Showing papers by "Shogo Oka published in 1999"

Antitumor activity of mannan-binding protein in vivo as revealed by a virus expression system: Mannan-binding proteindependent cell-mediated cytotoxicity

Abstract: Mannan-binding protein (MBP), a Ca2+-dependent mammalian lectin specific for mannose and N-acetylglucosamine, is an important serum component associated with innate immunity. MBP activates complement and functions as a direct opsonin on binding to mannooligosaccharide-bearing pathogens. We have found that MBP recognizes and binds specifically to oligosaccharide ligands expressed on the surfaces of a human colorectal carcinoma. Interestingly, the recombinant vaccinia virus carrying human MBP gene was demonstrated to possess a potent growth-inhibiting activity against human colorectal carcinoma cells transplanted in KSN nude mice when administered by intratumoral or subcutaneous injection. Moreover, a significant prolongation of life span of tumor-bearing mice resulted from the treatment. This effect appears to be a consequence of local production of MBP. Unexpectedly, the mutant MBP, which had essentially no complement-activating activity, was nearly as active as wild-type MBP. These results indicated that MBP has a previously undescribed cytotoxic activity, which we propose to term MBP-dependent cell-mediated cytotoxicity(MDCC). In addition, this study provides a model for the development of an effective and specific host defense factor for cancer gene therapy.

Characterization of human serum mannan-binding protein promoter.

Abstract: Serum mannan binding protein (MBP), a mannose/N-acetylglusosamine-specific lectin, is important in innate immunity. In order to elucidate the mechanism underlying the wide intra- and interracial variety in the MBP serum level, we have studied the transcriptional regulation of human MBP. Rapid amplification of cDNA ends (5' RACE) analysis of Hep G2 RNA indicated the presence of a novel exon, designated as "exon 0," upstream of previously identified exon 1 [Taylor, M.E. et al. (1989) Biochem. J. 262, 763-771]. Two MBP mRNAs with different sized 5'-noncoding regions were detected: the longer transcript starts at exon 0 and the shorter one at exon 1. Promoter analysis involving a luciferase assay vector revealed that the transcript starting from exon 1 predominates over that starting from exon 0. In addition, a hepatocyto-specific nuclear factor, (HNF)-3, which is known to control the expression of hepatocyto-specific genes, up-regulates the transcription of human MBP from exon 1, while a glucocorticoid, which is known to up-regulate acute phase proteins, markedly suppresses MBP transcription. Recently, polymorphisms were found to occur in the promoter region at two positions [Madsen, H.O. et al. (1995) J. Immunol. 155, 3013-3020]. Functional promoter analysis indicated that three haplotype variants as to these positions, HY, LY, and LX, exhibit high, medium and low promoter activity, respectively, in accordance with the results of a previous population study.

Molecular Biological Approach to Functions of Telencephalin, a Cell Adhesion Molecule and HNK‐1 Carbohydrate Epitope, which Is Commonly Expressed on Cell Adhesion Molecules in the Nervous System

Abstract: Cell surface carbohydrates modulate a variety of cellular functions, including recognition and adhesion. The HNK-1 carbohydrate epitope, which is recognized by the monoclonal antibody HNK-1, is specifically expressed on a series of cell adhesion molecules and also on some glycolipids in the nervous system over a wide range of species from insect to mammal. The HNK-1 epitope is spatially and temporally regulated during the development of the nervous system and associated with neural crest cell migration, neuron to glial cell adhesion, outgrowth of astrocytic processes and migration of cell body, as well as the preferential outgrowth of neurites from motor neurons. These observations together with the unusual chemical nature of the HNK-1 epitope, namely a non-reducing terminal 3-sulfoglucuronic acid residue, prompted us to study the biosynthesis of the NHK-1 epitope, in which a unique glucuronyltransferase(s) plays a key role. We found that the respective glucuronyltransferases are involved in the biosynthesis of the HNK-1 epitope on glycoproteins (GlcAT-P) and on glycolipids (GlcAT-L). Then, we isolated a novel glucuronyltransferase (GlcAT-P) specific for glycoprotein substrates and its cDNA from the rat brain. The primary structure deduced from the cDNA sequence predicted a type II transmembrane protein with 347 amino acids. Transfection of the GlcAT-P cDNA into COS-1 cells induced not only expression of the HNK-1 epitope on the cell surface but also marked morphological changes of the cells, suggesting that the HNK-1 epitope was associated with the cell-substratum interaction. The GlcAT-P cDNA obtained in this study will be a useful molecular tool to open the way for further steps in the elucidation of the biological function of the HNK-1 carbohydrate epitope in the development of the nervous system.