Ecto-ATPases are surface enzymes able to hydrolyze extracellular ATP. Our group had characterized this class of enzymes in different cell types as protozoa and fungi. Some functions are suggested for these proteins: cell adhesion, protection against cytotoxic effects of ATP and, recently, MDR phenomenon. Some enzyme activities are stimulated in response to stress such as heat, drug or osmotic. A well-known family of these enzymes is heat-shock proteins (HSP). These enzymes present ATPase activity and are up-regulated when the cells are submitted to the heat-stress.
In this work, we verified if Ecto-ATPase activities from Trypanosoma sp can be members of the HSP family. This fact becomes relevant because these parasites alters your life cycle between several host cells, presenting different temperature environments. For this purpose, cells were submitted to heat-stress (37ºC). After pre incubation at 37ºC, the cells were used to determine Mg2+-dependent Ecto-ATPase activity by the measurement of the 32Pi release from the substrate [g-32Pi]ATP.
Our results show that Ecto-ATPase from T. cruzi was increased in a incubation time-dependent manner. This effect can be observed at the first hour of incubation at 37ºC (50%) and after four hours, there was a progressive increase in activity (around 6-fold).
The inhibition by DIDS and suramin was the same in the cells maintained at 28 or 37ºC (80 and 60%, respectively), suggesting that the stimulation by the heat-stress is an effect on ATPase activity and not at the other enzyme expression. In addition, two strains of T. cruzi showed different stimulation pattern by the heat-stress. At four hours of heat incubation, the percentage of stimuli was, approximately, 6- and 2- fold higher for Y or Dm28c strain, respectively.
Studying the effects of heat-stress on the Ecto-ATPase activity of another parasite, T. rangeli, we showed that the preincubation of the cells at 37ºC for 2 hours inhibited around the 60% this activity. Take together, these data could be indicating different strategies to cell survival in the mammals’ organisms.
Supported by CNPq, CAPES and FAPERJ.