FIGURE 3.

Effect of the truncated and full length wt and mutant pump on the influx of Ca²⁺ from the extracellular medium. HeLa cells were co-transfected with cytAEQ and the PMCA3 constructs, or transfected with cytAEQ only, pretreated with 1 μm thapsigargin and 100 μm histamine in a buffer containing 1 mm EGTA for 3 min and perfused in the presence of KRB/Ca²⁺ 3 mm to stimulate Ca²⁺ entry from the extracellular ambient. The Ca²⁺ transients in panel A for the PMCA3a isoform and in panel D for the b variant are characterized by a first peak and a plateau phase (as indicated). Enlargements of the plateau phases are shown in the insets. Panels B and E show the averaged peak [Ca²⁺] values obtained upon stimulation and panels C and F show the obtained averaged [Ca²⁺] values of the plateau. Bars represent means ± S.E. obtained by averaging the values obtained in at least 18 independent measurements from six independent transfections for each condition. ***, p < 0.001; ns, not significant.