Studies on Sugar Recognition by Animal Lectins

点击翻译按钮获取中文摘要

Serum mannan-binding protein (MBP) is a C-type lectin which binds to sugar chains terminated with mannose or N-acetylglucosamine residue. Once MBP binds to ligand sugars on a solid support such as bacterial cells, it activates complement through a new pathway called "lectin pathway". The physiological significance of this lectin was demonstrated clearly by the finding that the patients deficient of the lectin in their serum suffer from serious infectious diseases. In the past one year, we have studied the mechanism of the expression of MBP mRNA by analyzing promoter activity of the 5' upstream region of human MBP gene. 5' upstream region gene fragment -845/+69, which contains several consensus sequences in addition to basic promoter elements CAAT and TATA boxes, was inserted into reporter plasmid containing luciferase gene. The resultant construct was transfected into Hep G2 cells, which was shown to express MBP mRNA.Treatment of the transfected cells with cytokines such as IL6, TNF-a, INF-g and PMA (phorbol 12-myristate 13-acetate) did not show any significant effects on the level of expression of luciferase, while dexamethasone inhibited the expression to one half the control level. Step wise deletions of the MBP gene from 5' upstream region resulted in the up and down regulation of the expression suggesting the presence of multiple negative and positive regulatory elements in this promoter regions.