Cell-substrate adhesion during Trypanosoma cruzi differentiation.

Abstract

Abstract. The transformation of Trypanosoma cruziepimastigotes to the mammal infective metacyclic trypomastigotes (metacyclogenesis) can be performed in vitro under chemically defined conditions. Under these conditions, differentiating epimastigotes adhere to a surface before their transformation into metacyclic trypomastigotes. Scanning and transmission electron microscopy of adhered and non-adhered parasites during the metacyclogenesis process show that only epimastigotes and few transition forms are found in the first population, whereas metacyclic trypomastigotes are exclusively found in the cell culture supernatant. PAGE analysis of the pS]methionine metabolic labeling products of adhered and non-adhered parasites shows that although most of the polypeptides are conserved, adhered parasites express specifically four polypeptides in the range of 45-50 kD with an isoelectric point of 4.8. These proteins might be involved in the adhesion process and are recognized by an antiserum against total adhered parasite proteins. This antiserum also recognized a group of 45-50 kD in the iodine-radiolabeled surface proteins of differentiating cells, providing direct evidence that these components are indeed surface antigens. The results suggest that epimastigotes must adhere to a substrate before their transformation to metacyclic trypomastigotes, being released to the medium as the metacyclogenesis process is accomplished. This could correspond to the process naturally occurring within the triatomine invertebrate host.

The surface charge of trypanosomatids

“…Trypomastigotes present a mean EPM of −1.15µm.s −1 .V −1 .cm which is the most negative surface charge compared with the other evolutive forms. As observed for the epimastigote and amastigote forms, the mean EPM of trypomastigotes obtained from the bloodstream of infected mice, from the supernatant of cell cultures, from axenic culture in complex or defined media does not differ significantly , Bonaldo et al 1988. Some results are not in agreement with those reported by Kreier and coworkers (1977) and Murray and coworkers (1982).…”

“…1988). Transitional forms, which have a rodlike kinetoplast localized beside the cell nucleus, presented a mean EPM similar to the trypomastigote forms indicating that during metacyclogenesis, morphological changes are preceded by alterations in some physiological characteristics (Bonaldo et al 1988). The pH of the solution in which the parasites are suspended interferes directly on the mean EPM indicating that the surface of T. cruzi must contain positively and negatively charged dissociating groups.…”

“…Differences in susceptibility of sialic acid residues to distinct neuraminidases were previously described by Tamura and coworkers (1982) and Seaman and Heard (1960) on erythrocytes. For details see Souto-Padrón et al 1984, Carvalho et al 1985, Bonaldo et al 1988, Souto-Padrón et al 1990 Treatment of T. cruzi with trypsin reduces the mean EPM of epimastigote, amastigote and trypomastigote forms by 11, 32 and 35%, respectively, suggesting that sialoglycoproteins contribute to the surface charge of T. cruzi. Neuraminidase and trypsin-treated parasites recover their normal mean EPM when incubated in fresh culture medium for 2 and 4h, respectively.…”

“…Cell surface charge of Trypanosoma cruzi has been analyzed in more detail , Kreier et al 1977, Carvalho et al 1985, Bonaldo et al 1988). The electrophoretic mobility analysis of the different developmental stages of T. cruzi showed that each evolutive form has a characteristic mean EPM which does not vary in the different strains or isolates of the parasite, is independent of the medium in which the cells were grown and do not change after glutaraldehyde fixation (Table II) (Souto-Padrón et al 1990).…”

Trypanosoma cruzi: Maintenance in Culture Modify Gene and Antigenic Expression of Metacyclic Trypomastigotes

“…With this medium, biochemical analysis of metacyclic forms is feasible and indeed has allowed the identification of stage-specific gene expression products, as well as the association between gene products and acquisition of metacyclic-specific trypomastigote biological properties (Contreras et al 1985a,c, Goldenberg et al 1987, Bonaldo et al 1988.…”