Regulation of a high-affinity diamine transport system in Trypanosoma cruzi epimastigotes

Abstract

Trypanosoma cruzi epimastigotes take up exogenous [3H]putrescine and [3H]cadaverine by a rapid, high-affinity, transport system that exhibits saturable kinetics (putrescine Km 2.0 μM, Vmax 3.3 nmol/min per 108 cells; cadaverine Km 13.4 μM, Vmax 3.9 nmol/min per 108 cells). Putrescine transport is temperature dependent and requires the presence of a membrane potential and thiol groups for activity. Its activity is altered in response to extracellular putrescine levels and as the cells proceed through the growth cycle. This transporter shows high specificity for the diamines putrescine and cadaverine, but low specificity for the polyamines spermidine and spermine. The existence of rapid diamine/polyamine transport systems whose activity can be adjusted in response to the growth conditions is of particular importance, as they seem unable to synthesize their own putrescine [Hunter, Le Quesne and Fairlamb (1994) Eur. J. Biochem. 226, 1019–1027].

Trypanosoma cruzi epimastigotes lack ornithine decarboxylase but can express a foreign gene encoding this enzyme

“…The lack of de novo putrescine synthesis in T. cruzi seems to be compensated by the presence of a constitutive and active transport system specific for putrescine which cannot be stimulated by DFMO and allows the uptake of putrescine from the external medium [8,16,17]. In contrast, other trypanosomatid protozoa such as Crithidia fitsciculata and Leishmania mexicana have shown an inducible putrescine transport system.…”

Insights into the redox biology of Trypanosoma cruzi: Trypanothione metabolism and oxidant detoxification

“…It is certain that the three stages 273 of the parasite are able to scavenge polyamines from the medium 274 [58,59]. The transporters involved in diamine uptake have been 275 functionally characterized in epimastigotes and they contain thiol 276 residues that are critical for their activity [60]. A gene coding for a 277 spermidine transporter has been expressed in an heterologous system 278 where it was shown to be functional [61].…”

Levels of Polyamines and Kinetic Characterization of Their Uptake in the Soybean Pathogen Phytophthora sojae

“…Significant quantities of polyamines may occur in the soil (54), plant phloem (2,13,21), and root nodules (22,23,40). Polyamine uptake has been studied in many microorganisms, including bacteria (27,34), yeasts (4,28), protozoans (26,35), and soil fungi (20,37). Polyamine uptake can be used to maintain cellular homeostasis, and uptake of polyamines by swimming P. sojae zoospores, heretofore believed to be dependent on internal stores until host contact (8,11,12), could increase zoospore survival and aid the development of the germinating cysts.…”