GMP reductase and genetic uncoupling of adenylate and guanylate metabolism in Leishmania donovani parasites.

ABSTRACT: Purine acquisition is an essential nutritional process for Leishmania. Although purine salvage into adenylate nucleotides has been investigated in detail, little attention has been focused on the guanylate branch of the purine pathway. To characterize guanylate nucleotide metabolism in Leishmania and create a cell culture model in which the pathways for adenylate and guanylate nucleotide synthesis can be genetically uncoupled for functional studies in intact cells, we created and characterized null mutants of L. donovani that were deficient in either GMP reductase alone (?gmpr) or in both GMP reductase and its paralog IMP dehydrogenase (?gmpr/?impdh). Whereas wild type parasites were capable of utilizing virtually any purine nucleobase/nucleoside, the ?gmpr and ?gmpr/?impdh null lines exhibited highly restricted growth phenotypes. The ?gmpr single mutant could not grow in xanthine, guanine, or their corresponding nucleosides, while no purine on its own could support the growth of ?gmpr/?impdh cells. Permissive growth conditions for the ?gmpr/?impdh necessitated both xanthine, guanine, or the corresponding nucleosides, and additionally, a second purine that could serve as a source for adenylate nucleotide synthesis. Interestingly, GMPR, like its paralog IMPDH, is compartmentalized to the leishmanial glycosome, a process mediated by its COOH-terminal peroxisomal targeting signal. The restricted growth phenotypes displayed by the L. donovani ?gmpr and ?gmpr/?impdh null mutants confirms the importance of GMPR in the purine interconversion processes of this parasite.

SUBMITTER: Boitz JM 

PROVIDER: S-EPMC5010971 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature