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Jacques U. Baenziger - One of the best experts on this subject based on the ideXlab platform.
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closely related mammals have distinct Asialoglycoprotein Receptor carbohydrate specificities
Journal of Biological Chemistry, 2004Co-Authors: Eric I Park, Jacques U. BaenzigerAbstract:Abstract We recently reported that the rat Asialoglycoprotein Receptor binds oligosaccharides terminating with sialic acid (Sia) α2,6GalNAc. Despite a high percentage of identical amino acids in their sequences, orthologues of the Asialoglycoprotein Receptor (ASGP-R) in different mammals differ in their specificity for terminal Siaα2,6GalNAc. The recombinant subunit 1 of the ASGP-R from the rat (RHL-1 or rat hepatic lectin) and the mouse (MHL-1 or mouse hepatic lectin), which differ at only 12 positions in the amino acid sequence of their carbohydrate recognition domains, binds Siaα2,6GalNAcβ1,4GlcNAcβ1,2Man-bovine serum albumin and GalNAcβ1,4GlcNAcβ1,2Man-bovine serum albumin in ratios of 16:1.0 and 1.0:1.0, respectively. Mutagenesis was used to show that amino acids both in the immediate vicinity of the proposed binding site for terminal GalNAc and on the α2 helix that is distant from the binding site contribute to the specificity for terminal Siaα2,6GalNAc. Thus, multiple amino acid sequence alterations in two key locations contribute to the difference in specificity observed for the rat and mouse ASGP-Rs. We hypothesize that the altered specificity of ASPG-R orthologues in such evolutionarily closely related species reflects rapidly changing requirements for recognition of endogenous or exogenous oligosaccharides in vivo.
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rapid clearance of sialylated glycoproteins by the Asialoglycoprotein Receptor
Journal of Biological Chemistry, 2003Co-Authors: Eric I Park, Stephen M. Manzella, Jacques U. BaenzigerAbstract:Abstract The Asialoglycoprotein-Receptor (ASGP-R) located on liver parenchymal cells was originally identified and characterized on the basis of its ability to bind glycoproteins bearing terminal galactose (Gal) or N-acetylgalactosamine (GalNAc); however, endogenous ligands for the ASGP-R have not to date been definitively identified. We have determined that the rat ASGP-R specifically binds oligosaccharides terminating with the sequence Siaα2,6GalNAcβ1,4GlcNAcβ1,2Man. Bovine serum albumin chemically modified with 10–15 tetrasaccharides with the sequence Siaα2,6GalNAcβ1,4GlcNAcβ1,2Man is cleared from the blood of the rat with a half-life of <1 min by a Receptor located in the liver. We have isolated the Receptor and identified it as the ASGP-R. Furthermore, we have determined that subunit 1 of the ASGP-R accounts for the binding of terminal Siaα2,6GalNAcβ. Based on the newly defined specificity of the rat ASGP-R we hypothesize that glycoproteins bearing structures that are selectively modified with terminal Siaα2,6GalNAcβ and are released into the blood may be endogenous ligands for the rat ASGP-R.
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Rapid Clearance of Sialylated Glycoproteins by the Asialoglycoprotein Receptor
The Journal of biological chemistry, 2002Co-Authors: Eric I Park, Stephen M. Manzella, Jacques U. BaenzigerAbstract:The Asialoglycoprotein-Receptor (ASGP-R) located on liver parenchymal cells was originally identified and characterized on the basis of its ability to bind glycoproteins bearing terminal galactose (Gal) or N-acetylgalactosamine (GalNAc); however, endogenous ligands for the ASGP-R have not to date been definitively identified. We have determined that the rat ASGP-R specifically binds oligosaccharides terminating with the sequence Siaα2,6GalNAcβ1,4GlcNAcβ1,2Man. Bovine serum albumin chemically modified with 10–15 tetrasaccharides with the sequence Siaα2,6GalNAcβ1,4GlcNAcβ1,2Man is cleared from the blood of the rat with a half-life of
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Abnormal surface distribution of the human Asialoglycoprotein Receptor in cirrhosis.
Hepatology (Baltimore Md.), 1992Co-Authors: James B. Burgess, Jacques U. Baenziger, William R. BrownAbstract:Serum concentrations of Asialoglycoproteins are increased in cirrhosis. We hypothesized that this increase results from abnormalities in the Asialoglycoprotein Receptor, which is located on the sinusoidal and lateral membrane of hepatocytes. Therefore we searched for morphological alterations in the distribution of the Asialoglycoprotein Receptor in human liver, using a light microscopic immunoperoxidase method in autopsy livers. In 24 of 25 (96%) of patients without liver disease, the Asialoglycoprotein Receptor was located on the sinusoidal and, less prominently, the lateral surface of hepatocytes but not the canalicular surface. In contrast, in 12 of 18 (67%) patients with cirrhosis of various causes, the Receptor also was localized strikingly along the canalicular surface, with a corresponding decrease on the sinusoidal and lateral surfaces. We conclude that an abnormal cell-surface distribution of the Asialoglycoprotein Receptor commonly occurs in cirrhosis. This abnormality might result in impaired clearance of desialylated glycoproteins from plasma. (Hepatology 1992;15:702–706).
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The minor components of the rat Asialoglycoprotein Receptor are apically located in neonatal enterocytes.
Gastroenterology, 1991Co-Authors: Eun Y. Lee, Jacques U. Baenziger, Jane E. Hewitt, Katherine Deschryver-kecskemeti, David H. AlpersAbstract:Abstract Because specific uptake of the Asialoglycoprotein haptocorrin has been reported in suckling distal intestine, evidence of the Asialoglycoprotein Receptor in rat ileum was sought. On Western blot, two different polyclonal antisera against purified rat holoReceptor recognized only proteins of the size of the minor Receptor components (51 and 55 kilodaltons) in both suckling and adult rat intestine. Messenger RNA encoding the minor component (RHL-2/3) was detected in total RNA extracted from rat ileum. Calcium-specific binding of porcine or rat haptocorrin-[ 57 Co] cobalamin complexes was detected in the brush border membranes of distal suckling rat and porcine small intestine. This binding was almost completely blocked by another Asialoglycoprotein, asialofetuin. The pH optimum for binding was 6–9, with a K a of 0.25 nmol/L and a capacity of 4.6 fmol/mg protein. These properties, with the exception of the low capacity, are all consistent with those of the intact Receptor on hepatocytes. The intestinal Receptor was localized not to the basolateral membrane, as in the liver, but to the apical brush border, as suggested by the binding data. Furthermore, immunoperoxidase stains of paraffin-embedded tissue detected strong binding to the brush border and apical phagolysosome of mid and distal suckling rat intestine. These data show that, contrary to expectations, the minor components of the Asialoglycoprotein Receptor are functional and expressed in the apical membrane of the suckling intestine. The abundance of the protein by Western blot suggests possible roles for it in the neonatal gut other than haptocorrin binding.
Eric I Park - One of the best experts on this subject based on the ideXlab platform.
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closely related mammals have distinct Asialoglycoprotein Receptor carbohydrate specificities
Journal of Biological Chemistry, 2004Co-Authors: Eric I Park, Jacques U. BaenzigerAbstract:Abstract We recently reported that the rat Asialoglycoprotein Receptor binds oligosaccharides terminating with sialic acid (Sia) α2,6GalNAc. Despite a high percentage of identical amino acids in their sequences, orthologues of the Asialoglycoprotein Receptor (ASGP-R) in different mammals differ in their specificity for terminal Siaα2,6GalNAc. The recombinant subunit 1 of the ASGP-R from the rat (RHL-1 or rat hepatic lectin) and the mouse (MHL-1 or mouse hepatic lectin), which differ at only 12 positions in the amino acid sequence of their carbohydrate recognition domains, binds Siaα2,6GalNAcβ1,4GlcNAcβ1,2Man-bovine serum albumin and GalNAcβ1,4GlcNAcβ1,2Man-bovine serum albumin in ratios of 16:1.0 and 1.0:1.0, respectively. Mutagenesis was used to show that amino acids both in the immediate vicinity of the proposed binding site for terminal GalNAc and on the α2 helix that is distant from the binding site contribute to the specificity for terminal Siaα2,6GalNAc. Thus, multiple amino acid sequence alterations in two key locations contribute to the difference in specificity observed for the rat and mouse ASGP-Rs. We hypothesize that the altered specificity of ASPG-R orthologues in such evolutionarily closely related species reflects rapidly changing requirements for recognition of endogenous or exogenous oligosaccharides in vivo.
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rapid clearance of sialylated glycoproteins by the Asialoglycoprotein Receptor
Journal of Biological Chemistry, 2003Co-Authors: Eric I Park, Stephen M. Manzella, Jacques U. BaenzigerAbstract:Abstract The Asialoglycoprotein-Receptor (ASGP-R) located on liver parenchymal cells was originally identified and characterized on the basis of its ability to bind glycoproteins bearing terminal galactose (Gal) or N-acetylgalactosamine (GalNAc); however, endogenous ligands for the ASGP-R have not to date been definitively identified. We have determined that the rat ASGP-R specifically binds oligosaccharides terminating with the sequence Siaα2,6GalNAcβ1,4GlcNAcβ1,2Man. Bovine serum albumin chemically modified with 10–15 tetrasaccharides with the sequence Siaα2,6GalNAcβ1,4GlcNAcβ1,2Man is cleared from the blood of the rat with a half-life of <1 min by a Receptor located in the liver. We have isolated the Receptor and identified it as the ASGP-R. Furthermore, we have determined that subunit 1 of the ASGP-R accounts for the binding of terminal Siaα2,6GalNAcβ. Based on the newly defined specificity of the rat ASGP-R we hypothesize that glycoproteins bearing structures that are selectively modified with terminal Siaα2,6GalNAcβ and are released into the blood may be endogenous ligands for the rat ASGP-R.
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Rapid Clearance of Sialylated Glycoproteins by the Asialoglycoprotein Receptor
The Journal of biological chemistry, 2002Co-Authors: Eric I Park, Stephen M. Manzella, Jacques U. BaenzigerAbstract:The Asialoglycoprotein-Receptor (ASGP-R) located on liver parenchymal cells was originally identified and characterized on the basis of its ability to bind glycoproteins bearing terminal galactose (Gal) or N-acetylgalactosamine (GalNAc); however, endogenous ligands for the ASGP-R have not to date been definitively identified. We have determined that the rat ASGP-R specifically binds oligosaccharides terminating with the sequence Siaα2,6GalNAcβ1,4GlcNAcβ1,2Man. Bovine serum albumin chemically modified with 10–15 tetrasaccharides with the sequence Siaα2,6GalNAcβ1,4GlcNAcβ1,2Man is cleared from the blood of the rat with a half-life of
Istvan Toth - One of the best experts on this subject based on the ideXlab platform.
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A Drug Delivery Strategy: Binding Enkephalin to Asialoglycoprotein Receptor by Enzymatic
2016Co-Authors: Michelle P Christie, Waleed M Hussein, Mohamad F M Rawi, Michael P Jennings, Lauren E. Hartley-tassell, Christopher J. Day, Freda -c. E. Jen, Istvan TothAbstract:Glycosylation of biopharmaceuticals can mediate cell specific delivery by targeting carbohydrate Receptors. Additionally, glycosylation can improve the physico-chemical (drug-like) properties of peptide based drug candidates. The main purpose of this study was to examine if glycosylation of the peptide enkephalin could facilitate its binding to the carbohydrate Receptor, Asialoglycoprotein. Firstly, we described the one-pot enzymatic galactosylation of lactose modified enkephalin in the presence of uridine-59-diphosphogalactose 4-epimerase and lipopolysaccharyl a-1,4-galactosyltransferase. Stability experiments using human plasma and Caco-2 cell homogenates showed that glycosylation considerably improved the stability of enkephalin (at least 60 % remained stable after a 2 hr incubation at 37uC). In vitro permeability experiments using Caco-2 cells revealed that the permeability of mono- and trisaccharide conjugated enkephalins was 14 and 28 times higher, respectively, than that of enkephalin alone (Papp 3.161028 cm/s). By the methods of surface plasmon resonance and molecular modeling, we demonstrated that the enzymatic glycosylation of enkephalin enabled binding the Asialoglycoprotein Receptor. The addition of a trisaccharide moiety to enkephalin improved the binding of enkephalin to the Asialoglycoprotein Receptor two fold (KD = 91 mM). The docking scores from molecular modeling showed that the binding modes and affinities of the glycosylated enkephalin derivatives to the Asialoglycoprotein Receptor complemente
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a drug delivery strategy binding enkephalin to Asialoglycoprotein Receptor by enzymatic galactosylation
PLOS ONE, 2014Co-Authors: Michelle P Christie, Pavla Simerska, Waleed M Hussein, Mohamad F M Rawi, Lauren E Hartleytassell, Michael P Jennings, Istvan TothAbstract:Glycosylation of biopharmaceuticals can mediate cell specific delivery by targeting carbohydrate Receptors. Additionally, glycosylation can improve the physico-chemical (drug-like) properties of peptide based drug candidates. The main purpose of this study was to examine if glycosylation of the peptide enkephalin could facilitate its binding to the carbohydrate Receptor, Asialoglycoprotein. Firstly, we described the one-pot enzymatic galactosylation of lactose modified enkephalin in the presence of uridine-5'-diphosphogalactose 4-epimerase and lipopolysaccharyl alpha-1,4-galactosyltransferase. Stability experiments using human plasma and Caco-2 cell homogenates showed that glycosylation considerably improved the stability of enkephalin (at least 60% remained stable after a 2 hr incubation at 37 degrees C). In vitro permeability experiments using Caco-2 cells revealed that the permeability of mono-and trisaccharide conjugated enkephalins was 14 and 28 times higher, respectively, than that of enkephalin alone (Papp 3.1x10(-8) cm/s). By the methods of surface plasmon resonance and molecular modeling, we demonstrated that the enzymatic glycosylation of enkephalin enabled binding the Asialoglycoprotein Receptor. The addition of a trisaccharide moiety to enkephalin improved the binding of enkephalin to the Asialoglycoprotein Receptor two fold (K-D=91 mu M). The docking scores from molecular modeling showed that the binding modes and affinities of the glycosylated enkephalin derivatives to the Asialoglycoprotein Receptor complemented the results from the surface plasmon resonance experiments.
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A drug delivery strategy: binding enkephalin to Asialoglycoprotein Receptor by enzymatic galactosylation
PloS one, 2014Co-Authors: Michelle P Christie, Pavla Simerska, Waleed M Hussein, Mohamad F M Rawi, Michael P Jennings, Freda E.-c. Jen, Lauren E. Hartley-tassell, Christopher J. Day, Istvan TothAbstract:Glycosylation of biopharmaceuticals can mediate cell specific delivery by targeting carbohydrate Receptors. Additionally, glycosylation can improve the physico-chemical (drug-like) properties of peptide based drug candidates. The main purpose of this study was to examine if glycosylation of the peptide enkephalin could facilitate its binding to the carbohydrate Receptor, Asialoglycoprotein. Firstly, we described the one-pot enzymatic galactosylation of lactose modified enkephalin in the presence of uridine-5′-diphosphogalactose 4-epimerase and lipopolysaccharyl α-1,4-galactosyltransferase. Stability experiments using human plasma and Caco-2 cell homogenates showed that glycosylation considerably improved the stability of enkephalin (at least 60% remained stable after a 2 hr incubation at 37°C). In vitro permeability experiments using Caco-2 cells revealed that the permeability of mono- and trisaccharide conjugated enkephalins was 14 and 28 times higher, respectively, than that of enkephalin alone (Papp 3.1×10−8 cm/s). By the methods of surface plasmon resonance and molecular modeling, we demonstrated that the enzymatic glycosylation of enkephalin enabled binding the Asialoglycoprotein Receptor. The addition of a trisaccharide moiety to enkephalin improved the binding of enkephalin to the Asialoglycoprotein Receptor two fold (KD = 91 µM). The docking scores from molecular modeling showed that the binding modes and affinities of the glycosylated enkephalin derivatives to the Asialoglycoprotein Receptor complemented the results from the surface plasmon resonance experiments.
Beat Ernst - One of the best experts on this subject based on the ideXlab platform.
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trivalent gal galnac containing ligands designed for the Asialoglycoprotein Receptor
Bioorganic & Medicinal Chemistry, 2008Co-Authors: Oleg Khorev, Daniela Stokmaier, Brian Cutting, Oliver Schwardt, Beat ErnstAbstract:Abstract A series of novel, fluorescent ligands designed to bind with high affinity and specificity to the Asialoglycoprotein Receptor (ASGP-R) has been synthesized and tested on human liver cells. The compounds bear three non-reducing, β-linked Gal or Gal N Ac moieties linked to flexible spacers for an optimal spatial interaction with the binding site of the ASGP-R. The final constructs were selectively endocytosed by HepG2 cells derived from parenchymal liver cells—the major human liver cell type—in a process that was visualized with the aid of fluorescence microscopy. Furthermore, the internalization was analyzed with flow cytometry, which showed the process to be Receptor-mediated and selective. The compounds described in this work could serve as valuable tools for studying hepatic endocytosis, and are suited as carriers for site-specific drug delivery to the liver.
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trivalent gal galnac containing ligands designed for the Asialoglycoprotein Receptor
Bioorganic & Medicinal Chemistry, 2008Co-Authors: Oleg Khorev, Daniela Stokmaier, Brian Cutting, Oliver Schwardt, Beat ErnstAbstract:A series of novel, fluorescent ligands designed to bind with high affinity and specificity to the Asialoglycoprotein Receptor (ASGP-R) has been synthesized and tested on human liver cells. The compounds bear three non-reducing, beta-linked Gal or GalNAc moieties linked to flexible spacers for an optimal spatial interaction with the binding site of the ASGP-R. The final constructs were selectively endocytosed by HepG2 cells derived from parenchymal liver cells-the major human liver cell type-in a process that was visualized with the aid of fluorescence microscopy. Furthermore, the internalization was analyzed with flow cytometry, which showed the process to be Receptor-mediated and selective. The compounds described in this work could serve as valuable tools for studying hepatic endocytosis, and are suited as carriers for site-specific drug delivery to the liver.
Oleg Khorev - One of the best experts on this subject based on the ideXlab platform.
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design synthesis and evaluation of monovalent ligands for the Asialoglycoprotein Receptor asgp r
Bioorganic & Medicinal Chemistry, 2009Co-Authors: Daniela Stokmaier, Oleg Khorev, Brian Cutting, Rita Born, Daniel Ricklin, Thomas O G Ernst, Fabienne Boni, Kathrin Schwingruber, Martin Gentner, Matthias WittwerAbstract:A series of novel aryl-substituted triazolyl D-galactosamine derivatives was synthesized as ligands for the carbohydrate recognition domain of the major subunit H1 (H1-CRD) of the human Asialoglycoprotein Receptor (ASGP-R). The compounds were biologically evaluated with a newly developed competitive binding assay, surface plasmon resonance and by a competitive NMR binding experiment. With compound 1b, a new ligand with a twofold improved affinity to the best so far known D-GalNAc was identified. This small, drug-like ligand can be used as targeting device for drug delivery to hepatocytes.
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trivalent gal galnac containing ligands designed for the Asialoglycoprotein Receptor
Bioorganic & Medicinal Chemistry, 2008Co-Authors: Oleg Khorev, Daniela Stokmaier, Brian Cutting, Oliver Schwardt, Beat ErnstAbstract:Abstract A series of novel, fluorescent ligands designed to bind with high affinity and specificity to the Asialoglycoprotein Receptor (ASGP-R) has been synthesized and tested on human liver cells. The compounds bear three non-reducing, β-linked Gal or Gal N Ac moieties linked to flexible spacers for an optimal spatial interaction with the binding site of the ASGP-R. The final constructs were selectively endocytosed by HepG2 cells derived from parenchymal liver cells—the major human liver cell type—in a process that was visualized with the aid of fluorescence microscopy. Furthermore, the internalization was analyzed with flow cytometry, which showed the process to be Receptor-mediated and selective. The compounds described in this work could serve as valuable tools for studying hepatic endocytosis, and are suited as carriers for site-specific drug delivery to the liver.
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trivalent gal galnac containing ligands designed for the Asialoglycoprotein Receptor
Bioorganic & Medicinal Chemistry, 2008Co-Authors: Oleg Khorev, Daniela Stokmaier, Brian Cutting, Oliver Schwardt, Beat ErnstAbstract:A series of novel, fluorescent ligands designed to bind with high affinity and specificity to the Asialoglycoprotein Receptor (ASGP-R) has been synthesized and tested on human liver cells. The compounds bear three non-reducing, beta-linked Gal or GalNAc moieties linked to flexible spacers for an optimal spatial interaction with the binding site of the ASGP-R. The final constructs were selectively endocytosed by HepG2 cells derived from parenchymal liver cells-the major human liver cell type-in a process that was visualized with the aid of fluorescence microscopy. Furthermore, the internalization was analyzed with flow cytometry, which showed the process to be Receptor-mediated and selective. The compounds described in this work could serve as valuable tools for studying hepatic endocytosis, and are suited as carriers for site-specific drug delivery to the liver.
