Role of Cytosolic Glyceraldehyde-3-Phosphate Dehydrogenase in Visceral Organ Infection by Leishmania donovani

Abstract

ABSTRACTThe initial 7 steps of the glycolytic pathway from glucose to 3-phosphoglycerate are localized in the glycosomes inLeishmania, including step 6, catalyzed by the enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH). InL. donovaniandL. mexicana, there exists a second GAPDH enzyme present in the cytosol that is absent inL. braziliensisand that has become a pseudogene inL. major.To investigate the role of the cytosolic GAPDH (cGAPDH), anL. donovanicGAPDH-null mutant was generated, and conversely, the functionalL. donovanicGAPDH was introduced intoL. majorand the resulting engineered parasites were characterized. TheL. donovanicGAPDH-null mutant was able to proliferate at the same rate as the wild-type parasite in glucose-deficient medium. However, in the presence of glucose, theL. donovanicGAPDH-null mutant consumed less glucose and proliferated more slowly than the wild-type parasite and displayed reduced infectivity in visceral organs of experimentally infected mice. This demonstrates that cGAPDH is functional inL. donovaniand is required for survival in visceral organs. Restoration of cGAPDH activity inL. major, in contrast, had an adverse effect onL. majorproliferation in glucose-containing medium, providing a possible explanation of why it has evolved into a pseudogene inL. major. This study indicates that there is a difference in glucose metabolism betweenL. donovaniandL. major, and this may represent an important factor in the ability ofL. donovanito cause visceral disease.