The molecular insights into the gating mechanism and function of SOC channel

Abstract

Store-operated Ca2+ entry (SOCE), the important cellular process in a wide range of cell types and species, is mediated by stromal interaction molecule (STIM), which senses the depletion of endoplasmic reticulum Ca2+ stores and binds and activates Orai channels in the plasma membrane. This inside-out mechanism of Ca2+ signaling raises some interesting questions about the SOCE: how did this sensitive Ca2+ signaling regulated by these two proteins existing in different cellular compartments? In this paper, I clarified the molecular insights into the gating mechanism and function of SOC channel by investigated the gating mechanism of Caenorhabditis elegans Orai channels and investigated the function of STIM2beta, an eight-residue-inserted splice variant of STIM2, in myogenesis. My analysis revealed a mechanism of Orai gating by STIM binding to the intracellular 2-3 loop of Orai in C. elegans that is radically different from Orai gating by STIM binding to the N and C termini of Orai in mammals. Besides, I found that the conserved hydrophobic amino acids in the 2-3 loop of Orai1 are essential for the oligomerization and gating of channels and are regulated via an intramolecular interaction mechanism mediated by the N and C termini of Orai1. Also, I found that the STIM2beta splicing was increases during in vitro differentiation of skeletal muscle. This study I investigated the function of STIM2beta in myogenesis with RNA interference-mediated knockdown and CRISPR-Cas-mediated knockout approaches. Deletion of STIM2beta delayed myogenic differentiation through the MEF2C and NFAT4 pathway in C2C12 cells. Further, loss of STIM2beta increased cell proliferation by altering Ca2+ homeostasis and inhibited cell cycle arrest mediated by the cyclin D1-CDK4 degradation pathway. Taken together, these data identified a previously unknown the molecular insights into the gating mechanism and function of SOC channel.