Expressão de glicanos e seu envolvimento com a perda da estabilidade das junções aderentes em células de câncer colo-retal

• Autor(a) principal: Freitas Junior, Julio Cesar Madureira de
• Data de Publicação: 2009
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/7810
• topic: Colorectal cancer; Adherent junctions; Glycobiology; E-cadherin; Câncer colo-retal; Junções Aderentes; Glicobiologia; E-caderina; Neoplasias colorretais; Glicoproteínas; CNPQ::CIENCIAS BIOLOGICAS::MORFOLOGIA::CITOLOGIA E BIOLOGIA CELULAR

The adherent junction (AJ) is one of the main components of the apical junctional complex. It is a multiprotein complex where E-cadherin, a transmembrane glycoprotein, acts as the main mediator of cell-cell adhesion in epithelium. This protein is anchored to the actin cytoskeleton via proteins of the catenin family. Posttranslational modifications of E-cadherin, such as phosphorylation and glycosylation, can modulate the assembly of AJs. Various studies have suggested that invasion and metastasis is associated to glycan patterns on the cell surface of tumor cells. In colorectal cancer the role of altered glycans expression and stability of E-cadherin-mediated adhesion is not clear. In this study we investigated the relation between changes of the glycans expression and AJs stability in colorectal cancer cells. We used two colon adenocarcinoma cell lines with different metastatic potential, Caco-2 and HCT-116, both models of stable and unstable AJs, respectively. Lectin binding assays demonstrated that in HCT-116, the more invasive cell line, E-cadherin presents a decrease of the glycans recognized by HPA and WGA lectins, which recognize N-acetylgalactosamine and, _-N-acetylhexosamines and sialic acid, respectively. Conversely, in HCT-116, there was an increase of glycans recognized by E-PHA and L-PHA lectins, which recognize bisecting _1,4- branched and _1,6-branched N-acetylglucosamine, respectively. Immunofluorescence assays showed a stronger L-PHA binding on cell-cell contact regions of HCT-116 cells when compared with Caco-2. Furthermore, in HCT-116 cells a complete inhibition of N-glycosylation by tunicamycin or inhibition of complex N-glycans synthesis by swainsonine increased the association of E-cadherin with the actin cytoskeleton. Finally, it was possible to observe that the inhibition of N-linked glycosylation by tunicamycin, leaded to a decreasing of ERK1/2 phosphorylation concomitantly with the formation of more intimate cell-cell contacts. These findings suggest that altered expression and subcellular localization of different glycans can be important events associated to loss of AJs stability in colorectal cancer.