Project description:The infectious metacyclic forms of Trypanosoma brucei result from a complex development in the tsetse fly vThe infectious metacyclic forms of Trypanosoma brucei result from a complex development in the tsetse fly vector. When they infect mammals, they cause African sleeping sickness in humans. Due to scarcity of biological material and difficulties of the tsetse fly as an experimental system, very limited information is available concerning the gene expression profile of metacyclic Trapanosoma forms. We used an in vitro system based on expressing the RNA binding protein 6 (RBP6) to obtain infectious metacyclics and determined their protein and mRNA repertoires by mass-spectrometry (MS) based proteomics and mRNA sequencing (RNAseq) in comparison to non-infectious procyclic trypanosomes. This comparison showed that metacyclics are quiescent cells, and we propose this influences the choice of a monocistronic variant surface glycoprotein expression site. Metacyclics have a largely bloodstream-form type transcriptome, and thus are programmed to translate a bloodstream-form type proteome upon entry into the mammalian host and resumption of cell division. Genes encoding cell surface components showed the largest changes between procyclics and metacyclics, observed at both the transcript and protein levels. Genes encoding metabolic enzymes exhibited expression in metacyclics with features of both procyclic and bloodstream forms, suggesting that this intermediate-type metabolism is dictated by the availability of nutrients in the tsetse fly vector. ector. When they infect mammals, they cause African sleeping sickness in humans. Due to scarcity of biological material and difficulties of the tsetse fly as an experimental system, very limited information is available concerning the gene expression profile of metacyclic Trapanosoma forms. We used an in vitro system based on expressing the RNA binding protein 6 (RBP6) to obtain infectious metacyclics and determined their protein and mRNA repertoires by mass-spectrometry (MS) based proteomics and mRNA sequencing (RNAseq) in comparison to non-infectious procyclic trypanosomes. This comparison showed that metacyclics are quiescent cells, and we propose this influences the choice of a monocistronic variant surface glycoprotein expression site. Metacyclics have a largely bloodstream-form type transcriptome, and thus are programmed to translate a bloodstream-form type proteome upon entry into the mammalian host and resumption of cell division. Genes encoding cell surface components showed the largest changes between procyclics and metacyclics, observed at both the transcript and protein levels. Genes encoding metabolic enzymes exhibited expression in metacyclics with features of both procyclic and bloodstream forms, suggesting that this intermediate-type metabolism is dictated by the availability of nutrients in the tsetse fly vector.

Project description:Background: Tsetse flies serve as biological vectors for several species of African trypanosomes. In order to survive, proliferate and establish a midgut infection, trypanosomes must cross the tsetse fly peritrophic matrix (PM), an acellular gut lining surrounding the blood meal. Crossing of this multi layered structure occurs at least twice during parasite migration and development, but the mechanism of how they do so is poorly understood. In order to better comprehend the molecular events surrounding trypanosome crossing of the tsetse PM, a mass spectrometry-based approach was applied to investigate the PM protein composition using Glossina morsitans morsitans as a model organism. Methods: Urea-SDS extracts of tsetse PM proteins were either subject to an in solution tryptic digestion or fractionated on 1D SDS-PAGE and the resulting bands digested with trypsin. The tryptic fragments from both preparations were purified and analysed by 2D-LC-MS/MS. Tandem MS data were searched against the Glossina-morsitans-Yale_PEPTIDES_GmorY1.1 database downloaded from VectorBase (https://www.vectorbase.org/proteomes) using the Mascot (version 2.3.02, Matrix Science) search engine. Search parameters were a precursor mass tolerance of 10 ppm for the in-solution digest using the LTQ-Orbitrap Velos and 0.6 Da for the lower resolution LTQ instrument. Fragment mass tolerance was 0.6 Da for both instruments. One missed cleavage was permitted, carbamidomethylation was set as a fixed modification and oxidation (M) was included as a variable modification. For in-solution data, the false discovery rate was <1%, and individual ion scores >30 were considered to indicate identity or extensive homology (p <0.05 ). Results: Overall, over 200 proteins were identified, several of those containing Chitin Binding Domains (CBD), a signature of insect PM proteins, including novel peritrophins and peritrophin-like glycoproteins, which are essential in maintaining PM architecture and may act as trypanosome adhesins. Furthermore, a minimum of 27 proteins were also identified from the tsetse secondary endosymbiont, Sodalis glossinidius, suggesting this bacterium is probably in close association with the tsetse PM. Conclusion: To our knowledge this is the first report on the protein composition of G. m. morsitans, an important vector of African trypanosomes. Further functional analyses of these proteins will lead to a better understanding of the tsetse physiology as well as to identification of potential targets to block trypanosome development within the tsetse.

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