title: Stimulated association of STIM1 and Orai1 is regulated by the balance of PtdIns(4,5)P₂ between distinct membrane pools.
abstract: We have previously shown that PIP5KIβ and PIP5KIγ generate functionally distinct pools of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P(2)] important for antigen-stimulated Ca(2+) entry in mast cells. In the present study, we find that association of the endoplasmic reticulum (ER) Ca(2+) sensor, STIM1, and the store-operated Ca(2+) channel, Orai1, stimulated by thapsigargin-mediated ER store depletion, is enhanced by overexpression of PIP5KIβ and inhibited by overexpression of PIP5KIγ. These different PIP5KI isoforms cause differential enhancement of PtdIns(4,5)P(2) in detergent-resistant membrane (DRM) fractions, which comprise ordered lipid regions, and detergent-solubilized membrane (DSM) fractions, which comprise disordered lipid regions. Consistent with these results, the inositol 5-phosphatase L10-Inp54p, which is targeted to ordered lipids, decreases PtdIns(4,5)P(2) in the DRM fraction and inhibits thapsigargin-stimulated STIM1-Orai1 association and store-operated Ca(2+) entry, whereas the inositol 5-phosphatase S15-Inp54p, which is targeted to disordered lipids, decreases PtdIns(4,5)P(2) in the DSM fraction and enhances STIM1-Orai1 association. Removal of either the STIM1 C-terminal polylysine sequence (amino acids 677-685) or an N-terminal polyarginine sequence in Orai1 (amino acids 28-33) eliminates this differential sensitivity of STIM1-Orai1 association to PtdIns(4,5)P(2) in the distinctive membrane domains. Our results are consistent with a model of PtdIns(4,5)P(2) balance, in which store-depletion-stimulated STIM1-Orai1 association is positively regulated by the ordered lipid pool of PtdIns(4,5)P(2) and negatively regulated by PtdIns(4,5)P(2) in disordered lipid domains.
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Nathaniel
authors.initials: N
authors.lastname: Calloway
authors.forename: Tristan
authors.initials: T
authors.lastname: Owens
authors.forename: Kathryn
authors.initials: K
authors.lastname: Corwith
authors.forename: William
authors.initials: W
authors.lastname: Rodgers
authors.forename: David
authors.initials: D
authors.lastname: Holowka
authors.forename: Barbara
authors.initials: B
authors.lastname: Baird
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D045744:Cell Line, Tumor; D008562:Membrane Glycoproteins / Q000378:metabolism*; D018613:Microscopy, Confocal; D000071740:ORAI1 Protein; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D051381:Rats; D000071737:Stromal Interaction Molecule 1
chemical_list: D015220:Calcium Channels; D008562:Membrane Glycoproteins; D000071740:ORAI1 Protein; C532493:Orai1 protein, rat; D019269:Phosphatidylinositol 4,5-Diphosphate; D020033:Protein Isoforms; C518857:Stim1 protein, rat; D000071737:Stromal Interaction Molecule 1; D017853:Phosphotransferases (Alcohol Group Acceptor); C501303:PIP5KI protein, rat; D002118:Calcium