Loss-of-function Gαs rare disease variants exert mutation-specific effects on GPCR signaling

Abstract

G protein–coupled receptors (GPCRs) are transmembrane detectors of extracellular signals that activate heterotrimeric G proteins to regulate intracellular responses. Because there are only 16 Gα proteins that can couple to GPCRs, variation in a single Gα can affect the function of numerous receptors. Here, we investigated two mutant forms of Gα_s (L388R and E392K) that are associated with pseudohypoparathyroidism type Ic (PHPIc), a maternally inherited rare disease. Gα_s is encoded by an imprinted gene, resulting in the mutant form of Gα_s being the only version of the protein present in certain tissues, which leads to tissue-specific disease manifestations. By integrating data from three-dimensional structures, GPCR–G protein coupling specificity, transcriptomics, biophysics, and molecular dynamics with systems pharmacology modeling, we identified GPCRs whose signaling could be altered by Gα_s mutations in the kidney, a tissue involved in the pathophysiology of PHPIc. Analysis of G protein activation by the parathyroid hormone receptor 1 (PTH1R) revealed that L388R impaired Gα_s interaction with the receptor, whereas E392K reduced the receptor-induced activation of heterotrimeric G_s. This indicates that different signal transduction steps can be altered by specific Gα_s mutants associated with the same disease. These findings highlight the importance of investigating mutation-specific perturbations in GPCR signaling to suggest patient-specific treatment strategies. Furthermore, our methods provide a blueprint for interrogating GPCR signaling diversity in different physiological and pathophysiological contexts.