Figure 5. Evidence for a close proximity of KCa3.1 and CRAC/Orai1 channels.

A. A representative whole-cell recording from an MLS-9 microglia cell with internal Ca²⁺ buffered to 120 nM using 1 mM of the fast Ca²⁺ buffer, BAPTA. The two traces show currents before (control) and after 100 µM UTP was added to the bath. The voltage protocol was the same as in Figures 1 and 2; i.e., a voltage step to +50 mV was followed by a voltage ramp from −100 to +80 mV (holding potential, −70 mV). B. Comparison of the KCa3.1 current amplitude at +80 mV. Intracellular Ca²⁺ was buffered to 120 nM with either 1 mM EGTA or 1 mM BAPTA (*p<0.05, Student's t-test). C. High-magnification, deconvolved images of MLS-9 cells show immunolabeling for KCa3.1 (red), Orai1 (green), and the nuclear marker, DAPI (blue) (scale bar  = 10 µm). Below the main panels are magnifications of the two boxed areas in the merged image (scale bars = 2 µm).