P2X4 Receptors Mediate Ca2+ Release from Lysosomes in Response to Stimulation of P2X7 and H1 Histamine Receptors.

Sin-Lih Tan,Peace Atakpa-Adaji,Colin W Taylor,Ewan St John Smith,Ruth D Murrell-Lagnado,Muruj Barri

doi:10.3390/ijms221910492

Abstract

The P2X4 purinergic receptor is targeted to endolysosomes, where it mediates an inward current dependent on luminal ATP and pH. Activation of P2X4 receptors was previously shown to trigger lysosome fusion, but the regulation of P2X4 receptors and their role in lysosomal Ca2+ signaling are poorly understood. We show that lysosomal P2X4 receptors are activated downstream of plasma membrane P2X7 and H1 histamine receptor stimulation. When P2X4 receptors are expressed, the increase in near-lysosome cytosolic [Ca2+] is exaggerated, as detected with a low-affinity targeted Ca2+ sensor. P2X4-dependent changes in lysosome properties were triggered downstream of P2X7 receptor activation, including an enlargement of lysosomes indicative of homotypic fusion and a redistribution of lysosomes towards the periphery of the cell. Lysosomal P2X4 receptors, therefore, have a role in regulating lysosomal Ca2+ release and the regulation of lysosomal membrane trafficking.

Highlights

Upregulation of P2X4 receptors in macrophages and microglia enhances the release of prostaglandins and brain-derived neurotrophic factor, which contribute to the development of inflammatory and neuropathic pain [8,12,13,14,15,16]
To identify physiological regulators of endolysosomal P2X4 receptors, we focused on two different signaling pathways: the P2X7 receptor and the H1 histamine receptor, the latter being an example of a G-protein-coupled receptor that stimulates Ca2+ release from the endoplasmic reticulum (ER) through IP3 receptors
Using a low-affinity, targeted Ca2+ sensor to reveal peaks of [Ca2+ ]c in the immediate vicinity of the lysosomes, we show that Ca2+ signals evoked by activation of

Summary

Introduction

The P2X4 purinergic receptor is targeted to endolysosomes, where it mediates an inward current dependent on luminal ATP and pH. We show that lysosomal P2X4 receptors are activated downstream of plasma membrane P2X7 and H1 histamine receptor stimulation. P2X4-dependent changes in lysosome properties were triggered downstream of P2X7 receptor activation, including an enlargement of lysosomes indicative of homotypic fusion and a redistribution of lysosomes towards the periphery of the cell. The P2X4 receptor is a member of the ATP-gated cation channel family. It is widely distributed in peripheral tissues and the central nervous system [1,2,3,4]. Given the high luminal concentrations of ATP, P2X4 receptors might be expected to regulate ion fluxes across lysosome membranes [20,22]

Methods

Results

Conclusion