Partially redundant function of UDP glycosyltransferase (ugt) genes in the modulation of benzimidazole sensitivity in the nematode Caenorhabditis elegans
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2021-12-10
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Abstract
The benzimidazoles (BZ) are a family of anthelmintics used in livestock and human parasitic nematode control. Our previous work has shown that the free-living model nematode Caenorhabditis elegans and the parasite Haemonchus contortus detoxify BZ anthelmintics by conjugation with a glucose residue. This suggests the involvement of phase II drug metabolizing enzymes, specifically the UDP-glycosyltransferase (UGT) enzyme family, whose expression is induced by BZ drug exposure. First, the UGT gene family of C. elegans was characterized by phylogenetic analysis, RNA-seq expression data and an RNAi screen. Phylogenetic analysis revealed none of the C. elegans and H. contortus UGT enzymes or clusters shared a clear orthologous relationship to any of the human UGT families. Existing RNA-seq expression data of the C. elegans ugt gene family identified that most of the ugts were less expressed in all developmental stages and many of them displayed enriched expression in the gut. Next, an RNAi screening identified that knockdown of ugt-9, ugt-11 and ugt-22 make worms sensitive to albendazole (ABZ) treatment compared to wild type. However, the RNAi knockdown of ugt-9 and ugt-11 potentially have “off target” effects and, based on their high level of sequence identity with six other ugt genes that are tightly linked in a cluster on chromosome V. This “ugt-9 cluster” includes ugt-9 and ugt-11, but not ugt-22. Next, I undertook a detailed genetic analysis of the ugt-9 cluster genes and demonstrated the importance of both ugt-9 and ugt-11 in modulating the potency of BZ drugs in vivo. These two genes appear to have partially redundant functions with respect to modulating in vivo BZ sensitivity, both with each other and other genes of the ugt-9 cluster, as well as with ugt-22. Further, expression patterns of ugt-9, ugt-11 and ugt-22 reporter genes are consistent with a lack of complete functional redundancy. Furthermore, in vivo overexpression of ugt-9 was sufficient to confer ABZ resistance in wild-type worms, supporting the role of this gene in ABZ biotransformation. Overall, this work identified multiple UGT enzymes that can modulate BZ potency in C. elegans in a partially redundant manner due to their non-overlapping in vivo expression patterns. Equivalent enzymes in parasitic nematodes could potentially represent “druggable” targets to improve BZ potency and warrant further investigation for a potential role in anthelmintic resistance.
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Sharma, N. (2021). Partially redundant function of UDP glycosyltransferase (ugt) genes in the modulation of benzimidazole sensitivity in the nematode Caenorhabditis elegans (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.