Angiotensin II stimulates phosphorylation of 4E-binding protein 1 and p70 S6 kinase in cultured vascular smooth muscle cells

AIM: To examine the regulatory effects of angiotensin II (Ang II) on the phosphorylation of 4E-binding protein 1 (4E-BP1) and p70 S6 kinase in cultured vascular smooth muscle cells (VSMC), and the contribution of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB) signaling pathway in this process. METHODS: VSMC obtained from rat thoracic aortas were cultured. The phosphorylation of 4E-BP1 and p70 S6 kinase was detected by immunoblotting. RESULTS: Ang II significantly increased the phosphorylation of 4E-BP1 and p70 S6 kinase, with the peaks occurring at, respectively, 10 min and 30 min, after stimulation with Ang II. The stimulatory effect of Ang II on 4E-BP1 and p70 S6 kinase phosphorylation was abrogated by Ang II type 1 receptor (AT(1) receptor) antagonist losartan, and suppressed by PI3K inhibitor LY294002 in a concentration-dependent manner. CONCLUSION: Ang II treatment of VSMC induces the phosphorylation of 4E-BP1 and p70 S6 kinase via AT(1) receptor, and PI3K signaling pathway is involved in this process.