RdlDv, a novel GABA-gated chloride channel gene from the American dog tick Dermacentor variabilis

The American dog tick Dermacentor variabilis is a major transmitter of bacterial and viral pathogens in human and animal populations, and compounds active against this species would benefit both human and animal health. Invertebrate GABA-gated chloride channels are validated targets of commonly used insecticides and acaricides. We cloned a novel member of the invertebrate GABA-gated chloride channel gene family from Dermacentor variabilis, Rdl(Dv). The closest homologue of the predicted gene product of Rdl(Dv) is the RDL protein encoded by the GABA-gated chloride channel gene Drosophila Rdl (Resistance to Dieldrin), with which it shares 64% amino acid identity. When expressed in Xenopus oocytes, Rdl(Dv) produces GABA-activated currents blocked by the known insecticides and RDL antagonists fipronil and picrotoxinin. These results suggest that Rdl(Dv) encodes a GABA-gated chloride channel subunit, making it a potential target for compounds active against the tick D. variabilis. (C) 2003 Elsevier Science Ltd. All rights reserved.