RESUMO
Trypanosoma cruzi, the protozoa that causes Chagas disease in humans, is transmitted by insects from the Reduviidae family. The parasite has developed the ability to change the structure of the surface molecules, depending on the host. Among them, the mucins are the most abundant glycoproteins. Structural studies have focused on the epimastigotes and metacyclic trypomastigotes that colonize the insect, and on the mammal trypomastigotes. The carbohydrate in the mucins fulfills crucial functions, the most important of which being the accepting of sialic acid from the host, a process catalyzed by the unique parasite trans-sialidase. The sialylation of the parasite influences the immune response on infection. The O-linked sugars have characteristics that differentiate them from human mucins. One of them is the linkage to the polypeptide chain by the hexosamine, GlcNAc, instead of GalNAc. The main monosaccharide in the mucins oligosaccharides is galactose, and this may be present in three configurations. Whereas ß-d-galactopyranose (ß-Galp) was found in the insect and the human stages of Trypanosoma cruzi, ß-d-galactofuranose (ß-Galf) is present only in the mucins of some strains of epimastigotes and α-d-galactopyranose (α-Galp) characterizes the mucins of the bloodstream trypomastigotes. The two last configurations confer high antigenic properties. In this review we discuss the different structures found and we pose the questions that still need investigation on the exchange of the configurations of galactose.
Assuntos
Doença de Chagas/parasitologia , Mucinas , Oligossacarídeos/química , Trypanosoma cruzi , Configuração de Carboidratos , Sequência de Carboidratos , Galactose/química , Interações Hospedeiro-Parasita , Humanos , Mucinas/química , Mucinas/imunologia , Ácido N-Acetilneuramínico/química , Trypanosoma cruzi/imunologia , Trypanosoma cruzi/fisiologiaRESUMO
Trypomastigote forms of Trypanosoma cruzi were metabolically labeled with [14C]-ethanolamine and [3H]-palmitic acid. Lipids shed to the culture medium were analyzed and compared with the parasite components. Phosphatidylcholine and lysophosphatidylcholine accounted for 53 per cent of the total incorporated precursor. Interestingly, phosphatidylethanolamine and its lyso derivative lysophosphatidylethanolamine, although present in significant amounts in the parasites, could not be detected in the shed material. Shed lipids were highly enriched in the desaturated fatty acids C16:1 and C18:1 when compared to the total fatty acid pool isolated from the parasites.
Assuntos
Animais , Lipídeos/análise , Trypanosoma cruzi/química , Cromatografia em Camada Fina , Meios de Cultura , Etanolaminas , Ácidos Graxos não Esterificados/análise , Ácidos Graxos Insaturados/análise , Lisofosfatidilcolinas/análise , Ácido Palmítico , Fosfatidilcolinas/análise , Trypanosoma cruzi/metabolismoRESUMO
The glycoconjugate profiles of epimastigotes of the Y strain and of two stocks of the tulahuen strain which differ in their infectivity have been compared. The surface location of the glycoconjugates was evidenced by labelling with glactose oxidase/NaB3H4. Fluorography of SDS-polyacrylamide gel electrophoresis showed a different pattern in the glycoprotein range for both strains and also for two lines (T0 and T2) of the Tulahuen strain. While T0 showed only one glycoprotein with Mr 45 kDa, T2 revealed three glycoproteins in the range of 25-57 kDa. Two fast components, corresponding to glycolipids were also shown. The glycoproteins were isolated with 44 percent phenol and they were purified from the aqueous phase. Alkaline borohydride treatment of the labelled glycoproteins under the conditions of beta-elimination released strongly labelled O-glycosidically linked oligosaccharides. These O-linked glycans are not of the usual type found in glycoproteins. N-acetylgalactosamine which links O-glycans to the protein in the known mucin type glycoproteins has not been detected in the T. cruzi glycoproteins (1).