Molecular Regulation of the RhoGAP GRAF3 and Its Capacity to Limit Blood Pressure In Vivo

Abstract

Anti-hypertensive therapies are usually prescribed empirically and are often ineffective. Given the prevalence and deleterious outcomes of hypertension (HTN), improved strategies are needed. We reported that the Rho-GAP GRAF3 is selectively expressed in smooth muscle cells (SMC) and controls blood pressure (BP) by limiting the RhoA-dependent contractility of resistance arterioles. Importantly, genetic variants at the GRAF3 locus controls BP in patients. The goal of this study was to validate GRAF3 as a druggable candidate for future anti-HTN therapies. Importantly, using a novel mouse model, we found that modest induction of GRAF3 in SMC significantly decreased basal and vasoconstrictor-induced BP. Moreover, we found that GRAF3 protein toggles between inactive and active states by processes controlled by the mechano-sensing kinase, focal adhesion kinase (FAK). Using resonance energy transfer methods, we showed that agonist-induced FAK-dependent phosphorylation at Y376GRAF3 reverses an auto-inhibitory interaction between the GAP and BAR-PH domains. Y376 is located in a linker between the PH and GAP domains and is invariant in GRAF3 homologues and a phosphomimetic E376GRAF3 variant exhibited elevated GAP activity. Collectively, these data provide strong support for the future identification of allosteric activators of GRAF3 for targeted anti-hypertensive therapies.

Rho kinase inhibition ameliorates vascular remodeling and blood pressure elevations in a rat model of apatinib-induced hypertension

“…To this end, a previous study found that GRAF3 -deficient mice exhibited increased susceptibility to DOCA-salt-mediated hypertension [ 28 ]. Results from another in-vivo mouse model showed that even modest induction of GRAF3 in smooth muscle cells significantly decreased basal BP and vasoconstrictor-induced hypertension, indicating that allosteric activators of GRAF3 are targeted antihypertensive drugs [ 29 ]. Therefore, apatinib could be acting by first activating RhoA via GRAF3 inhibition thereby causing vascular remodeling, as evidenced by expression of collagen and increased media thickness of mid-aorta.…”

Fine Mapping of Intracranial Aneurysm Susceptibility Based on a Genome-wide Association Study

“…The role of ARHGAP32 has been mainly investigated in the regulation of blood pressure. Rho-speci c GTPase-activating protein GRAF3 was highly expressed in smooth muscle cells (SMCs) and regulated blood pressure control by inhibiting the contractility of RhoA-mediated SMC 25 . GRAF3-de cient mice also showed increased blood pressure in response to angiotensin II and endothelin 1 26 .…”

Hypertension genetics past, present and future applications

“…Genetically modified mice were used to establish that ARHGAP42 deficiency results in hypertension via increased response to angiotensin II and endothelin‐1 [74]. These models are continuing to be applied to assess whether this candidate gene could be a valid drug target moving forward [75]. Nonetheless, functional validation represents a major challenge due to the large number of SNPs associated with BP.…”