Critical functions of the polyamine putrescine for proliferation and viability of Leishmania donovani parasites

Abstract

Polyamines are metabolites that play important roles in rapidly proliferating cells, and recent studies have highlighted their critical nature in Leishmania parasites. However, little is known about the function of polyamines in parasites. To address this question, we assessed the effect of polyamine depletion in Leishmania donovani mutants lacking ornithine decarboxylase (Δodc) or spermidine synthase (Δspdsyn). Intracellular putrescine levels depleted rapidly in Δodc mutants and accumulated in Δspdsyn mutants, while spermidine levels were maintained at low but stable levels in both cell lines. Putrescine depletion in the Δodc mutants led to cell rounding, immediate cessation of proliferation, and loss of viability, while putrescine-rich Δspdsyn mutants displayed an intermediate proliferation phenotype and were able to arrest in a quiescent-like state for 6 weeks. Supplementation of Δodc mutants with spermidine had little effect on cell proliferation and morphology but enabled parasites to persist for 14 weeks. Thus, putrescine is not only essential as precursor for spermidine formation but also critical for parasite proliferation, morphology, and viability.

Polyamine Metabolism in Leishmania Parasites: A Promising Therapeutic Target

“…Deletion of the ODC gene in L. donovani led to growth arrest in promastigotes, axenic, and intracellular amastigotes, and it profoundly reduced infectivity in mice [ 57 , 107 , 111 , 127 ]. When ODC gene deletion mutants were incubated in polyamine-free media, intracellular putrescine pools were rapidly depleted while levels of spermidine, though initially decreased, were sustained at stable levels for over 12 days [ 57 , 127 ].…”

“…Deletion of the ODC gene in L. donovani led to growth arrest in promastigotes, axenic, and intracellular amastigotes, and it profoundly reduced infectivity in mice [ 57 , 107 , 111 , 127 ]. When ODC gene deletion mutants were incubated in polyamine-free media, intracellular putrescine pools were rapidly depleted while levels of spermidine, though initially decreased, were sustained at stable levels for over 12 days [ 57 , 127 ]. Although it remains unclear how spermidine levels were maintained in these mutants, it is possible that the back-conversion of trypanothione to spermidine via the bifunctional trypanothione synthetase-amidase helps to maintain intracellular spermidine levels.…”

Toward New Antileishmanial Compounds: Molecular Targets for Leishmaniasis Treatment

“…ODC metabolizes ornithine to the diamine putrescine by its catalytic action [59]. Although alpha-difluoromethylornithine (DFMO) is an irreversible inhibitor of ODC, DFMO has not shown any antileishmanial activity [60].…”

A Double Line of Defense: Heat Shock Proteins and Polyamines Act as Contributing Factors to Drug Resistance of some Plasmodium Parasites

“…When the Anopheles mosquito bites a human during its blood meal, the parasite is then transferred to a human host. It is reported that the temperature in the mosquito vector is about 22°C, whereas in the human host the normal body temperature is 37°C, but when the malaria symptoms kick in, the temperature goes as high as 38°C and above [3][4][5]. However, these sudden temperature changes do not affect the parasite viability.…”

“…For example, when cells that lack polyamines are added with polyamines and exposed to a temperature above 37°C, the cells do survive [7], signifying that polyamines display chaperone activities. Wide studies conducted in plant biochemistry demonstrated that when plant cells are exposed to abiotic temperature, polyamines protect plant cells and improve growth and production [3]. In P. falciparum, it could be that polyamines do cooperate with heat shock proteins as means for the parasite to survive under harsh conditions.…”