van Giersbergen P L, Leppik R
Marion Merrill Dow Research Institute, Strasbourg, France.
Naunyn Schmiedebergs Arch Pharmacol. 1995 Aug;352(2):166-72. doi: 10.1007/BF00176770.
In membranes prepared from CHO-m2 cells, inhibition of [3H]-N-methylscopolamine ([3H]NMS) binding by several muscarinic agonists resulted in competition curves with Hill slopes significantly different from unity. Addition of 5'-guanylylimidodiphosphate (Gpp(NH)p) led to an increase in the IC50 value of the agonists with significant steepening of the inhibition curves. The shift in potency induced by Gpp(NH)p differed among the agonists with a rank order of oxotremorine-M = carbachol > oxotremorine > McN-A-343 = pilocarpine. In CHO-m4 membranes, Gpp(NH)p was less efficacious than in CHO-m2 membranes whereas no effect of the guanine nucleotide was found in membranes prepared from CHO-m1, -m3, and -m5 cells. No major differences in the effect of Gpp(NH)p among agonists were found in CHO-m4 cells. Atropine binding was not affected by the guanine nucleotide. Together, these results indicate that coupling of G-proteins to muscarinic receptors linked to inhibition of cyclic adenosine monophosphate (cAMP) (m2 and m4) but not of those linked to phosphoinositol turnover (m1, m3 and m5) can be perturbed by Gpp(NH)p. The differential effects observed with Gpp(NH)p between agonist binding to m2 and m4 receptors appear to be receptor-specific and may reflect differences in the G proteins activated by these receptors in CHO cells.
在从CHO - m2细胞制备的膜中，几种毒蕈碱激动剂对[3H] - N - 甲基东莨菪碱（[3H]NMS）结合的抑制作用导致竞争曲线的希尔斜率显著不同于1。添加5'-鸟苷酰亚胺二磷酸（Gpp(NH)p）导致激动剂的IC50值增加，抑制曲线明显变陡。Gpp(NH)p诱导的效力变化在激动剂之间有所不同，顺序为氧化震颤素 - M = 卡巴胆碱 > 氧化震颤素 > McN - A - 343 = 毛果芸香碱。在CHO - m4膜中，Gpp(NH)p的效力低于在CHO - m2膜中的效力，而在从CHO - m1、-m3和 - m5细胞制备的膜中未发现鸟嘌呤核苷酸的作用。在CHO - m4细胞中，未发现Gpp(NH)p对激动剂的作用有重大差异。阿托品结合不受鸟嘌呤核苷酸的影响。总之，这些结果表明，G蛋白与与环磷酸腺苷（cAMP）抑制相关的毒蕈碱受体（m2和m4）的偶联，而不是与磷酸肌醇代谢相关的毒蕈碱受体（m1、m3和m5）的偶联，可被Gpp(NH)p干扰。观察到的Gpp(NH)p对激动剂与m2和m4受体结合的不同作用似乎是受体特异性的，可能反映了CHO细胞中这些受体激活的G蛋白的差异。
