  Background: Trypanosoma brucei is the causative agent of human African
sleeping sickness and Nagana in cattle. In addition to being an important
pathogen T. brucei has developed into a model system in cell biology. Results:
Using Stable Isotope Labelling of Amino acids in Cell culture (SILAC) in
combination with mass spectrometry we determined the abundance of >1600
proteins in the long slender (LS), short stumpy (SS) mammalian bloodstream form
stages relative to the procyclic (PC) insect-form stage. In total we identified
2645 proteins, corresponding to ~30% of the total proteome and for the first
time present a comprehensive overview of relative protein levels in three life
stages of the parasite. Conclusions: We can show the extent of pre-adaptation
in the SS cells, especially at the level of the mitochondrial proteome. The
comparison to a previously published report on monomorphic in vitro grown
bloodstream and procyclic T. brucei indicates a loss of stringent regulation
particularly of mitochondrial proteins in these cells when compared to the
pleomorphic in vivo situation. In order to better understand the different
levels of gene expression regulation in this organism we compared mRNA steady
state abundance with the relative protein abundance-changes and detected
moderate but significant correlation indicating that trypanosomes possess a
significant repertoire of translational and posttranslational mechanisms to
regulate protein abundance.
