Specific binding of the WASP N-terminal domain to Btk is critical for TLR2 signaling in macrophages.

[wiskott-aldrich syndrome]

Wiskott-Aldrich syndrome protein (WASP ) is an adaptor molecule in immune cells . Recently , we revealed that WASP is involved in lipopolysaccharide-TLR 4 signaling in macrophages by association of Bruton 's tyrosine kinase (Btk ) with the WASP N-terminal domain . Btk has been shown to play important roles in the signaling of several TLRs and to modulate the inflammatory response in macrophages . In this study , we evaluated the importance of the interaction between Btk and WASP in TLR 2 signaling by using bone marrow-derived macrophage cell lines from transgenic (Tg ) mice expressing anti-WASP N-terminal domain single -chain variable fragment (scFv ) or VL single -domain intrabodies . In this Tg bone marrow-derived macrophages , specific interaction between WASP and Btk were strongly inhibited by masking of the binding site in the WASP N-terminal domain . There was impairment of gene expression of TNF -α , IL -6 , and IL -1 β and phosphorylation of inhibitor of κB α /β (IKK α /β ) and nuclear factor (NF )-κB upon stimulation with TLR 2 ligands . Furthermore , tyrosine phosphorylation of WASP following TLR 2 -ligand stimulation was severely inhibited in the Tg bone marrow-derived macrophages , as shown by the impairment in WASP tyrosine phosphorylation following lipopolysaccharide stimulation . These results strongly suggest that the association between the WASP N-terminal domain and Btk plays an important role in the TLR 2 -signaling pathway in macrophages .