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Caputo M, Ivanova D, Chasserot-Golaz S, Doussau F, Haeberlé AM, Royer C, Ozkan S, Ecard J, Vitale N, Cousin MA, Tóth P, Gasman S, Ory S. Phospholipid Scramblase 1 Controls Efficient Neurotransmission and Synaptic Vesicle Retrieval at Cerebellar Synapses. J Neurosci 2024; 44:e0042242024. [PMID: 38839301 PMCID: PMC11223464 DOI: 10.1523/jneurosci.0042-24.2024] [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: 01/08/2024] [Revised: 04/23/2024] [Accepted: 04/28/2024] [Indexed: 06/07/2024] Open
Abstract
Phospholipids (PLs) are asymmetrically distributed at the plasma membrane. This asymmetric lipid distribution is transiently altered during calcium-regulated exocytosis, but the impact of this transient remodeling on presynaptic function is currently unknown. As phospholipid scramblase 1 (PLSCR1) randomizes PL distribution between the two leaflets of the plasma membrane in response to calcium activation, we set out to determine its role in neurotransmission. We report here that PLSCR1 is expressed in cerebellar granule cells (GrCs) and that PLSCR1-dependent phosphatidylserine egress occurred at synapses in response to neuron stimulation. Synaptic transmission is impaired at GrC Plscr1 -/- synapses, and both PS egress and synaptic vesicle (SV) endocytosis are inhibited in Plscr1 -/- cultured neurons from male and female mice, demonstrating that PLSCR1 controls PL asymmetry remodeling and SV retrieval following neurotransmitter release. Altogether, our data reveal a novel key role for PLSCR1 in SV recycling and provide the first evidence that PL scrambling at the plasma membrane is a prerequisite for optimal presynaptic performance.
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Affiliation(s)
- Margherita Caputo
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg F-67000, France
| | - Daniela Ivanova
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom
- Muir Maxwell Epilepsy Centre, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom
| | - Sylvette Chasserot-Golaz
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg F-67000, France
| | - Frédéric Doussau
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg F-67000, France
| | - Anne-Marie Haeberlé
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg F-67000, France
| | - Cathy Royer
- Plateforme Imagerie In Vitro, Centre National de la Recherche Scientifique UPS3256, Strasbourg F-67000, France
| | - Sebahat Ozkan
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg F-67000, France
| | - Jason Ecard
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg F-67000, France
| | - Nicolas Vitale
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg F-67000, France
| | - Michael A Cousin
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom
- Muir Maxwell Epilepsy Centre, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom
- Simons Initiative for the Developing Brain, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom
| | - Petra Tóth
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg F-67000, France
| | - Stéphane Gasman
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg F-67000, France
| | - Stéphane Ory
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg F-67000, France
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2
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Petrov AM. Oxysterols in Central and Peripheral Synaptic Communication. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2024; 1440:91-123. [PMID: 38036877 DOI: 10.1007/978-3-031-43883-7_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2023]
Abstract
Cholesterol is a key molecule for synaptic transmission, and both central and peripheral synapses are cholesterol rich. During intense neuronal activity, a substantial portion of synaptic cholesterol can be oxidized by either enzymatic or non-enzymatic pathways to form oxysterols, which in turn modulate the activities of neurotransmitter receptors (e.g., NMDA and adrenergic receptors), signaling molecules (nitric oxide synthases, protein kinase C, liver X receptors), and synaptic vesicle cycling involved in neurotransmitters release. 24-Hydroxycholesterol, produced by neurons in the brain, could directly affect neighboring synapses and change neurotransmission. 27-Hydroxycholesterol, which can cross the blood-brain barrier, can alter both synaptogenesis and synaptic plasticity. Increased generation of 25-hydroxycholesterol by activated microglia and macrophages could link inflammatory processes to learning and neuronal regulation. Amyloids and oxidative stress can lead to an increase in the levels of ring-oxidized sterols and some of these oxysterols (4-cholesten-3-one, 5α-cholestan-3-one, 7β-hydroxycholesterol, 7-ketocholesterol) have a high potency to disturb or modulate neurotransmission at both the presynaptic and postsynaptic levels. Overall, oxysterols could be used as "molecular prototypes" for therapeutic approaches. Analogs of 24-hydroxycholesterol (SGE-301, SGE-550, SAGE718) can be used for correction of NMDA receptor hypofunction-related states, whereas inhibitors of cholesterol 24-hydroxylase, cholestane-3β,5α,6β-triol, and cholest-4-en-3-one oxime (olesoxime) can be utilized as potential anti-epileptic drugs and (or) protectors from excitotoxicity.
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Affiliation(s)
- Alexey M Petrov
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of RAS", Kazan, RT, Russia.
- Kazan State Medial University, Kazan, RT, Russia.
- Kazan Federal University, Kazan, RT, Russia.
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3
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Daly C, Plouffe B. Gα q signalling from endosomes: A new conundrum. Br J Pharmacol 2023. [PMID: 37740273 DOI: 10.1111/bph.16248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 08/08/2023] [Accepted: 09/13/2023] [Indexed: 09/24/2023] Open
Abstract
G-protein-coupled receptors (GPCRs) constitute the largest family of membrane receptors, and are involved in the transmission of a variety of extracellular stimuli such as hormones, neurotransmitters, light and odorants into intracellular responses. They regulate every aspect of physiology and, for this reason, about one third of all marketed drugs target these receptors. Classically, upon binding to their agonist, GPCRs are thought to activate G-proteins from the plasma membrane and to stop signalling by subsequent desensitisation and endocytosis. However, accumulating evidence indicates that, upon internalisation, some GPCRs can continue to activate G-proteins in endosomes. Importantly, this signalling from endomembranes mediates alternative cellular responses other than signalling at the plasma membrane. Endosomal G-protein signalling and its physiological relevance have been abundantly documented for Gαs - and Gαi -coupled receptors. Recently, some Gαq -coupled receptors have been reported to activate Gαq on endosomes and mediate important cellular processes. However, several questions relative to the series of cellular events required to translate endosomal Gαq activation into cellular responses remain unanswered and constitute a new conundrum. How are these responses in endosomes mediated in the quasi absence of the substrate for the canonical Gαq -activated effector? Is there another effector? Is there another substrate? If so, how does this alternative endosomal effector or substrate produce a downstream signal? This review aims to unravel and discuss these important questions, and proposes possible routes of investigation.
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Affiliation(s)
- Carole Daly
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast, UK
| | - Bianca Plouffe
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast, UK
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Hipkaeo W, Kondo H. Localization of phospholipid-related signal molecules in salivary glands of rodents: A review. J Oral Biosci 2023; 65:146-155. [PMID: 37061129 DOI: 10.1016/j.job.2023.04.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 04/08/2023] [Accepted: 04/10/2023] [Indexed: 04/17/2023]
Abstract
BACKGROUND In the 1950s, Hokin conducted initial studies on phosphoinositide turnover/cycle in salivary glandular cells. From these studies, the idea emerged that receptor-mediated changes in intramembranous levels of phosphoinositides represent an early step in the stimulus-response pathway. Based on this idea and the general view that knowledge of the exact localization of a given endogenous molecule in cells in situ is important for understanding its functional significance, we have reviewed available information about the localization of several representative phosphoinositide-signaling molecules in the salivary glands in situ in mice. HIGHLIGHT We focused on phosphatidylinositol 4-kinase, phosphatidylinositol 4 phosphate 5-kinase α, β, γ, phospholipase Cβ, muscarinic cholinoceptors 1 and 3, diacylglycerol kinase ζ, phospholipase D1 and 2, ADP-ribosylation factor 6 and its exchange factors for Arf6, and cannabinoid receptors. These molecules individually exhibit differential localization in a spatiotemporal manner in the exocrine glands, making it possible to deduce their functional significance, such as their involvement in secretion and cell differentiation. CONCLUSION Although phosphoinositide-signaling molecules whose in situ localization in glandular cells has been clarified are still limited, the obtained information on their localization suggests that their functional significance is more valuable in glandular ducts than in acini. It thus suggests the necessity of greater attention to the ducts in their physio-pharmacological analyses. The purpose of this review is to encourage more in situ localization studies of phosphoinositide-signaling molecules with an aim to further understand their possible involvement in the pathogenesis of salivary gland diseases.
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Affiliation(s)
- Wiphawi Hipkaeo
- Electron Microscopy Laboratory, Division of Anatomy, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.
| | - Hisatake Kondo
- Electron Microscopy Laboratory, Division of Anatomy, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand; Department of Anatomy, Graduate School of Medicine, Tohoku University, Sendai, JAPAN
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Hofbrucker-MacKenzie SA, Seemann E, Westermann M, Qualmann B, Kessels MM. Long-term depression in neurons involves temporal and ultra-structural dynamics of phosphatidylinositol-4,5-bisphosphate relying on PIP5K, PTEN and PLC. Commun Biol 2023; 6:366. [PMID: 37012315 PMCID: PMC10070498 DOI: 10.1038/s42003-023-04726-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Accepted: 03/17/2023] [Indexed: 04/05/2023] Open
Abstract
Synaptic plasticity involves proper establishment and rearrangement of structural and functional microdomains. Yet, visualization of the underlying lipid cues proved challenging. Applying a combination of rapid cryofixation, membrane freeze-fracturing, immunogold labeling and electron microscopy, we visualize and quantitatively determine the changes and the distribution of phosphatidylinositol-4,5-bisphosphate (PIP2) in the plasma membrane of dendritic spines and subareas thereof at ultra-high resolution. These efforts unravel distinct phases of PIP2 signals during induction of long-term depression (LTD). During the first minutes PIP2 rapidly increases in a PIP5K-dependent manner forming nanoclusters. PTEN contributes to a second phase of PIP2 accumulation. The transiently increased PIP2 signals are restricted to upper and middle spine heads. Finally, PLC-dependent PIP2 degradation provides timely termination of PIP2 cues during LTD induction. Together, this work unravels the spatial and temporal cues set by PIP2 during different phases after LTD induction and dissects the molecular mechanisms underlying the observed PIP2 dynamics.
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Affiliation(s)
- Sarah A Hofbrucker-MacKenzie
- Institute of Biochemistry I, Jena University Hospital - Friedrich Schiller University Jena, 07743, Jena, Germany
| | - Eric Seemann
- Institute of Biochemistry I, Jena University Hospital - Friedrich Schiller University Jena, 07743, Jena, Germany
| | - Martin Westermann
- Center for Electron Microscopy, Jena University Hospital - Friedrich Schiller University Jena, 07743, Jena, Germany
| | - Britta Qualmann
- Institute of Biochemistry I, Jena University Hospital - Friedrich Schiller University Jena, 07743, Jena, Germany.
| | - Michael M Kessels
- Institute of Biochemistry I, Jena University Hospital - Friedrich Schiller University Jena, 07743, Jena, Germany.
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Sánchez-Castillo C, Cuartero MI, Fernández-Rodrigo A, Briz V, López-García S, Jiménez-Sánchez R, López JA, Graupera M, Esteban JA. Functional specialization of different PI3K isoforms for the control of neuronal architecture, synaptic plasticity, and cognition. SCIENCE ADVANCES 2022; 8:eabq8109. [PMID: 36417513 PMCID: PMC9683729 DOI: 10.1126/sciadv.abq8109] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Accepted: 10/25/2022] [Indexed: 06/16/2023]
Abstract
Neuronal connectivity and activity-dependent synaptic plasticity are fundamental properties that support brain function and cognitive performance. Phosphatidylinositol 3-kinase (PI3K) intracellular signaling controls multiple mechanisms mediating neuronal growth, synaptic structure, and plasticity. However, it is still unclear how these pleiotropic functions are integrated at molecular and cellular levels. To address this issue, we used neuron-specific virally delivered Cre expression to delete either p110α or p110β (the two major catalytic isoforms of type I PI3K) from the hippocampus of adult mice. We found that dendritic and postsynaptic structures are almost exclusively supported by p110α activity, whereas p110β controls neurotransmitter release and metabotropic glutamate receptor-dependent long-term depression at the presynaptic terminal. In addition to these separate functions, p110α and p110β jointly contribute to N-methyl-d-aspartate receptor-dependent postsynaptic long-term potentiation. This molecular and functional specialization is reflected in different proteomes controlled by each isoform and in distinct behavioral alterations for learning/memory and sociability in mice lacking p110α or p110β.
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Affiliation(s)
- Carla Sánchez-Castillo
- Department of Molecular Neuropathology, Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Madrid, Spain
| | - María I. Cuartero
- Department of Molecular Neuropathology, Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Madrid, Spain
| | - Alba Fernández-Rodrigo
- Department of Molecular Neuropathology, Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Madrid, Spain
| | - Víctor Briz
- Department of Molecular Neuropathology, Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Madrid, Spain
| | - Sergio López-García
- Department of Molecular Neuropathology, Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Madrid, Spain
| | - Raquel Jiménez-Sánchez
- Department of Molecular Neuropathology, Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Madrid, Spain
| | - Juan A. López
- Proteomics Unit, Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Instituto de Salud Carlos III, Madrid, Spain
| | - Mariona Graupera
- Endothelial Pathobiology and Microenviroment Group, Josep Carreras Leukaemia Research Institute (IJC), 08916 Badalona, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Cáncer (CIBERONC), Instituto de Salud Carlos III, Madrid, Spain
| | - José A. Esteban
- Department of Molecular Neuropathology, Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Madrid, Spain
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7
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Bending over backwards: BAR proteins and the actin cytoskeleton in mammalian receptor-mediated endocytosis. Eur J Cell Biol 2022; 101:151257. [PMID: 35863103 DOI: 10.1016/j.ejcb.2022.151257] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Revised: 07/13/2022] [Accepted: 07/14/2022] [Indexed: 11/21/2022] Open
Abstract
The role of the actin cytoskeleton during receptor-mediated endocytosis (RME) has been well characterized in yeast for many years. Only more recently has the interplay between the actin cytoskeleton and RME been extensively explored in mammalian cells. These studies have revealed the central roles of BAR proteins in RME, and have demonstrated significant roles of BAR proteins in linking the actin cytoskeleton to this cellular process. The actin cytoskeleton generates and transmits mechanical force to promote the extension of receptor-bound endocytic vesicles into the cell. Many adaptor proteins link and regulate the actin cytoskeleton at the sites of endocytosis. This review will cover key effectors, adaptors and signalling molecules that help to facilitate the invagination of the cell membrane during receptor-mediated endocytosis, including recent insights gained on the roles of BAR proteins. The final part of this review will explore associations of alterations to genes encoding BAR proteins with cancer.
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8
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Liu GT, Kochlamazashvili G, Puchkov D, Müller R, Schultz C, Mackintosh AI, Vollweiter D, Haucke V, Soykan T. Endosomal phosphatidylinositol 3-phosphate controls synaptic vesicle cycling and neurotransmission. EMBO J 2022; 41:e109352. [PMID: 35318705 PMCID: PMC9058544 DOI: 10.15252/embj.2021109352] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 02/24/2022] [Accepted: 03/01/2022] [Indexed: 11/09/2022] Open
Abstract
Neural circuit function requires mechanisms for controlling neurotransmitter release and the activity of neuronal networks, including modulation by synaptic contacts, synaptic plasticity, and homeostatic scaling. However, how neurons intrinsically monitor and feedback control presynaptic neurotransmitter release and synaptic vesicle (SV) recycling to restrict neuronal network activity remains poorly understood at the molecular level. Here, we investigated the reciprocal interplay between neuronal endosomes, organelles of central importance for the function of synapses, and synaptic activity. We show that elevated neuronal activity represses the synthesis of endosomal lipid phosphatidylinositol 3-phosphate [PI(3)P] by the lipid kinase VPS34. Neuronal activity in turn is regulated by endosomal PI(3)P, the depletion of which reduces neurotransmission as a consequence of perturbed SV endocytosis. We find that this mechanism involves Calpain 2-mediated hyperactivation of Cdk5 downstream of receptor- and activity-dependent calcium influx. Our results unravel an unexpected function for PI(3)P-containing neuronal endosomes in the control of presynaptic vesicle cycling and neurotransmission, which may explain the involvement of the PI(3)P-producing VPS34 kinase in neurological disease and neurodegeneration.
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Affiliation(s)
- Guan-Ting Liu
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | | | - Dmytro Puchkov
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Rainer Müller
- European Molecular Biology Laboratory (EMBL), Cell Biology and Biophysics Unit, Heidelberg, Germany
| | - Carsten Schultz
- European Molecular Biology Laboratory (EMBL), Cell Biology and Biophysics Unit, Heidelberg, Germany.,Department of Chemical Physiology & Biochemistry, Oregon Health & Science University (OHSU), Portland, OR, USA
| | - Albert I Mackintosh
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Dennis Vollweiter
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Volker Haucke
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany.,Faculty of Biology, Chemistry, Pharmacy, Freie Universität Berlin, Berlin, Germany.,NeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Tolga Soykan
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
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9
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Galkina OV, Vetrovoy OV, Eschenko ND. The Role of Lipids in Implementing Specific Functions in the Central Nervous System. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2021. [DOI: 10.1134/s1068162021050253] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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10
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Tolstykh GP, Valdez CM, Montgomery ND, Cantu JC, Sedelnikova A, Ibey BL. Intrinsic properties of primary hippocampal neurons contribute to PIP 2 depletion during nsEP-induced physiological response. Bioelectrochemistry 2021; 142:107930. [PMID: 34450563 DOI: 10.1016/j.bioelechem.2021.107930] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 08/03/2021] [Accepted: 08/10/2021] [Indexed: 12/23/2022]
Abstract
High-energy, short-duration electric pulses (EPs) are known to be effective in neuromodulation, but the biological mechanisms underlying this effect remain unclear. Recently, we discovered that nanosecond electric pulses (nsEPs) could initiate the phosphatidylinositol4,5-bisphosphate (PIP2) depletion in non-excitable cells identical to agonist-induced activation of the Gq11 coupled receptors. PIP2 is the precursor for multiple intracellular second messengers critically involved in the regulation of intracellular Ca2+ homeostasis and plasma membrane (PM) ion channels responsible for the control of neuronal excitability. In this paper we demonstrate a novel finding that five day in vitro (DIV5) primary hippocampal neurons (PHNs) undergo significantly higher PIP2 depletion after 7.5 kV/cm 600 ns EP exposure than DIV1 PHNs and day 1-5 (D1-D5) non-excitable Chinese hamster ovarian cells with muscarinic receptor 1 (CHO-hM1). Despite the age of development, the stronger 15 kV/cm 600 ns or longer 7.5 kV/cm 12 µs EP initiated profound PIP2 depletion in all cells studied, outlining damage of the cellular PM and electroporation. Therefore, the intrinsic properties of PHNs in concert with nanoporation explain the stronger neuronal response to nsEP at lower intensity exposures. PIP2 reduction in neurons could be a primary biological mechanism responsible for the stimulation or inhibition of neuronal tissues.
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Affiliation(s)
- Gleb P Tolstykh
- General Dynamics Information Technology, 4141 Petroleum Road, JBSA Fort Sam Houston, TX 78234, USA.
| | - Christopher M Valdez
- Air Force Research Laboratory, 711th Human Performance Wing, Airman Systems Directorate, Bioeffects Division, Radio Frequency Bioeffects Branch, 4141 Petroleum Road, JBSA Fort Sam Houston, TX 78234, USA
| | - Noel D Montgomery
- Air Force Research Laboratory, 711th Human Performance Wing, Airman Systems Directorate, Bioeffects Division, Radio Frequency Bioeffects Branch, 4141 Petroleum Road, JBSA Fort Sam Houston, TX 78234, USA
| | - Jody C Cantu
- General Dynamics Information Technology, 4141 Petroleum Road, JBSA Fort Sam Houston, TX 78234, USA
| | | | - Bennett L Ibey
- Air Force Research Laboratory, 711th Human Performance Wing, Airman Systems Directorate, Bioeffects Division, Radio Frequency Bioeffects Branch, 4141 Petroleum Road, JBSA Fort Sam Houston, TX 78234, USA
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11
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Nitric oxide resets kisspeptin-excited GnRH neurons via PIP2 replenishment. Proc Natl Acad Sci U S A 2021; 118:2012339118. [PMID: 33443156 DOI: 10.1073/pnas.2012339118] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Fertility relies upon pulsatile release of gonadotropin-releasing hormone (GnRH) that drives pulsatile luteinizing hormone secretion. Kisspeptin (KP) neurons in the arcuate nucleus are at the center of the GnRH pulse generation and the steroid feedback control of GnRH secretion. However, KP evokes a long-lasting response in GnRH neurons that is hard to reconcile with periodic GnRH activity required to drive GnRH pulses. Using calcium imaging, we show that 1) the tetrodotoxin-insensitive calcium response evoked by KP relies upon the ongoing activity of canonical transient receptor potential channels maintaining voltage-gated calcium channels in an activated state, 2) the duration of the calcium response is determined by the rate of resynthesis of phosphatidylinositol 4,5-bisphosphate (PIP2), and 3) nitric oxide terminates the calcium response by facilitating the resynthesis of PIP2 via the canonical pathway guanylyl cyclase/3',5'-cyclic guanosine monophosphate/protein kinase G. In addition, our data indicate that exposure to nitric oxide after KP facilitates the calcium response to a subsequent KP application. This effect was replicated using electrophysiology on GnRH neurons in acute brain slices. The interplay between KP and nitric oxide signaling provides a mechanism for modulation of the refractory period of GnRH neurons after KP exposure and places nitric oxide as an important component for tonic GnRH neuronal pulses.
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12
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Zou L, Zhang X, Xiong M, Meng L, Tian Y, Pan L, Yuan X, Chen G, Wang Z, Bu L, Yao Z, Zhang Z, Ye K, Zhang Z. Asparagine endopeptidase cleaves synaptojanin 1 and triggers synaptic dysfunction in Parkinson's disease. Neurobiol Dis 2021; 154:105326. [PMID: 33677035 DOI: 10.1016/j.nbd.2021.105326] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 02/02/2021] [Accepted: 03/02/2021] [Indexed: 10/22/2022] Open
Abstract
Parkinson's disease (PD) is one of the most common neurodegenerative diseases, which is characterized by the loss of dopaminergic neurons in the nigrostriatal pathway. Synaptic dysfunction impairs dopamine turnover and contributes to the degeneration of dopaminergic neurons. However, the molecular mechanisms underlying synaptic dysfunction and dopaminergic neuronal vulnerability in PD are not clear. Here, we report that synaptojanin 1 (SYNJ1), a polyphosphoinositide phosphatase concentrated at nerve terminals, is a substrate of a cysteine proteinase, asparagine endopeptidase (AEP). SYNJ1 is cleaved by the cysteine proteinase AEP at N599 in the brains of PD patients. AEP-mediated cleavage of SYNJ1 disrupts neuronal phosphoinositide homeostasis and causes synaptic dysfunction. Overexpression of the AEP-generated fragments of SYNJ1 triggers synaptic dysfunction and the degeneration of dopaminergic neurons, inducing motor defects in the α-synuclein transgenic mice. Blockage of AEP-mediated cleavage of SYJN1 alleviates the pathological and behavioral defects in a mouse model of PD. Our results demonstrate that the fragmentation of SYNJ1 by AEP mediates synaptic dysfunction and dopaminergic neuronal degeneration in PD.
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Affiliation(s)
- Li Zou
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Xingyu Zhang
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Min Xiong
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Lanxia Meng
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Ye Tian
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Lina Pan
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Xin Yuan
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Guiqin Chen
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China; Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Zhihao Wang
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Lihong Bu
- PET-CT/MRI Center, Faculty of Radiology and Nuclear Medicine, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Zhaohui Yao
- Department of Geriatrics, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Zhaohui Zhang
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Keqiang Ye
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Zhentao Zhang
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China.
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13
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Bradberry MM, Courtney NA, Dominguez MJ, Lofquist SM, Knox AT, Sutton RB, Chapman ER. Molecular Basis for Synaptotagmin-1-Associated Neurodevelopmental Disorder. Neuron 2020; 107:52-64.e7. [PMID: 32362337 DOI: 10.1016/j.neuron.2020.04.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 03/09/2020] [Accepted: 04/01/2020] [Indexed: 12/13/2022]
Abstract
At neuronal synapses, synaptotagmin-1 (syt1) acts as a Ca2+ sensor that synchronizes neurotransmitter release with Ca2+ influx during action potential firing. Heterozygous missense mutations in syt1 have recently been associated with a severe but heterogeneous developmental syndrome, termed syt1-associated neurodevelopmental disorder. Well-defined pathogenic mechanisms, and the basis for phenotypic heterogeneity in this disorder, remain unknown. Here, we report the clinical, physiological, and biophysical characterization of three syt1 mutations from human patients. Synaptic transmission was impaired in neurons expressing mutant variants, which demonstrated potent, graded dominant-negative effects. Biophysical interrogation of the mutant variants revealed novel mechanistic features concerning the cooperative action, and functional specialization, of the tandem Ca2+-sensing domains of syt1. These mechanistic studies led to the discovery that a clinically approved K+ channel antagonist is able to rescue the dominant-negative heterozygous phenotype. Our results establish a molecular cause, basis for phenotypic heterogeneity, and potential treatment approach for syt1-associated neurodevelopmental disorder.
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Affiliation(s)
- Mazdak M Bradberry
- Howard Hughes Medical Institute and Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA; Medical Scientist Training Program, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA
| | - Nicholas A Courtney
- Howard Hughes Medical Institute and Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA
| | - Matthew J Dominguez
- Department of Cell Physiology and Molecular Biophysics and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Sydney M Lofquist
- Howard Hughes Medical Institute and Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA
| | - Andrew T Knox
- Department of Neurology, Section of Pediatric Neurology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA
| | - R Bryan Sutton
- Department of Cell Physiology and Molecular Biophysics and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Edwin R Chapman
- Howard Hughes Medical Institute and Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA.
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Bradberry MM, Bao H, Lou X, Chapman ER. Phosphatidylinositol 4,5-bisphosphate drives Ca 2+-independent membrane penetration by the tandem C2 domain proteins synaptotagmin-1 and Doc2β. J Biol Chem 2019; 294:10942-10953. [PMID: 31147445 DOI: 10.1074/jbc.ra119.007929] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 05/28/2019] [Indexed: 12/14/2022] Open
Abstract
Exocytosis mediates the release of neurotransmitters and hormones from neurons and neuroendocrine cells. Tandem C2 domain proteins in the synaptotagmin (syt) and double C2 domain (Doc2) families regulate exocytotic membrane fusion via direct interactions with Ca2+ and phospholipid bilayers. Syt1 is a fast-acting, low-affinity Ca2+ sensor that penetrates membranes upon binding Ca2+ to trigger synchronous vesicle fusion. The closely related Doc2β is a slow-acting, high-affinity Ca2+ sensor that triggers spontaneous and asynchronous vesicle fusion, but whether it also penetrates membranes is unknown. Both syt1 and Doc2β bind the dynamically regulated plasma membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2), but it is unclear whether PIP2 serves only as a membrane contact or enables specialized membrane-binding modes by these Ca2+ sensors. Furthermore, it has been shown that PIP2 uncaging can trigger rapid, syt1-dependent exocytosis in the absence of Ca2+ influx, suggesting that current models for the action of these Ca2+ sensors are incomplete. Here, using a series of steady-state and time-resolved fluorescence measurements, we show that Doc2β, like syt1, penetrates membranes in a Ca2+-dependent manner. Unexpectedly, we observed that PIP2 can drive membrane penetration by both syt1 and Doc2β in the absence of Ca2+, providing a plausible mechanism for Ca2+-independent, PIP2-dependent exocytosis. Quantitative measurements of penetration depth revealed that, in the presence of Ca2+, PIP2 drives Doc2β, but not syt1, substantially deeper into the membrane, defining a biophysical regulatory mechanism specific to this high-affinity Ca2+ sensor. Our results provide evidence of a novel role for PIP2 in regulating, and under some circumstances triggering, exocytosis.
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Affiliation(s)
- Mazdak M Bradberry
- Howard Hughes Medical Institute and the Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53706 and; Medical Scientist Training Program, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53705
| | - Huan Bao
- Howard Hughes Medical Institute and the Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53706 and
| | - Xiaochu Lou
- Howard Hughes Medical Institute and the Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53706 and
| | - Edwin R Chapman
- Howard Hughes Medical Institute and the Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53706 and.
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15
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Khrongyut S, Rawangwong A, Pidsaya A, Sakagami H, Kondo H, Hipkaeo W. Localization of phosphatidylinositol 4-phosphate 5-kinase (PIP5K) α, β, γ in the three major salivary glands in situ of mice and their response to β-adrenoceptor stimulation. J Anat 2019; 234:502-514. [PMID: 30734271 DOI: 10.1111/joa.12944] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/07/2019] [Indexed: 12/15/2022] Open
Abstract
Phosphatidylinositol 4-phosphate 5-kinase (PIP5K), which is composed of three isozymes (α, β and γ), catalyzes the production of phosphatidylinositol bisphosphate (PIP2). This phospholipid functions in membrane trafficking, as an anchor for actin cytoskeletons and as a regulator of intramembranous channels/transporters. It is also a precursor of such second messengers as diacylglycerol, inositol triphosphate and phosphatidylinositol (3,4,5)-triphosphate. In the present study, the expression and localization of endogenous PIP5Ks were examined in the three major salivary glands of young adult mice in situ. In western blotting of normal control glands, immunoreactive bands for individual PIP5Ks were detectable, with the highest density in the parotid gland and the weakest density in the submandibular gland. In immuno-light microscopy under non-stimulated condition, weak immunoreactivity for PIP5Kα was confined to the apical plasmalemma in parotid, but not sublingual or submandibular, acinar cells. Immunoreactivity for PIP5Kβ was weak to moderate and confined to ductal cells but not acinar cells, whereas that for PIP5Kγ was selectively and intensely detected in myoepithelial cells but not acinar cells, and it was weak in ductal cells in the three glands. In western blot of the parotid gland stimulated by isoproterenol, a β-adrenoceptor agonist, no changes were seen in the intensity of immunoreactive bands for any of the PIP5Ks. In contrast, in immuno-light microscopy, the apical immunoreactivity for PIP5Kα in parotid acinar cells was transiently and distinctly increased after the stimulation. The increased immunoreactivity was ultrastructurally localized on most apical microvilli and along contiguous plasma membrane, where membranous invaginations of various shapes and small vesicles were frequently found. It was thus suggested that PIP5Kα is involved in post-exocytotic membrane dynamics via microvillous membranes. The present finding further suggests that each of the three isoforms of PIP5K functions through its product PIP2 discretely in different cells of the glands to regulate saliva secretion.
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Affiliation(s)
- Suthankamon Khrongyut
- Faculty of Medicine, Department of Anatomy, Electron Microscopy Unit, Khon Kaen University, Khon Kaen, Thailand
| | - Atsara Rawangwong
- Faculty of Medicine, Department of Anatomy, Electron Microscopy Unit, Khon Kaen University, Khon Kaen, Thailand
| | - Atthapon Pidsaya
- Faculty of Medicine, Department of Anatomy, Electron Microscopy Unit, Khon Kaen University, Khon Kaen, Thailand
| | - Hiroyuki Sakagami
- Department of Anatomy, School of Medicine, Kitasato University, Sagamihara, Japan
| | - Hisatake Kondo
- Faculty of Medicine, Department of Anatomy, Electron Microscopy Unit, Khon Kaen University, Khon Kaen, Thailand.,Department of Organ Anatomy, Graduate School of Medicine, Tohoku University, Sendai, Japan
| | - Wiphawi Hipkaeo
- Faculty of Medicine, Department of Anatomy, Electron Microscopy Unit, Khon Kaen University, Khon Kaen, Thailand
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Hackelberg S, Oliver D. Metabotropic Acetylcholine and Glutamate Receptors Mediate PI(4,5)P 2 Depletion and Oscillations in Hippocampal CA1 Pyramidal Neurons in situ. Sci Rep 2018; 8:12987. [PMID: 30154490 PMCID: PMC6113233 DOI: 10.1038/s41598-018-31322-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Accepted: 08/17/2018] [Indexed: 01/24/2023] Open
Abstract
The sensitivity of many ion channels to phosphatidylinositol-4,5-bisphosphate (PIP2) levels in the cell membrane suggests that PIP2 fluctuations are important and general signals modulating neuronal excitability. Yet the PIP2 dynamics of central neurons in their native environment remained largely unexplored. Here, we examined the behavior of PIP2 concentrations in response to activation of Gq-coupled neurotransmitter receptors in rat CA1 hippocampal neurons in situ in acute brain slices. Confocal microscopy of the PIP2-selective molecular sensors tubbyCT-GFP and PLCδ1-PH-GFP showed that pharmacological activation of muscarinic acetylcholine (mAChR) or group I metabotropic glutamate (mGluRI) receptors induces transient depletion of PIP2 in the soma as well as in the dendritic tree. The observed PIP2 dynamics were receptor-specific, with mAChR activation inducing stronger PIP2 depletion than mGluRI, whereas agonists of other Gαq-coupled receptors expressed in CA1 neurons did not induce measureable PIP2 depletion. Furthermore, the data show for the first time neuronal receptor-induced oscillations of membrane PIP2 concentrations. Oscillatory behavior indicated that neurons can rapidly restore PIP2 levels during persistent activation of Gq and PLC. Electrophysiological responses to receptor activation resembled PIP2 dynamics in terms of time course and receptor specificity. Our findings support a physiological function of PIP2 in regulating electrical activity.
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Affiliation(s)
- Sandra Hackelberg
- Institute of Physiology and Pathophysiology, Philipps University, 35037, Marburg, Germany
- The Ken and Ruth Davee Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Dominik Oliver
- Institute of Physiology and Pathophysiology, Philipps University, 35037, Marburg, Germany.
- DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, GRK 2213, Philipps University, Marburg, Germany.
- Center for Mind, Brain and Behavior (CMBB), Marburg and Giessen, Germany.
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17
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Boras M, Volmering S, Bokemeyer A, Rossaint J, Block H, Bardel B, Van Marck V, Heitplatz B, Kliche S, Reinhold A, Lowell C, Zarbock A. Skap2 is required for β 2 integrin-mediated neutrophil recruitment and functions. J Exp Med 2017; 214:851-874. [PMID: 28183734 PMCID: PMC5339670 DOI: 10.1084/jem.20160647] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 11/03/2016] [Accepted: 12/27/2016] [Indexed: 01/13/2023] Open
Abstract
Integrin activation is required for neutrophil functions. Impaired integrin activation on neutrophils is the hallmark of leukocyte adhesion deficiency (LAD) syndrome in humans, characterized by impaired leukocyte recruitment and recurrent infections. The Src kinase-associated phosphoprotein 2 (Skap2) is involved in integrin functions in different leukocyte subtypes. However, the role of Skap2 in β2 integrin activation and neutrophil recruitment is unknown. In this study, we demonstrate the crucial role of Skap2 in regulating actin polymerization and binding of talin-1 and kindlin-3 to the β2 integrin cytoplasmic domain, thereby being indispensable for β2 integrin activation and neutrophil recruitment. The direct interaction of Skap2 with the Wiskott-Aldrich syndrome protein via its SH3 domain is critical for integrin activation and neutrophil recruitment in vivo. Furthermore, Skap2 regulates integrin-mediated outside-in signaling events and neutrophil functions. Thus, Skap2 is essential to activate the β2 integrins, and loss of Skap2 function is sufficient to cause a LAD-like phenotype in mice.
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Affiliation(s)
- Mark Boras
- Department of Anesthesiology, Intensive Care, and Pain Medicine, University of Münster, 48149 Münster, Germany
| | - Stephanie Volmering
- Department of Anesthesiology, Intensive Care, and Pain Medicine, University of Münster, 48149 Münster, Germany
| | - Arne Bokemeyer
- Department of Anesthesiology, Intensive Care, and Pain Medicine, University of Münster, 48149 Münster, Germany
| | - Jan Rossaint
- Department of Anesthesiology, Intensive Care, and Pain Medicine, University of Münster, 48149 Münster, Germany
| | - Helena Block
- Department of Anesthesiology, Intensive Care, and Pain Medicine, University of Münster, 48149 Münster, Germany
| | - Bernadette Bardel
- Department of Anesthesiology, Intensive Care, and Pain Medicine, University of Münster, 48149 Münster, Germany
| | - Veerle Van Marck
- Gerhard-Domagk-Institute of Pathology, University Hospital Münster, University of Münster, 48149 Münster, Germany
| | - Barbara Heitplatz
- Gerhard-Domagk-Institute of Pathology, University Hospital Münster, University of Münster, 48149 Münster, Germany
| | - Stefanie Kliche
- Institute of Molecular and Clinical Immunology, Otto-von-Guericke University Magdeburg, 39106 Magdeburg, Germany
| | - Annegret Reinhold
- Institute of Molecular and Clinical Immunology, Otto-von-Guericke University Magdeburg, 39106 Magdeburg, Germany
| | - Clifford Lowell
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94143
- The Program in Immunology, University of California, San Francisco, San Francisco, CA 94143
| | - Alexander Zarbock
- Department of Anesthesiology, Intensive Care, and Pain Medicine, University of Münster, 48149 Münster, Germany
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18
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Blazek AD, Paleo BJ, Weisleder N. Plasma Membrane Repair: A Central Process for Maintaining Cellular Homeostasis. Physiology (Bethesda) 2016; 30:438-48. [PMID: 26525343 DOI: 10.1152/physiol.00019.2015] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Plasma membrane repair is a conserved cellular response mediating active resealing of membrane disruptions to maintain homeostasis and prevent cell death and progression of multiple diseases. Cell membrane repair repurposes mechanisms from various cellular functions, including vesicle trafficking, exocytosis, and endocytosis, to mend the broken membrane. Recent studies increased our understanding of membrane repair by establishing the molecular machinery contributing to membrane resealing. Here, we review some of the key proteins linked to cell membrane repair.
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Affiliation(s)
- Alisa D Blazek
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Brian J Paleo
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Noah Weisleder
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio
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19
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Raben DM, Barber CN. Phosphatidic acid and neurotransmission. Adv Biol Regul 2016; 63:15-21. [PMID: 27671966 DOI: 10.1016/j.jbior.2016.09.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 09/15/2016] [Accepted: 09/19/2016] [Indexed: 12/31/2022]
Abstract
Lipids play a vital role in the health and functioning of neurons and interest in the physiological role of neuronal lipids is certainly increasing. One neuronal function in which neuronal lipids appears to play key roles in neurotransmission. Our understanding of the role of lipids in the synaptic vesicle cycle and neurotransmitter release is becoming increasingly more important. Much of the initial research in this area has highlighted the major roles played by the phosphoinositides (PtdIns), diacylglycerol (DAG), and phosphatidic acid (PtdOH). Of these, PtdOH has not received as much attention as the other lipids although its role and metabolism appears to be extremely important. This lipid has been shown to play a role in modulating both exocytosis and endocytosis although its precise role in either process is not well defined. The currently evidence suggest this lipid likely participates in key processes by altering membrane architecture necessary for membrane fusion, mediating the penetration of membrane proteins, serving as a precursor for other important SV cycling lipids, or activating essential enzymes. In this review, we address the sources of PtdOH, the enzymes involved in its production, the regulation of these enzymes, and its potential roles in neurotransmission in the central nervous system.
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Affiliation(s)
- Daniel M Raben
- The Department of Biological Chemistry, The Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA.
| | - Casey N Barber
- The Department of Biological Chemistry, The Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
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20
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Abstract
UNLABELLED In neurons, loss of plasma membrane phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] leads to a decrease in exocytosis and changes in electrical excitability. Restoration of PI(4,5)P2 levels after phospholipase C activation is therefore essential for a return to basal neuronal activity. However, the dynamics of phosphoinositide metabolism have not been analyzed in neurons. We measured dynamic changes of PI(4,5)P2, phosphatidylinositol 4-phosphate, diacylglycerol, inositol 1,4,5-trisphosphate, and Ca(2+) upon muscarinic stimulation in sympathetic neurons from adult male Sprague-Dawley rats with electrophysiological and optical approaches. We used this kinetic information to develop a quantitative description of neuronal phosphoinositide metabolism. The measurements and analysis show and explain faster synthesis of PI(4,5)P2 in sympathetic neurons than in electrically nonexcitable tsA201 cells. They can be used to understand dynamic effects of receptor-mediated phospholipase C activation on excitability and other PI(4,5)P2-dependent processes in neurons. SIGNIFICANCE STATEMENT Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] is a minor phospholipid in the cytoplasmic leaflet of the plasma membrane. Depletion of PI(4,5)P2 via phospholipase C-mediated hydrolysis leads to a decrease in exocytosis and alters electrical excitability in neurons. Restoration of PI(4,5)P2 is essential for a return to basal neuronal activity. However, the dynamics of phosphoinositide metabolism have not been analyzed in neurons. We studied the dynamics of phosphoinositide metabolism in sympathetic neurons upon muscarinic stimulation and used the kinetic information to develop a quantitative description of neuronal phosphoinositide metabolism. The measurements and analysis show a several-fold faster synthesis of PI(4,5)P2 in sympathetic neurons than in an electrically nonexcitable cell line, and provide a framework for future studies of PI(4,5)P2-dependent processes in neurons.
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21
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Tadokoro S, Inoh Y, Nakanishi M, Hirashima N. Effects of PIP2 on membrane fusion between mast cell SNARE liposomes mediated by synaptotagmin 2. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:2290-4. [PMID: 26095717 DOI: 10.1016/j.bbamem.2015.06.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Revised: 06/13/2015] [Accepted: 06/15/2015] [Indexed: 12/30/2022]
Abstract
Recent studies have revealed that SNARE proteins are involved in exocytotic release in mast cells. Previously, we reported that mast cell SNARE proteins induce membrane fusion between liposomes. Moreover, we found that synaptotagmin 2, a candidate Ca2+ sensor for mast cell exocytosis, enhanced SNARE-mediated membrane fusion via Ca2+ and phosphatidylserine. Phosphatidylinositol 4,5-bisphosphate (PIP2) is an acidic phospholipid like phosphatidylserine. In the present study, we investigated whether PIP2 is involved in the enhancement effect of synaptotagmin 2 on SNARE-mediated membrane fusion. PIP2 did not show any significant effect on SNARE-mediated membrane fusion by itself. In the presence of Ca2+, synaptotagmin 2 enhanced SNARE-mediated membrane fusion between liposomes containing PIP2. However, even in the presence of Ca2+, when we used 100% PC liposomes, synaptotagmin 2 did not show any significant effect on SNARE-mediated membrane fusion. These results indicated that PIP2 is involved in the enhancement effect of synaptotagmin 2 on membrane fusion between liposomes containing mast cell SNARE proteins.
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Affiliation(s)
- Satoshi Tadokoro
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya 467-8603, Japan
| | - Yoshikazu Inoh
- School of Pharmacy, Aichi Gakuin University, 1-100 Kusumoto-cho, Chikusa-ku, Nagoya 464-8650, Japan
| | - Mamoru Nakanishi
- School of Pharmacy, Aichi Gakuin University, 1-100 Kusumoto-cho, Chikusa-ku, Nagoya 464-8650, Japan
| | - Naohide Hirashima
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya 467-8603, Japan.
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22
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Mori MX, Inoue R. New experimental trends for phosphoinositides research on ion transporter/channel regulation. J Pharmacol Sci 2014; 126:186-97. [PMID: 25367262 DOI: 10.1254/jphs.14r14cp] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Phosphoinositides(4,5)-bisphosphates [PI(4,5)P2] critically controls membrane excitability, the disruption of which leads to pathophysiological states. PI(4,5)P2 plays a primary role in regulating the conduction and gating properties of ion channels/transporters, through electrostatic and hydrophobic interactions that allow direct associations. In recent years, the development of many molecular tools have brought deep insights into the mechanisms underlying PI(4,5)P2-mediated regulation. This review summarizes the methods currently available to manipulate the cell membrane PI(4,5)P2 level including pharmacological interventions as well as newly designed molecular tools. We concisely introduce materials and experimental designs suitable for the study of PI(4,5)P2-mediated regulation of ion-conducting molecules, in order to assist researchers who are interested in this area. It is our further hope that the knowledge introduced in this review will help to promote our understanding about the pathology of diseases such as cardiac arrhythmias, bipolar disorders, and Alzheimer's disease which are somehow associated with a disruption of PI(4,5)P2 metabolism.
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Affiliation(s)
- Masayuki X Mori
- Department of Synthetic Chemistry and Biological Chemistry, School of Engineering, Kyoto University, Japan
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23
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Capsaicin modulates acetylcholine release at the myoneural junction. Eur J Pharmacol 2014; 744:211-9. [PMID: 25446918 DOI: 10.1016/j.ejphar.2014.09.044] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2014] [Revised: 09/25/2014] [Accepted: 09/25/2014] [Indexed: 11/20/2022]
Abstract
Transient receptor potential (TRP) proteins are non-selective cation channel proteins that are expressed throughout the body. Previous studies demonstrated the expression of TRP Vanilloid 1 (TRPV1), capsaicin (CAP) receptor, in sensory neurons. Recently, we reported TRPV1 expression in mouse motor nerve terminals [MNTs; (Thyagarajan et al., 2009)], where we observed that CAP protected MNTs from botulinum neurotoxin A (BoNT/A). Phrenic nerve diaphragm nerve muscle preparations (NMP) isolated from isoflurane anesthetized adult mice were analyzed for twitch tension, spontaneous (mEPCs) and nerve stimulus evoked (EPCs) acetylcholine release. When acutely applied to isolated NMP, CAP produced a concentration-dependent decline of twitch tension and produced a significant decline in the amplitude of EPCs and quantal content without any effect on the mEPCs. The suppression of nerve stimulus evoked acetylcholine release by CAP was antagonized by capsazepine (CPZ), a TRPV1 antagonist. CAP did not suppress phrenic nerve stimulus evoked acetylcholine release in TRPV1 knockout mice. Also, CAP treatment, in vitro, interfered with the localization of adapter protein 2 in cholinergic Neuro 2a cells. Wortmannin, (WMN; non-selective phosphoinositol kinase inhibitor), mimicked the effects of CAP by inhibiting the acetylcholine exocytosis. Our data suggest that TRPV1 proteins expressed at the MNT are coupled to the exo-endocytic mechanisms to regulate neuromuscular functions.
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24
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Ueda Y. The Role of Phosphoinositides in Synapse Function. Mol Neurobiol 2014; 50:821-38. [DOI: 10.1007/s12035-014-8768-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2013] [Accepted: 06/01/2014] [Indexed: 11/30/2022]
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25
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Dason JS, Smith AJ, Marin L, Charlton MP. Cholesterol and F-actin are required for clustering of recycling synaptic vesicle proteins in the presynaptic plasma membrane. J Physiol 2013; 592:621-33. [PMID: 24297851 DOI: 10.1113/jphysiol.2013.265447] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Synaptic vesicles (SVs) and their proteins must be recycled for sustained synaptic transmission. We tested the hypothesis that SV cholesterol is required for proper sorting of SV proteins during recycling in live presynaptic terminals. We used the reversible block of endocytosis in the Drosophila temperature-sensitive dynamin mutant shibire-ts1 to trap exocytosed SV proteins, and then examined the effect of experimental treatments on the distribution of these proteins within the presynaptic plasma membrane by confocal microscopy. SV proteins synaptotagmin, vglut and csp were clustered following SV trapping in control experiments but dispersed in samples treated with the cholesterol chelator methyl-β-cyclodextrin to extract SV cholesterol. There was accumulation of phosphatidylinositol (4,5)-bisphosphate (PIP2) in presynaptic terminals following SV trapping and this was reduced following SV cholesterol extraction. Reduced PIP2 accumulation was associated with disrupted accumulation of actin in presynaptic terminals. Similar to vesicular cholesterol extraction, disruption of actin by latrunculin A after SV proteins had been trapped on the plasma membrane resulted in the dispersal of SV proteins and prevented recovery of synaptic transmission due to impaired endocytosis following relief of the endocytic block. Our results demonstrate that vesicular cholesterol is required for aggregation of exocytosed SV proteins in the presynaptic plasma membrane and are consistent with a mechanism involving regulation of PIP2 accumulation and local actin polymerization by cholesterol. Thus, alteration of membrane or SV lipids may affect the ability of synapses to undergo sustained synaptic transmission by compromising the recycling of SV proteins.
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Affiliation(s)
- Jeffrey S Dason
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada, M5S 1A8.
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26
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Machado-Nils AV, de Faria LO, Vieira AS, Teixeira SA, Muscará MN, Ferrari EA. Daily cycling of nitric oxide synthase (NOS) in the hippocampus of pigeons (C. livia). J Circadian Rhythms 2013; 11:12. [PMID: 24176048 PMCID: PMC4177212 DOI: 10.1186/1740-3391-11-12] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 10/08/2013] [Indexed: 11/18/2022] Open
Abstract
Background Nitric oxide synthase (NOS) is essential for the synthesis of nitric oxide (NO), a non-conventional neurotransmitter with an important role in synaptic plasticity underlying processes of hippocampus-dependent memory and in the regulation of biological clocks and circadian rhythms. Many studies have shown that both the NOS cytosolic protein content and its enzymatic activity present a circadian variation in different regions of the rodent brain, including the hippocampus. The present study investigated the daily variation of NOS enzymatic activity and the cytosolic content of nNOS in the hippocampus of pigeons. Results Adult pigeons kept under a skeleton photoperiod were assigned to six different groups. Homogenates of the hippocampus obtained at six different times-of-day were used for NOS analyses. Both iNOS activity and nNOS cytosolic protein concentrations were highest during the subjective light phase and lowest in the subjective dark phase of the circadian period. ANOVA showed significant time differences for iNOS enzymatic activity (p < 0.05) and for nNOS protein content (p < 0.05) in the hippocampus. A significant daily rhythm for both iNOS and nNOS was confirmed by analysis with the Cosinor method (p < 0.05). The present findings indicate that the enzymatic activity of iNOS and content of nNOS protein in the hippocampus of pigeons exhibit a daily rhythm, with acrophase values occurring during the behavioral activity phase. Conclusions The data corroborate the reports on circadian variation of NOS in the mammalian hippocampus and can be considered indicative of a dynamic interaction between hippocampus-dependent processes and circadian clock mechanisms.
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Affiliation(s)
- Aline V Machado-Nils
- Departamento de Biologia Estrutural e Funcional, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), Rua Monteiro Lobato, 255, Campinas, São Paulo 13083-970, Brazil.
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Puchkov D, Haucke V. Greasing the synaptic vesicle cycle by membrane lipids. Trends Cell Biol 2013; 23:493-503. [DOI: 10.1016/j.tcb.2013.05.002] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Revised: 04/30/2013] [Accepted: 05/02/2013] [Indexed: 12/18/2022]
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Abstract
Inositol 1,4,5-trisphosphate (IP(3)) is a ubiquitous second messenger, derived from the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP(2)) by enzymes of the phospholipase C (PLC) family. Binding of IP(3) to its cognate receptor in the endoplasmic reticulum membrane leads to release of Ca(2+) into the cytoplasm, which is involved in the regulation of an array of cellular functions. Traditional techniques for the detection of IP(3) have required the extraction of a large number of cells, with limitations in the time resolution of changes in IP(3) and an inability to obtain detailed information on the dynamics of this second messenger in single cells. Recent progress in this field has led to the development of a number of genetically encoded fluorescent biosensors, which upon recombinant expression are able selectively to detect real-time changes in IP(3) in single live cells. In this chapter, I detail protocols for the expression, visualization (by confocol or fluorescence microscopy), and interpretation of data obtained with such biosensors expressed in mammalian cells.
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Affiliation(s)
- Carl P Nelson
- Department of Cardiovascular Sciences, Division of Anaesthesia, Critical Care, and Pain Management, Leicester Royal Infirmary, University of Leicester, Leicester, UK.
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Vernay A, Schaub S, Guillas I, Bassilana M, Arkowitz RA. A steep phosphoinositide bis-phosphate gradient forms during fungal filamentous growth. ACTA ACUST UNITED AC 2012; 198:711-30. [PMID: 22891265 PMCID: PMC3514036 DOI: 10.1083/jcb.201203099] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
A gradient of PI(4,5)P2 formed by phospholipid synthesis, diffusion,
and regulated turnover is crucial for filamentous growth. Membrane lipids have been implicated in many critical cellular processes, yet
little is known about the role of asymmetric lipid distribution in cell
morphogenesis. The phosphoinositide bis-phosphate PI(4,5)P2 is
essential for polarized growth in a range of organisms. Although an asymmetric
distribution of this phospholipid has been observed in some cells, long-range
gradients of PI(4,5)P2 have not been observed. Here, we show that in
the human pathogenic fungus Candida albicans a steep,
long-range gradient of PI(4,5)P2 occurs concomitant with emergence of
the hyphal filament. Both sufficient PI(4)P synthesis and the actin cytoskeleton
are necessary for this steep PI(4,5)P2 gradient. In contrast, neither
microtubules nor asymmetrically localized mRNAs are critical. Our results
indicate that a gradient of PI(4,5)P2, crucial for filamentous
growth, is generated and maintained by the filament tip–localized
PI(4)P-5-kinase Mss4 and clearing of this lipid at the back of the cell.
Furthermore, we propose that slow membrane diffusion of PI(4,5)P2
contributes to the maintenance of such a gradient.
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Affiliation(s)
- Aurélia Vernay
- Institute of Biology Valrose, Université Nice - Sophia Antipolis, 06108 Nice Cedex 2, France
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Eguchi K, Nakanishi S, Takagi H, Taoufiq Z, Takahashi T. Maturation of a PKG-dependent retrograde mechanism for exoendocytic coupling of synaptic vesicles. Neuron 2012; 74:517-29. [PMID: 22578503 DOI: 10.1016/j.neuron.2012.03.028] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/09/2012] [Indexed: 12/24/2022]
Abstract
At presynaptic terminals vesicular membranes are fused into plasma membrane upon exocytosis and retrieved by endocytosis. During a sustained high-frequency transmission, exoendocytic coupling is critical for the maintenance of synaptic transmission. Here, we show that this homeostatic coupling is supported by cGMP-dependent protein kinase (PKG) at the calyx of Held. This mechanism starts to operate after hearing onset during the second postnatal week, when PKG expression becomes upregulated in the brainstem. Pharmacological tests with capacitance measurements revealed that presynaptic PKG activity is supported by a retrograde signal cascade mediated by NO that is released by activation of postsynaptic NMDA receptors. Activation of PKG also upregulates phosphatidylinositol-4,5-bisphosphate, thereby accelerating endocytosis. Furthermore, presynaptic PKG activity upregulates synaptic fidelity during high-frequency transmission. We conclude that maturation of the PKG-dependent retrograde signal cascade strengthens the homeostatic plasticity for the maintenance of high-frequency synaptic transmission at the fast glutamatergic synapse.
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Affiliation(s)
- Kohgaku Eguchi
- Cellular & Molecular Synaptic Function Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Kunigami, Okinawa 904-0412, Japan.
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New insights in the activity of voltage sensitive phosphatases. Cell Signal 2012; 24:1541-7. [PMID: 22481094 DOI: 10.1016/j.cellsig.2012.03.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Revised: 03/13/2012] [Accepted: 03/20/2012] [Indexed: 11/23/2022]
Abstract
The Ciona intestinalis voltage sensitive phosphatase (Ci-VSP) was the first proven enzyme to be under direct control of the membrane potential. Ci-VSP belongs to a family of proteins known as Protein Tyrosine Phosphatases (PTP), which are a group of enzymes that catalyze the removal of phosphate groups from phosphatidylinositides and phosphorylated tyrosine residues on proteins. What makes Ci-VSP and similar phosphatases unique is the presence of a Voltage Sensing Domain (VSD) in their N-terminus. The VSD of Ci-VSP shares high homology with those from voltage-gated channels and confers voltage sensitivity to these enzymes. The catalytic domain of Ci-VSP displays extraordinary structural and functional similarities to PTEN. This latter protein is encoded by the Phosphatase and Tensin homolog deleted from chromosome 10 gene, thus its name, and it is known as a tumor suppressor. The resemblance between these proteins has prompted the use of PTEN as a template for the study of Ci-VSP and produced a rapid advance in our understanding of the mechanism of activity of Ci-VSP. This review will be focused on discussing recent advances in the understanding of the activation mechanism for these molecules known as electrochemical coupling.
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Koch M, Holt M. Coupling exo- and endocytosis: an essential role for PIP₂ at the synapse. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1821:1114-32. [PMID: 22387937 DOI: 10.1016/j.bbalip.2012.02.008] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2011] [Revised: 02/12/2012] [Accepted: 02/13/2012] [Indexed: 12/24/2022]
Abstract
Chemical synapses are specialist points of contact between two neurons, where information transfer takes place. Communication occurs through the release of neurotransmitter substances from small synaptic vesicles in the presynaptic terminal, which fuse with the presynaptic plasma membrane in response to neuronal stimulation. However, as neurons in the central nervous system typically only possess ~200 vesicles, high levels of release would quickly lead to a depletion in the number of vesicles, as well as leading to an increase in the area of the presynaptic plasma membrane (and possible misalignment with postsynaptic structures). Hence, synaptic vesicle fusion is tightly coupled to a local recycling of synaptic vesicles. For a long time, however, the exact molecular mechanisms coupling fusion and subsequent recycling remained unclear. Recent work now indicates a unique role for the plasma membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP(2)), acting together with the vesicular protein synaptotagmin, in coupling these two processes. In this work, we review the evidence for such a mechanism and discuss both the possible advantages and disadvantages for vesicle recycling (and hence signal transduction) in the nervous system. This article is part of a Special Issue entitled Lipids and Vesicular Transport.
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Affiliation(s)
- Marta Koch
- Laboratory of Neurogenetics, VIB Center for the Biology of Disease and K.U. Leuven Center for Human Genetics, O&N4 Herestraat 49, 3000 Leuven, Belgium
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Abstract
Phosphoinositides are important regulators of cellular homoeostasis and numerous signal-transduction pathways. One of their major features is their ability to recruit signalling proteins to membranes by direct interaction with phosphoinositide-binding modules. The distribution and dynamics of membrane phosphoinositides are therefore major determinants in the spatiotemporal control of cell signalling and membrane trafficking. However, standard biochemical approaches cannot reveal the dynamics of phosphoinositides at the single-cell level. A major technical advance has been the development of genetically encoded fluorescent phosphoinositide probes on the basis of the phosphoinositide-binding domains found in signalling proteins, such as the PH (pleckstrin homology) domain. This review describes the diverse fluorescent phosphoinositide probes available for imaging specific phosphoinositide species and how their use has improved the understanding of phosphoinositide signalling at the single-cell level.
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Affiliation(s)
- Guillaume Halet
- Department of Physiology, University College London, Gower Street, London WC1E 6BT, UK.
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Johnson JL, Erickson JW, Cerione RA. C-terminal di-arginine motif of Cdc42 protein is essential for binding to phosphatidylinositol 4,5-bisphosphate-containing membranes and inducing cellular transformation. J Biol Chem 2012; 287:5764-74. [PMID: 22215673 DOI: 10.1074/jbc.m111.336487] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rho GTPases regulate a diverse range of processes that are dependent on their proper cellular localization. The membrane localization of these GTPases is due in large part to their carboxyl-terminal geranylgeranyl moiety. In addition, most of the Rho family members contain a cluster of positively charged residues (i.e. a "polybasic domain"), directly preceding their geranylgeranyl moiety, and it has been suggested that this domain serves to fine-tune their localization among different cellular membrane sites. Here, we have taken a closer look at the role of the polybasic domain of Cdc42 in its ability to bind to membranes and induce the transformation of fibroblasts. A FRET assay for the binding of Cdc42 to liposomes of defined composition showed that Cdc42 associates more strongly with liposomes containing phosphatidylinositol 4,5-bisphosphate (PIP(2)) when compared either with uncharged control membranes or with liposomes containing a charge-equivalent amount of phosphatidylserine. The carboxyl-terminal di-arginine motif (Arg-186 and Arg-187) was shown to play an essential role in the binding of Cdc42 to PIP(2)-containing membranes. We further showed that substitutions for the di-arginine motif, when introduced within a constitutively active ("fast cycling") Cdc42(F28L) background, had little effect on the ability of the activated Cdc42 mutant to induce microspikes/filopodia in NIH 3T3 cells, whereas they eliminated its ability to transform fibroblasts. Taken together, these findings suggest that the di-arginine motif within the carboxyl terminus of Cdc42 is necessary for this GTPase to bind at membrane sites containing PIP(2), where it can initiate signaling activities that are essential for the oncogenic transformation of cells.
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Affiliation(s)
- Jared L Johnson
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
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Optogenetic reporters: Fluorescent protein-based genetically encoded indicators of signaling and metabolism in the brain. PROGRESS IN BRAIN RESEARCH 2012; 196:235-63. [PMID: 22341329 DOI: 10.1016/b978-0-444-59426-6.00012-4] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Fluorescent protein technology has evolved to include genetically encoded biosensors that can monitor levels of ions, metabolites, and enzyme activities as well as protein conformation and even membrane voltage. They are well suited to live-cell microscopy and quantitative analysis, and they can be used in multiple imaging modes, including one- or two-photon fluorescence intensity or lifetime microscopy. Although not nearly complete, there now exists a substantial set of genetically encoded reporters that can be used to monitor many aspects of neuronal and glial biology, and these biosensors can be used to visualize synaptic transmission and activity-dependent signaling in vitro and in vivo. In this review, we present an overview of design strategies for engineering biosensors, including sensor designs using circularly permuted fluorescent proteins and using fluorescence resonance energy transfer between fluorescent proteins. We also provide examples of indicators that sense small ions (e.g., pH, chloride, zinc), metabolites (e.g., glutamate, glucose, ATP, cAMP, lipid metabolites), signaling pathways (e.g., G protein-coupled receptors, Rho GTPases), enzyme activities (e.g., protein kinase A, caspases), and reactive species. We focus on examples where these genetically encoded indicators have been applied to brain-related studies and used with live-cell fluorescence microscopy.
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Cellular Mechanisms for the Biogenesis and Transport of Synaptic and Dense-Core Vesicles. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 299:27-115. [DOI: 10.1016/b978-0-12-394310-1.00002-3] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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37
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Abstract
A role for phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) in membrane fusion was originally identified for regulated dense-core vesicle exocytosis in neuroendocrine cells. Subsequent studies demonstrated essential roles for PI(4,5)P(2) in regulated synaptic vesicle and constitutive vesicle exocytosis. For regulated dense-core vesicle exocytosis, PI(4,5)P(2) appears to be primarily required for priming, a stage in vesicle exocytosis that follows vesicle docking and precedes Ca(2) (+)-triggered fusion. The priming step involves the organization of SNARE protein complexes for fusion. A central issue concerns the mechanisms by which PI(4,5)P(2) exerts an essential role in membrane fusion events at the plasma membrane. The observed microdomains of PI(4,5)P(2) in the plasma membrane of neuroendocrine cells at fusion sites has suggested possible direct effects of the phosphoinositide on membrane curvature and tension. More likely, PI(4,5)P(2) functions in vesicle exocytosis as in other cellular processes to recruit and activate PI(4,5)P(2)-binding proteins. CAPS and Munc13 proteins, which bind PI(4,5)P(2) and function in vesicle priming to organize SNARE proteins, are key candidates as effectors for the role of PI(4,5)P(2) in vesicle priming. Consistent with roles prior to fusion that affect SNARE function, subunits of the exocyst tethering complex involved in constitutive vesicle exocytosis also bind PI(4,5)P(2). Additional roles for PI(4,5)P(2) in fusion pore dilation have been described, which may involve other PI(4,5)P(2)-binding proteins such as synaptotagmin. Lastly, the SNARE proteins that mediate exocytic vesicle fusion contain highly basic membrane-proximal domains that interact with acidic phospholipids that likely affect their function.
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Affiliation(s)
- Thomas F J Martin
- Department of Biochemistry, University of Wisconsin-Madison, 433 Babcock Drive, 53706, Madison, WI, U.S.A,
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Wang Z, Liu H, Gu Y, Chapman ER. Reconstituted synaptotagmin I mediates vesicle docking, priming, and fusion. ACTA ACUST UNITED AC 2011; 195:1159-70. [PMID: 22184197 PMCID: PMC3246889 DOI: 10.1083/jcb.201104079] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
In vitro reconstitution fusion assays incorporating full-length membrane-anchored synaptotagmin I clarify its role in several steps in the secretory pathway. The synaptic vesicle protein synaptotagmin I (syt) promotes exocytosis via its ability to penetrate membranes in response to binding Ca2+ and through direct interactions with SNARE proteins. However, studies using full-length (FL) membrane-embedded syt in reconstituted fusion assays have yielded conflicting results, including a lack of effect, or even inhibition of fusion, by Ca2+. In this paper, we show that reconstituted FL syt promoted rapid docking of vesicles (<1 min) followed by a priming step (3–9 min) that was required for subsequent Ca2+-triggered fusion between v- and t-SNARE liposomes. Moreover, fusion occurred only when phosphatidylinositol 4,5-bisphosphate was included in the target membrane. This system also recapitulates some of the effects of syt mutations that alter synaptic transmission in neurons. Finally, we demonstrate that the cytoplasmic domain of syt exhibited mixed agonist/antagonist activity during regulated membrane fusion in vitro and in cells. Together, these findings reveal further convergence of reconstituted and cell-based systems.
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Affiliation(s)
- Zhao Wang
- Department of Neuroscience, Howard Hughes Medical Institute, University of Wisconsin, Madison, WI 53706, USA
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KCNQ5 channels control resting properties and release probability of a synapse. Nat Neurosci 2011; 14:840-7. [PMID: 21666672 PMCID: PMC3133966 DOI: 10.1038/nn.2830] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Accepted: 04/07/2011] [Indexed: 11/08/2022]
Abstract
Little is known about which ion channels determine the resting electrical properties of presynaptic membranes. In recordings made from the rat calyx of Held, a giant mammalian terminal, we found resting potential to be controlled by KCNQ (Kv7) K(+) channels, most probably KCNQ5 (Kv7.5) homomers. Unlike most KCNQ channels, which are activated only by depolarizing stimuli, the presynaptic channels began to activate just below the resting potential. As a result, blockers and activators of KCNQ5 depolarized or hyperpolarized nerve terminals, respectively, markedly altering resting conductance. Moreover, the background conductance set by KCNQ5 channels, together with Na(+) and hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels, determined the size and time course of the response to subthreshold stimuli. Signaling pathways known to directly affect exocytic machinery also regulated KCNQ5 channels, and increase or decrease of KCNQ5 channel activity controlled release probability through alterations in resting potential. Thus, ion channel determinants of presynaptic resting potential also control synaptic strength.
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40
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Mironov SL, Skorova EY. Stimulation of bursting in pre-Bötzinger neurons by Epac through calcium release and modulation of TRPM4 and K-ATP channels. J Neurochem 2011; 117:295-308. [PMID: 21281309 DOI: 10.1111/j.1471-4159.2011.07202.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The exchange factor directly activated by cAMP (Epac) can couple cAMP production to the activation of particular membrane and cytoplasmic targets. Using patch-clamp recordings and calcium imaging in organotypic brainstem slices, we examined the role of Epac in pre-Bötzinger complex, an essential part of the respiratory network. The selective agonist 8-(4-chlorophenylthio)-2'-O-methyl-cAMP (8-pCPT) sensitized calcium mobilisation from inositol-1,4,5-trisphosphate-sensitive internal stores that stimulated TRPM4 (transient receptor potential cation channel, subfamily M, Melastatin) channels and potentiated the bursts of action potentials. 8-pCPT actions were abolished after inhibition of phospholipase C with U73122 and depletion of calcium stores with thapsigargin. Caffeine-sensitive release channels were not modulated by 8-pCPT. Epac inhibited ATP-sensitive K(+) channels that also led to the enhancement of bursting by 8-pCPT. Bursting activity, spontaneous calcium transients and activity of TRPM4 and ATP-sensitive K(+) channels were potentiated after brief exposures to bradykinin and incubation with wortmannin produced opposite effects that can be explained by changes in phosphatidylinositol 4,5-bisphosphate levels. 8-pCPT stimulated the respiratory motor output in functionally intact preparations and the effects of bradykinin and wortmannin were identical to those observed in organotypic slices. The data thus indicate a novel pathway of controlling bursting activity in pre-Bötzinger complex neurons through Epac that can involved in reinforcement of the respiratory activity by cAMP.
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Affiliation(s)
- Sergej L Mironov
- DFG-Center of Molecular Physiology of the Brain, Department of Neuro- and Sensory Physiology, Georg-August-University, Göttingen, Germany.
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Wen P, Osborne S, Meunier F. Dynamic control of neuroexocytosis by phosphoinositides in health and disease. Prog Lipid Res 2011; 50:52-61. [DOI: 10.1016/j.plipres.2010.08.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 08/02/2010] [Indexed: 10/19/2022]
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Dovgan AV, Cherkas VP, Stepanyuk AR, Fitzgerald DJ, Haynes LP, Tepikin AV, Burgoyne RD, Belan PV. Decoding glutamate receptor activation by the Ca2+ sensor protein hippocalcin in rat hippocampal neurons. Eur J Neurosci 2010; 32:347-58. [PMID: 20704590 PMCID: PMC3069492 DOI: 10.1111/j.1460-9568.2010.07303.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Hippocalcin is a Ca2+-binding protein that belongs to a family of neuronal Ca2+sensors and is a key mediator of many cellular functions including synaptic plasticity and learning. However, the molecular mechanisms involved in hippocalcin signalling remain illusive. Here we studied whether glutamate receptor activation induced by locally applied or synaptically released glutamate can be decoded by hippocalcin translocation. Local AMPA receptor activation resulted in fast hippocalcin-YFP translocation to specific sites within a dendritic tree mainly due to AMPA receptor-dependent depolarization and following Ca2+influx via voltage-operated calcium channels. Short local NMDA receptor activation induced fast hippocalcin-YFP translocation in a dendritic shaft at the application site due to direct Ca2+influx via NMDA receptor channels. Intrinsic network bursting produced hippocalcin-YFP translocation to a set of dendritic spines when they were subjected to several successive synaptic vesicle releases during a given burst whereas no translocation to spines was observed in response to a single synaptic vesicle release and to back-propagating action potentials. The translocation to spines required Ca2+influx via synaptic NMDA receptors in which Mg2+ block is relieved by postsynaptic depolarization. This synaptic translocation was restricted to spine heads and even closely (within 1–2 μm) located spines on the same dendritic branch signalled independently. Thus, we conclude that hippocalcin may differentially decode various spatiotemporal patterns of glutamate receptor activation into site- and time-specific translocation to its targets. Hippocalcin also possesses an ability to produce local signalling at the single synaptic level providing a molecular mechanism for homosynaptic plasticity.
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Affiliation(s)
- A V Dovgan
- Department of General Physiology of the Nervous System, Bogomoletz Institute of Physiology, Kiev, Ukraine
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Davletov B, Montecucco C. Lipid function at synapses. Curr Opin Neurobiol 2010; 20:543-9. [DOI: 10.1016/j.conb.2010.06.008] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2010] [Revised: 05/27/2010] [Accepted: 06/26/2010] [Indexed: 11/25/2022]
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Carlini VP, Perez MF, Salde E, Schiöth HB, Ramirez OA, de Barioglio SR. Ghrelin induced memory facilitation implicates nitric oxide synthase activation and decrease in the threshold to promote LTP in hippocampal dentate gyrus. Physiol Behav 2010; 101:117-23. [PMID: 20451534 DOI: 10.1016/j.physbeh.2010.04.026] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2009] [Revised: 04/01/2010] [Accepted: 04/25/2010] [Indexed: 12/16/2022]
Abstract
Although the hypothalamus has been long considered the main ghrelin (Ghr) target organ mediating orexigenic effects, recently it has been shown that in-vivo Ghr hippocampus administration improves learning and memory in the inhibitory avoidance paradigm. However, the possible mechanisms underlying this memory facilitation effect have not been clarified. Given that the biochemical memory cascade into the hippocampus involves nitric oxide (NO) synthesis via NO synthase (NOS) activation, we investigated 1) if Ghr administration modulated NOS activity in the hippocampus; and 2) if hippocampal NOS inhibition influenced Ghr-induced memory facilitation, using a behavioral paradigm, biochemical determinations and an electrophysiological model. Our results showed that intra-hippocampal Ghr administration increased the NOS activity in a dose dependent manner, and reduced the threshold for LTP generation in dentate gyrus of rat hippocampus. Moreover, pre-administration of NG-nitro-l-arginine (l-NOArg) in the hippocampus partially prevented the Ghr-induced memory improvement, abolished the increase in NOS activity, and prevented the decreased threshold to generate LTP induced by Ghr. These findings suggest that activation of the NOS/NO pathway in hippocampus participates in the effects of Ghr on memory consolidation and is related with plastic properties of the hippocampal three-synaptic loop.
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Affiliation(s)
- Valeria P Carlini
- IFEC, CONICET, Departamento de Farmacología, Facultad de Ciencias Químicas, UNC, Córdoba, Argentina.
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Zhang X, Chen X, Jia C, Geng X, Du X, Zhang H. Depolarization increases phosphatidylinositol (PI) 4,5-bisphosphate level and KCNQ currents through PI 4-kinase mechanisms. J Biol Chem 2010; 285:9402-9409. [PMID: 20106968 DOI: 10.1074/jbc.m109.068205] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
A growing body of evidence shows that membrane phosphatidylinositol 4,5-bisphosphates (PtdIns(4,5)P(2), PIP(2)) play an important role in cell signaling. The presence of PIP(2) is fundamentally important for maintaining the functions of a large number of ion channels and transporters, and for other cell processes such as vesicle trafficking, mobility, and endo- and exocytosis. PIP(2) levels in the membrane are dynamically modulated, which is an important signaling mechanism for modulation of PIP(2)-dependent cellular processes. In this study, we describe a novel mechanism of membrane PIP(2) modulation. Membrane depolarization induces an elevation in membrane PIP(2), and subsequently increases functions of PIP(2)-sensitive KCNQ potassium channels expressed in Xenopus oocytes. Further evidence suggests that the depolarization-induced elevation of membrane PIP(2) occurs through increased activity of PI4 kinase. With increased recognition of the importance of PIP(2) in cell function, the effect of membrane depolarization in PIP(2) metabolism is destined to have important physiological implications.
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Affiliation(s)
- Xuan Zhang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050017, China
| | - Xingjuan Chen
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050017, China
| | - Caixia Jia
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050017, China
| | - Xian Geng
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050017, China
| | - Xiaona Du
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050017, China
| | - Hailin Zhang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050017, China.
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Verstreken P, Ohyama T, Haueter C, Habets RL, Lin YQ, Swan LE, Ly CV, Venken KJT, De Camilli P, Bellen HJ. Tweek, an evolutionarily conserved protein, is required for synaptic vesicle recycling. Neuron 2009; 63:203-15. [PMID: 19640479 PMCID: PMC2759194 DOI: 10.1016/j.neuron.2009.06.017] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2007] [Revised: 04/24/2009] [Accepted: 06/11/2009] [Indexed: 11/18/2022]
Abstract
Synaptic vesicle endocytosis is critical for maintaining synaptic communication during intense stimulation. Here we describe Tweek, a conserved protein that is required for synaptic vesicle recycling. tweek mutants show reduced FM1-43 uptake, cannot maintain release during intense stimulation, and harbor larger than normal synaptic vesicles, implicating it in vesicle recycling at the synapse. Interestingly, the levels of a fluorescent PI(4,5)P(2) reporter are reduced at tweek mutant synapses, and the probe is aberrantly localized during stimulation. In addition, various endocytic adaptors known to bind PI(4,5)P(2) are mislocalized and the defects in FM1-43 dye uptake and adaptor localization are partially suppressed by removing one copy of the phosphoinositide phosphatase synaptojanin, suggesting a role for Tweek in maintaining proper phosphoinositide levels at synapses. Our data implicate Tweek in regulating synaptic vesicle recycling via an action mediated at least in part by the regulation of PI(4,5)P(2) levels or availability at the synapse.
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Affiliation(s)
- Patrik Verstreken
- Department of Molecular and Human Genetics and Howard Hughes Medical Institute, Baylor College of Medicine, One Baylor Plaza, Houston, TX, USA
- VIB, Department of Molecular and Developmental Genetics, Program in Molecular and Developmental Genetics, Program in Cognitive and Molecular Neuroscience, Laboratory of Neuronal Communication, Herestraat 49, Leuven, Belgium
- K.U.Leuven, Center for Human Genetics, Program in Molecular and Developmental Genetics, Program in Cognitive and Molecular Neuroscience, Laboratory of Neuronal Communication, Herestraat 49 Leuven, Belgium
| | - Tomoko Ohyama
- Department of Molecular and Human Genetics and Howard Hughes Medical Institute, Baylor College of Medicine, One Baylor Plaza, Houston, TX, USA
| | - Claire Haueter
- Department of Molecular and Human Genetics and Howard Hughes Medical Institute, Baylor College of Medicine, One Baylor Plaza, Houston, TX, USA
| | - Ron L.P. Habets
- VIB, Department of Molecular and Developmental Genetics, Program in Molecular and Developmental Genetics, Program in Cognitive and Molecular Neuroscience, Laboratory of Neuronal Communication, Herestraat 49, Leuven, Belgium
- K.U.Leuven, Center for Human Genetics, Program in Molecular and Developmental Genetics, Program in Cognitive and Molecular Neuroscience, Laboratory of Neuronal Communication, Herestraat 49 Leuven, Belgium
| | - Yong Q. Lin
- Department of Molecular and Human Genetics and Howard Hughes Medical Institute, Baylor College of Medicine, One Baylor Plaza, Houston, TX, USA
| | - Laura E. Swan
- Department of Cell Biology, Howard Hughes Medical Institute, Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT, USA
| | - Cindy V. Ly
- Department of Neuroscience, Baylor College of Medicine, One Baylor Plaza, Houston, TX, USA
| | - Koen J. T. Venken
- Department of Molecular and Human Genetics and Howard Hughes Medical Institute, Baylor College of Medicine, One Baylor Plaza, Houston, TX, USA
- Program in Developmental Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX, USA
| | - Pietro De Camilli
- Department of Cell Biology, Howard Hughes Medical Institute, Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT, USA
| | - Hugo J. Bellen
- Department of Molecular and Human Genetics and Howard Hughes Medical Institute, Baylor College of Medicine, One Baylor Plaza, Houston, TX, USA
- Department of Neuroscience, Baylor College of Medicine, One Baylor Plaza, Houston, TX, USA
- Program in Developmental Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX, USA
- Correspondence:
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47
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Investigation of the H+–myo-inositol transporter (HMIT) as a neuronal regulator of phosphoinositide signalling. Biochem Soc Trans 2009; 37:1139-43. [DOI: 10.1042/bst0371139] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Phosphoinositide signalling regulates a series of important neuronal processes that are thought to be altered in mood disorders. Furthermore, mood-stabilizing drugs inhibit key enzymes that regulate phosphoinositide production and alter neuronal growth cone morphology in an inositol-reversible manner. Inositol is taken up by neurons from the extracellular fluid, presumably via membrane transporters; it can also be synthesized by the enzyme MIP-synthase (myo-inositol-1-phosphate synthase) and, in addition, it is generated by inositol phospholipid hydrolysis. The neuronal-specific HMIT (H+–myo-inositol transporter) represents a potential regulator of inositol signalling in neurons that warrants further investigation.
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48
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Immunocytochemical techniques reveal multiple, distinct cellular pools of PtdIns4P and PtdIns(4,5)P(2). Biochem J 2009; 422:23-35. [PMID: 19508231 PMCID: PMC2722159 DOI: 10.1042/bj20090428] [Citation(s) in RCA: 408] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
PtdIns4P is the major precursor for the synthesis of the multifunctional plasma membrane lipid, PtdIns(4,5)P2. Yet PtdIns4P also functions as a regulatory lipid in its own right, particularly at the Golgi apparatus. In the present study we define specific conditions that enable preservation of several organellar membranes for the immunocytochemical detection of PtdIns4P. We report distinct pools of this lipid in both Golgi and plasma membranes, which are synthesized by different PI4K (phosphatidylinositol 4-kinase) activities, and also the presence of PtdIns4P in cytoplasmic vesicles, which are not readily identifiable as PI4K containing trafficking intermediates. In addition, we present evidence that the majority of PtdIns4P resides in the plasma membrane, where it is metabolically distinct from the steady-state plasma membrane pool of PtdIns(4,5)P2.
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49
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Yakir-Tamang L, Gerst JE. A phosphatidylinositol-transfer protein and phosphatidylinositol-4-phosphate 5-kinase control Cdc42 to regulate the actin cytoskeleton and secretory pathway in yeast. Mol Biol Cell 2009; 20:3583-97. [PMID: 19477927 DOI: 10.1091/mbc.e08-10-1073] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The actin cytoskeleton rapidly depolarizes in yeast secretory (sec) mutants at restrictive temperatures. Thus, an unknown signal conferred upon secretion is necessary for actin polarity and exocytosis. Here, we show that a phosphatidylinositol (PI) transfer protein, Sfh5, and a phosphatidylinositol-4-phosphate 5-kinase, Mss4, facilitate Cdc42 activation to concomitantly regulate both actin and protein trafficking. Defects in Mss4 function led to actin depolarization, an inhibition of secretion, reduced levels of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P(2)] in membranes, mislocalization of a pleckstrin homology domain fused to green fluorescent protein, and the mislocalization of Cdc42. Similar defects were observed in sec, myo2-66, and cdc42-6 mutants at elevated temperatures and were rescued by the overexpression of MSS4. Likewise, the overexpression of SFH5 or CDC42 could ameliorate these defects in many sec mutants, most notably in sec3Delta cells, indicating that Cdc42-mediated effects upon actin and secretion do not necessitate Sec3 function. Moreover, mutation of the residues involved in PI binding in Sfh5 led to the mislocalization and loss of function of both Sfh5 and Cdc42. Based upon these findings, we propose that the exocytic signal involves PI delivery to the PI kinases (i.e., Mss4) by Sfh5, generation of PI(4,5)P(2), and PI(4,5)P(2)-dependent regulation of Cdc42 and the actin cytoskeleton.
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Affiliation(s)
- Liat Yakir-Tamang
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
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50
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Paradoxical facilitation of pentylenetetrazole-induced convulsion susceptibility in mice lacking neuronal nitric oxide synthase. Neuroscience 2009; 159:735-43. [DOI: 10.1016/j.neuroscience.2008.12.040] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2008] [Revised: 12/07/2008] [Accepted: 12/23/2008] [Indexed: 11/24/2022]
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