title: Structural basis of ligand interactions of the large extracellular domain of tetraspanin CD81.
abstract: Hepatitis C virus (HCV) causes chronic liver disease, cirrhosis, and primary liver cancer. Despite 130 million people being at risk worldwide, no vaccine exists, and effective therapy is limited by drug resistance, toxicity, and high costs. The tetraspanin CD81 is an essential entry-level receptor required for HCV infection of hepatocytes and represents a critical target for intervention. In this study, we report the first structural characterization of the large extracellular loop of CD81, expressed in mammalian cells and studied in physiological solutions. The HCV E2 glycoprotein recognizes CD81 through a dynamic loop on the helical bundle, which was shown by nuclear magnetic resonance (NMR) spectroscopy to adopt a conformation distinct from that seen in crystals. A novel membrane binding interface was revealed adjacent to the exposed HCV interaction site in the extracellular loop of CD81. The binding pockets for two proposed inhibitors of the CD81-HCV interaction, namely, benzyl salicylate and fexofenadine, were shown to overlap the HCV and membrane interaction sites. Although the dynamic loop region targeted by these compounds presents challenges for structure-based design, the NMR assignments enable realistic screening and validation of ligands. Together, these data provide an improved avenue for developing potent agents that specifically block CD81-HCV interaction and also pave a way for elucidating the recognition mechanisms of diverse tetraspanins.
authors: School of Cancer Sciences, The University of Birmingham, Edgbaston, Birmingham, United Kingdom.
authors: Sundaresan
authors: S
authors: Rajesh
authors: Pooja
authors: P
authors: Sridhar
authors: Birke Andrea
authors: BA
authors: Tews
authors: Lucie
authors: L
authors: Fénéant
authors: Laurence
authors: L
authors: Cocquerel
authors: Douglas G
authors: DG
authors: Ward
authors: Fedor
authors: F
authors: Berditchevski
authors: Michael
authors: M
authors: Overduin
mesh_terms: D001665:Binding Sites; D057809:HEK293 Cells; D016174:Hepacivirus / Q000378:metabolism* / Q000472:pathogenicity; D022781:Hepatocytes / Q000378:metabolism / Q000821:virology; D054884:Host-Pathogen Interactions; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D054730:Protein Interaction Domains and Motifs; D011991:Receptors, Virus / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D060225:Tetraspanin 28 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D014759:Viral Envelope Proteins / Q000378:metabolism*
chemical_list: C554798:CD81 protein, human; D008024:Ligands; D011991:Receptors, Virus; D011994:Recombinant Proteins; D060225:Tetraspanin 28; D014759:Viral Envelope Proteins; C091015:glycoprotein E2, Hepatitis C virus