Stromal interaction molecule 1 (STIM1) regulates store-operated Ca entry (SOCE) and other ion channels either as an endoplasmic reticulum Ca-sensing protein or when present in the plasma membrane. However, the role of STIM1 in insulin-secreting β-cells is unresolved. We report that lowering expression of , the gene that encodes STIM1, in insulin-secreting MIN6 β-cells with RNA interference inhibits SOCE and ATP-sensitive K () channel activation. The effects of knockdown were reversed by transduction of MIN6 cells with an adenovirus gene shuttle vector that expressed human Immunoprecipitation studies revealed that STIM1 binds to nucleotide binding fold-1 (NBF1) of the sulfonylurea receptor 1 (SUR1) subunit of the channel. Binding of STIM1 to SUR1 was enhanced by poly-lysine. Our data indicate that SOCE and channel activity are regulated by STIM1. This suggests that STIM1 is a multifunctional signaling effector that participates in the control of membrane excitability and Ca signaling events in β-cells.
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