title: Direct G protein gating of ion channels.
abstract: 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.
mesh_terms: D037361:Adenylate Cyclase Toxin; D000818:Animals; D002118:Calcium / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000502:physiology*; D006325:Heart Atria; D006801:Humans; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D009132:Muscles / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D037342:Pertussis Toxin; D011188:Potassium / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000378:metabolism; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D037361:Adenylate Cyclase Toxin; D007473:Ion Channels; D011976:Receptors, Muscarinic; D010566:Virulence Factors, Bordetella; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D011188:Potassium; D002118:Calcium