FIGURE 1.

STIM1 phosphorylation inhibits SOCE in endothelial cells. A, thrombin-induced STIM1 phosphorylation was measured. HLMVECs exposed to thrombin (50 nm) for different time periods were lysed; lysates were immunoprecipitated (IP) with STIM1 mAb, and the immunoprecipitate was immunoblotted (IB) with anti-phospho-Ser pAb (top row). Total cell lysates were immunoblotted with anti-STIM1 mAb (bottom row). Phosphoprotein bands were quantified by densitometry and expressed as relative to control (bottom panel). Results shown are mean ± S.E. of four experiments. B, HLMVECs were preincubated either with thrombin (50 nm) (top panel) or PAR-1 peptide (40 μm) (bottom panel) for different time periods. After the specified time points, cells were used to measure TG (1 μm)-induced store Ca²⁺ release and Ca²⁺ entry (see details under “Experimental Procedures”). The experiment was repeated three times with similar results.