# Ionic Mechanisms of Two-Pore Channel Regulation of Vesicle Trafficking

## TL;DR

This paper explains how two-pore channels regulate vesicle trafficking by releasing calcium and sodium ions from endosomes and lysosomes.

## Contribution

The study highlights the distinct roles of Ca2+ and Na+ efflux in vesicle trafficking and the dual regulation by NAADP and PI(3,5)P2.

## Key findings

- TPC1 and TPC2 release Ca2+ and Na+ from endosomes and lysosomes upon activation by NAADP and PI(3,5)P2.
- Ca2+ and Na+ effluxes have distinct roles in intracellular vesicle trafficking.
- Both Ca2+ and Na+ effects are important for understanding TPC-regulated cellular functions.

## Abstract

What are the main findings?
Two-pore channels (TPC1 and TPC2) are intracellular channels activated by NAADP and PI(3,5)P2 to release Ca2+ and Na+ from endosomes and lysosomes.TPC-mediated effluxes of Ca2+ and Na+ play distinct roles in intracellular vesicle trafficking.

Two-pore channels (TPC1 and TPC2) are intracellular channels activated by NAADP and PI(3,5)P2 to release Ca2+ and Na+ from endosomes and lysosomes.

TPC-mediated effluxes of Ca2+ and Na+ play distinct roles in intracellular vesicle trafficking.

What are the implications of the main findings?
The dual regulation by NAADP and PI(3,5)P2 explains the diverse functions of TPCs in physiology and disease.Both Ca2+- and Na+-mediated effects need to be considered when evaluating the mechanism of TPC-regulation of cellular function.

The dual regulation by NAADP and PI(3,5)P2 explains the diverse functions of TPCs in physiology and disease.

Both Ca2+- and Na+-mediated effects need to be considered when evaluating the mechanism of TPC-regulation of cellular function.

The endolysosomal system plays a pivotal role in cellular function. Before reaching lysosomes for degradation, the endocytosed cargoes are sorted at various stages of endosomal trafficking for recycling and/or rerouting. The proper execution of these processes depends on tightly regulated ion fluxes across endolysosomal membranes. Recent studies have demonstrated the importance of two-pore channels (TPCs), including TPC1 and TPC2, in endolysosomal trafficking. These channels are expressed in the membranes of distinct populations of endosomes and lysosomes, where they respond to nicotinic acid adenine dinucleotide phosphate (NAADP) and phosphatidylinositol 3,5-bisphosphate [PI(3,5)P2] to conduct Ca2+ and Na+ release from these acidic organelles. Here, we discuss the potential implications of Ca2+ and Na+ fluxes mediated by TPCs across endolysosomal membranes in the physiological and pathophysiological functions of these organellar channels.