title: Determinants of CD81 dimerization and interaction with hepatitis C virus glycoprotein E2.
abstract: The tetraspanin CD81 plays an essential role in diverse cellular processes. CD81 also acts as an entry receptor for HCV through an interaction between the large extracellular loop (LEL) of CD81 and HCV glycoprotein E2. The E2-CD81 interaction also results in immunomodulatory effects in vitro. In this study, we examined the relationship between the dimeric crystal structure of the CD81 LEL and intact CD81. Using random mutagenesis, amino acids were identified that abolished dimerization of recombinant LEL in regions that were important for intermonomer contacts (F150S and V146E), salt bridge formation (K124T), and intramonomer disulfide bonding (T166I, C157S, and C190R). Two monomeric LEL mutants retained the ability to bind E2, K124T, and V146E, whereas F150S, T166I, C157S, and C190R did not. Introduction of K124T, V146E, and F150S mutations in full-length CD81 did not affect its oligomerization and the effects on E2 binding were less severe than for isolated LEL. These results suggest that the LEL has a more robust structure in the intact tetraspanin with regions outside the LEL contributing to CD81 dimerization.
authors.affiliation: St. Vincent's Institute of Medical Research, 41 Victoria Pde, Fitzroy 3065, Australia. hdrummer@burnet.edu.au
authors.forename: Heidi E
authors.initials: HE
authors.lastname: Drummer
authors.forename: Kirilee A
authors.initials: KA
authors.lastname: Wilson
authors.forename: Pantelis
authors.initials: P
authors.lastname: Poumbourios
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000818:Animals; D015703:Antigens, CD / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D019281:Dimerization; D006801:Humans; D007668:Kidney / Q000378:metabolism; D051379:Mice; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016297:Mutagenesis, Site-Directed; D041681:NIH 3T3 Cells; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship; D060225:Tetraspanin 28; D014759:Viral Envelope Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D015703:Antigens, CD; C554798:CD81 protein, human; C554799:Cd81 protein, mouse; D011994:Recombinant Proteins; D060225:Tetraspanin 28; D014759:Viral Envelope Proteins; C091015:glycoprotein E2, Hepatitis C virus