Exoproteome dynamics in Leishmania infantum

The exoproteome of Leishmania infantum is composed of parasite derived proteins present in the extracellular environment. Although the exoproteome might have a significant role in the precocious steps of infection little is known concerning its composition. We developed an approach enabling the in vitro recovery of the exoproteome from logarithmic and stationary L. infantum promastigotes. The recovered exoproteomes were further separated into two fractions, vesicles and vesicle depleted exoproteome, evaluating the fraction protein profile. Although the most abundant protein in all fractions was GP63, the protein composition of the separated fractions was distinct reflecting the origin of the fraction and the metabolic state of the parasites. The vesicle-derived exoproteome recovered from logarithmic parasites was significantly enriched in ribosomal proteins, indicating a potential role for these vesicles in protein turnover. Also, a stage specific enrichment of vesicles with properties related to apoptotic vesicles was observed in stationary phase parasites and evidence was obtained that the release of vesicles was increased in response to a death stimuli. This report on the exoproteome obtained from in vitro promastigote cultures provides new perspectives on Leishmania biology with the possibility of vesicles playing a major role in protein turnover and also in cell death.

Biological significance: The first systematic insight into Leishmania exoproteome composition and the impact of the selected recovery approach.