title: The nicotinic acetylcholine receptor and the Na,K-ATPase alpha2 isoform interact to regulate membrane electrogenesis in skeletal muscle.
abstract: The nicotinic acetylcholine receptor (nAChR) and the Na,K-ATPase functionally interact in skeletal muscle (Krivoi, I. I., Drabkina, T. M., Kravtsova, V. V., Vasiliev, A. N., Eaton, M. J., Skatchkov, S. N., and Mandel, F. (2006) Pflugers Arch. 452, 756-765; Krivoi, I., Vasiliev, A., Kravtsova, V., Dobretsov, M., and Mandel, F. (2003) Ann. N.Y. Acad. Sci. 986, 639-641). In this interaction, the specific binding of nanomolar concentrations of nicotinic agonists to the nAChR stimulates electrogenic transport by the Na,K-ATPase alpha2 isozyme, causing membrane hyperpolarization. This study examines the molecular nature and membrane localization of this interaction. Stimulation of Na,K-ATPase activity by the nAChR does not require ion flow through open nAChRs. It can be induced by nAChR desensitization alone, in the absence of nicotinic agonist, and saturates when the nAChR is fully desensitized. It is enhanced by noncompetitive blockers of the nAChR (proadifen, QX-222), which promote non-conducting or desensitized states; and retarded by tetracaine, which stabilizes the resting nAChR conformation. The interaction operates at the neuromuscular junction as well as on extrajunctional sarcolemma. The Na,K-ATPase alpha2 isozyme is enriched at the postsynaptic neuromuscular junction and co-localizes with nAChRs. The nAChR and Na,K-ATPase alpha subunits specifically coimmunoprecipitate with each other, phospholemman, and caveolin-3. In a purified membrane preparation from Torpedo californica enriched in nAChRs and the Na,K-ATPase, a ouabain-induced conformational change of the Na,K-ATPase enhances a conformational transition of the nAChR to a desensitized state. These results suggest a mechanism by which the nAChR in a desensitized state with high apparent affinity for agonist interacts with the Na,K-ATPase to stimulate active transport. The interaction utilizes a membrane-delimited complex involving protein-protein interactions, either directly or through additional protein partners. This interaction is expected to enhance neuromuscular transmission and muscle excitation.
authors.affiliation: Department of General Physiology, St. Petersburg State University, St. Petersburg 199034, Russia.
authors.forename: Judith A
authors.initials: JA
authors.lastname: Heiny
authors.forename: Violetta V
authors.initials: VV
authors.lastname: Kravtsova
authors.forename: Frederic
authors.initials: F
authors.lastname: Mandel
authors.forename: Tatiana L
authors.initials: TL
authors.lastname: Radzyukevich
authors.forename: Boubacar
authors.initials: B
authors.lastname: Benziane
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Prokofiev
authors.forename: Steen E
authors.initials: SE
authors.lastname: Pedersen
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Chibalin
authors.forename: Igor I
authors.initials: II
authors.lastname: Krivoi
mesh_terms: D000818:Animals; D051244:Caveolin 3 / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008012:Lidocaine / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism; D009469:Neuromuscular Junction / Q000378:metabolism*; D018722:Nicotinic Agonists / Q000494:pharmacology; D018733:Nicotinic Antagonists / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism; D011335:Proadifen / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D011978:Receptors, Nicotinic / Q000378:metabolism*; D012508:Sarcolemma / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D014101:Torpedo
chemical_list: C495549:Cav3 protein, rat; D051244:Caveolin 3; D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D018722:Nicotinic Agonists; D018733:Nicotinic Antagonists; D010750:Phosphoproteins; D011978:Receptors, Nicotinic; C069141:phospholemman; C006072:QX-222; D008012:Lidocaine; D011335:Proadifen; C498532:Atp1a2 protein, rat; D000254:Sodium-Potassium-Exchanging ATPase