Navegando por Palavras-chave "protein kinase C"
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- ItemSomente Metadadadosalpha-Tocopherol modulates tyrosine phosphorylation in human neutrophils by inhibition of protein kinase C activity and activation of tyrosine phosphatases(Taylor & Francis Ltd, 2001-01-01) Chan, S. S.; Monteiro, H. P.; Schindler, F.; Stern, A.; Junqueira, VBC; Universidade Federal de São Paulo (UNIFESP); Universidade de São Paulo (USP); Fdn Pro Sangue; NYUalpha-Tocopherol augmentation in human neutrophils was investigated for effects on neutrophil activation and tyrosine phosphorylation of proteins, through its modulation of protein kinase C (PKC) and tyrosine phosphatase activities. Incubation of neutrophils with alpha-tocopherol succinate (TS) resulted in a dose-dependent incorporation into cell membranes, up to 2.5 nmol/2 X 10(6) cells. A saturating dose of TS (40 mumol/l) inhibited oxidant production by neutrophils stimulated with phorbol myristate acetate (PMA) or opsonized zymosan (OZ) by 86 and 57%, as measured by luminol-amplified chemiluminescence (CL). With PMA, TS inhibited CL generation to a similar extent to staurosporine (10 nmol/l) or genistein (100 mumol/l), and much more than Trolox (40 mumol/l). With OZ, TS inhibited CL to a similar extent to Trolox. Neutrophil PKC activity was inhibited 50% or more by TS or staurosporine. the enzyme activity was unaffected by genistein or Trolox, indicating a specific interaction of alpha-tocopherol. TS or Trolox increased protein tyrosine phosphorylation in resting neutrophils, and as with staurosporine further increased tyrosine phosphorylation in PMA-stimulated neutrophils, while the tyrosine kinase (TK) inhibitor genistein diminished phosphorylation. These effects in resting or PMA-stimulated neutrophils were unrelated to protein tyrosine phosphatase (PTP) activities, which were maintained or increased by TS or Trolox. in OZ-stimulated neutrophils, on the other hand, all four compounds inhibited the increase in tyrosine-phosphorylated proteins. in this case, the effects of pre-incubation with TS or Trolox corresponded with partial inhibition of the marked (85%) decrease in PTP activity induced by OZ. These results indicate that alpha-tocopherol inhibits PMA-activation of human neutrophils by inhibition of PKC activity, and inhibits tyrosine phosphorylation and activation of OZ-stimulated neutrophils also through inhibition of phosphatase inactivation.
- ItemSomente MetadadadosSmPKC1, a new protein kinase C identified in the platyhelminth parasite Schistosoma mansoni(Elsevier B.V., 2006-07-07) Bahia, Diana; Avelar, Livia; Mortara, Renato A.; Khayath, Naji; Yan, Yutao; Noel, Christophe; Capron, Monique; Dissous, Colette; Pierce, Raymond J.; Oliveira, Guilherme; Inst Pasteur; Fiocruz MS; Universidade Federal de São Paulo (UNIFESP); Newcastle Univ; Santa Casa Misericordia Belo HorizonteSchistosoma mansoni signal transduction pathways are promising sources of target molecules for the development of novel control strategies against this platyhelminth parasite of humans. Members of the protein kinase C (PKC) family play key roles in such pathways activated by both receptor tyrosine kinases and other receptors, controlling a variety of physiological processes. Here, we report the cloning and molecular characterization of the first PKC identified in S. mansoni. Structural analysis indicated that SmPKC1 exhibits all the features typical of the conventional PKC subfamily. the gene structure was determined in silico and found to comprise a total of 15 exons and 14 introns. This structure is highly conserved; all intron positions are also present in the human PKC beta gene and most of the exon sizes are identical. Using PCR on genomic DNA we were able to show that putative orthologues of SmPKC1 are present in 9 Schistosoma species. SmPKC1 expression is developmentally regulated with the highest level of transcripts in miracidia, whereas SmPKC1 protein expression is higher in the sporocyst. the localization of SmPKC1 on the sporocyst ridge cyton and in schistosomula acetabular glands suggests that the enzyme plays a role in signal transduction pathways associated with larval transformation. (c) 2006 Elsevier Inc. All rights reserved.
- ItemRestritoSpecific structural features of syndecans and heparan sulfate chains are needed for cell signaling(Assoc Bras Divulg Cientifica, 2006-02-01) Lopes, Carla Cristina [UNIFESP]; Dietrich, Carl Peter [UNIFESP]; Nader, Helena Bonciani [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)The syndecans, heparan sulfate proteoglycans, are abundant molecules associated with the cell surface and extracellular matrix and consist of a protein core to which heparan sulfate chains are covalently attached. Each of the syndecan core proteins has a short cytoplasmic domain that binds cytosolic regulatory factors. the syndecans also contain highly conserved transmembrane domains and extracellular domains for which important activities are becoming known. These protein domains locate the syndecan on cell surface sites during development and tumor formation where they interact with other receptors to regulate signaling and cytoskeletal organization. the functions of cell surface heparan sulfate proteoglycan have been centered on the role of heparan sulfate chains, located on the outer side of the cell surface, in the binding of a wide array of ligands, including extracellular matrix proteins and soluble growth factors. More recently, the core proteins of the syndecan family transmembrane proteoglycans have also been shown to be involved in cell signaling through interaction with integrins and tyrosine kinase receptors.