Effect of Orai1(R91W), STIM1, and STIM1(K684E,K685E) on TRPC5 and TRPC5(D651K,E652K) currents. A–C, HEK cells were transfected with M3 receptors; TRPC5 (C5); and empty vector (thin black traces), Orai1(R91W) (thick black traces), or Orai1(R91W) + STIM1 (O1(R91W)+S1; gray traces). D–F, HEK cells were transfected with M3 receptors; TRPC5(D651K,E652K) (TRPC5(DE/KK), C5(DE/KK)); and empty vector (thin black traces), Orai1(R91W) (thin gray traces), STIM1 (thick gray traces), or STIM1(K684E,K685E) (S1(KK/EE); thick black traces). The Na+ current was measured as described under “Materials and Methods.” A and D, examples of the time dependence of the current; B and E, I/V at peak current; C and F, mean ± S.E. of current density in pA/pF from the indicated number of experiments. *, p < 0.01 relative to the respective controls.