β-Arrestin 1 Inhibits the GTPase-Activating Protein Function of ARHGAP21, Promoting Activation of RhoA following Angiotensin II Type 1A Receptor Stimulation

Abstract

Activation of the small GTPase RhoA following angiotensin II stimulation is known to result in actin reorganization and stress fiber formation. Full activation of RhoA, by angiotensin II, depends on the scaffolding protein ␤-arrestin 1, although the mechanism behind its involvement remains elusive. Here we uncover a novel partner and function for ␤-arrestin 1, namely, in binding to ARHGAP21 (also known as ARHGAP10), a known effector of RhoA activity, whose GTPase-activating protein (GAP) function it inhibits. Using yeast two-hybrid screening, a peptide array, in vitro binding studies, truncation analyses, and coimmunoprecipitation techniques, we show that ␤-arrestin 1 binds directly to ARHGAP21 in a region that transects the RhoA effector GAP domain. Moreover, we show that the level of a complex containing ␤-arrestin 1 and ARHGAP21 is dynamically increased following angiotensin stimulation and that the kinetics of this interaction modulates the temporal activation of RhoA. Using information gleaned from a peptide array, we developed a cell-permeant peptide that serves to inhibit the interaction of these proteins. Using this peptide, we demonstrate that disruption of the ␤-arrestin 1/ARHGAP21 complex results in a more active ARHGAP21, leading to lessefficient signaling via the angiotensin II type 1A receptor and, thereby, attenuation of stimulated stress fiber formation.

βArrestin1 Regulates the Guanine Nucleotide Exchange Factor RasGRF2 Expression and the Small GTPase Rac-mediated Formation of Membrane Protrusion and Cell Motility

“…Activation of the angiotensin II type 1A receptor facilitated association of ␤Arr1 with the RhoGAP ARHGAP21, and consequent inhibition of the GTPase-activating proteins contributed to higher RhoA activity (16). Angiotensin II type 1A receptor was also shown to mediate RhoA activation through both ␤Arr1 and G q (13), as well as through JAK2-mediated phosphorylation of p115RhoGEF (17).…”

β-Arrestin-Mediated Signaling Improves the Efficacy of Therapeutics

“…This pathway is dependent upon β-arrestin-1 but not β-arrestin-2 (11). Although the exact mechanisms of β-arrestin-1-mediated RhoA/ROCK signaling are still under investigation, it has been reported that β-arrestin-1 enhances angiotensin II-stimulated RhoA/ROCK signaling by inhibiting ArhGAP (12). The function of ArhGAP is to deactivate RhoA.…”

“…In contrast to G protein-mediated signaling, a β-arrestin-biased agonist selectively activates bone formation. PTH-βarr (D-Trp 12 , Tyr 34 -βPTH ) is found to be a PTH receptor-biased agonist that activates β-arrestin-2 but not classic G protein signaling (24). PTH-βarr stimulated anabolic bone formation, and this effect was greatly decreased in β-arrestin-2-knockout mice (25).…”

“…Angiotensin II binds AT1R and activates G q and G 12 (21,22). Both agonists can decrease blood pressure, increase cardiomyocyte contractility, increase cardiomyocyte performance, and de-crease cardiac fibrosis (22,23).…”

A biosensor to monitor dynamic regulation and function of tumour suppressor PTEN in living cells

“…As the S1PR2 activates PTEN via a RhoAdependent pathway 33 , we tested several other GPCRs, known to stimulate RhoA-dependent signalling in HEK cells but that have not been reported so far to modulate PTEN activity in this system. The angiotensin type 1A receptor (AT1AR) has previously been shown to activate RhoA in HEK cells [34][35][36] . We first confirmed that the AT1AR can activate the Rho/ROCK pathway in HEK cells using an in vitro assay that measures ROCK activity.…”