Journal articles on the topic 'Glycoproteins Receptors'
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1
Garner, Omai B., and Linda G. Baum. "Galectin–glycan lattices regulate cell-surface glycoprotein organization and signalling." Biochemical Society Transactions 36, no. 6 (November 19, 2008): 1472–77. http://dx.doi.org/10.1042/bst0361472.
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The formation of multivalent complexes of soluble galectins with glycoprotein receptors on the plasma membrane helps to organize glycoprotein assemblies on the surface of the cell. In some cell types, this formation of galectin–glycan lattices or scaffolds is critical for organizing plasma membrane domains, such as lipid rafts, or for targeted delivery of glycoproteins to the apical or basolateral surface. Galectin–glycan lattice formation is also involved in regulating the signalling threshold of some cell-surface glycoproteins, including T-cell receptors and growth factor receptors. Finally, galectin–glycan lattices can determine receptor residency time by inhibiting endocytosis of glycoprotein receptors from the cell surface, thus modulating the magnitude or duration of signalling from the cell surface. This paper reviews recent evidence in vitro and in vivo for critical physiological and cellular functions that are regulated by galectin–glycoprotein interactions.
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Dupuis, Gilles, and Marc Letellier. "Functional incorporation and preferred orientation of phytohemagglutinin receptor glycoproteins in phospholipid vesicles." Biochemistry and Cell Biology 65, no. 2 (February 1, 1987): 120–29. http://dx.doi.org/10.1139/o87-017.
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Porcine lymphocyte Phaseolus vulgaris phytohemagglutinin (PHA) receptor glycoproteins purified by affinity chromatography have been reassembled into vesicles made of phosphatidylcholine and phosphatidylserine by detergent (dodecyltrimethylammonium bromide) dialysis. The receptor glycoproteins were incorporated into the lipid vesicles in a nonselective manner with a yield of 65–70%. Vesicles containing the glycoproteins were sealed as evidenced by their impermeability to calcium ions, using quin 2 trapped inside the vesicles. The vesicles were agglutinated by PHA, suggesting that the saccharidic moiety of the reconstituted glycoproteins was, at least in part, oriented towads the extravesicular medium. This observation was further supported by the fact that the vesicles bound 125I-labeled PHA in a specific and saturable manner. At maximum amount of lectin bound, a ratio of 1.01 ± 0.05 μg of PHA per microgram glycoprotein incorporated was measured. When the binding data were analyzed by Scatchard plot, a downward concave profile was observed, suggestive of a positive cooperativity at low concentrations of lectin. The orientation of the reconstituted lectin receptor glycoproteins was determined by proteolytic treatments of labeled glycoproteins. The combined action of trypsin and chymotrypsin released, in the 120 000 × g supernatant, approximately 80% of label when 125I-tagged PHA receptor glycoproteins were incorporated into the vesicles. When the oligosaccharidic moieties of the receptor glycoproteins were specifically labeled, the simultaneous action of the two enzymes released approximately 70% of tritium labeling present in the reconstituted system. Taken together, these results suggest that the reconstituted PHA receptors are preferentially oriented into the phospholipid vesicles. The reconstituted PHA receptor glycoproteins competed effectively with cellular receptors in the assay of PHA-induced porcine lymphocyte activation. A 50% inhibition of [3H]thymidine incorporation was observed when 1 μg of glycoproteins in vesicles was added to the cultured cells, whereas vesicles alone had no effect at this (equivalent) concentration.
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Wessner, David R., Paul C. Shick, Jin-Hua Lu, Christine B. Cardellichio, Sara E. Gagneten, Nicole Beauchemin, Kathryn V. Holmes, and Gabriela S. Dveksler. "Mutational Analysis of the Virus and Monoclonal Antibody Binding Sites in MHVR, the Cellular Receptor of the Murine Coronavirus Mouse Hepatitis Virus Strain A59." Journal of Virology 72, no. 3 (March 1, 1998): 1941–48. http://dx.doi.org/10.1128/jvi.72.3.1941-1948.1998.
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ABSTRACT The primary cellular receptor for mouse hepatitis virus (MHV), a murine coronavirus, is MHVR (also referred to as Bgp1a or C-CAM), a transmembrane glycoprotein with four immunoglobulin-like domains in the murine biliary glycoprotein (Bgp) subfamily of the carcinoembryonic antigen (CEA) family. Other murine glycoproteins in the Bgp subfamily, including Bgp1b and Bgp2, also can serve as MHV receptors when transfected into MHV-resistant cells. Previous studies have shown that the 108-amino-acid N-terminal domain of MHVR is essential for virus receptor activity and is the binding site for monoclonal antibody (MAb) CC1, an antireceptor MAb that blocks MHV infection in vivo and in vitro. To further elucidate the regions of MHVR required for virus receptor activity and MAb CC1 binding, we constructed chimeras between MHVR and other members of the CEA family and tested them for MHV strain A59 (MHV-A59) receptor activity and MAb CC1 binding activity. In addition, we used site-directed mutagenesis to introduce selected amino acid changes into the N-terminal domains of MHVR and these chimeras and tested the abilities of these mutant glycoproteins to bind MAb CC1 and to function as MHV receptors. Several recombinant glycoproteins exhibited virus receptor activity but did not bind MAb CC1, indicating that the virus and MAb binding sites on the N-terminal domain of MHVR are not identical. Analysis of the recombinant glycoproteins showed that a short region of MHVR, between amino acids 34 and 52, is critical for MHV-A59 receptor activity. Additional regions of the N-terminal variable domain and the constant domains, however, greatly affected receptor activity. Thus, the molecular context in which the amino acids critical for MHV-A59 receptor activity are found profoundly influences the virus receptor activity of the glycoprotein.
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Morimoto, Kanta, Noriko Suzuki, Isei Tanida, Soichiro Kakuta, Yoko Furuta, Yasuo Uchiyama, Kentaro Hanada, Yusuke Suzuki, and Toshiyuki Yamaji. "Blood group P1 antigen–bearing glycoproteins are functional but less efficient receptors of Shiga toxin than conventional glycolipid-based receptors." Journal of Biological Chemistry 295, no. 28 (May 14, 2020): 9490–501. http://dx.doi.org/10.1074/jbc.ra120.013926.
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Shiga toxin (STx) is a virulence factor produced by enterohemorrhagic Escherichia coli. STx is taken up by mammalian host cells by binding to the glycosphingolipid (GSL) globotriaosylceramide (Gb3; Galα1-4Galβ1-4Glc-ceramide) and causes cell death after its retrograde membrane transport. However, the contribution of the hydrophobic portion of Gb3 (ceramide) to STx transport remains unclear. In pigeons, blood group P1 glycan antigens (Galα1-4Galβ1-4GlcNAc-) are expressed on glycoproteins that are synthesized by α1,4-galactosyltransferase 2 (pA4GalT2). To examine whether these glycoproteins can also function as STx receptors, here we constructed glycan-remodeled HeLa cell variants lacking Gb3 expression but instead expressing pA4GalT2-synthesized P1 glycan antigens on glycoproteins. We compared STx binding and sensitivity of these variants with those of the parental, Gb3-expressing HeLa cells. The glycan-remodeled cells bound STx1 via N-glycans of glycoproteins and were sensitive to STx1 even without Gb3 expression, indicating that P1-containing glycoproteins also function as STx receptors. However, these variants were significantly less sensitive to STx than the parent cells. Fluorescence microscopy and correlative light EM revealed that the STx1 B subunit accumulates to lower levels in the Golgi apparatus after glycoprotein-mediated than after Gb3-mediated uptake but instead accumulates in vacuole-like structures probably derived from early endosomes. Furthermore, coexpression of Galα1-4Gal on both glycoproteins and GSLs reduced the sensitivity of cells to STx1 compared with those expressing Galα1-4Gal only on GSLs, probably because of competition for STx binding or internalization. We conclude that lipid-based receptors are much more effective in STx retrograde transport and mediate greater STx cytotoxicity than protein-based receptors.
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Melder, Deborah C., Gennett M. Pike, Matthew W. VanBrocklin, and Mark J. Federspiel. "Model of the TVA Receptor Determinants Required for Efficient Infection by Subgroup A Avian Sarcoma and Leukosis Viruses." Journal of Virology 89, no. 4 (December 3, 2014): 2136–48. http://dx.doi.org/10.1128/jvi.02339-14.
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ABSTRACTThe study of the interactions of subgroup A avian sarcoma and leucosis viruses [ASLV(A)] with the TVA receptor required to infect cells offers a powerful experimental model of retroviral entry. Several regions and specific residues in the TVA receptor have previously been identified to be critical determinants of the binding affinity with ASLV(A) envelope glycoproteins and to mediate efficient infection. Two homologs of the TVA receptor have been cloned: the original quail TVA receptor, which has been the basis for most of the initial characterization of the ASLV(A) TVA, and the chicken TVA receptor, which is 65% identical to the quail receptor overall but identical in the region thought to be critical for infection. Our previous work characterized three mutant ASLV(A) isolates that could efficiently bind and infect cells using the chicken TVA receptor homolog but not using the quail TVA receptor homolog, with the infectivity of one mutant virus being >500-fold less with the quail TVA receptor. The mutant viruses contained mutations in the hr1 region of the surface glycoprotein. Using chimeras of the quail and chicken TVA receptors, we have identified new residues of TVA critical for the binding affinity and entry of ASLV(A) using the mutant glycoproteins and viruses to probe the function of those residues. The quail TVA receptor required changes at residues 10, 14, and 31 of the corresponding chicken TVA residues to bind wild-type and mutant ASLV(A) glycoproteins with a high affinity and recover the ability to mediate efficient infection of cells. A model of the TVA determinants critical for interacting with ASLV(A) glycoproteins is proposed.IMPORTANCEA detailed understanding of how retroviruses enter cells, evolve to use new receptors, and maintain efficient entry is crucial for identifying new targets for combating retrovirus infection and pathogenesis, as well as for developing new approaches for targeted gene delivery. Since all retroviruses share an envelope glycoprotein organization, they likely share a mechanism of receptor triggering to begin the entry process. Multiple, noncontiguous interaction determinants located in the receptor and the surface (SU) glycoprotein hypervariable domains are required for binding affinity and to restrict or broaden receptor usage. In this study, further mechanistic details of the entry process were elucidated by characterizing the ASLV(A) glycoprotein interactions with the TVA receptor required for entry. The ASLV(A) envelope glycoproteins are organized into functional domains that allow changes in receptor choice to occur by mutation and/or recombination while maintaining a critical level of receptor binding affinity and an ability to trigger glycoprotein conformational changes.
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Kolchinsky, Peter, Enko Kiprilov, and Joseph Sodroski. "Increased Neutralization Sensitivity of CD4-Independent Human Immunodeficiency Virus Variants." Journal of Virology 75, no. 5 (March 1, 2001): 2041–50. http://dx.doi.org/10.1128/jvi.75.5.2041-2050.2001.
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ABSTRACT Naturally occurring human immunodeficiency virus (HIV-1) variants require the presence of CD4 and specific chemokine receptors to enter a cell. In the laboratory, HIV-1 variants that are capable of bypassing CD4 and utilizing only the CCR5 chemokine receptor for virus entry have been generated. Here we report that these CD4-independent viruses are significantly more sensitive to neutralization by soluble CD4 and a variety of antibodies. The same amino acid changes in the HIV-1 gp120 envelope glycoprotein determined CD4 independence and neutralization sensitivity. The CD4-independent envelope glycoproteins exhibited higher affinity for antibodies against CD4-induced gp120 epitopes but not other neutralizing ligands. The CD4-independent envelope glycoproteins did not exhibit increased lability relative to the wild-type envelope glycoproteins. The utilization of two receptors apparently allows HIV-1 to maintain a more neutralization-resistant state prior to engaging CD4 on the target cell, explaining the rarity of CD4 independence in wild-type HIV-1.
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Bowden, Thomas A., Max Crispin, E. Yvonne Jones, and David I. Stuart. "Shared paramyxoviral glycoprotein architecture is adapted for diverse attachment strategies." Biochemical Society Transactions 38, no. 5 (September 24, 2010): 1349–55. http://dx.doi.org/10.1042/bst0381349.
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Members within the paramyxovirus subfamily Paramyxovirinae constitute a large number of highly virulent human and animal pathogens. The glycoproteins present on these viruses are responsible for mediating host cell attachment and fusion and are key targets for the design of antiviral entry inhibitors. In the present review, we discuss recent structural studies which have led to a better understanding of the various mechanisms by which different paramyxoviruses use their attachment glycoproteins to hijack specific protein and glycan cell-surface receptors to facilitate viral entry. It is observed that the paramyxovirus attachment glycoprotein consists of a conserved overall structure which includes an N-terminal six-bladed β-propeller domain which is responsible for cell receptor binding. Crystal structures of this domain from different biomedically important paramyxoviruses, including measles, Nipah, Hendra, Newcastle disease and parainfluenza viruses, alone and in complex with their functional cell-surface receptors, demonstrate three contrasting mechanisms of receptor engagement that paramyxoviruses have evolved to confer discreet protein- and glycan-receptor specificity. This structural information highlights the adaptability of the paramyxovirus attachment glycoprotein surface and the potential for the emergence of new and potentially harmful viruses in human hosts.
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Federspiel, Mark J. "Reverse Engineering Provides Insights on the Evolution of Subgroups A to E Avian Sarcoma and Leukosis Virus Receptor Specificity." Viruses 11, no. 6 (May 30, 2019): 497. http://dx.doi.org/10.3390/v11060497.
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The initial step of retrovirus entry—the interaction between the virus envelope glycoprotein trimer and a cellular receptor—is complex, involving multiple, noncontiguous determinants in both proteins that specify receptor choice, binding affinity and the ability to trigger conformational changes in the viral glycoproteins. Despite the complexity of this interaction, retroviruses have the ability to evolve the structure of their envelope glycoproteins to use a different cellular protein as receptors. The highly homologous subgroup A to E Avian Sarcoma and Leukosis Virus (ASLV) glycoproteins belong to the group of class 1 viral fusion proteins with a two-step triggering mechanism that allows experimental access to intermediate structures during the fusion process. We and others have taken advantage of replication-competent ASLVs and exploited genetic selection strategies to force the ASLVs to naturally evolve and acquire envelope glycoprotein mutations to escape the pressure on virus entry and still yield a functional replicating virus. This approach allows for the simultaneous selection of multiple mutations in multiple functional domains of the envelope glycoprotein that may be required to yield a functional virus. Here, we review the ASLV family and experimental system and the reverse engineering approaches used to understand the evolution of ASLV receptor usage.
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Zhao, Xuesen, Fang Guo, Mary Ann Comunale, Anand Mehta, Mohit Sehgal, Pooja Jain, Andrea Cuconati, et al. "Inhibition of Endoplasmic Reticulum-Resident Glucosidases Impairs Severe Acute Respiratory Syndrome Coronavirus and Human Coronavirus NL63 Spike Protein-Mediated Entry by Altering the Glycan Processing of Angiotensin I-Converting Enzyme 2." Antimicrobial Agents and Chemotherapy 59, no. 1 (October 27, 2014): 206–16. http://dx.doi.org/10.1128/aac.03999-14.
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ABSTRACTEndoplasmic reticulum (ER)-resident glucosidases I and II sequentially trim the three terminal glucose moieties on the N-linked glycans attached to nascent glycoproteins. These reactions are the first steps of N-linked glycan processing and are essential for proper folding and function of many glycoproteins. Because most of the viral envelope glycoproteins contain N-linked glycans, inhibition of ER glucosidases with derivatives of 1-deoxynojirimycin, i.e., iminosugars, efficiently disrupts the morphogenesis of a broad spectrum of enveloped viruses. However, like viral envelope proteins, the cellular receptors of many viruses are also glycoproteins. It is therefore possible that inhibition of ER glucosidases not only compromises virion production but also disrupts expression and function of viral receptors and thus inhibits virus entry into host cells. Indeed, we demonstrate here that iminosugar treatment altered the N-linked glycan structure of angiotensin I-converting enzyme 2 (ACE2), which did not affect its expression on the cell surface or its binding of the severe acute respiratory syndrome coronavirus (SARS-CoV) spike glycoprotein. However, alteration of N-linked glycans of ACE2 impaired its ability to support the transduction of SARS-CoV and human coronavirus NL63 (HCoV-NL63) spike glycoprotein-pseudotyped lentiviral particles by disruption of the viral envelope protein-triggered membrane fusion. Hence, in addition to reducing the production of infectious virions, inhibition of ER glucosidases also impairs the entry of selected viruses via a post-receptor-binding mechanism.
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Coller, B. S. "Activation affects access to the platelet receptor for adhesive glycoproteins." Journal of Cell Biology 103, no. 2 (August 1, 1986): 451–56. http://dx.doi.org/10.1083/jcb.103.2.451.
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Blood platelets have a receptor for macromolecular adhesive glycoproteins, located on a heteroduplex membrane glycoprotein complex (GPIIb/IIIa) that only becomes "exposed" when platelets are activated. Binding of the adhesive glycoproteins, in particular fibrinogen, to the receptor is required for platelet aggregation, which in turn is required to arrest bleeding. A murine monoclonal antibody whose rate of binding to the receptor is affected by platelet activation was both cross-linked and fragmented to assess the effects of changes in molecular size on its rate of binding to unactivated and activated platelets. The results indicate that small molecules can bind more rapidly to the receptors on unactivated platelets than can large molecules and that activation involves a conformational and/or microenvironmental change that permits the large molecules to bind more rapidly.
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Zelus, Bruce D., David R. Wessner, Richard K. Williams, Michael N. Pensiero, Fenna T. Phibbs, Mark deSouza, Gabriela S. Dveksler, and Kathryn V. Holmes. "Purified, Soluble Recombinant Mouse Hepatitis Virus Receptor, Bgp1b, and Bgp2 Murine Coronavirus Receptors Differ in Mouse Hepatitis Virus Binding and Neutralizing Activities." Journal of Virology 72, no. 9 (September 1, 1998): 7237–44. http://dx.doi.org/10.1128/jvi.72.9.7237-7244.1998.
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ABSTRACT Mouse hepatitis virus receptor (MHVR) is a murine biliary glycoprotein (Bgp1a). Purified, soluble MHVR expressed from a recombinant vaccinia virus neutralized the infectivity of the A59 strain of mouse hepatitis virus (MHV-A59) in a concentration-dependent manner. Several anchored murine Bgps in addition to MHVR can also function as MHV-A59 receptors when expressed at high levels in nonmurine cells. To investigate the interactions of these alternative MHVR glycoproteins with MHV, we expressed and purified to apparent homogeneity the extracellular domains of several murine Bgps as soluble, six-histidine-tagged glycoproteins, using a baculovirus expression system. These include MHVR isoforms containing four or two extracellular domains and the corresponding Bgp1bglycoproteins from MHV-resistant SJL/J mice, as well as Bgp2 and truncation mutants of MHVR and Bgp1b comprised of the first two immunoglobulin-like domains. The soluble four-domain MHVR glycoprotein (sMHVR[1-4]) had fourfold more MHV-A59 neutralizing activity than the corresponding soluble Bgp1b(sBgp1b) glycoprotein and at least 1,000-fold more neutralizing activity than sBgp2. Although virus binds to the N-terminal domain (domain 1), soluble truncation mutants of MHVR and Bgp1b containing only domains 1 and 2 bound virus poorly and had 10- and 300-fold less MHV-A59 neutralizing activity than the corresponding four-domain glycoproteins. In contrast, the soluble MHVR glycoprotein containing domains 1 and 4 (sMHVR[1,4]) had as much neutralizing activity as the four-domain glycoprotein, sMHVR[1-4]. Thus, the virus neutralizing activity of MHVR domain 1 appears to be enhanced by domain 4. The sBgp1b[1-4] glycoprotein had 500-fold less neutralizing activity for MHV-JHM than for MHV-A59. Thus, MHV strains with differences in S-glycoprotein sequence, tissue tropism, and virulence can differ in the ability to utilize the various murine Bgps as receptors.
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McKeating, J. A., L. Q. Zhang, C. Logvinoff, M. Flint, J. Zhang, J. Yu, D. Butera, et al. "Diverse Hepatitis C Virus Glycoproteins Mediate Viral Infection in a CD81-Dependent Manner." Journal of Virology 78, no. 16 (August 15, 2004): 8496–505. http://dx.doi.org/10.1128/jvi.78.16.8496-8505.2004.
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ABSTRACT We recently reported that retroviral pseudotypes bearing the hepatitis C virus (HCV) strain H and Con1 glycoproteins, genotype 1a and 1b, respectively, require CD81 as a coreceptor for virus-cell entry and infection. Soluble truncated E2 cloned from a number of diverse HCV genotypes fail to interact with CD81, suggesting that viruses of diverse origin may utilize different receptors and display altered cell tropism. We have used the pseudotyping system to study the tropism of viruses bearing diverse HCV glycoproteins. Viruses bearing these glycoproteins showed a 150-fold range in infectivity for hepatoma cells and failed to infect lymphoid cells. The level of glycoprotein incorporation into particles varied considerably between strains, generally reflecting the E2 expression level within transfected cells. However, differences in glycoprotein incorporation were not associated with virus infectivity, suggesting that infectivity is not limited by the absolute level of glycoprotein. All HCV pseudotypes failed to infect HepG2 cells and yet infected the same cells after transduction to express human CD81, confirming the critical role of CD81 in HCV infection. Interestingly, these HCV pseudotypes differed in their ability to infect HepG2 cells expressing a panel of CD81 variants, suggesting subtle differences in the interaction of CD81 residues with diverse viral glycoproteins. Our current model of HCV infection suggests that CD81, together with additional unknown liver specific receptor(s), mediate the virus-cell entry process.
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Jambunathan, Nithya, Carolyn M. Clark, Farhana Musarrat, Vladimir N. Chouljenko, Jared Rudd, and Konstantin G. Kousoulas. "Two Sides to Every Story: Herpes Simplex Type-1 Viral Glycoproteins gB, gD, gH/gL, gK, and Cellular Receptors Function as Key Players in Membrane Fusion." Viruses 13, no. 9 (September 16, 2021): 1849. http://dx.doi.org/10.3390/v13091849.
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Herpes simplex virus type-1 (HSV-1) and type-2 (HSV-2) are prototypical alphaherpesviruses that are characterized by their unique properties to infect trigeminal and dorsal root ganglionic neurons, respectively, and establish life-long latent infections. These viruses initially infect mucosal epithelial tissues and subsequently spread to neurons. They are associated with a significant disease spectrum, including orofacial and ocular infections for HSV-1 and genital and neonatal infections for HSV-2. Viral glycoproteins within the virion envelope bind to specific cellular receptors to mediate virus entry into cells. This is achieved by the fusion of the viral envelope with the plasma membrane. Similarly, viral glycoproteins expressed on cell surfaces mediate cell-to-cell fusion and facilitate virus spread. An interactive complex of viral glycoproteins gB, gD/gH/gL, and gK and other proteins mediate these membrane fusion phenomena with glycoprotein B (gB), the principal membrane fusogen. The requirement for the virion to enter neuronal axons suggests that the heterodimeric protein complex of gK and membrane protein UL20, found only in alphaherpesviruses, constitute a critical determinant for neuronal entry. This hypothesis was substantiated by the observation that a small deletion in the amino terminus of gK prevents entry into neuronal axons while allowing entry into other cells via endocytosis. Cellular receptors and receptor-mediated signaling synergize with the viral membrane fusion machinery to facilitate virus entry and intercellular spread. Unraveling the underlying interactions among viral glycoproteins, envelope proteins, and cellular receptors will provide new innovative approaches for antiviral therapy against herpesviruses and other neurotropic viruses.
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Yang, Xinzhen, Svetla Kurteva, Xinping Ren, Sandra Lee, and Joseph Sodroski. "Subunit Stoichiometry of Human Immunodeficiency Virus Type 1 Envelope Glycoprotein Trimers during Virus Entry into Host Cells." Journal of Virology 80, no. 9 (May 1, 2006): 4388–95. http://dx.doi.org/10.1128/jvi.80.9.4388-4395.2006.
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ABSTRACT 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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Bishop, Kimberly A., Tzanko S. Stantchev, Andrew C. Hickey, Dimple Khetawat, Katharine N. Bossart, Valery Krasnoperov, Parkash Gill, et al. "Identification of Hendra Virus G Glycoprotein Residues That Are Critical for Receptor Binding." Journal of Virology 81, no. 11 (March 21, 2007): 5893–901. http://dx.doi.org/10.1128/jvi.02022-06.
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ABSTRACT Hendra virus (HeV) is an emerging paramyxovirus capable of infecting and causing disease in a variety of mammalian species, including humans. The virus infects its host cells through the coordinated functions of its fusion (F) and attachment (G) glycoproteins, the latter of which is responsible for binding the virus receptors ephrinB2 and ephrinB3. In order to identify the receptor binding site, a panel of G glycoprotein constructs containing mutations was generated using an alanine-scanning mutagenesis strategy. Based on a predicted G structure, charged amino acids residing in regions that could be homologous to those in the measles virus H attachment glycoprotein known to be involved in its protein receptor interaction were targeted. Using a coprecipitation-based assay, seven single-amino-acid substitutions in HeV G were identified as having significantly impaired binding to both the ephrinB2 and ephrinB3 viral receptors: D257A, D260A, G439A, K443A, G449A, K465A, and D468A. The impairment of receptor interaction conferred a concomitant diminution in their abilities to promote membrane fusion when coexpressed with F. The G glycoprotein mutants were also recognized by three or more conformation-dependent monoclonal antibodies of a panel of five, were expressed on the cell surface, and retained their abilities to bind and coprecipitate F. Interestingly, some of these mutant G glycoproteins coprecipitated with F more efficiently than wild-type G. Taken together, these data provide strong biochemical and functional evidence that some of these residues could be part of a conformation-dependent, discontinuous, and overlapping ephrinB2 and -B3 binding domain within the HeV G glycoprotein.
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Santos, Joy Ramielle L., Weijie Sun, Tarana A. Mangukia, Eduardo Reyes-Serratos, and Marcelo Marcet-Palacios. "Challenging the Existing Model of the Hexameric HIV-1 Gag Lattice and MA Shell Superstructure: Implications for Viral Entry." Viruses 13, no. 8 (July 31, 2021): 1515. http://dx.doi.org/10.3390/v13081515.
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Despite type 1 human immunodeficiency virus (HIV-1) being discovered in the early 1980s, significant knowledge gaps remain in our understanding of the superstructure of the HIV-1 matrix (MA) shell. Current viral assembly models assume that the MA shell originates via recruitment of group-specific antigen (Gag) polyproteins into a hexagonal lattice but fails to resolve and explain lattice overlapping that occurs when the membrane is folded into a spherical/ellipsoidal shape. It further fails to address how the shell recruits, interacts with and encompasses the viral spike envelope (Env) glycoproteins. These Env glycoproteins are crucial as they facilitate viral entry by interacting with receptors and coreceptors located on T-cells. In our previous publication, we proposed a six-lune hosohedral structure, snowflake-like model for the MA shell of HIV-1. In this article, we improve upon the six-lune hosohedral structure by incorporating into our algorithm the recruitment of complete Env glycoproteins. We generated the Env glycoprotein assembly using a combination of predetermined Env glycoprotein domains from X-ray crystallography, nuclear magnetic resonance (NMR), cryoelectron tomography, and three-dimensional prediction tools. Our novel MA shell model comprises 1028 MA trimers and 14 Env glycoproteins. Our model demonstrates the movement of Env glycoproteins in the interlunar spaces, with effective clustering at the fusion hub, where multiple Env complexes bind to T-cell receptors during the process of viral entry. Elucidating the HIV-1 MA shell structure and its interaction with the Env glycoproteins is a key step toward understanding the mechanism of HIV-1 entry.
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Komagome, Rika, Hirofumi Sawa, Takashi Suzuki, Yasuo Suzuki, Shinya Tanaka, Walter J. Atwood, and Kazuo Nagashima. "Oligosaccharides as Receptors for JC Virus." Journal of Virology 76, no. 24 (December 15, 2002): 12992–3000. http://dx.doi.org/10.1128/jvi.76.24.12992-13000.2002.
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ABSTRACT JC virus (JCV) belongs to the polyomavirus family of double-stranded DNA viruses and in humans causes a demyelinating disease of the central nervous system, progressive multifocal leukoencephalopathy. Its hemagglutination activity and entry into host cells have been reported to depend on an N-linked glycoprotein containing sialic acid. In order to identify the receptors of JCV, we generated virus-like particles (VLP) consisting of major viral capsid protein VP1. We then developed an indirect VLP overlay assay to detect VLP binding to glycoproteins and a panel of glycolipids. We found that VLP bound to sialoglycoproteins, including α1-acid glycoprotein, fetuin, and transferrin receptor, and that this binding depended on α2-3-linked sialic acids and N-linked sugar chains. Neoglycoproteins were synthesized by using ovalbumin and conjugation with oligosaccharides containing the terminal α2-3- or α2-6-linked sialic acid or the branched α2-6-linked sialic acid. We show that the neoglycoprotein containing the terminal α2-6-linked sialic acid had the highest affinity for VLP, inhibited the hemagglutination activity of VLP and JCV, and inhibited the attachment of VLP to cells. We also demonstrate that VLP bound to specific glycolipids, such as lactosylceramide, and gangliosides, including GM3, GD2, GD3, GD1b, GT1b, and GQ1b, and that VLP bound weakly to GD1a but did not bind to GM1a, GM2, or galactocerebroside. Furthermore, the neoglycoprotein containing the terminal α2-6-linked sialic acid and the ganglioside GT1b inhibited JCV infection in the susceptible cell line IMR-32. These results suggest that the oligosaccharides of glycoproteins and glycolipids work as JCV receptors and may be feasible as anti-JCV agents.
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Rahman, Shah, Mairaj Ansari, Pratibha Gaur, Imtiyaz Ahmad, Chandrani Chakravarty, Dileep Verma, Anshika Sharma, et al. "The Immunomodulatory CEA Cell Adhesion Molecule 6 (CEACAM6/CD66c) Is a Protein Receptor for the Influenza A Virus." Viruses 13, no. 5 (April 21, 2021): 726. http://dx.doi.org/10.3390/v13050726.
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To establish a productive infection in host cells, viruses often use one or multiple host membrane glycoproteins as their receptors. For Influenza A virus (IAV) such a glycoprotein receptor has not been described, to date. Here we show that IAV is using the host membrane glycoprotein CD66c as a receptor for entry into human epithelial lung cells. Neuraminidase (NA), a viral spike protein, binds to CD66c on the cell surface during IAV entry into the host cells. Lung cells overexpressing CD66c showed an increase in virus binding and subsequent entry into the cell. Upon comparison, CD66c demonstrated higher binding capacity than other membrane glycoproteins (EGFR and DC-SIGN) reported earlier to facilitate IAV entry into host cells. siRNA mediated knockdown of CD66c from lung cells inhibited virus binding on cell surface and entry into cells. Blocking CD66c by antibody on the cell surface resulted in decreased virus entry. We found that CD66c is a specific glycoprotein receptor for influenza A virus that did not affect entry of non-IAV RNA virus (Hepatitis C virus). Finally, IAV pre-incubated with recombinant CD66c protein when administered intranasally in mice showed decreased cytopathic effects in mice lungs. This publication is the first to report CD66c (Carcinoembryonic cell adhesion molecule 6 or CEACAM6) as a glycoprotein receptor for Influenza A virus.
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Pacheco, Beatriz, Stephane Basmaciogullari, Jason A. LaBonte, Shi-Hua Xiang, and Joseph Sodroski. "Adaptation of the Human Immunodeficiency Virus Type 1 Envelope Glycoproteins to New World Monkey Receptors." Journal of Virology 82, no. 1 (October 24, 2007): 346–57. http://dx.doi.org/10.1128/jvi.01299-07.
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ABSTRACT Human immunodeficiency virus type 1 (HIV-1) infection encounters an early block in the cells of New World monkeys because the CD4 receptor does not efficiently support HIV-1 entry. We adapted HIV-1(NL4-3) and HIV-1(KB9), two HIV-1 variants with different envelope glycoproteins, to replicate efficiently in cells expressing the CD4 and CXCR4 proteins of the common marmoset, a New World monkey. The HIV-1(NL4-3) adaptation involves three gp120 changes that result in a specific increase in affinity for the marmoset CD4 glycoprotein. The already high affinity of the HIV-1(KB9) envelope glycoproteins for marmoset CD4 did not significantly change as a result of the adaptation. Instead, changes in the gp120 variable loops and gp41 ectodomain resulted in improved replication in cells expressing the marmoset receptors. HIV-1(KB9) became relatively sensitive to neutralization by soluble CD4 and antibodies as a result of the adaptation. These results demonstrate the distinct mechanistic pathways by which the HIV-1 envelope glycoproteins can adapt to less-than-optimal CD4 molecules and provide HIV-1 variants that can overcome some of the early blocks in New World monkey cells.
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Uchida, Hiroaki, Janet Chan, Indira Shrivastava, Bonnie Reinhart, Paola Grandi, Joseph C. Glorioso, and Justus B. Cohen. "Novel Mutations in gB and gH Circumvent the Requirement for Known gD Receptors in Herpes Simplex Virus 1 Entry and Cell-to-Cell Spread." Journal of Virology 87, no. 3 (November 14, 2012): 1430–42. http://dx.doi.org/10.1128/jvi.02804-12.
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ABSTRACTBoth entry and cell-to-cell spread of herpes simplex virus (HSV) involve a cascade of cooperative interactions among the essential glycoproteins D, B, and H/L (gD, gB, and gH/gL, respectively) initiated by the binding of gD to a cognate HSV entry receptor. We previously reported that a variant (D285N/A549T) of glycoprotein B (gB:NT) enabled primary virus entry into cells that were devoid of typical HSV entry receptors. Here, we compared the activities of the gB:NT variant with those of a newly selected variant of glycoprotein H (gH:KV) and a frequently coselected gB variant (gB:S668N). In combination, gH:KV and gB:S668N enabled primary virus entry into cells that lacked established HSV entry receptors as efficiently as did gB:NT, but separately, each variant enabled only limited entry. Remarkably, gH:KV uniquely facilitated secondary virus spread between cells that lacked canonical entry receptors. Transient expression of the four essential entry glycoproteins revealed that gH:KV, but not gB:NT, induced fusion between cells lacking the standard receptors. Because the involvement of gD remained essential for virus spread and cell fusion, we propose that gH:KV mimics a transition state of gH that responds efficiently to weak signals from gD to reach the active state. Computational modeling of the structures of wild-type gH and gH:KV revealed relatively subtle differences that may have accounted for our experimental findings. Our study shows that (i) the dependence of HSV-1 entry and spread on specific gD receptors can be reduced by sequence changes in the downstream effectors gB and gH, and (ii) the relative roles of gB and gH are different in entry and spread.
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Tailor, Chetankumar S., Ali Nouri, and David Kabat. "A Comprehensive Approach to Mapping the Interacting Surfaces of Murine Amphotropic and Feline Subgroup B Leukemia Viruses with Their Cell Surface Receptors." Journal of Virology 74, no. 1 (January 1, 2000): 237–44. http://dx.doi.org/10.1128/jvi.74.1.237-244.2000.
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ABSTRACT Because mutations in envelope glycoproteins of retroviruses or in their cell surface receptors can eliminate function by multiple mechanisms, it has been difficult to unambiguously identify sites for their interactions by site-directed mutagenesis. Recently, we developed a gain-of-function approach to overcome this problem. Our strategy relies on the fact that feline leukemia virus subgroup B (FeLV-B) and amphotropic murine leukemia virus (A-MLV) have closely related gp70 surface envelope glycoproteins and use related Na+-dependent phosphate symporters, Pit1 and Pit2, respectively, as their receptors. We previously observed that FeLV-B/A-MLV envelope glycoprotein chimeras spliced between the variable regions VRA and VRB were unable to use Pit1 or Pit2 as a receptor but could efficiently use specific Pit1/Pit2 chimeras. The latter study suggested that the VRA of A-MLV and FeLV-B functionally interact with the presumptive extracellular loops 4 and 5 (ECL4 and -5) of their respective receptors, whereas VRB interacts with ECL2. We also found that FeLV-B gp70 residues F60 and P61 and A-MLV residues Y60 and V61 in the first disulfide-bonded loop of VRA were important for functional interaction with the receptor's ECL4 or -5. We have now extended this approach to identify additional VRA and VRB residues that are involved in receptor recognition. Our studies imply that FeLV-B VRA residues F60 and P61 interact with the Pit1 ECL5 region, whereas VRA residues 66 to 78 interact with Pit1 ECL4. Correspondingly, A-MLV VRA residues Y60 and V61 interact with the Pit2 ECL5 region, whereas residues 66 to 78 interact with Pit2 ECL4. Similar studies that focused on the gp70 VRB implicated residues 129 to 139 as contributing to specific interactions with the receptor ECL2. These results identify three regions of gp70 that interact in a specific manner with distinct portions of their receptors, thereby providing a map of the functionally interacting surfaces.
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Chen, Jia, and Richard Longnecker. "Epithelial cell infection by Epstein–Barr virus." FEMS Microbiology Reviews 43, no. 6 (October 4, 2019): 674–83. http://dx.doi.org/10.1093/femsre/fuz023.
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ABSTRACT Epstein-Barr Virus (EBV) is etiologically associated with multiple human malignancies including Burkitt lymphoma and Hodgkin disease as well as nasopharyngeal and gastric carcinoma. Entry of EBV into target cells is essential for virus to cause disease and is mediated by multiple viral envelope glycoproteins and cell surface associated receptors. The target cells of EBV include B cells and epithelial cells. The nature and mechanism of EBV entry into these cell types are different, requiring different glycoprotein complexes to bind to specific receptors on the target cells. Compared to the B cell entry mechanism, the overall mechanism of EBV entry into epithelial cells is less well known. Numerous receptors have been implicated in this process and may also be involved in additional processes of EBV entry, transport, and replication. This review summarizes EBV glycoproteins, host receptors, signal molecules and transport machinery that are being used in the epithelial cell entry process and also provides a broad view for related herpesvirus entry mechanisms.
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Madani, Navid, Amy M. Hubicki, Ana Luisa Perdigoto, Martin Springer, and Joseph Sodroski. "Inhibition of Human Immunodeficiency Virus Envelope Glycoprotein- Mediated Single Cell Lysis by Low-Molecular-Weight Antagonists of Viral Entry." Journal of Virology 81, no. 2 (August 30, 2006): 532–38. http://dx.doi.org/10.1128/jvi.01079-06.
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ABSTRACT The coexpression of human immunodeficiency virus type 1 (HIV-1) envelope glycoproteins and receptors leads to the lysis of single cells by a process that is dependent upon membrane fusion. This cell lysis was inhibited by low-molecular-weight compounds that interfere with receptor binding or with receptor-induced conformational transitions in the envelope glycoproteins. A peptide, T20, potently inhibited cell-cell fusion but had no effect on single cell lysis mediated by the HIV-1 envelope glycoproteins. Thus, critical events in the lysis of single cells by the HIV-1 envelope glycoproteins occur in intracellular compartments accessible only to small inhibitory compounds.
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Qian, Mengding, and Billy Tsai. "Lipids and Proteins Act in Opposing Manners To Regulate Polyomavirus Infection." Journal of Virology 84, no. 19 (July 28, 2010): 9840–52. http://dx.doi.org/10.1128/jvi.01093-10.
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ABSTRACT How receptors control virus infection is poorly understood. Polyomavirus (Py) binds to the sialic acid-galactose moiety on receptors to gain entry into host cells and cause infection. We previously demonstrated that the sialic acid-galactose-containing glycolipids called gangliosides GD1a and GT1b promote Py infection, in part, by sorting the virus from the endolysosomes to the endoplasmic reticulum (ER), a critical infection route. Whether these glycolipids act as Py entry receptors, however, is not clear. Additionally, as the majority of glycoproteins also harbor terminal sialic acid-galactose residues, their roles in Py infection are also not well established. Using a ganglioside-deficient cell line, we show that GD1a is the functional entry receptor for Py. GD1a binds to Py on the plasma membrane, and the receptor-virus complex is internalized and transported to the late endosomes and then the ER to initiate infection. In contrast, our findings indicate that glycoproteins act as decoy receptors, restricting the ER transport and infection of Py. Thus, glycolipids and glycoproteins, two major constituents of the plasma membrane, execute opposing functions in regulating infection by a defined virus.
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Elleder, Daniel, Volodymir Stepanets, Deborah C. Melder, Filip Šenigl, Josef Geryk, Petr Pajer, Jiří Plachý, Jiří Hejnar, Jan Svoboda, and Mark J. Federspiel. "The Receptor for the Subgroup C Avian Sarcoma and Leukosis Viruses, Tvc, Is Related to Mammalian Butyrophilins, Members of the Immunoglobulin Superfamily." Journal of Virology 79, no. 16 (August 15, 2005): 10408–19. http://dx.doi.org/10.1128/jvi.79.16.10408-10419.2005.
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ABSTRACT The five highly related envelope subgroups of the avian sarcoma and leukosis viruses (ASLVs), subgroup A [ASLV(A)] to ASLV(E), are thought to have evolved from an ancestral envelope glycoprotein yet utilize different cellular proteins as receptors. Alleles encoding the subgroup A ASLV receptors (Tva), members of the low-density lipoprotein receptor family, and the subgroup B, D, and E ASLV receptors (Tvb), members of the tumor necrosis factor receptor family, have been identified and cloned. However, alleles encoding the subgroup C ASLV receptors (Tvc) have not been cloned. Previously, we established a genetic linkage between tvc and several other nearby genetic markers on chicken chromosome 28, including tva. In this study, we used this information to clone the tvc gene and identify the Tvc receptor. A bacterial artificial chromosome containing a portion of chicken chromosome 28 that conferred susceptibility to ASLV(C) infection was identified. The tvc gene was identified on this genomic DNA fragment and encodes a 488-amino-acid protein most closely related to mammalian butyrophilins, members of the immunoglobulin protein family. We subsequently cloned cDNAs encoding Tvc that confer susceptibility to infection by subgroup C viruses in chicken cells resistant to ASLV(C) infection and in mammalian cells that do not normally express functional ASLV receptors. In addition, normally susceptible chicken DT40 cells were resistant to ASLV(C) infection after both tvc alleles were disrupted by homologous recombination. Tvc binds the ASLV(C) envelope glycoproteins with low-nanomolar affinity, an affinity similar to that of binding of Tva and Tvb with their respective envelope glycoproteins. We have also identified a mutation in the tvc gene in line L15 chickens that explains why this line is resistant to ASLV(C) infection.
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Kolchinsky, Peter, Tajib Mirzabekov, Michael Farzan, Enko Kiprilov, Mark Cayabyab, Larissa J. Mooney, Hyeryun Choe, and Joseph Sodroski. "Adaptation of a CCR5-Using, Primary Human Immunodeficiency Virus Type 1 Isolate for CD4-Independent Replication." Journal of Virology 73, no. 10 (October 1, 1999): 8120–26. http://dx.doi.org/10.1128/jvi.73.10.8120-8126.1999.
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ABSTRACT The gp120 envelope glycoprotein of the human immunodeficiency virus type 1 (HIV-1) promotes virus entry by sequentially binding CD4 and chemokine receptors on the target cell. Primary, clinical HIV-1 isolates require interaction with CD4 to allow gp120 to bind the CCR5 chemokine receptor efficiently. We adapted a primary HIV-1 isolate, ADA, to replicate in CD4-negative canine cells expressing human CCR5. The gp120 changes responsible for the adaptation were limited to alteration of glycosylation addition sites in the V2 loop–V1-V2 stem. The gp120 glycoproteins of the adapted viruses bound CCR5 directly, without prior interaction with CD4. Thus, a major function of CD4 binding in the entry of primary HIV-1 isolates can be bypassed by changes in the gp120 V1-V2 elements, which allow the envelope glycoproteins to assume a conformation competent for CCR5 binding.
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Balliet, John W., and Paul Bates. "Efficient Infection Mediated by Viral Receptors Incorporated into Retroviral Particles." Journal of Virology 72, no. 1 (January 1, 1998): 671–76. http://dx.doi.org/10.1128/jvi.72.1.671-676.1998.
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ABSTRACT Many host cell surface proteins, including viral receptors, are incorporated into enveloped viruses. To address the functional significance of these host proteins, murine leukemia viruses containing the cellular receptors for Rous sarcoma virus (Tva) or ecotropic murine leukemia virus (MCAT-1) were produced. These receptor-pseudotyped viruses efficiently infect cells expressing the cognate viral envelope glycoproteins, with titers of up to 105 infectious units per milliliter for the Tva pseudotypes. Receptor and viral glycoprotein specificity and functional requirements are maintained, suggesting that receptor pseudotype infection recapitulates events of normal viral entry. The ability of the Tva and MCAT-1 pseudotypes to infect cells efficiently suggests that, in contrast to human immunodeficiency virus type 1 entry, neither of these retroviral receptors requires a coreceptor for membrane fusion. In addition, the ability of receptor pseudotypes to target infected cells suggests that they may be useful therapeutic reagents for directing infection of viral vectors. Receptor-pseudotyped viruses may be useful for identifying new viral receptors or for defining functional requirements of known receptors. Moreover, this work suggests that the production of receptor pseudotypes in vivo could provide a mechanism for expanded viral tropism with potential effects on the pathogenesis and evolution of the virus.
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Basu, Arnab, Tatsuo Kanda, Aster Beyene, Kousuke Saito, Keith Meyer, and Ranjit Ray. "Sulfated Homologues of Heparin Inhibit Hepatitis C Virus Entry into Mammalian Cells." Journal of Virology 81, no. 8 (February 7, 2007): 3933–41. http://dx.doi.org/10.1128/jvi.02622-06.
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ABSTRACT The mechanism of entry of hepatitis C virus (HCV) through interactions between the envelope glycoproteins and specific cell surface receptors remains unclear at this time. We have previously shown with the vesicular stomatitis virus (VSV)/HCV pseudotype model that the hypervariable region 1 of the HCV E2 envelope glycoprotein helps in binding with glycosaminoglycans present on the cell surface. In this study, we have examined the binding of HCV envelope glycoproteins with chemically modified derivatives of heparin. Furthermore, we have determined the functional relevance of the interaction of heparin derivatives with HCV envelope glycoproteins for infectivity by using a human immunodeficiency virus (HIV)/HCV pseudotype, a VSV/HCV pseudotype, and cell culture-grown HCV genotype 1a. Taken together, our results suggest that the HCV envelope glycoproteins rely upon O-sulfated esters of a heparin homologue to facilitate entry into mammalian cells.
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Ruhl, Stefan, John O. Cisar, and Ann L. Sandberg. "Identification of Polymorphonuclear Leukocyte and HL-60 Cell Receptors for Adhesins of Streptococcus gordonii and Actinomyces naeslundii." Infection and Immunity 68, no. 11 (November 1, 2000): 6346–54. http://dx.doi.org/10.1128/iai.68.11.6346-6354.2000.
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ABSTRACT Interactions of oral streptococci and actinomyces with polymorphonuclear leukocytes (PMNs), mediated by sialic acid- and Gal/GalNAc-reactive adhesins, respectively, result in activation of the PMNs and thereby may contribute to the initiation of oral inflammation. Sialidase treatment of PMNs or HL-60 cells abolished adhesion ofStreptococcus gordonii but was required for adhesion ofActinomyces naeslundii. The same effects of sialidase were noted for adhesion of these bacteria to a major 150-kDa surface glycoprotein of either PMNs or undifferentiated HL-60 cells and to a 130-kDa surface glycoprotein of differentiated HL-60 cells. These glycoproteins were both identified as leukosialin (CD43) by immunoprecipitation with a specific monoclonal antibody (MAb). Adhesion of streptococci and actinomyces to a 200-kDa minor PMN surface glycoprotein was also detected by bacterial overlay of untreated and sialidase-treated nitrocellulose transfers, respectively. This glycoprotein was identified as leukocyte common antigen (CD45) by immunoprecipitation with a specific MAb. CD43 and CD45 both possess extracellular mucinlike domains in addition to intracellular domains that are implicated in signal transduction. Consequently, the interactions of streptococci and actinomyces with the mucinlike domains of these mammalian cell surface glycoproteins result not only in adhesion but, in addition, may represent the initial step in PMN activation by these bacteria.
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Sullivan, Nancy, Ying Sun, Quentin Sattentau, Markus Thali, Dona Wu, Galina Denisova, Jonathan Gershoni, James Robinson, John Moore, and Joseph Sodroski. "CD4-Induced Conformational Changes in the Human Immunodeficiency Virus Type 1 gp120 Glycoprotein: Consequences for Virus Entry and Neutralization." Journal of Virology 72, no. 6 (June 1, 1998): 4694–703. http://dx.doi.org/10.1128/jvi.72.6.4694-4703.1998.
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ABSTRACT Human immunodeficiency virus type 1 (HIV-1) entry into target cells involves sequential binding of the gp120 exterior envelope glycoprotein to CD4 and to specific chemokine receptors. Soluble CD4 (sCD4) is thought to mimic membrane-anchored CD4, and its binding alters the conformation of the HIV-1 envelope glycoproteins. Two cross-competing monoclonal antibodies, 17b and CG10, that recognize CD4-inducible gp120 epitopes and that block gp120-chemokine receptor binding were used to investigate the nature and functional significance of gp120 conformational changes initiated by CD4 binding. Envelope glycoproteins derived from both T-cell line-adapted and primary HIV-1 isolates exhibited increased binding of the 17b antibody in the presence of sCD4. CD4-induced exposure of the 17b epitope on the oligomeric envelope glycoprotein complex occurred over a wide range of temperatures and involved movement of the gp120 V1/V2 variable loops. Amino acid changes that reduced the efficiency of 17b epitope exposure following CD4 binding invariably compromised the ability of the HIV-1 envelope glycoproteins to form syncytia or to support virus entry. Comparison of the CD4 dependence and neutralization efficiencies of the 17b and CG10 antibodies suggested that the epitopes for these antibodies are minimally accessible following attachment of gp120 to cell surface CD4. These results underscore the functional importance of these CD4-induced changes in gp120 conformation and illustrate viral strategies for sequestering chemokine receptor-binding regions from the humoral immune response.
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Norris, W. E. "Evidence for a second class of membrane glycoprotein involved in cell adhesion." Journal of Cell Science 93, no. 4 (August 1, 1989): 631–40. http://dx.doi.org/10.1242/jcs.93.4.631.
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It is believed that transmembrane relationships exist between the cytoskeleton and the extracellular matrix through integral membrane proteins, almost certainly glycoproteins, which would act as transmembrane receptors. Such receptors would include those involved in cell adhesion. I have been able to isolate a detergent-soluble fraction from chick embryo fibroblasts that is enriched in these integral membrane proteins by making use of their amphipathic character to phase-separate them in the detergent Triton X-114. Antisera raised to this fraction had biological activities interfering with cell adhesion and motility. A 45 X 10(3) Mr glycoprotein unique to this fraction appears to be responsible for this biological activity and is a candidate for a transmembrane receptor involved in cell adhesion.
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Gruol, Donald J., and Suzanne Bourgeois. "Expression of the mdr1 P-glycoprotein gene: a mechanism of escape from glucocorticoid-induced apoptosis." Biochemistry and Cell Biology 72, no. 11-12 (November 1, 1994): 561–71. http://dx.doi.org/10.1139/o94-075.
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Glucocorticoid hormones cause apoptosis in the murine T-lymphoma cell line WEHI-7. Glucocorticoid receptors in these cells are cytoplasmic proteins that translocate to the nucleus upon binding hormone. Thus, regulation of cytoplasmic glucocorticoid concentrations controls the level of activated receptors and sensitivity to steroid-induced apoptosis. We found that expression of the mdr1 P-glycoprotein gene produces a reduced accumulation of dexamethasone in WEHI-7 cells. Concomitantly, there is a suppression of dexamethasone-induced changes in transcription and a decrease in steroid sensitivity. P-glycoproteins are known to cause an outward, ATP-dependent transport of a variety of unrelated hydrophobic drugs across the plasma membrane. Our results indicate that glucocorticoid transport by P-glycoproteins depends upon the presence of an hydroxyl group at position 11 of corticosteroids and is enhanced by hydroxyl groups at the positions 16, 17, and 21. The antiprogestin RU486, which contains a dimethyl aminophenyl substitution at the position 11, is not transported by the mdr 1 P-glycoprotein. We have found that RU486 is an inhibitor of P-glycoprotein function, indicating that steroid analogs could be useful chemosensitizers in patients undergoing chemotherapy.Key words: multidrug resistance, glucocorticoids, apoptosis, lymphomas, RU486.
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Zhou, Guoying, and Bernard Roizman. "Characterization of a Recombinant Herpes Simplex Virus 1 Designed To Enter Cells via the IL13Rα2 Receptor of Malignant Glioma Cells." Journal of Virology 79, no. 9 (May 1, 2005): 5272–77. http://dx.doi.org/10.1128/jvi.79.9.5272-5277.2005.
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ABSTRACT Malignant glioma tumor cells in situ exhibit on their surfaces the interleukin 13 (IL-13) receptor designated IL13Rα2. To target herpes simplex virus 1 to this receptor, we constructed a recombinant virus (R5111) in which the known heparan sulfate binding sites in glycoproteins B and C were deleted and IL-13 was inserted into both glycoproteins C and D. We also transduced a baby hamster kidney cell line lacking the known viral receptors (J1-1) and Vero cells with a plasmid encoding IL13Rα2. The J1-1 derivative (J-13R) cell line is susceptible to and replicates the R5111 recombinant virus but not the wild-type parent virus. We report the following. (i) Expression of IL13Rα2 was rapidly lost from the surface of transduced cells grown in culture. The loss appeared to be related to ligands present in fetal bovine serum in the medium. None of the malignant glioma cell lines cultivated in vitro and tested to date exhibited the IL13Rα2 receptor. (ii) Soluble IL-13 but not IL-4 or IL-2 blocked the replication of R5111 recombinant virus in J-13R cells. (iii) The endocytosis inhibitor PD98059 blocked the replication in J1-1 cells of a mutant lacking glycoprotein D (gD−/−) but not the replication of R5111 in the J-13R cells. We conclude that R5111 enters cells via its interaction with the IL13Rα2 receptor in a manner that cannot be differentiated from the interaction of wild-type virus with its receptors.
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Munguia, Audelia, and Mark J. Federspiel. "Efficient Subgroup C Avian Sarcoma and Leukosis Virus Receptor Activity Requires the IgV Domain of the Tvc Receptor and Proper Display on the Cell Membrane." Journal of Virology 82, no. 22 (September 3, 2008): 11419–28. http://dx.doi.org/10.1128/jvi.01408-08.
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ABSTRACT We recently identified and cloned the receptor for subgroup C avian sarcoma and leukosis viruses [ASLV(C)], i.e., Tvc, a protein most closely related to mammalian butyrophilins, which are members of the immunoglobulin protein family. The extracellular domain of Tvc contains two immunoglobulin-like domains, IgV and IgC, which presumably each contain a disulfide bond important for native function of the protein. In this study, we have begun to identify the functional determinants of Tvc responsible for ASLV(C) receptor activity. We found that the IgV domain of the Tvc receptor is responsible for interacting with the glycoprotein of ASLV(C). Additional experiments demonstrated that a domain was necessary as a spacer between the IgV domain and the membrane-spanning domain for efficient Tvc receptor activity, most likely to orient the IgV domain a proper distance from the cell membrane. The effects on ASLV(C) glycoprotein binding and infection efficiency were also studied by site-directed mutagenesis of the cysteine residues of Tvc as well as conserved amino acid residues of the IgV Tvc domain compared to other IgV domains. In this initial analysis of Tvc determinants important for interacting with ASLV(C) glycoproteins, at least two aromatic amino acid residues in the IgV domain of Tvc, Trp-48 and Tyr-105, were identified as critical for efficient ASLV(C) infection. Interestingly, one or more aromatic amino acid residues have been identified as critical determinants in the other ASLV(A-E) receptors for a proper interaction with ASLV glycoproteins. This suggests that the ASLV glycoproteins may share a common mechanism of receptor interaction with an aromatic residue(s) on the receptor critical for triggering conformational changes in SU that initiate the fusion process required for efficient virus infection.
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Sudo, Satoko, Yoshimitsu Kuwabara, Jae-Il Park, Sheau Yu Hsu, and Aaron J. W. Hsueh. "Heterodimeric Fly Glycoprotein Hormone-α2 (GPA2) and Glycoprotein Hormone-β5 (GPB5) Activate Fly Leucine-Rich Repeat-Containing G Protein-Coupled Receptor-1 (DLGR1) and Stimulation of Human Thyrotropin Receptors by Chimeric Fly GPA2 and Human GPB5." Endocrinology 146, no. 8 (August 1, 2005): 3596–604. http://dx.doi.org/10.1210/en.2005-0317.
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Abstract Glycoprotein hormones play important roles in thyroid and gonadal function in vertebrates. The glycoprotein hormone α-subunit forms heterodimers with different β-subunits to activate TSH or gonadotropin (LH and FSH) receptors. Recent genomic analyses allowed the identification of another α-subunit, GPA2, and another β-subunit, GPB5, in human, capable of forming heterodimers to activate TSH receptors. Based on comparative genomic searches, we isolated the fly orthologs for human GPA2 and GPB5, each consisting of 10 cysteine residues likely involved in cystine-knot formation. RT-PCR analyses in Drosophila melanogaster demonstrated the expression of GPA2 and GPB5 at different developmental stages. Immunoblot analyses further showed that fly GPA2 and GPB5 subunit proteins are of approximately 16 kDa, and coexpression of these subunits yielded heterodimers. Purified recombinant fly GPA2/GPB5 heterodimers were found to be glycoproteins with N-linked glycosylated α-subunits and nonglycosylated β-subunits, capable of stimulating cAMP production mediated by fly orphan receptor DLGR1 but not DLGR2. Although the fly GPA2/GPB5 heterodimers did not activate human TSH or gonadotropin receptors, chimeric fly GPA2/human GPB5 heterodimers stimulated human TSH receptors. These findings indicated that fly GPA2/GPB5 is a ligand for DLGR1, thus showing the ancient origin of this glycoprotein hormone-seven transmembrane receptor-G protein signaling system. The fly GPA2 also could form heterodimers with human GPB5 to activate human TSH receptors, indicating the evolutionary conservation of these genes and suggesting that the GPA2 subunit may serve as a scaffold for the β-subunit to activate downstream G protein-mediated signaling.
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Kinloch, R. A., S. Mortillo, and P. M. Wassarman. "Transgenic mouse eggs with functional hamster sperm receptors in their zona pellucida." Development 115, no. 4 (August 1, 1992): 937–46. http://dx.doi.org/10.1242/dev.115.4.937.
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Sperm receptors are located in the mammalian egg extracellular coat, or zona pellucida. Mouse and hamster sperm receptor glycoproteins, mZP3 (83 × 10(3) M(r)) and hZP3 (56 × 10(3) M(r)), respectively, have very similar polypeptides (44 × 10(3) M(r); 81% identical) that are glycosylated to different extents. Purified mZP3 and hZP3 can bind to mouse sperm, prevent them from binding to eggs and induce them to undergo exocytosis, the acrosome reaction, in vitro. A DNA construct that placed the hZP3 gene under the control of mZP3 gene 5′-flanking sequence was used in this report to produce two mouse lines that harbored the foreign sperm receptor transgene. In both lines, the transgene was expressed only by growing oocytes, at a level comparable to that of the endogenous mZP3 gene, and the developmental pattern of transgene expression resembled that of the mZP3 gene. In addition to mZP3, transgenic mouse oocytes synthesized and secreted a glycoprotein indistinguishable from hZP3, and incorporated both glycoproteins into a mosaic zona pellucida. Importantly, hZP3 purified from such zonae pellucidae exhibited both sperm receptor and acrosome reaction-inducing activities in vitro and, following fertilization of transgenic mouse eggs, was inactivated. These results demonstrate that a biologically active foreign sperm receptor can be synthesized and secreted by transgenic mouse oocytes, assembled into a mosaic zona pellucida, and inactivated following fertilization as part of the secondary block to polyspermy.
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Wang, Jia, Xiang Zheng, Qiu Peng, Xuemei Zhang, and Zailong Qin. "Eph receptors: the bridge linking host and virus." Cellular and Molecular Life Sciences 77, no. 12 (December 31, 2019): 2355–65. http://dx.doi.org/10.1007/s00018-019-03409-6.
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AbstractEph (erythropoietin-producing hepatoma) receptors and Ephrin ligands constitute the largest subfamily of receptor tyrosine kinase (RTK), which were first discovered in tumors. Heretofore, Eph protein has been shown to be involved in various tumor biological behaviors including proliferation and progression. The occurrence of specific types of tumor is closely related to the virus infection. Virus entry is a complex process characterized by a series of events. The entry into target cells is an essential step for virus to cause diseases, which requires the fusion of the viral envelope and host cellular membrane mediated by viral glycoproteins and cellular receptors. Integrin molecules are well known as entry receptors for most herpes viruses. However, in recent years, Eph receptors and their Ephrin ligands have been reported to be involved in virus infections. The main mechanism may be the interaction between Eph receptors and conserved viral surface glycoprotein, such as the gH/gL or gB protein of the herpesviridae. This review focuses on the relationship between Eph receptor family and virus infection that summarize the processes of viruses such as EBV, KSHV, HCV, RRV, etc., infecting target cells through Eph receptors and activating its downstream signaling pathways resulting in malignancies. Finally, we discussed the perspectives to block virus infection, prevention, and treatment of viral-related tumors via Eph receptor family.
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Cayabyab, Mark, Gunilla B. Karlsson, Bijan A. Etemad-Moghadam, Wolfgang Hofmann, Tavis Steenbeke, Matilda Halloran, John W. Fanton, Michael K. Axthelm, Norman L. Letvin, and Joseph G. Sodroski. "Changes in Human Immunodeficiency Virus Type 1 Envelope Glycoproteins Responsible for the Pathogenicity of a Multiply Passaged Simian-Human Immunodeficiency Virus (SHIV-HXBc2)." Journal of Virology 73, no. 2 (February 1, 1999): 976–84. http://dx.doi.org/10.1128/jvi.73.2.976-984.1999.
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ABSTRACT In vivo passage of a poorly replicating, nonpathogenic simian-human immunodeficiency virus (SHIV-HXBc2) generated an efficiently replicating virus, KU-1, that caused rapid CD4+T-lymphocyte depletion and AIDS-like illness in monkeys (S. V. Joag, Z. Li, L. Foresman, E. B. Stephens, L.-J. Zhao, I. Adany, D. M. Pinson, H. M. McClure, and O. Narayan, J. Virol. 70:3189–3197, 1996). The env gene of the KU-1 virus was used to create a molecularly cloned virus, SHIV-HXBc2P 3.2, that differed from a nonpathogenic SHIV-HXBc2 virus in only 12 envelope glycoprotein residues. SHIV-HXBc2P 3.2 replicated efficiently and caused rapid and persistent CD4+ T-lymphocyte depletion in inoculated rhesus macaques. Compared with the envelope glycoproteins of the parental SHIV-HXBc2, the SHIV-HXBc2P 3.2 envelope glycoproteins supported more efficient infection of rhesus monkey peripheral blood mononuclear cells. Both the parental SHIV-HXBc2 and the pathogenic SHIV-HXBc2P 3.2 used CXCR4 but none of the other seven transmembrane segment receptors tested as a second receptor. Compared with the parental virus, viruses with the SHIV-HXBc2P 3.2 envelope glycoproteins were more resistant to neutralization by soluble CD4 and antibodies. Thus, changes in the envelope glycoproteins account for the ability of the passaged virus to deplete CD4+ T lymphocytes rapidly and specify increased replicative capacity and resistance to neutralization.
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Dupuis, Gilles, and Bânû Bastin. "Binding of phytohemagglutinin to porcine lymphocyte receptors. Time-course studies and comparative binding isotherms using whole cells or cellular receptors incorporated into phospholipid vesicles." Canadian Journal of Biochemistry and Cell Biology 63, no. 9 (September 1, 1985): 1033–43. http://dx.doi.org/10.1139/o85-128.
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We have studied the binding of 125I-labeled phytohemagglutinin (PHA) to porcine splenic lymphocytes (107 cells∙mL−1) at 37 °C. Our data show that PHA binding is dependent on the incubation period and that a maximum quantity of 4.53 ± 0.13 μg is bound when 200 μg of PHA is added. The binding process is rapid and saturation can readily be achieved in less than 2 min. These observations suggest, in accordance with the mass-action principle, that the binding equilibrium can be rapidly displaced towards PHA–receptor complex formation when sufficient amounts of PHA are added. Our data further suggest that receptor sites are exposed at the cell surface and that putative cryptic receptor sites are unlikely to play a major role in the initial part of the binding process. We have studied this aspect by comparing Scatchard plots for PHA binding to receptors in intact lymphocytes and to lymphocyte-derived receptors incorporated into liposomes. In one case, partially purified plasma membranes were solubilized and incorporated into phosphatidylcholine–phosphatidylserine (PC–PS) vesicles prepared by detergent dialysis. In another case, PHA-receptor glycoproteins were purified by affinity chromatography and reassembled into PC–PS vesicles, using the same technique. Scatchard plot analyses showed nonlinear profiles with a concavity turned upward for PHA binding to receptors of intact cells or of PC–PS vesicles with plasma membranes, and a concavity turned downward for vesicles with purified glycoproteins. These observations suggest that PHA-receptor environment plays a determining role in the binding process of the lectin. Numerical data from binding experiments were obtained by computer-assisted nonlinear regression analysis, using a one ligand–two sites model. The (apparent) high-affinity constant (K1) for intact lymphocytes or partially purified plasma membrane components reassembled into liposomes was 4.6 × 107 M−1 and the (apparent) low-affinity constants (K2) were 4.4 × 106 ± 1.5 × 106 M−1 (intact lymphocytes) and 1.7 × 106 ± 0.6 × 106 M−1 (plasma membranes constituents reassembled into liposomes). The value obtained for reconstituted PHA-glycoprotein receptors (K) was 0.70 × 107 ± 0.10 × 107 M−1. The apparent number of sites was n1 = 0.19 × 106 ± 0.05 × 106 (high affinity) and n2 = 2.50 × 106 ± 0.50 × 106 (low affinity) sites per intact lymphocyte cell. In the case of the reconstituted systems, the number of sites per microgram protein of the PC–PS vesicles were n1 = 0.79 × 1010 ± 0.18 × 1010 and n2 = 31.8 × 1010 ± 8.5 × 1010 for the partially purified plasma membrane and n = 26.6 × 1010 ± 2.9 × 1010 for the purified PHA receptor glycoproteins. Data presented here are discussed in terms of the lymphocyte activation model of Prujansky and colleagues, which suggests that positively cooperative lectin binding is a sine qua non condition for lymphocyte activation.
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Kassa, Aemro, Andrés Finzi, Marie Pancera, Joel R. Courter, Amos B. Smith, and Joseph Sodroski. "Identification of a Human Immunodeficiency Virus Type 1 Envelope Glycoprotein Variant Resistant to Cold Inactivation." Journal of Virology 83, no. 9 (February 11, 2009): 4476–88. http://dx.doi.org/10.1128/jvi.02110-08.
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ABSTRACT The human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein trimer consists of gp120 and gp41 subunits and undergoes a series of conformational changes upon binding to the receptors, CD4 and CCR5/CXCR4, that promote virus entry. Surprisingly, we found that the envelope glycoproteins of some HIV-1 strains are functionally inactivated by prolonged incubation on ice. Serial exposure of HIV-1 to extremes of temperature, followed by expansion of replication-competent viruses, allowed selection of a temperature-resistant virus. The envelope glycoproteins of this virus resisted cold inactivation due to a single passage-associated change, H66N, in the gp120 exterior envelope glycoprotein. Histidine 66 is located within the gp41-interactive inner domain of gp120 and, in other studies, has been shown to decrease the sampling of the CD4-bound conformation by unliganded gp120. Substituting asparagine or other amino acid residues for histidine 66 in cold-sensitive HIV-1 envelope glycoproteins resulted in cold-stable phenotypes. Cold inactivation of the HIV-1 envelope glycoproteins occurred even at high pH, indicating that protonation of histidine 66 is not necessary for this process. Increased exposure of epitopes in the ectodomain of the gp41 transmembrane envelope glycoprotein accompanied cold inactivation, but shedding of gp120 did not. An amino acid change in gp120 (S375W) that promotes the CD4-bound state or treatment with soluble CD4 or a small-molecule CD4 mimic resulted in increased cold sensitivity. These results indicate that the CD4-bound intermediate of the HIV-1 envelope glycoproteins is cold labile; avoiding the CD4-bound state increases temperature stability.
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Scidmore, M. A., E. R. Fischer, and T. Hackstadt. "Sphingolipids and glycoproteins are differentially trafficked to the Chlamydia trachomatis inclusion." Journal of Cell Biology 134, no. 2 (July 15, 1996): 363–74. http://dx.doi.org/10.1083/jcb.134.2.363.
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Chlamydia trachomatis is an obligate intracellular pathogen that multiples within the confines of a membrane-bound vacuole called an inclusion. Approximately 40-50% of the sphingomyelin synthesized from exogenously added NBD-ceramide is specifically transported from the Golgi apparatus to the chlamydial inclusion (Hackstadt, T., M.A. Scidmore, and D.D. Rockey. 1995. Proc. Natl. Acad. Sci. USA. 92: 4877-4881). Given this major disruption of a cellular exocytic pathway and the similarities between glycolipid and glycoprotein exocytosis, we wished to determine whether the processing and trafficking of glycoproteins through the Golgi apparatus to the plasma membrane in chlamydia-infected cells was also disrupted. We analyzed the processing of several model glycoproteins including vesicular stomatitis virus G-protein, transferrin receptor, and human histocompatibility leukocyte class I antigen. In infected cells, the posttranslational processing and trafficking of these specific proteins through the Golgi apparatus and subsequent transport to the plasma membrane was not significantly impaired, nor were these glycoproteins found associated with the chlamydial inclusion membrane. Studies of receptor recycling from endocytic vesicles employing fluorescently and HRP-tagged transferrin and anti-transferrin receptor antibody revealed an increased local concentration of transferrin and transferrin receptor around but never within the chlamydial inclusion. However, Scatchard analysis failed to show either an increased intracellular accumulation of transferrin receptor or a decreased number of plasma membrane receptors in infected cells. Furthermore, the rate of exocytosis from the recycling endosomes to the plasma membrane was not altered in chlamydia-infected cells. Thus, although C. trachomatis disrupts the exocytosis of sphingolipids and the Golgi apparatus appears physically distorted, glycosylation and exocytosis of representative secreted and endocytosed proteins are not disrupted. These results suggest the existence of a previously unrecognized sorting of sphingolipids and glycoproteins in C. trachomatis-infected cells.
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Palmerin, Nancy, Farizeh Aalam, Romina Nabiee, Murali Muniraju, Javier Gordon Ogembo, and Jennifer Totonchy. "Suppression of DC-SIGN and gH Reveals Complex, Subset-Specific Mechanisms for KSHV Entry in Primary B Lymphocytes." Viruses 13, no. 8 (July 31, 2021): 1512. http://dx.doi.org/10.3390/v13081512.
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Kaposi sarcoma-associated herpesvirus (KSHV) is the causative agent of multiple cancers in immunocompromised patients including two lymphoproliferative disorders associated with KSHV infection of B lymphocytes. Despite many years of research into the pathogenesis of KSHV associated diseases, basic questions related to KSHV molecular virology remain unresolved. One such unresolved question is the cellular receptors and viral glycoproteins needed for KSHV entry into primary B lymphocytes. In this study, we assess the contributions of KSHV glycoprotein H (gH) and the cellular receptor DC-SIGN to KSHV infection in tonsil-derived B lymphocytes. Our results show that (1) neither KSHV-gH nor DC-SIGN are essential for entry into any B cell subset, (2) DC-SIGN does play a role in KSHV entry into tonsil-derived B cells, but in all B cell subtypes alternative entry mechanisms exist, (3) KSHV-gH can participate in KSHV entry into centrocytes via a DC-SIGN independent entry mechanism, and (4) in the absence of KSHV-gH, DC-SIGN is required for KSHV entry into centrocytes. Our results provide a first glimpse into the complexity of KSHV entry in the lymphocyte compartment and highlight that multiple subset-dependent entry mechanisms are employed by KSHV which depend upon multiple cellular receptors and multiple KSHV glycoproteins.
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Kingsley, D. M., K. F. Kozarsky, M. Segal, and M. Krieger. "Three types of low density lipoprotein receptor-deficient mutant have pleiotropic defects in the synthesis of N-linked, O-linked, and lipid-linked carbohydrate chains." Journal of Cell Biology 102, no. 5 (May 1, 1986): 1576–85. http://dx.doi.org/10.1083/jcb.102.5.1576.
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Biochemical, immunological, and genetic techniques were used to investigate the genetic defects in three types of low density lipoprotein (LDL) receptor-deficient hamster cells. The previously isolated ldlB, ldlC, and ldlD mutants all synthesized essentially normal amounts of a 125,000-D precursor form of the LDL receptor, but were unable to process this receptor to the mature form of 155,000 D. Instead, these mutants produced abnormally small, heterogeneous receptors that reached the cell surface but were rapidly degraded thereafter. The abnormal sizes of the LDL receptors in these cells were due to defective processing of the LDL receptor's N- and O-linked carbohydrate chains. Processing defects in these cells appeared to be general since the ldlB, ldlC, and ldlD mutants also showed defective glycosylation of a viral glycoprotein, alterations in glycolipid synthesis, and changes in resistance to several toxic lectins. Preliminary structural studies suggested that these cells had defects in multiple stages of the Golgi-associated processing reactions responsible for synthesis of glycolipids and in the N-linked and O-linked carbohydrate chains of glycoproteins. Comparisons between the ldl mutants and a large number of previously isolated CHO glycosylation defective mutants showed that the genetic defects in ldlB, ldlC, and ldlD cells were unique and that only very specific types of carbohydrate alteration could dramatically affect LDL receptor function.
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Wassarman, PM. "Eggs, Sperm, and Sugar. A Recipe for Fertilization." Physiology 3, no. 3 (June 1, 1988): 120–24. http://dx.doi.org/10.1152/physiologyonline.1988.3.3.120.
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The extracellular coat surrounding unfertilized mammalian eggs contains receptors that sperm recognize and bind in a species-specific manner during fertilization. These sperm receptors are glycoproteins that regulate interactions between eggs and sperm both before and after fertilization. Recent evidence suggests that it is certain of the sperm receptor's oligosaccharides that mediate gamete recognition and binding during mammalian fertilization.
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Lavillette, Dimitri, Alessia Ruggieri, Bertrand Boson, Marielle Maurice, and François-Loïc Cosset. "Relationship between SU Subdomains That Regulate the Receptor-Mediated Transition from the Native (Fusion-Inhibited) to the Fusion-Active Conformation of the Murine Leukemia Virus Glycoprotein." Journal of Virology 76, no. 19 (October 1, 2002): 9673–85. http://dx.doi.org/10.1128/jvi.76.19.9673-9685.2002.
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ABSTRACT Envelope glycoproteins (Env) of retroviruses are trimers of SU (surface) and TM (transmembrane) heterodimers and are expressed on virions in fusion-competent forms that are likely to be metastable. Activation of the viral receptor-binding domain (RBD) via its interaction with a cell surface receptor is thought to initiate a cascade of events that lead to refolding of the Env glycoprotein into its stable fusion-active conformation. While the fusion-active conformation of the TM subunit has been described in detail for several retroviruses, little is known about the fusion-competent structure of the retroviral glycoproteins or the molecular events that mediate the transition between the two conformations. By characterizing Env chimeras between the ecotropic and amphotropic murine leukemia virus (MLV) SUs as well as a set of point mutants, we show that alterations of the conformation of the SU glycoprotein strongly elevate Env fusogenicity by disrupting the stability of the Env complex. Compensatory mutations that restored both Env stability and fusion control were also identified, allowing definition of interactions within the Env complex that maintain the stability of the native Env complex. We show that, in the receptor-unbound form, structural interactions between the N terminus of the viral RBD (NTR domain), the proline-rich region (PRR), and the distal part of the C-terminal domain of the SU subunit maintain a conformation of the glycoprotein that is fusion inhibitory. Additionally, we identified mutations that disrupt this fusion-inhibitory conformation and allow fusion activation in the absence of viral receptors, provided that receptor-activated RBD fragments are added in trans during infection. Other mutations were identified that allow fusion activation in the absence of receptors for both the viral glycoprotein and the trans-acting RBD. Finally, we found mutations of the SU that bypass in cis the requirement for the NTR domain in fusion activation. All these different mutations call for a critical role of the PRR in mediating conformational changes of the Env glycoprotein during fusion activation. Our results suggest a model of MLV Env fusion activation in which unlocking of the fusion-inhibitory conformation is initiated by receptor binding of the viral RBD, which, upon disruption of the PRR, allows the NTR domain to promote further events in Env fusion activation. This involves a second type of interaction, in cis or in trans, between the receptor-activated RBD and a median segment of the freed C-terminal domain.
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Doig, Peter, William Paranchych, Parimi A. Sastry, and Randall T. Irvin. "Human buccal epithelial cell receptors of Pseudomonas aeruginosa: identification of glycoproteins with pilus binding activity." Canadian Journal of Microbiology 35, no. 12 (December 1, 1989): 1141–45. http://dx.doi.org/10.1139/m89-189.
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Adherence of Pseudomonas aeruginosa to a patient's epithelial surface is thought to be an important first step in the infection process. Pseudomonas aeruginosa is capable of attaching to epithelial cells via its pili, yet little is known about the epithelial receptors of this adhesin. Using nitrocellulose replicas of polyacrylamide gels of solubilized human buccal epithelial cells (BECs), glycoproteins (Mz: 82 000, and four bands between 40 000 and 50 000) that bound purified pili from P. aeruginosa strain K (PAK) were identified by immunoblotting with a pilus-specific monoclonal antibody that does not affect pilus binding to BECs (PK3B). All pilus-binding glycoproteins were surface localized, as determined by surface radioiodination of intact BECs. Binding of pili to all of the glycoproteins was inhibited by Fab fragments of monoclonal antibody PK99H, which inhibits PAK pili binding to BECs by binding to or near the binding domain of the pilus, but not by Fab fragments of monoclonal antibody PK41C, which binds to PAK pilin but does not inhibit pili binding to BECs, demonstrating that pilus binding to these glycoproteins is likely via the same region of the pilus that binds to intact BECs. Periodate oxidation of the blot eliminated pili binding to all glycoproteins, indicating that a carbohydrate moiety is an important determinant for pilus-binding activity. However, not all of the glycoproteins exhibited the same degree of sensitivity to periodate oxidation. Furthermore, monosaccharide inhibition of pilus binding to BECs implicated L-fucose and N-acetylneuraminic acid as receptor moieties.Key words: Pseudomonas aeruginosa, pili, receptor, adhesion.
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Duncan, J. R., and S. Kornfeld. "Intracellular movement of two mannose 6-phosphate receptors: return to the Golgi apparatus." Journal of Cell Biology 106, no. 3 (March 1, 1988): 617–28. http://dx.doi.org/10.1083/jcb.106.3.617.
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We have used Chinese hamster ovary (CHO) cells and a murine lymphoma cell line to study the recycling of the 215-kD and the 46-kD mannose 6-phosphate receptors to various regions of the Golgi to determine the site where the receptors first encounter newly synthesized lysosomal enzymes. For assessing return to the trans-most Golgi compartments containing sialyltransferase (trans-cisternae and trans-Golgi network), the oligosaccharides of receptor molecules on the cell surface were labeled with [3H]galactose at 4 degrees C. Upon warming to 37 degrees C, the [3H]galactose residues on both receptors were substituted with sialic acid with a t1/2 approximately 3 hrs. Other glycoproteins acquired sialic acid at least 8-10 times slower. Return of the receptors to the trans-Golgi cisternae containing galactosyltransferase could not be detected. Return to the cis/middle Golgi cisternae containing alpha-mannosidase I was measured by adding deoxymannojirimycin, a mannosidase I inhibitor, during the initial posttranslational passage of [3H]mannose-labeled glycoproteins through the Golgi, thereby preserving oligosaccharides which would be substrates for alpha-mannosidase I. After removal of the inhibitor, return to the early Golgi with subsequent passage through the Golgi complex was measured by determining the conversion of the oligosaccharides from high mannose to complex-type units. This conversion was very slow for the receptors and other glycoproteins (t1/2 approximately 20 h). Exposure of the receptors and other glycoproteins to the dMM-sensitive alpha-mannosidase without movement through the Golgi apparatus was determined by measuring the loss of mannose residues from these proteins. This loss was also slow. These results indicate that both Man-6-P receptors routinely return to the Golgi compartment which contains sialyltransferase and recycle through other regions of the Golgi region less frequently. We infer that the trans-Golgi network is the major site for lysosomal enzyme sorting in CHO and murine lymphoma cells.
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van der Meulen, Emma, Meg Anderton, Melissa J. Blumenthal, and Georgia Schäfer. "Cellular Receptors Involved in KSHV Infection." Viruses 13, no. 1 (January 17, 2021): 118. http://dx.doi.org/10.3390/v13010118.
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The process of Kaposi’s Sarcoma Herpes Virus’ (KSHV) entry into target cells is complex and engages several viral glycoproteins which bind to a large range of host cell surface molecules. Receptors for KSHV include heparan sulphate proteoglycans (HSPGs), several integrins and Eph receptors, cystine/glutamate antiporter (xCT) and Dendritic Cell-Specific Intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN). This diverse range of potential binding and entry sites allows KSHV to have a broad cell tropism, and entry into specific cells is dependent on the available receptor repertoire. Several molecules involved in KSHV entry have been well characterized, particularly those postulated to be associated with KSHV-associated pathologies such as Kaposi’s Sarcoma (KS). In this review, KSHV infection of specific cell types pertinent to its pathogenesis will be comprehensively summarized with a focus on the specific cell surface binding and entry receptors KSHV exploits to gain access to a variety of cell types. Gaps in the current literature regarding understanding interactions between KSHV glycoproteins and cellular receptors in virus infection are identified which will lead to the development of virus infection intervention strategies.
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Davis, Craig B., Ivan Dikic, Derya Unutmaz, C. Mark Hill, James Arthos, Michael A. Siani, Darren A. Thompson, Joseph Schlessinger, and Dan R. Littman. "Signal Transduction Due to HIV-1 Envelope Interactions with Chemokine Receptors CXCR4 or CCR5." Journal of Experimental Medicine 186, no. 10 (November 17, 1997): 1793–98. http://dx.doi.org/10.1084/jem.186.10.1793.
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Infection with HIV-1 requires expression of CD4 and the chemokine receptors CXCR4 or CCR5 at the target cell surface. Engagement of these receptors by the HIV-1 envelope glycoprotein is essential for membrane fusion, but may additionally activate intracellular signaling pathways. In this study, we demonstrate that chemokines and HIV-1 envelope glycoproteins from both T-tropic and macrophage-tropic strains rapidly induce tyrosine phosphorylation of the protein tyrosine kinase Pyk2. The response requires CXCR4 and CCR5 to be accessible on the cell surface. The results presented here provide the first evidence for activation of an intracellular signaling event that can initiate multiple signaling pathways as a consequence of contact between HIV-1 and chemokine receptors.
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Bixby, J. L., J. Lilien, and L. F. Reichardt. "Identification of the major proteins that promote neuronal process outgrowth on Schwann cells in vitro." Journal of Cell Biology 107, no. 1 (July 1, 1988): 353–61. http://dx.doi.org/10.1083/jcb.107.1.353.
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Schwann cells have a unique role in regulating the growth of axons during regeneration and presumably during development. Here we show that Schwann cells are the best substrate yet identified for promoting process growth in vitro by peripheral motor neurons. To determine the molecular interactions responsible for Schwann cell regulation of axon growth, we have examined the effects of specific antibodies on process growth in vitro, and have identified three glycoproteins that play major roles. These are the Ca2+-independent cell adhesion molecule (CAM), L1/Ng-CAM; the Ca2+-dependent CAM, N-cadherin; and members of the integrin extracellular matrix receptor superfamily. Two other CAMs present on neurons and/or Schwann cells-N-CAM and myelin-associated glycoprotein-do not appear to be important in regulating process growth. Our results imply that neuronal growth cones use integrin-class extracellular matrix receptors and at least two CAMs--N-cadherin and L1/Ng-CAM-for growth on Schwann cells in vitro and establish each of these glycoproteins as a strong candidate for regulating axon growth and guidance in vivo.