Leishmania major : detection of membrane-bound protein tyrosine phosphatase
M M Aguirre-García1, A R Escalona-Montaño, N Bakalara
1Departamento de Medicina Experimental, Facultad de Medicina, Universidad Nacional Autónoma de México, México, D.F., México. maguirre@servidor.unam.mx
Abstract:
PTPases have been reported as a virulence factor in different pathogens. Recent studies suggest that PTPases play a role in the pathogenesis of Leishmania infections through activation of macrophage PTPases by the parasite. We report here the presence of a membrane-bound PTPase in Leishmania major promastigotes. We detected differences in the PTPases present in the procyclic and metacyclic stages of promastigotes. In metacyclic promastigotes, the PTPase activity was totally inhibited by specific PTPase and serine/threonine inhibitors, whereas in procyclic promastigotes the PTPase activity was inhibited only with PTPase inhibitors. Two antibodies against the catalytic domains of the human placental PTPase1B and a PTPase from Trypanosoma brucei cross-reacted with a 55-60 kDa molecule present in the soluble detergent-extracted fraction of a Leishmania homogenate. Metacyclic promastigotes expressed more of this molecule than parasites in the procyclic stage. Yet the specific activity of the enzyme was lower in metacyclic than in procyclic promastigotes. Ultrastructural localization of the enzyme showed that it was more membrane-associated in metacyclic promastigotes, whereas in procyclic promastigotes it was scattered throughout the cytoplasm. This is the first demonstration of a PTPase present in Leishmania major promastigotes that differs in expression, activity and ultrastructural localization between the procyclic and metacyclic stages of the parasite's life-cycle.
Insights
This study identifies a membrane-bound protein tyrosine phosphatase (PTPase) in Leishmania major promastigotes. Its expression, activity, and localization differ between the procyclic and metacyclic stages, suggesting a role in parasite development.
Area of Science:
- Parasitology
- Molecular Biology
- Biochemistry
Background:
- Protein tyrosine phosphatases (PTPases) are implicated as virulence factors in pathogens.
- Leishmania infections may involve parasite-mediated activation of host macrophage PTPases.
- The role of parasite-specific PTPases in Leishmania pathogenesis is under investigation.
Purpose of the Study:
- To identify and characterize a PTPase in Leishmania major promastigotes.
- To investigate differences in PTPase expression, activity, and localization between procyclic and metacyclic stages.
- To explore the potential role of this PTPase in the parasite's life cycle.
Main Methods:
- Biochemical assays to measure PTPase activity and inhibition.
- Immunological detection using antibodies against human and trypanosome PTPases.
- Western blotting to identify the PTPase molecule.
- Ultrastructural localization studies using electron microscopy.
Main Results:
- A membrane-bound PTPase was detected in Leishmania major promastigotes.
- Significant differences in PTPase activity and inhibitor sensitivity were observed between procyclic and metacyclic stages.
- A 55-60 kDa PTPase molecule was identified, with higher expression in metacyclic forms.
- Ultrastructural analysis revealed distinct localization patterns: membrane-associated in metacyclic and cytoplasmic in procyclic stages.
Conclusions:
- Leishmania major promastigotes possess a PTPase with stage-specific characteristics.
- The observed differences in expression, activity, and localization suggest a role for this PTPase in parasite differentiation and/or infectivity.
- This finding provides the first evidence of stage-dependent PTPase variation in Leishmania major.
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