Understanding polymodal gating of a lysosomal ion channel
Lead Research Organisation:
University College London
Department Name: Cell and Developmental Biology
Abstract
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Technical Summary
Selective ion channels open to allow the flow of a single type of ion whereas non-selective ion channels allow multiple ions through. Ion selectivity is a defining feature of a given ion channel and is generally considered a fixed entity. But the lysosomal ion channel TPC2 has been shown recently to defy dogma displaying completely different ion selectivity profiles when activated by its endogenous activators, NAADP, a calcium mobilising messenger and PI(3,5)P2, an endo-lysosomal lipid. This highly unusual behaviour needs to be explained mechanistically as it contradicts the text-book view.
Armed with new NAADP and PI(3,5)P2 mimetics, our pilot high-resolution single channel recordings show that ion selection and gating profiles are linked in an agonist-specific manner. PI(3,5)P2 binds TPC2 directly but NAADP is thought to bind to associated NAADP-binding proteins that have only very recently been identified. Despite such segregated action, further pilot studies identify a key region of TPC2 that appears to be responsible for activation by both endogenous cues. This leads us to hypothesize gating and ion selection by TPC2 are coupled through distinct but converging agonist-specific mechanisms.
Our aims are to i) establish the behavior of single agonist-activated TPC2 channels and define ii) the dynamics of agonist activation and iii) the coupling of TPC2 channels to NAADP receptors. We will do so through an interdisciplinary approach comprising electrophysiology, molecular dynamics simulations and molecular cell biology brought about by the collaboration.
Successful outcome of this project will provide fundamental insight into how an ion channel morphs on demand.
Armed with new NAADP and PI(3,5)P2 mimetics, our pilot high-resolution single channel recordings show that ion selection and gating profiles are linked in an agonist-specific manner. PI(3,5)P2 binds TPC2 directly but NAADP is thought to bind to associated NAADP-binding proteins that have only very recently been identified. Despite such segregated action, further pilot studies identify a key region of TPC2 that appears to be responsible for activation by both endogenous cues. This leads us to hypothesize gating and ion selection by TPC2 are coupled through distinct but converging agonist-specific mechanisms.
Our aims are to i) establish the behavior of single agonist-activated TPC2 channels and define ii) the dynamics of agonist activation and iii) the coupling of TPC2 channels to NAADP receptors. We will do so through an interdisciplinary approach comprising electrophysiology, molecular dynamics simulations and molecular cell biology brought about by the collaboration.
Successful outcome of this project will provide fundamental insight into how an ion channel morphs on demand.
Organisations
People |
ORCID iD |
Sandip Patel (Principal Investigator) |
Publications
Saito R
(2023)
Convergent activation of Ca2+ permeability in two-pore channel 2 through distinct molecular routes.
in Science signaling
Gunaratne GS
(2023)
Convergent activation of two-pore channels mediated by the NAADP-binding proteins JPT2 and LSM12.
in Science signaling
Yuan Y
(2024)
Coordinating activation of endo-lysosomal two-pore channels and TRP mucolipins.
in The Journal of physiology
Patel S
(2023)
Endo-Lysosomal Two-Pore Channels and Their Protein Partners.
in Handbook of experimental pharmacology
Jaslan D
(2023)
New insights into gating mechanisms in TPCs: Relevance for drug discovery.
in Cell calcium
Jaslan D
(2023)
PI(3,5)P2 and NAADP: Team players or lone warriors? - New insights into TPC activation modes
in Cell Calcium
Gunaratne G
(2023)
Progesterone receptor membrane component 1 facilitates Ca2+ signal amplification between endosomes and the endoplasmic reticulum
in Journal of Biological Chemistry
Clement D
(2023)
The Lysosomal Calcium Channel TRPML1 Maintains Mitochondrial Fitness in NK Cells through Interorganelle Cross-Talk.
in Journal of immunology (Baltimore, Md. : 1950)
Alonso MT
(2023)
Use of aequorin-based indicators for monitoring Ca2+ in acidic organelles.
in Biochimica et biophysica acta. Molecular cell research