Functional deactivation of the major neuronal nicotinic receptor caused by nicotine and a protein kinase C-dependent mechanism.
The effect of nicotine on the major human neuronal nicotinic receptor (alpha 4 beta 2 subtype) was studied in permanently transfected HEK 293 cells. Prolonged exposure to low concentrations of nicotine (1 microM) increased epibatidine binding but functionally deactivated the nicotinic receptor, abolishing Ca2+ influx in response to an acute nicotine challenge. Deactivation could also be caused by down-regulating protein kinase C (PKC) activity with 0.5 microM phorbol-12,13-dibutyrate or briefly incubating cells with the PKC inhibitor NPC-15437. Recovery from receptor deactivation caused by either nicotine treatment or PKC inhibition occurred slowly (4-6 hr). Reversal of nicotine-induced deactivation was accelerated by the addition of inhibitors of protein phosphatases 2A and 2B. These data suggest a hypothetical mechanism of nicotine-induced deactivation that involves dephosphorylation of nicotinic receptors at PKC phosphorylation sites.
Eilers
H
H
Department of Anesthesia, University of California San Francisco 94143-0542, USA.
Schaeffer
E
E
Bickler
P E
PE
Forsayeth
J R
JR
D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000378:metabolism / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D009474:Neurons / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure*; D009538:Nicotine / Q000494:pharmacology*; D018722:Nicotinic Agonists / Q000378:metabolism / Q000494:pharmacology*; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors; D011487:Protein Conformation; D011493:Protein Kinase C / Q000378:metabolism / Q000502:physiology*; D011725:Pyridines / Q000378:metabolism / Q000494:pharmacology; D011978:Receptors, Nicotinic / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*; D012680:Sensitivity and Specificity; D014162:Transfection; D015854:Up-Regulation / Q000187:drug effects
D019086:Bridged Bicyclo Compounds, Heterocyclic; D004791:Enzyme Inhibitors; D018722:Nicotinic Agonists; D011725:Pyridines; D011978:Receptors, Nicotinic; D009538:Nicotine; D011493:Protein Kinase C; D010744:Phosphoric Monoester Hydrolases; C082748:epibatidine; D002118:Calcium