title: Resolving cadherin interactions and binding cooperativity at the single-molecule level.
abstract: The cadherin family of Ca(2+)-dependent cell adhesion proteins are critical for the morphogenesis and functional organization of tissues in multicellular organisms, but the molecular interactions between cadherins that are at the core of cell-cell adhesion are a matter of considerable debate. A widely-accepted model is that cadherins adhere in 3 stages. First, the functional unit of cadherin adhesion is a cis dimer formed by the binding of the extracellular regions of 2 cadherins on the same cell surface. Second, formation of low-affinity trans interactions between cadherin cis dimers on opposing cell surfaces initiates cell-cell adhesion. Third, lateral clustering of cadherins cooperatively strengthens intercellular adhesion. Evidence of these cadherin binding states during adhesion is, however, contradictory, and evidence for cooperativity is lacking. We used single-molecule structural (fluorescence resonance energy transfer) and functional (atomic force microscopy) assays to demonstrate directly that cadherin monomers interact via their N-terminal EC1 domain to form trans adhesive complexes. We could not detect the formation of cadherin cis dimers, but found that increasing the density of cadherin monomers cooperatively increased the probability of trans adhesive binding.
authors.affiliation: Department of Physics, Stanford University, Stanford, CA 94305, USA.
authors.forename: Yunxiang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Sanjeevi
authors.initials: S
authors.lastname: Sivasankar
authors.forename: W James
authors.initials: WJ
authors.lastname: Nelson
authors.forename: Steven
authors.initials: S
authors.lastname: Chu
mesh_terms: D015820:Cadherins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D019281:Dimerization; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D018625:Microscopy, Atomic Force; D008956:Models, Chemical; D046912:Multiprotein Complexes; D011485:Protein Binding; D015202:Protein Engineering; D054730:Protein Interaction Domains and Motifs / Q000502:physiology; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D014162:Transfection
chemical_list: D015820:Cadherins; D046912:Multiprotein Complexes