Peptide-mediated interference of TIR domain dimerization in MyD88 inhibits interleukin-1-dependent activation of NF-{kappa}B

• Published in: The Journal of biological chemistry 2005-04, Vol.280 (16), p.15809-15814
• Main Authors: Loiarro, Maria, Sette, Claudio, Gallo, Grazia, Ciacci, Andrea, Fantò, Nicola, Mastroianni, Domenico, Carminati, Paolo, Ruggiero, Vito
• Format: Article
• Language: English
• Subjects: Adaptor Proteins, Signal Transducing; Amino Acid Sequence; Antennapedia Homeodomain Protein; Antigens, Differentiation - genetics; Antigens, Differentiation - metabolism; Dimerization; Homeodomain Proteins - genetics; Homeodomain Proteins - metabolism; Interleukin-1 - metabolism; Membrane Glycoproteins - genetics; Molecular Sequence Data; Myeloid Differentiation Factor 88; NF-kappa B - metabolism; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Peptides - metabolism; Protein Structure, Tertiary; Receptors, Cell Surface - genetics; Receptors, Immunologic - genetics; Receptors, Immunologic - metabolism; Receptors, Interleukin-1 - genetics; Sequence Alignment; Toll-Like Receptors; Transcription Factors - genetics; Transcription Factors - metabolism
• ISSN: 0021-9258

Myeloid differentiation factor 88 (MyD88) plays a crucial role in the signaling pathways triggered by interleukin (IL)-1 and Toll-like receptors in several steps of innate host defense. A crucial event in this signaling pathway is represented by dimerization of MyD88, which allows the recruitment of downstream kinases like IRAK-1 and IRAK-4. Herein, we have investigated the function of the Toll/IL-1 receptor (TIR) domain in MyD88 homodimerization in cell-free and in vitro experimental settings by using epta-peptides that mimic the BB-loop region of the conserved TIR domain of different proteins. By using a pull-down assay with purified glutathione S-transferase-MyD88 TIR or co-immunoprecipitation experiments, we found that epta-peptides derived from the TIR domain of MyD88 and IL-18R are the most effective in inhibiting homodimerization with either the isolated TIR or full-length MyD88. Moreover, we demonstrated that a cell permeable analog of MyD88 epta-peptide inhibits homodimerization of MyD88 TIR domains in an in vitro cell system and significantly reduces IL-1 signaling, as assayed by activation of the downstream transcription factor NF-kappaB. Our results indicate that the BB-loop in TIR domain of MyD88 is a good target for specific inhibition of MyD88-mediated signaling in vivo.