Fig. 2. Comparison between human PMCA3a wt and mutant E1081Q activity on cytosolic and ER Ca²⁺ handling.

a, b Kinetic of ER release of the full-length wt and E1081Q mutant pump. HeLa cells were co-transfected with cytAEQ and the PMCA3a constructs stimulated with histamine 100 μM and CPA (20 μM) and in the absence of extracellular Ca²⁺ (100 μM EGTA). c, d HeLa cells were co-transfected with erAEQ (targeted to the ER lumen) and the PMCA3a constructs. ER refilling upon re-addition of 1 mM CaCl₂ to Ca²⁺-depleted cells in HeLa cells either mock transfected or overexpressing PMCA3a wt or E1081Q. e, f Effect full length PMCA3a and mutant E1081Q pump on the influx of Ca²⁺ from the extracellular medium. HeLa cells were co-transfected with cytAEQ and the PMCA3a constructs. All the traces refer to representative experiments selected from at least three independent experiments. Quantifications for panels a–c are shown respectively in panels b–f. Bars represent means ± SEM obtained by averaging the values obtained in at least 30 independent measurements from three independent transfections for each condition. *, p < 0.05: **, p < 0.01: ***, p < 0.001; ****, p < 0.0001: ns not significant.