Fig. 2. Rearrangements of both Stim1 and Orai1 are reversed by Ca²⁺ store refilling. (A) Confocal images of HEK293 cells co-overexpressing EYFP-Stim1 and the m5 muscarinic receptor in the presence of 1.8 mM extracellular Ca²⁺ before store depletion (left panel), 10 minutes following treatment with 300 µM carbachol in nominally Ca²⁺-free extracellular solution (center panel), and 10 minutes following restoration of 1.8 mM extracellular Ca²⁺ in the presence of 50 µM atropine (right panel). (B) The same protocol described in panel A was repeated with cells co-overexpressing EYFP-Stim1, CFP-Orai1 and the m5 muscarinic receptor. EYFP-Stim1 fluorescence is shown in the upper row, CFP-Orai1 is shown in the center row, and the bottom row shows merged images of EYFP-Stim1 (green) and CFP-Orai1 (red). Bars, 10 µm.