ACR-26: a novel nicotinic receptor subunit of parasitic nematodes

Nematode nicotinic acetylcholine receptors are the targets for many effective anthelmintics, including those recently introduced into the market. We have identified a novel nicotinic receptor subunit sequence, acr-26, that is expressed in all the animal parasitic nematodes we examined from clades III, IV and V, but is not present in the genomes of Trichinella spiralis, Caenorhabditis elegans, Pristionchus pacificus and Meloidogyne spp. In Ascaris suum, ACR-26 is expressed on muscle cells isolated from the head, but not from the mid-body region. Sequence comparisons with other vertebrate and nematode subunits suggested that ACR-26 may be capable of forming a functional homomeric receptor; when acr-26 cRNA was injected into Xenopus oocytes along with Xenopus laevis ric-3 cRNA we occasionally observed the formation of acetylcholine- and nicotine-sensitive channels. The unreliable expression of ACR-26 in vitro may suggest that additional subunits or chaperones may be required for efficient formation of the functional receptors. ACR-26 may represent a novel target for the development of cholinergic anthelmintics specific for animal parasites.