Eguchi S, Numaguchi K, Iwasaki H, Matsumoto T, Yamakawa T, Utsunomiya H, Motley E D, Kawakatsu H, Owada K M, Hirata Y, Marumo F, Inagami T
Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
J Biol Chem. 1998 Apr 10;273(15):8890-6. doi: 10.1074/jbc.273.15.8890.
We have recently reported that angiotensin II (Ang II)-induced mitogen-activated protein kinase (MAPK) activation is mainly mediated by Ca2+-dependent activation of a protein tyrosine kinase through Gq-coupled Ang II type 1 receptor in cultured rat vascular smooth muscle cells (VSMC). In the present study, we found Ang II rapidly induced the tyrosine phosphorylation of the epidermal growth factor (EGF) receptor and its association with Shc and Grb2. These reactions were inhibited by the EGF receptor kinase inhibitor, AG1478. The Ang II-induced phosphorylation of the EGF receptor was mimicked by a Ca2+ ionophore and completely inhibited by an intracellular Ca2+ chelator. Thus, AG1478 abolished the MAPK activation induced by Ang II, a Ca2+ ionophore as well as EGF but not by a phorbol ester or platelet-derived growth factor-BB in the VSMC. Moreover, Ang II induced association of EGF receptor with catalytically active c-Src. This reaction was not affected by AG1478. These data indicate that Ang II induces Ca2+-dependent transactivation of the EGF receptor which serves as a scaffold for pre-activated c-Src and for downstream adaptors, leading to MAPK activation in VSMC.
我们最近报道，在培养的大鼠血管平滑肌细胞（VSMC）中，血管紧张素II（Ang II）诱导的丝裂原活化蛋白激酶（MAPK）激活主要是通过Gq偶联的Ang II 1型受体，由Ca2+依赖性激活一种蛋白酪氨酸激酶介导的。在本研究中，我们发现Ang II迅速诱导表皮生长因子（EGF）受体的酪氨酸磷酸化及其与Shc和Grb2的结合。这些反应被EGF受体激酶抑制剂AG1478抑制。Ang II诱导的EGF受体磷酸化可被Ca2+离子载体模拟，并被细胞内Ca2+螯合剂完全抑制。因此，AG1478消除了Ang II、Ca2+离子载体以及EGF在VSMC中诱导的MAPK激活，但不能消除佛波酯或血小板衍生生长因子-BB诱导的MAPK激活。此外，Ang II诱导EGF受体与具有催化活性的c-Src结合。该反应不受AG1478影响。这些数据表明，Ang II诱导EGF受体的Ca2+依赖性反式激活，该受体作为预激活的c-Src和下游衔接蛋白的支架，导致VSMC中的MAPK激活。
