Showing papers by "Shogo Oka published in 2008"
TL;DR: A comparison of the N-glycans released from the MBP- binding and non-MBP-binding glycopeptides suggested that complex-type N- glycans carrying a minimum of 4 Le(a)/Le(b) epitopes arranged either as multimeric tandem repeats or terminal epitopes on multiantennary structures are critically important for the high affinity binding to MBP.
Abstract: The serum mannan-binding protein (MBP) is a host defense C-type lectin specific for mannose, N-acetylglucosamine, and fucose residues, and exhibits growth inhibitory activity toward human colorectal carcinoma cells. The MBP-ligand oligosaccharides (MLO) isolated from a human colorectal carcinoma cell line, SW1116, are large, multiantennary N-glycans with highly fucosylated polylactosamine-type structures having Le(b)-Le(a) or tandem repeats of the Le(a) structure at their nonreducing ends. In this study, we isolated the major MBP-ligand glycoproteins from SW1116 cell lysates with an MBP column and identified them as CD26/dipeptidyl peptidase IV (DPPIV) (110 kDa) and CD98 heavy chain (CD98hc)/4F2hc (82 kDa). Glycosidase digestion revealed that CD26 contained such complex-type N-glycans that appear to mediate the MBP binding. MALDI-MS of the N-glycans released from CD26 by PNGase F demonstrated conclusively that CD26 is the major MLO-carrying protein. More interestingly, a comparison of the N-glycans released from the MBP-binding and non-MBP-binding glycopeptides suggested that complex-type N-glycans carrying a minimum of 4 Le(a)/Le(b) epitopes arranged either as multimeric tandem repeats or terminal epitopes on multiantennary structures are critically important for the high affinity binding to MBP. Analysis of the N-glycan attachment sites demonstrated that the high affinity MLO was expressed preferentially at some N-glycosylation sites, but this site preference was not so stringent. Finally, hypothetical 3D models of tandem repeats of the Le(a) epitope and the MBP-Lewis oligosaccharide complex were presented.
33 citations
TL;DR: The interaction between laminin-1 and alpha-dystroglycan through their glycans in mouse kidney using the overlay assay technique obtained evidence that glucuronic acid as well as sialic acid inhibited this interaction, suggesting that the nonsulfated HNK-1 epitope on lamin in-1 may regulate its binding and play a role in maintenance of the proper structure in the kidney basal lamina.
Abstract: The HNK-1 epitope has a unique structure comprising the sulfated trisaccharide (HSO(3)-3GlcAbeta1-3Galbeta1-4GlcNAc), and two glucuronyltransferases (GlcAT-P and GlcAT-S) are key enzymes for its biosynthesis. However, the different functional roles of these enzymes in its biosynthesis remain unclear. Recently, we reported that a nonsulfated form of this epitope, which is biosynthesized by GlcAT-S but not by GlcAT-P, is expressed on two metalloproteases in mouse kidney. In this study, we found that a novel glycoprotein carrying the nonsulfated HNK-1 epitope in mouse kidney was enriched in the nuclear fraction. The protein was affinity-purified and identified as laminin-1, and we also confirmed the N-linked oligosaccharide structure including nonsulfated HNK-1 epitope derived from laminin-1 by mass spectrometry. Curiously, immunofluorescence staining of kidney sections revealed that laminin-1 appeared not to be colocalized with the nonsulfated HNK-1 epitope. However, proteinase treatment strengthened the signals of both laminin-1 and the nonsulfated HNK-1 epitope, resulting in overlapping of them. These results indicate that the nonsulfated HNK-1 epitope on laminin-1 is usually embedded and masked in the robust basement membrane in tight association with other proteins. To clarify the associated proteins and the functional role of the carbohydrate epitope, we investigated the interaction between laminin-1 and alpha-dystroglycan through their glycans in mouse kidney using the overlay assay technique. We obtained evidence that glucuronic acid as well as sialic acid inhibited this interaction, suggesting that the nonsulfated HNK-1 epitope on laminin-1 may regulate its binding and play a role in maintenance of the proper structure in the kidney basal lamina.
15 citations
TL;DR: The HPLC map developed in the present study will be a useful glycomics tool for identification and profiling of glucuronyl N-glycans expressed in the neural and other biological systems.
Abstract: Although the multi-dimensional HPLC maps of neutral, sialyl, and sulfated N-glycans have been reported and widely used for glycosylation profiling, those of glucuronyl oligosaccharides have not yet been available. In the present study, by in vitro enzymatic reactions, we prepared 55 different glucuronyl PA-oligosaccharides that include 6 kinds of HNK-1-containing N-glycans, and established their HPLC map. Furthermore, we applied this map to the characterization of branch specificity in glucuronylation reaction catalyzed by human GlcAT-S, revealing that this enzyme transfers the glucuronyl residues preferentially onto the Gal 1�4GlcNAc 1�4Man 1�3 and Gal 1�4GlcNAc 1�2Man 1�3 branches of a galactose-terminated tri-antennary oligosaccharide. The HPLC map developed in the present study will be a useful glycomics tool for identification and profiling of glucuronyl N-glycans expressed in the neural and other biological systems.
6 citations
01 Jan 2008
TL;DR: The HNK-1 carbohydrate has a very unique structural feature comprising a sulfated trisaccharide, whose biosynthesis is regulated by two glucuronyltranferases (GlcAT-P and Glcat-S).
Abstract: The HNK-1 carbohydrate has a very unique structural feature comprising a sulfated trisaccharide (HSO3-3GlcAβ1-3Galβ1-4GlcNAc-), whose biosynthesis is regulated by two glucuronyltranferases (GlcAT-P and GlcAT-S). The carbohydrate is expressed on a limited number of glycoproteins, such as neural cell adhesion molecule (NCAM), L1, phosphacan and so on, in the nervous system. To elucidate the role of the HNK-1 carbohydrate, we generated and analyzed mice with a targeted deletion of the GlcAT-P gene, which is mainly expressed in the nervous system.
01 Jan 2008
TL;DR: It was revealed that unique carbohydrate epitopes are known to be expressed such as HNK-1 and PSA (polysialic acid), which are rarely found in other organs or tissues and are involved in the formation and maintenance of neural network.
Abstract: In the nervous system, many types of cells recognize each other to form a precise neural network, whereas these cells are morphologically and functionally different. The development and maintenance of this complicated but accurate network involves many molecules. Among them, cell adhesion molecules (CAMs) are considered to play important roles in these processes. On these CAMs in the nervous system, unique carbohydrate epitopes are known to be expressed such as HNK-1 (Human Natural Killer-1, also called CD57) and PSA (polysialic acid), which are rarely found in other organs or tissues. Recently, it was revealed that these unique carbohydrates are involved in the formation and maintenance of neural network.
01 Jan 2008
TL;DR: The monoclonal antibody HNK-1 was raised against the membrane fraction of the human HSB-2 T-cell line and the structure of the H NK-1 epitope was demonstrated to comprise the sulfated trisaccharide HSO3-3GlcAβ1-3Gal β1-4GlcNAc, which is shared by glycolipids and glycoproteins.
Abstract: The monoclonal antibody HNK-1 was raised against the membrane fraction of the human HSB-2 T-cell line. The antigen was originally found to be a marker of human natural killer (HNK) cells and is called as CD57 in immunology. After that, it was found that the HNK-1 carbohydrate epitope is highly expressed in the nervous system, especially on a series of cell adhesion molecules, including neural cell adhesion molecule (NCAM), myelin-associated glycoprotein (MAG), L1, P0, telencephalin, and also some glycolipids. The structure of the HNK-1 epitope was demonstrated to comprise the sulfated trisaccharide HSO3-3GlcAβ1-3Galβ1-4GlcNAc, which is shared by glycolipids and glycoproteins. The expression of the HNK-1 carbohydrate epitope is spatially and temporally regulated during the development of the nervous system, and it functions in cell adhesion, migration, neurite outgrowth and synaptic plasticity (Yamamoto et al. 2002).