Functional Properties Of Homomeric Human Î±7-Nicotinic Acetylcholine Receptors Heterologously Expressed In The Sh-Ep1 Human Epithelial Cell Line
Î±7-Nicotinic acetylcholine receptors (Î±7-nAChRs) are broadly distributed in the central nervous system, where they play important roles in chemical and electrical signaling, and perhaps in neurite outgrowth, synaptic plasticity, and neuronal death/survival. To help elucidate their normal and pathophysiological roles, we have heterologously expressed human Î±7-nAChR in transfected SH-EP1 human epithelial cells. Reverse transcription-polymerase chain reaction and mRNA fluorescence in situ hybridization analyses demonstrate expression of human Î±7 subunits as messenger RNA. Patch-clamp recordings exploiting a novel strategy to prevent functional rundown of whole-cell peak current responses to repeated acute challenges with nicotinic agonists show successful expression of functional Î±7-nAChR that mediate inward currents characterized by rapid phases of activation and inactivation. Concentration-response curves show that nicotine, acetylcholine, and choline are efficacious agonists at human Î±7-nAChRs. Current-voltage relationships show inward rectification for agonist-induced currents. Human Î±7-nAChRs exhibit some sensitivity to Î±7-nAChR antagonists Î±-bungarotoxin (Bgt) or methyllycaconitine (MLA) when applied coincidentally with agonist, but much higher affinity block occurs when cells and Î±7-nAChRs are pre-exposed to antagonists for 2 min before challenge with agonist. Both Bgt and MLA are competitive inhibitors of Î±7-nAChR function. Whole-cell current peak amplitudes and half-times for inactivation of Î±7-nAChR functional responses to nicotine are dramatically reduced in the absence of extracellular Ca2+, suggestive of high Ca2+ permeability of the Î±7-nAChR channel. Thus, heterologously expressed human Î±7-nAChR in mammalian cells have properties of native Î±7-nAChR or of Î±7-nAChR heterologously expressed in other systems and serve as excellent models for studies of molecular bases of Î±7-nAChR function.
Journal of Pharmacology and Experimental Therapeutics
Digital Object Identifier (DOI)
Zhao, Lingke; Kuo, Yen Ping; George, Andrew A.; Peng, Jian Hong; Purandare, Madhuri Singh; Schroeder, Katherine M.; Lukas, Ronald J.; and Wu, Jie, "Functional Properties Of Homomeric Human Î±7-Nicotinic Acetylcholine Receptors Heterologously Expressed In The Sh-Ep1 Human Epithelial Cell Line" (2003). Neurobiology. 424.