Etk/BMX, a Btk Family Tyrosine Kinase, and Mal Contribute to the Cross-Talk between MyD88 and FAK Pathways

Authors:
Semaan N, Alsaleh G, Gottenberg JE, Wachsmann D, Sibilia J
In:
Source: J Immunol
Publication Date: (2008)
Issue: 180(5): 3485-91
Research Area:
Cancer Research/Cell Biology
Immunotherapy / Hematology
Cells used in publication:
Fibroblast, synovial, human
Species: human
Tissue Origin:
Synoviocyte, human
Species: human
Tissue Origin:
Platform:
Nucleofector® I/II/2b
Abstract
MyD88 and focal adhesion kinase (FAK) are key adaptors involved in signaling downstream of TLR2, TLR4, and integrin alpha(5)beta(1), linking pathogen-associated molecule detection to the initiation of proinflammatory response. The MyD88 and integrin pathways are interlinked, but the mechanism of this cross-talk is not yet understood. In this study we addressed the involvement of Etk, which belongs to the Tec family of tyrosine kinases, in the cross-talk between the integrin/FAK and the MyD88 pathways in fibroblast-like synoviocyte s (FLS) and in IL-6 synthesis. Using small interfering RNA blockade, we report that Etk plays a major role in LPS- and protein I/II (a model activator of FAK)-dependent IL-6 release by activated FLS. Etk is associated with MyD88, FAK, and Mal as shown by coimmunoprecipitation. Interestingly, knockdown of Mal appreciably inhibited IL-6 synthesis in response to LPS and protein I/II. Our results also indicate that LPS and protein I/II induced phosphorylation of Etk and Mal in rheumatoid arthritis FLS via a FAK-dependent pathway. In conclusion, our data provide support that, in FLS, Etk and Mal are implicated in the cross-talk between FAK and MyD88 and that their being brought into play is clearly dependent on FAK.