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Bruton's tyrosine kinase regulates TLR7/8-induced TNF transcription via nuclear factor-κB recruitment
Theresa H Page1, Anna M Urbaniak1, Ana I Espirito Santo1
1Kennedy Institute of Rheumatology, NDORMS, University of Oxford, Roosevelt Drive, Oxford, OX3 7FY, United Kingdom.
Abstract:
Tumour necrosis factor (TNF) is produced by primary human macrophages in response to stimulation by exogenous pathogen-associated molecular patterns (PAMPs) and endogenous damage-associated molecular patterns (DAMPs) via Toll-like receptor (TLR) signalling. However, uncontrolled TNF production can be deleterious and hence it is tightly controlled at multiple stages. We have previously shown that Bruton's tyrosine kinase (Btk) regulates TLR4-induced TNF production via p38 MAP Kinase by stabilising TNF messenger RNA. Using both gene over-expression and siRNA-mediated knockdown we have examined the role of Btk in TLR7/8 mediated TNF production. Our data shows that Btk acts in the TLR7/8 pathway and mediates Ser-536 phosphorylation of p65 RelA and subsequent nuclear entry in primary human macrophages. These data show an important role for Btk in TLR7/8 mediated TNF production and reveal distinct differences for Btk in TLR4 versus TLR7/8 signalling.
Insights
Bruton's tyrosine kinase (Btk) plays a key role in regulating tumour necrosis factor (TNF) production. This study reveals Btk's distinct functions in Toll-like receptor (TLR) 4 versus TLR7/8 signalling pathways in human macrophages.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Tumour necrosis factor (TNF) is crucial in immune responses but requires tight regulation to prevent deleterious effects.
- Toll-like receptors (TLRs) mediate responses to pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs).
- Bruton's tyrosine kinase (Btk) was previously implicated in regulating TNF production via TLR4 signalling.
Purpose of the Study:
- To investigate the role of Bruton's tyrosine kinase (Btk) in Toll-like receptor 7/8 (TLR7/8) mediated tumour necrosis factor (TNF) production.
- To elucidate the specific molecular mechanisms by which Btk influences TLR7/8 signalling in primary human macrophages.
- To compare the function of Btk in TLR4 versus TLR7/8 signalling pathways.
Main Methods:
- Gene over-expression and siRNA-mediated knockdown of Btk in primary human macrophages.
- Stimulation of macrophages with TLR7/8 agonists.
- Analysis of p65 RelA phosphorylation at Ser-536 and its nuclear translocation.
Main Results:
- Bruton's tyrosine kinase (Btk) is shown to be active in the TLR7/8 signalling pathway.
- Btk mediates the phosphorylation of p65 RelA at Ser-536, promoting its nuclear entry.
- Distinct roles for Btk in TLR4-induced versus TLR7/8-induced TNF production were identified.
Conclusions:
- Bruton's tyrosine kinase (Btk) plays a significant role in regulating TNF production through TLR7/8 signalling in human macrophages.
- Btk's involvement in TLR7/8 signalling differs from its previously established role in TLR4 signalling.
- These findings highlight the complex and pathway-specific functions of Btk in innate immune responses.