Orai1 and Ca2+-independent phospholipase A2 are required for store-operated Icat-SOC current, Ca2+ entry, and proliferation of primary vascular smooth muscle cells

Yang B, Gwozdz T, Dutko-Gwozdz J, Bolotina VM. Orai1 and Ca2+-independent phospholipase A(2) are required for store-operated Icat-SOC current, Ca2+ entry, and proliferation of primary vascular smooth muscle cells. Am J Physiol Cell Physiol 302: C748-C756, 2012. First published November 16, 2011; doi:10.1152/ajpcell.00312.2011.-Store-operated Ca2+ entry (SOCE) is important for multiple functions of vascular smooth muscle cells (SMC), which, depending of their phenotype, can resemble excitable and nonexcitable cells. Similar to nonexcitable cells, Orai1 was found to mediate Ca2+-selective (CRAC-like) current and SOCE in dedifferentiated cultured SMC and smooth muscle-derived cell lines. However, the role of Orai1 in cation-selective store-operated channels (cat-SOC), which are responsible for SOCE in primary SMC, remains unclear. Here we focus on primary SMC, and assess the role of Orai1 and Ca2+-independent phospholipase A2 (iPLA(2)beta, or PLA2G6) in activation of cat-SOC current (Icat-SOC), SOCE, and SMC proliferation. Using molecular, electrophysiological, imaging, and functional approaches, we demonstrate that molecular knockdown of either Orai1 or iPLA(2)beta leads to similar inhibition of the whole cell cat-SOC current and SOCE in primary aortic SMC and results in significant reduction in DNA synthesis and impairment of SMC proliferation. This is the first demonstration that Orai1 and iPLA(2)beta are equally important for cat-SOC, SOCE, and proliferation of primary aortic SMC.