Cloning and localisation of an avermectin receptor-related subunit from Haemonchus contortus

Ivermectin is believed to exert its anthelminthic effects by binding to glu tamate-gated chloride channels (Glu-Cl) and several cDNAs encoding subunits of Glu-Cl have been cloned from Caenorhabditis elegans. We report the clon ing of cDNAs encoding a putative Glu-Cl subunit (HG4) from the parasite Hae monchus contortus. The HG4 cDNAs were isolated using RT-PCR and the sequenc e of the predicted polypeptide has 82% amino-acid identity with the C. eleg ans Glu-Cl beta subunit. Individual HG4 cDNAs showed up to 4% sequence vari ation at the nucleotide level, but the vast majority of these polymorphisms were translationally silent. A synthetic peptide corresponding to sequence near the N-terminus of the mature polypeptide was used to raise an antiser um that recognised the N-terminal domain of HG4 expressed in E. coli. Affin ity purified antibodies reacted with motor neuron commissures in immuno-loc alisation studies: these commissures were limited to the anterior portion o f the worms, from a region level with the nerve ring to just anterior of th e vulva. Some possible nerve cord staining was also observed, but no expres sion of HG4 on pharyngeal muscle could be detected. (C) 1998 Published by E lsevier Science B.V. All rights reserved.