Additional data related to Figs. 4, 5 and 6. (A) Cells were cultured on Matrigel-coated polyacrylamide gels of the indicated stiffness or on glass. The average intracellular Ca²⁺ responses in Fura-2–loaded cells following the application of a Ca²⁺-free solution containing 200 µM ATP are shown for each condition (n = 202 for both WT and dKO cells). (B–D) Mean rise and decay times of Ca²⁺ puff fluorescence were measured during increases and decreases to 20%, 50%, 80%, and 100%, analyzed from the indicated type of MDA-MB-231 (B) or LM2-4 (C) cells shown in Fig. 5 or from MDA-MB-231 STIM dKO control or STIM1, STIM2, or STIM1 D76A–expressing (rescue) cells (D) shown in Fig. 6. (E) Quantification of resting Ca²⁺ levels in the indicated cells following loading with a Ca²⁺ indicator (Fura-2), caged IP3 (ci-IP3/PM), and EGTA-AM. Statistics: one-way ANOVA with Tukey’s post hoc test; *P < 0.05.