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Trypanosoma cruzi, the etiological agent of the Chagas' disease in Latin America undergoes a complex life cycle involving two hosts, a mammalian host and a reduviid insect vector (triatomine). In the insect midgut the parasite multiplies as epimastigote forms, which rely on endocytosis for their energy requirement. We recently showed that posttranslational modification of endocytic N-glycoproteins by tomato lectin (TL) binding-N-glycans is crucial for receptor-mediated endocytosis (RME) in epimastigote forms. In an attempt to characterize the endocytic proteome we used a TL affinity chromatography, which significantly enriched glycoproteins of the trypanosomal endocytic pathway. In addition to various lysosomal hydrolases, we found an endosomal C-type lectin-like protein, which displays some structural and topological characteristics of the mammalian lectin receptor superfamily. This lectin encoding a large transmembrane protein of around 375kDa contained three putative extracellular N-terminal C-type lectin domains (CTLD) and located inside the flagellar pocket (FP)/cytostome and endosomal compartments of the insect stage of the parasite and on the surface of the plasma membrane of intracellular amastigote parasites. Noteworthy, this endogenous lectin displayed similar sugar-binding specificity to that of TL and therefore could be important in either the N-glycan mediated endocytosis or parasite adhesion to host cells. We postulated that during the evolution of trypanosomatids, genes encoding lectin harboring 3 CTDLs represent an old acquisition present in free-living, monoxenic and heteroxenic trypanosomatids, which would have been secondarily lost in extracellular parasites from the T. brucei clade., (Copyright © 2017 Elsevier GmbH. All rights reserved.)

The Trypanosoma cruzi adenylyl cyclase (AC) multigene family encodes different isoforms (around 15) sharing a variable large N-terminal domain, which is extracellular and receptor-like, followed by a transmembrane helix and a conserved C-terminal catalytic domain. It was proposed that these key enzymes in the cAMP signalling pathway allow the parasite to sense its changing extracellular milieu in order to rapidly adapt to its new environment, which is generally achieved through a differentiation process. One of the critical differentiation events the parasitic protozoan T. cruzi undergoes during its life cycle, known as metacyclogenesis, occurs in the digestive tract of the insect and corresponds to the differentiation from noninfective epimastigotes to infective metacyclic trypomastigote forms. By in vitro monitoring the activity of AC during metacyclogenesis, we showed that both the activity of AC and the intracellular cAMP content follow a similar pattern of transient stimulation in a two-step process, with a first activation peak occurring during the first hours of nutritional stress and a second peak between 6 and 48 h, corresponding to the cellular adhesion. During this differentiation process, a general mechanism of upregulation of AC expression of both mRNA and protein is triggered and in particular for a major subclass of these enzymes that are present in various gene copies commonly associated to the THT gene clusters. Although the scattered genome distribution of these gene copies is rather unusual in trypanosomatids and seems to be a recent acquisition in the evolution of the T. cruzi clade, their encoded product redistributed on the flagellum of the parasite upon differentiation could be important to sense the extracellular milieu., (Copyright © 2015 Elsevier B.V. All rights reserved.)