title: Chronic nicotine modifies skeletal muscle Na,K-ATPase activity through its interaction with the nicotinic acetylcholine receptor and phospholemman.
abstract: Our previous finding that the muscle nicotinic acetylcholine receptor (nAChR) and the Na,K-ATPase interact as a regulatory complex to modulate Na,K-ATPase activity suggested that chronic, circulating nicotine may alter this interaction, with long-term changes in the membrane potential. To test this hypothesis, we chronically exposed rats to nicotine delivered orally for 21-31 days. Chronic nicotine produced a steady membrane depolarization of ∼3 mV in the diaphragm muscle, which resulted from a net change in electrogenic transport by the Na,K-ATPase α2 and α1 isoforms. Electrogenic transport by the α2 isoform increased (+1.8 mV) while the activity of the α1 isoform decreased (-4.4 mV). Protein expression of Na,K-ATPase α1 or α2 isoforms and the nAChR did not change; however, the content of α2 subunit in the plasma membrane decreased by 25%, indicating that its stimulated electrogenic transport is due to an increase in specific activity. The physical association between the nAChR, the Na,K-ATPase α1 or α2 subunits, and the regulatory subunit of the Na,K-ATPase, phospholemman (PLM), measured by co-immuno precipitation, was stable and unchanged. Chronic nicotine treatment activated PKCα/β2 and PKCδ and was accompanied by parallel increases in PLM phosphorylation at Ser(63) and Ser(68). Collectively, these results demonstrate that nicotine at chronic doses, acting through the nAChR-Na,K-ATPase complex, is able to modulate Na,K-ATPase activity in an isoform-specific manner and that the regulatory range includes both stimulation and inhibition of enzyme activity. Cholinergic modulation of Na,K-ATPase activity is achieved, in part, through activation of PKC and phosphorylation of PLM.
authors.affiliation: Department of Molecular Medicine and Surgery, Integrative Physiology, Karolinska Institutet, Stockholm, Sweden. Alexander.Chibalin@ki.se
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Chibalin
authors.forename: Judith A
authors.initials: JA
authors.lastname: Heiny
authors.forename: Boubacar
authors.initials: B
authors.lastname: Benziane
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Prokofiev
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Vasiliev
authors.forename: Violetta V
authors.initials: VV
authors.lastname: Kravtsova
authors.forename: Igor I
authors.initials: II
authors.lastname: Krivoi
mesh_terms: D000818:Animals; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008565:Membrane Proteins / Q000378:metabolism*; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D009538:Nicotine / Q000493:pharmacokinetics*; D018722:Nicotinic Agonists / Q000494:pharmacology*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects / Q000235:genetics; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011978:Receptors, Nicotinic / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000096:biosynthesis*
chemical_list: D008565:Membrane Proteins; D009124:Muscle Proteins; D018722:Nicotinic Agonists; D010750:Phosphoproteins; D011978:Receptors, Nicotinic; C069141:phospholemman; D009538:Nicotine; D011493:Protein Kinase C; C499075:Atp1a1 protein, rat; C498532:Atp1a2 protein, rat; D000254:Sodium-Potassium-Exchanging ATPase