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Sialyltransferases --- Colostrum --- Lectins --- metabolism --- enzymology --- isolation & purification
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Sialyltransferases --- Gangliosides --- Microsomes, Liver --- metabolism --- enzymology
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Researchers from our laboratory identified a new mechanism of anergy of CD8+ T lymphocytes (CTL), which could explain the loss of function observed in human tumor-infiltrating T lymphocytes.
After in vitro stimulation, the CTL lose temporarily the capacity to secrete cytokines. Confocal microscopy and FRET analyses, a technique allowing to estimate the proximity between two molecules, indicated that the T cell receptor (TCR) and the CD8 co-receptor, both required for the interaction with the HLA-peptide complex, are not co-localized in non-functional CTL. This loss of co-localization seems to be due to the reduction the mobility of the TCR trapped in a lattice of glycoproteins connected to galectine-3. Galectin-3 is a lectine that has a high affinity for the N-Acetyllactosamine (LacNAc) residues found on numerous glycoproteins such as TCR.
been shown that, after their stimulation, mouse T lymphocytes endure important changes of glycosylation of their surface proteins. If these changes also happen in human T lymphocytes, they could be responsible for a more important binding of the galectine-3 on the surface of T lymphocytes.
The present study focuses on two sialyltransferases, ST3Gal-1 and ST6Gal-1, which catalyse the transfer of a sialic acid on the O-glycans and the N-glycans respectively. The expression of the genes encoding for these enzymes has been analysed by microarray and semi-quantitative PCR. Their gene expression decreased strongly 24 hours after stimulation of CTL and recovered their initial level after 3 to 5 days. If we suppose that galectine-3 preferentially bind to unsialylated glycans, then, the decrease of the sialyltransferases expression would allow more binding of galectin-3 to the surface of activated CTL and therefore, promote the entrapment of the TCR.
We started to test the hypothesis that a stable expression of sialyltransferases could allow the T lymphocytes to keep their LacNAc residues sialylated even after stimulation. The coding sequence of these enzymes were cloned and introduced into a lentiviral vector in order to transduce CTL. For the time being, we are culturing and expanding the transduced CD8+ T lymphocytes and we hope, in a close future, to measure the sialyltransferases expression, the cytokines production and the capacity to bind to the HLA-peptide complex in these transduced CTL Des chercheurs de notre laboratoire ont identifié un nouveau mécanisme d’anergie des lymphocytes T CD8+ (CTL) qui pourrait fournir une explication à la perte de fonction observée chez des lymphocytes T humains infiltrant les tumeurs.
Après stimulation in vitro, les CTL perdent transitoirement la capacité à sécréter des cytokines. Des analyses de microscopie confocale et des analyses FRET, une technique permettant d’estimer la proximité entre deux molécules, ont révélé que le récepteur T (TCR) et le co-récepteur CD8, tous deux indispensables pour l’interaction avec le complexe HLA-peptide, ne sont plus co-localisés sur des CTL non fonctionnels. Cette perte de co-localisation du TCR et du co-récepteur CD8 semble due à la réduction de la mobilité du TCR emprisonné dans un réseau de glycoprotéines reliées par de la galectine-3. La galectine-3 est une lectine qui possède une haute affinité pour les résidus N-Acetyllacosamine (LacNAc) qui sont présents sur de nombreuses glycoprotéines dont les TCR.
Il a été montré qu’après stimulation, les lymphocytes T murins subissent d’importants changements de glycosylation de leurs protéines de surface. Si de tels changements ont également lieu lors de la stimulation des lymphocytes T humains, ils pourraient être à l’origine d’une plus grande liaison de la galectine-3 en surface des lymphocytes T.
Mon travail s’est porté sur l’étude de deux sialyltransférases, ST3-Gal-1 et ST6-Gal-1 qui catalysent le transfert d’un acide sialique sur les O-glycannes et les N-glycannes respectivement. L’expression des gènes codant ces deux enzymes, ont été analysés par microdamiers et par PCR semi-quantitative. Cette expression diminue fortement 24 heures après la stimulation du CTL et le niveau de départ n’est retrouvé qu’après 3 à 5 jours. En supposant que la galectine-3 se lie plus facilement aux glycans non sialylés, la diminution d’expression des sialyltransférases permettrait une liaison plus importante de la galectine-3 la surface des CTL activés et par là, favoriserait l’emprisonnement du TCR.
Nous avons commencé à tester l’hypothèse que l’expression stable des sialyltransférases permettrait aux lymphocytes T de garder les motifs LacNAc sialylés même après stimulation antigénique. Les séquences codantes de ces deux enzymes ont été clonées et introduites dans des vecteurs lentiviraux afin de transduire des CTL. Nous disposons actuellement de lymphocytes T CD8+ tranduits et nous espérons dans un futur proche, pouvoir mesurer l’expression des sialyltransférases, la prodution de cytokines et la capacité à lier le complexe HLA-peptide chez ces CTL transduits.
Sialyltransferases --- CD8-Positive T-Lymphocytes --- Clonal Anergy --- Glycosylation
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Carbohydrate-active enzymes are responsible for both biosynthesis and the breakdown of carbohydrates and glycoconjugates. They are involved in many metabolic pathways; in the biosynthesis and degradation of various biomolecules, such as bacterial exopolysaccharides, starch, cellulose and lignin; and in the glycosylation of proteins and lipids. Carbohydrate-active enzymes are classified into glycoside hydrolases, glycosyltransferases, polysaccharide lyases, carbohydrate esterases, and enzymes with auxiliary activities (CAZy database, www.cazy.org). Glycosyltransferases synthesize a huge variety of complex carbohydrates with different degrees of polymerization, moieties and branching. On the other hand, complex carbohydrate breakdown is carried out by glycoside hydrolases, polysaccharide lyases and carbohydrate esterases. Their interesting reactions have attracted the attention of researchers across scientific fields, ranging from basic research to biotechnology. Interest in carbohydrate-active enzymes is due not only to their ability to build and degrade biopolymers—which is highly relevant in biotechnology—but also because they are involved in bacterial biofilm formation, and in glycosylation of proteins and lipids, with important health implications. This book gathers new research results and reviews to broaden our understanding of carbohydrate-active enzymes, their mutants and their reaction products at the molecular level.
Research & information: general --- Biology, life sciences --- glycoside hydrolase --- xylanase --- carbohydrate-binding module --- CBM truncation --- halo-tolerant --- xylan hydrolysis --- pectate lyase --- Paenibacillus polymyxa --- pectins --- degradation --- Lactobacillus --- GH13_18 --- sucrose phosphorylase --- glycoside phosphorylase --- Ilumatobacter coccineus --- Thermoanaerobacterium thermosaccharolyticum --- crystallography --- galactosidase --- hydrolysis --- reaction mechanism --- complex structures --- cold-adapted --- GH2 --- Cellulase --- random mutagenesis --- cellulose degradation --- structural analysis --- α-amylase --- starch degradation --- biotechnology --- structure --- pyruvylation --- pyruvyltransferase --- exopolysaccharides --- capsular polysaccharides --- cell wall glycopolymers --- N-glycans --- lipopolysaccharides --- biosynthesis --- sequence space --- pyruvate analytics --- Nanopore sequencing --- ganoderic acid --- Bacillus thuringiensis --- biotransformation --- glycosyltransferase --- whole genome sequencing --- applied biocatalysis --- enzyme cascades --- chemoenzymatic synthesis --- sugar chemistry --- carbohydrate --- Leloir --- nucleotide --- Enzymatic glycosylation --- alkyl glycosides (AG)s --- Deep eutectic solvents (DES) --- Amy A --- alcoholysis --- methanol --- circular dichroism --- protein stability --- alpha-amylase --- biomass --- hemicellulose --- bioethanol --- xylanolytic enzyme --- hemicellulase --- lysozyme --- peptidoglycan cleavage --- avian gut GH22 --- crystal structure --- glycosylation --- UDP-glucose pyrophosphorylase --- UDP-glucose --- nucleotide donors --- Rhodococcus, Actinobacteria, gene redundancy --- Leloir glycosyltransferases --- activated sugar --- UTP --- thermophilic fungus --- β-glucosidases --- Chaetomium thermophilum --- protein structure --- fungal enzymes --- endo-α-(1→6)-d-mannase --- mannoside --- Mycobacterium --- lipomannan --- lipoarabinomannan --- phosphatidylinositol mannosides --- GH68 --- fructosyltransferase --- fructooligosaccharides --- FOS biosynthesis --- prebiotic oligosaccharides --- Arxula adeninivorans --- α-glucosidase --- maltose --- panose --- amylopectin --- glycogen --- inhibition by Tris --- transglycosylation --- glycoside hydrolyase --- Trichoderma harzianum --- complete saccharification --- lignocellulose --- N-acetylhexosamine specificity --- GH20 --- phylogenetic analysis --- NAG-oxazoline --- acceptor diversity --- lacto-N-triose II --- human milk oligosaccharides --- NMR --- molecular phylogeny --- α2,8-sialyltransferases --- polySia motifs --- evolution --- ST8Sia --- functional genomics --- glycoside hydrolase --- xylanase --- carbohydrate-binding module --- CBM truncation --- halo-tolerant --- xylan hydrolysis --- pectate lyase --- Paenibacillus polymyxa --- pectins --- degradation --- Lactobacillus --- GH13_18 --- sucrose phosphorylase --- glycoside phosphorylase --- Ilumatobacter coccineus --- Thermoanaerobacterium thermosaccharolyticum --- crystallography --- galactosidase --- hydrolysis --- reaction mechanism --- complex structures --- cold-adapted --- GH2 --- Cellulase --- random mutagenesis --- cellulose degradation --- structural analysis --- α-amylase --- starch degradation --- biotechnology --- structure --- pyruvylation --- pyruvyltransferase --- exopolysaccharides --- capsular polysaccharides --- cell wall glycopolymers --- N-glycans --- lipopolysaccharides --- biosynthesis --- sequence space --- pyruvate analytics --- Nanopore sequencing --- ganoderic acid --- Bacillus thuringiensis --- biotransformation --- glycosyltransferase --- whole genome sequencing --- applied biocatalysis --- enzyme cascades --- chemoenzymatic synthesis --- sugar chemistry --- carbohydrate --- Leloir --- nucleotide --- Enzymatic glycosylation --- alkyl glycosides (AG)s --- Deep eutectic solvents (DES) --- Amy A --- alcoholysis --- methanol --- circular dichroism --- protein stability --- alpha-amylase --- biomass --- hemicellulose --- bioethanol --- xylanolytic enzyme --- hemicellulase --- lysozyme --- peptidoglycan cleavage --- avian gut GH22 --- crystal structure --- glycosylation --- UDP-glucose pyrophosphorylase --- UDP-glucose --- nucleotide donors --- Rhodococcus, Actinobacteria, gene redundancy --- Leloir glycosyltransferases --- activated sugar --- UTP --- thermophilic fungus --- β-glucosidases --- Chaetomium thermophilum --- protein structure --- fungal enzymes --- endo-α-(1→6)-d-mannase --- mannoside --- Mycobacterium --- lipomannan --- lipoarabinomannan --- phosphatidylinositol mannosides --- GH68 --- fructosyltransferase --- fructooligosaccharides --- FOS biosynthesis --- prebiotic oligosaccharides --- Arxula adeninivorans --- α-glucosidase --- maltose --- panose --- amylopectin --- glycogen --- inhibition by Tris --- transglycosylation --- glycoside hydrolyase --- Trichoderma harzianum --- complete saccharification --- lignocellulose --- N-acetylhexosamine specificity --- GH20 --- phylogenetic analysis --- NAG-oxazoline --- acceptor diversity --- lacto-N-triose II --- human milk oligosaccharides --- NMR --- molecular phylogeny --- α2,8-sialyltransferases --- polySia motifs --- evolution --- ST8Sia --- functional genomics
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Carbohydrate-active enzymes are responsible for both biosynthesis and the breakdown of carbohydrates and glycoconjugates. They are involved in many metabolic pathways; in the biosynthesis and degradation of various biomolecules, such as bacterial exopolysaccharides, starch, cellulose and lignin; and in the glycosylation of proteins and lipids. Carbohydrate-active enzymes are classified into glycoside hydrolases, glycosyltransferases, polysaccharide lyases, carbohydrate esterases, and enzymes with auxiliary activities (CAZy database, www.cazy.org). Glycosyltransferases synthesize a huge variety of complex carbohydrates with different degrees of polymerization, moieties and branching. On the other hand, complex carbohydrate breakdown is carried out by glycoside hydrolases, polysaccharide lyases and carbohydrate esterases. Their interesting reactions have attracted the attention of researchers across scientific fields, ranging from basic research to biotechnology. Interest in carbohydrate-active enzymes is due not only to their ability to build and degrade biopolymers—which is highly relevant in biotechnology—but also because they are involved in bacterial biofilm formation, and in glycosylation of proteins and lipids, with important health implications. This book gathers new research results and reviews to broaden our understanding of carbohydrate-active enzymes, their mutants and their reaction products at the molecular level.
glycoside hydrolase --- xylanase --- carbohydrate-binding module --- CBM truncation --- halo-tolerant --- xylan hydrolysis --- pectate lyase --- Paenibacillus polymyxa --- pectins --- degradation --- Lactobacillus --- GH13_18 --- sucrose phosphorylase --- glycoside phosphorylase --- Ilumatobacter coccineus --- Thermoanaerobacterium thermosaccharolyticum --- crystallography --- galactosidase --- hydrolysis --- reaction mechanism --- complex structures --- cold-adapted --- GH2 --- Cellulase --- random mutagenesis --- cellulose degradation --- structural analysis --- α-amylase --- starch degradation --- biotechnology --- structure --- pyruvylation --- pyruvyltransferase --- exopolysaccharides --- capsular polysaccharides --- cell wall glycopolymers --- N-glycans --- lipopolysaccharides --- biosynthesis --- sequence space --- pyruvate analytics --- Nanopore sequencing --- ganoderic acid --- Bacillus thuringiensis --- biotransformation --- glycosyltransferase --- whole genome sequencing --- applied biocatalysis --- enzyme cascades --- chemoenzymatic synthesis --- sugar chemistry --- carbohydrate --- Leloir --- nucleotide --- Enzymatic glycosylation --- alkyl glycosides (AG)s --- Deep eutectic solvents (DES) --- Amy A --- alcoholysis --- methanol --- circular dichroism --- protein stability --- alpha-amylase --- biomass --- hemicellulose --- bioethanol --- xylanolytic enzyme --- hemicellulase --- lysozyme --- peptidoglycan cleavage --- avian gut GH22 --- crystal structure --- glycosylation --- UDP-glucose pyrophosphorylase --- UDP-glucose --- nucleotide donors --- Rhodococcus, Actinobacteria, gene redundancy --- Leloir glycosyltransferases --- activated sugar --- UTP --- thermophilic fungus --- β-glucosidases --- Chaetomium thermophilum --- protein structure --- fungal enzymes --- endo-α-(1→6)-d-mannase --- mannoside --- Mycobacterium --- lipomannan --- lipoarabinomannan --- phosphatidylinositol mannosides --- GH68 --- fructosyltransferase --- fructooligosaccharides --- FOS biosynthesis --- prebiotic oligosaccharides --- Arxula adeninivorans --- α-glucosidase --- maltose --- panose --- amylopectin --- glycogen --- inhibition by Tris --- transglycosylation --- glycoside hydrolyase --- Trichoderma harzianum --- complete saccharification --- lignocellulose --- N-acetylhexosamine specificity --- GH20 --- phylogenetic analysis --- NAG-oxazoline --- acceptor diversity --- lacto-N-triose II --- human milk oligosaccharides --- NMR --- molecular phylogeny --- α2,8-sialyltransferases --- polySia motifs --- evolution --- ST8Sia --- functional genomics --- n/a
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