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Volume 272, Number 19, Issue of May 9, 1997 pp. 12373-12379
©1997 by The American Society for Biochemistry and Molecular Biology, Inc.

Angiotensin II Stimulates Tyrosine Phosphorylation and Activation of Insulin Receptor Substrate 1 and Protein-tyrosine Phosphatase 1D in Vascular Smooth Muscle Cells

(Received for publication, September 19, 1996, and in revised form, February 19, 1997)

From the ^a Departments of Pathology and ^c Medicine, ^f Renal and ^c Cardiology Divisions, and ^g The Center for Cell and Molecular Signaling, Emory University School of Medicine and ^f Veterans Affairs Medical Center, Atlanta, Georgia 30322

Angiotensin II (Ang II) and insulin-like growth factor I (IGF I) stimulate intracellular signaling events through binding to their respective G-protein-coupled and growth factor receptors. In rat aortic vascular smooth muscle cells, IGF I (20 ng/ml) induced a sustained (>30 min) increase in the tyrosine phosphorylation of both Src-homology 2 domain-docking insulin receptor substrate 1 (IRS-1) and Src-homology 2-binding tyrosine phosphatase 1D (PTP-1D). In addition, IGF I stimulated PTP-1D phosphatase activity. Ang II (10⁷ M) also increased the tyrosine phosphorylation of IRS-1 (4-fold), PTP-1D (5-fold), and PTP-1D activity (3-4-fold), but with a more transient time course. Ang II also induced PTP-1D·IRS-1 complex formation. These Ang II-induced events were not affected by preincubation with an anti-IGF I antibody, suggesting that Ang II's actions were not mediated via the autocrine secretion of IGF I. Anti-PTP-1D antibody electroporation attenuated Ang II-induced PTP-1D·IRS-1 complex formation and PTP-1D tyrosine phosphorylation and activation. Our findings show that the tyrosine phosphorylation of IRS-1 and PTP-1D represents a convergent intracellular signaling cascade stimulated by both growth factor (i.e. IGF I) and G-protein-coupled (i.e. AT₁) receptors.

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