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.

Functional expression in Xenopus oocytes of hetero-oligomeric nicotinic acetylcholine receptors of Caenorhabditis elegans

Katzuhiko Matsuda1, Howard A Baylis1, Michael D Squire1, John T Fleming2, James A Lewis3, David B Sattelle1

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,

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.