| 摘要 |
We describe the molecular and functional characterization of the C. elegans unc-63 gene, a levamisole resistance locus on chromosome I, which encodes a nicotinic acetylcholine receptor (nAChR) alpha subunit. The derived amino acid sequence of UNC-63 most closely resembles that of UNC-38, the product of a separate levamisole resistance locus. Using a gfp::unc-63 fusion construct, expression has been detected in muscles (body wall, vulval) and motorneurons of C. elegans. Nuclear injection into Xenopus laevis oocytes of unc-63 cDNA together with lev-1 and unc-29 results in the expression for the first time of a robust functional C. elegans heteromeric nAChR. The EC50 for ACh of the expressed receptor (20 muM) resembles that of native nematode muscle nAChRs. Nicotine and the anthelmintic drug levamisole are agonists and mecamylamine is an antagonist of this expressed receptor. When unc-38 cDNA is co-injected with cDNAs encoding unc-63, lev-1 and unc-29 much smaller amplitude agonist-activated currents are observed. The first robust functional recombinant heteromeric nAChR composed only of invertebrate subunits has therefore been characterized and shown to contain a pesticide binding site.
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