title: CD81 and claudin 1 coreceptor association: role in hepatitis C virus entry.
abstract: Hepatitis C virus (HCV) is an enveloped positive-stranded RNA hepatotropic virus. HCV pseudoparticles infect liver-derived cells, supporting a model in which liver-specific molecules define HCV internalization. Three host cell molecules have been reported to be important entry factors or receptors for HCV internalization: scavenger receptor BI, the tetraspanin CD81, and the tight junction protein claudin-1 (CLDN1). None of the receptors are uniquely expressed within the liver, leading us to hypothesize that their organization within hepatocytes may explain receptor activity. Since CD81 and CLDN1 act as coreceptors during late stages in the entry process, we investigated their association in a variety of cell lines and human liver tissue. Imaging techniques that take advantage of fluorescence resonance energy transfer (FRET) to study protein-protein interactions have been developed. Aequorea coerulescens green fluorescent protein- and Discosoma sp. red-monomer fluorescent protein-tagged forms of CD81 and CLDN1 colocalized, and FRET occurred between the tagged coreceptors at comparable frequencies in permissive and nonpermissive cells, consistent with the formation of coreceptor complexes. FRET occurred between antibodies specific for CD81 and CLDN1 bound to human liver tissue, suggesting the presence of coreceptor complexes in liver tissue. HCV infection and treatment of Huh-7.5 cells with recombinant HCV E1-E2 glycoproteins and anti-CD81 monoclonal antibody modulated homotypic (CD81-CD81) and heterotypic (CD81-CLDN1) coreceptor protein association(s) at specific cellular locations, suggesting distinct roles in the viral entry process.
authors.affiliation: University of Birmingham, Division of Infection and Immunity, Institute for Biomedical Research, Vincent Dr., Birmingham B15 2TT, United Kingdom.
authors.forename: Helen J
authors.initials: HJ
authors.lastname: Harris
authors.forename: Michelle J
authors.initials: MJ
authors.lastname: Farquhar
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Mee
authors.forename: Christopher
authors.initials: C
authors.lastname: Davis
authors.forename: Gary M
authors.initials: GM
authors.lastname: Reynolds
authors.forename: Adam
authors.initials: A
authors.lastname: Jennings
authors.forename: Ke
authors.initials: K
authors.lastname: Hu
authors.forename: Fei
authors.initials: F
authors.lastname: Yuan
authors.forename: HongKui
authors.initials: H
authors.lastname: Deng
authors.forename: Stefan G
authors.initials: SG
authors.lastname: Hubscher
authors.forename: Jang H
authors.initials: JH
authors.lastname: Han
authors.forename: Peter
authors.initials: P
authors.lastname: Balfe
authors.forename: Jane A
authors.initials: JA
authors.lastname: McKeating
mesh_terms: D015703:Antigens, CD / Q000032:analysis*; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry*; D002478:Cells, Cultured; D062445:Claudin-1; D031541:Fluorescence Resonance Energy Transfer; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D016174:Hepacivirus / Q000502:physiology*; D022781:Hepatocytes / Q000737:chemistry; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000032:analysis*; D011991:Receptors, Virus / Q000032:analysis*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D060225:Tetraspanin 28; D053586:Virus Internalization; D000097573:Red Fluorescent Protein
chemical_list: D015703:Antigens, CD; D062445:Claudin-1; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D008565:Membrane Proteins; D011991:Receptors, Virus; D011993:Recombinant Fusion Proteins; D060225:Tetraspanin 28; D000097573:Red Fluorescent Protein; C554798:CD81 protein, human; C568108:CLDN1 protein, human