title: Reconstructing the TIR Side of the Myddosome: a Paradigm for TIR-TIR Interactions.
abstract: Members of the Toll-like receptor and interleukin-1 (IL-1) receptor families all signal via Toll/IL-1R (TIR) domain-driven assemblies with adaptors such as MyD88. We here combine the mammalian two-hybrid system MAPPIT and saturation mutagenesis to complement and extend crystallographic and nuclear magnetic resonance data, and reveal how TIR domains interact. We fully delineate the interaction sites on the MyD88 TIR domain for homo-oligomerization and for interaction with Mal and TLR4. Interactions between three sites drive MyD88 homo-oligomerization. The BB-loop interacts with the αE-helix, explaining how BB-loop mimetics inhibit MyD88 signaling. The αC'-helix interacts symmetrically. The MyD88 TIR domains thus assemble into a left-handed helix, compatible with the Myddosome death domain crystal structure. This assembly explains activation of MyD88 by Mal and by an oncogenic mutation, and regulation by phosphorylation. These findings provide a paradigm for the interaction of mammalian TIR domains.
authors.affiliation: Department of Medical Protein Research, Cytokine Receptor Lab, VIB, A. Baertsoenkaai 3, 9000 Ghent, Belgium; Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, 9000 Ghent, Belgium.
authors.forename: Laurens
authors.initials: L
authors.lastname: Vyncke
authors.affiliation: Department of Medical Protein Research, Cytokine Receptor Lab, VIB, A. Baertsoenkaai 3, 9000 Ghent, Belgium; Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, 9000 Ghent, Belgium.
authors.forename: Celia
authors.initials: C
authors.lastname: Bovijn
authors.affiliation: Center for Molecular Modeling, Ghent University, Technologiepark 903, 9052 Zwijnaarde, Belgium.
authors.forename: Ewald
authors.initials: E
authors.lastname: Pauwels
authors.affiliation: Department of Medical Protein Research, Cytokine Receptor Lab, VIB, A. Baertsoenkaai 3, 9000 Ghent, Belgium; Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, 9000 Ghent, Belgium.
authors.forename: Tim
authors.initials: T
authors.lastname: Van Acker
authors.affiliation: Department of Medical Protein Research, Cytokine Receptor Lab, VIB, A. Baertsoenkaai 3, 9000 Ghent, Belgium; Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, 9000 Ghent, Belgium.
authors.forename: Elien
authors.initials: E
authors.lastname: Ruyssinck
authors.affiliation: Department of Medical Protein Research, Cytokine Receptor Lab, VIB, A. Baertsoenkaai 3, 9000 Ghent, Belgium; Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, 9000 Ghent, Belgium.
authors.forename: Elianne
authors.initials: E
authors.lastname: Burg
authors.affiliation: Department of Medical Protein Research, Cytokine Receptor Lab, VIB, A. Baertsoenkaai 3, 9000 Ghent, Belgium; Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, 9000 Ghent, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: Tavernier
authors.affiliation: Department of Medical Protein Research, Cytokine Receptor Lab, VIB, A. Baertsoenkaai 3, 9000 Ghent, Belgium; Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, 9000 Ghent, Belgium. Electronic address: frank.peelman@vib-ugent.be.
authors.forename: Frank
authors.initials: F
authors.lastname: Peelman
mesh_terms: D001665:Binding Sites; D057809:HEK293 Cells; D006801:Humans; D008958:Models, Molecular; D062105:Molecular Docking Simulation; D009154:Mutation; D062806:Myelin and Lymphocyte-Associated Proteolipid Proteins / Q000378:metabolism*; D053594:Myeloid Differentiation Factor 88 / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D000072417:Protein Domains; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D051197:Toll-Like Receptor 4 / Q000378:metabolism
chemical_list: C569026:MAL protein, human; C507779:MYD88 protein, human; D062806:Myelin and Lymphocyte-Associated Proteolipid Proteins; D053594:Myeloid Differentiation Factor 88; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4