Navegando por Palavras-chave "GPI"

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    CHARACTERIZATION OF A PHOSPHOLIPASE C-RESISTANT INOSITOL CONTAINING GLYCOLIPID FROM TRYPANOSOMA-CRUZI
    (Assoc Bras Divulg Cientifica, 1994-02-01) Heise, Norton [UNIFESP]; Raper, J.; Cardosodealmeida, M. L.; JOHNS HOPKINS UNIV; Universidade Federal de São Paulo (UNIFESP)
    Since glycosylphosphatidylinositol is the most common form of attachment of proteins to membranes in T. cruzi, and that this parasite depends on surface-mediated interactions for survival within the vector and mammalian host, it is probable that a drug which interfers with the metabolism of glycosylphosphatidylinositol (GPI) could be successfully employed in chemotherapy. Over the last few years several groups have been characterizing this mode of attachment in T. cruzi and more recently we have been concentrating our efforts on the identification of candidate precursors for protein anchors in metacyclic trypomastigotes. Previously detected GPI heterogeneity regarding solubilization of a major stage-specific antigen (1G7-Ag) by phospholipase C led us to investigate whether biosynthetic precursors with similar properties could also be identified. Two glycolipid species whose migration properties resemble glycolipids A and C of T. brucei were amenable to biosynthetic radiolabelling with palmitic acid, inositol, ethanolamine, glucosamine and mannose. Following purification,these species were submitted to classical GPI diagnostic treatments. In both cases digestion with GPI-specific phospholipase D (GPIPLD) produced phospatidic acid and treatment with either mild base or phospholipase A(2) (PLA(2)) produced free fatty acid, indicating an acylation at least at position 2 of the glycerol. The glycolipid A-like species proved to be susceptible to solubilization by PIPLC of B. thuringiensis and by GPIPLC of T. brucei and the glycolipid C-like material proved to be fully resistant to both lipases. Although the glycolipid A-like species indeed presents these and other properties compatible with a precursor for the chemically characterized 1 G7-Ag anchor, the PLC-resistant species which is completely insensitive to nitrous acid deamination might be an exception to the general finding of a non-acetylated glucosamine in the GPI moieties so far described.
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    FURTHER CHARACTERIZATION OF THE ACIDIC GPI-HYDROLYZING PHOSPHOLIPASE PRESENT IN HUMAN SERA
    (Assoc Bras Divulg Cientifica, 1994-02-01) Stambuk, Boris Juan Carlos Ugarte [UNIFESP]; Cardosodealmeida, M. L.; Universidade Federal de São Paulo (UNIFESP)
    A phospholipase from human serum capable of hydrolyzing glycosylphosphatidylinositol membrane anchors was described and partially characterized by our group some years ago. This activity presented a pH optimum between 5.0 and 6.0 and was inhibited by EDTA, EGTA and 1,10-phenanthroline. Partial purification showed that the enzyme was a glycoprotein with an apparent molecular weight of 140 kDa as judged by gel filtration. Other investigators characterized at the same time a phospholipase D with similar properties but with a pH optimum near 7.5. We now confirm that the human serum enzyme is indeed a phospholipase D capable of hydrolyzing mfVSG and glycolipids A and C from T. brucei. Isoelectric focusing of whole sera suggests the presence of two isoforms, one with a pi of 4.7 which was the form previously purified by our group, and others with pI from 6.2 to 7.4.
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    The mucin-like glycoprotein super-family of Trypanosoma cruzi: structure and biological roles
    (Elsevier B.V., 2001-05-01) Serrano, Alvaro Acosta; Almeida, Igor Correia de [UNIFESP]; Freitas Junior, Lucio Holanda Gondim de [UNIFESP]; Yoshida, Nobuko [UNIFESP]; Schenkman, Sergio [UNIFESP]; Johns Hopkins Univ; Universidade de São Paulo (USP); Universidade Federal de São Paulo (UNIFESP)
    Trypanosoma cruzi expresses at its surface large amounts of mucin-like glycoproteins. the T. cruzi mucins (TcMUC), a group of highly glycosylated GPI-anchored proteins rich in Thr, Ser, and Pro residues, are expressed in high copy numbers in both insect and mammalian stages of the parasite. These molecules are encoded by a multigene family and contain a unique type of glycosylation consisting of several sialylated O-glycans linked to the protein backbone via Nw-acetylglucosamine residues. the TcMUC are important because of their role in host cell invasion and the ability to induce secretion of proinflammatory cytokines and nitric oxide in activated macrophages. the TcMUC are also significant in being the major substrate for the cell surface trans-sialidase. in this review, we summarize the recent knowledge on the molecular structure and function of this family of T. cruzi glycoproteins. (C) 2001 Elsevier Science B.V. All rights reserved.
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    Phosphatidylinositol-specific phospholipase C (PI-PLC) cleavage of GPI-anchored surface molecules of Trypanosoma cruzi triggers in vitro morphological reorganization of trypomastigotes
    (Soc Protozoologists, 2001-01-01) Mortara, R. A.; Minelli, LMS; Vandekerchove, F.; Nussenzweig, V; Ramalho-Pinto, F. J.; Universidade Federal de São Paulo (UNIFESP); Universidade de São Paulo (USP); NYU Med Ctr
    Trypanosoma cruzi trypomastigotes treated with phosphatidylinositol-specific phospholipase C (PI-PLC) in vitro are rapidly induced to differentiate into round forms. Using confocal microscopy, we were able to show that trypomastigotes treated with PI-PLC initiate the process of flagellum remodeling by 30 sec after contact with the enzyme and amastigote-like forms are detected as early as 10 min after PI-PLC treatment. Scanning and transmission electron microscopy indicate that trypomastigotes undergo a previously undescribed process of flagellum circularization and internalization. Analysis of the flagellar complex with monoclonal antibody 4D9 shows heterogeneous labeling among the parasites, suggesting a remodeling of these molecules. After PI-PLC treatment, parasites rapidly lose the surface marker Ssp-3 and 24 h post-treatment they begin to exhibit a circular nucleus and a rod-shaped kinetoplast. By flow cytometry analysis and confocal microscopy, the Ssp-4 amastigote-specific epitope can be detected on the parasite surface. This indicates that thr release of trypomastigote GPI-anchored molecules by exogenous PI-PLC in vitro can trigger morphological changes.