Isolation and characterization of a novel member of the ACC ligand-gated chloride channel family, Hco-LCG-46, from the parasitic nematode Haemonchus contortus

• Published in: Molecular and biochemical parasitology 2020-05, Vol.237, p.111276-111276, Article 111276
• Main Authors: Habibi, Sarah A., Blazie, Stephen M., Jin, Yishi, Forrester, Sean G.
• Format: Article
• Language: English
• Subjects: Acetylcholine - metabolism; Acetylcholine - pharmacology; Action Potentials - drug effects; Action Potentials - physiology; Aldicarb - pharmacology; Aldicarb sensitivity; Amino Acid Sequence; Animals; Anthelmintics - pharmacology; Caenorhabditis elegans - genetics; Caenorhabditis elegans - metabolism; Carbachol - metabolism; Carbachol - pharmacology; Chloride Channels - chemistry; Chloride Channels - genetics; Chloride Channels - isolation & purification; Chloride Channels - metabolism; Choline - analogs & derivatives; Choline - metabolism; Choline - pharmacology; Cloning, Molecular; Cys-loop receptor; Cysteine Loop Ligand-Gated Ion Channel Receptors - chemistry; Cysteine Loop Ligand-Gated Ion Channel Receptors - genetics; Cysteine Loop Ligand-Gated Ion Channel Receptors - isolation & purification; Cysteine Loop Ligand-Gated Ion Channel Receptors - metabolism; Gene Expression; Genetic Vectors - chemistry; Genetic Vectors - metabolism; Haemonchus - genetics; Haemonchus - metabolism; Haemonchus contortus; Helminth Proteins - chemistry; Helminth Proteins - genetics; Helminth Proteins - isolation & purification; Helminth Proteins - metabolism; Ion channels; Models, Molecular; Oocytes - cytology; Oocytes - metabolism; Parasitic nematode; Protein Structure, Secondary; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Recombinant Proteins - isolation & purification; Recombinant Proteins - metabolism; Sequence Alignment; Sequence Homology, Amino Acid; Xenopus laevis - genetics; Xenopus laevis - metabolism
• ISSN: 0166-6851; 1872-9428
• DOI: 10.1016/j.molbiopara.2020.111276

•hco-lgc-46 encodes a novel member of the ACC-1 family of ligand-gated chloride channels.•Hco-LGC-46 can associate with both Hco-ACC-1 and Hco-ACC-4 in Xenopus oocytes.•Hco-LGC-46 can suppress aldicarb sensitivity when expressed in a C. elegans lgc-46 null strain. The ACC-1 family of cys-loop receptors are ligand-gated chloride channels sensitive to acetylcholine (ACh), and are only present in invertebrates. Studies of this family of inhibitory receptors has provided insight into how they bind and respond to ACh in a manner vastly different from nicotinic acetylcholine receptors and appear to be present in tissues that are relevant to anthelmintic action. Here, we have identified two members of the ACC-1 family from the parasitic nematode Haemonchus contortus, Hco-LGC-46 and Hco-ACC-4. Hco-LGC-46 is an ACC subunit that has never been previously expressed and pharmacologically characterized. We found that Hco-LGC-46 when expressed in Xenopus laevis oocytes forms a functional homomeric channel that is responsive to the cholinergic agonists ACh and methylcholine. hco-lgc-46 expressed in a C. elegans lgc-46 null strain (ok2900) suppressed hypersensitivity to aldicarb in a manner similar to cel-lgc-46. It was also found that Hco-LGC-46 assembles with Hco-ACC-1 and produces a receptor that is over 5-fold more sensitive to ACh and responds to the cholinergic agonists methycholine and carbachol. In contrast, the co-expression of Hco-LGC-46 with Hco-ACC-4 resulted in non-functional channels in oocytes. Hco-ACC-4 also appears to form heteromeric channels with a previously characterized subunit, Hco-ACC-2. Co-expression of Hco-ACC-4 with Hco-ACC-2 resulted in a functional heteromeric channel with an EC50 value similar to that of the Hco-ACC-2 homomeric channel. However, the maximum currents generated in the ACC-4/ACC-2 channel were significantly (p < 0.005) lower than those from the ACC-2 homomeric channel. Overall, this is the first report confirming that lgc-46 encodes an acetylcholine-gated chloride channel which when co-expressed with acc-4 results in reduced receptor function or trafficking in oocytes.