Extended Data Fig. 8: CaSR-G-protein interactions.
From: Promiscuous G-protein activation by the calcium-sensing receptor
a, b, Barcode presentations of CaSR (a) and Gα (b) residues that take part in the CaSR-G-protein interfaces of our five complexes. Stars designate residues with functional significance as per our mutational analyses. In (a), filled circles indicate G-protein-binding residues of CaSR that are common to all five complexes (green) or in specific complexes (gray). Empty circles represent CaSR residues not in contact with G protein. Dotted circles mark disordered residues. In (b), G-protein residues that contact CaSR in complexes bearing miniGisq (cyan), Gi3 (green), miniGi1 (green) or miniGis (blue) are interspersed with those that lack contact with the receptor (empty). c, d, Functional analysis of G-protein-binding residues in CaSR. Ca2+ potency (EC50) and maximal response (Emax) of wild-type and mutant receptors are compared for Gq, Gi3 and Gi1 (c) as well as Gq, Gqi9 and Gqs5 (d) using BRET-based G-protein activation and IP1 accumulation assay, respectively. e, Analysis of Ca2+ potency (EC50) and maximal response (Emax) of wild-type CaSR-mediated IP1 accumulation through wild-type or mutant Gαq. Ca2+-stimulated IP1 accumulation was measured in Gαq/11-knockout HEK293 cells co-transfected with either wild-type or mutant Gαq. C-ter, C-terminal tail (a,c,d). Bar segments represent averages ± s.e.m, with the number of independent experiments (n) indicated (c-e). One-way analysis of variance (ANOVA) with Dunnett’s multiple comparison test was used to calculate statistical differences in EC50 and Emax between wild-type and mutant receptors. ND stands for not determined due to an incomplete response curve within the dose concentration range tested. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001; ns, not significant. Cell surface expression levels of wild-type and mutant CaSR are described in the Methods (c,d).
