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Department of Pharmacy, Center of Drug Research, University of Munich, Munich, Germany (U.G.B.H., T.U.R., A.M.V., V.M.D.); Cancer Biology Program, Beth Israel Deaconess Medical Center, Boston, Massachusetts (M.I.K., B.G.N.); and Department of Medicine, Division of Cardiology, Emory University, Atlanta, Georgia (D.S., K.K.G.)
trans-Resveratrol (RV), a polyphenolic stilbene derivative found in grape skin and other food products, has been proposed to exert beneficial effects in cardiovascular disease. Our group has shown previously that RV inhibits angiotensin II (Ang II)-induced Akt activation and, consequently, vascular smooth muscle cell (VSMC) hypertrophy. In this work, to identify the molecular target of RV, we investigated the impact of RV on early signaling cascades in rat aortic VSMCs triggered by Ang II and epidermal growth factor (EGF). We show that RV does not influence Ang II-mediated transactivation of EGF-receptor but potently inhibits EGF-induced phosphorylation of Akt kinase, suggesting that RV acts downstream of EGF-receptor transactivation in VSMCs. Recent evidence indicates that the adapter molecule Gab1, together with the protein tyrosine phosphatase Shp2, is critically involved in regulating the strength and duration of phosphatidylinositol-3-kinase (PI3K) and Akt activation upon EGF stimulation in fibroblasts. Our results show that stimulation of VSMCs with EGF as well as Ang II leads to a rapid tyrosine phosphorylation of Gab1 and its association with the p85 subunit of PI3K. RV attenuates these processes. Experiments performed in Shp2-deficient fibroblasts revealed that RV does not inhibit EGF-stimulated Akt activation in these cells, suggesting that Shp2 is necessary for the inhibitory effect of RV on the PI3K/Akt pathway. Furthermore, RV treatment activates Shp2. We therefore propose that RV blocks Akt activation in Ang II- and EGF-stimulated VSMCs by activating Shp2, thus preventing interaction between Gab1 and PI3K that is necessary for further signal transduction.
Address correspondence to: Dr. Verena M. Dirsch, Department of Pharmacy, Center of Drug Research, Butenandtstrasse 5–13, D-81377 Munich, Germany. E-mail: verena.dirsch{at}cup.uni-muenchen.de
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