Pharmacological characterization of novel heteromeric GluCl subtypes from Caenorhabditis elegans and parasitic nematodes

Abstract

Background and Purpose: Macrocyclic lactones are the most widely used broadspectrum anthelmintic drugs for the treatment of parasitic nematodes affecting both human and animal health. Macrocyclic lactones are agonists of the nematode glutamate-gated chloride channels (GluCls). However, for many important nematode species, the GluCls subunit composition and pharmacological properties remain largely unknown. To gain new insights into GluCl diversity and mode of action of macrocyclic lactones, we identified and pharmacologically characterized receptors made of highly conserved GluCl subunits from the model nematode Caenorhabditis elegans, the human filarial nematode Brugia malayi and the horse parasite Parascaris univalens.Experimental Approach: AVR-14, GLC-2, GLC3 and GLC-4 are the most conserved GluCl subunits throughout the Nematoda phylum. For each nematode species, we investigated the ability of these subunits to form either homomeric or heteromeric GluCls when expressed in Xenopus laevis oocytes and carried out detailed pharmacological characterization of the functional channels.Key Results: A total of 14 GluCls were functionally reconstituted, and heteromers formation was inferred from pharmacological criteria. The GLC-2 subunit plays a pivotal role in the composition of heteromeric GluCls in nematodes. We also found a novel GluCl subtype, combining GLC-2/GLC-3 subunits, for which a high concentration of the anthelmintics ivermectin and moxidectin reversibly potentiates glutamateinduced response. Conclusion and Implications: This study brings new insights into the diversity ofGluCl subtypes in nematodes and promotes novel drug targets for the development of the next generation of anthelmintic compounds.Abbreviation: GluCl, glutamate-gated chloride channel.

Database of glutamate-gated chloride (GluCl) subunits across 125 nematode species: patterns of gene accretion and sequence diversification

“…These observations suggest that GLC-1 and AVR-15 may represent a more recent duplication event that may postdate a duplication event from GLC-3. This phylogenetic relationship is in keeping with recent observations from another group ( Lamassiaude et al 2021 ) and is further supported by the synteny of GluCl genes within C. elegans in which both GLC-1 and AVR-15 are closely linked on chromosome V while GLC-3 is located toward the other end of chromosome V ( Supplementary Fig. 4 ).…”

“…To classify the remaining 499 GluCl subunit genes from the 864 total GluCl gene predictions into orthologous clusters, we used the conserved 365 predicted GluCl subunit genes that we described above alongside functionally characterized GluCl subunits ( Lamassiaude et al 2021 ) to create a database which we interrogated using blastp searches to cluster into orthologous groups based on top blastp hits. These data alongside the conserved 365 predicted GluCl subunit genes were converted into JSON tables to build an online database that included all 864 predicted GluCl sequences.…”

Analysis of P-gp genes relative expression associated to ivermectin resistance in Haemonchus contortus larval stages from in vitro cultures (L3 and xL3) and from gerbils (Meriones unguiculatus) (L4) as models of study

“…However, as a P-gp identifier, C. elegans has some limitations in its genome compared with GIN of ruminants. Fourteen P-gp genes are identified, but some of them are absent, such as P-gp16 (Williamson and Wolstenholme 2012; Lamassiaude et al 2022). Thus, the study of endoparasitic stages is crucial since they share a close relationship with their host and they could be used as one of the main anthelmintic targets (Reyes-Guerrero et al 2021).…”

A new family of glutamate-gated chloride channels in parasitic sea louse Caligus rogercresseyi: A subunit refractory to activation by ivermectin is dominant in heteromeric assemblies

“…Invertebrate glutamate receptors belong to the Cys loop ligand-gated ion channel (LGIC) group of proteins that can assemble as homopentamers or heteromers of different stoichiometries. Most of the GluCl subunits successfully expressed in vitro have been homomeric [18] but there are instances of heteromeric assembly in coexpression experiments in vitro that give rise to activities with novel properties [35][36][37][38]. The subunit composition of native GluCls is not known in species with genes coding for multiple subunits.…”

“…Interestingly, a recent paper [38] describes a variety of GluCl subunits in the parasitic nematodes Brugia malayi and Parascaris univalens which are orthologues to C. elegans receptors AVR-14B, GLC-2, GLC-3 and GLC-4. Functional expression of these reveals no or very low activity as GluCls when expressed on their own.…”