Fig. 2. EYFP-STIM1 colocalizes with -tubulin. (A) Upper panel: confocal images of an HEK 293 cell co-overexpressing EYFP-STIM1 (left panel; green) and mCherry--tubulin (middle panel; red) in the presence of 1.8 mM extracellular Ca²⁺. The arrowheads indicate a track of EYFP-STIM1 fluorescence that exactly matches a corresponding track of mCherry--tubulin fluorescence. Lower panel: EYFP-STIM1 and mCherry--tubulin localization 15 minutes following Ca²⁺ store depletion with thapsigargin (Tg; 2 µM) in a nominally Ca²⁺-free extracellular solution. (B) Upper panel: confocal images of an HEK 293 cell overexpressing EYFP-STIM1 that was fixed and immunostained with antibodies against EYFP (to enhance detection of EYFP-STIM1) (left panel; green) and -tubulin (middle panel; red). Lower panel: an HEK 293 cell that was store depleted with thapsigargin for 15 minutes before fixation and immunostaining. Arrowheads indicate a track of -tubulin along which several EYFP-STIM1 puncta appear to associate. Bars, 10 µm.