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Llorente García I, Marsh M. A biophysical perspective on receptor-mediated virus entry with a focus on HIV. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2020; 1862:183158. [PMID: 31863725 PMCID: PMC7156917 DOI: 10.1016/j.bbamem.2019.183158] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 12/12/2019] [Accepted: 12/13/2019] [Indexed: 12/14/2022]
Abstract
As part of their entry and infection strategy, viruses interact with specific receptor molecules expressed on the surface of target cells. The efficiency and kinetics of the virus-receptor interactions required for a virus to productively infect a cell is determined by the biophysical properties of the receptors, which are in turn influenced by the receptors' plasma membrane (PM) environments. Currently, little is known about the biophysical properties of these receptor molecules or their engagement during virus binding and entry. Here we review virus-receptor interactions focusing on the human immunodeficiency virus type 1 (HIV), the etiological agent of acquired immunodeficiency syndrome (AIDS), as a model system. HIV is one of the best characterised enveloped viruses, with the identity, roles and structure of the key molecules required for infection well established. We review current knowledge of receptor-mediated HIV entry, addressing the properties of the HIV cell-surface receptors, the techniques used to measure these properties, and the macromolecular interactions and events required for virus entry. We discuss some of the key biophysical principles underlying receptor-mediated virus entry and attempt to interpret the available data in the context of biophysical mechanisms. We also highlight crucial outstanding questions and consider how new tools might be applied to advance understanding of the biophysical properties of viral receptors and the dynamic events leading to virus entry.
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Affiliation(s)
| | - Mark Marsh
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
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2
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Lobo PI, Schlegel KH, Spencer CE, Okusa MD, Chisholm C, Mchedlishvili N, Park A, Christ C, Burtner C. Naturally Occurring IgM Anti-Leukocyte Autoantibodies (IgM-ALA) Inhibit T Cell Activation and Chemotaxis. THE JOURNAL OF IMMUNOLOGY 2008; 180:1780-91. [DOI: 10.4049/jimmunol.180.3.1780] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Lynch GW, Turville S, Carter B, Sloane AJ, Chan A, Muljadi N, Li S, Low L, Armati P, Raison R, Zoellner H, Williamson P, Cunningham A, Church WB. Marked differences in the structures and protein associations of lymphocyte and monocyte CD4: resolution of a novel CD4 isoform. Immunol Cell Biol 2006; 84:154-65. [PMID: 16519733 DOI: 10.1111/j.1440-1711.2005.01403.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The structures, molecular interactions and functions of CD4 in a subset of T lymphocytes have been well characterized. The CD4 receptors of other cell types have, however, been poorly documented. We have previously shown that lymphocytes and monocytes/macrophages differ in their expression of CD4 monomers and dimers. In the present study, we have shown further significant differences. Variability in the blocking of CD4 mAb binding by sulfated polyanions indicated differences in exofacial CD4 structures. In contrast to the well-documented 55 kDa monomers in lymphocytic cells, monocytic cells were found to coexpress two monomer isoforms: the 55 kDa form and a novel 59 kDa species. Experimental uncoupling of CD4 disulfides indicated that the oxidized 55 kDa monomer could be converted to the 59 kDa form. This was achieved by chemical reduction of purified native or recombinant CD4, or in cell transfection experiments by mutation of cysteine to alanine in domain 1 (D1) (Cys16 or Cys84) and in domain 4 (D4) (Cys303 or Cys345). All of these modifications promote CD4 distension on SDS-PAGE analysis and indicate that, when CD4 inter-beta-sheet disulfides in the D1 and D4 Ig folds are disrupted, there is an unravelling of the oxidized form to an extended 59 kDa unfolded state. We hypothesize that this may be a transition-state, structural-intermediate in the formation of disulfide-linked homodimers. Also identified were CD4-tyrosine kinase dissimilarities in which lymphocyte CD4 associated with Lck, but monocyte CD4 associated with HcK. These findings show that there is complex heterogeneity in structures and interactions in the CD4 of T lymphocytes and monocytes.
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Affiliation(s)
- Garry W Lynch
- HIV-Protein Interactions Laboratory, Westmead Millennium Institute, Westmead, Australia.
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Maekawa A, Schmidt B, Fazekas de St Groth B, Sanejouand YH, Hogg PJ. Evidence for a Domain-Swapped CD4 Dimer as the Coreceptor for Binding to Class II MHC. THE JOURNAL OF IMMUNOLOGY 2006; 176:6873-8. [PMID: 16709847 DOI: 10.4049/jimmunol.176.11.6873] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
CD4 is a coreceptor for binding of T cells to APC and the primary receptor for HIV. The disulfide bond in the second extracellular domain (D2) of CD4 is reduced on the cell surface, which leads to formation of disulfide-linked homodimers. A large conformational change must take place in D2 to allow for formation of the disulfide-linked dimer. Domain swapping of D2 is the most likely candidate for the conformational change leading to formation of two disulfide-bonds between Cys130 in one monomer and Cys159 in the other one. Mild reduction of the extracellular part of CD4 resulted in formation of disulfide-linked dimers, which supports the domain-swapped model. The functional significance of dimer formation for coreceptor function was tested using cells expressing wild-type or disulfide-bond mutant CD4. Eliminating the D2 disulfide bond markedly impaired CD4's coreceptor function. Modeling of the complex of the TCR and domain-swapped CD4 dimer bound to class II MHC and Ag supports the domain-swapped dimer as the immune coreceptor. The known involvement of D4 residues Lys318 and Gln344 in dimer formation is also accommodated by this model. These findings imply that disulfide-linked dimeric CD4 is the preferred coreceptor for binding to APC.
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Affiliation(s)
- Akiko Maekawa
- Centre for Vascular Research, University of New South Wales, Sydney, Australia
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Sloane AJ, Raso V, Dimitrov DS, Xiao X, Deo S, Muljadi N, Restuccia D, Turville S, Kearney C, Broder CC, Zoellner H, Cunningham AL, Bendall L, Lynch GW. Marked structural and functional heterogeneity in CXCR4: separation of HIV-1 and SDF-1alpha responses. Immunol Cell Biol 2005; 83:129-43. [PMID: 15748209 DOI: 10.1111/j.1440-1711.2004.01304.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
CXCR4, the chemotactic cell receptor for SDF-1alpha, is essential for immune trafficking and HIV infection. CXCR4 is remarkably heterogeneous and the purpose of this study was to better identify the isoforms expressed by cells and compare their structure and function. We found that cells express either a predominant isoform or multiple isoforms. These were best resolved on SDS-PAGE using sucrose-gradient-fractionated, triton-insoluble, membrane extracts. We hypothesized that glycosyl modification may underpin some of this heterogeneity and that cell isoform(s) differences may underscore CXCR4's multiple cell functions. A comparison of wild-type (WT) and dual N-linked glycosylation site, N11A/N176A, mutant CXCR4 expressed in 3T3 and HEK-293 cells served to implicate variabilities in glycosylation and oligomerization in almost half of the isoforms. Immunoprecipitation of CXCR4 revealed monomer and dimer non-glycosylated forms of 34 kDa and 68 kDa from the N11A/N176A mutant, compared with glycosylated 40 kDa and 47 kDa and 73 kDa and 80 kDa forms from WT. The functional specificity of isoform action was also implicated because, despite CEMT4 cells expressing high levels of CXCR4 and 11 different isoforms, a single 83 kDa form was found to bind gp120 for HIV-1 IIIB infection. Furthermore, comparative studies found that in contrast to SDF-1alpha-responsive Nalm-6 cells that expressed similar levels of a single isoform, CEMT4 cells did not show a Ca(++) flux or a chemotactic response to SDF-1alpha. Thus, CXCR4 can differ both structurally and functionally between cells, with HIV-1 infection and chemotaxis apparently mediated by different isoforms. This separation of structure and function has implications for understanding HIV-1 entry and SDF-1alpha responses and may indicate therapeutic possibilities.
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Affiliation(s)
- Andrew J Sloane
- HIV-Protein Interactions Laboratory, Centre for Virus Research, Westmead, NSW, Australia
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Lynch GW, Slaytor EK, Elliott FD, Saurajen A, Turville SG, Sloane AJ, Cameron PU, Cunningham AL, Halliday GM. CD4 is expressed by epidermal Langerhans' cells predominantly as covalent dimers. Exp Dermatol 2003; 12:700-11. [PMID: 14705812 DOI: 10.1034/j.1600-0625.2003.00078.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Langerhans' cells (LC) of skin are CD4 expressing, dendritic, antigen-presenting cells, that are essential for activation of primary immune responses and are productively infected by HIV. We have shown previously that lymphocytes and monocytes express CD4 both as monomers and covalently linked homodimers. In those cells the 55-kDa monomer structure predominates. LC in un-fractionated human epidermal cell (EC) suspension also expresses both forms of CD4, but in EC the dimer form is predominant. Because isolation of LC into single cell suspension by trypsin, as is routinely used for LC isolation, degrades CD4, a systematic study for an alternate procedure for LC isolation was performed. Thus it was found that collagenase blend F treatment can efficiently release LC into suspension, under conditions of only minimal degradation of control soluble recombinant CD4 or CEM-T4 or THP-1 cell CD4, or importantly of LC surface CD4. SDS-PAGE immunoblotting of purified LC extracted from EC by collagenase confirmed CD4 structure as predominantly 110-kDa dimers, with only minimal 55-kDa monomers. The suitability of LC prepared thus for functional studies was demonstrated with binding of functional ligand HIV gp120. It remains to be determined, however, why tissue embedded LC express mainly CD4 dimers, but single-celled blood lymphocytes and monocytes mainly monomers.
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Affiliation(s)
- G W Lynch
- Centre for Virus Research, Westmead Millennium Institute, University of Sydney, Westmead Hospital, Sydney, Australia.
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Lapham CK, Romantseva T, Petricoin E, King LR, Manischewitz J, Zaitseva MB, Golding H. CXCR4 heterogeneity in primary cells: possible role of ubiquitination. J Leukoc Biol 2002. [DOI: 10.1189/jlb.72.6.1206] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Cheryl K. Lapham
- Divisions of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland and
| | - Tatiana Romantseva
- Divisions of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland and
| | - Emmanuel Petricoin
- Divisions of Cytokine Biology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland
| | - Lisa R. King
- Divisions of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland and
| | - Jody Manischewitz
- Divisions of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland and
| | - Marina B. Zaitseva
- Divisions of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland and
| | - Hana Golding
- Divisions of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland and
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Cunningham AL, Li S, Juarez J, Lynch G, Alali M, Naif H. The level of HIV infection of macrophages is determined by interaction of viral and host cell genotypes. J Leukoc Biol 2000. [DOI: 10.1189/jlb.68.3.311] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- A. L. Cunningham
- Centre for Virus Research, The Westmead Millennium Institute, University of Sydney, and The Australian National Centre for HIV Research, Sydney, Australia
| | - S Li
- Centre for Virus Research, The Westmead Millennium Institute, University of Sydney, and The Australian National Centre for HIV Research, Sydney, Australia
| | - J Juarez
- Centre for Virus Research, The Westmead Millennium Institute, University of Sydney, and The Australian National Centre for HIV Research, Sydney, Australia
| | - G Lynch
- Centre for Virus Research, The Westmead Millennium Institute, University of Sydney, and The Australian National Centre for HIV Research, Sydney, Australia
| | - M. Alali
- Centre for Virus Research, The Westmead Millennium Institute, University of Sydney, and The Australian National Centre for HIV Research, Sydney, Australia
| | - H. Naif
- Centre for Virus Research, The Westmead Millennium Institute, University of Sydney, and The Australian National Centre for HIV Research, Sydney, Australia
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Schamel WW. Detection of proteins after biotinylation within polyacrylamide gels (BIG method). Anal Biochem 1999; 274:144-6. [PMID: 10527509 DOI: 10.1006/abio.1999.4238] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- W W Schamel
- Department of Molecular Immunology, University of Freiburg and Max-Planck-Institut für Immunbiologie, Stübeweg 51, Freiburg, 79108, Germany
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10
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Abstract
CD4 is expressed by T lymphocytes and monocytes and is generally considered a monomer even though its structure was originally modelled on the REI Bence-Jones homodimer. However, native CD4 was demonstrated as both monomer and dimers of 55 and 110 kDa in lymphoid and monocytoid cells by immunoprecipitation and immunoblotting after solubilization with alkylating (iodoacetamide) or reducing (dithiothreitol, 2-mercaptoethanol) reagents. Full reduction yielded only the 55-kDa monomeric form. Purified CD4 oligomers from CEM-T4 cells were also resolved as homodimers by MALDI-Tof mass fingerprinting after tryptic digestion. Cell treatment with the membrane impermeable, free-thiol reactive, 5,5'-dithiobis-2-nitrobenzoic acid enhanced cell surface CD4 dimers and tetramers. The interaction sites producing dimerization were probably in the D4 domain as OKT4 inhibited self association of recombinant CD4 (rCD4). Oligomerization of rCD4 by glutathione and thioredoxin indicates that thiol exchange interactions were responsible. Enhanced CD4 dimer expression was also observed after PMA (20 ng/ml) activation of THP-1 cells. These findings demonstrate that different quaternary forms of CD4 such as monomers, homodimers and tetramers are expressed by T lymphocytes and monocytes/macrophages.
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Affiliation(s)
- G W Lynch
- Centre for Virus Research, Westmead Institutes of Health Research, Westmead Hospital and University of Sydney, Sydney, Australia.
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