Differential expression of cruzipain- and gp63-like molecules in the phytoflagellate trypanosomatid Phytomonas serpens induced by exogenous proteins

Phytomonas serpens synthesizes metallo- and cysteine-proteases that are related to gp63 and cruzipain, respectively, two virulence factors produced by pathogenic trypanosomatids. Here, we described the cellular distribution of gp63- and cruzipain-like molecules in P. serpens through immunocytochemistry and confocal fluorescence microscopy. Both proteases were detected in distinct cellular compartments, presenting co-localization in membrane domains and intracellular regions. Subsequently, we showed that exogenous proteins modulated the production of both protease classes, but in different ways. Regarding the metalloprotease, only fetal bovine serum (FBS) influenced the gp63 expression, reducing its surface exposition (≈30%). Conversely, the cruzipain-like molecule was differentially modulated according to the proteins: human and bovine albumins reduced its expression around 50% and 35%, respectively; mucin and FBS did not alter its production, while IgG and hemoglobin drastically enhanced its surface exposition around 7- and 11-fold, respectively. Additionally, hemoglobin induced an augmentation in the cell-associated cruzipain-like activity in a dose-dependent manner. A twofold increase of the secreted cruzipain-like protein was detected after parasite incubation with 1% hemoglobin compared to the parasites incubated in PBS-glucose. The results showed the ability of P. serpens in modulating the expression and the activity of proteolytic enzymes after exposition to exogenous proteins, with emphasis in its cruzipain-like molecules.