Inducible, heterologous expression of human alpha 7-nicotinic acetylcholine receptors in a native nicotinic receptor-null human clonal line

Tetracycline-regulated expression of recombinant nicotinic acetylcholine re ceptors (nAChR) composed of human alpha 7 subunits is achieved in native nA ChR-null SH-EP1 human epithelial cells. alpha 7 subunits are heterologously expressed as messenger RNA and as components of I-125-labeled alpha-bungar oloxin (I-Bgt)-binding nAChR (similar to 10 pmol per milligram of membrane protein) at levels sensitive to the amount of tetracycline in cell growth m edium. I-Bgt-binding alpha 7-nAChR appear on the cell surface pool and in i ntracellular pools. The pharmacological profile for drug competition toward I-Bgt binding to these recombinant alpha 7-nAChR matches that of human nat ive alpha 7-nAChR naturally expressed in SH-SY5Y human neuroblastoma cells (rank order potency methyllycaconitine > 1,1-dimethyl-4-phenylpiperazinium > (-)nicotine > cytisine > carbamylcholine greater than or equal to D-tuboc urarine). Chronic exposure to nicotine induces up-regulation of human recom binant alpha 7-nAChR (80% up-regulation at 10 mu M nicotine) just as it doe s native alpha 7-nAChR in other human cell lines. These studies confirm exp ression of nAChR as homooligomers of human alpha 7 subunits from transgenes , establish a native nAChR-null background for such expression, and demonst rate that this expression can be regulated to facilitate studies of human a lpha 7-nAChR. (C) 1999 Elsevier Science B.V. All rights reserved.