CDI does not require a specific diffusible cytosolic anion. All currents were recorded from cells expressing WT mCh-STIM1 and WT Orai1-GFP as described in Fig. 3, with adjustments to the internal solution (see Materials and methods). The standard aspartate-based internal solution (A, same traces shown in Fig. 3 A) was substituted with sucrose (B) and HEPES (C), with the extent of CDI summarized in (D). Next, internal solutions were varied to include a range of chloride concentrations, from 0 (E) to 16 mM (F, same traces shown in Fig. 3 A) to 166 mM Cl⁻ (G), with extent of CDI summarized in H. Each point on the summary graphs represents the mean ± SEM for n = 5–6 cells.