mCherry-STIM1 and Orai1-GCaMP6f fluorescence at individual puncta. (A and B) Fluorescence intensity of mCherry-STIM1 (A) and Orai1-GCaMP6f (B) at individual puncta from six different HEK 293A cells held at +20 mV holding potential. (C) Relative STIM1/Orai1 ratios for the same six cells. Red lines indicate the mean.