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

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.

Could the Inhibition of Endo-Lysosomal Two-Pore Channels (TPCs) by the Natural Flavonoid Naringenin Represent an Option to Fight SARS-CoV-2 Infection?

“…Therefore, inhibition of TPCs should both impair the fusogenic potential of the endo-lysosomal system and alter the normal trafficking, which, in turn, could be a limit for viral replication (Alsaadi and Jones, 2019). Very recently, unique features of TPC2 in the response to different agonists have been published (Gerndt et al, 2020) expanding the characterization of this channel, hence the range of potential approaches to pharmacologically control the intracellular pathway of the virus.…”

TPC1 deficiency or blockade augments systemic anaphylaxis and mast cell activity

“…The effect of simultaneous NAADP application together with GTPγS was less severe but supports the same notion. The very recent identification of two structurally distinct TPC2 agonists, mirroring NAADP and PI(3,5)P 2 activation characteristics, suggests diverse ion channel selectivity depending on the mode of activation (50). However, whether TPC1 also switches its ion selectivity remains to be established, and TPC2 does not seem to be involved in degranulation of preformed mast cell granules.…”

ER-to-Golgi Transport in HeLa Cells Displays High Resilience to Ca2+ and Energy Stresses

“…HeLa cells stably expressing pH-Lemon-GPI [ 57 , 58 ] were used to investigate vesicle movement. Pretreatment (+ glucose, − glucose, + 2-DG, EGTA/2Ca + ATP + BHQ) was conducted equivalent to the transport experiment (see Section 2.4 ).…”