![Orai1 channel activity varies widely between puncta independent of STIM1/Orai1 ratio.(A) Plots of Orai1-GCaMP6f ΔF/F0 plateau values measured in response to a 600-ms test pulse to −100 mV. Red rectangles indicate the mean ±2 SD of measurement errors. (B) Scatterplot of ΔF/F0 versus relative STIM1/Orai1 ratio for the six cells shown in A. The cell of origin is indicated by the colored labels shown in A. Note that ΔF/F0 is near zero only for relative STIM1/Orai1 ratios near 1. (C) Scatterplot of ΔF/F0 versus relative STIM1/Orai1 ratio shown for cell A. Note the wide spread of values of ΔF/F0 and relative STIM1/Orai1 ratio for individual puncta from the same cell. (D) Scatterplot of ΔF/F0 versus relative STIM1/Orai1 ratio shown for cell B. Red line corresponds to a curve fit to the Hill equation (Kd = 1.08 [95% CI, 1.02–1.13], hc = 10 [95% CI, 6–17], R2 = 0.45). (E) Scatterplot of A-index versus relative STIM1/Orai1 ratio for the six cells shown in A. Inclusion was restricted to puncta with ΔF/F0 > 0.25. (F) Scatterplot of A-index versus relative STIM1/Orai1 ratio shown for cell F. Note that the A-index declines at low relative STIM1/Orai1 ratios.](https://cdn.rupress.org/rup/content_public/journal/jgp/152/9/10.1085_jgp.201812239/2/jgp_201812239_fig7.png?Expires=1767809341&Signature=pADJeeCSA1b4q4VNDYftWuHX0dwDQrNIAcoXS3~u6RUPehTSCC4ertHVdphrpxYN~SUzKCiTDZMirV9djUdKX3FLyg4z0yvSN8rMMs~qU2WK6OESwpIVC8kEM-qZ6L0026fMy3dryQkpS3eHnvopoF9sf9Y0QOsEks~3Z0~pKXZ9OHiri1bztmMf4rzQ63H94n24hStoFxJDeOa-F0BCm4zM0TwVe3b5Hk~kAZhvhJ83syL1CMzEAwDDdVale0y~9wcFk12hngtXSjgFOBDLzF0qcR4t0qW8saVFn9oMtWJWul1Z5wnz1X61FN7lzNAFTcIBOB1fqU72e8jPMLTxGQ__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
Orai1 channel activity varies widely between puncta independent of STIM1/Orai1 ratio. (A) Plots of Orai1-GCaMP6f ΔF/F0 plateau values measured in response to a 600-ms test pulse to −100 mV. Red rectangles indicate the mean ±2 SD of measurement errors. (B) Scatterplot of ΔF/F0 versus relative STIM1/Orai1 ratio for the six cells shown in A. The cell of origin is indicated by the colored labels shown in A. Note that ΔF/F0 is near zero only for relative STIM1/Orai1 ratios near 1. (C) Scatterplot of ΔF/F0 versus relative STIM1/Orai1 ratio shown for cell A. Note the wide spread of values of ΔF/F0 and relative STIM1/Orai1 ratio for individual puncta from the same cell. (D) Scatterplot of ΔF/F0 versus relative STIM1/Orai1 ratio shown for cell B. Red line corresponds to a curve fit to the Hill equation (Kd = 1.08 [95% CI, 1.02–1.13], hc = 10 [95% CI, 6–17], R2 = 0.45). (E) Scatterplot of A-index versus relative STIM1/Orai1 ratio for the six cells shown in A. Inclusion was restricted to puncta with ΔF/F0 > 0.25. (F) Scatterplot of A-index versus relative STIM1/Orai1 ratio shown for cell F. Note that the A-index declines at low relative STIM1/Orai1 ratios.