Kurachi Y, Nakajima T, Sugimoto T
Am J Physiol. 1986 Sep;251(3 Pt 2):H681-4. doi: 10.1152/ajpheart.1986.251.3.H681.
The activation mechanisms of K+ channels by muscarinic acetylcholine (m-ACh) receptors were examined in isolated atrial cells by use of patch-recording technique. In "cell-attached" patch recordings, ACh, present in the pipette, activated an inwardly rectifying K+ channel. In "inside-out" patches, activation of the K+ channel by ACh diminished with time following excision of the patch, but it resumed when GTP was present in the solution bathing the intracellular side of the membrane. The A protomer of pertussis toxin, together with NAD, inhibited the channel activation in the presence of GTP. Since pertussis toxin specifically ADP-ribosylates GTP-binding proteins Ni and No, which can interact with m-ACh receptors, and inhibits their functions, it was concluded that m-ACh receptors communicate with the K+ channel via GTP-binding proteins, probably Ni and/or No, in atrial cell membrane.
利用膜片钳记录技术，在分离的心房细胞中研究了毒蕈碱型乙酰胆碱（m-ACh）受体对钾通道的激活机制。在“细胞贴附式”膜片钳记录中，移液管中的乙酰胆碱激活了内向整流钾通道。在“外翻式”膜片中，膜片切除后，乙酰胆碱对钾通道的激活随时间减弱，但当膜片细胞内侧浸泡液中存在GTP时，激活作用恢复。百日咳毒素的A亚基与NAD一起，在有GTP存在时抑制通道激活。由于百日咳毒素特异性地使可与m-ACh受体相互作用的GTP结合蛋白Ni和No发生ADP核糖基化，并抑制其功能，因此得出结论：在心房细胞膜中，m-ACh受体通过GTP结合蛋白，可能是Ni和/或No与钾通道进行通讯。
