Worm Breeder's Gazette 14(3): 45 (June 1, 1996)
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
|1||The Babraham Institute Laboratory of Molecular Signalling, Department of Zoology, Downing Street, Cambridge, CB2 3EJ, UK|
|2||Massachusetts General Hospital Cancer Centre, Building 149, 13th Street, Charlestown, MA 02129, USA|
|3||Division of Life Sciences, College of Science and Engineering, The University of Texas at San Antonio, 6900 North Loop, 1604 West, San Antonio, USA|
Three of the eleven genes of the nematode C. elegans that mediate resistance to the anthelmintic drug levamisole and to other cholinergic agonists encode nicotinic acetylcholine receptor (nAChR) structural subunits1,2. The unc-38 gene encodes an alpha subunit while the lev-1 and unc-29 genes encode non-alpha subunits. The nematode nAChR subunits show conservation of many mammalian nAChR sequence features, implying an ancient evolutionary origin of nAChR proteins. Separate nuclear injection of cDNA clones in pMT3 encoding UNC-38, UNC-29 and LEV-1 failed to generate functional nAChRs. Pairwise injection of unc-38 and unc-29, consistently produced small amplitude inwardly-directed currents (Eh=-60mV) as did co-injection of either unc-38 and lev-1, or all three subunits under similar conditions. Levamisole-induced currents were in all cases suppressed by a 5min pre-treatment with 1mM mecamylamine or 10mM d-tubocurarine. Block by these nicotinic antagonists was reversible after a 15-20 min wash in saline. Thus, expression in Xenopus oocytes of combinations of these subunits that include the unc-38 alpha subunit resulted in levamisole-induced currents that were suppressed by the nAChR antagonists that block native nematode nAChRs The identification of viable nAChR mutants in C. elegans provides a system in which several aspects of nAChR receptor function, assembly and regulation of expression can be addressed experimentally. 1. Lewis J A, Wu C-H, Berg H and Levine J H (1987) Mol. Pharmacol. 31, 185-193 2. Fleming J T, Tornøe C, Riina H A, Coadwell J, Lewis J A and Sattelle D B (1993) Comparative Molecular Neurobiology (ed Pichon Y) 65-80, Springer-Verlag, Berlin.