Lechleiter J, Hellmiss R, Duerson K, Ennulat D, David N, Clapham D, Peralta E
Department of Pharmacology, Mayo Foundation, Rochester, MN 55905.
EMBO J. 1990 Dec;9(13):4381-90. doi: 10.1002/j.1460-2075.1990.tb07888.x.
Relatively little is understood concerning the mechanisms by which subtypes of receptors, G proteins and effector enzymes interact to transduce specific signals. Through expression of normal, hybrid and deletion mutant receptors in Xenopus oocytes, we determined the G protein coupling characteristics of the functionally distinct m2 and m3 muscarinic acetylcholine receptor (mAChR) subtypes and identified the critical receptor sequences responsible for G protein specificity. Activation of a pertussis toxin insensitive G protein pathway, leading to a rapid and transient release of intracellular Ca2+ characteristic of the m3 receptor, could be specified by the transfer of as few as nine amino acids from the m3 to the m2 receptor. In a reciprocal manner, transfer of no more than 21 residues from the m2 to the m3 receptor was sufficient to specify activation of a pertussis toxin sensitive G protein coupled to a slow and oscillatory Ca2+ release pathway typical of the m2 subtype. Notably, these critical residues occur within the same region of the third cytoplasmic domain of functionally distinct mAChR subtypes.
关于受体亚型、G蛋白和效应酶相互作用以转导特定信号的机制，人们了解得相对较少。通过在非洲爪蟾卵母细胞中表达正常、杂交和缺失突变受体，我们确定了功能不同的毒蕈碱型乙酰胆碱受体（mAChR）m2和m3亚型的G蛋白偶联特性，并确定了负责G蛋白特异性的关键受体序列。激活百日咳毒素不敏感的G蛋白途径，导致m3受体特有的细胞内Ca2+快速短暂释放，这可以通过将少至9个氨基酸从m3受体转移到m2受体来实现。反之，从m2受体转移不超过21个残基就足以激活与m2亚型典型的缓慢振荡性Ca2+释放途径偶联的百日咳毒素敏感G蛋白。值得注意的是，这些关键残基出现在功能不同的mAChR亚型的第三个胞质结构域的同一区域内。
