Qin Yingjie, Yasuda Noritaka, Akazawa Hiroshi, Ito Kaoru, Kudo Yoko, Liao Chien-Hui, Yamamoto Rie, Miura Shin-Ichiro, Saku Keijiro, Komuro Issei
Department of Cardiovascular Science and Medicine, Chiba University Graduate School of Medicine, Chuo-ku, Chiba, Japan.
Hypertens Res. 2009 Oct;32(10):875-83. doi: 10.1038/hr.2009.117. Epub 2009 Aug 7.
Type 1 angiotensin II (AT(1)) receptor has a critical role in the development of load-induced cardiac hypertrophy. Recently, we showed that mechanical stretching of cells activates the AT(1) receptor without the involvement of angiotensin II (AngII) and that this AngII-independent activation is inhibited by the inverse agonistic activity of the AT(1) receptor blocker (ARB), candesartan. Although the inverse agonist activity of ARBs has been studied in terms of their action on constitutively active AT(1) receptors, the structure-function relationship of the inverse agonism they exert against stretch-induced AT(1) receptor activation has not been fully elucidated. Assays evaluating c-fos gene expression and phosphorylated extracellular signal-regulated protein kinases (ERKs) have shown that olmesartan has strong inverse agonist activities against the constitutively active AT(1) receptor and the stretch-induced activation of AT(1) receptor, respectively. Ternary drug-receptor interactions, which occur between the hydroxyl group of olmesartan and Tyr(113) and between the carboxyl group of olmesartan and Lys(199) and His(256), were essential for the potent inverse agonist action olmesartan exerts against stretch-induced ERK activation and the constitutive activity of the AT(1)-N111G mutant receptor. Furthermore, the inverse agonist activity olmesartan exerts against stretch-induced ERK activation requires an additional drug-receptor interaction involving the tetrazole group of olmesartan and Gln(257) of the AT(1) receptor. These results suggest that multivalent interactions between an inverse agonist and the AT(1) receptor are required to stabilize the receptor in an inactive conformation in response to the distinct processes that lead to an AngII-independent activation of the AT(1) receptor.
1型血管紧张素II（AT(1)）受体在负荷诱导的心脏肥大发展过程中起关键作用。最近，我们发现细胞的机械拉伸可激活AT(1)受体，且不涉及血管紧张素II（AngII），并且这种不依赖AngII的激活可被AT(1)受体阻滞剂（ARB）坎地沙坦的反向激动活性所抑制。尽管已就ARB的反向激动活性对组成型活性AT(1)受体的作用进行了研究，但它们对拉伸诱导的AT(1)受体激活所发挥的反向激动作用的结构-功能关系尚未完全阐明。评估c-fos基因表达和磷酸化细胞外信号调节蛋白激酶（ERK）的实验表明，奥美沙坦分别对组成型活性AT(1)受体和拉伸诱导的AT(1)受体激活具有强大的反向激动活性。奥美沙坦的羟基与Tyr(113)之间以及奥美沙坦的羧基与Lys(199)和His(256)之间发生的三元药物-受体相互作用，对于奥美沙坦对拉伸诱导的ERK激活和AT(1)-N111G突变受体的组成型活性所发挥的强效反向激动作用至关重要。此外，奥美沙坦对拉伸诱导的ERK激活所发挥的反向激动活性需要另一种药物-受体相互作用，该相互作用涉及奥美沙坦的四氮唑基团与AT(1)受体的Gln(257)。这些结果表明，反向激动剂与AT(1)受体之间的多价相互作用是必需的，以便在导致AT(1)受体不依赖AngII激活的不同过程中，将受体稳定在无活性构象。
