FIGURE 8.
Ca2+ store depletion but not cAMP induces STIM1-Orai1 co-clustering in islet cells. A, TIRF images of an islet cell co-expressing STIM1-YFP (green) and Orai1-mCherry (red). The cell was initially exposed to 20 mm glucose while hyperpolarized with 250 μm of the KATP channel activator diazoxide (basal). Subsequently 5 μm forskolin and 50 μm CPA were added. The top and middle rows show STIM1 and Orai1 images, respectively, and the bottom row shows a STIM1/Orai1 overlay. The images represent averages of 25 consecutive frames under each condition. B and C, changes in mean STIM1-YFP and Orai1-mCherry fluorescence intensity ± S.E. in 25 ROIs based on selection of STIM1 puncta that were formed after exposure to CPA. D and E, changes in mean STIM1-YFP and Orai1-mCherry fluorescence intensity ± S.E. in 18 ROIs based on selection of STIM1 puncta that were formed after exposure to forskolin. F, overlay image of STIM1 after exposure to forskolin (red) and CPA (green). Image scale bars indicate 1 μm.