title: Different domains of CD81 mediate distinct stages of hepatitis C virus pseudoparticle entry.
abstract: The CD81 tetraspanin was first identified as a hepatitis C virus (HCV) receptor by its ability to bind the soluble ectodomain of envelope glycoprotein E2 (sE2). More recently, it has been suggested that CD81 is necessary but not sufficient for HCV entry into target cells. Here we present further evidence that putative human hepatocyte-specific factors act in concert with CD81 to mediate sE2 binding and HCV pseudoparticle (HCVpp) entry. Moreover, we show that CD81-mediated HCVpp entry entails E2 binding to residues in the large extracellular loop as well as molecular events mediated by the transmembrane and intracellular domains of CD81. The concept that CD81 receptor function progresses in stages is further supported by our finding that anti-CD81 monoclonal antibodies inhibit HCVpp entry by different mechanisms. The half-life of CD81-HCVpp binding was determined to be approximately 17 min, and we propose that binding is followed by CD81 oligomerization, partitioning into cholesterol-rich membrane domains, or other, lateral protein-protein interactions. This results in the formation of a receptor-virus complex that undergoes endocytosis and pH-dependent membrane fusion.
authors.affiliation: Albert Einstein College of Medicine, Department of Microbiology and Immunology, Bronx, NY 10461, USA.
authors.forename: Claire
authors.initials: C
authors.lastname: Bertaux
authors.forename: Tatjana
authors.initials: T
authors.lastname: Dragic
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D015703:Antigens, CD / Q000096:biosynthesis / Q000276:immunology / Q000502:physiology*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism / Q000821:virology; D005110:Extracellular Space / Q000378:metabolism / Q000821:virology; D015967:Gene Expression Regulation, Viral; D016174:Hepacivirus / Q000472:pathogenicity* / Q000502:physiology*; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism / Q000821:virology; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D060225:Tetraspanin 28; D020298:U937 Cells; D014759:Viral Envelope Proteins / Q000378:metabolism; D014771:Virion / Q000472:pathogenicity / Q000502:physiology*
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; C554798:CD81 protein, human; C554799:Cd81 protein, mouse; D060225:Tetraspanin 28; D014759:Viral Envelope Proteins; C091015:glycoprotein E2, Hepatitis C virus