Dual effects of muscarinic M2 acetylcholine receptors on the synthesis of cyclic AMP in CHO cells:: dependence on time, receptor density and receptor agonists
Dual effects of muscarinic M2 acetylcholine receptors on the synthesis of cyclic AMP in CHO cells:: dependence on time, receptor density and receptor agonists
复制标题
DOI：
10.1038/sj.bjp.0703931
复制
发表时间：
2001-03-01
影响因子：
7.3
通讯作者：
Tucek, S
中科院分区：
文献类型：
--
作者：
Michal, P;Lysíková, M;Tucek, S
1 毒蕈碱 M-2 受体通常通过 G(i) 蛋白抑制环 AMP 的产生，但在高激动剂浓度下其作用中会出现刺激成分，据信这是基于 G(s) 蛋白的激活。我们研究了确定稳定表达毒蕈碱 M-2 受体的 CHO 细胞中刺激成分的出现和程度的条件。2 与卡巴胆碱、氧化震颤素-M、乙酰胆碱、槟榔碱和槟榔碱炔丙酯孵育 10 分钟后获得双相浓度-反应曲线（先下降，然后返回对照值），但氧化震颤素、甲基呋美特、呋美酯缺少上升相。和戊硫基-TZTP，缩短孵育时间有利于刺激成分的出现。卡巴胆碱 (1 mM) 和氧化震颤素-M (1 mM) 在 2 分钟孵育期间对环 AMP 合成产生净刺激（高于对照的 100%）。用氧苯溴铵降低受体密度后，刺激成分消失。3 所有激动剂均刺激用百日咳毒素预处理的细胞中环 AMP 的合成。4 激动剂对环 AMP 合成的刺激成分的影响的大多数差异可以通过其功效和诱导的受体内化的差异来解释。5 我们认为，毒蕈碱 M-2 作用的 G(s) 介导的刺激成分仅当激活受体的密度足够高以使 G(i) 蛋白饱和并且与受体对 G(s) 蛋白的低亲和力成比例时，环 AMP 合成上的受体才会发生。它往往会被受体内化所消除。
1 Muscarinic M-2 receptors normally inhibit the production of cyclic AMP via G(i) proteins, but a stimulatory component occurs in their effect at high agonist concentrations, believed to be based on the activation of G(s) proteins. We investigated the conditions which determine the occurrence and extent of the stimulatory component in CHO cells stably expressing muscarinic M-2 receptors.2 Biphasic concentration-response curves (decline followed by return towards control values) were obtained after 10 min incubation with carbachol, oxotremorine-M, acetylcholine, arecoline and arecaidine propargyl ester, but the upward phase was missing with oxotremorine, methylfurmethide, furmethide and pentylthio-TZTP, Shortening the incubation favoured the occurrence of the stimulatory component. Carbachol (1 mM) and oxotremorine-M (1 mM) brought about net stimulation (above 100% of control) of cyclic AMP synthesis during 2 min incubations. The stimulatory components disappeared after the density of receptors had been lowered with oxyphenonium mustard.3 All agonists stimulated the synthesis of cyclic AMP in cells pretreated with pertussis toxin.4 Most differences between agonists regarding the stimulatory component of their effect on cyclic AMP synthesis could be explained by differences in their efficacy and the induced receptor internalization.5 We propose that the G(s)-mediated stimulatory component of the effect of muscarinic M-2 receptors on cyclic AMP synthesis only occurs if the density of activated receptors is high enough to saturate the G(i) proteins and proportionate to the receptors' low affinity for the G(s) proteins. It tends to be abolished by receptor internalization.