title: Crystal Structure of the cis-Dimer of Nectin-1: implications for the architecture of cell-cell junctions.
abstract: In multicellular organisms, cells are interconnected by cell adhesion molecules. Nectins are immunoglobulin (Ig)-like cell adhesion molecules that mediate homotypic and heterotypic cell-cell adhesion, playing key roles in tissue organization. To mediate cell-cell adhesion, nectin molecules dimerize in cis on the surface of the same cell, followed by trans-dimerization of the cis-dimers between the neighboring cells. Previous cell biological studies deduced that the first Ig-like domain of nectin and the second Ig-like domain are involved in trans-dimerization and cis-dimerization, respectively. However, to understand better the steps involved in nectin adhesion, the structural basis for the dimerization of nectin must be determined. In this study, we determined the first crystal structure of the entire extracellular region of nectin-1. In the crystal, nectin-1 formed a V-shaped homophilic dimer through the first Ig-like domain. Structure-based site-directed mutagenesis of the first Ig-like domain identified four essential residues that are involved in the homophilic dimerization. Upon mutating the four residues, nectin-1 significantly decreased cis-dimerization on the surface of cultured cells and abolished the homophilic and heterophilic adhesion activities. These results indicate that, in contrast with the previous notion, our structure represents a cis-dimer. Thus, our findings clearly reveal the structural basis for the cis-dimerization of nectins through the first Ig-like domains.
authors.affiliation: Laboratory of Supramolecular Crystallography, Research Center for Structural and Functional Proteomics, Institute for Protein Research, Osaka University, Suita 565-0871, Japan.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Narita
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Mamoru
authors.initials: M
authors.lastname: Suzuki
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Miyazaki
authors.forename: Asuka
authors.initials: A
authors.lastname: Yoshida
authors.forename: Katsuhisa
authors.initials: K
authors.lastname: Kawai
authors.forename: Kenji
authors.initials: K
authors.lastname: Iwasaki
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nakagawa
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Takai
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Sakisaka
mesh_terms: D000818:Animals; D015815:Cell Adhesion Molecules / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002449:Cell Aggregation / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D002850:Chromatography, Gel; D018360:Crystallography, X-Ray; D006801:Humans; D006860:Hydrogen Bonding; D007365:Intercellular Junctions / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008856:Microscopy, Fluorescence; D000075983:Nectins; D016900:Neurofilament Proteins / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D055503:Protein Multimerization / Q000235:genetics / Q000502:physiology; D017433:Protein Structure, Secondary; D014461:Ultracentrifugation
chemical_list: D015815:Cell Adhesion Molecules; C000619010:NECTIN1 protein, human; C000619015:Nectin1 protein, mouse; D000075983:Nectins; D016900:Neurofilament Proteins; C061195:neurofilament protein M