Wei Huijun, Ahn Seungkirl, Shenoy Sudha K, Karnik Sadashiva S, Hunyady László, Luttrell Louis M, Lefkowitz Robert J
Howard Hughes Medical Institute and Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA.
Proc Natl Acad Sci U S A. 2003 Sep 16;100(19):10782-7. doi: 10.1073/pnas.1834556100. Epub 2003 Aug 29.
Stimulation of a mutant angiotensin type 1A receptor (DRY/AAY) with angiotensin II (Ang II) or of a wild-type receptor with an Ang II analog ([sarcosine1,Ile4,Ile8]Ang II) fails to activate classical heterotrimeric G protein signaling but does lead to recruitment of beta-arrestin 2-GFP and activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) (maximum stimulation approximately 50% of wild type). This G protein-independent activation of mitogen-activated protein kinase is abolished by depletion of cellular beta-arrestin 2 but is unaffected by the PKC inhibitor Ro-31-8425. In parallel, stimulation of the wild-type angiotensin type 1A receptor with Ang II robustly stimulates ERK1/2 activation with approximately 60% of the response blocked by the PKC inhibitor (G protein dependent) and the rest of the response blocked by depletion of cellular beta-arrestin 2 by small interfering RNA (beta-arrestin dependent). These findings imply the existence of independent G protein- and beta-arrestin 2-mediated pathways leading to ERK1/2 activation and the existence of distinct "active" conformations of a seven-membrane-spanning receptor coupled to each.
用血管紧张素 II（Ang II）刺激突变型 1A 型血管紧张素受体（DRY/AAY），或用 Ang II 类似物（[肌氨酸 1，异亮氨酸 4，异亮氨酸 8]Ang II）刺激野生型受体，均无法激活经典的异源三聚体 G 蛋白信号传导，但确实会导致β-抑制蛋白 2-GFP 的募集以及细胞外信号调节激酶 1 和 2（ERK1/2）的激活（最大刺激约为野生型的 50%）。细胞内β-抑制蛋白 2 的耗竭可消除这种与 G 蛋白无关的丝裂原活化蛋白激酶激活，但不受蛋白激酶 C 抑制剂 Ro-31-8425 的影响。同时，用 Ang II 刺激野生型 1A 型血管紧张素受体可强烈刺激 ERK1/2 激活，其中约 60%的反应被蛋白激酶 C 抑制剂阻断（依赖 G 蛋白），其余反应被小干扰 RNA 使细胞内β-抑制蛋白 2 耗竭所阻断（依赖β-抑制蛋白）。这些发现表明存在独立的、由 G 蛋白和β-抑制蛋白 2 介导的导致 ERK1/2 激活的信号通路，以及与之偶联的七跨膜受体的不同“活性”构象。
