Hco-LGC-38 is novel nematode cys-loop GABA receptor subunit

• Published in: Molecular and biochemical parasitology Vol. 185; no. 2; pp. 137 - 144
• Main Authors: Siddiqui, Salma Z., Brown, David D.R., Accardi, Michael V., Forrester, Sean G.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.10.2012
• Subjects: Amino Acid Sequence; Animals; Binding Sites; Cloning, Molecular; Dieldrin; Drosophila; Electrophysiology; fipronil; free-living nematodes; GABA receptor; gamma-aminobutyric acid; gamma-Aminobutyric Acid - metabolism; genes; Haemonchus - chemistry; Haemonchus - genetics; Haemonchus - metabolism; Haemonchus contortus; Helminth Proteins - chemistry; Helminth Proteins - genetics; Helminth Proteins - metabolism; insects; LGC-38; Ligand-gated chloride channel; Ligand-Gated Ion Channels - chemistry; Ligand-Gated Ion Channels - genetics; Ligand-Gated Ion Channels - metabolism; Models, Molecular; Molecular Sequence Data; Muscimol - metabolism; oocytes; parasitology; Phylogeny; receptors; Receptors, GABA - chemistry; Receptors, GABA - classification; Receptors, GABA - genetics; Receptors, GABA - metabolism; Sequence Analysis, DNA; Xenopus; Xenopus laevis - metabolism; Haemonchus contortus; UTR; Ligand-gated chloride channel; RACE; Electrophysiology; GABA receptor; RDL; LGC-38
• ISSN: 0166-6851; 1872-9428
• DOI: 10.1016/j.molbiopara.2012.08.004

Model of the Hco-LGC-38 ligand-binding domain with GABA docked in the binding-site at the interface of two adjacent subunits. Loops A–F which form the binding cleft are indicated. [Display omitted] ► Hco-LGC-38 is a novel nematode cys-loop GABA receptor. ► The channel is activated by both GABA and muscimol. ► The model of GABA docked into the Hco-LGC-38 binding-site shows similarity to models of other invertebrate GABA receptors. ► The Hco-LGC-38 channel is highly sensitive to picrotoxin and moderately sensitive to dieldrin and fipronil. We have identified and characterized a novel cys-loop GABA receptor subunit (Hco-LGC-38) from the parasitic nematode Haemonchus contortus. This subunit is present in parasitic and free-living nematodes and shares similarity to both the UNC-49 group of GABA receptor subunits from nematodes and the resistant to dieldrin (RDL) receptors of insects. Expression of the Hco-lgc-38 gene in Xenopus oocytes and subsequent electrophysiological analysis has revealed that the gene encodes a homomeric channel sensitive to GABA (EC50 19μM) and the GABA analogue muscimol. The sensitivity of the Hco-LGC-38 channel to GABA is similar to reported values for the Drosophila RDL receptor whereas its lower sensitivity to muscimol is similar to nematode GABA receptors. Hco-LGC-38 is also highly sensitive to the channel blocker picrotoxin and moderately sensitive to fipronil and dieldrin. Homology modeling of Hco-LGC-38 and subsequent docking of GABA and muscimol into the binding site has uncovered several types of potential interactions with binding-site residues and overall appears to share similarity with models of other invertebrate GABA receptors.