STIM1 regulates Ca2+ entry via arachidonate-regulated Ca2+-selective (ARC) channels without store depletion or translocation to the plasma membrane.
Recent studies have indicated a critical role for STIM (stromal interacting molecule) proteins in the regulation of the store-operated mode of receptor-activated Ca2+ entry. Current models emphasize the role of STIM located in the endoplasmic reticulum membrane, where a Ca2+-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 Ca2+ stores. Dissociation of Ca2+ 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 Ca2+ channels. However, the possible effects of STIM on other modes of receptor-activated Ca2+ entry have not been examined. Here we show that STIM1 also regulates the arachidonic-acid-regulated Ca2+-selective (ARC) channels - receptor-activated Ca2+ entry channels whose activation is entirely independent of store depletion. Regulation of the ARC channels by STIM1 does not involve dissociation of Ca2+ 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 Ca2+ entry pathways than previously thought, and appears to have multiple modes of action.
Mignen
Olivier
O
Department of Pharmacology and Physiology, Box 711, University of Rochester Medical Center, 601 Elmwood Avenue, Rochester, NY 14642, USA.
Thompson
Jill L
JL
Shuttleworth
Trevor J
TJ
D016718:Arachidonic Acid / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000235:genetics / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D015870:Gene Expression / Q000502:physiology; D006801:Humans; D007668:Kidney / Q000166:cytology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D016296:Mutagenesis / Q000502:physiology; D009363:Neoplasm Proteins / Q000235:genetics / Q000502:physiology*; D018408:Patch-Clamp Techniques; D021381:Protein Transport / Q000502:physiology; D034741:RNA, Small Interfering; D000071737:Stromal Interaction Molecule 1
D015220:Calcium Channels; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D034741:RNA, Small Interfering; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1; D016718:Arachidonic Acid; D002118:Calcium