Leishmania amazonensis: Effects of heat shock on ecto-ATPase activity

Abstract

In this work we demonstrated that promastigotes of Leishmania amazonensis exhibit an Mg-dependent ecto-ATPase activity, which is stimulated by heat shock. The Mg-dependent ATPase activity of cells grown at 22 and 28°C was 41.0±5.2nmol Pi/h×107cells and 184.2±21.0nmol Pi/h×107cells, respectively. When both promastigotes were pre-incubated at 37°C for 2h, the ATPase activity of cells grown at 22°C was increased to 136.4±10.6nmol Pi/h×107 whereas that the ATPase activity of cells grown at 28°C was not modified by the heat shock (189.8±10.3nmol Pi/h×107cells). It was observed that Km of the enzyme from cells grown at 22°C (Km=980.2±88.6μM) was the same to the enzyme from cells grown at 28°C (Km=901.4±91.9μM). In addition, DIDS (4,4′-diisothiocyanatostilbene 2,2′-disulfonic acid) and suramin, two inhibitors of ecto-ATPases, also inhibited similarly the ATPase activities from promastigotes grown at 22 and 28°C. We also observed that cells grown at 22°C exhibit the same ecto-phosphatase and ecto 3′- and 5′-nucleotidase activities than cells grown at 28°C. Interestingly, cycloheximide, an inhibitor of protein synthesis, suppressed the heat-shock effect on ecto-ATPase activity of cells grown at 22°C were exposed at 37°C for 2h. A comparison between the stimulation of the Mg-dependent ecto-ATPase activity of virulent and avirulent promastigotes by the heat shock showed that avirulent promastigotes had a higher stimulation than virulent promastigotes after heat stress.