Palaparti A, Ge C, Anand-Srivastava M B
Faculty of Medicine, University of Montreal, Montreal, Quebec, H3C 3J7, Canada.
Arch Biochem Biophys. 1999 May 1;365(1):113-22. doi: 10.1006/abbi.1999.1153.
In the present studies, we have investigated the effect of angiotensin II (AII) on guanine nucleotide regulatory protein (G protein) expression and functions in A10 smooth muscle cells. AII treatment of A10 cells enhanced the levels of inhibitory guanine nucleotide regulatory protein (Gi) as well as Gi mRNA and not of stimulatory guanine nucleotide regulatory protein (Gs) in a concentration-dependent manner as determined by immunoblot and Northern blot analysis, respectively. AII-evoked increased expression of Gialpha-2 and Gialpha-3 was inhibited by actinomycin D treatment (RNA synthesis inhibitor). The increased expression of Gialpha-2 and Gialpha-3 by AII was not reflected in functions, because the GTPgammaS-mediated inhibition of forskolin-stimulated adenylyl cyclase and the receptor-mediated inhibition of adenylyl cyclase by AII and C-ANP4-23 [des(Gln18, Ser19, Gln20, Leu21, Gly22) ANP4-23-NH2] were not augmented but attenuated in AII-treated A10 cells. The attenuation was prevented by staurosporine (a protein kinase C inhibitor) treatment. On the other hand, AII treatment did not affect the expression and functions of stimulatory guanine nucleotide regulatory protein (Gs), however, the stimulatory effects of 5'-O-(3-thiotriphosphate), isoproterenol, and N-ethylcarboxamide adenosine (NECA) on adenylyl cyclase activity were inhibited to various degrees by AII treatment. Staurosporine reversed the AII-evoked attenuation of isoproterenol- and NECA-stimulated enzyme activity. From these results, it can be suggested that AII, whose levels are increased in hypertension, may be one of the possible contributing factors responsible for exhibiting an enhanced expression of Gi protein in hypertension.
在本研究中，我们研究了血管紧张素II（AII）对A10平滑肌细胞中鸟嘌呤核苷酸调节蛋白（G蛋白）表达及功能的影响。通过免疫印迹和Northern印迹分析分别测定，用AII处理A10细胞后，抑制性鸟嘌呤核苷酸调节蛋白（Gi）及其mRNA水平呈浓度依赖性升高，而刺激性鸟嘌呤核苷酸调节蛋白（Gs）水平未升高。放线菌素D处理（RNA合成抑制剂）可抑制AII诱导的Gialpha - 2和Gialpha - 3表达增加。AII引起的Gialpha - 2和Gialpha - 3表达增加并未反映在功能上，因为在经AII处理的A10细胞中，GTPγS介导的对福斯可林刺激的腺苷酸环化酶的抑制作用以及AII和C - ANP4 - 23 [去（Gln18，Ser19，Gln20，Leu21，Gly22）ANP4 - 23 - NH2]对受体介导的腺苷酸环化酶的抑制作用并未增强，反而减弱。星形孢菌素（一种蛋白激酶C抑制剂）处理可防止这种减弱。另一方面，AII处理不影响刺激性鸟嘌呤核苷酸调节蛋白（Gs）的表达和功能，然而，AII处理可不同程度地抑制5'-O-（3 - 硫代三磷酸）、异丙肾上腺素和N - 乙基甲酰胺腺苷（NECA）对腺苷酸环化酶活性的刺激作用。星形孢菌素可逆转AII引起的异丙肾上腺素和NECA刺激的酶活性减弱。从这些结果可以推测，在高血压中水平升高的AII可能是导致高血压中Gi蛋白表达增强的可能因素之一。
