Olivares-Reyes J Alberto, Shah Bukhtiar H, Hernández-Aranda Judith, García-Caballero Agustín, Farshori M Parvaiz, García-Sáinz J Adolfo, Catt Kevin J
Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, A. P. 14-740 México, 07000 D. F., México.
Mol Pharmacol. 2005 Aug;68(2):356-64. doi: 10.1124/mol.104.010637. Epub 2005 May 19.
In rat hepatic C9 cells, angiotensin II (Ang II)-induced activation of angiotensin type 1 (AT(1)) receptors (AT(1)-Rs) stimulates extracellular signal-regulated kinase (ERK) 1/2 phosphorylation via transactivation of the endogenous epidermal growth factor (EGF) receptor (EGF-R) by a protein kinase C (PKC) delta/Src/Pyk2-dependent pathway. This leads to phosphorylation of the EGF-R as well as its subsequent internalization. On the other hand, EGF-induced activation of the EGF-R in C9 cells was found to cause phosphorylation of the AT(1)-R. This was prevented by selective inhibition of the intrinsic tyrosine kinase activity of the EGF-R by AG1478 [4-(3'-chloroanilino)-6,7-dimethoxy-quinazoline] and was reduced by inhibition of PKC and phosphoinositide 3-kinase. EGF-induced AT(1)-R phosphorylation was associated with a decrease in membrane-associated AT(1)-Rs and a reduced inositol phosphate response to Ang II. Agonist activation of endogenous AT(1)-Rs and EGF-Rs induced the formation of a multireceptor complex containing both the AT(1)-R and the transactivated EGF-R. The dependence of these responses on caveolin was indicated by the finding that cholesterol depletion of C9 cells abolished Ang II-induced inositol phosphate production, activation of Akt/PKB and ERK1/2, and AT(1)-R internalization. Confocal microscopy demonstrated that caveolin-1 was endogenously phosphorylated and was distributed on the plasma membrane in patches that undergo redistribution during Ang II stimulation. Agonist-induced phosphorylation and association of caveolin 1 with the AT(1)-R was observed, consistent with a scaffolding role of caveolin during transactivation of the EGF-R by Ang II. The EGF-induced AT(1)-R/caveolin association was abolished by AG1478, suggesting that activation of the EGF-R promotes the association of caveolin and the AT(1)-R.
在大鼠肝脏C9细胞中，血管紧张素II（Ang II）诱导的血管紧张素1型（AT(1)）受体（AT(1)-Rs）激活通过蛋白激酶C（PKC）δ/ Src / Pyk2依赖性途径使内源性表皮生长因子（EGF）受体（EGF-R）反式激活，从而刺激细胞外信号调节激酶（ERK）1/2磷酸化。这导致EGF-R磷酸化及其随后的内化。另一方面，发现EGF诱导的C9细胞中EGF-R激活会导致AT(1)-R磷酸化。AG1478 [4-(3'-氯苯胺基)-6,7-二甲氧基喹唑啉]对EGF-R内在酪氨酸激酶活性的选择性抑制可阻止这种情况，并且通过抑制PKC和磷酸肌醇3-激酶可使其减少。EGF诱导的AT(1)-R磷酸化与膜相关AT(1)-Rs的减少以及对Ang II的肌醇磷酸反应降低有关。内源性AT(1)-Rs和EGF-Rs的激动剂激活诱导形成包含AT(1)-R和反式激活的EGF-R的多受体复合物。C9细胞的胆固醇耗竭消除了Ang II诱导的肌醇磷酸产生、Akt / PKB和ERK1/2激活以及AT(1)-R内化，这一发现表明这些反应对小窝蛋白的依赖性。共聚焦显微镜显示小窝蛋白-1内源性磷酸化，并分布在质膜上的斑块中，在Ang II刺激期间会发生重新分布。观察到激动剂诱导的小窝蛋白1磷酸化以及与AT(1)-R的结合，这与小窝蛋白在Ang II对EGF-R反式激活过程中的支架作用一致。AG1478消除了EGF诱导的AT(1)-R /小窝蛋白结合，表明EGF-R的激活促进了小窝蛋白与AT(1)-R的结合。
