Fig. 7

CaSR^R62A is not inhibited by Pi. CaSR^R62A-induced \({\mathrm{Ca}}_i^{2 + }\)-mobilization is not sensitive to Pi upon stimulation with Ca²⁺ (a, n = 7), or cotreatment with R568 (b, n = 10). c CaSR^R62A-induced \({\mathrm{Ca}}_i^{2 + }\)-mobilization is also insensitive to SO₄ (n = 8). a–c Area under the curve was calculated for each treatment and normalized against maximal response. d Cell surface expression levels of CaSR^WT, CaSR^R62A, and known defective mutants measured in transiently transfected HEK cells with non-transfected HEK-293 cells (NT) used as negative controls (n = 9, performed in triplicate; NT, n = 6). Data normalized to CaSR^WT (WT) total expression levels. e Ca²⁺ concentration−effect curves for \({\mathrm{Ca}}_i^{2 + }\)-mobilization on CaSR^R62A (with 0, 0.8, or 2 mM Pi) and CaSR^WT (without Pi, shown here for comparison purposes). Data fitted to a four-parameter Hill equation (Eq. (1)) for sigmoidal concentration−response variable slope (n = 8–10, from three independent experiments). Data fitted best when EC₅₀ (shown as mean with 95% confidence interval) values for \({\mathrm{Ca}}_o^{2 + }\) were different among data sets and E_max was shared, P < 0.01 extra sum-of-square F-test. f Representative immunoblot showing pERK responses by CaSR^R62A and CaSR^WT after a 10-min stimulation; 0.5 mM Ca²⁺ used as negative control. Changes in pERK were corrected for β-actin abundance and then normalized to the Pi-free stimulated control (n = 8, from four independent experiments). Data are plotted as %mean ± SEM and analyzed by using RM-ANOVA, Dunnett’s multiple comparisons (b–e), or unpaired t test (a, f). ns not significant, ^*P < 0.05 and ^**P < 0.01. Source data are provided as a Source Data file