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de Zélicourt A, Fayssoil A, Mansart A, Zarrouki F, Karoui A, Piquereau J, Lefebvre F, Gerbaud P, Mika D, Dakouane-Giudicelli M, Lanchec E, Feng M, Leblais V, Bobe R, Launay JM, Galione A, Gomez AM, de la Porte S, Cancela JM. Two-pore channels (TPCs) acts as a hub for excitation-contraction coupling, metabolism and cardiac hypertrophy signalling. Cell Calcium 2024; 117:102839. [PMID: 38134531 DOI: 10.1016/j.ceca.2023.102839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 12/01/2023] [Accepted: 12/02/2023] [Indexed: 12/24/2023]
Abstract
Ca2+ signaling is essential for cardiac contractility and excitability in heart function and remodeling. Intriguingly, little is known about the role of a new family of ion channels, the endo-lysosomal non-selective cation "two-pore channel" (TPCs) in heart function. Here we have used double TPC knock-out mice for the 1 and 2 isoforms of TPCs (Tpcn1/2-/-) and evaluated their cardiac function. Doppler-echocardiography unveils altered left ventricular (LV) systolic function associated with a LV relaxation impairment. In cardiomyocytes isolated from Tpcn1/2-/- mice, we observed a reduction in the contractile function with a decrease in the sarcoplasmic reticulum Ca2+ content and a reduced expression of various key proteins regulating Ca2+ stores, such as calsequestrin. We also found that two main regulators of the energy metabolism, AMP-activated protein kinase and mTOR, were down regulated. We found an increase in the expression of TPC1 and TPC2 in a model of transverse aortic constriction (TAC) mice and in chronically isoproterenol infused WT mice. In this last model, adaptive cardiac hypertrophy was reduced by Tpcn1/2 deletion. Here, we propose a central role for TPCs and lysosomes that could act as a hub integrating information from the excitation-contraction coupling mechanisms, cellular energy metabolism and hypertrophy signaling.
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Affiliation(s)
- Antoine de Zélicourt
- Université Paris-Saclay, UVSQ, Inserm, END-ICAP, 78000 Versailles, France; Neuroscience Paris-Saclay Institute (Neuro-PSI), UMR 9197, CNRS- Université Paris-Saclay, Saclay, 91400, France
| | - Abdallah Fayssoil
- Université Paris-Saclay, UVSQ, Inserm, END-ICAP, 78000 Versailles, France
| | - Arnaud Mansart
- Université Paris-Saclay, UVSQ, Inserm, 2I, 78000 Versailles, France
| | - Faouzi Zarrouki
- Neuroscience Paris-Saclay Institute (Neuro-PSI), UMR 9197, CNRS- Université Paris-Saclay, Saclay, 91400, France
| | - Ahmed Karoui
- UMR-S 1180, INSERM, Signaling and cardiovascular pathophysiology, Université Paris-Saclay, 91400 Orsay, France
| | - Jérome Piquereau
- UMR-S 1180, INSERM, Signaling and cardiovascular pathophysiology, Université Paris-Saclay, 91400 Orsay, France
| | - Florence Lefebvre
- UMR-S 1180, INSERM, Signaling and cardiovascular pathophysiology, Université Paris-Saclay, 91400 Orsay, France
| | - Pascale Gerbaud
- UMR-S 1180, INSERM, Signaling and cardiovascular pathophysiology, Université Paris-Saclay, 91400 Orsay, France
| | - Delphine Mika
- UMR-S 1180, INSERM, Signaling and cardiovascular pathophysiology, Université Paris-Saclay, 91400 Orsay, France
| | | | - Erwan Lanchec
- Neuroscience Paris-Saclay Institute (Neuro-PSI), UMR 9197, CNRS- Université Paris-Saclay, Saclay, 91400, France
| | - Miao Feng
- UMR-S 1176, Université Paris-Saclay, Le Kremlin Bicêtre, France
| | - Véronique Leblais
- UMR-S 1180, INSERM, Signaling and cardiovascular pathophysiology, Université Paris-Saclay, 91400 Orsay, France
| | - Régis Bobe
- UMR-S 1176, Université Paris-Saclay, Le Kremlin Bicêtre, France
| | - Jean-Marie Launay
- Service de Biochimie, INSERM UMR S942, Hôpital Lariboisière, Paris, France
| | - Antony Galione
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, United Kingdom
| | - Ana Maria Gomez
- UMR-S 1180, INSERM, Signaling and cardiovascular pathophysiology, Université Paris-Saclay, 91400 Orsay, France
| | - Sabine de la Porte
- Université Paris-Saclay, UVSQ, Inserm, END-ICAP, 78000 Versailles, France
| | - José-Manuel Cancela
- Neuroscience Paris-Saclay Institute (Neuro-PSI), UMR 9197, CNRS- Université Paris-Saclay, Saclay, 91400, France.
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Lu J, Dreyer I, Dickinson MS, Panzer S, Jaślan D, Navarro-Retamal C, Geiger D, Terpitz U, Becker D, Stroud RM, Marten I, Hedrich R. Vicia faba SV channel VfTPC1 is a hyperexcitable variant of plant vacuole Two Pore Channels. eLife 2023; 12:e86384. [PMID: 37991833 PMCID: PMC10665017 DOI: 10.7554/elife.86384] [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: 01/23/2023] [Accepted: 10/12/2023] [Indexed: 11/23/2023] Open
Abstract
To fire action-potential-like electrical signals, the vacuole membrane requires the two-pore channel TPC1, formerly called SV channel. The TPC1/SV channel functions as a depolarization-stimulated, non-selective cation channel that is inhibited by luminal Ca2+. In our search for species-dependent functional TPC1 channel variants with different luminal Ca2+ sensitivity, we found in total three acidic residues present in Ca2+ sensor sites 2 and 3 of the Ca2+-sensitive AtTPC1 channel from Arabidopsis thaliana that were neutral in its Vicia faba ortholog and also in those of many other Fabaceae. When expressed in the Arabidopsis AtTPC1-loss-of-function background, wild-type VfTPC1 was hypersensitive to vacuole depolarization and only weakly sensitive to blocking luminal Ca2+. When AtTPC1 was mutated for these VfTPC1-homologous polymorphic residues, two neutral substitutions in Ca2+ sensor site 3 alone were already sufficient for the Arabidopsis At-VfTPC1 channel mutant to gain VfTPC1-like voltage and luminal Ca2+ sensitivity that together rendered vacuoles hyperexcitable. Thus, natural TPC1 channel variants exist in plant families which may fine-tune vacuole excitability and adapt it to environmental settings of the particular ecological niche.
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Affiliation(s)
- Jinping Lu
- Julius-Maximilians-Universität (JMU), Biocenter, Department of Molecular Plant Physiology and BiophysicsWürzburgGermany
- School of Life Sciences, Zhengzhou UniversityZhengzhouChina
| | - Ingo Dreyer
- Universidad de Talca, Faculty of Engineering, Center of Bioinformatics, Simulation and ModelingTalcaChile
| | - Miles Sasha Dickinson
- University of California San Francisco, Department of Biochemistry and BiophysicsSan FranciscoUnited States
| | - Sabine Panzer
- Julius-Maximilians-Universität (JMU), Biocenter, Theodor-Boveri-Institute, Department of Biotechnology and BiophysicsWürzburgGermany
| | - Dawid Jaślan
- Julius-Maximilians-Universität (JMU), Biocenter, Department of Molecular Plant Physiology and BiophysicsWürzburgGermany
- Ludwig Maximilians-Universität, Faculty of Medicine, Walther Straub Institute of Pharmacology and ToxicologyMunichGermany
| | - Carlos Navarro-Retamal
- Universidad de Talca, Faculty of Engineering, Center of Bioinformatics, Simulation and ModelingTalcaChile
- Department of Cell Biology and Molecular Genetics, University of MarylandCollege ParkUnited States
| | - Dietmar Geiger
- Julius-Maximilians-Universität (JMU), Biocenter, Department of Molecular Plant Physiology and BiophysicsWürzburgGermany
| | - Ulrich Terpitz
- Julius-Maximilians-Universität (JMU), Biocenter, Theodor-Boveri-Institute, Department of Biotechnology and BiophysicsWürzburgGermany
| | - Dirk Becker
- Julius-Maximilians-Universität (JMU), Biocenter, Department of Molecular Plant Physiology and BiophysicsWürzburgGermany
| | - Robert M Stroud
- University of California San Francisco, Department of Biochemistry and BiophysicsSan FranciscoUnited States
| | - Irene Marten
- Julius-Maximilians-Universität (JMU), Biocenter, Department of Molecular Plant Physiology and BiophysicsWürzburgGermany
| | - Rainer Hedrich
- Julius-Maximilians-Universität (JMU), Biocenter, Department of Molecular Plant Physiology and BiophysicsWürzburgGermany
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Wahl-Schott C, Freichel M, Hennis K, Philippaert K, Ottenheijm R, Tsvilovskyy V, Varbanov H. Characterization of Endo-Lysosomal Cation Channels Using Calcium Imaging. Handb Exp Pharmacol 2023; 278:277-304. [PMID: 36894791 DOI: 10.1007/164_2023_637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/11/2023]
Abstract
Endo-lysosomes are membrane-bound acidic organelles that are involved in endocytosis, recycling, and degradation of extracellular and intracellular material. The membranes of endo-lysosomes express several Ca2+-permeable cation ion channels, including two-pore channels (TPC1-3) and transient receptor potential mucolipin channels (TRPML1-3). In this chapter, we will describe four different state-of-the-art Ca2+ imaging approaches, which are well-suited to investigate the function of endo-lysosomal cation channels. These techniques include (1) global cytosolic Ca2+ measurements, (2) peri-endo-lysosomal Ca2+ imaging using genetically encoded Ca2+ sensors that are directed to the cytosolic endo-lysosomal membrane surface, (3) Ca2+ imaging of endo-lysosomal cation channels, which are engineered in order to redirect them to the plasma membrane in combination with approaches 1 and 2, and (4) Ca2+ imaging by directing Ca2+ indicators to the endo-lysosomal lumen. Moreover, we will review useful small molecules, which can be used as valuable tools for endo-lysosomal Ca2+ imaging. Rather than providing complete protocols, we will discuss specific methodological issues related to endo-lysosomal Ca2+ imaging.
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Affiliation(s)
- Christian Wahl-Schott
- Institut für Kardiovaskuläre Physiologie und Pathophysiologie, Lehrstuhl für Vegetative Physiologie, Biomedizinisches Zentrum, Ludwig-Maximilians-Universität München, München, Germany.
| | - Marc Freichel
- Institute of Pharmacology, Heidelberg University, Heidelberg, Germany. .,DZHK (German Centre for Cardiovascular Research), Heidelberg/Mannheim, Germany.
| | - Konstantin Hennis
- Institut für Kardiovaskuläre Physiologie und Pathophysiologie, Lehrstuhl für Vegetative Physiologie, Biomedizinisches Zentrum, Ludwig-Maximilians-Universität München, München, Germany
| | - Koenraad Philippaert
- Institute of Pharmacology, Heidelberg University, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Heidelberg/Mannheim, Germany
| | - Roger Ottenheijm
- Institute of Pharmacology, Heidelberg University, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Heidelberg/Mannheim, Germany
| | - Volodymyr Tsvilovskyy
- Institute of Pharmacology, Heidelberg University, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Heidelberg/Mannheim, Germany
| | - Hristo Varbanov
- Institut für Neurophysiologie, Medizinische Hochschule Hannover(MHH), Hannover, Germany
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She J, Guo J, Jiang Y. Structure and Function of Plant and Mammalian TPC Channels. Handb Exp Pharmacol 2023; 278:155-180. [PMID: 35879575 DOI: 10.1007/164_2022_599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/28/2023]
Abstract
Two-pore channels (TPCs) belong to the family of voltage-gated tetrameric cation channels and are ubiquitously expressed in organelles of animals and plants. These channels are believed to be evolutionary intermediates between homotetrameric voltage-gated potassium/sodium channels and the four-domain, single subunit, voltage-gated sodium/calcium channels. Each TPC subunit contains 12 transmembrane segments that can be divided into two homologous copies of an S1-S6 Shaker-like 6-TM domain. A functional TPC channel assembles as a dimer - the equivalent of a voltage-gated tetrameric cation channel. The plant TPC channel is localized in the vacuolar membrane and is also called the SV channel for generating the slow vacuolar (SV) current observed long before its molecular identification. Three subfamilies of mammalian TPC channels have been defined - TPC1, 2, and 3 - with the first two being ubiquitously expressed in animals and TPC3 being expressed in some animals but not in humans. Mammalian TPC1 and TPC2 are localized to the endolysosomal membrane and their functions are associated with various physiological processes. TPC3 is localized in the plasma membrane and its physiological function is not well defined.
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Affiliation(s)
- Ji She
- MOE Key Laboratory for Cellular Dynamics, School of Life Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China
| | - Jiangtao Guo
- Department of Biophysics, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
- Department of Neurology, the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Youxing Jiang
- Howard Hughes Medical Institute, Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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5
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Dietrich P, Gradogna A, Carpaneto A. The Plant Vacuole as Heterologous System to Characterize the Functional Properties of TPC Channels. Handb Exp Pharmacol 2023; 278:235-247. [PMID: 35879579 DOI: 10.1007/164_2022_604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/28/2023]
Abstract
Human TPC channels are an emerging family of intracellular proteins fundamental for cell physiology and involved in various severe pathologies. Their localization in the membranes of endo-lysosomes, intracellular compartments of submicrometric dimensions, makes their study difficult with usual electrophysiological techniques. In this work, we show how the plant vacuole, a versatile organelle that can occupy up to 90% of the volume in mature plant cells, can be used as a heterologous system of expression for functional characterization. For this purpose, the use of vacuoles isolated from mesophyll cells of the Arabidopsis thaliana mutant lacking the endogenous TPC avoids unwanted interferences. The patch-clamp technique can be successfully applied to plant vacuoles in all different configuration modes; of note, the whole-vacuole configuration allows to study channel modulation by cytosolic factors. The combination of patch-clamp with fluorescence techniques, for example, by using fluorescent probes sensitive to specific ions of interest, represents a useful extension to investigate the selectivity properties of the channels. Therefore, the plant vacuole, similar to Xenopus oocytes for ion channels and transporters localized in the plasma membrane, has the capability to become a model system for functional studies on intracellular ion channels and transporters.
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Affiliation(s)
- P Dietrich
- Lehrstuhl für Molekulare Pflanzenphysiologie, Department Biologie Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | | | - A Carpaneto
- Institute of Biophysics, Genoa, Italy.
- Department of Earth, Environment and Life Sciences (DISTAV) - University of Genoa, Genoa, Italy.
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6
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Enrich C, Lu A, Tebar F, Rentero C, Grewal T. Ca 2+ and Annexins - Emerging Players for Sensing and Transferring Cholesterol and Phosphoinositides via Membrane Contact Sites. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1422:393-438. [PMID: 36988890 DOI: 10.1007/978-3-031-21547-6_15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
Abstract
Maintaining lipid composition diversity in membranes from different organelles is critical for numerous cellular processes. However, many lipids are synthesized in the endoplasmic reticulum (ER) and require delivery to other organelles. In this scenario, formation of membrane contact sites (MCS) between neighbouring organelles has emerged as a novel non-vesicular lipid transport mechanism. Dissecting the molecular composition of MCS identified phosphoinositides (PIs), cholesterol, scaffolding/tethering proteins as well as Ca2+ and Ca2+-binding proteins contributing to MCS functioning. Compelling evidence now exists for the shuttling of PIs and cholesterol across MCS, affecting their concentrations in distinct membrane domains and diverse roles in membrane trafficking. Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) at the plasma membrane (PM) not only controls endo-/exocytic membrane dynamics but is also critical in autophagy. Cholesterol is highly concentrated at the PM and enriched in recycling endosomes and Golgi membranes. MCS-mediated cholesterol transfer is intensely researched, identifying MCS dysfunction or altered MCS partnerships to correlate with de-regulated cellular cholesterol homeostasis and pathologies. Annexins, a conserved family of Ca2+-dependent phospholipid binding proteins, contribute to tethering and untethering events at MCS. In this chapter, we will discuss how Ca2+ homeostasis and annexins in the endocytic compartment affect the sensing and transfer of cholesterol and PIs across MCS.
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Affiliation(s)
- Carlos Enrich
- Departament de Biomedicina, Unitat de Biologia Cel⋅lular, Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.
- Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain.
| | - Albert Lu
- Departament de Biomedicina, Unitat de Biologia Cel⋅lular, Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
- Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain
| | - Francesc Tebar
- Departament de Biomedicina, Unitat de Biologia Cel⋅lular, Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
- Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain
| | - Carles Rentero
- Departament de Biomedicina, Unitat de Biologia Cel⋅lular, Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
- Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain
| | - Thomas Grewal
- School of Pharmacy, Faculty of Medicine and Health, University of Sydney, Sydney, NSW, Australia
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Minicozzi V, Qi T, Gradogna A, Pozzolini M, Milenkovic S, Filippini A, Ceccarelli M, Carpaneto A. A commentary on the inhibition of human TPC2 channel by the natural flavonoid naringenin: Methods, experiments, and ideas. Biomol Concepts 2023; 14:bmc-2022-0036. [PMID: 37677148 DOI: 10.1515/bmc-2022-0036] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Accepted: 08/14/2023] [Indexed: 09/09/2023] Open
Abstract
Human endo-lysosomes possess a class of proteins called TPC channels on their membrane, which are essential for proper cell functioning. This protein family can be functionally studied by expressing them in plant vacuoles. Inhibition of hTPC activity by naringenin, one of the main flavonoids present in the human diet, has the potential to be beneficial in severe human diseases such as solid tumor development, melanoma, and viral infections. We attempted to identify the molecular basis of the interaction between hTPC2 and naringenin, using ensemble docking on molecular dynamics (MD) trajectories, but the specific binding site remains elusive, posing a challenge that could potentially be addressed in the future by increased computational power in MD and the combined use of microscopy techniques such as cryo-EM.
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Affiliation(s)
- Velia Minicozzi
- INFN and Department of Physics, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma, Italy
| | - Tianwen Qi
- Department of Earth, Environment and Life Sciences (DISTAV), University of Genoa, Viale Benedetto XV 5, 16132 Genova, Italy
| | - Antonella Gradogna
- Institute of Biophysics, National Research Council, Via De Marini 6, 16149 Genova, Italy
| | - Marina Pozzolini
- Department of Earth, Environment and Life Sciences (DISTAV), University of Genoa, Viale Benedetto XV 5, 16132 Genova, Italy
| | - Stefan Milenkovic
- Department of Physics, University of Cagliari, 09042 Monserrato, Italy
| | - Antonio Filippini
- Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, Unit of Histology and Medical Embryology, Sapienza University, 16 Via A. Scarpa, 00161 Rome, Italy
| | - Matteo Ceccarelli
- Department of Physics, University of Cagliari, 09042 Monserrato, Italy
| | - Armando Carpaneto
- Department of Earth, Environment and Life Sciences (DISTAV), University of Genoa, Viale Benedetto XV 5, 16132 Genova, Italy
- Institute of Biophysics, National Research Council, Via De Marini 6, 16149 Genova, Italy
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Jaślan D, Ferro IF, Kudrina V, Yuan Y, Patel S, Grimm C. PI(3,5)P 2 and NAADP: Team players or lone warriors? - New insights into TPC activation modes. Cell Calcium 2023; 109:102675. [PMID: 36525777 DOI: 10.1016/j.ceca.2022.102675] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 11/21/2022] [Accepted: 11/22/2022] [Indexed: 12/13/2022]
Abstract
NAADP (nicotinic acid adenine dinucleotide phosphate) is a second messenger, releasing Ca2+ from acidic calcium stores such as endosomes and lysosomes. PI(3,5)P2 (phosphatidylinositol 3,5-bisphosphate) is a phospho-inositide, residing on endolysosomal membranes and likewise releasing Ca2+ from endosomes and lysosomes. Both compounds have been shown to activate endolysosomal two-pore channels (TPCs) in mammalian cells. However, their effects on ion permeability as demonstrated specifically for TPC2 differ. While PI(3,5)P2 elicits predominantly Na+-selective currents, NAADP increases the Ca2+ permeability of the channel. What happens when both compounds are applied simultaneously was unclear until recently.
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Affiliation(s)
- Dawid Jaślan
- Walther Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, Ludwig-Maximilians-University, Munich, Germany
| | - Irene Flavia Ferro
- Walther Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, Ludwig-Maximilians-University, Munich, Germany
| | - Veronika Kudrina
- Walther Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, Ludwig-Maximilians-University, Munich, Germany
| | - Yu Yuan
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, United Kingdom
| | - Sandip Patel
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, United Kingdom
| | - Christian Grimm
- Walther Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, Ludwig-Maximilians-University, Munich, Germany.
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Du C, Guan X, Yan J. Two-pore channel blockade by phosphoinositide kinase inhibitors YM201636 and PI-103 determined by a histidine residue near pore-entrance. Commun Biol 2022; 5:738. [PMID: 35871252 PMCID: PMC9308409 DOI: 10.1038/s42003-022-03701-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Accepted: 07/11/2022] [Indexed: 12/04/2022] Open
Abstract
Human two-pore channels (TPCs) are endolysosomal cation channels and play an important role in NAADP-evoked Ca2+ release and endomembrane dynamics. We found that YM201636, a PIKfyve inhibitor, potently inhibits PI(3,5)P2-activated human TPC2 with an IC50 of 0.16 μM. YM201636 also effectively inhibits NAADP-activated TPC2 and a constitutively-open TPC2 L690A/L694A mutant channel; whereas it exerts little effect when applied in the channel’s closed state. PI-103, a YM201636 analog and an inhibitor of PI3K and mTOR, also inhibits human TPC2 with an IC50 of 0.64 μM. With mutational, virtual docking, and molecular dynamic simulation analyses, we found that YM201636 and PI-103 directly block the TPC2’s open-state channel pore at the bundle-cross pore-gate region where a nearby H699 residue is a key determinant for channel’s sensitivity to the inhibitors. H699 likely interacts with the blockers around the pore entrance and facilitates their access to the pore. Substitution of a Phe for H699 largely accounts for the TPC1 channel’s insensitivity to YM201636. These findings identify two potent TPC2 channel blockers, reveal a channel pore entrance blockade mechanism, and provide an ion channel target in interpreting the pharmacological effects of two commonly used phosphoinositide kinase inhibitors. YM201636 and PI-103 are potent inhibitors of human two-pore channel 2 that act through a channel pore entrance blockade mechanism.
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Two-pore channels: going with the flows. Biochem Soc Trans 2022; 50:1143-1155. [PMID: 35959977 PMCID: PMC9444070 DOI: 10.1042/bst20220229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 07/21/2022] [Accepted: 07/25/2022] [Indexed: 11/26/2022]
Abstract
In recent years, our understanding of the structure, mechanisms and functions of the endo-lysosomal TPC (two-pore channel) family have grown apace. Gated by the second messengers, NAADP and PI(3,5)P2, TPCs are an integral part of fundamental signal-transduction pathways, but their array and plasticity of cation conductances (Na+, Ca2+, H+) allow them to variously signal electrically, osmotically or chemically. Their relative tissue- and organelle-selective distribution, together with agonist-selective ion permeabilities provides a rich palette from which extracellular stimuli can choose. TPCs are emerging as mediators of immunity, cancer, metabolism, viral infectivity and neurodegeneration as this short review attests.
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11
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Patel S, Yuan Y, Chen CC, Jaślan D, Gunaratne G, Grimm C, Rahman T, Marchant JS. Electrophysiology of Endolysosomal Two-Pore Channels: A Current Account. Cells 2022; 11:2368. [PMID: 35954212 PMCID: PMC9368155 DOI: 10.3390/cells11152368] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 07/20/2022] [Accepted: 07/20/2022] [Indexed: 12/10/2022] Open
Abstract
Two-pore channels TPC1 and TPC2 are ubiquitously expressed pathophysiologically relevant proteins that reside on endolysosomal vesicles. Here, we review the electrophysiology of these channels. Direct macroscopic recordings of recombinant TPCs expressed in enlarged lysosomes in mammalian cells or vacuoles in plants and yeast demonstrate gating by the Ca2+-mobilizing messenger NAADP and/or the lipid PI(3,5)P2. TPC currents are regulated by H+, Ca2+, and Mg2+ (luminal and/or cytosolic), as well as protein kinases, and they are impacted by single-nucleotide polymorphisms linked to pigmentation. Bisbenzylisoquinoline alkaloids, flavonoids, and several approved drugs demonstrably block channel activity. Endogenous TPC currents have been recorded from a number of primary cell types and cell lines. Many of the properties of endolysosomal TPCs are recapitulated upon rerouting channels to the cell surface, allowing more facile recording through conventional electrophysiological means. Single-channel analyses have provided high-resolution insight into both monovalent and divalent permeability. The discovery of small-molecule activators of TPC2 that toggle the ion selectivity from a Ca2+-permeable (NAADP-like) state to a Na+-selective (PI(3,5)P2-like) state explains discrepancies in the literature relating to the permeability of TPCs. Identification of binding proteins that confer NAADP-sensitive currents confirm that indirect, remote gating likely underpins the inconsistent observations of channel activation by NAADP.
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Affiliation(s)
- Sandip Patel
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK;
| | - Yu Yuan
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK;
| | - Cheng-Chang Chen
- Department of Clinical Laboratory Sciences and Medical Biotechnology, College of Medicine, National Taiwan University, Taipei 100229, Taiwan;
- Department of Laboratory Medicine, National Taiwan University Hospital, Taipei 100225, Taiwan
| | - Dawid Jaślan
- Walther Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, Ludwig-Maximilians University, 80336 Munich, Germany; (D.J.); (C.G.)
| | - Gihan Gunaratne
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA; (G.G.); (J.S.M.)
| | - Christian Grimm
- Walther Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, Ludwig-Maximilians University, 80336 Munich, Germany; (D.J.); (C.G.)
| | - Taufiq Rahman
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, UK;
| | - Jonathan S. Marchant
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA; (G.G.); (J.S.M.)
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12
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Shah KR, Guan X, Yan J. Diversity of two-pore channels and the accessory NAADP receptors in intracellular Ca 2+ signaling. Cell Calcium 2022; 104:102594. [PMID: 35561646 PMCID: PMC9645597 DOI: 10.1016/j.ceca.2022.102594] [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: 02/02/2022] [Revised: 03/10/2022] [Accepted: 05/04/2022] [Indexed: 02/03/2023]
Abstract
Intracellular Ca2+ signaling via changes or oscillation in cytosolic Ca2+ concentration controls almost every aspect of cellular function and physiological processes, such as gene transcription, cell motility and proliferation, muscle contraction, and learning and memory. Two-pore channels (TPCs) are a class of eukaryotic cation channels involved in intracellular Ca2+ signaling, likely present in a multitude of organisms from unicellular organisms to mammals. Accumulated evidence indicates that TPCs play a critical role in Ca2+ mobilization from intracellular stores mediated by the second messenger molecule, nicotinic acid adenine dinucleotide phosphate (NAADP). In recent years, significant progress has been made regarding our understanding of the structures and function of TPCs, including Cryo-EM structure determination of mammalian TPCs and characterization of a plastid TPC in a single-celled parasite.. The recent identification of Lsm12 and JPT2 as NAADP-binding proteins provides a new molecular basis for understanding NAADP-evoked Ca2+ signaling. In this review, we summarize basic structural and functional aspects of TPCs and highlight the most recent studies on the newly discovered TPC in a parasitic protozoan and the NAADP-binding proteins LSM12 and JPT2 as new key players in NAADP signaling.
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Affiliation(s)
- Kunal R. Shah
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Xin Guan
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Jiusheng Yan
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA,Neuroscience and Biochemistry and Cell Biology Programs, The University of Texas MD Anderson Cancer Center UT Health Graduate School of Biomedical Sciences, Houston, TX, USA,Corresponding author at: Department of Anesthesiology & Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA., (J. Yan)
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13
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Martucci LL, Cancela JM. Neurophysiological functions and pharmacological tools of acidic and non-acidic Ca2+ stores. Cell Calcium 2022; 104:102582. [DOI: 10.1016/j.ceca.2022.102582] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 03/07/2022] [Accepted: 03/23/2022] [Indexed: 02/08/2023]
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14
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Gradogna A, Pardo JM, Carpaneto A. The phosphoinositide PI(3,5)P 2 inhibits the activity of plant NHX proton/potassium antiporters: Advantages of a novel electrophysiological approach. Biomol Concepts 2022; 13:119-125. [DOI: 10.1515/bmc-2022-0009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 02/22/2022] [Indexed: 11/15/2022] Open
Abstract
Abstract
In the present work, we discuss the way in which the parallel application of the patch-clamp technique and the 2′,7′-bis-(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF) fluorescence detection for recording luminal proton changes allows the functional characterization of nonelectrogenic potassium/proton vacuolar antiporters of the NHX (Na+/H+ exchanger) family. Moreover, we review the functional role of the tonoplast-specific phosphoinositide PI(3,5)P2, able to simultaneously inhibit the activity of NHXs and CLC-a transporters, whose coordinated action can play an important role in the water balance of plant cells.
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Affiliation(s)
- Antonella Gradogna
- Institute of Biophysics, National Research Council , Via De Marini 6 , 16149 Genova , Italy
| | - José M. Pardo
- Institute of Plant Biochemistry and Photosynthesis, Consejo Superior de Investigaciones Cientificas and University of Seville , Seville 41092 , Spain
| | - Armando Carpaneto
- Department of Earth, Environment and Life Sciences (DISTAV) – University of Genoa , Viale Benedetto XV 5 , 16132 Genova , Italy
- Institute of Biophysics, National Research Council , Via De Marini 6 , 16149 Genova , Italy
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15
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Current Methods to Unravel the Functional Properties of Lysosomal Ion Channels and Transporters. Cells 2022; 11:cells11060921. [PMID: 35326372 PMCID: PMC8946281 DOI: 10.3390/cells11060921] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 03/04/2022] [Accepted: 03/05/2022] [Indexed: 02/07/2023] Open
Abstract
A distinct set of channels and transporters regulates the ion fluxes across the lysosomal membrane. Malfunctioning of these transport proteins and the resulting ionic imbalance is involved in various human diseases, such as lysosomal storage disorders, cancer, as well as metabolic and neurodegenerative diseases. As a consequence, these proteins have stimulated strong interest for their suitability as possible drug targets. A detailed functional characterization of many lysosomal channels and transporters is lacking, mainly due to technical difficulties in applying the standard patch-clamp technique to these small intracellular compartments. In this review, we focus on current methods used to unravel the functional properties of lysosomal ion channels and transporters, stressing their advantages and disadvantages and evaluating their fields of applicability.
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16
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Dickinson MS, Lu J, Gupta M, Marten I, Hedrich R, Stroud RM. Molecular basis of multistep voltage activation in plant two-pore channel 1. Proc Natl Acad Sci U S A 2022; 119:e2110936119. [PMID: 35210362 PMCID: PMC8892357 DOI: 10.1073/pnas.2110936119] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 11/29/2021] [Indexed: 12/26/2022] Open
Abstract
Voltage-gated ion channels confer excitability to biological membranes, initiating and propagating electrical signals across large distances on short timescales. Membrane excitation requires channels that respond to changes in electric field and couple the transmembrane voltage to gating of a central pore. To address the mechanism of this process in a voltage-gated ion channel, we determined structures of the plant two-pore channel 1 at different stages along its activation coordinate. These high-resolution structures of activation intermediates, when compared with the resting-state structure, portray a mechanism in which the voltage-sensing domain undergoes dilation and in-membrane plane rotation about the gating charge-bearing helix, followed by charge translocation across the charge transfer seal. These structures, in concert with patch-clamp electrophysiology, show that residues in the pore mouth sense inhibitory Ca2+ and are allosterically coupled to the voltage sensor. These conformational changes provide insight into the mechanism of voltage-sensor domain activation in which activation occurs vectorially over a series of elementary steps.
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Affiliation(s)
- Miles Sasha Dickinson
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143
- Chemistry and Chemical Biology Graduate Program, University of California, San Francisco, CA 94143
| | - Jinping Lu
- Department of Molecular Plant Physiology and Biophysics, University of Würzburg, D-97082 Würzburg, Germany
| | - Meghna Gupta
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143
| | - Irene Marten
- Department of Molecular Plant Physiology and Biophysics, University of Würzburg, D-97082 Würzburg, Germany
| | - Rainer Hedrich
- Department of Molecular Plant Physiology and Biophysics, University of Würzburg, D-97082 Würzburg, Germany
| | - Robert M Stroud
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143;
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17
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Activation of endo-lysosomal two-pore channels by NAADP and PI(3,5)P2. Five things to know. Cell Calcium 2022; 103:102543. [PMID: 35123238 PMCID: PMC9552313 DOI: 10.1016/j.ceca.2022.102543] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 01/21/2022] [Accepted: 01/24/2022] [Indexed: 12/31/2022]
Abstract
Two-pore channels are ancient members of the voltage-gated ion channel superfamily that are expressed predominantly on acidic organelles such as endosomes and lysosomes. Here we review recent advances in understanding how TPCs are activated by their ligands and identify five salient features: (1) TPCs are Ca2+-permeable non-selective cation channels gated by NAADP. (2) NAADP activation is indirect through associated NAADP receptors. (3) TPCs are also Na+-selective channels gated by PI(3,5)P2. (4) PI(3,5)P2 activation is direct through a structurally-resolved binding site. (5) TPCs switch their ion selectivity in an agonist-dependent manner.
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18
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Lsm12 is an NAADP receptor and a two-pore channel regulatory protein required for calcium mobilization from acidic organelles. Nat Commun 2021; 12:4739. [PMID: 34362892 PMCID: PMC8346516 DOI: 10.1038/s41467-021-24735-z] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 07/01/2021] [Indexed: 01/19/2023] Open
Abstract
Nicotinic acid adenine dinucleotide phosphate (NAADP) is a potent Ca2+-mobilizing second messenger which uniquely mobilizes Ca2+ from acidic endolysosomal organelles. However, the molecular identity of the NAADP receptor remains unknown. Given the necessity of the endolysosomal two-pore channel (TPC1 or TPC2) in NAADP signaling, we performed affinity purification and quantitative proteomic analysis of the interacting proteins of NAADP and TPCs. We identified a Sm-like protein Lsm12 complexed with NAADP, TPC1, and TPC2. Lsm12 directly binds to NAADP via its Lsm domain, colocalizes with TPC2, and mediates the apparent association of NAADP to isolated TPC2 or TPC2-containing membranes. Lsm12 is essential and immediately participates in NAADP-evoked TPC activation and Ca2+ mobilization from acidic stores. These findings reveal a putative RNA-binding protein to function as an NAADP receptor and a TPC regulatory protein and provides a molecular basis for understanding the mechanisms of NAADP signaling. Nicotinic acid adenine dinucleotide phosphate (NAADP) potent Ca2+ mobilizing second messenger which uniquely triggers Ca2+ release from acidic endolysosomal organelles. Here the authors identify Lsm12 as an NAADP receptor essential for NAADP-evoked Ca2+ release from lysosomes via NAADP binding on its Lsm domain.
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19
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The Discovery of Naringenin as Endolysosomal Two-Pore Channel Inhibitor and Its Emerging Role in SARS-CoV-2 Infection. Cells 2021; 10:cells10051130. [PMID: 34067054 PMCID: PMC8150892 DOI: 10.3390/cells10051130] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 05/01/2021] [Accepted: 05/04/2021] [Indexed: 12/23/2022] Open
Abstract
The flavonoid naringenin (Nar), present in citrus fruits and tomatoes, has been identified as a blocker of an emerging class of human intracellular channels, namely the two-pore channel (TPC) family, whose role has been established in several diseases. Indeed, Nar was shown to be effective against neoangiogenesis, a process essential for solid tumor progression, by specifically impairing TPC activity. The goal of the present review is to illustrate the rationale that links TPC channels to the mechanism of coronavirus infection, and how their inhibition by Nar could be an efficient pharmacological strategy to fight the current pandemic plague COVID-19.
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20
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Abstract
Lysosomal calcium is emerging as a modulator of autophagy and lysosomal compartment, an obligatory partner to complete the autophagic pathway. A variety of specific signals such as nutrient deprivation or oxidative stress can trigger lysosomal calcium-mediated nuclear translocation of the transcription factor EB (TFEB), a master regulator of global lysosomal function. Also, lysosomal calcium can promote the formation of autophagosome vesicles (AVs) by a mechanism that requires the production of the phosphoinositide PI3P by the VPS34 autophagic complex and the activation of the energy-sensing kinase AMPK. Additionally, lysosomal calcium plays a role in membrane fusion and fission events involved in cellular processes such as endocytic maturation, autophagosome-lysosome fusion, lysosomal exocytosis, and lysosomal reformation upon autophagy completion. Lysosomal calcium-dependent functions are defective in cellular and animal models of the non-selective cation channel TRPML1, whose mutations in humans cause the neurodegenerative lysosomal storage disease mucolipidosis type IV (MLIV). Lysosomal calcium is not only acting as a positive regulator of autophagy, but it is also responsible for turning-off this process through the reactivation of the mTOR kinase during prolonged starvation. More recently, it has been described the role of lysosomal calcium on an elegant sequence of intracellular signaling events such as membrane repair, lysophagy, and lysosomal biogenesis upon the induction of different grades of lysosomal membrane damage. Here, we will discuss these novel findings that re-define the importance of the lysosome and lysosomal calcium signaling at regulating cellular metabolism.
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21
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Gradogna A, Scholz-Starke J, Pardo JM, Carpaneto A. Beyond the patch-clamp resolution: functional activity of nonelectrogenic vacuolar NHX proton/potassium antiporters and inhibition by phosphoinositides. THE NEW PHYTOLOGIST 2021; 229:3026-3036. [PMID: 33098586 DOI: 10.1111/nph.17021] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 10/12/2020] [Indexed: 05/12/2023]
Abstract
We combined the patch-clamp technique with ratiometric fluorescence imaging using the proton-responsive dye BCECF as a luminal probe. Upon application of a steep cytosol-directed potassium ion (K+ ) gradient in Arabidopsis mesophyll vacuoles, a strong and reversible acidification of the vacuolar lumen was detected, whereas no associated electrical currents were observed, in agreement with electroneutral cation/H+ exchange. Our data show that this acidification was generated by NHX antiport activity, because: it did not distinguish between K+ and sodium (Na+ ) ions; it was sensitive to the NHX inhibitor benzamil; and it was completely absent in vacuoles from nhx1 nhx2 double knockout plants. Our data further show that NHX activity could be reversed, was voltage-independent and specifically impaired by the low-abundance signaling lipid PI(3,5)P2 , which may regulate salt accumulation in plants by acting as a common messenger to coordinately shut down secondary active carriers responsible for cation and anion uptake inside the vacuole. Finally, we developed a theory based on thermodynamics, which supports the data obtained by our novel experimental approach. This work, therefore, represents a proof-of-principle that can be applied to the study of proton-dependent exchangers from plants and animals, which are barely detectable using conventional techniques.
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Affiliation(s)
- Antonella Gradogna
- Institute of Biophysics, National Research Council, Via De Marini 6, Genova, 16149, Italy
| | - Joachim Scholz-Starke
- Institute of Biophysics, National Research Council, Via De Marini 6, Genova, 16149, Italy
| | - José M Pardo
- Institute of Plant Biochemistry and Photosynthesis, CSIC-University of Seville, Seville, 41092, Spain
| | - Armando Carpaneto
- Institute of Biophysics, National Research Council, Via De Marini 6, Genova, 16149, Italy
- Department of Earth, Environment and Life Sciences (DISTAV), University of Genoa, Viale Benedetto XV 5, Genova, 16132, Italy
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22
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Abstract
Lysosomes offer a unique arrangement of degradative, exocytic, and signaling capabilities that make their continued function critical to cellular homeostasis. Lysosomes owe their function to the activity of lysosomal ion channels and transporters, which maintain concentration gradients of H+, K+, Ca2+, Na+, and Cl- across the lysosomal membrane. This review examines the contributions of lysosomal ion channels to lysosome function, showing how ion channel function is integral to degradation and autophagy, maintaining lysosomal membrane potential, controlling Ca2+ signaling, and facilitating exocytosis. Evidence of lysosome dysfunction in a variety of disease pathologies creates a need to understand how lysosomal ion channels contribute to lysosome dysfunction. For example, the loss of function of the TRPML1 Ca2+ lysosome channel in multiple lysosome storage diseases leads to lysosome dysfunction and disease pathogenesis while neurodegenerative diseases are marked by lysosome dysfunction caused by changes in ion channel activity through the TRPML1, TPC, and TMEM175 ion channels. Autoimmune disease is marked by dysregulated autophagy, which is dependent on the function of multiple lysosomal ion channels. Understanding the role of lysosomal ion channel activity in lysosome membrane permeability and NLRP3 inflammasome activation could provide valuable mechanistic insight into NLRP3 inflammasome-mediated diseases. Finally, this review seeks to show that understanding the role of lysosomal ion channels in lysosome dysfunction could give mechanistic insight into the efficacy of certain drug classes, specifically those that target the lysosome, such as cationic amphiphilic drugs.
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Affiliation(s)
- Rebekah L Kendall
- Department of Biomedical and Pharmaceutical Sciences, Center for Environmental Health Sciences, University of Montana, Missoula, MT, USA
| | - Andrij Holian
- Department of Biomedical and Pharmaceutical Sciences, Center for Environmental Health Sciences, University of Montana, Missoula, MT, USA
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23
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Cremer T, Neefjes J, Berlin I. The journey of Ca 2+ through the cell - pulsing through the network of ER membrane contact sites. J Cell Sci 2020; 133:133/24/jcs249136. [PMID: 33376155 DOI: 10.1242/jcs.249136] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Calcium is the third most abundant metal on earth, and the fundaments of its homeostasis date back to pre-eukaryotic life forms. In higher organisms, Ca2+ serves as a cofactor for a wide array of (enzymatic) interactions in diverse cellular contexts and constitutes the most important signaling entity in excitable cells. To enable responsive behavior, cytosolic Ca2+ concentrations are kept low through sequestration into organellar stores, particularly the endoplasmic reticulum (ER), but also mitochondria and lysosomes. Specific triggers are then used to instigate a local release of Ca2+ on demand. Here, communication between organelles comes into play, which is accomplished through intimate yet dynamic contacts, termed membrane contact sites (MCSs). The field of MCS biology in relation to cellular Ca2+ homeostasis has exploded in recent years. Taking advantage of this new wealth of knowledge, in this Review, we invite the reader on a journey of Ca2+ flux through the ER and its associated MCSs. New mechanistic insights and technological advances inform the narrative on Ca2+ acquisition and mobilization at these sites of communication between organelles, and guide the discussion of their consequences for cellular physiology.
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Affiliation(s)
- Tom Cremer
- Department of Cell and Chemical Biology, Leiden University Medical Center LUMC, Einthovenweg 20, 2300RC Leiden, The Netherlands
| | - Jacques Neefjes
- Department of Cell and Chemical Biology, Leiden University Medical Center LUMC, Einthovenweg 20, 2300RC Leiden, The Netherlands
| | - Ilana Berlin
- Department of Cell and Chemical Biology, Leiden University Medical Center LUMC, Einthovenweg 20, 2300RC Leiden, The Netherlands
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24
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Khan N, Chen X, Geiger JD. Role of Endolysosomes in Severe Acute Respiratory Syndrome Coronavirus-2 Infection and Coronavirus Disease 2019 Pathogenesis: Implications for Potential Treatments. Front Pharmacol 2020; 11:595888. [PMID: 33324224 PMCID: PMC7723437 DOI: 10.3389/fphar.2020.595888] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 10/05/2020] [Indexed: 12/14/2022] Open
Abstract
Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is an enveloped, single-stranded RNA virus. Humans infected with SARS-CoV-2 develop a disease known as coronavirus disease 2019 (COVID-19) with symptoms and consequences including acute respiratory distress syndrome (ARDS), cardiovascular disorders, and death. SARS-CoV-2 appears to infect cells by first binding viral spike proteins with host protein angiotensin-converting enzyme 2 (ACE2) receptors; the virus is endocytosed following priming by transmembrane protease serine 2 (TMPRSS2). The process of virus entry into endosomes and its release from endolysosomes are key features of enveloped viruses. Thus, it is important to focus attention on the role of endolysosomes in SARS-CoV-2 infection. Indeed, coronaviruses are now known to hijack endocytic machinery to enter cells such that they can deliver their genome at replication sites without initiating host detection and immunological responses. Hence, endolysosomes might be good targets for developing therapeutic strategies against coronaviruses. Here, we focus attention on the involvement of endolysosomes in SARS-CoV-2 infection and COVID-19 pathogenesis. Further, we explore endolysosome-based therapeutic strategies to restrict SARS-CoV-2 infection and COVID-19 pathogenesis.
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Affiliation(s)
| | | | - Jonathan D. Geiger
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND, United States
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25
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Milenkovic S, Bodrenko IV, Lagostena L, Gradogna A, Serra G, Bosin A, Carpaneto A, Ceccarelli M. The mechanism and energetics of a ligand-controlled hydrophobic gate in a mammalian two pore channel. Phys Chem Chem Phys 2020; 22:15664-15674. [PMID: 32618303 DOI: 10.1039/d0cp00805b] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
In the last decade two-pore intracellular channels (TPCs) attracted the interest of researchers, still some key questions remain open. Their importance for vacuolar (plants) and endo-lysosomal (animals) function highlights them as a very attractive system to study, both theoretically and experimentally. Indicated as key players in the trafficking of the cell, today they are considered a new potential target for avoiding virus infections, including those from coronaviruses. A particular boost for theoretical examinations has been made with recent high-resolution X-ray and cryo-EM structures. These findings have opened the way for efficient and precise computational studies at the atomistic level. Here we report a set of multiscale-calculations performed on the mTPC1, a ligand- and voltage-gated sodium selective channel. The molecular dynamics and enhanced molecular dynamics simulations were used for a thorough analysis of the mammalian TPC1 behaviour in the presence and absence of the ligand molecule, with a special accent on the supposed bottleneck, the hydrophobic gate. Moreover, from the reconstructed free energy obtained from enhanced simulations, we have calculated the macroscopic conductance of sodium ions through the mTPC1, which we compared with measured single-channel conductance values. The hydrophobic gate works as a steric barrier and the key parameters are its flexibility and the dimension of the sodium first hydration shell.
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Affiliation(s)
- Stefan Milenkovic
- Department of Physics and IOM/CNR, University of Cagliari, 09042 Monserrato, Italy.
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26
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Moccia F, Zuccolo E, Di Nezza F, Pellavio G, Faris PS, Negri S, De Luca A, Laforenza U, Ambrosone L, Rosti V, Guerra G. Nicotinic acid adenine dinucleotide phosphate activates two-pore channel TPC1 to mediate lysosomal Ca 2+ release in endothelial colony-forming cells. J Cell Physiol 2020; 236:688-705. [PMID: 32583526 DOI: 10.1002/jcp.29896] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 06/08/2020] [Accepted: 06/12/2020] [Indexed: 12/15/2022]
Abstract
Nicotinic acid adenine dinucleotide phosphate (NAADP) is the most recently discovered Ca2+ -releasing messenger that increases the intracellular Ca2+ concentration by mobilizing the lysosomal Ca2+ store through two-pore channels 1 (TPC1) and 2 (TPC2). NAADP-induced lysosomal Ca2+ release regulates multiple endothelial functions, including nitric oxide release and proliferation. A sizeable acidic Ca2+ pool endowed with TPC1 is also present in human endothelial colony-forming cells (ECFCs), which represent the only known truly endothelial precursors. Herein, we sought to explore the role of the lysosomal Ca2+ store and TPC1 in circulating ECFCs by harnessing Ca2+ imaging and molecular biology techniques. The lysosomotropic agent, Gly-Phe β-naphthylamide, and nigericin, which dissipates the proton gradient which drives Ca2+ sequestration by acidic organelles, caused endogenous Ca2+ release in the presence of a replete inositol-1,4,5-trisphosphate (InsP3 )-sensitive endoplasmic reticulum (ER) Ca2+ pool. Likewise, the amount of ER releasable Ca2+ was reduced by disrupting lysosomal Ca2+ content. Liposomal delivery of NAADP induced a transient Ca2+ signal that was abolished by disrupting the lysosomal Ca2+ store and by pharmacological and genetic blockade of TPC1. Pharmacological manipulation revealed that NAADP-induced Ca2+ release also required ER-embedded InsP3 receptors. Finally, NAADP-induced lysosomal Ca2+ release was found to trigger vascular endothelial growth factor-induced intracellular Ca2+ oscillations and proliferation, while it did not contribute to adenosine-5'-trisphosphate-induced Ca2+ signaling. These findings demonstrated that NAADP-induced TPC1-mediated Ca2+ release can selectively be recruited to induce the Ca2+ response to specific cues in circulating ECFCs.
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Affiliation(s)
- Francesco Moccia
- Department of Biology and Biotechnology, Laboratory of General Physiology, University of Pavia, Pavia, Italy
| | - Estella Zuccolo
- Department of Biology and Biotechnology, Laboratory of General Physiology, University of Pavia, Pavia, Italy
| | - Francesca Di Nezza
- Department of Medicine and Health Sciences "Vincenzo Tiberio", University of Molise, Campobasso, Italy
| | - Giorgia Pellavio
- Human Physiology Unit, Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Pawan S Faris
- Department of Biology and Biotechnology, Laboratory of General Physiology, University of Pavia, Pavia, Italy
| | - Sharon Negri
- Department of Biology and Biotechnology, Laboratory of General Physiology, University of Pavia, Pavia, Italy
| | - Antonio De Luca
- Department of Mental and Physical Health and Preventive Medicine, University of Campania Luigi Vanvitelli, Naples, Italy
| | - Umberto Laforenza
- Human Physiology Unit, Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Luigi Ambrosone
- Department of Medicine and Health Sciences "Vincenzo Tiberio", University of Molise, Campobasso, Italy
| | - Vittorio Rosti
- Laboratory of Biochemistry Biotechnology and Advanced Diagnostic, Myelofibrosis Study Centre, IRCCS Ospedale Policlinico San Matteo, Pavia, Italy
| | - Germano Guerra
- Department of Medicine and Health Sciences "Vincenzo Tiberio", University of Molise, Campobasso, Italy
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27
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Evolutionary Aspects of TRPMLs and TPCs. Int J Mol Sci 2020; 21:ijms21114181. [PMID: 32545371 PMCID: PMC7312350 DOI: 10.3390/ijms21114181] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 06/05/2020] [Accepted: 06/10/2020] [Indexed: 01/02/2023] Open
Abstract
Transient receptor potential (TRP) or transient receptor potential channels are a highly diverse family of mostly non-selective cation channels. In the mammalian genome, 28 members can be identified, most of them being expressed predominantly in the plasma membrane with the exception of the mucolipins or TRPMLs which are expressed in the endo-lysosomal system. In mammalian organisms, TRPMLs have been associated with a number of critical endo-lysosomal functions such as autophagy, endo-lysosomal fusion/fission and trafficking, lysosomal exocytosis, pH regulation, or lysosomal motility and positioning. The related non-selective two-pore cation channels (TPCs), likewise expressed in endosomes and lysosomes, have also been found to be associated with endo-lysosomal trafficking, autophagy, pH regulation, or lysosomal exocytosis, raising the question why these two channel families have evolved independently. We followed TRP/TRPML channels and TPCs through evolution and describe here in which species TRP/TRPMLs and/or TPCs are found, which functions they have in different species, and how this compares to the functions of mammalian orthologs.
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Filippini A, D'Amore A, Palombi F, Carpaneto A. Could the Inhibition of Endo-Lysosomal Two-Pore Channels (TPCs) by the Natural Flavonoid Naringenin Represent an Option to Fight SARS-CoV-2 Infection? Front Microbiol 2020; 11:970. [PMID: 32425923 PMCID: PMC7204543 DOI: 10.3389/fmicb.2020.00970] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 04/22/2020] [Indexed: 01/12/2023] Open
Affiliation(s)
- Antonio Filippini
- Unit of Histology and Medical Embryology, Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, SAPIENZA University of Rome, Rome, Italy
| | - Antonella D'Amore
- Unit of Histology and Medical Embryology, Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, SAPIENZA University of Rome, Rome, Italy
| | - Fioretta Palombi
- Unit of Histology and Medical Embryology, Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, SAPIENZA University of Rome, Rome, Italy
| | - Armando Carpaneto
- Department of Earth, Environment and Life Sciences (DISTAV), University of Genoa, Genoa, Italy.,Institute of Biophysics, National Research Council, Genoa, Italy
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Khan N, Halcrow PW, Lakpa KL, Afghah Z, Miller NM, Dowdy SF, Geiger JD, Chen X. Two-pore channels regulate Tat endolysosome escape and Tat-mediated HIV-1 LTR transactivation. FASEB J 2020; 34:4147-4162. [PMID: 31950548 PMCID: PMC7079041 DOI: 10.1096/fj.201902534r] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Revised: 12/10/2019] [Accepted: 01/02/2020] [Indexed: 12/25/2022]
Abstract
HIV‐1 Tat is essential for HIV‐1 replication and appears to play an important role in the pathogenesis of HIV‐associated neurological complications. Secreted from infected or transfected cells, Tat has the extraordinary ability to cross the plasma membrane. In the brain, Tat can be taken up by CNS cells via receptor‐mediated endocytosis. Following endocytosis and its internalization into endolysosomes, Tat must be released in order for it to activate the HIV‐1 LTR promoter and facilitate HIV‐1 viral replication in the nucleus. However, the underlying mechanisms whereby Tat escapes endolysosomes remain unclear. Because Tat disrupts intracellular calcium homeostasis, we investigated the involvement of calcium in Tat endolysosome escape and subsequent LTR transactivation. We demonstrated that chelating endolysosome calcium with high‐affinity rhodamine‐dextran or chelating cytosolic calcium with BAPTA‐AM attenuated Tat endolysosome escape and LTR transactivation. Significantly, we demonstrated that pharmacologically blocking and knocking down the endolysosome‐resident two‐pore channels (TPCs) attenuated Tat endolysosome escape and LTR transactivation. This calcium‐mediated effect appears to be selective for TPCs because knocking down TRPML1 calcium channels was without effect. Our findings suggest that calcium released from TPCs is involved in Tat endolysosome escape and subsequent LTR transactivation. TPCs might represent a novel therapeutic target against HIV‐1 infection and HIV‐associated neurological complications.
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Affiliation(s)
- Nabab Khan
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND, USA
| | - Peter W Halcrow
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND, USA
| | - Koffi L Lakpa
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND, USA
| | - Zahra Afghah
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND, USA
| | - Nicole M Miller
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND, USA
| | - Steven F Dowdy
- Department of Cellular and Molecular Medicine, University of California San Diego (UCSD) School of Medicine, La Jolla, CA, USA
| | - Jonathan D Geiger
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND, USA
| | - Xuesong Chen
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND, USA
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30
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A perspective on the modulation of plant and animal two pore channels (TPCs) by the flavonoid naringenin. Biophys Chem 2019; 254:106246. [PMID: 31426023 DOI: 10.1016/j.bpc.2019.106246] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2019] [Revised: 08/03/2019] [Accepted: 08/03/2019] [Indexed: 12/17/2022]
Abstract
The inhibitory effect of the flavonoid naringenin on plant and human Two-Pore Channels (TPCs) was assessed by means of electrophysiological measurements. By acting on human TPC2, naringenin, was able to dampen intracellular calcium responses to VEGF in cultured human endothelial cells and to impair angiogenic activity in VEGF-containing matrigel plugs implanted in mice. Molecular docking predicts selective binding sites for naringenin in the TPC structure, thus suggesting a specific interaction between the flavonoid and the channel.
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31
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Abdul Kadir L, Stacey M, Barrett-Jolley R. Emerging Roles of the Membrane Potential: Action Beyond the Action Potential. Front Physiol 2018; 9:1661. [PMID: 30519193 PMCID: PMC6258788 DOI: 10.3389/fphys.2018.01661] [Citation(s) in RCA: 116] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Accepted: 11/02/2018] [Indexed: 01/03/2023] Open
Abstract
Whilst the phenomenon of an electrical resting membrane potential (RMP) is a central tenet of biology, it is nearly always discussed as a phenomenon that facilitates the propagation of action potentials in excitable tissue, muscle, and nerve. However, as ion channel research shifts beyond these tissues, it became clear that the RMP is a feature of virtually all cells studied. The RMP is maintained by the cell’s compliment of ion channels. Transcriptome sequencing is increasingly revealing that equally rich compliments of ion channels exist in both excitable and non-excitable tissue. In this review, we discuss a range of critical roles that the RMP has in a variety of cell types beyond the action potential. Whereas most biologists would perceive that the RMP is primarily about excitability, the data show that in fact excitability is only a small part of it. Emerging evidence show that a dynamic membrane potential is critical for many other processes including cell cycle, cell-volume control, proliferation, muscle contraction (even in the absence of an action potential), and wound healing. Modulation of the RMP is therefore a potential target for many new drugs targeting a range of diseases and biological functions from cancer through to wound healing and is likely to be key to the development of successful stem cell therapies.
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Affiliation(s)
- Lina Abdul Kadir
- Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom
| | - Michael Stacey
- Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA, United States
| | - Richard Barrett-Jolley
- Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom
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Demidchik V, Shabala S, Isayenkov S, Cuin TA, Pottosin I. Calcium transport across plant membranes: mechanisms and functions. THE NEW PHYTOLOGIST 2018; 220:49-69. [PMID: 29916203 DOI: 10.1111/nph.15266] [Citation(s) in RCA: 191] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 04/21/2018] [Indexed: 05/20/2023]
Abstract
Contents Summary 49 I. Introduction 49 II. Physiological and structural characteristics of plant Ca2+ -permeable ion channels 50 III. Ca2+ extrusion systems 61 IV. Concluding remarks 64 Acknowledgements 64 References 64 SUMMARY: Calcium is an essential structural, metabolic and signalling element. The physiological functions of Ca2+ are enabled by its orchestrated transport across cell membranes, mediated by Ca2+ -permeable ion channels, Ca2+ -ATPases and Ca2+ /H+ exchangers. Bioinformatics analysis has not determined any Ca2+ -selective filters in plant ion channels, but electrophysiological tests do reveal Ca2+ conductances in plant membranes. The biophysical characteristics of plant Ca2+ conductances have been studied in detail and were recently complemented by molecular genetic approaches. Plant Ca2+ conductances are mediated by several families of ion channels, including cyclic nucleotide-gated channels (CNGCs), ionotropic glutamate receptors, two-pore channel 1 (TPC1), annexins and several types of mechanosensitive channels. Key Ca2+ -mediated reactions (e.g. sensing of temperature, gravity, touch and hormones, and cell elongation and guard cell closure) have now been associated with the activities of specific subunits from these families. Structural studies have demonstrated a unique selectivity filter in TPC1, which is passable for hydrated divalent cations. The hypothesis of a ROS-Ca2+ hub is discussed, linking Ca2+ transport to ROS generation. CNGC inactivation by cytosolic Ca2+ , leading to the termination of Ca2+ signals, is now mechanistically explained. The structure-function relationships of Ca2+ -ATPases and Ca2+ /H+ exchangers, and their regulation and physiological roles are analysed.
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Affiliation(s)
- Vadim Demidchik
- Department of Horticulture, Foshan University, Foshan, 528000, China
- Department of Plant Cell Biology and Bioengineering, Biological Faculty, Belarusian State University, 4 Independence Avenue, Minsk, 220030, Belarus
- Komarov Botanical Institute, Russian Academy of Sciences, 2 Professora Popova Street, St Petersburg, 197376, Russia
| | - Sergey Shabala
- Department of Horticulture, Foshan University, Foshan, 528000, China
- Tasmanian Institute of Agriculture, University of Tasmania, Private Bag 54, Hobart, Tas, 7001, Australia
| | - Stanislav Isayenkov
- Institute of Food Biotechnology and Genomics, National Academy of Science of Ukraine, 2a Osipovskogo Street, Kyiv, 04123, Ukraine
| | - Tracey A Cuin
- Tasmanian Institute of Agriculture, University of Tasmania, Private Bag 54, Hobart, Tas, 7001, Australia
| | - Igor Pottosin
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Avenida 25 de julio 965, Colima, 28045, Mexico
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33
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Kirsch SA, Kugemann A, Carpaneto A, Böckmann RA, Dietrich P. Phosphatidylinositol-3,5-bisphosphate lipid-binding-induced activation of the human two-pore channel 2. Cell Mol Life Sci 2018; 75:3803-3815. [PMID: 29705952 PMCID: PMC11105763 DOI: 10.1007/s00018-018-2829-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Revised: 03/29/2018] [Accepted: 04/23/2018] [Indexed: 11/24/2022]
Abstract
Mammalian two-pore channels (TPCs) are activated by the low-abundance membrane lipid phosphatidyl-(3,5)-bisphosphate (PI(3,5)P2) present in the endo-lysosomal system. Malfunction of human TPC1 or TPC2 (hTPC) results in severe organellar storage diseases and membrane trafficking defects. Here, we compared the lipid-binding characteristics of hTPC2 and of the PI(3,5)P2-insensitive TPC1 from the model plant Arabidopsis thaliana. Combination of simulations with functional analysis of channel mutants revealed the presence of an hTPC2-specific lipid-binding pocket mutually formed by two channel regions exposed to the cytosolic side of the membrane. We showed that PI(3,5)P2 is simultaneously stabilized by positively charged amino acids (K203, K204, and K207) in the linker between transmembrane helices S4 and S5 and by S322 in the cytosolic extension of S6. We suggest that PI(3,5)P2 cross links two parts of the channel, enabling their coordinated movement during channel gating.
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Affiliation(s)
- Sonja A Kirsch
- Computational Biology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Andreas Kugemann
- Molecular Plant Physiology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Armando Carpaneto
- Institute of Biophysics, National Research Council, Genoa, Italy
- Department of Earth, Environment and Life Sciences-DISTAV, University of Genoa, Genoa, Italy
| | - Rainer A Böckmann
- Computational Biology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany.
| | - Petra Dietrich
- Molecular Plant Physiology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany.
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Böhm J, Messerer M, Müller HM, Scholz-Starke J, Gradogna A, Scherzer S, Maierhofer T, Bazihizina N, Zhang H, Stigloher C, Ache P, Al-Rasheid KAS, Mayer KFX, Shabala S, Carpaneto A, Haberer G, Zhu JK, Hedrich R. Understanding the Molecular Basis of Salt Sequestration in Epidermal Bladder Cells of Chenopodium quinoa. Curr Biol 2018; 28:3075-3085.e7. [PMID: 30245105 DOI: 10.1016/j.cub.2018.08.004] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 06/20/2018] [Accepted: 08/01/2018] [Indexed: 02/03/2023]
Abstract
Soil salinity is destroying arable land and is considered to be one of the major threats to global food security in the 21st century. Therefore, the ability of naturally salt-tolerant halophyte plants to sequester large quantities of salt in external structures, such as epidermal bladder cells (EBCs), is of great interest. Using Chenopodium quinoa, a pseudo-cereal halophyte of great economic potential, we have shown previously that, upon removal of salt bladders, quinoa becomes salt sensitive. In this work, we analyzed the molecular mechanism underlying the unique salt dumping capabilities of bladder cells in quinoa. The transporters differentially expressed in the EBC transcriptome and functional electrophysiological testing of key EBC transporters in Xenopus oocytes revealed that loading of Na+ and Cl- into EBCs is mediated by a set of tailored plasma and vacuole membrane-based sodium-selective channel and chloride-permeable transporter.
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Affiliation(s)
- Jennifer Böhm
- Tasmanian Institute for Agriculture, College of Science and Engineering, University of Tasmania, Private Bag 54, Hobart, TAS 7001, Australia
| | - Maxim Messerer
- Plant Genome and Systems Biology, Helmholtz Center Munich, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany
| | - Heike M Müller
- Institute for Molecular Plant Physiology and Biophysics, University of Wuerzburg, Julius-von-Sachs Platz 2, 97082 Wuerzburg, Germany
| | - Joachim Scholz-Starke
- Institute of Biophysics, National Research Council (CNR), Via De Marini 6, 16149 Genova, Italy
| | - Antonella Gradogna
- Institute of Biophysics, National Research Council (CNR), Via De Marini 6, 16149 Genova, Italy
| | - Sönke Scherzer
- Institute for Molecular Plant Physiology and Biophysics, University of Wuerzburg, Julius-von-Sachs Platz 2, 97082 Wuerzburg, Germany
| | - Tobias Maierhofer
- Institute for Molecular Plant Physiology and Biophysics, University of Wuerzburg, Julius-von-Sachs Platz 2, 97082 Wuerzburg, Germany
| | - Nadia Bazihizina
- Tasmanian Institute for Agriculture, College of Science and Engineering, University of Tasmania, Private Bag 54, Hobart, TAS 7001, Australia; Department of Agrifood Production and Environmental Sciences, Università degli Studi di Firenze, Viale delle Idee 30, 50019 Sesto Fiorentino, Florence, Italy
| | - Heng Zhang
- Shanghai Center for Plant Stress Biology, and CAS Center for Excellence in Molecular Plant Sciences, 3888 Chenhua Road, Shanghai 201602, China
| | - Christian Stigloher
- Imaging Core Facility, Biocenter, University of Wuerzburg, Am Hubland, 97074 Wuerzburg, Germany
| | - Peter Ache
- Institute for Molecular Plant Physiology and Biophysics, University of Wuerzburg, Julius-von-Sachs Platz 2, 97082 Wuerzburg, Germany
| | - Khaled A S Al-Rasheid
- Zoology Department, College of Science, King Saud University, PO Box 2455, Riyadh 11451, Saudi Arabia
| | - Klaus F X Mayer
- Plant Genome and Systems Biology, Helmholtz Center Munich, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany
| | - Sergey Shabala
- Tasmanian Institute for Agriculture, College of Science and Engineering, University of Tasmania, Private Bag 54, Hobart, TAS 7001, Australia; Department of Horticulture, Foshan University, Foshan 528000, PRC
| | - Armando Carpaneto
- Institute of Biophysics, National Research Council (CNR), Via De Marini 6, 16149 Genova, Italy; Department of Earth, Environment and Life Sciences (DISTAV), University of Genoa, Viale Benedetto XV 5, 16132 Genova, Italy
| | - Georg Haberer
- Plant Genome and Systems Biology, Helmholtz Center Munich, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany.
| | - Jian-Kang Zhu
- Shanghai Center for Plant Stress Biology, and CAS Center for Excellence in Molecular Plant Sciences, 3888 Chenhua Road, Shanghai 201602, China; Department of Horticulture and Landscape Architecture, Purdue University, 625 Agriculture Mall Drive, West Lafayette, IN 47907, USA.
| | - Rainer Hedrich
- Institute for Molecular Plant Physiology and Biophysics, University of Wuerzburg, Julius-von-Sachs Platz 2, 97082 Wuerzburg, Germany.
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Hedrich R, Mueller TD, Becker D, Marten I. Structure and Function of TPC1 Vacuole SV Channel Gains Shape. MOLECULAR PLANT 2018; 11:764-775. [PMID: 29614320 DOI: 10.1016/j.molp.2018.03.017] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 03/12/2018] [Accepted: 03/22/2018] [Indexed: 05/20/2023]
Abstract
Plants and animals in endosomes operate TPC1/SV-type cation channels. All plants harbor at least one TPC1 gene. Although the encoded SV channel was firstly discovered in the plant vacuole membrane two decades ago, its biological function has remained enigmatic. Recently, the structure of a plant TPC1/SV channel protein was determined. Insights into the 3D topology has now guided site-directed mutation approaches, enabling structure-function analyses of TPC1/SV channels to shed new light on earlier findings. Fou2 plants carrying a hyperactive mutant form of TPC1 develop wounding stress phenotypes. Recent studies with fou2 and mutants that lack functional TPC1 have revealed atypical features in local and long-distance stress signaling, providing new access to the previously mysterious biology of this vacuolar cation channel type in planta.
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Affiliation(s)
- Rainer Hedrich
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Platz 2, 97082 Würzburg, Germany.
| | - Thomas D Mueller
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Platz 2, 97082 Würzburg, Germany
| | - Dirk Becker
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Platz 2, 97082 Würzburg, Germany
| | - Irene Marten
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Platz 2, 97082 Würzburg, Germany
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36
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Carpaneto A, Gradogna A. Modulation of calcium and potassium permeation in plant TPC channels. Biophys Chem 2018; 236:1-7. [PMID: 29486387 DOI: 10.1016/j.bpc.2018.02.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2018] [Revised: 02/20/2018] [Accepted: 02/20/2018] [Indexed: 01/01/2023]
Abstract
Plant two-pore channels (TPCs) are non-selective cation channels permeable both to monovalent potassium and divalent calcium. We previously developed a technique that allowed the simultaneous determination of the fluxes of these two ions across the channel by a combined use of patch-clamp and fluorescence. In this paper we studied how potassium and calcium fluxes were influenced by modification of cytosolic concentrations of K+ and Ca2+. A decrease in cytosolic calcium from 2 to 0.5 mM led to a shift of the activation curve of about +60 mV; although at positive potentials currents were very similar, calcium ion permeation was significantly reduced and the ratio between the total and calcium-mediated current increased about two-fold. Upon removal of cytosolic potassium, in the presence of 2 mM cytosolic calcium, the voltage-dependent activation curve was not modified but a dramatic reduction of the currents at positive voltages was apparent. However, calcium permeation did not change significantly in this condition. This work demonstrated that the electrophysiological measurements alone were not capable to predict the extent of the flow of different ions through cation channels. The parallel use of calcium detection by fluorescent dyes proved to be a valuable tool for the correct quantification of the permeation mechanisms in non-selective ion channels.
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Affiliation(s)
- Armando Carpaneto
- Department of Earth, Environment and Life Sciences (DISTAV), University of Genoa, Viale Benedetto XV 5, 16132 Genova, Italy; Institute of Biophysics, CNR, Via De Marini 6, 16149 Genova, Italy.
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37
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Hamamoto S, Mori Y, Yabe I, Uozumi N. In vitro and in vivo characterization of modulation of the vacuolar cation channel TRPY1 from Saccharomyces cerevisiae. FEBS J 2018; 285:1146-1161. [PMID: 29405580 DOI: 10.1111/febs.14399] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Revised: 11/29/2017] [Accepted: 01/30/2018] [Indexed: 01/08/2023]
Abstract
Saccharomyces cerevisiae possesses a transient receptor potential (TRP) channel homolog TRPY1 in its vacuolar membrane, considered to be an ancestral TRP channel. So far, studies have focused on the channel properties of TRPY1, but its regulation and physiologic role remained to be elucidated. Here, we investigated TRPY1 channel function in vitro and in vivo. Patch-clamp recording of TRPY1 in yeast vacuolar membranes showed that Ca2+ on the lumen side inhibited TRPY1-mediated channel activity, whereas luminal Zn2+ increased the currents. TRPY1 was activated in the presence of a reducing agent, 2-mercaptoethanol. The cysteine at position 624 was identified as the target for this activating action. This activation was independent of the presence of cytosolic Ca2+ . The amplitude of TRPY1-mediated current was reduced by addition of phosphatidylinositol 3-phosphate on the cytosolic side but not by phosphatidylinositol (PI) or phosphatidylinositol 3,5-phosphate. Measurement of the transient Ca2+ increase in response to hyper-osmotic shock in several yeast mutants defective in different steps of the PI phosphate biogenesis pathway supported this interpretation. Addition of a microtubule inhibitor strongly decreased the transient cytosolic Ca2+ increase upon hyper-osmotic shock. Taken together, the data indicate that the vacuolar TRPY1 Ca2+ channel mediates the perception of cytosolic signals that were induced by external changes in osmolarity, and participates in the modulation of cytosolic calcium signaling through Ca2+ release from the vacuole to maintain intracellular Ca2+ homeostasis in yeast.
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Affiliation(s)
- Shin Hamamoto
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan
| | - Yasuo Mori
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Japan
| | - Isamu Yabe
- Department of Green and Sustainable Chemistry, Tokyo Denki University, Japan
| | - Nobuyuki Uozumi
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan
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Hilgemann DW, Dai G, Collins A, Lariccia V, Magi S, Deisl C, Fine M. Lipid signaling to membrane proteins: From second messengers to membrane domains and adapter-free endocytosis. J Gen Physiol 2018; 150:211-224. [PMID: 29326133 PMCID: PMC5806671 DOI: 10.1085/jgp.201711875] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Hilgemann et al. explain how lipid signaling to membrane proteins involves a hierarchy of mechanisms from lipid binding to membrane domain coalescence. Lipids influence powerfully the function of ion channels and transporters in two well-documented ways. A few lipids act as bona fide second messengers by binding to specific sites that control channel and transporter gating. Other lipids act nonspecifically by modifying the physical environment of channels and transporters, in particular the protein–membrane interface. In this short review, we first consider lipid signaling from this traditional viewpoint, highlighting innumerable Journal of General Physiology publications that have contributed to our present understanding. We then switch to our own emerging view that much important lipid signaling occurs via the formation of membrane domains that influence the function of channels and transporters within them, promote selected protein–protein interactions, and control the turnover of surface membrane.
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Affiliation(s)
- Donald W Hilgemann
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Gucan Dai
- Department of Physiology and Biophysics, University of Washington, Seattle, WA
| | - Anthony Collins
- Saba University School of Medicine, The Bottom, Saba, Dutch Caribbean
| | - Vincenzo Lariccia
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche," Ancona, Italy
| | - Simona Magi
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche," Ancona, Italy
| | - Christine Deisl
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Michael Fine
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX
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Lenglet A, Jaślan D, Toyota M, Mueller M, Müller T, Schönknecht G, Marten I, Gilroy S, Hedrich R, Farmer EE. Control of basal jasmonate signalling and defence through modulation of intracellular cation flux capacity. THE NEW PHYTOLOGIST 2017; 216:1161-1169. [PMID: 28885692 DOI: 10.1111/nph.14754] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Accepted: 07/19/2017] [Indexed: 05/24/2023]
Abstract
Unknown mechanisms tightly regulate the basal activity of the wound-inducible defence mediator jasmonate (JA) in undamaged tissues. However, the Arabidopsis fatty acid oxygenation upregulated2 (fou2) mutant in vacuolar two-pore channel 1 (TPC1D454N ) displays high JA pathway activity in undamaged leaves. This mutant was used to explore mechanisms controlling basal JA pathway regulation. fou2 was re-mutated to generate novel 'ouf' suppressor mutants. Patch-clamping was used to examine TPC1 cation channel characteristics in the ouf suppressor mutants and in fou2. Calcium (Ca2+ ) imaging was used to study the effects fou2 on cytosolic Ca2+ concentrations. Six intragenic ouf suppressors with near wild-type (WT) JA pathway activity were recovered and one mutant, ouf8, affected the channel pore. At low luminal calcium concentrations, ouf8 had little detectable effect on fou2. However, increased vacuolar Ca2+ concentrations caused channel occlusion, selectively blocking K+ fluxes towards the cytoplasm. Cytosolic Ca2+ concentrations in unwounded fou2 were found to be lower than in the unwounded WT, but they increased in a similar manner in both genotypes following wounding. Basal JA pathway activity can be controlled solely by manipulating endomembrane cation flux capacities. We suggest that changes in endomembrane potential affect JA pathway activity.
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Affiliation(s)
- Aurore Lenglet
- Department of Plant Molecular Biology, Biophore, University of Lausanne, Lausanne, CH-1015, Switzerland
| | - Dawid Jaślan
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Platz 2, Würzburg, D-97082, Germany
| | - Masatsugu Toyota
- Department of Botany, University of Wisconsin, Birge Hall, 430 Lincoln Drive, Madison, WI, 53706, USA
- Department of Biochemistry and Molecular Biology, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, 338-8570, Japan
- Japan Science and Technology Agency (JST), Precursory Research for Embryonic Science and Technology (PRESTO), Saitama, 332-0012, Japan
| | - Matthias Mueller
- Department of Plant Molecular Biology, Biophore, University of Lausanne, Lausanne, CH-1015, Switzerland
| | - Thomas Müller
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Platz 2, Würzburg, D-97082, Germany
| | - Gerald Schönknecht
- Department of Plant Biology, Ecology, and Evolution, Oklahoma State University, Stillwater, OK, 74078, USA
| | - Irene Marten
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Platz 2, Würzburg, D-97082, Germany
| | - Simon Gilroy
- Department of Botany, University of Wisconsin, Birge Hall, 430 Lincoln Drive, Madison, WI, 53706, USA
| | - Rainer Hedrich
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Platz 2, Würzburg, D-97082, Germany
| | - Edward E Farmer
- Department of Plant Molecular Biology, Biophore, University of Lausanne, Lausanne, CH-1015, Switzerland
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Electron current recordings in living cells. Biophys Chem 2017; 229:57-61. [DOI: 10.1016/j.bpc.2017.05.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 05/16/2017] [Accepted: 05/16/2017] [Indexed: 11/22/2022]
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Kintzer AF, Stroud RM. On the structure and mechanism of two-pore channels. FEBS J 2017; 285:233-243. [PMID: 28656706 DOI: 10.1111/febs.14154] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Revised: 05/24/2017] [Accepted: 06/23/2017] [Indexed: 12/22/2022]
Abstract
In eukaryotes, two-pore channels (TPC1-3) comprise a family of ion channels that regulate the conductance of Na+ and Ca2+ ions across cellular membranes. TPC1-3 form endolysosomal channels, but TPC3 can also function in the plasma membrane. TPC1/3 are voltage-gated channels, but TPC2 opens in response to binding endolysosome-specific lipid phosphatidylinositol-3,5-diphosphate (PI(3,5)P2 ). Filoviruses, such as Ebola, exploit TPC-mediated ion release as a means of escape from the endolysosome during infection. Antagonists that block TPC1/2 channel conductance abrogate filoviral infections. TPC1/2 form complexes with the mechanistic target of rapamycin complex 1 (mTORC1) at the endolysosomal surface that couple cellular metabolic state and cytosolic nutrient concentrations to the control of membrane potential and pH. We determined the X-ray structure of TPC1 from Arabidopsis thaliana (AtTPC1) to 2.87Å resolution-one of the two first reports of a TPC channel structure. Here, we summarize these findings and the implications that the structure may have for understanding endolysosomal control mechanisms and their role in human health.
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Affiliation(s)
- Alexander F Kintzer
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA
| | - Robert M Stroud
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA
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Naringenin Impairs Two-Pore Channel 2 Activity And Inhibits VEGF-Induced Angiogenesis. Sci Rep 2017; 7:5121. [PMID: 28698624 PMCID: PMC5505983 DOI: 10.1038/s41598-017-04974-1] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 05/23/2017] [Indexed: 12/11/2022] Open
Abstract
Our research introduces the natural flavonoid naringenin as a novel inhibitor of an emerging class of intracellular channels, Two-Pore Channel 2 (TPC2), as shown by electrophysiological evidence in a heterologous system, i.e. Arabidopsis vacuoles lacking endogenous TPCs. In view of the control exerted by TPC2 on intracellular calcium signaling, we demonstrated that naringenin dampens intracellular calcium responses of human endothelial cells stimulated with VEGF, histamine or NAADP-AM, but not with ATP or Angiopoietin-1 (negative controls). The ability of naringenin to impair TPC2-dependent biological activities was further explored in an established in vivo model, in which VEGF-containing matrigel plugs implanted in mice failed to be vascularized in the presence of naringenin. Overall, the present data suggest that naringenin inhibition of TPC2 activity and the observed inhibition of angiogenic response to VEGF are linked by impaired intracellular calcium signaling. TPC2 inhibition is emerging as a key therapeutic step in a range of important pathological conditions including the progression and metastatic potential of melanoma, Parkinson’s disease, and Ebola virus infection. The identification of naringenin as an inhibitor of TPC2-mediated signaling provides a novel and potentially relevant tool for the advancement of this field of research.
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Carpaneto A, Boccaccio A, Lagostena L, Di Zanni E, Scholz-Starke J. The signaling lipid phosphatidylinositol-3,5-bisphosphate targets plant CLC-a anion/H + exchange activity. EMBO Rep 2017; 18:1100-1107. [PMID: 28536248 DOI: 10.15252/embr.201643814] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 04/20/2017] [Accepted: 04/21/2017] [Indexed: 12/21/2022] Open
Abstract
Phosphatidylinositol-3,5-bisphosphate (PI(3,5)P2) is a low-abundance signaling lipid associated with endo-lysosomal and vacuolar membranes in eukaryotic cells. Recent studies on Arabidopsis indicated a critical role of PI(3,5)P2 in vacuolar acidification and morphology during ABA-induced stomatal closure, but the molecular targets in plant cells remained unknown. By using patch-clamp recordings on Arabidopsis vacuoles, we show here that PI(3,5)P2 does not affect the activity of vacuolar H+-pyrophosphatase or vacuolar H+-ATPase. Instead, PI(3,5)P2 at low nanomolar concentrations inhibited an inwardly rectifying conductance, which appeared upon vacuolar acidification elicited by prolonged H+ pumping activity. We provide evidence that this novel conductance is mediated by chloride channel a (CLC-a), a member of the anion/H+ exchanger family formerly implicated in stomatal movements in Arabidopsis H+-dependent currents were absent in clc-a knock-out vacuoles, and canonical CLC-a-dependent nitrate/H+ antiport was inhibited by low concentrations of PI(3,5)P2 Finally, using the pH indicator probe BCECF, we show that CLC-a inhibition contributes to vacuolar acidification. These data provide a mechanistic explanation for the essential role of PI(3,5)P2 and advance our knowledge about the regulation of vacuolar ion transport.
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Affiliation(s)
- Armando Carpaneto
- Institute of Biophysics, Consiglio Nazionale delle Ricerche, Genova, Italy
| | - Anna Boccaccio
- Institute of Biophysics, Consiglio Nazionale delle Ricerche, Genova, Italy
| | - Laura Lagostena
- Institute of Biophysics, Consiglio Nazionale delle Ricerche, Genova, Italy
| | - Eleonora Di Zanni
- Institute of Biophysics, Consiglio Nazionale delle Ricerche, Genova, Italy
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