The Experts below are selected from a list of 8166 Experts worldwide ranked by ideXlab platform
Kurt Drickamer - One of the best experts on this subject based on the ideXlab platform.
-
Mechanism of ligand Binding to E- and P-selectin analyzed using selectin/Mannose-Binding Protein chimeras.
The Journal of biological chemistry, 1998Co-Authors: Dawn Torgersen, Nicholas P. Mullin, Kurt DrickamerAbstract:Abstract The mechanism of oligosaccharide Binding to the selectin cell adhesion molecules has been analyzed by transferring regions of the carbohydrate-recognition domains of E- and P-selectin into corresponding sites in the homologous rat serum Mannose-Binding Protein. Insertion of two basic regions and an adjacent glutamic acid residue leads to efficient Binding of HL-60 cells and sialyl-Lewisx-conjugated serum albumin. Substitution of glycine for a histidine residue known to stabilize Mannose in the Binding site of wild type Mannose-Binding Protein results in dramatic loss of affinity for Mannose without decreasing Binding to sialyl-Lewisx. The accumulated effect of these changes is to alter the ligand Binding selectivity of the domain so that it resembles E- or P-selectin more closely than it resembles the parental Mannose-Binding domain. Affinity labeling using sialyl-Lewisx in which the sialic acid has been mildly oxidized has been used to verify this switch in specificity and to show that the sialic acid-containing portion of the ligand interacts near the sequence Lys-Lys-Lys corresponding to residues 111–113 of E-selectin. The Binding of sialyl-Lewisx-serum albumin is inhibited dramatically at physiological and higher salt concentrations, consistent with a significant electrostatic component to the Binding interaction. The Binding characteristics of these gain-of-function chimeras suggest that they contain many of the selectin residues responsible for selective ligand Binding.
-
mechanism of ligand Binding to e and p selectin analyzed using selectin Mannose Binding Protein chimeras
Journal of Biological Chemistry, 1998Co-Authors: Dawn Torgersen, Nicholas P. Mullin, Kurt DrickamerAbstract:Abstract The mechanism of oligosaccharide Binding to the selectin cell adhesion molecules has been analyzed by transferring regions of the carbohydrate-recognition domains of E- and P-selectin into corresponding sites in the homologous rat serum Mannose-Binding Protein. Insertion of two basic regions and an adjacent glutamic acid residue leads to efficient Binding of HL-60 cells and sialyl-Lewisx-conjugated serum albumin. Substitution of glycine for a histidine residue known to stabilize Mannose in the Binding site of wild type Mannose-Binding Protein results in dramatic loss of affinity for Mannose without decreasing Binding to sialyl-Lewisx. The accumulated effect of these changes is to alter the ligand Binding selectivity of the domain so that it resembles E- or P-selectin more closely than it resembles the parental Mannose-Binding domain. Affinity labeling using sialyl-Lewisx in which the sialic acid has been mildly oxidized has been used to verify this switch in specificity and to show that the sialic acid-containing portion of the ligand interacts near the sequence Lys-Lys-Lys corresponding to residues 111–113 of E-selectin. The Binding of sialyl-Lewisx-serum albumin is inhibited dramatically at physiological and higher salt concentrations, consistent with a significant electrostatic component to the Binding interaction. The Binding characteristics of these gain-of-function chimeras suggest that they contain many of the selectin residues responsible for selective ligand Binding.
-
asymmetry adjacent to the collagen like domain in rat liver Mannose Binding Protein
Biochemical Journal, 1997Co-Authors: Russell Wallis, Kurt DrickamerAbstract:Rat liver Mannose-Binding Protein (MBP-C) is the smallest known member of the collectin family of animal lectins, many of which are involved in defence against microbial pathogens. It consists of an N-terminal collagen-like domain linked to C-terminal carbohydrate-recognition domains. MBP-C, overproduced in Chinese-hamster ovary cells, is post-translationally modified and processed in a manner similar to the native lectin. Analytical ultracentrifugation experiments indicate that MBP-C is trimeric, with a weight-averaged molecular mass of approx. 77 kDa. The rate of sedimentation of MBP-C and its mobility on gel filtration suggest a highly elongated molecule. Anomalous behaviour on gel filtration due to this extended conformation may explain previous suggestions that MBP-C forms a higher oligomer. The polypeptide chains of the MBP-C trimer are linked by disulphide bonds between two cysteine residues at the N-terminal junction of the collagen-like domain. Analysis of an N-terminal tryptic fragment reveals that the disulphide bonding in MBP-C is heterogeneous and asymmetrical. These results indicate that assembly of MBP-C oligomers probably proceeds in a C- to N-terminal direction: trimerization at the C-terminus is followed by assembly of the collagenous domain and finally formation of N-terminal disulphide bonds. The relatively simple organization of MBP-C provides a template for understanding larger, more complex collectins.
-
Structural Analysis of Monosaccharide Recognition by Rat Liver Mannose-Binding Protein
The Journal of biological chemistry, 1996Co-Authors: Kurt Drickamer, William I. WeisAbstract:The structural basis of carbohydrate recognition by rat liver Mannose-Binding Protein (MBP-C) has been explored by determining the three-dimensional structure of the C-type carbohydrate-recognition domain (CRD) of MBP-C using x-ray crystallography. The structure was solved by molecular replacement using rat serum Mannose-Binding Protein (MBP-A) as a search model and was refined to maximum Bragg spacings of 1.7 A. Despite their almost identical folds, the dimeric structures formed by the two MBP CRDs differ dramatically. Complexes of MBP-C with methyl glycosides of Mannose, N-acetylglucosamine, and fucose were prepared by soaking MBP-C crystals in solutions containing these sugars. Surprisingly, the pyranose ring of Mannose is rotated 180 degrees relative to the orientation observed previously in MBP-A, but the local interactions between sugar and Protein are preserved. For each of the bound sugars, vicinal, equatorial hydroxyl groups equivalent to the 3- and 4-OH groups of Mannose directly coordinate Ca2+ and form hydrogen bonds with residues also serving as Ca2+ ligands. Few interactions are observed between other parts of the sugar and the Protein. A complex formed between free galactose and MBP-C reveals a similar mode of Binding, with the anomeric hydroxyl group serving as one of the Ca2+ ligands. A second Binding site for Mannose has also been observed in one of two copies in the asymmetric unit at a sugar concentration of 1.3 M. These structures explain how MBPs recognize a wide range of monosaccharides and suggest how fine specificity differences between MBP-A and MBP-C may be achieved.
-
Multivalent ligand Binding by serum Mannose-Binding Protein.
Archives of biochemistry and biophysics, 1992Co-Authors: Reiko T. Lee, Kurt Drickamer, Yoshitaka Ichikawa, Toshisuke Kawasaki, Yuan C. LeeAbstract:Abstract The serum-type Mannose-Binding Protein (MBP) is a defense molecule that has carbohydrate-dependent bactericidal effects. It shares with mammalian and chicken hepatic lectins similarity in the primary structure of the carbohydrate-recognition domain, as well as the ligand-Binding mode: a high affinity ( K D ~ nM) is generated by clustering of ~30 terminal target sugar residues on a macromolecule, such as bovine serum albumin, although the individual monosaccharides have low affinity ( K D 0.1–1 mM). On the other hand, MBP does not manifest any significant affinity enhancement toward small, di-and trivalent ligands, in contrast to the hepatic lectins whose affinity toward divalent ligands of comparable structures increased from 100- to 1000-fold. Such differences may be explained on the basis of different subunit organization between the hepatic lectins and MBP.
Teizo Fujita - One of the best experts on this subject based on the ideXlab platform.
-
Substances reactive with Mannose-Binding Protein (MBP) in sera of patients with rheumatoid arthritis.
Fukushima journal of medical science, 1997Co-Authors: Sato R, Misao Matsushita, Miyata M, Yukio Sato, Reiji Kasukawa, Teizo FujitaAbstract:OBJECTIVES In order to evaluate the role of Mannose-Binding Protein (MBP) in rheumatoid arthritis, we characterized MBP-Binding substances in sera of patients with this disease. METHODS An enzyme linked immunosorbent assay (ELISA) was used to detect MBP-Binding substances in sera of patients with RA. We applied the sera of two RA patients to an immobilized MBP column, and by means of both ELISA and molecular sieve chromatography, examined the substances that bound to MBP. MBP-MASP complexes were added to the fractions containing the Binding substances, and C4-consuming activity was examined. RESULTS Sera of patients with RA showed stronger MBP Binding on ELISA than did those of normal controls. In the case of RA sera, both IgG was IgM-RF eluted from the MBP column, whereas with normal controls, only IgG was obtained. The results of molecular sieve chromatography showed that the Binding substances of RA patients consisted of immune complexes containing IgG and IgM-RF. These substances were specifically bound to MBP, and once bound, the MBP-MASP complexes were then able to consume C4. CONCLUSION MBP binds to immune complexes consisting of IgG and IgM-RF, and probably recognizes either the Mannose moiety of IgM-RF or the N-acetyl-glucosamine of agalactosyl IgG. When this occurs in RA patients, the lectin pathway would then be activated.
-
Exon structure of the gene encoding the human Mannose-Binding Protein-associated serine protease light chain: comparison with complement C1r and C1s genes.
International immunology, 1996Co-Authors: Yuichi Endo, Misao Matsushita, Tetsuo Sato, Teizo FujitaAbstract:Mannan or Mannose-Binding Protein (MBP) requires a novel serine protease termed MBP-associated serine protease (MASP) for activation of the complement cascade. In this study, we analyzed MASP genomic clones and found that the light chain (catalytic domain) is encoded by six exons, whereas those of the complement C1 subunits, C1r and C1s, and the haptoglobin segment have been reported to be encoded by a single exon. We confirmed the intron-lacking sequence of C1r by analysis of its genome. These results, in conjunction with those obtained by constructing a phylogenetic tree for these Proteins, suggest that the MASP gene is prototype and that the intron-lacking sequences of the other serine proteases have a more recent history.
-
cleavage of the third component of complement c3 by Mannose Binding Protein associated serine protease masp with subsequent complement activation
Immunobiology, 1995Co-Authors: Misao Matsushita, Teizo FujitaAbstract:We have previously shown that a novel C1s-like serine protease termed MBP-associated serine protease (MASP) is responsible for activation of the complement cascade initiated by Mannose-Binding Protein (MBP). In this communication, we report that MASP is unique in having the proteolytic capacity to cleave C3 with subsequent activation of the alternative pathway, a capacity which C1s lacks.
-
α2-Macroglobulin binds to and inhibits Mannose-Binding Protein-associated serine protease
International immunology, 1995Co-Authors: Itaru Terai, Misao Matsushita, Teizo Fujita, Kunihiko Kobayashi, Kazuhiko MatsunoAbstract:We determined the presence in human serum of a complex consisting of Mannose-Binding Protein (MBP), MBP-associated serine protease (MASP), which is a C1s-like Protein with complement activation activity, and alpha 2-macroglobulin (alpha 2M). Binding between these three molecules was in an ascending order of MBP, MASP and alpha 2M, in that alpha 2M bound directly to MASP, possibly through covalent bonds, whereas the Binding between MBP and MASP was reversible and Ca(2+)-dependent. Since it was found that alpha 2M can inhibit complement activation by MASP and that MASP in the complex lacks esterolytic activity, it is conceivable that alpha 2M plays a regulatory role in MBP-derived complement activation via a mechanism involving MASP (the lectin pathway).
-
Mannose‐Binding Protein Recognizes Glioma Cells: In vitro Analysis of Complement Activation on Glioma Cells via the Lectin Pathway
Japanese journal of cancer research : Gann, 1995Co-Authors: Takashi Fujita, Misao Matsushita, Satoshi Taira, Namio Kodama, Teizo FujitaAbstract:The lectin pathway is a novel pathway for activation of the complement cascade, which is initiated by the Binding of Mannose-Binding Protein (MBP) to its carbohydrate ligands. We investigated whether the complement system was activated in vitro by glioma cells through this pathway to the C3 level. MBP was found to bind to all six glioma cell lines tested by using flow cytometric analysis. Binding of a complex of MBP-associated serine protease and MBP was observed in two of the cell lines examined, thereby resulting in C4 consumption. Activation of C3 was hemolytically evaluated in these two lines. C3 consumption was also observed in one. Based on these results, it is likely that recognition by MBP followed by complement activation occurs in certain glioma cell lines.
William I. Weis - One of the best experts on this subject based on the ideXlab platform.
-
structure of a selectin like mutant of Mannose Binding Protein complexed with sialylated and sulfated lewis x oligosaccharides
Biochemistry, 1997Co-Authors: William I. WeisAbstract:Rat serum Mannose-Binding Protein in which residues 211−213 have been changed to the Lys-Lys-Lys sequence found in E-selectin binds HL-60 cells and the oligosaccharide 3‘-NeuAc-Lex. To understand how this mutant, designated K3, mimics the carbohydrate-Binding properties of E-selectin, structures of K3 alone and in complexes with 3‘-NeuAc-Lex, 3‘-sulfo-Lex, and 4‘-sulfo-Lex have been determined at 1.95−2.1 A resolution by X-ray crystallography. The region of K3 that interacts with bound oligosaccharides superimposes closely with the corresponding region of unliganded E-selectin. In each of the oligosaccharide−Protein complexes, the 2- and 3-OH of Fuc coordinate Ca2+ and form a network of cooperative hydrogen bonds with amino acid side chains that also coordinate the Ca2+. Lys211 of the K3 mutant, which corresponds to Lys111 of E-selectin, interacts with each of the three bound ligands: the Nζ atom donates a hydrogen bond to the 4-OH of Gal in 3‘-NeuAc-Lex, forms a water-mediated hydrogen bond with the 4-OH...
-
Structural Analysis of Monosaccharide Recognition by Rat Liver Mannose-Binding Protein
The Journal of biological chemistry, 1996Co-Authors: Kurt Drickamer, William I. WeisAbstract:The structural basis of carbohydrate recognition by rat liver Mannose-Binding Protein (MBP-C) has been explored by determining the three-dimensional structure of the C-type carbohydrate-recognition domain (CRD) of MBP-C using x-ray crystallography. The structure was solved by molecular replacement using rat serum Mannose-Binding Protein (MBP-A) as a search model and was refined to maximum Bragg spacings of 1.7 A. Despite their almost identical folds, the dimeric structures formed by the two MBP CRDs differ dramatically. Complexes of MBP-C with methyl glycosides of Mannose, N-acetylglucosamine, and fucose were prepared by soaking MBP-C crystals in solutions containing these sugars. Surprisingly, the pyranose ring of Mannose is rotated 180 degrees relative to the orientation observed previously in MBP-A, but the local interactions between sugar and Protein are preserved. For each of the bound sugars, vicinal, equatorial hydroxyl groups equivalent to the 3- and 4-OH groups of Mannose directly coordinate Ca2+ and form hydrogen bonds with residues also serving as Ca2+ ligands. Few interactions are observed between other parts of the sugar and the Protein. A complex formed between free galactose and MBP-C reveals a similar mode of Binding, with the anomeric hydroxyl group serving as one of the Ca2+ ligands. A second Binding site for Mannose has also been observed in one of two copies in the asymmetric unit at a sugar concentration of 1.3 M. These structures explain how MBPs recognize a wide range of monosaccharides and suggest how fine specificity differences between MBP-A and MBP-C may be achieved.
-
structure of a c type Mannose Binding Protein complexed with an oligosaccharide
Nature, 1992Co-Authors: Kurt Drickamer, William I. Weis, Wayne A HendricksonAbstract:C-type (Ca2+-dependent) animal lectins such as Mannose-Binding Proteins mediate many cell-surface carbohydrate-recognition events. The crystal structure at 1.7 A resolution of the carbohydrate-recognition domain of rat Mannose-Binding Protein complexed with an oligoMannose asparaginyl-oligosaccharide reveals that Ca2+ forms coordination bonds with the carbohydrate ligand. Carbohydrate specificity is determined by a network of coordination and hydrogen bonds that stabilizes the ternary complex of Protein, Ca2+ and sugar. Two branches of the oligosaccharide crosslink neighbouring carbohydrate-recognition domains in the crystal, enabling multivalent Binding to a single oligosaccharide chain to be visualized directly.
-
structure of the calcium dependent lectin domain from a rat Mannose Binding Protein determined by mad phasing
Science, 1991Co-Authors: William I. Weis, Kurt Drickamer, Richard Kahn, R Fourme, Wayne A HendricksonAbstract:Calcium-dependent (C-type) animal lectins participate in many cell surface recognition events mediated by Protein-carbohydrate interactions. The C-type lectin family includes cell adhesion molecules, endocytic receptors, and extracellular matrix Proteins. Mammalian Mannose-Binding Proteins are C-type lectins that function in antibody-independent host defense against pathogens. The crystal structure of the carbohydrate-recognition domain of a rat Mannose-Binding Protein, determined as the holmium-substituted complex by multiwavelength anomalous dispersion (MAD) phasing, reveals an unusual fold consisting of two distinct regions, one of which contains extensive nonregular secondary structure stabilized by two holmium ions. The structure explains the conservation of 32 residues in all C-type carbohydrate-recognition domains, suggesting that the fold seen here is common to these domains. The strong anomalous scattering observed at the Ho LIII edge demonstrates that traditional heavy atom complexes will be generally amenable to the MAD phasing method.
-
physical characterization and crystallization of the carbohydrate recognition domain of a Mannose Binding Protein from rat
Journal of Biological Chemistry, 1991Co-Authors: William I. Weis, Wayne A Hendrickson, G V Crichlow, H M Murthy, Kurt DrickamerAbstract:A portion of rat Mannose-Binding Protein A (MBP-A), a Ca(2+)-dependent animal lectin, has been overproduced in a bacterial expression system, biochemically characterized, and crystallized. A fragment corresponding to the COOH-terminal 115 residues of native MBP-A, produced by subtilisin digestion of the bacterially expressed Protein, contains the carbohydrate-recognition domain (CRD). Gel filtration, chemical cross-linking, and crystallographic self-rotation function analyses indicate that the subtilisin fragment is a dimer, although the complete bacterially expressed fragment, containing the neck and CRD of MBP-A, is a trimer. Crystals of the minimal CRD, obtained only as a complex with a Man6GlcNAc2Asn glycopeptide, diffract to Bragg spacings of at least 1.7 A. Several trivalent lanthanide ions (Ln3+) can substitute for Ca2+, as assessed by their ability to support carbohydrate Binding and to protect the CRD from proteolysis in a manner similar to that observed for Ca2+. These assays indicate that Ln2+ binds about 30 times more tightly than Ca2+ to the CRD, and that two Ca2+ or Ln3+ bind to each monomer, a result confirmed by determination of the Ho3+ positions in a Ho(3+)-containing crystal of the CRD. Crystals grown in the presence of Ln3+ belong to different space groups from those obtained with Ca2+ and are therefore not useable for traditional crystallographic phase determination methods, but are well-suited for high resolution structure determination by multiwavelength anomalous dispersion phasing.
R A Ezekowitz - One of the best experts on this subject based on the ideXlab platform.
-
the serum Mannose Binding Protein and the macrophage Mannose receptor are pattern recognition molecules that link innate and adaptive immunity
Seminars in Immunology, 1998Co-Authors: Iain P Fraser, Henry Koziel, R A EzekowitzAbstract:Abstract The innate immune system evolved to protect the host in the early phases of an infectious challenge. The soluble Mannose Binding Protein, and the cell surface Mannose receptor are two key pattern recognition molecules of innate immunity. The ligand Binding specificity of these molecules enables them to differentiate ‘self’ from ‘non-self’. These pattern recognition capabilities are coupled to effector functions, which enable them to interact with other molecules of the immune system. In this way, these pattern recognition molecules are able to serve as a link between the innate and adaptive immune systems.
-
Interactions of human Mannose-Binding Protein with lipoteichoic acids
Infection and immunity, 1996Co-Authors: Vsevolod Polotsky, W. Fischer, R A Ezekowitz, Keith A. JoinerAbstract:We explored the interaction of human recombinant Mannose-Binding Protein and lipoteichoic acids (LTAs) by enzyme-linked immunosorbent assay. The best ligand was Micrococcus luteus lipomannan, followed by Enterococcus spp. LTA containing mono-, di-, and oligoglucosyl substituents. LTAs lacking terminal sugars (those of Streptococcus pyogenes and Staphylococcus aureus) or containing galactosyl substituents (those of Listeria spp. and Lactococcus spp.) were poor ligands. These results are consistent with known structural requirements for Binding through the Mannose-Binding Protein carbohydrate recognition domain.
-
Human Mannose-Binding Protein carbohydrate recognition domain trimerizes through a triple |[alpha]|-helical coiled-coil
Nature structural biology, 1995Co-Authors: Steven Sheriff, Chonghwan Chang, R A EzekowitzAbstract:Human Mannose-Binding Protein is a hexamer of trimers with each subunit consisting of an amino-terminal region rich in cysteine, 19 collagen repeats, a ‘neck’, and a carbohydrate recognition domain that requires calcium to bind ligand. A 148-residue peptide, consisting of the ‘neck’ and carbohydrate recognition domains forms trimers in solution and in crystals. The structure of this trimeric peptide has been determined in two different crystal forms. The ‘neck’ forms a triple α-helical coiled-coil. Each α-helix interacts with a neighbouring carbohydrate recognition domain. The spatial arrangement of the carbohydrate recognition domains suggest how MBP trimers form the basic recognition unit for branched oligosaccharides on microorganisms.
-
human Mannose Binding Protein carbohydrate recognition domain trimerizes through a triple alpha helical coiled coil
Nature Structural & Molecular Biology, 1994Co-Authors: Steven Sheriff, Chonghwan Chang, R A EzekowitzAbstract:Human Mannose-Binding Protein is a hexamer of trimers with each subunit consisting of an amino-terminal region rich in cysteine, 19 collagen repeats, a ‘neck’, and a carbohydrate recognition domain that requires calcium to bind ligand. A 148-residue peptide, consisting of the ‘neck’ and carbohydrate recognition domains forms trimers in solution and in crystals. The structure of this trimeric peptide has been determined in two different crystal forms. The ‘neck’ forms a triple α-helical coiled-coil. Each α-helix interacts with a neighbouring carbohydrate recognition domain. The spatial arrangement of the carbohydrate recognition domains suggest how MBP trimers form the basic recognition unit for branched oligosaccharides on microorganisms.
Misao Matsushita - One of the best experts on this subject based on the ideXlab platform.
-
Substances reactive with Mannose-Binding Protein (MBP) in sera of patients with rheumatoid arthritis.
Fukushima journal of medical science, 1997Co-Authors: Sato R, Misao Matsushita, Miyata M, Yukio Sato, Reiji Kasukawa, Teizo FujitaAbstract:OBJECTIVES In order to evaluate the role of Mannose-Binding Protein (MBP) in rheumatoid arthritis, we characterized MBP-Binding substances in sera of patients with this disease. METHODS An enzyme linked immunosorbent assay (ELISA) was used to detect MBP-Binding substances in sera of patients with RA. We applied the sera of two RA patients to an immobilized MBP column, and by means of both ELISA and molecular sieve chromatography, examined the substances that bound to MBP. MBP-MASP complexes were added to the fractions containing the Binding substances, and C4-consuming activity was examined. RESULTS Sera of patients with RA showed stronger MBP Binding on ELISA than did those of normal controls. In the case of RA sera, both IgG was IgM-RF eluted from the MBP column, whereas with normal controls, only IgG was obtained. The results of molecular sieve chromatography showed that the Binding substances of RA patients consisted of immune complexes containing IgG and IgM-RF. These substances were specifically bound to MBP, and once bound, the MBP-MASP complexes were then able to consume C4. CONCLUSION MBP binds to immune complexes consisting of IgG and IgM-RF, and probably recognizes either the Mannose moiety of IgM-RF or the N-acetyl-glucosamine of agalactosyl IgG. When this occurs in RA patients, the lectin pathway would then be activated.
-
Exon structure of the gene encoding the human Mannose-Binding Protein-associated serine protease light chain: comparison with complement C1r and C1s genes.
International immunology, 1996Co-Authors: Yuichi Endo, Misao Matsushita, Tetsuo Sato, Teizo FujitaAbstract:Mannan or Mannose-Binding Protein (MBP) requires a novel serine protease termed MBP-associated serine protease (MASP) for activation of the complement cascade. In this study, we analyzed MASP genomic clones and found that the light chain (catalytic domain) is encoded by six exons, whereas those of the complement C1 subunits, C1r and C1s, and the haptoglobin segment have been reported to be encoded by a single exon. We confirmed the intron-lacking sequence of C1r by analysis of its genome. These results, in conjunction with those obtained by constructing a phylogenetic tree for these Proteins, suggest that the MASP gene is prototype and that the intron-lacking sequences of the other serine proteases have a more recent history.
-
cleavage of the third component of complement c3 by Mannose Binding Protein associated serine protease masp with subsequent complement activation
Immunobiology, 1995Co-Authors: Misao Matsushita, Teizo FujitaAbstract:We have previously shown that a novel C1s-like serine protease termed MBP-associated serine protease (MASP) is responsible for activation of the complement cascade initiated by Mannose-Binding Protein (MBP). In this communication, we report that MASP is unique in having the proteolytic capacity to cleave C3 with subsequent activation of the alternative pathway, a capacity which C1s lacks.
-
α2-Macroglobulin binds to and inhibits Mannose-Binding Protein-associated serine protease
International immunology, 1995Co-Authors: Itaru Terai, Misao Matsushita, Teizo Fujita, Kunihiko Kobayashi, Kazuhiko MatsunoAbstract:We determined the presence in human serum of a complex consisting of Mannose-Binding Protein (MBP), MBP-associated serine protease (MASP), which is a C1s-like Protein with complement activation activity, and alpha 2-macroglobulin (alpha 2M). Binding between these three molecules was in an ascending order of MBP, MASP and alpha 2M, in that alpha 2M bound directly to MASP, possibly through covalent bonds, whereas the Binding between MBP and MASP was reversible and Ca(2+)-dependent. Since it was found that alpha 2M can inhibit complement activation by MASP and that MASP in the complex lacks esterolytic activity, it is conceivable that alpha 2M plays a regulatory role in MBP-derived complement activation via a mechanism involving MASP (the lectin pathway).
-
Mannose‐Binding Protein Recognizes Glioma Cells: In vitro Analysis of Complement Activation on Glioma Cells via the Lectin Pathway
Japanese journal of cancer research : Gann, 1995Co-Authors: Takashi Fujita, Misao Matsushita, Satoshi Taira, Namio Kodama, Teizo FujitaAbstract:The lectin pathway is a novel pathway for activation of the complement cascade, which is initiated by the Binding of Mannose-Binding Protein (MBP) to its carbohydrate ligands. We investigated whether the complement system was activated in vitro by glioma cells through this pathway to the C3 level. MBP was found to bind to all six glioma cell lines tested by using flow cytometric analysis. Binding of a complex of MBP-associated serine protease and MBP was observed in two of the cell lines examined, thereby resulting in C4 consumption. Activation of C3 was hemolytically evaluated in these two lines. C3 consumption was also observed in one. Based on these results, it is likely that recognition by MBP followed by complement activation occurs in certain glioma cell lines.