Up-regulation of human alpha7 nicotinic receptors by chronic treatment with activator and antagonist ligands.
This study examined the binding and functional properties of human alpha7 neuronal nicotinic acetylcholine receptors stably expressed in human embryonic kidney (HEK) 293 cells following chronic treatment with nicotinic receptor ligands. Treatment of cells with (-)-nicotine (100 microM) for 120 h increased the Bmax values of [125I]alpha-bungarotoxin binding 2.5-fold over untreated cells. This effect was concentration-dependent (EC50) = 970 microM) and a 6-fold upregulation was observed with the maximal concentration of (-)-nicotine tested. Also, treatment of cells with ligands of varying intrinsic activities including (+/-)-epibatidine, (2,4)-dimethoxybenzylidene anabaseine (GTS-21) and 1,1-dimethyl-4-phenyl piperazinium iodide (DMPP) also upregulated [125I]alpha-bungarotoxin binding. A concentration-dependent upregulation of binding sites was also observed following treatment with the alpha7 nicotinic receptor antagonist, methyllycaconitine (EC50 = 92 microM) with a maximal upregulation of about 7-fold. Functionally, the peak amplitude of the whole-cell currents recorded by fast application of (-)-nicotine after chronic treatment of cells with concentrations of (-)-nicotine (1000 microM) or methyllycaconitine (10 microM) that elicited similar increases in binding levels (3.5-fold) resulted in increases of 2-fold (505 +/- 21 pA) and 6-fold (1820 +/- 137 pA) respectively in whole cell current amplitude compared to untreated cells (267 +/- 24 pA). These studies clearly demonstrate that long-term exposure to both activator and antagonist ligands can increase the density of alpha7 nicotinic receptors and can differentially enhance nicotinic receptor function.
Molinari
E J
EJ
Neurological and Urological Diseases Research, Pharmaceutical Products Division, Abbott Laboratories, Abbott Park, IL 60064-3500, USA.
Delbono
O
O
Messi
M L
ML
Renganathan
M
M
Arneric
S P
SP
Sullivan
J P
JP
Gopalakrishnan
M
M
D000157:Aconitine / Q000031:analogs & derivatives / Q000494:pharmacology; D001597:Benzylidene Compounds / Q000494:pharmacology; D001665:Binding Sites; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002038:Bungarotoxins / Q000378:metabolism / Q000494:pharmacology; D004246:Dimethylphenylpiperazinium Iodide / Q000494:pharmacology; D006801:Humans; D007306:Insecticides / Q000494:pharmacology; D007457:Iodine Radioisotopes; D007668:Kidney / Q000187:drug effects / Q000648:ultrastructure; D007700:Kinetics; D008024:Ligands; D009538:Nicotine / Q000494:pharmacology; D018722:Nicotinic Agonists / Q000494:pharmacology*; D018733:Nicotinic Antagonists / Q000378:metabolism / Q000494:pharmacology*; D011725:Pyridines / Q000494:pharmacology; D011978:Receptors, Nicotinic / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D014162:Transfection; D015854:Up-Regulation / Q000187:drug effects; D064569:alpha7 Nicotinic Acetylcholine Receptor
D001597:Benzylidene Compounds; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002038:Bungarotoxins; C579167:Chrna7 protein, human; D007306:Insecticides; D007457:Iodine Radioisotopes; D008024:Ligands; D018722:Nicotinic Agonists; D018733:Nicotinic Antagonists; D011725:Pyridines; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor; C054634:methyllycaconitine; D004246:Dimethylphenylpiperazinium Iodide; D009538:Nicotine; C088936:3-(2,4-dimethoxybenzylidene)anabaseine; C082748:epibatidine; D000157:Aconitine