Heterologous Expression Of Human Î±6Î²4Î²3Î±5 Nicotinic Acetylcholine Receptors: Binding Properties Consistent With Their Natural Expression Require Quaternary Subunit Assembly Including The Î±5 Subunit
Heterologous expression and lesioning studies were conducted to identify possible subunit assembly partners in nicotinic acetylcholine receptors (nAChR) containing Î±6 subunits (Î±6* nAChR). SH-EP1 human epithelial cells were transfected with the requisite subunits to achieve stable expression of human Î±6Î²2, Î±6Î²4, Î±6Î²2Î²3, Î±6Î²4Î²3, or Î±6Î²4Î²3Î±5 nAChR. Cells expressing subunits needed to form Î±6Î²4Î²3Î±5 nAChR exhibited saturable [3H]epibatidine binding (Kd = 95.9 Â± 8.3 pM and Bmax = 84.5 Â± 1.6 fmol/mg of protein). The rank order of binding competition potency (Ki) for prototypical nicotinic compounds was Î±-conotoxin Mll (6 nM) > nicotine (156 nM) âˆ¼ methyllycaconitine (200 nM) > Î±-bungarotoxin (>10 Î¼M), similar to that for nAChR in dopamine neurons displaying a distinctive pharmacology. 6-Hydroxydopamine lesioning studies indicated that Î²3 and Î±5 subunits are likely partners of the Î±6 subunits in nAChR expressed in dopaminergic cell bodies. Similar to findings in rodents, quantitative real-time reverse transcription-polymerase chain reactions of human brain indicated that Î±6 subunit mRNA expression was 13-fold higher in the substantia nigra than in the cortex or the rest of the brain. Thus, heterologous expression studies suggest that the human Î±5 subunit makes a critical contribution to Î±6Î²4Î²3Î±5 nAChR assembly into a ligand-binding form with native Î±6*-nAChR-like pharmacology and of potential physiological and pathophysiological relevance.
Journal of Pharmacology and Experimental Therapeutics
Digital Object Identifier (DOI)
Grinevich, Vladimir P.; Letchworth, Sharon R.; Lindenberger, Kari A.; Menager, Jean; Mary, Veronique; Sadieva, Khalima A.; Buhlman, Lori M.; Bohme, Georg Andrees; Pradier, Laurent; Benavides, Jesus; Lukas, Ronald J.; and Bencherif, Merouane, "Heterologous Expression Of Human Î±6Î²4Î²3Î±5 Nicotinic Acetylcholine Receptors: Binding Properties Consistent With Their Natural Expression Require Quaternary Subunit Assembly Including The Î±5 Subunit" (2005). Neurobiology. 228.