Hck tyrosine kinase regulates TLR4-induced TNF and IL-6 production via AP-1.
The TLRs play a key role in host defense against infection and injury, and mounting evidence suggests that these receptors may also play a role in diseases such autoimmunity, atherosclerosis, and cancer. Activation of TLRs on macrophages results in the production of multiple soluble mediators including the key inflammatory cytokines, TNF and IL-6. Thus, the intracellular signaling mechanism by which TLRs signal is a subject of great interest. As well as activating the NF-κB and MAPK pathways, TLR engagement leads to tyrosine kinase activation within minutes. Src family kinases (SFKs) are the largest nonreceptor tyrosine kinase family with nine members: Src, Hck, Lyn, Fyn, Fgr, Blk, Lck, Yes, and Ylk. The role of the SFKs in TLR signaling has been an area of much controversy, with conflicting findings between studies using chemical inhibitors and knockout mice. Using primary human macrophages in combination with adenoviral overexpression and small interfering RNA knockdown studies, we show that the SFK, Hck, has a pre-eminent role in LPS/TLR4-induced TNF and IL-6 production. Hck kinase mediates TLR4-induced transcription of both TNF and IL-6 by a mechanism that involves neither the NF-κB nor the MAPK pathways, but rather leads to AP-1 binding with a complex of c-fos and JunD. These data highlight the importance of Hck as an active component in LPS-induced TLR signaling and suggest the possibility of targeting this kinase for the alleviation of excessive inflammation.
Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Kennedy Institute of Rheumatology, Oxford University, London W6 8LH, United Kingdom.
Maria J
MJ
Smolinska
Theresa H
TH
Page
Ania M
AM
Urbaniak
Brenda E
BE
Mutch
Nicole J
NJ
Horwood
D015153:Blotting, Western; D002478:Cells, Cultured; D024202:Electrophoretic Mobility Shift Assay; D004797:Enzyme-Linked Immunosorbent Assay; D015870:Gene Expression / Q000235:genetics / Q000276:immunology; D005786:Gene Expression Regulation / Q000235:genetics / Q000276:immunology; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology; D008264:Macrophages / Q000276:immunology / Q000378:metabolism; D051572:Proto-Oncogene Proteins c-hck / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D034622:RNA Interference; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction / Q000276:immunology; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology
D015850:Interleukin-6; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D018808:Transcription Factor AP-1; D014409:Tumor Necrosis Factor-alpha; C496631:HCK protein, human; D051572:Proto-Oncogene Proteins c-hck