Fig. 1.

Store-dependent control of Orai and Ca_V1.2 channels. Fura-2 F₃₄₀/F₃₈₀ ratiometric responses to cytosolic Ca²⁺ in A7r5 VSMCs in response to 100 nM VP (A) or 2 μM TG (B), in control or Orai1-E106A-CFP–transfected cells in nominally Ca²⁺ free or 3 mM external Ca²⁺ (bars). (Inset) Current-voltage curve for CRAC channels in control A7r5 cells. (C) Fura-2 responses in control and STIM1-D76A–transfected A7r5 cells (bars, 3 mM external Sr²⁺ or Ca²⁺). (D) Fura-2 responses to application of external 134 mM K⁺ with 3 mM Sr²⁺ (bars, K⁺/Sr²⁺); 2 μM nimodipine (arrow). (E) Fura-2 responses to two sequential K⁺/Sr²⁺ pulses (bars) with addition of dimethyl sulfoxide (DMSO) or 2 μM ionomycin (arrow), and subsequent 2 μM nimodipine addition. (F) As in (E), except with the addition of 100 nM VP. (G) Statistics for results in (E), (F), and TG (trace not shown) (n = 6, paired t test). (H) I/V curve for whole-cell Ba²⁺ current through Ca_V1.2 channels in A7r5 cells with cytosolic Ca2+ clamped to 0.1 μM (10 mM EGTA; 3.4 mM CaCl₂), either before (left) or 5 min after store depletion with 2 μM ionomycin, 100 nM VP, or control (right). (I to K) Fura-2 responses to K⁺/Sr²⁺ (bars) in HEK293 cells expressing three Ca_V1.2 subunits (α_1C+ β_2a+ α₂δ₁) or control-transfected cells. (I) K⁺/Sr²⁺ responses in Ca_V1.2-transfected and control-transfected cells; 2 μM nimodipine (arrow); inset, I/V curve for Ca_V1.2-transfected cells (n = 4). (J) Fura-2 responses to sequential K⁺/Sr²⁺ pulses (bars) with additions of DMSO or 2 μM ionomycin (arrow), and 2 μM nimodipine (arrows). (K) K⁺/Sr² responses after DBHQ (10 μM, 10 min, present throughout) or TPEN (250 μM, 5 min, removed at K⁺/Sr²⁺ addition).