Dependence of STIM1/Orai1-mediated Calcium Entry on Plasma Membrane Phosphoinositides

作者：Korzeniowski Marek K; Popovic Marko A; Szentpetery Zsofia; Varnai Peter; Stojilkovic Stanko S; Balla Tamas^*

来源：JOURNAL OF BIOLOGICAL CHEMISTRY, 2009, 284(31): 21027-21035.

DOI：10.1074/jbc.M109.012252

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)P-2) 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)P-2 is a likely determinant of Orai1 channel activity.

• 出版日期2009-7-31