Worm Breeder's Gazette 14(3): 43 (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||Molecular Neurobiology Division of Basic Medcial Sciences, Royal Free Hospital School of Medicine, Rowland Hill Street, London NW3 2PF, UK|
Several putative nicotinic acetylcholine receptor (nAChR) subunit clones were isolated by screening a lambda library of Caenorhabditis elegans genomic DNA with a probe derived from the Drosophila melanogaster ard gene (a non-alpha nicotinic acetylcholine receptor subunit clone). Studies on two of these loci, acr-2, acr-3 and their gene products ACR-2 and ACR-3 are described. acr-2 is located between sup-7 and unc-6 on the X chromosome. The cDNA encoding ACR-2 was sequenced and shown to possess many of the conserved features of vertebrate and invertebrate non-alpha nicotinic acetylcholine receptor subunits. To investigate the functional expression of this subunit, the corresponding cRNA was produced and micro-injected into the cytoplasm of Xenopus oocytes. When expressed alone, ACR-2 was not able to generate levamisole-gated channels. When co-expressed with a C. elegans a subunit (UNC-38), which is itself unable to form functional homo-oligomers, ACR-2 contributed to the formation of a functional channel that was blocked by mecamylamine1. Recently, similar findings have been obtained for the product of acr-3, another non-alpha nAChR subunit encoding gene located 281bp downstream from acr-2 on the X chromosome and in the same orientation. In this case, ACR-3 encoding DNA was injected into Xenopus oocyte nuclei. As in the case of ACR-2, small cationic currents were detected in the presence of 100mM levamisole and these were blocked by mecamylamine (1mM) and d-tubocurarine (10mM). Studies on the regulation of expression of these linked non-alpha subunits are underway. The functional expression studies of nematode nicotinic acetylcholine receptors reported here support the interpretation that the differentiation between alpha and non-alpha subunits dates back to the earliest stages of metazoan evolution. 1. Squire M D, Tornøe C, Baylis, H A, Fleming, J T, Barnard E A and Sattelle DB (1995) Receptors and Channels 3, 107-115.