Dependence of STIM1/Orai1-mediated calcium entry on plasma membrane phosphoinositides.
Recent studies identified two main components of store-operated calcium entry (SOCE): the endoplasmic reticulum-localized Ca2+ sensor protein, STIM1, and the plasma membrane (PM)-localized Ca2+ channel, Orai1/CRACM1. In the present study, we investigated the phosphoinositide dependence of Orai1 channel activation in the PM and of STIM1 movements from the tubular to PM-adjacent endoplasmic reticulum regions during Ca2+ store depletion. Phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) levels were changed either with agonist stimulation or by chemically induced recruitment of a phosphoinositide 5-phosphatase domain to the PM, whereas PtdIns4P levels were decreased by inhibition or down-regulation of phosphatidylinositol 4-kinases (PI4Ks). Agonist-induced phospholipase C activation and PI4K inhibition, but not isolated PtdIns(4,5)P(2) depletion, substantially reduced endogenous or STIM1/Orai1-mediated SOCE without preventing STIM1 movements toward the PM upon Ca2+ store depletion. Patch clamp analysis of cells overexpressing STIM1 and Orai1 proteins confirmed that phospholipase C activation or PI4K inhibition greatly reduced I(CRAC) currents. These results suggest an inositide requirement of Orai1 activation but not STIM1 movements and indicate that PtdIns4P rather than PtdIns(4,5)P2 is a likely determinant of Orai1 channel activity.
Korzeniowski
Marek K
MK
Sections on molecular signal transduction, National Institutes of Health, Bethesda, Maryland 20892, USA.
Popovic
Marko A
MA
Szentpetery
Zsofia
Z
Varnai
Peter
P
Stojilkovic
Stanko S
SS
Balla
Tamas
T
D019870:1-Phosphatidylinositol 4-Kinase / Q000037:antagonists & inhibitors; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D019556:COS Cells; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002522:Chlorocebus aethiops; D015536:Down-Regulation / Q000187:drug effects; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D055785:Gene Knockdown Techniques; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D010738:Type C Phospholipases / Q000378:metabolism
D015220:Calcium Channels; D008565:Membrane Proteins; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; D047428:Protein Kinase Inhibitors; C037178:phosphatidylinositol 4-phosphate; D000804:Angiotensin II; D019870:1-Phosphatidylinositol 4-Kinase; D010738:Type C Phospholipases; D002118:Calcium