Figure 1.

2-APB-mediated current density (CD) responses in HEK cells stably overexpressing STIM1 with 50 μM IP₃ and 0 nM Ca²⁺ in the patch pipette. (A) CD development over time with Orai1 overexpression (n = 8) and application of 50 μM 2-APB as indicated. Inset: corresponding IV relationship. (B) Same experimental setting as in (A) but with Orai3 overexpression (n = 10). (C) Same experiment as in (A) but with overexpression of Orai1 and Orai3 in a ratio of 4:1 (n = 12) or (D) with overexpression of concatenated tetrameric channel 3-1-1-1 (n = 12), insets: corresponding IV relationship. The light grey traces are single cell recordings. A calculated CD taken from experiments in (A) and (B) is represented as a dark brown line in (C) (4 × CD from Orai1 + 1 × CD from Orai3 divided by 5). (E) Extracted inward current densities from (C) + (D) at t = 116 s and t = 178 s. Single data points and mean values ± SD are shown. In addition, SD is stated as s. (F) same as in (E) but with extracted outward currents at the same time points.