.6 A8¦Á-mannosidase Expression On Jurkat Cell Adhesion

Glycosylation of protein plays important roles in the function of cells. In thislaboratory, a cDNA (6A8) encoding a new humanα-mannosidase has been isolated. It hasbeen previously found that biological activities are affected by the inhibition of 6A8α-mannosidase expression in the cells studied including Jurkat cell. In this study, cell massformation in the Jurkat cells with inhibition of 6A8α-mannosidase expression (AS cell)was observed. It suggested an enhancement of adhesion among the AS cells. In order tofind clues for studying the mechanisms, mRNA differential display analysis was performedbetween AS cell and a control M cell (the Jurkat cell-tranduced with a mock) on a DNAchip containing 440 genes including those encoding a number of adhesion and immunemolecules. Nineteen genes were found to be up-regulated and 20 genes be down-regulated.The genes which were up-regulated included CD11a, CD54, CD82, CD24, CD11c, intgrinα-7, CD103, TNFSF9, IL-1R and IL-2Rγ. They were related to cell-cell adhesion. The datafrom DNA chip study were confirmed by the RT-PCR and the immunofluorescencestaining analysis. Among the genes mentioned, CD54 and CD11a are the most important.Thus, this study concentrated on the role played by them in the adhesion enhancementamong AS cells. In comparing to the controls, the wild-type cell (W) and the M cell, AScell showed an enhancement of adhesion to the plate coated with CD54 molecules. Inaddition, the blocking CD11a antibody could block the adhesion and the adhesion amongthe Jurkat cells. These data demonstrated the role played by the enhancement of CD54 andCD11a expression in the adhesion enhancement among AS cells. In addition, an increase ofaffinity in CD11a molecule was also observed in AS cell. Moreover, cytoskeleton in AScell was found to be rearranged. Since cell-cell adhesion is also related to cytoskeleton, itcould be suggested that the rearrangement would play roles in the enhancement of AS celladhesion. Adhesion between heterogeneous cells also plays important roles in life activities, such as immune response etc. Adhesion between AS cell and Raji cell was observed to beenhanced in comparison to that between the control and Raji cell. At the presence of thesuperantigen SEB, immune synapse was formed between Jurkat cell and Raji cell.The function ofα-mannosidase is to trim the mannoses in the N-glycan ofglycoproteins. The high mannose structure in the N-glycan is the receptor of ConA. Thus,ConA binding assay could be used to detect the extent of mannose trimming byα-mannosidase in the N-glycan of glycoproteins. In my study, an enhancement of ConAbinding to the AS cells was observed. Of course, the mechanisms of the effect of thealternation of glycosylation resulted from the inhibition of 6A8α-mannosidase expressionon the adhesiveness of Jurkat cells remains to be discovered in the future.