STIM1 regulates Ca2+ entry via arachidonate-regulated Ca2+-selective (ARC) channels without store-depletion or translocation to the plasma membrane

Authors:
Mignen O, Thompson JL, Shuttleworth TJ
In:
Source: J Physiol
Publication Date: (2007)
Issue: 579(Pt 3): 703-15
Research Area:
Cancer Research/Cell Biology
Cells used in publication:
293
Species: human
Tissue Origin: kidney
Platform:
Nucleofectorâ„¢ I/II/2b
Abstract
Recent studies have indicated a critical role for STIM (stromal interacting molecule) proteins in the regulation of the store-operated mode of receptor-activated Ca(2+) entry. Current models emphasize the role of STIM located in the endoplasmic reticulum membrane, where a Ca(2+)-binding EF-hand domain within the N-terminal of the protein lies within the lumen and is thought to represent the sensor for the depletion of intracellular Ca(2+) stores. Dissociation of Ca(2+) from this domain induces the aggregation of STIM to regions of the ER immediately adjacent to the plasma membrane where it acts to regulate the activity of store-operated Ca(2+) channels. However, the possible effects of STIM on other modes of receptor-activated Ca(2+) entry have not been examined. Here we show that STIM1 also regulates the arachidonic-acid-regulated Ca(2+)-selective (ARC) channels - receptor-activated Ca(2+) entry channels whose activation is entirely independent of store depletion. Regulation of the ARC channels by STIM1 does not involve dissociation of Ca(2+) from the EF-hand, or any translocation of STIM1. Instead, a critical role of STIM1 resident in the plasma membrane is indicated. Thus, exposure of intact cells to an antibody targeting the extracellular N-terminal domain of STIM1 inhibits ARC channel activity without significantly affecting the store-operated channels. A similar specific inhibition of the ARC channels is seen in cells expressing a STIM1 construct in which the N-linked glycosylation sites essential for the constitutive cell surface expression of STIM1, were mutated. We conclude that, in contrast to store-operated channels, regulation of ARC channels by STIM1 depends exclusively on the pool of STIM1 constitutively residing in the plasma membrane. These data demonstrate that STIM1 is a more universal regulator of Ca(2+) entry pathways than previously thought, and appears to have multiple modes of action.