Brown A M, Birnbaumer L
Department of Physiology and Molecular Biophysics, Baylor College of Medicine, Houston, Texas 77030.
Am J Physiol. 1988 Mar;254(3 Pt 2):H401-10. doi: 10.1152/ajpheart.1988.254.3.H401.
Guanine nucleotide binding (G) proteins couple a variety of receptors to ionic channels. Until recently the pathway was thought to be indirect via cytoplasmic second messengers; now the heterotrimeric G proteins are known to act directly on K+ and Ca2+ channels. Here we summarize recent developments concerning this widespread mechanism which we call G protein gating of ion channels. A specific pertussis toxin-sensitive G protein called Gk, purified from human red blood cells, activates a unique K+ channel and Gk, or a similar G protein, couples this channel to muscarinic atrial receptors. The alpha-subunit (alpha k) at less than 10 pM mediates the effects, and alpha k also activates K+ channels directly in neurosecretory cells. The G protein stimulatory to adenylyl cyclase, Gs, gates directly through its alpha-subunit, specific Ca2+ channels in heart and skeletal muscle T tubules. Hence, one G protein can have two distinct effectors.
鸟嘌呤核苷酸结合（G）蛋白将多种受体与离子通道偶联起来。直到最近，人们还认为该途径是通过细胞质第二信使间接进行的；现在已知异源三聚体G蛋白可直接作用于钾离子通道和钙离子通道。在此，我们总结了关于这一广泛机制（我们称之为离子通道的G蛋白门控）的最新进展。一种从人红细胞中纯化出来的名为Gk的特定百日咳毒素敏感型G蛋白，可激活一种独特的钾离子通道，并且Gk或一种类似的G蛋白将该通道与毒蕈碱型心房受体偶联起来。浓度低于10皮摩尔的α亚基（αk）介导这些效应，并且αk还可直接激活神经分泌细胞中的钾离子通道。对腺苷酸环化酶有刺激作用的G蛋白Gs，通过其α亚基直接控制心脏和骨骼肌T小管中的特定钙离子通道。因此，一种G蛋白可以有两种不同的效应器。
