Orai1 forms a signal complex with BKCa channel in mesenteric artery smooth muscle cells

Orai1, a specific nonvoltage‐gated Ca2+ channel, has been found to be one of key molecules involved in store‐operated Ca2+ entry (SOCE). Orai1 may associate with other proteins to form a signaling complex, which is essential for regulating a variety of physiological functions. In this study, we studied the possible interaction between Orai1 and large conductance Ca2+‐activated potassium channel (BKCa). Using RNA interference technique, we demonstrated that the SOCE and its associated membrane hyperpolarization were markedly suppressed after knockdown of Orai1 with a specific Orai1 siRNA in rat mesenteric artery smooth muscle. Moreover, isometric tension measurements showed that agonist‐induced vasocontraction was increased after Orai1 was knocked down or the tissue was incubated with BKCa blocker iberiotoxin. Coimmunoprecipitation data revealed that BKCa and Orai1 could reciprocally pull down each other. In situ proximity ligation assay further demonstrated that Orai1 and BKCa are in close proximity. Taken together, these results indicate that Orai1 physically associates with BKCa to form a signaling complex in the rat mesenteric artery smooth muscle. Ca2+ influx via Orai1 stimulates BKCa, leading to membrane hyperpolarization. This hyperpolarizing effect of Orai1‐BKCa coupling could contribute to reduce agonist‐induced membrane depolarization, therefore preventing excessive contraction of the rat mesenteric artery smooth muscle in response to contractile agonists.