TRPM4-mediated control of FcεRI-evoked Ca(2+) elevation comprises enhanced plasmalemmal trafficking of TRPM4 channels in connective tissue type mast cells.

Torben Rixecker,Alexander Pfeifer,Stefanie Mannebach,Peter Lipp,Rebekka Medert,Marc Freichel,Volodymyr Tsvilovskyy,Ilka Mathar

doi:10.1038/srep32981

Abstract

TRPM4 proteins form Ca2+-activated non selective cation (CAN) channels that affect transmembrane Ca2+-influx by determining the membrane potential. Tight control of the intracellular Ca2+ concentration is essential for mast cell responses. In this study, we analyzed the expression of TRPM4 in peritoneal mast cells (PCMC) as a model for connective tissue type mast cells with respect to FcεRI-evoked calcium changes and the subcellular localization of fluorescently labeled TRPM4 using two viral transduction systems before and following antigen stimulation. Our results show that TRPM4 is expressed in PCMCs, is an essential constituent of the endogenous CAN channels in PCMCs and regulates antigen-evoked increases in intracellular calcium that are significantly enhanced in TRPM4-deficient PCMCs. Compared to PCMCs analyzed before antigen stimulation, the cells depict a substantially increased localization of TRPM4 proteins towards the plasma membrane after FcεRI stimulation. Thus, TRPM4 functions as a limiting factor for antigen evoked calcium rise in connective tissue type mast cells and concurrent translocation of TRPM4 into the plasma membrane is part of this mechanism.

Highlights

Initially described by Enerbäck et al in 197014 and were later developed further[12]
Similar to bone marrow derived mast cells (BMMCs), where TRPM5 expression was not detected[8], we found that upon deletion of TRPM4 FcεRI-evoked calcium transients are significantly enhanced in PCMCs (Fig. 2)
Fluorimetric measurements showed that FcεRI-evoked Ca2+ transients were significantly increased in TRPM4-deficient peritoneal mast cells compared to wild type controls

Summary

Introduction

Initially described by Enerbäck et al in 197014 and were later developed further[12]. Work in pancreatic beta (INS-1) and smooth muscle (A7r5) cell lines suggested a translocation of TRPM4 proteins from intracellular organelles towards the plasma membrane contributing to the incremental increase of TRPM4 current density[17,18]. In these experiments, TRPM4 channels were stimulated by elevation of cytosolic calcium or by protein kinase C (PKC) activators, but evidence for receptor-operated translocation of TRPM4 proteins, in primary mast cells, is still lacking. Our results indicate that TRPM4 is functionally relevant as a limiting factor for antigen-evoked calcium rise and that concurrent translocation of TRPM4 into the plasma membrane is part of this mechanism that limits mast cell activation in tissue mast cells

Objectives

Methods

Results

Conclusion