The Experts below are selected from a list of 216 Experts worldwide ranked by ideXlab platform
Joseph Sodroski - One of the best experts on this subject based on the ideXlab platform.
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Subunit Stoichiometry of Human Immunodeficiency Virus Type 1 Envelope Glycoprotein Trimers during Virus Entry into Host Cells
Journal of Virology, 2006Co-Authors: Xinzhen Yang, Svetla Kurteva, Joseph SodroskiAbstract:The envelope Glycoproteins of human immunodeficiency virus type 1 (HIV-1) function as a homotrimer of gp120/gp41 heterodimers to support virus entry. During the process of virus entry, an individual HIV-1 envelope glycoprotein trimer binds the cellular receptors CD4 and CCR5/CXCR4 and mediates the fusion of the viral and the target cellular membranes. By studying the function of heterotrimers between wild-type and nonfunctional mutant envelope Glycoproteins, we found that two wild-type subunits within an envelope glycoprotein trimer are required to support virus entry. Complementation between HIV-1 envelope glycoprotein mutants defective in different functions to allow virus entry was not evident. These results assist our understanding of the mechanisms whereby the HIV-1 envelope Glycoproteins mediate virus entry and membrane fusion and guide attempts to inhibit these processes.
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highly stable trimers formed by human immunodeficiency virus type 1 envelope Glycoproteins fused with the trimeric motif of t4 bacteriophage fibritin
Journal of Virology, 2002Co-Authors: Xinzhen Yang, Juliette Lee, Erin Mahony, Peter D Kwong, Richard T Wyatt, Joseph SodroskiAbstract:The envelope Glycoproteins of human immunodeficiency virus type 1 (HIV-1) function as a trimer composed of three gp120 exterior Glycoproteins and three gp41 transmembrane proteins. Soluble gp140 Glycoproteins composed of the uncleaved ectodomains of gp120 and gp41 form unstable, heterogeneous oligomers, but soluble gp140 trimers can be stabilized by fusion with a C-terminal, trimeric GCN4 motif (X. Yang et al., J. Virol. 74:5716-5725, 2000). To understand the influence of the C-terminal trimerization domain on the properties of soluble HIV-1 envelope glycoprotein trimers, uncleaved, soluble gp140 Glycoproteins were stabilized by fusion with another trimeric motif derived from T4 bacteriophage fibritin. The fibritin construct was more stable to heat and reducing conditions than the GCN4 construct. Both GCN4- and fibritin-stabilized soluble gp140 Glycoproteins exhibited patterns of neutralizing and nonneutralizing antibody binding expected for the functional envelope glycoprotein spike. Of note, two potently neutralizing antibodies, immunoglobulin G1b12 and 2G12, exhibited the greatest recognition of the stabilized, soluble trimers, relative to recognition of the gp120 monomer. The observed similarities between the GCN4 and fibritin constructs indicate that the HIV-1 envelope glycoprotein ectodomains dictate many of the antigenic and structural features of these fusion proteins. The melting temperatures and ligand recognition properties of the GCN4- and fibritin-stabilized soluble gp140 Glycoproteins suggest that these molecules assume conformations distinct from that of the fusion-active, six-helix bundle.
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replicative function and neutralization sensitivity of envelope Glycoproteins from primary and t cell line passaged human immunodeficiency virus type 1 isolates
Journal of Virology, 1995Co-Authors: Nancy Sullivan, J Li, Wolfgang Hofmann, Joseph SodroskiAbstract:The structure, replicative properties, and sensitivity to neutralization by soluble CD4 and monoclonal antibodies were examined for molecularly cloned envelope Glycoproteins derived from human immunodeficiency virus type 1 (HIV-1) viruses either isolated directly from patients or passaged in T-cell lines. Complementation of virus entry into peripheral blood mononuclear cell targets by primary patient envelope Glycoproteins exhibited efficiencies ranging from that observed for the HXBc2 envelope Glycoproteins, which are derived from a T-cell line-passaged virus, to approximately fivefold-lower values. The ability of the envelope Glycoproteins to complement virus entry roughly correlated with sensitivity to neutralization by soluble CD4. Laboratory-adapted viruses were sensitive to neutralization by monoclonal antibodies directed against the CD4-binding site and the third variable (V3) loop of the gp120 glycoprotein. By comparison, viruses with envelope Glycoproteins from primary patient isolates exhibited decreased sensitivity to neutralization by these monoclonal antibodies; for these viruses, neutralization sensitivity correlated with replicative ability. Subinhibitory concentrations of soluble CD4 and a CD4-binding site-directed antibody significantly enhanced the entry of viruses containing envelope Glycoproteins from some primary patient isolates. The sensitivity of viruses containing the different envelope Glycoproteins to neutralization by soluble CD4 or monoclonal antibodies could be predicted by assays dependent on the binding of the inhibitory molecule to the oligomeric envelope glycoprotein complex but less well by assays measuring binding to the monomeric gp120 glycoprotein. These results indicate that the intrinsic structure of the oligomeric envelope glycoprotein complex of primary HIV-1 isolates, while often less than optimal with respect to the mediation of early events in virus replication, allows a relative degree of resistance to neutralizing antibodies. The interplay of selective forces for higher virus replication efficiency and resistance to neutralizing antibodies could explain the temporal course described for the in vivo emergence of HIV-1 isolates with differing phenotypes.
Yasuhiro Kajihara - One of the best experts on this subject based on the ideXlab platform.
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monitoring of glycoprotein quality control system with a series of chemically synthesized homogeneous native and misfolded Glycoproteins
Journal of the American Chemical Society, 2018Co-Authors: Tatsuto Kiuchi, Masayuki Izumi, Akira Seko, Masafumi Sakono, Ryo Okamoto, Yuki Mukogawa, Arisa Shimada, Yoichi Takeda, Yasuhiro KajiharaAbstract:The glycoprotein quality control (GQC) system in the endoplasmic reticulum (ER) effectively uses chaperone-type enzymes and lectins such as UDP-glucose:glycoprotein glucosyltransferase (UGGT), calnexin (CNX), calreticulin (CRT), protein disulfide bond isomerases (ERp57 or PDIs), and glucosidases to generate native-folded Glycoproteins from nascent glycopolypeptides. However, the individual processes of the GQC system at the molecular level are still unclear. We chemically synthesized a series of several homogeneous Glycoproteins bearing M9-high-mannose type oligosaccharides (M9-glycan), such as erythropoietin (EPO), interferon-β (IFN-β), and interleukin 8 (IL8) and their misfolded counterparts, and used these glycoprotein probes to better understand the GQC process. The analyses by high performance liquid chromatography and mass spectrometer clearly showed refolding processes from synthetic misfolded Glycoproteins to native form through folding intermediates, allowing for the relationship between the amou...
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chemical synthesis of homogeneous Glycoproteins for the study of glycoprotein quality control system
Israel Journal of Chemistry, 2015Co-Authors: Masayuki Izumi, Simone Dedola, Yasuhiro KajiharaAbstract:The glycoprotein quality control system exists in the endoplasmic reticulum to maintain protein homeostasis and prevent accumulation of aberrant Glycoproteins. Folding sensor enzyme uridine diphosphate (UDP)glucose : glycoprotein glucosyltransferase (UGGT) plays an important role in this system through its ability to discriminate immature or misfolded Glycoproteins from native ones. UGGT transfers a glucose residue to a glycoprotein containing Man9GlcNAc2 (M9; Man=mannose, GlcNAc=N-acetyl-D-glucosamine) N-glycan only when the glycoprotein has not attained a native form. We chemically prepared homogeneous Glycoproteins containing M9 N-glycan in the native form as well as in misfolded forms and examined them as substrates of UGGT. Glucose transfer to misfolded Glycoproteins was clearly observed by LC-MS, but Glycoproteins in the native form were barely glucosylated. Furthermore, we constructed an in vitro glycoprotein folding system in the presence of UGGT and found out that all folding intermediates which appeared during folding were also glucosylated. Through these experiments, we demonstrated the usefulness of chemically synthesized homogeneous Glycoproteins as probes to gain insights into the molecular basis of the glycoprotein quality control system.
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Chemical Synthesis of Homogeneous Glycoproteins
Glycoscience: Biology and Medicine, 2014Co-Authors: Masayuki Izumi, Ryo Okamoto, Yasuhiro KajiharaAbstract:Oligosaccharides of glycoprotein are known to be heterogeneous. These diverse oligosaccharide profiles have been a hindrance to elucidating oligosaccharide functions in many biological events. In order to elucidate oligosaccharide functions, Glycoproteins having homogeneous oligosaccharides that can be varied as much as chemists like are requisite. Chemical synthesis of Glycoproteins recently emerged and provides homogeneous Glycoproteins such as erythropoietin. For this purpose, an efficient preparation of complex-type oligosaccharides, solid-phase glycopeptide synthesis, glycopeptide segment coupling, and glycopeptide folding procedure are essential. This chapter introduces typical procedure for the chemical synthesis of homogeneous glycoprotein.
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Folding of Synthetic Homogeneous Glycoproteins in the Presence of a Glycoprotein Folding Sensor Enzyme
Angewandte Chemie, 2014Co-Authors: Simone Dedola, Masayuki Izumi, Yutaka Makimura, Akira Seko, Akiko Kanamori, Masafumi Sakono, Yukishige Ito, Yasuhiro KajiharaAbstract:UDP-glucose:glycoprotein glucosyltransferase (UGGT) plays a key role in recognizing folded and misfolded Glycoproteins in the glycoprotein quality control system of the endoplasmic reticulum. UGGT detects misfolded Glycoproteins and re-glucosylates them as a tag for misfolded Glycoproteins. A flexible model to reproduce in vitro folding of a glycoprotein in the presence of UGGT in a mixture containing correctly folded, folding intermediates, and misfolded Glycoproteins is described. The data demonstrates that UGGT can re-glucosylate all intermediates in the in vitro folding experiments, thus indicating that UGGT inspects not only final folded products, but also the glycoprotein folding intermediates.
Masayuki Izumi - One of the best experts on this subject based on the ideXlab platform.
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monitoring of glycoprotein quality control system with a series of chemically synthesized homogeneous native and misfolded Glycoproteins
Journal of the American Chemical Society, 2018Co-Authors: Tatsuto Kiuchi, Masayuki Izumi, Akira Seko, Masafumi Sakono, Ryo Okamoto, Yuki Mukogawa, Arisa Shimada, Yoichi Takeda, Yasuhiro KajiharaAbstract:The glycoprotein quality control (GQC) system in the endoplasmic reticulum (ER) effectively uses chaperone-type enzymes and lectins such as UDP-glucose:glycoprotein glucosyltransferase (UGGT), calnexin (CNX), calreticulin (CRT), protein disulfide bond isomerases (ERp57 or PDIs), and glucosidases to generate native-folded Glycoproteins from nascent glycopolypeptides. However, the individual processes of the GQC system at the molecular level are still unclear. We chemically synthesized a series of several homogeneous Glycoproteins bearing M9-high-mannose type oligosaccharides (M9-glycan), such as erythropoietin (EPO), interferon-β (IFN-β), and interleukin 8 (IL8) and their misfolded counterparts, and used these glycoprotein probes to better understand the GQC process. The analyses by high performance liquid chromatography and mass spectrometer clearly showed refolding processes from synthetic misfolded Glycoproteins to native form through folding intermediates, allowing for the relationship between the amou...
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chemical synthesis of homogeneous Glycoproteins for the study of glycoprotein quality control system
Israel Journal of Chemistry, 2015Co-Authors: Masayuki Izumi, Simone Dedola, Yasuhiro KajiharaAbstract:The glycoprotein quality control system exists in the endoplasmic reticulum to maintain protein homeostasis and prevent accumulation of aberrant Glycoproteins. Folding sensor enzyme uridine diphosphate (UDP)glucose : glycoprotein glucosyltransferase (UGGT) plays an important role in this system through its ability to discriminate immature or misfolded Glycoproteins from native ones. UGGT transfers a glucose residue to a glycoprotein containing Man9GlcNAc2 (M9; Man=mannose, GlcNAc=N-acetyl-D-glucosamine) N-glycan only when the glycoprotein has not attained a native form. We chemically prepared homogeneous Glycoproteins containing M9 N-glycan in the native form as well as in misfolded forms and examined them as substrates of UGGT. Glucose transfer to misfolded Glycoproteins was clearly observed by LC-MS, but Glycoproteins in the native form were barely glucosylated. Furthermore, we constructed an in vitro glycoprotein folding system in the presence of UGGT and found out that all folding intermediates which appeared during folding were also glucosylated. Through these experiments, we demonstrated the usefulness of chemically synthesized homogeneous Glycoproteins as probes to gain insights into the molecular basis of the glycoprotein quality control system.
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Chemical Synthesis of Homogeneous Glycoproteins
Glycoscience: Biology and Medicine, 2014Co-Authors: Masayuki Izumi, Ryo Okamoto, Yasuhiro KajiharaAbstract:Oligosaccharides of glycoprotein are known to be heterogeneous. These diverse oligosaccharide profiles have been a hindrance to elucidating oligosaccharide functions in many biological events. In order to elucidate oligosaccharide functions, Glycoproteins having homogeneous oligosaccharides that can be varied as much as chemists like are requisite. Chemical synthesis of Glycoproteins recently emerged and provides homogeneous Glycoproteins such as erythropoietin. For this purpose, an efficient preparation of complex-type oligosaccharides, solid-phase glycopeptide synthesis, glycopeptide segment coupling, and glycopeptide folding procedure are essential. This chapter introduces typical procedure for the chemical synthesis of homogeneous glycoprotein.
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Folding of Synthetic Homogeneous Glycoproteins in the Presence of a Glycoprotein Folding Sensor Enzyme
Angewandte Chemie, 2014Co-Authors: Simone Dedola, Masayuki Izumi, Yutaka Makimura, Akira Seko, Akiko Kanamori, Masafumi Sakono, Yukishige Ito, Yasuhiro KajiharaAbstract:UDP-glucose:glycoprotein glucosyltransferase (UGGT) plays a key role in recognizing folded and misfolded Glycoproteins in the glycoprotein quality control system of the endoplasmic reticulum. UGGT detects misfolded Glycoproteins and re-glucosylates them as a tag for misfolded Glycoproteins. A flexible model to reproduce in vitro folding of a glycoprotein in the presence of UGGT in a mixture containing correctly folded, folding intermediates, and misfolded Glycoproteins is described. The data demonstrates that UGGT can re-glucosylate all intermediates in the in vitro folding experiments, thus indicating that UGGT inspects not only final folded products, but also the glycoprotein folding intermediates.
Xinzhen Yang - One of the best experts on this subject based on the ideXlab platform.
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Subunit Stoichiometry of Human Immunodeficiency Virus Type 1 Envelope Glycoprotein Trimers during Virus Entry into Host Cells
Journal of Virology, 2006Co-Authors: Xinzhen Yang, Svetla Kurteva, Joseph SodroskiAbstract:The envelope Glycoproteins of human immunodeficiency virus type 1 (HIV-1) function as a homotrimer of gp120/gp41 heterodimers to support virus entry. During the process of virus entry, an individual HIV-1 envelope glycoprotein trimer binds the cellular receptors CD4 and CCR5/CXCR4 and mediates the fusion of the viral and the target cellular membranes. By studying the function of heterotrimers between wild-type and nonfunctional mutant envelope Glycoproteins, we found that two wild-type subunits within an envelope glycoprotein trimer are required to support virus entry. Complementation between HIV-1 envelope glycoprotein mutants defective in different functions to allow virus entry was not evident. These results assist our understanding of the mechanisms whereby the HIV-1 envelope Glycoproteins mediate virus entry and membrane fusion and guide attempts to inhibit these processes.
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highly stable trimers formed by human immunodeficiency virus type 1 envelope Glycoproteins fused with the trimeric motif of t4 bacteriophage fibritin
Journal of Virology, 2002Co-Authors: Xinzhen Yang, Juliette Lee, Erin Mahony, Peter D Kwong, Richard T Wyatt, Joseph SodroskiAbstract:The envelope Glycoproteins of human immunodeficiency virus type 1 (HIV-1) function as a trimer composed of three gp120 exterior Glycoproteins and three gp41 transmembrane proteins. Soluble gp140 Glycoproteins composed of the uncleaved ectodomains of gp120 and gp41 form unstable, heterogeneous oligomers, but soluble gp140 trimers can be stabilized by fusion with a C-terminal, trimeric GCN4 motif (X. Yang et al., J. Virol. 74:5716-5725, 2000). To understand the influence of the C-terminal trimerization domain on the properties of soluble HIV-1 envelope glycoprotein trimers, uncleaved, soluble gp140 Glycoproteins were stabilized by fusion with another trimeric motif derived from T4 bacteriophage fibritin. The fibritin construct was more stable to heat and reducing conditions than the GCN4 construct. Both GCN4- and fibritin-stabilized soluble gp140 Glycoproteins exhibited patterns of neutralizing and nonneutralizing antibody binding expected for the functional envelope glycoprotein spike. Of note, two potently neutralizing antibodies, immunoglobulin G1b12 and 2G12, exhibited the greatest recognition of the stabilized, soluble trimers, relative to recognition of the gp120 monomer. The observed similarities between the GCN4 and fibritin constructs indicate that the HIV-1 envelope glycoprotein ectodomains dictate many of the antigenic and structural features of these fusion proteins. The melting temperatures and ligand recognition properties of the GCN4- and fibritin-stabilized soluble gp140 Glycoproteins suggest that these molecules assume conformations distinct from that of the fusion-active, six-helix bundle.
Richard T Wyatt - One of the best experts on this subject based on the ideXlab platform.
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highly stable trimers formed by human immunodeficiency virus type 1 envelope Glycoproteins fused with the trimeric motif of t4 bacteriophage fibritin
Journal of Virology, 2002Co-Authors: Xinzhen Yang, Juliette Lee, Erin Mahony, Peter D Kwong, Richard T Wyatt, Joseph SodroskiAbstract:The envelope Glycoproteins of human immunodeficiency virus type 1 (HIV-1) function as a trimer composed of three gp120 exterior Glycoproteins and three gp41 transmembrane proteins. Soluble gp140 Glycoproteins composed of the uncleaved ectodomains of gp120 and gp41 form unstable, heterogeneous oligomers, but soluble gp140 trimers can be stabilized by fusion with a C-terminal, trimeric GCN4 motif (X. Yang et al., J. Virol. 74:5716-5725, 2000). To understand the influence of the C-terminal trimerization domain on the properties of soluble HIV-1 envelope glycoprotein trimers, uncleaved, soluble gp140 Glycoproteins were stabilized by fusion with another trimeric motif derived from T4 bacteriophage fibritin. The fibritin construct was more stable to heat and reducing conditions than the GCN4 construct. Both GCN4- and fibritin-stabilized soluble gp140 Glycoproteins exhibited patterns of neutralizing and nonneutralizing antibody binding expected for the functional envelope glycoprotein spike. Of note, two potently neutralizing antibodies, immunoglobulin G1b12 and 2G12, exhibited the greatest recognition of the stabilized, soluble trimers, relative to recognition of the gp120 monomer. The observed similarities between the GCN4 and fibritin constructs indicate that the HIV-1 envelope glycoprotein ectodomains dictate many of the antigenic and structural features of these fusion proteins. The melting temperatures and ligand recognition properties of the GCN4- and fibritin-stabilized soluble gp140 Glycoproteins suggest that these molecules assume conformations distinct from that of the fusion-active, six-helix bundle.