Endothelial β2 adrenergic signaling to AKT:: Role of Gi and SRC

We have recently demonstrated that endothelial beta(2) adrenergic receptors beta(2)AR regulate eNOS activity and consequently vascular tone, through means of PKB/AKT. In this work we explored the signal transduction pathway leading to AKT/eNOS activation in endothelial cells (EC). Using pharmacological and molecular inhibitors both in cultured EC cells and in ex vivo rat carotid preparations, we found that G(i) coupling of the beta 2AR is needed for AKT activation and vasorelaxation. Since endothelial activation is sensitive to pertussis toxin but not to G(i beta gamma), inhibition by beta ARKct, we conclude that G(alpha i) mediates beta AR induced AKT activation. Downstream, beta AR signalling requires the soluble tyrosine kinase SRC, as both in cultured EC and rat carotid, the mutant dominant negative of SRC prevent beta(2)AR induced endothelial activation and vasodilation. In EC, G(alpha i) directly interacts with SRC and this interaction leads to SRC activation and phosphorylation in a manner that is regulated by Balk stimulation. We propose a novel signal transduction pathway for beta(2)AR stimulation trough G(alpha i) and SRC, leading to activation of AKT. (c) 2007 Elsevier Inc. All rights reserved.