POST-TRANSLATIONAL MODIFICATION WITH LIPOIC ACID OF Caenorhabditis elegans PROTEINS

DE MENDOZA D; MANSILLA, MC; LAVATELLI, A

Montevideo

Congreso; First Latin American Worm Meeting; 2017

Lipoic acid (LA)is a sulfur-containing cofactor which is present in multienzymes complexesinvolved in oxidative metabolism in all three domains of life. Lipoylationpathways are very well characterized among prokaryotes, while informationconcerning eukaryotes is scarce. Human patients with defects in proteinlipoylation suffer from severe neurological disorders and they receivetreatments just to alleviate symptoms. For this reason, we started toinvestigate how proteins become modified with LA in the nematode Caenorhabditis elegans. By in silico analyses we found two nematodeproteins with considerable identity percentages with bacterial, human and yeastenzymes involved in lipoylation. One of them, M01F1.3, has homology withlipoate synthases. Worms subjected to RNA interference (RNAi) experimentsagainst M01F1.3 suffered larval arrestand never developed embryos. It was confirmed by Western blot analyses thatthese treated worms had reduced protein lipoylation levels. The arrested phenotypecould not be rescued by the addition of exogenous LA but could be partiallyrescued when branched chain fatty acid C15ISO was supplied. We performedcomplementation assays in bacterial strains defective in protein lipoylationand found that M01F1.3 was only able to rescue a Bacillus subtilis lipoate synthase mutant. The other protein,C45G3.3, has sequence similarity with bacterial lipoate ligases. Worms treatedwith RNAi against C45G3.3 had novisible phenotype neither had affected their protein lipoylation levels. However,this protein was able to complement a Saccharomycescerevisiae lip3 mutant andrestored the ability of a B. subtilislipM lplJ double mutant to grow in aminimal medium when supplemented with octanoate but not with LA. These resultssuggest that C45G3.3 is indeed involved in worm protein lipoylation.