Loss-of-function mutations in human regulator of G protein signaling RGS2 differentially regulate pharmacological reactivity of resistance vasculature

Abstract

Regulator of G protein signaling 2 (RGS2) plays a role in reducing vascular contraction and promoting relaxation due to its GTPase accelerating protein activity toward Gαq. Previously, we identified four human loss-of-function (LOF) mutations in RGS2 (Q2L, D40Y, R44H, and R188H). This study aimed to investigate whether those RGS2 LOF mutations disrupt the ability of RGS2 to regulate vascular reactivity. Isolated mesenteric arteries (MAs) from RGS2-/- mice showed an elevated contractile response to 5 nM angiotensin II and a loss of acetylcholine (ACh)–mediated vasodilation. Reintroduction of a wild-type (WT) RGS2-GFP plasmid into RGS2-/- MAs suppressed the vasoconstrictor response to angiotensin II. RGS2 LOF mutants failed to suppress the angiotensin II constriction response compared with RGS2 WT. In contrast, ACh-mediated vasoconstriction was restored by expression of RGS2 WT, D40Y, and R44H but not by RGS2 Q2L or R188H. Phosphorylation of RGS2 D40Y and R44H by protein kinase G (PKG) may explain their maintained function to support relaxation in MAs. This is supported by phosphomimetic mutants and suppression of vasorelaxation mediated by RGS2 D40Y by a PKG inhibitor. These results demonstrate that RGS2 attenuates vasoconstriction in MAs and that RGS2 LOF mutations cannot carry out this effect. Among them, the Q2L and R188H mutants supported less relaxation to ACh, whereas relaxation mediated by the D40Y and R44H mutant proteins was equal to that with WT protein. Phosphorylation of RGS2 by PKG appears to contribute to this vasorelaxation. These results provide insights for precision medicine targeting the rare individuals carrying these RGS2 mutations. SIGNIFICANCE STATEMENT Regulator of G protein signaling 2 (RGS2) has been implicated in the control of blood pressure; rare mutations in the RGS2 gene have been identified in large-scale human gene sequencing studies. Four human mutations in RGS2 that cause loss of function (LOF) in cell-based assays were examined in isolated mouse arteries for effects on both vasoconstriction and vasodilation. All mutants showed the expected LOF effects in suppressing vasoconstriction. Surprisingly, the D40Y and R44H mutant RGS2 showed normal control of vasodilation. We propose that this is due to rescue of the mislocalization phenotype of these two mutants by nitric oxide–mediated/protein kinase G–dependent phosphorylation. These mechanisms may guide drug discovery or drug repurposing efforts for hypertension by enhancing RGS2 function.