title: The N-terminal loop of IRAK-4 death domain regulates ordered assembly of the Myddosome signalling scaffold.
abstract: Activation of Toll-like receptors induces dimerization and the recruitment of the death domain (DD) adaptor protein MyD88 into an oligomeric post receptor complex termed the Myddosome. The Myddosome is a hub for inflammatory and oncogenic signaling and has a hierarchical arrangement with 6-8 MyD88 molecules assembling with exactly 4 of IRAK-4 and 4 of IRAK-2. Here we show that a conserved motif in IRAK-4 (Ser8-X-X-X-Arg12) is autophosphorylated and that the phosphorylated DD is unable to form Myddosomes. Furthermore a mutant DD with the phospho-mimetic residue Asp at this position is impaired in both signalling and Myddosome assembly. IRAK-4 Arg12 is also essential for Myddosome assembly and signalling and we propose that phosphorylated Ser8 induces the N-terminal loop to fold into an α-helix. This conformer is stabilised by an electrostatic interaction between phospho-Ser8 and Arg12 and would destabilise a critical interface between IRAK-4 and MyD88. Interestingly IRAK-2 does not conserve this motif and has an alternative interface in the Myddosome that requires Arg67, a residue conserved in paralogues, IRAK-1 and 3(M).
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge, CB2 1GA, UK.|Molecular Discovery Research, GlaxoSmithKline R&D, Stevenage, SG1 2NY, UK.
authors.forename: Anthony C G
authors.initials: AC
authors.lastname: Dossang
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge, CB2 1GA, UK.|Department of Biochemistry, University of Pretoria, South Africa.
authors.forename: Precious G
authors.initials: PG
authors.lastname: Motshwene
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge, CB2 1GA, UK.
authors.forename: Yang
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge, CB2 1GA, UK.
authors.forename: Martyn F
authors.initials: MF
authors.lastname: Symmons
authors.affiliation: Department of Veterinary Medicine, University of Cambridge, Cambridge, CB2 1GA, UK.
authors.forename: Clare E
authors.initials: CE
authors.lastname: Bryant
authors.affiliation: Molecular Discovery Research, GlaxoSmithKline R&D, Stevenage, SG1 2NY, UK.
authors.forename: Satty
authors.initials: S
authors.lastname: Borman
authors.affiliation: Junior Research Group Toll-Like Receptors and Cancer, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 580, 69120 Heidelberg, Germany.
authors.forename: Julie
authors.initials: J
authors.lastname: George
authors.affiliation: Interfaculty Institute for Cell Biology, Department of Immunology, University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany.
authors.forename: Alexander N R
authors.initials: AN
authors.lastname: Weber
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge, CB2 1GA, UK.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Gay
mesh_terms: D020816:Amino Acid Motifs; D006801:Humans; D053592:Interleukin-1 Receptor-Associated Kinases / Q000737:chemistry* / Q000378:metabolism; D046912:Multiprotein Complexes / Q000737:chemistry* / Q000378:metabolism; D053594:Myeloid Differentiation Factor 88 / Q000737:chemistry* / Q000378:metabolism; D020836:Protein Structure, Quaternary; D015398:Signal Transduction; D055672:Static Electricity
chemical_list: C507779:MYD88 protein, human; D046912:Multiprotein Complexes; D053594:Myeloid Differentiation Factor 88; C507773:IRAK4 protein, human; D053592:Interleukin-1 Receptor-Associated Kinases