In silico study on the internal signal pathway of different mutants of vasopressin receptor 2 with arginine vasopressin bound.

Abstract

The vasopressin receptor 2 (V2R) belongs to rhodopsin superfamily of G-protein coupled receptors (GPCRs), commonly expressed in collecting duct which promotes kidney water reabsorption. The antidiuretic hormone arginine vasopressin (AVP) is the endogenous ligand for V2R, which acts as an agonist playing a crucial role in water reabsorption and the stability in homeostasis and blood pressure. Mutation in V2R could lead to kidney-related diseases such as congenital nephrogenic diabetes insipidus, nephrogenic syndrome of inappropriate antidiuresis and autosomal dominant polycystic kidney disease. However, the signaling difference and conformational change of V2R induced by these mutations are still unclear. In this study, four V2R systems, including wild-type (V2R-WT), partially active mutant (V2R-D136A), and inactive mutant (V2R-ΔV279, V2R-M272R) were built using homology modeling method to study the molecular switches and internal signal pathways as the ligand AVP bound and compare with recently resolved AVP-V2R-Gs complex structure. Molecular docking of AVP to V2Rs was performed for these systems and then these complex systems were embedded into a POPC lipid bilayer for long term all-atom molecular dynamic (MD) simulations. The results showed that the intracellular loop 3 (ICL3) swings differently in these systems, especially in V2R-ΔV279, and V2R-M272R systems. The ICL3 swung back to cover the intracellular region of V2R to inhibit Gs-protein coupling. However, in the V2R-D136A system, ICL3 swung outward to enlarge intracellular region for Gs-protein binding. Distance between Y7.53 and Y5.58 also showed decrease in active mutant while increase in inactive mutant, consistent with other GPCR structures. Communication transduction pathways calculated showed more pathways for active mutant system than other inactive systems. This study provides atomic-level insights for the structural and functional importance of V2R.