The interaction of acetylcholine receptors in porcine atrial membranes with three kinds of G proteins

• Published in: Japanese circulation journal Vol. 54; no. 9; pp. 1176 - 1184
• Main Authors: HAGA, T, IKEGATA, T, HAGA, K
• Format: Journal Article
• Language: English
• Published: Kyoto Japanese Circulation Society 01.09.1990
• Subjects: Animals; Biological and medical sciences; Carbachol - metabolism; Ethylmaleimide - pharmacology; Fundamental and applied biological sciences. Psychology; GTP-Binding Proteins - metabolism; Heart; Heart Atria - drug effects; Heart Atria - metabolism; Hot Temperature; Membranes - drug effects; Membranes - metabolism; Myocardium - metabolism; Receptors, Muscarinic - metabolism; Swine; Vertebrates: cardiovascular system; Atrium; Exploration; Receiver; Experimental study; Pig; Binding protein; Vertebrata; Mammalia; Animal; Membrane; Acetylcholine; Muscarinic receptor; Artiodactyla; Ungulata
• ISSN: 0047-1828; 1347-4839
• DOI: 10.1253/jcj.54.1176

We developed a simple procedure to detect the interaction of muscarinic receptors in atrial membranes with exogenous GTP-binding proteins (G proteins). The procedure consists of mixing atrial membranes with G proteins in the presence of sodium cholate, diluting the mixture with a salt buffer and then measuring the ligand binding activity. The displacement by carbachol of [3H] QNB binding to muscarinic receptors in the atrial membranes was not affected by guanine nucleotides when the membranes had been treated at 60 degrees C for 30 min or with N-ethylmeleimide (NEM) and became affected by them after mixing the heat- or NEM-treated membranes with G proteins. The displacement curves in the presence of GTP were essentially the same irrespective of the presence or absence of G proteins. Those in the absence of GTP shifted to a lower concentration of carbachol with addition of a higher concentration of G proteins, indicating an increase in GTP-sensitive high affinity agonist binding sites. The highest affinity for carbachol was detected with membranes treated with NEM and then mixed with G proteins. The GTP-sensitive high affinity agonist binding could be detected with any one of three kinds of G proteins (Gi, Go, Gn) which were purified from porcine cerebrum, indicating that the muscarinic receptor m2 subtype may interact with and possibly activate these three kinds of G proteins.