The cytostome of Trypanosoma cruzi epimastigotes is associated with the flagellar complex

Proliferative forms of Trypanosoma cruzi, amastigotes and epimastigoles, ha ve a cytostome, a specialized structure formed by an invagination of the fl agellar pocket's membrane surrounded by microtubules and frequently followe d by a row of vesicles. All this assemblage penetrates deeply into the cyto plasm overpassing the nucleus. This structure, together with the flagellar pocket, appears to play an important role in the nutrition of the parasite. We demonstrated that the monoclonal antibody 2C4, made-up against isolated flagellar complex of T. cruzi epimastigotes, recognizes a protein doublet of 76 and 87 kDa in total epimastigotes homogenate. The 76-kDa polypeptide is enriched in the detergent-soluble fraction whereas the 87-kDa polypeptid e is highly represented in the insoluble fractions and the purified flagell a. Immunofluorescence assays show the antigen as a small spot at the flagel lar pocket region. Immunogold labeling of ultrathin sections of epimastigot e forms reveals gold particles at the opening of flagellar pocket, concentr ated in the cytostome region. Immunocytochemistry of epimastigote whole-mou nt cytoskeletons reveals the labeling on an array of three to four microtub ules that appears attached to flagellum, running in the direction of the nu cleus. Ultrastructural observations have shown that the posterior region of isolated flagella, corresponding to the level of the flagellar pocket, pos sesses a microtubular structure compatible with that from the cytostome. Th e relationship between the cytostome, an endocytic organelle, and the flage llum is here described for the first lime. (C) 1999 Academic Press.