Trichomonas vaginalis is a sexually transmitted anaerobic parasite that infects humans causing trichomoniasis, a common and ubiquitous sexually transmitted disease. The life cycle of this parasite possesses a trophozoite form without a cystic stage. However, the presence of nonproliferative and nonmotile, yet viable and reversible spherical forms with internalized flagella, denominated pseudocysts, has been commonly observed for this parasite. To understand the mechanisms involved in the formation of pseudocysts, we performed a mass spectrometry-based high-throughput quantitative proteomics study using a label-free approach and functional assays by biochemical and flow cytometric methods. We observed that the morphological transformation of trophozoite to pseudocysts is coupled to (i) a metabolic shift toward a less glycolytic phenotype; (ii) alterations in the abundance of hydrogenosomal iron–sulfur cluster (ISC) assembly machinery; (iii) increased abundance of regulatory particles of the ubiquitin–proteasome system; (iv) significant alterations in proteins involved in adhesion and cytoskeleton reorganization; and (v) arrest in G2/M phase associated with alterations in the abundance of regulatory proteins of the cell cycle. These data demonstrate that pseudocysts experience important physiological and structural alterations for survival under unfavorable environmental conditions.

BackgroundAedes albopictus is widely distributed across tropical and sub-tropical regions and is associated with the transmission of several arboviruses. Although this species is increasingly relevant to public health due its ability to successfully colonize both urban and rural habitats, favoring the dispersion of viral infections, little is known about its biochemical traits, with all assumptions made based on studies of A. aegypti. In previous studies we characterized the peptidase profile of pre-imaginal stages of A. albopictus and we reported the first proteomic analysis of the midgut from sugar-fed females of this insect species.MethodsIn the present work, we further analyzed the peptidase expression in the midgut of sugar-fed females using 1DE-substrate gel zymography, two-dimensional electrophoresis (2DE), mass spectrometry (MS), and protein identification based on similarity.ResultsThe combination of zymography, in solution assays using fluorescent substrates and 2DE-MS/MS allowed us to identify the active serine peptidase “fingerprint” in the midgut of A. albopictus females. Zymographic analysis revealed a proteolytic profile composed of at least 13 bands ranging from ~25 to 250 kDa, which were identified as trypsin-like serine peptidases by using specific inhibitors of this class of enzymes. Concomitant use of the fluorogenic substrate Z-Phe-Arg-AMC and trypsin-like serine protease inhibitors corroborated the zymographic findings. Our proteomic approach allowed the identification of two different trypsin-like serine peptidases and one chymotrypsin in protein spots of the alkaline region in 2DE map of the A. albopictus female midgut. Identification of these protein coding genes was achieved by similarity to the A. aegypti genome sequences using Mascot and OMSSA search engines.ConclusionThese results allowed us to detect, identify and characterize the expression of active trypsin-like serine peptidases in the midgut of sugar-fed A. albopictus females. In addition, proteomic analysis allowed us to confidently assign the expression of two trypsin genes and one chymotrypsin gene to the midgut of this mosquito. These results contribute to the gene annotation in this species of unknown genome and represent a small but important step toward the protein-level functional and localization assignment of trypsin-like serine peptidase genes in the Aedes genus.