A novel 4-methylumbelliferyl-beta-D-xyloside derivative, sulfate-O-3-xylosylbeta1-(4-methylumbelliferone), isolated from culture medium of human skin fibroblasts, and its role in methylumbelliferone-initiated glycosaminoglycan biosynthesis

HNK-1-Reactive oligosaccharide, sulfate-O-3GlcAbeta1-4Xylbeta1-MU, synthesized by cultured human colorectal cancer cells

Human colorectal cancer cells were incubated with medium containing 4-methylumbelliferyl-beta-D-xyloside (Xyl-MU). The cells synthesized Xyl-MU-derivatives which were detected in the culture medium by gel-filtration high-performance liquid chromatography. These included a Xyl-MU-induced glycosaminoglycan and its biosynthetic intermediates, Galbeta1-4Xylbeta1-MU and Galbeta1-3Galbeta1-4Xylbeta1-MU, and other Xyl-MU-induced oligosaccharides, not related to Xyl-MU-induced glycosaminoglycan, were also synthesized. One of these oligosaccharides, sulfate-O-3GlcAbeta1-4Xylbeta1-MU, reacted with HNK-1, a mouse monoclonal antibody raised against human natural killer cells. Human neural cells and skin fibroblasts have also been reported to synthesize HNK-1-reactive sugar chains. Since HNK-1-reactive sugar chains are known to be involved in cell adhesion in the nervous system, the present results suggest that epithelium-derived colorectal cancer cells might also be able to utilize them in cell adhesion.

4-Methylumbelliferone induces the expression of membrane type 1-matrix metalloproteinase in cultured human skin fibroblasts

Human skin fibroblasts were cultured in the presence of 4-methylumbelliferone, an inhibitor of hyaluronan synthesis. Gelatinolytic activity excreted in the medium was examined by zymography and gelatinase assay using a fluorogenic substrate. 4-Methylumbelliferone added to the medium activated the latent form of matrix metalloproteinase-2 in a dose- and time-dependent manner. Immunoblot analysis also showed the conversion of the latent form of matrix metalloproteinase-2 to its active form. This activation was observed even when the cells were cultured with both 4-methylumbelliferone and hyaluronan. Addition of Streptomyces hyaluronidase to the medium during cultivation did not activate the latent form of matrix metalloproteinase-2. Reverse transcription-polymerase chain reaction revealed that 4-methylumbelliferone markedly increased the level of mRNA for membrane type 1-matrix metalloproteinase, whereas levels of mRNA for matrix metalloproteinase-2 and tissue inhibitor of metalloproteinase-2 were little affected. These results suggest that 4-methylumbelliferone induces the expression of membrane type 1-matrix metalloproteinase, resulting in activation of matrix metalloproteinase-2, in cultured human skin fibroblasts.

The mechanism of cell death in human cultured colon adenocarcinoma cell line COLO 201 induced by beta-D-N-acetylglucosaminyl-p-nitrophenol

COLO 201, human colon adenocarcinoma cells were incubated with artificial primers, p-nitrophenyl-glycoside derivatives at 1.0 mmol (mM) in the medium containing 10% fetal bovine serum to detect sugar chain elongation. However, when p-nitrophenyl-beta-N-acetylglucosamine (beta-GlcNAc-PNP) was added, the medium changed color to yellow and the cells were dead. To explain this finding, the cells were incubated with 1.0 mM each of beta-GlcNAc-PNP and 4-methylumbelliferyl-beta-N-acetylglucosamine, then the number of living cells was measured in a time course. In beta-GlcNAc-PNP, the living cells were decreased at 24 hours. The cells were survived with N-acetylglucosamine, whereas in the presence of p-nitrophenol (PNP) the living cells were decreased. It was suggested that PNP released from beta-GlcNAc-PNP induced the cell death. Activity of beta-D-N-acetylglucosaminidase was detected in fetal bovine serum. It was shown that PNP induced the cell death in time-and-dose dependent manner. Genomic DNA from COLO 201 analyzed by agarose gel electrophoresis was fragmentated. PNP analogues were tested for toxicity, and the results suggested that the phenolic OH-group linked to benzene ring and nitro-group linked to the structure in para-form (PNP) was the most effective.

Effects of ATP on regulation of galactosyltransferase-I activity responsible for synthesis of the linkage region between the core protein and glycosaminoglycan chains of proteoglycans

We report that ATP enhances the activity of galactosyltransferase-I, which synthesizes the linkage region between glycosaminoglycan chains and the core proteins of proteoglycans. The enzyme activity in cell-free fractions prepared from cultured human skin fibroblasts was measured by high-performance liquid chromatographic detection of galactosyl-xylosyl-(4-methylumbelliferone) produced from 4-methylumbelliferyl-β-D-xyloside used as an acceptor. ATP at 2 mM increased the enzyme activity by about 60% in the 110 × g supernatant of the cell homogenate, but not in the supernatant or precipitate fractions obtained by 100 000 × g centrifugation. When both fractions (the 100 000 × g supernatant and precipitate) were mixed, the additional ATP increased the enzyme activity. This increase was canceled by heat treatment or trypsin digestion of the 100 000 × g supernatant. In addition, the 100 000 × g precipitate, which was prepared from the 110 × g supernatant preincubated with ATP, exhibited increased activity, and this increase was abolished by alkaline phosphatase treatment. These results suggest that a protein kinase in the 100 000 × g supernatant activates galactosyltransferase-I activity.Key words: ATP, enzyme activator, galactosyltransferase-I, proteoglycan linkage region.