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Saito R, Mu Q, Yuan Y, Rubio-Alarcón M, Eznarriaga M, Zhao P, Gunaratne G, Kumar S, Keller M, Bracher F, Grimm C, Brailoiu E, Marchant JS, Rahman T, Patel S. Convergent activation of Ca 2+ permeability in two-pore channel 2 through distinct molecular routes. Sci Signal 2023; 16:eadg0661. [PMID: 37607219 PMCID: PMC10639088 DOI: 10.1126/scisignal.adg0661] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Accepted: 07/27/2023] [Indexed: 08/24/2023]
Abstract
TPC2 is a pathophysiologically relevant lysosomal ion channel that is activated directly by the phosphoinositide PI(3,5)P2 and indirectly by the calcium ion (Ca2+)-mobilizing molecule NAADP through accessory proteins that associate with the channel. TPC2 toggles between PI(3,5)P2-induced, sodium ion (Na+)-selective and NAADP-induced, Ca2+-permeable states in response to these cues. To address the molecular basis of polymodal gating and ion-selectivity switching, we investigated the mechanism by which NAADP and its synthetic functional agonist, TPC2-A1-N, induced Ca2+ release through TPC2 in human cells. Whereas NAADP required the NAADP-binding proteins JPT2 and LSM12 to evoke endogenous calcium ion signals, TPC2-A1-N did not. Residues in TPC2 that bind to PI(3,5)P2 were required for channel activation by NAADP but not for activation by TPC2-A1-N. The cryptic voltage-sensing region of TPC2 was required for the actions of TPC2-A1-N and PI(3,5)P2 but not for those of NAADP. These data mechanistically distinguish natural and synthetic agonist action at TPC2 despite convergent effects on Ca2+ permeability and delineate a route for pharmacologically correcting impaired NAADP-evoked Ca2+ signals.
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Affiliation(s)
- Ryo Saito
- Department of Cell and Developmental Biology, University
College London, Gower Street, London WC1E 6BT, UK
- Department of Dermatology, Graduate School of Biomedical
and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Qianru Mu
- Department of Cell and Developmental Biology, University
College London, Gower Street, London WC1E 6BT, UK
| | - Yu Yuan
- Department of Cell and Developmental Biology, University
College London, Gower Street, London WC1E 6BT, UK
| | | | - Maria Eznarriaga
- Department of Pharmacology, University of Cambridge,
Cambridge, UK
| | - Pingwei Zhao
- Center for Substance Abuse Research, Lewis Katz School of
Medicine at Temple University, Philadelphia, PA 19140, USA
| | - Gihan Gunaratne
- Department of Cell Biology, Neurobiology and Anatomy,
Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226,
USA
| | - Sushil Kumar
- Department of Cell Biology, Neurobiology and Anatomy,
Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226,
USA
| | - Marco Keller
- Department of Pharmacy—Center for Drug Research,
Ludwig-Maximilian University, Munich, Germany
| | - Franz Bracher
- Department of Pharmacy—Center for Drug Research,
Ludwig-Maximilian University, Munich, Germany
| | - Christian Grimm
- Walther Straub Institute of Pharmacology and Toxicology,
Faculty of Medicine, Ludwig-Maximilians University, Munich, Germany
| | - Eugen Brailoiu
- Center for Substance Abuse Research, Lewis Katz School of
Medicine at Temple University, Philadelphia, PA 19140, USA
| | - Jonathan S. Marchant
- Department of Cell Biology, Neurobiology and Anatomy,
Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226,
USA
| | - Taufiq Rahman
- Department of Pharmacology, University of Cambridge,
Cambridge, UK
| | - Sandip Patel
- Department of Cell and Developmental Biology, University
College London, Gower Street, London WC1E 6BT, UK
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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] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 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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