Trypanosoma cruzi: Effects of heat shock on ecto-ATPase activity

[Display omitted] ► Trypanosoma cruzi is able to hydrolyze extracellular ATP. ► Trypanosoma cruzi exhibit an ecto-ATPase activity that is stimulated by heat shock. ► Cycloheximide, suppressed the heat shock effect of the ecto-ATPase activity. In this work, we demonstrate that Trypanosoma cruzi Y strain epimastigotes exhibit Mg2+-dependent ecto-ATPase activity that is stimulated by heat shock. When the epimastigotes were incubated at 37°C for 2h, the ecto-ATPase activity of the cells was 43.95±0.97nmol Pi/h×107 cells, whereas the ecto-ATPase activity of cells that were not exposed to heat shock stress was 16.97±0.30nmol Pi/h×107 cells. The ecto-ATPase activities of cells, that were exposed or not exposed to heat shock stress had approximately the same Km values (2.25±0.26mM ATP and 1.55±0.23mM ATP, respectively) and different Vmax values. The heat-shocked cells had higher Vmax values (54.38±3.07nmol Pi/h×107 cells) than the cells that were not exposed to heat shock (19.38±1.76nmol Pi/h×107 cells). We also observed that the ecto-phosphatase and ecto-5′nucleotidase activities of cells that had been incubated at 28°C or 37°C were the same. Interestingly, cycloheximide, an inhibitor of protein synthesis, suppressed the heat shock effect of ecto-ATPase activity on T. cruzi. The Mg2+-dependent ecto-ATPase activity from the Y strain (high virulence) was approximately 2-fold higher than that of Dm28c (a clone with low virulence). In addition, these two strains presented different responses to heat shock with regard to their ecto-ATPase activities; Y strain epimastigotes had a stimulation of 2.52-fold while the Dm28c strain had a 1.71-fold stimulation. In this context, the virulent trypomastigote form of T. cruzi, Dm28c, had an ecto-ATPase activity that was more than 7-fold higher (66.67±5.98nmol Pi/h×107 cells) than that of the insect epimastigote forms (8.91±0.76nmol Pi/h×107 cells). This difference increased to approximately 10-fold when both forms were subjected to heat shock stress (181.14±16.48nmol Pi/h×107 cells for trypomastigotes and 16.71±1.17nmol Pi/h×107 cells for epimastigotes at 37°C). The ecto-ATPase activity of a plasma membrane-enriched fraction obtained from T. cruzi epimastigotes was not increased by heat treatment, which suggested that cytoplasmic components had an influence on enzyme activation by heat shock stress.