Phosphorylation of proteins in virulent promastigotes from Leishmania major

Protein kinases are present in the plasma membrane of the human parasite Leishmania. A marked increase in enzyme activity has been detected as cultures entered into the stationary phase of growth. Since avirulent parasites can be separated from virulent forms by the peanut agglutinin (PNA), we have examined the change in the protein kinase activity of L. major during growth in vitro and the difference in phosphorylation with virulent promastigotes (PNA-) of L. major. Marked similarities were found between the phosphorylation patterns of the logarithmic and stationary phase promastigotes of L. major. On the other hand, when the phosphorylation pattern of those proteins, shared by both the metacyclic (PNA-) promastigotes and the stationary phase cells, was examined, a marked increase in both the total number of phosphoproteins and the extent of their phosphorylation was observed in PNA-. Both the increase in protein kinase activity in the stationary phase parasites and the marked changes in phosphorylation in the highly infective promastigotes, may provide a clue as to the adaptative mechanism which enable promastigotes to survive within the vertebrate host

Extracellular dephosphorylation in the parasite, leishmania major / Desfosforilacion extracelular en el parasito, leishmania major

Leishmania major promastigotes were analyzed for the presence of protein phosphatase activity in intact cells and membrane-enriched fractions. Parasite phosphoprorylated in live cells with {*-32P} adenosine 5'-triphosphate (ATP) and an edogemous leishmanial ectokinase, were dephosphorylated by endogenous protein phosphatase like activity in intact cells and membrane-rich fractions. An alkaline phosphatase-like activity was also identified using the artificial substrate, p-nitrophenyl phosphate (pNPP). This activity was localized on the extracellular membrane of intact parasite, as well as in the particulate fraction of lysed cells. The phosphatase activity measure using pNPP had inhibition properties and a pH profile between protein phosphatases and general alkaline phosphatase. This study supports the observation that there is extracellular protein phosphorylation/dephosphorylation in L.major which may play a significant role in host-cell-parasite recognition and infection