title: Identification of interaction sites for dimerization and adapter recruitment in Toll/interleukin-1 receptor (TIR) domain of Toll-like receptor 4.
abstract: Toll-like receptor signaling requires interactions of the Toll/IL-1 receptor (TIR) domains of the receptor and adapter proteins. Using the mammalian protein-protein interaction trap strategy, homology modeling, and site-directed mutagenesis, we identify the interaction surfaces in the TLR4 TIR domain for the TLR4-TLR4, TLR4-MyD88 adapter-like (MAL), and TLR4-TRIF-related adapter molecule (TRAM) interaction. Two binding sites are equally important for TLR4 dimerization and adapter recruitment. In a model based on the crystal structure of the dimeric TLR10 TIR domain, the first binding site mediates TLR4-TLR4 TIR-TIR interaction. Upon dimerization, two identical second binding sites of the TLR4 TIR domain are juxtaposed and form an extended binding platform for both MAL and TRAM. In our mammalian protein-protein interaction trap assay, MAL and TRAM compete for binding to this platform. Our data suggest that adapter binding can stabilize the TLR4 TIR dimerization.
authors.affiliation: Department of Medical Protein Research, Unit of Molecular Signal Transduction in Inflammation, Flanders Interuniversity Institute for Biotechnology, Ghent University, B-9000 Ghent, Belgium.
authors.forename: Celia
authors.initials: C
authors.lastname: Bovijn
authors.forename: Peter
authors.initials: P
authors.lastname: Ulrichts
authors.forename: Anne-Sophie
authors.initials: AS
authors.lastname: De Smet
authors.forename: Dominiek
authors.initials: D
authors.lastname: Catteeuw
authors.forename: Rudi
authors.initials: R
authors.lastname: Beyaert
authors.forename: Jan
authors.initials: J
authors.lastname: Tavernier
authors.forename: Frank
authors.initials: F
authors.lastname: Peelman
mesh_terms: D000818:Animals; D006801:Humans; D051379:Mice; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D053594:Myeloid Differentiation Factor 88 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010449:Peptide Mapping; D055503:Protein Multimerization / Q000502:physiology*; D017434:Protein Structure, Tertiary; D040681:Structural Homology, Protein; D051201:Toll-Like Receptor 10 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: C507779:MYD88 protein, human; D053594:Myeloid Differentiation Factor 88; C475955:TLR10 protein, human; C495345:TLR4 protein, human; D051201:Toll-Like Receptor 10; D051197:Toll-Like Receptor 4