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Angiotensin II controls p21ras activity via pp60c-src
B Schieffer1, W G Paxton, Q Chai
1Department of Pathology Center for Molecular and Cellular Signaling, Emory University, Atlanta, Georgia 30322, USA.
Abstract:
Angiotensin II is the major effector peptide of the renin-angiotensin system, and it exerts its physiologic functions via a G protein-coupled cell surface receptor called AT1. We found that in rat aortic smooth muscle cells, angiotensin II stimulated the formation of Ras-GTP, Ras-Raf-1 complex formation, and the tyrosine phosphorylation of two important Ras GTPase-activating proteins (GAPs), p120 Ras-GAP and p190 Rho-GAP. Electroporation of anti-pp60c-src antibody into cultured, adherent smooth muscle cells blocked the angiotensin II stimulation of Ras-GAP and Rho-GAP tyrosine phosphorylation. In contrast electroporation of antibodies against c-Yes or c-Fyn had no effect. Anti-pp60c-src antibody also blocked angiotensin II-stimulated Ras activation and Ras-Raf-1 complex formation. These data strongly suggest that a G protein-coupled receptor such as the AT1 receptor can activate the Ras protein cascade via the tyrosine kinase pp60c-src.
Insights
Angiotensin II activates the Ras protein cascade through the AT1 receptor and the tyrosine kinase pp60c-src. This study reveals a novel signaling pathway involving Ras-GTP, Ras-Raf-1 complex, and tyrosine phosphorylation of Ras GTPase-activating proteins.
Area of Science:
- Molecular Biology
- Cell Signaling
- Cardiovascular Research
Background:
- The renin-angiotensin system's primary effector peptide, Angiotensin II, mediates physiological functions through the AT1 receptor.
- Understanding the downstream signaling pathways activated by Angiotensin II is crucial for cardiovascular research.
Purpose of the Study:
- To investigate the role of the tyrosine kinase pp60c-src in Angiotensin II-mediated signaling via the AT1 receptor.
- To elucidate the involvement of Ras protein cascade activation in response to Angiotensin II stimulation.
Main Methods:
- Utilizing rat aortic smooth muscle cells to study Angiotensin II signaling.
- Employing electroporation of specific antibodies (anti-pp60c-src, anti-c-Yes, anti-c-Fyn) to block protein activity.
- Assessing the formation of Ras-GTP and Ras-Raf-1 complexes.
- Measuring the tyrosine phosphorylation of p120 Ras-GAP and p190 Rho-GAP.
Main Results:
- Angiotensin II stimulated Ras-GTP formation, Ras-Raf-1 complex formation, and tyrosine phosphorylation of p120 Ras-GAP and p190 Rho-GAP.
- Blocking pp60c-src activity with an antibody inhibited Angiotensin II-induced tyrosine phosphorylation of GAPs and Ras activation.
- Inhibition of c-Yes or c-Fyn did not affect these signaling events.
- pp60c-src is implicated in mediating Angiotensin II-stimulated Ras activation and Ras-Raf-1 complex formation.
Conclusions:
- The AT1 receptor activates the Ras protein cascade through the tyrosine kinase pp60c-src.
- pp60c-src plays a critical role in Angiotensin II-induced smooth muscle cell signaling.
- This study identifies a novel signaling mechanism linking G protein-coupled receptors to the Ras pathway.