title: An alanine-to-proline mutation in the BB-loop of TLR3 Toll/IL-1R domain switches signalling adaptor specificity from TRIF to MyD88.
abstract: A functionally important proline residue is highly conserved in the cytosolic Toll/IL-1R signaling domains of human TLRs. The antiviral Toll, TLR3, is unusual because it has alanine instead of proline at this position and is the only human TLR that associates directly with the adaptor molecule TIR domain-containing adaptor inducing IFN-β (TRIF) rather than MyD88. In this article, we report that a mutant TLR3 that substitutes the BB-loop alanine for proline (A795P) enhances NF-κB activation but is incapable of mediating TRIF-dependent IFN response factor 3 responses. Wild-type and A795P TLR3 associate constitutively with both TRIF and MyD88, and activation induces additional binding of TRIF to the wild-type and of MyD88 to the A795P mutant receptors, respectively. In addition, activation of A795P, but not wild-type TLR3, leads to the recruitment of TRAF6, a downstream signal transducer of the MyD88-dependent pathway. These results show that adaptor specificity can be conferred by minimal determinants of the Toll/IL-1R domain.
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, United Kingdom.
authors.forename: Brett
authors.initials: B
authors.lastname: Verstak
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Arnot
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Gay
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000037:antagonists & inhibitors / Q000502:physiology; D000409:Alanine / Q000737:chemistry; D019943:Amino Acid Substitution; D001665:Binding Sites; D057809:HEK293 Cells; D006801:Humans; D050838:Interferon Regulatory Factor-3 / Q000502:physiology; D020125:Mutation, Missense; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism; D016328:NF-kappa B / Q000502:physiology; D017354:Point Mutation; D011070:Poly I-C / Q000494:pharmacology; D011392:Proline / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D013045:Species Specificity; D013329:Structure-Activity Relationship; D048029:TNF Receptor-Associated Factor 6 / Q000378:metabolism; D051196:Toll-Like Receptor 3 / Q000737:chemistry / Q000235:genetics* / Q000502:physiology
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D050838:Interferon Regulatory Factor-3; C494233:Irf3 protein, mouse; C507779:MYD88 protein, human; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D011993:Recombinant Fusion Proteins; C470409:TICAM1 protein, human; C495344:TLR3 protein, human; D048029:TNF Receptor-Associated Factor 6; D051196:Toll-Like Receptor 3; D011392:Proline; D011070:Poly I-C; D000409:Alanine