The Rho/Rac exchange factor Vav2 controls nitric oxide–dependent responses in mouse vascular smooth muscle cells
Vincent Sauzeau, María A. Sevilla, María J. Montero, Xosé R. Bustelo
Vincent Sauzeau, María A. Sevilla, María J. Montero, Xosé R. Bustelo
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Research Article Vascular biology

The Rho/Rac exchange factor Vav2 controls nitric oxide–dependent responses in mouse vascular smooth muscle cells

Abstract

The regulation of arterial contractility is essential for blood pressure control. The GTPase RhoA promotes vasoconstriction by modulating the cytoskeleton of vascular smooth muscle cells. Whether other Rho/Rac pathways contribute to blood pressure regulation remains unknown. By studying a hypertensive knockout mouse lacking the Rho/Rac activator Vav2, we have discovered a new signaling pathway involving Vav2, the GTPase Rac1, and the serine/threonine kinase Pak that contributes to nitric oxide–triggered blood vessel relaxation and normotensia. This pathway mediated the Pak-dependent inhibition of phosphodiesterase type 5, a process that favored RhoA inactivation and the subsequent depolymerization of the F-actin cytoskeleton in vascular smooth muscle cells. The inhibition of phosphodiesterase type 5 required its physical interaction with autophosphorylated Pak1 but, unexpectedly, occurred without detectable transphosphorylation events between those 2 proteins. The administration of phosphodiesterase type 5 inhibitors prevented the development of hypertension and cardiovascular disease in Vav2-deficient animals, demonstrating the involvement of this new pathway in blood pressure regulation. Taken together, these results unveil one cause of the cardiovascular phenotype of Vav2-knockout mice, identify a new Rac1/Pak1 signaling pathway, and provide a mechanistic framework for better understanding blood pressure control in physiological and pathological states.

Authors

Vincent Sauzeau, María A. Sevilla, María J. Montero, Xosé R. Bustelo

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Figure 10

Pak1 inhibits PDE5 in a phosphorylation-independent manner.

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Pak1 inhibits PDE5 in a phosphorylation-independent manner. (A) In vitro...
(A) In vitro PDE5 enzyme activity under the indicated conditions (n = 4, each performed in triplicate). Data are shown as mean ± SEM. (B–D) The indicated GST-PDE5 fusion proteins (labeled as in Figure 9C) (B–D) alone or in combination with histone 1 (B) were subjected to in vitro kinase reactions in the presence of GST-Pak1 (B), PKA (C), and cGKIα (D). We also included reactions of kinases without PDE5 proteins (none, B–D). (E) The indicated Pak1 proteins (top) were expressed in COS1 cells and subjected to pulldown experiments with either the GST-PDE5-1 fusion protein (see Figure 9C) or the nonchimeric GST protein. The pulled down material (top panel) and aliquots of the total cellular lysates (bottom panel) used in the pulldown experiments were analyzed by anti-Pak1 immunoblot.