Figure 4.

2-APB-mediated current density responses in HEK 293 WT cells. (A) CD development after overexpression of concatenated tetrameric Orai1/Orai3 channels or empty vector as a control when internal Ca²⁺ is clamped to 200 nM (1-1-1-1, n = 9; 3-1-1-1, n = 7; 3-1-1-3, n = 5; 3-1-3-1, n = 8; 3-1-3-3, n = 9; empty vector, n = 7). Application of 50 μM 2-APB as indicated. (B) Corresponding IV relationships from cells in (A). (C) Analysis of 2-APB-mediated outward currents from (A) at t = 178 s. (D) same experimental setting as in (A) but with 50 μM IP₃ and 0 nM Ca²⁺ in the patch pipette (1-1-1-1, n = 9; 3-1-1-1, n = 13; 3-1-1-3, n = 6; 3-1-3-1, n = 11; 3-1-3-3, n = 8; control, n = 11). (E) Corresponding IV relationships from cells in (D). (F) Analysis of 2-APB-mediated outward currents from (D) at t = 178 s. Statistical significance was determined by an unpaired t test with Welch’s correction and is indicated as ns p > 0.05, * p < 0.05, ** p < 0.005, **** p < 0.0001.