On the functional interaction between nicotinic acetylcholine receptor and Na+,K+-ATPase.
Previous studies have shown that nanomolar acetylcholine (ACh) produces a 2 to 4-mV hyperpolarization of skeletal muscle fibers putatively due to Na(+),K(+)-ATPase activation. The present study elucidates the involvement of the nicotinic ACh receptor (nAChR) and of Na(+),K(+)-ATPase isoform(s) in ACh-induced hyperpolarization of rat diaphragm muscle fibers. A variety of ligands of specific binding sites of nAChR and Na(+),K(+)-ATPase were used. Dose-response curves for ouabain, a specific Na(+),K(+)-ATPase inhibitor, were obtained to ascertain which Na(+),K(+)-ATPase isoform(s) is involved. The ACh dose-response relationship for the hyperpolarization was also determined. The functional relationship between these two proteins was also studied in a less complex system, a membrane preparation from Torpedo electric organ. The possibility of a direct ACh effect on Na(+),K(+)-ATPase was studied in purified lamb kidney Na(+),K(+)-ATPase and in rat red blood cells, systems where no nAChR is present. The results indicate that binding of nAChR agonists to their specific sites results in modulation of ouabain-sensitive (most probably alpha2) isoform of Na(+),K(+)-ATPase, leading to muscle membrane hyperpolarization. In the Torpedo preparation, ouabain modulates dansyl-C6-choline binding to nAChR, and vice versa. These results provide the first evidence of a functional interaction between nAChR and Na(+),K(+)-ATPase. Possible interaction mechanisms are discussed.
Krivoi
Igor I
II
Department of General Physiology, St. Petersburg State University, 7/9 University emb., St. Petersburg 199034, Russia. IgorKrivoi@IK4251.spb.edu
Drabkina
Tatiana M
TM
Kravtsova
Violetta V
VV
Vasiliev
Alexander N
AN
Eaton
Misty J
MJ
Skatchkov
Serguei N
SN
Mandel
Frederic
F
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D003619:Dansyl Compounds / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000201:enzymology; D066298:In Vitro Techniques; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000502:physiology; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D009538:Nicotine / Q000494:pharmacology; D018722:Nicotinic Agonists / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000502:physiology*; D012756:Sheep; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000502:physiology*; D013050:Spectrometry, Fluorescence; D014101:Torpedo
D003619:Dansyl Compounds; D004791:Enzyme Inhibitors; D018722:Nicotinic Agonists; D000644:Quaternary Ammonium Compounds; D011978:Receptors, Nicotinic; D010042:Ouabain; C027933:(1-(5-dimethylaminonaphthalene)sulfonamido)-n-hexanoic acid-beta-N-trimethylammonium ethyl ester; D009538:Nicotine; C498532:Atp1a2 protein, rat; D000254:Sodium-Potassium-Exchanging ATPase; D000109:Acetylcholine