title: G protein regulation of cardiac muscarinic potassium channel.
abstract: Several ion channels can be regulated by G proteins in a "membrane-delimited" manner. The cardiac muscarinic K+ (KACh) channel, which is responsible for the acetylcholine (ACh) or adenosine-induced deceleration of heart beat and atrioventricular conduction, is the prototype of this type of receptor-dependent regulation of ion channels. Because similar transduction mechanisms are utilized by various membrane receptors, such as somatostatin, 5-hydroxytryptamine-1, alpha 2-adrenergic, mu-and delta-opioid, D2-dopamine, and gamma-aminobutyric acid B receptors, in neuronal, hormone-secreting, renal, or smooth muscle cells, the G protein (GK)-KACh channel system illustrates the principles underlying one of the most important cell signaling mechanisms (B. Hille. Neuron 9: 187-195, 1992). It seems that both alpha- and beta gamma-subunits of GK may be involved in the regulation of the KACh channel of mammalian atrial muscle. A general consensus of opinion has emerged, after some years of controversy, to support the notion that physiological activation of the channel by GK is the responsibility of the beta gamma-subunits. Recent evidence suggests that the KACh channel interacts with the alpha-subunit in the terminating process of activation.
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D003001:Cloning, Molecular; D004789:Enzyme Activation; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000502:physiology*; D006801:Humans; D009116:Muscarine / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D015221:Potassium Channels / Q000235:genetics / Q000502:physiology*
chemical_list: D015221:Potassium Channels; D009116:Muscarine; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins