Isolation and characterization of a novel glutamate-gated chloride channel subunit (GLC-2) from the canine heartworm Dirofilaria immitis.

Dirofilaria immitis is a parasitic nematode responsible for canine heartworm disease. Current heartworm treatment options include melarsomine chloridrate (an arsenical) to treat adult parasites and the macrocyclic lactones. Unfortunately, resistance to macrocyclic lactones is emerging which is highlighting the need for the discovery of new anthelmintics. Cys-loop ligand-gated ion channels are an untapped source for novel drug targets essential for nematode neurotransmission. This work presents the isolation and preliminary pharmacological characterization of a glutamate-gated chloride channel, GLC-2, from D. immitis. Expression levels of GLC-2, identified in the adult female, adult male and microfilaria (Mf) life stages, were measured via qPCR, with highest expression found in the adult stages. Dim-GLC-2 forms homomeric channels with low sensitivity to monosodium L-glutamate (MSG) and L-glutamic acid. Homodimer models were created to visualize docking of glutamate to the binding site, and several potential interactions were identified and compared to the original crystal structure of the glutamate-gated chloride channel from Caenorhabditis elegans.