The smooth muscle-selective RhoGAP GRAF3 is a critical regulator of vascular tone and hypertension

Abstract

Although hypertension is a worldwide health issue, an incomplete understanding of its etiology has hindered our ability to treat this complex disease. Here we identify arhgap42 (also known as GRAF3) as a Rho-specific GAP expressed specifically in smooth muscle cells in mice and humans. We show that GRAF3-deficient mice exhibit significant hypertension and increased pressor responses to angiotensin II and endothelin-1; these effects are prevented by treatment with the Rho-kinase inhibitor, Y-27632. RhoA activity and myosin light chain phosphorylation are elevated in GRAF3-depleted smooth muscle cells in vitro and in vivo, and isolated vessel segments from GRAF3-deficient mice show increased contractility. Taken together our data indicate that GRAF3-mediated inhibition of RhoA activity in vascular smooth muscle cells is necessary for maintaining normal blood pressure homeostasis. Moreover, these findings provide a potential mechanism for a hypertensive locus recently identified within arhgap42 and provide a foundation for the future development of innovative hypertension therapies.

Blood pressure–associated polymorphism controls ARHGAP42 expression via serum response factor DNA binding

“…We have previously shown that the Rho-specific GTPase-activating protein ARHGAP42 is highly and selectively expressed in SMCs and that global gene-trap-mediated reduction in ARHGAP42 levels resulted in hypertension (11). By characterizing the transcription mechanisms that control human ARHGAP42 expression, we have now identified a novel mechanism for the BP-associated locus within the ARHGAP42 first intron.…”

“…In brief, thoracic aortae were stripped of endothelial and adventitial layers by microdissection, and then SMCs were dispersed by treatment with trypsin and collagenase. Cells were maintained in DMEM supplemented with F12 and 10% FBS and used from passages [5][6][7][8][9][10][11][12][13][14][15]. SMC preparations are routinely tested for smooth muscle differentiation marker gene expression, and only those that are deemed at least 85% pure by these measurements are used for further experimentation.…”

“…Based on our demonstration that ARHGAP42 was highly and selectively expressed in smooth muscle in mouse and human tissues (11) and the fact that Rho GTPase RhoA signaling controls smooth muscle cell (SMC) contractility (12), we hypothesized that ARHGAP42's association with BP was mediated by its ability to modulate vascular resistance. Indeed, Arhgap42-deficient mice exhibited significant hypertension and increased pressor responses to ANGII and endothelin 1, and these effects were prevented by treatment with the Rho kinase (ROCK) inhibitor Y-27632 (11). Further supporting this idea, we showed that large and small arteries from Arhgap42-deficient mice exhibited increased contractility in vitro and in vivo, while kidney structure and function were unchanged.…”

ARHGAP42 promotes cell migration and invasion involving PI3K/Akt signaling pathway in nasopharyngeal carcinoma

“…ARHGAP42 (also known as GRAF3) is a GTPase‐activating protein 12. Rho family small GTPases regulate cellular functions, including diverse cytoskeleton‐related events, gene transcription, and immune cell migration and inflammation 13.…”

“…The Rho GTPase‐activating proteins (Rho‐GAPs) are one of the most important types of regulators of Rho GTPases 16. A previous study has identified ARHGAP42 as a Rho‐specific GAP expressed specifically in smooth muscle cells (SMCs) in mice and humans 12. The study has indicated that ARHGAP42‐mediated inhibition of RhoA activity in vascular SMCs is necessary to maintain normal blood pressure homeostasis.…”