Agonist-mediated switching of ion selectivity in TPC2 differentially promotes lysosomal function

  • Elife. 2020 Mar 16;9:e54712. doi: 10.7554/eLife.54712.
Susanne Gerndt   #  1  2 ,  Cheng-Chang Chen   #  1 ,  Yu-Kai Chao   #  2 ,  Yu Yuan   #  3 ,  Sandra Burgstaller  4 ,  Anna Scotto Rosato  2 ,  Einar Krogsaeter  2 ,  Nicole Urban  5 ,  Katharina Jacob  2 ,  Ong Nam Phuong Nguyen  1 ,  Meghan T Miller  1  6 ,  Marco Keller  1 ,  Angelika M Vollmar  1 ,  Thomas Gudermann  2 ,  Susanna Zierler  2 ,  Johann Schredelseker  1  2 ,  Michael Schaefer  1  5 ,  Martin Biel  1 ,  Roland Malli  4 ,  Christian Wahl-Schott  7 ,  Franz Bracher  1 ,  Sandip Patel  3 ,  Christian Grimm  2
Affiliations
  • 1. Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität, Munich, Germany.
  • 2. Walther Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, Ludwig-Maximilians-Universität, Munich, Germany.
  • 3. Department of Cell and Developmental Biology, University College London, London, United Kingdom.
  • 4. Molecular Biology and Biochemistry, Gottfried Schatz Research Center, Medical University of Graz, Graz, Austria.
  • 5. Rudolf-Boehm-Institute for Pharmacology and Toxicology, Universität Leipzig, Leipzig, Germany.
  • 6. Pharma Research and Early Development (pRED), Roche Innovation Center Basel, F. Hoffmann-La Roche, Basel, Switzerland.
  • 7. Institute for Neurophysiology, Hannover Medical School, Hannover, Germany.
  • # Contributed equally.
PMID: 32167471 DOI: 10.7554/eLife.54712
Abstract

Ion selectivity is a defining feature of a given ion channel and is considered immutable. Here we show that ion selectivity of the lysosomal ion channel TPC2, which is hotly debated (Calcraft et al., 2009; Guo et al., 2017; Jha et al., 2014; Ruas et al., 2015; Wang et al., 2012), depends on the activating ligand. A high-throughput screen identified two structurally distinct TPC2 agonists. One of these evoked robust CA2+-signals and non-selective cation currents, the other weaker CA2+-signals and Na+-selective currents. These properties were mirrored by the CA2+-mobilizing messenger, NAADP and the phosphoinositide, PI(3,5)P2, respectively. Agonist action was differentially inhibited by mutation of a single TPC2 residue and coupled to opposing changes in lysosomal pH and exocytosis. Our findings resolve conflicting reports on the permeability and gating properties of TPC2 and they establish a new paradigm whereby a single ion channel mediates distinct, functionally-relevant ionic signatures on demand.

Keywords
NAADP; PI(3,5)P2; TPC; TPC2; biochemistry; chemical biology; human; lysosome; mouse; two-pore channel 2.
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