Effect of overexpression of HNF-4α on STIM1 expression in HEK-293 cells. A: representative experiment showing STIM1 expression (middle) in HEK-293 cells without transfection (Untran) or transfected with vector pcDNA3 (pcDNA3), HNF4α expression plasmid (HNF4α), STIM1 expression plasmid plus pcDNA3 vector (STIM1 + pcDNA3), and STIM1 expression plasmid plus HNF4α expression plasmid (STIM1 + HNF4α). HNF4α expression in the five groups of cells is shown in the top. Tubulin (TB; bottom) was used as a loading control. Ex-HNF4α, exogenous HNF4α; En-HNF4α, endogenous HNF4α; Ex-STIM1, exogenous STIM1; En-STIM1, endogenous STIM1. B: summary data averaged from four independent experiments shown in A (n = 4). Ex-STIM1 protein expression levels were normalized to TB. *P < 0.05 compared with STIM1 + pcDNA3.