TRIF-mediated TLR3 and TLR4 signaling is negatively regulated by ADAM15

Area of Science:

• Immunology
• Molecular Biology
• Cell Signaling

Background:

• Toll-like receptors (TLRs) are crucial for innate immunity against pathogens.
• Toll/IL-1R domain-containing adaptor inducing IFN (TRIF) is a key adaptor for TLR3 and TLR4 signaling.
• Regulation of TRIF-dependent signaling pathways remains incompletely understood.

Purpose of the Study:

• To identify novel regulators of TRIF-mediated Toll-like receptor signaling.
• To characterize the functional role of identified TRIF-interacting partners.
• To elucidate the mechanism by which ADAM15 modulates TLR signaling.

Main Methods:

• Immunoprecipitation of the TRIF signaling complex followed by liquid chromatography-mass spectrometry for protein identification.
• Stimulation of cells with TLR3 or TLR4 ligands.
• Reporter gene assays to assess NF-κB and IFN-β activity.
• Analysis of cytokine production upon suppression of ADAM15 expression.
• Investigation of ADAM15's role in TRIF proteolytic cleavage.

Main Results:

• A disintegrin and metalloprotease (ADAM)15 was identified as a novel TRIF-interacting partner.
• ADAM15 functions as a negative regulator of TRIF-mediated NF-κB and IFN-β activation.
• Suppression of ADAM15 enhances pro-inflammatory cytokine production induced by TLR ligands and viral infections.
• ADAM15 directly mediates the proteolytic cleavage of TRIF.

Conclusions:

• ADAM15 plays an unexpected, anti-inflammatory role in TLR signaling by impairing TRIF-dependent pathways.
• ADAM15 limits excessive pro-inflammatory cytokine and matrix metalloproteinase production.
• This study reveals ADAM15 as a novel negative regulator of TLR3 and TLR4 signaling.