STIM1 has a plasma membrane role in the activation of store-operated Ca(2+) channels.
Receptor-induced Ca(2+) signals are key to the function of all cells and involve release of Ca(2+) from endoplasmic reticulum (ER) stores, triggering Ca(2+) entry through plasma membrane (PM) "store-operated channels" (SOCs). The identity of SOCs and their coupling to store depletion remain molecular and mechanistic mysteries. The single transmembrane-spanning Ca(2+)-binding protein, STIM1, is necessary in this coupling process and is proposed to function as an ER Ca(2+) sensor to provide the trigger for SOC activation. Here we reveal that, in addition to being an ER Ca(2+) sensor, STIM1 functions within the PM to control operation of the Ca(2+) entry channel itself. Increased expression levels of STIM1 correlate with a gain in function of Ca(2+) release-activated Ca(2+) (CRAC) channel activity. Point mutation of the N-terminal EF hand transforms the CRAC channel current (I(CRAC)) into a constitutively active, Ca(2+) store-independent mode. Mutants in the EF hand and cytoplasmic C terminus of STIM1 alter operational parameters of CRAC channels, including pharmacological profile and inactivation properties. Last, Ab externally applied to the STIM1 N-terminal EF hand blocks both I(CRAC) in hematopoietic cells and SOC-mediated Ca(2+) entry in HEK293 cells, revealing that STIM1 has an important functional presence within the PM. The results reveal that, in addition to being an ER Ca(2+) sensor, STIM1 functions within the PM to exert control over the operation of SOCs. As a cell surface signaling protein, STIM1 represents a key pharmacological target to control fundamental Ca(2+)-regulated processes including secretion, contraction, metabolism, cell division, and apoptosis.
Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
Maria A
MA
Spassova
Jonathan
J
Soboloff
Li-Ping
LP
He
Wen
W
Xu
Marie A
MA
Dziadek
Donald L
DL
Gill
D000818:Animals; D015220:Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D009363:Neoplasm Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000071737:Stromal Interaction Molecule 1; D050052:TRPC Cation Channels / Q000378:metabolism*
D015220:Calcium Channels; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1; D050052:TRPC Cation Channels