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.

acr-2, acr-3: a pair of linked genes on chromosome X encoding non-alpha nicotinic acetylcholine receptor subunits (ACR-2, ACR-3) capable of functional co-expression in Xenopus oocytes with UNC-38 to yield small amplitude cationic currents

David B Sattelle1, Katzuhiko Matsuda1, Michael D Squire1, Camilla Tornøe1, Howard A Baylis1, John T Fleming2, Eric A Barnard3

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

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.