Fan G H, Zhou T H, Zhang W B, Pei G
Shanghai Institute of Cell Biology, Chinese Academy of Sciences, PR China.
Eur J Pharmacol. 1998 Jan 12;341(2-3):317-22. doi: 10.1016/s0014-2999(97)01477-5.
The potential effect of inhibition of phospholipase C on the response of Gi-coupled receptors was investigated in neuroblastoma x glioma hybrid (NG108-15) cells. The phospholipase C specific inhibitor 1-[6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl]-1H -pyrrole-2,5-dione (U73122), which did not affect basal and forskolin-stimulated adenylyl cyclase activities, time- and dose-dependently blocked delta-opioid receptor-mediated inhibition of adenylyl cyclase activity, the EC50 (0.5 microM) of which was consistent with that for inhibition of bradykinin-dependent phospholipase C activation (EC50 = 1 microM). U73122 treatment also blocked functional responses of m4 muscarinic receptor and alpha2-adrenoceptor in NG108-15 cells and three opioid receptors (mu, delta and opioid receptor-like receptor (ORL1)) in human neuroblastoma SK-N-SH cells. 1-[6-((17Beta-3-Methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl]-2, 5-pyrrolidinedione (U73343), an inactive analog of U73122, did not show any effect, which suggests that the blockade by U73122 of Gi-coupled receptor-mediated signaling is probably mediated through inhibition of phospholipase C, although a possible direct modification of G proteins can not be excluded. Furthermore, treatment with U73122 but not U73343 blocked the GTP-induced inhibition of adenylyl cyclase, indicating blockade at the level of Gi proteins.
在神经母细胞瘤x胶质瘤杂交（NG108 - 15）细胞中研究了抑制磷脂酶C对Gi偶联受体反应的潜在影响。磷脂酶C特异性抑制剂1 - [6 - （（17β - 3 - 甲氧基雌甾 - 1,3,5（10） - 三烯 - 17 - 基）氨基）己基] - 1H - 吡咯 - 2,5 - 二酮（U73122）不影响基础和福斯可林刺激的腺苷酸环化酶活性，它呈时间和剂量依赖性地阻断δ - 阿片受体介导的腺苷酸环化酶活性抑制，其半数有效浓度（EC50）为0.5微摩尔，这与抑制缓激肽依赖性磷脂酶C激活的半数有效浓度（EC50 = 1微摩尔）一致。U73122处理还阻断了NG108 - 15细胞中m4毒蕈碱受体和α2 - 肾上腺素能受体以及人神经母细胞瘤SK - N - SH细胞中三种阿片受体（μ、δ和阿片受体样受体（ORL1））的功能反应。U73122的无活性类似物1 - [6 - （（17β - 3 - 甲氧基雌甾 - 1,3,5（10） - 三烯 - 17 - 基）氨基）己基] - 2,5 - 吡咯烷二酮（U73343）未显示任何作用，这表明U73122对Gi偶联受体介导的信号传导的阻断可能是通过抑制磷脂酶C介导的，尽管不能排除对G蛋白的可能直接修饰。此外，用U73122而非U73343处理可阻断GTP诱导的腺苷酸环化酶抑制，表明在Gi蛋白水平发生了阻断。
