Current density responses in HEK cells stably overexpressing STIM1 with overexpression of concatenated tetrameric Orai1/Orai3 channels or empty vector control under store-depleting conditions. (A) CD development over time and application of 50 μM 2-APB as indicated (1-1-1-1, n = 6; 3-1-1-1, n = 12; 3-1-1-3, n = 10; 3-1-3-1, n = 7; 3-1-3-3, n = 10; control, n = 7). (B) Inward currents at t = 116 s extracted from (A). (C) Outward currents extracted at t = 178 s extracted from (A). (D) Corresponding IV relationships from (A). Statistical significance was determined by an unpaired t test with Welch’s correction and is presented as ns p > 0.05, * p < 0.05, ** p < 0.005, *** p < 0.001, **** p < 0.0001.