title: Exocytosis and protein secretion in Trypanosoma.
abstract: BACKGROUND
  Human African trypanosomiasis is a lethal disease caused by the extracellular parasite Trypanosoma brucei. The proteins secreted by T. brucei inhibit the maturation of dendritic cells and their ability to induce lymphocytic allogenic responses. To better understand the pathogenic process, we combined different approaches to characterize these secreted proteins.
  
  
  RESULTS
  Overall, 444 proteins were identified using mass spectrometry, the largest parasite secretome described to date. Functional analysis of these proteins revealed a strong bias toward folding and degradation processes and to a lesser extent toward nucleotide metabolism. These features were shared by different strains of T. brucei, but distinguished the secretome from published T. brucei whole proteome or glycosome. In addition, several proteins had not been previously described in Trypanosoma and some constitute novel potential therapeutic targets or diagnostic markers. Interestingly, a high proportion of these secreted proteins are known to have alternative roles once secreted. Furthermore, bioinformatic analysis showed that a significant proportion of proteins in the secretome lack transit peptide and are probably not secreted through the classical sorting pathway. Membrane vesicles from secretion buffer and infested rat serum were purified on sucrose gradient and electron microscopy pictures have shown 50- to 100-nm vesicles budding from the coated plasma membrane. Mass spectrometry confirmed the presence of Trypanosoma proteins in these microvesicles, showing that an active exocytosis might occur beyond the flagellar pocket.
  
  
  CONCLUSIONS
  This study brings out several unexpected features of the secreted proteins and opens novel perspectives concerning the survival strategy of Trypanosoma as well as possible ways to control the disease. In addition, concordant lines of evidence support the original hypothesis of the involvement of microvesicle-like bodies in the survival strategy allowing Trypanosoma to exchange proteins at least between parasites and/or to manipulate the host immune system.
authors.affiliation: UMR 177, IRD-CIRAD, CIRAD TA A-17/G, Campus International de Baillarguet, 34398 Montpellier Cedex 5, France. anne.geiger@mpl.ird.fr
authors.forename: Anne
authors.initials: A
authors.lastname: Geiger
authors.forename: Christophe
authors.initials: C
authors.lastname: Hirtz
authors.forename: Thierry
authors.initials: T
authors.lastname: Bécue
authors.forename: Eric
authors.initials: E
authors.lastname: Bellard
authors.forename: Delphine
authors.initials: D
authors.lastname: Centeno
authors.forename: Daniel
authors.initials: D
authors.lastname: Gargani
authors.forename: Michel
authors.initials: M
authors.lastname: Rossignol
authors.forename: Gérard
authors.initials: G
authors.lastname: Cuny
authors.forename: Jean-Benoit
authors.initials: JB
authors.lastname: Peltier
mesh_terms: D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D005089:Exocytosis / Q000502:physiology; D013058:Mass Spectrometry; D020543:Proteome / Q000032:analysis / Q000378:metabolism; D040901:Proteomics / Q000379:methods*; D015800:Protozoan Proteins / Q000378:metabolism*; D051381:Rats; D014347:Trypanosoma brucei gambiense / Q000145:classification / Q000166:cytology / Q000502:physiology*; D014353:Trypanosomiasis, African / Q000469:parasitology
chemical_list: D020543:Proteome; D015800:Protozoan Proteins