the subcellular localisation of diacylglycerol (DAG), a modulator of membrane morphology and membrane dynamics in nuclear envelope assembly. We show that DAG is localised to the nuclear envelope, nucleoplasmic reticulum and curved tips of the Golgi apparatus. With these developments, we demonstrate that integrated imaging is maturing into a powerful tool for accurate molecular localisation to structure.
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Affiliation(s)
- Christopher J Peddie
- Electron Microscopy Unit, London Research Institute, Cancer Research UK, London WC2A 3LY, UK
| | - Ken Blight
- Electron Microscopy Unit, London Research Institute, Cancer Research UK, London WC2A 3LY, UK
| | - Emma Wilson
- Electron Microscopy Unit, London Research Institute, Cancer Research UK, London WC2A 3LY, UK
| | - Charlotte Melia
- Electron Microscopy Unit, London Research Institute, Cancer Research UK, London WC2A 3LY, UK; Cell Biophysics Laboratory, London Research Institute, Cancer Research UK, London WC2A 3LY, UK; Department of Molecular Cell Biology, Leiden University Medical Centre, 2300 RC Leiden, The Netherlands
| | - Jo Marrison
- Department of Biology, The University of York, Heslington, York, UK
| | - Raffaella Carzaniga
- Electron Microscopy Unit, London Research Institute, Cancer Research UK, London WC2A 3LY, UK
| | - Marie-Charlotte Domart
- Electron Microscopy Unit, London Research Institute, Cancer Research UK, London WC2A 3LY, UK; Cell Biophysics Laboratory, London Research Institute, Cancer Research UK, London WC2A 3LY, UK
| | - Peter O'Toole
- Department of Biology, The University of York, Heslington, York, UK
| | - Banafshe Larijani
- Cell Biophysics Laboratory, London Research Institute, Cancer Research UK, London WC2A 3LY, UK; Cell Biophysics Laboratory, Unidad de Biofísica (CSIC-UPV/EHU),Sarriena s/n, 48940 Leioa, Spain; IKERBASQUE, Basque Foundation for Science, Bilbao, Spain
| | - Lucy M Collinson
- Electron Microscopy Unit, London Research Institute, Cancer Research UK, London WC2A 3LY, UK
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Abstract
After the initial observation that lipids form a considerable part of biological membranes, the details of the physical role of lipids in biological systems have emerged gradually. There have been few 'Eureka' moments in which a class or individual lipid has appeared as a game-changing physical player. However, evidence collected in the last five years suggests that that notion may be about to change. In chemical biology studies, inositides are increasingly showing themselves to be lipids that have a physical influence on membrane systems that is as strong as their biological (signalling) one. Additionally, recent evidence has shown that the concentration of at least one inositide changes during important stages of the cell cycle, and not in a manner consistent with its traditional signalling roles. The balance between these data is explored and a forward-looking view is proposed.
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Affiliation(s)
- Samuel Furse
- Membrane Biochemistry and Biophysics, Universiteit Utrecht, Kruytgebouw, Padualaan 8, Utrecht, 3584 CH The Netherlands
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15
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Domart MC, Hobday TMC, Peddie CJ, Chung GHC, Wang A, Yeh K, Jethwa N, Zhang Q, Wakelam MJO, Woscholski R, Byrne RD, Collinson LM, Poccia DL, Larijani B. Acute manipulation of diacylglycerol reveals roles in nuclear envelope assembly & endoplasmic reticulum morphology. PLoS One 2012; 7:e51150. [PMID: 23227247 PMCID: PMC3515572 DOI: 10.1371/journal.pone.0051150] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Accepted: 10/29/2012] [Indexed: 12/16/2022] Open
Abstract
The functions and morphology of cellular membranes are intimately related and depend not only on their protein content but also on the repertoire of lipids that comprise them. In the absence of in vivo data on lipid asymmetry in endomembranes, it has been argued that motors, scaffolding proteins or integral membrane proteins rather than non-lamellar bilayer lipids such as diacylglycerol (DAG), are responsible for shaping of organelles, local membrane curvature and fusion. The effects of direct alteration of levels of such lipids remain predominantly uninvestigated. Diacylglycerol (DAG) is a well documented second messenger. Here we demonstrate two additional conserved functions of DAG: a structural role in organelle morphology, and a role in localised extreme membrane curvature required for fusion for which proteins alone are insufficient. Acute and inducible DAG depletion results in failure of the nuclear envelope (NE) to reform at mitosis and reorganisation of the ER into multi-lamellar sheets as revealed by correlative light and electron microscopy and 3D reconstructions. Remarkably, depleted cells divide without a complete NE, and unless rescued by 1,2 or 1,3 DAG soon die. Attenuation of DAG levels by enzyme microinjection into echinoderm eggs and embryos also results in alterations of ER morphology and nuclear membrane fusion. Our findings demonstrate that DAG is an in vivo modulator of organelle morphology in mammalian and echinoderm cells, indicating a fundamental role conserved across the deuterostome superphylum.
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Affiliation(s)
- Marie-Charlotte Domart
- Cell Biophysics Laboratory, London Research Institute, Cancer Research United Kingdom, London, United Kingdom
| | - Tina M. C. Hobday
- Cell Biophysics Laboratory, London Research Institute, Cancer Research United Kingdom, London, United Kingdom
| | - Christopher J. Peddie
- Electron Microscopy Unit, London Research Institute, Cancer Research United Kingdom, London, United Kingdom
| | - Gary H. C. Chung
- Cell Biophysics Laboratory, London Research Institute, Cancer Research United Kingdom, London, United Kingdom
| | - Alan Wang
- Department of Biology, Amherst College, Amherst, Massachusetts, United States of America
| | - Karen Yeh
- Department of Biology, Amherst College, Amherst, Massachusetts, United States of America
| | - Nirmal Jethwa
- Cell Biophysics Laboratory, London Research Institute, Cancer Research United Kingdom, London, United Kingdom
| | - Qifeng Zhang
- The Babraham Institute, Babraham Research Campus, Cambridge, United Kingdom
| | | | - Rudiger Woscholski
- Department of Chemistry, Faculty of Natural Sciences and Institute of Chemical Biology, Imperial College London, London, United Kingdom
| | - Richard D. Byrne
- Cell Biophysics Laboratory, London Research Institute, Cancer Research United Kingdom, London, United Kingdom
| | - Lucy M. Collinson
- Electron Microscopy Unit, London Research Institute, Cancer Research United Kingdom, London, United Kingdom
| | - Dominic L. Poccia
- Department of Biology, Amherst College, Amherst, Massachusetts, United States of America
| | - Banafshé Larijani
- Cell Biophysics Laboratory, London Research Institute, Cancer Research United Kingdom, London, United Kingdom
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Cremasco V, Decker CE, Stumpo D, Blackshear PJ, Nakayama KI, Nakayama K, Lupu TS, Graham DB, Novack DV, Faccio R. Protein kinase C-delta deficiency perturbs bone homeostasis by selective uncoupling of cathepsin K secretion and ruffled border formation in osteoclasts. J Bone Miner Res 2012; 27:2452-63. [PMID: 22806935 PMCID: PMC3498518 DOI: 10.1002/jbmr.1701] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 06/12/2012] [Accepted: 06/26/2012] [Indexed: 01/27/2023]
Abstract
Bone homeostasis requires stringent regulation of osteoclasts, which secrete proteolytic enzymes to degrade the bone matrix. Despite recent progress in understanding how bone resorption occurs, the mechanisms regulating osteoclast secretion, and in particular the trafficking route of cathepsin K vesicles, remain elusive. Using a genetic approach, we describe the requirement for protein kinase C-delta (PKCδ) in regulating bone resorption by affecting cathepsin K exocytosis. Importantly, PKCδ deficiency does not perturb formation of the ruffled border or trafficking of lysosomal vesicles containing the vacuolar-ATPase (v-ATPase). Mechanistically, we find that cathepsin K exocytosis is controlled by PKCδ through modulation of the actin bundling protein myristoylated alanine-rich C-kinase substrate (MARCKS). The relevance of our finding is emphasized in vivo because PKCδ-/- mice exhibit increased bone mass and are protected from pathological bone loss in a model of experimental postmenopausal osteoporosis. Collectively, our data provide novel mechanistic insights into the pathways that selectively promote secretion of cathepsin K lysosomes independently of ruffled border formation, providing evidence of the presence of multiple mechanisms that regulate lysosomal exocytosis in osteoclasts.
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Affiliation(s)
- Viviana Cremasco
- Department of Orthopaedics, Washington University School of Medicine, St. Louis, MO, USA
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17
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Byrne RD, Applebee C, Poccia DL, Larijani B. Dynamics of PLCγ and Src family kinase 1 interactions during nuclear envelope formation revealed by FRET-FLIM. PLoS One 2012; 7:e40669. [PMID: 22848394 DOI: 10.1371/journal.pone.0040669] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Accepted: 06/11/2012] [Indexed: 01/10/2023] Open
Abstract
The nuclear envelope (NE) breaks down and reforms during each mitotic cycle. A similar process happens to the sperm NE following fertilisation. The formation of the NE in both these circumstances involves endoplasmic reticulum membranes enveloping the chromatin, but PLCγ-dependent membrane fusion events are also essential. Here we demonstrate the activation of PLCγ by a Src family kinase (SFK1) during NE assembly. We show by time-resolved FRET for the first time the direct in vivo interaction and temporal regulation of PLCγ and SFK1 in sea urchins. As a prerequisite for protein activation, there is a rapid phosphorylation of PLCγ on its Y783 residue in response to GTP in vitro. This phosphorylation is dependent upon SFK activity; thus Y783 phosphorylation and NE assembly are susceptible to SFK inhibition. Y783 phosphorylation is also observed on the surface of the male pronucleus (MPN) in vivo during NE formation. Together the corroborative in vivo and in vitro data demonstrate the phosphorylation and activation of PLCγ by SFK1 during NE assembly. We discuss the potential generality of such a mechanism.
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18
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Goñi FM, Montes LR, Alonso A. Phospholipases C and sphingomyelinases: Lipids as substrates and modulators of enzyme activity. Prog Lipid Res 2012; 51:238-66. [DOI: 10.1016/j.plipres.2012.03.002] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Revised: 03/23/2012] [Accepted: 03/26/2012] [Indexed: 11/30/2022]
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19
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Lopez CI, Pelletán LE, Suhaiman L, De Blas GA, Vitale N, Mayorga LS, Belmonte SA. Diacylglycerol stimulates acrosomal exocytosis by feeding into a PKC- and PLD1-dependent positive loop that continuously supplies phosphatidylinositol 4,5-bisphosphate. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1821:1186-99. [PMID: 22609963 DOI: 10.1016/j.bbalip.2012.05.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Revised: 04/04/2012] [Accepted: 05/07/2012] [Indexed: 01/08/2023]
Abstract
Acrosomal exocytosis involves a massive fusion between the outer acrosomal and the plasma membranes of the spermatozoon triggered by stimuli that open calcium channels at the plasma membrane. Diacylglycerol has been implicated in the activation of these calcium channels. Here we report that this lipid promotes the efflux of intraacrosomal calcium and triggers exocytosis in permeabilized human sperm, implying that diacylglycerol activates events downstream of the opening of plasma membrane channels. Furthermore, we show that calcium and diacylglycerol converge in a signaling pathway leading to the production of phosphatidylinositol 4,5-bisphosphate (PIP(2)). Addition of diacylglycerol promotes the PKC-dependent activation of PLD1. Rescue experiments adding phosphatidic acid or PIP(2) and direct measurement of lipid production suggest that both PKC and PLD1 promote PIP(2) synthesis. Inhibition of different steps of the pathway was reverted by adenophostin, an agonist of IP(3)-sensitive calcium channels, indicating that PIP(2) is necessary to keep these channels opened. However, phosphatidic acid, PIP(2), or adenophostin could not trigger exocytosis by themselves, indicating that diacylglycerol must also activate another factor. We found that diacylglycerol and phorbol ester stimulate the accumulation of the GTP-bound form of Rab3A. Together our results indicate that diacylglycerol promotes acrosomal exocytosis by i) maintaining high levels of IP(3) - an effect that depends on a positive feedback loop leading to the production of PIP(2) - and ii) stimulating the activation of Rab3A, which in turn initiates a cascade of protein interactions leading to the assembly of SNARE complexes and membrane fusion.
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Affiliation(s)
- Cecilia I Lopez
- Instituto de Histología y Embriología, Universidad Nacional de Cuyo, Mendoza, Argentina
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20
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Rogasevskaia TP, Churchward MA, Coorssen JR. Anionic lipids in Ca(2+)-triggered fusion. Cell Calcium 2012; 52:259-69. [PMID: 22516687 DOI: 10.1016/j.ceca.2012.03.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Revised: 03/20/2012] [Accepted: 03/25/2012] [Indexed: 01/30/2023]
Abstract
Anionic lipids are native membrane components that have a profound impact on many cellular processes, including regulated exocytosis. Nonetheless, the full nature of their contribution to the fast, Ca(2+)-triggered fusion pathway remains poorly defined. Here we utilize the tightly coupled quantitative molecular and functional analyses enabled by the cortical vesicle model system to elucidate the roles of specific anionic lipids in the docking, priming and fusion steps of regulated release. Studies with cholesterol sulfate established that effectively localized anionic lipids could contribute to Ca(2+)-sensing and even bind Ca(2+) directly as effectors of necessary membrane rearrangements. The data thus support a role for phosphatidylserine in Ca(2+) sensing. In contrast, phosphatidylinositol would appear to serve regulatory functions in the physiological fusion machine, contributing to priming and thus the modulation and tuning of the fusion process. We note the complexities associated with establishing the specific roles of (anionic) lipids in the native fusion mechanism, including their localization and interactions with other critical components that also remain to be more clearly and quantitatively defined.
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Affiliation(s)
- Tatiana P Rogasevskaia
- Department of Chemical & Biological Sciences, Mount Royal University, 4825 Mount Royal Gate SW, Calgary, AB, T3E 6K6 Canada
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21
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Abstract
Phosphatidylinositol 4,5-bisphosphate (PIP(2)) is a membrane bound lipid molecule with capabilities to affect a wide array of signaling pathways to regulate very different cellular processes. PIP(2) is used as a precursor to generate the second messengers PIP(3), DAG and IP(3), indispensable molecules for signaling events generated by membrane receptors. However, PIP(2) can also directly regulate a vast array of proteins and is emerging as a crucial messenger with the potential to distinctly modulate biological processes critical for both normal and pathogenic cell physiology. PIP(2) directly associates with effector proteins via unique phosphoinositide binding domains, altering their localization and/or enzymatic activity. The spatial and temporal generation of PIP(2) synthesized by the phosphatidylinositol phosphate kinases (PIPKs) tightly regulates the activation of receptor signaling pathways, endocytosis and vesicle trafficking, cell polarity, focal adhesion dynamics, actin assembly and 3' mRNA processing. Here we discuss our current understanding of PIPKs in the regulation of cellular processes from the plasma membrane to the nucleus.
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22
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Larijani B, Poccia DL. Effects of Phosphoinositides and Their Derivatives on Membrane Morphology and Function. Curr Top Microbiol Immunol 2012; 362:99-110. [DOI: 10.1007/978-94-007-5025-8_5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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Zhendre V, Grélard A, Garnier-LHomme M, Buchoux S, Larijani B, Dufourc EJ. Key role of polyphosphoinositides in dynamics of fusogenic nuclear membrane vesicles. PLoS One 2011; 6:e23859. [PMID: 21931619 PMCID: PMC3169559 DOI: 10.1371/journal.pone.0023859] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Accepted: 07/26/2011] [Indexed: 11/18/2022] Open
Abstract
The role of phosphoinositides has been thoroughly described in many signalling and membrane trafficking events but their function as modulators of membrane structure and dynamics in membrane fusion has not been investigated. We have reconstructed models that mimic the composition of nuclear envelope precursor membranes with naturally elevated amounts of phosphoinositides. These fusogenic membranes (membrane vesicle 1(MV1) and nuclear envelope remnants (NER) are critical for the assembly of the nuclear envelope. Phospholipids, cholesterol, and polyphosphoinositides, with polyunsaturated fatty acid chains that were identified in the natural nuclear membranes by lipid mass spectrometry, have been used to reconstruct complex model membranes mimicking nuclear envelope precursor membranes. Structural and dynamic events occurring in the membrane core and at the membrane surface were monitored by solid-state deuterium and phosphorus NMR. "MV1-like" (PC∶PI∶PIP∶PIP(2), 30∶20∶18∶12, mol%) membranes that exhibited high levels of PtdIns, PtdInsP and PtdInsP(2) had an unusually fluid membrane core (up to 20% increase, compared to membranes with low amounts of phosphoinositides to mimic the endoplasmic reticulum). "NER-like" (PC∶CH∶PI∶PIP∶PIP(2), 28∶42∶16∶7∶7, mol%) membranes containing high amounts of both cholesterol and phosphoinositides exhibited liquid-ordered phase properties, but with markedly lower rigidity (10-15% decrease). Phosphoinositides are the first lipids reported to counterbalance the ordering effect of cholesterol. At the membrane surface, phosphoinositides control the orientation dynamics of other lipids in the model membranes, while remaining unchanged themselves. This is an important finding as it provides unprecedented mechanistic insight into the role of phosphoinositides in membrane dynamics. Biological implications of our findings and a model describing the roles of fusogenic membrane vesicles are proposed.
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Affiliation(s)
- Vanessa Zhendre
- Chemistry and Biology of Membranes and Nanoobjects (CBMN), UMR5248 - CNRS-Université Bordeaux-Institut Polytechnique de Bordeaux, Pessac, France
- Cell Biophysics Laboratory, Lincoln's Inn Fields Laboratories, Cancer Research UK, London, United Kingdom
| | - Axelle Grélard
- Chemistry and Biology of Membranes and Nanoobjects (CBMN), UMR5248 - CNRS-Université Bordeaux-Institut Polytechnique de Bordeaux, Pessac, France
| | - Marie Garnier-LHomme
- Chemistry and Biology of Membranes and Nanoobjects (CBMN), UMR5248 - CNRS-Université Bordeaux-Institut Polytechnique de Bordeaux, Pessac, France
- Cell Biophysics Laboratory, Lincoln's Inn Fields Laboratories, Cancer Research UK, London, United Kingdom
| | - Sébastien Buchoux
- UMR 6022 - Génie Enzymatique et Cellulaire, Université Picardie Jules Verne (UPJV), Amiens, France
| | - Banafshé Larijani
- Cell Biophysics Laboratory, Lincoln's Inn Fields Laboratories, Cancer Research UK, London, United Kingdom
| | - Erick J. Dufourc
- Chemistry and Biology of Membranes and Nanoobjects (CBMN), UMR5248 - CNRS-Université Bordeaux-Institut Polytechnique de Bordeaux, Pessac, France
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Rogasevskaia TP, Coorssen JR. A new approach to the molecular analysis of docking, priming, and regulated membrane fusion. J Chem Biol 2011; 4:117-36. [PMID: 22315653 DOI: 10.1007/s12154-011-0056-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Accepted: 12/23/2010] [Indexed: 12/12/2022] Open
Abstract
Studies using isolated sea urchin cortical vesicles have proven invaluable in dissecting mechanisms of Ca(2+)-triggered membrane fusion. However, only acute molecular manipulations are possible in vitro. Here, using selective pharmacological manipulations of sea urchin eggs ex vivo, we test the hypothesis that specific lipidic components of the membrane matrix selectively affect defined late stages of exocytosis, particularly the Ca(2+)-triggered steps of fast membrane fusion. Egg treatments with cholesterol-lowering drugs resulted in the inhibition of vesicle fusion. Exogenous cholesterol recovered fusion extent and efficiency in cholesterol-depleted membranes; α-tocopherol, a structurally dissimilar curvature analogue, selectively restored fusion extent. Inhibition of phospholipase C reduced vesicle phosphatidylethanolamine and suppressed both the extent and kinetics of fusion. Although phosphatidylinositol-3-kinase inhibition altered levels of polyphosphoinositide species and reduced all fusion parameters, sequestering polyphosphoinositides selectively inhibited fusion kinetics. Thus, cholesterol and phosphatidylethanolamine play direct roles in the fusion pathway, contributing negative curvature. Cholesterol also organizes the physiological fusion site, defining fusion efficiency. A selective influence of phosphatidylethanolamine on fusion kinetics sheds light on the local microdomain structure at the site of docking/fusion. Polyphosphoinositides have modulatory upstream roles in priming: alterations in specific polyphosphoinositides likely represent the terminal priming steps defining fully docked, release-ready vesicles. Thus, this pharmacological approach has the potential to be a robust high-throughput platform to identify molecular components of the physiological fusion machine critical to docking, priming, and triggered fusion.
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