The core exosome proteome of Trichomonas vaginalis 

Background: Trichomonas vaginalis is an anaerobic parasitic protozoan of the human urogenital tract. Infection can cause vaginitis in women and urethritis in men. Accumulated reports indicated that exosomes released by protozoan parasites play important roles in transmitting information and substances between cells and mediating communication during host-parasite interactions in several parasitic infections. However, current knowledge on the protein contents in T. vaginalis exosome is mainly generated from three previous studies which used different T. vaginalis isolates as an experimental model. Therefore, whether T. vaginalis exosomes comprise a common set of proteins (core exosome proteome) is still unclear. Methods: : To explore the core exosome proteome in T. vaginalis , we used liquid chromatography-tandem mass spectrometry (LC-MS/MS) to identify the contents of sucrose ultracentrifugation-enriched exosome isolated from six isolates. Results: : Transmission electron microscopy (TEM) revealed the presence of exosomes in the enriched fraction with the classical cup-shaped morphology and size around 150 nm. Proteomic analysis identified a total of 1870 proteins from exosomal extracts. There were 1207 exosomal-specific proteins after excluding 436 contaminant proteins. Among these, 72 common exosomal-specific proteins were expressed in all six isolates. Compared with three published T. vaginalis exosome proteome datasets, we identified 16 core exosomal-specific proteins. These core exosomal-specific proteins included tetraspanin (TvTSP1), the classical exosome marker, and proteins mainly involved in catalytic activity and binding such as ribosomal proteins, ras-associated binding (Rab) proteins, and heterotrimeric G proteins. Conclusions: : Our study highlighted the importance of using supernatant fraction from exosomal extract as a control to remove contaminant proteins. In addition, we compiled a reference core exosome proteome of T. vaginalis , which is important for developing a fundamental understanding of exosome-mediated cell communication and host-parasite interaction.