Functional Involvement of TANK-Binding Kinase 1 in the MyD88-Dependent NF-B Pathway Through Syk.

Inflammation is a vital immune defense mechanism regulated by Toll-like receptors (TLRs) and the nuclear factor-kappa B (NF-B) pathway. TANK-binding kinase 1 (TBK1) is central to immunity and inflammation and influences antiviral responses and cellular processes. However, the precise role of TBK1 in modulating the NF-B pathway through interactions with other proteins, such as spleen tyrosine kinase (Syk), remains poorly understood. As dysregulation of TBK1 and NF-B can lead to a variety of diseases, they are important therapeutic targets. In this work, inflammatory processes involving the TBK1-Syk-NF-B pathway were elucidated using lipopolysaccharide (LPS)-induced macrophages; human embryonic kidney 293 (HEK293) cells overexpressing MyD88, TBK1, and Syk proteins and their mutants; and real-time polymerase chain reaction (PCR), immunoblotting analyses, and kinase assays. TBK1 was activated in LPS-, poly I:C-, and Pam3CSK-stimulated macrophages. Transcript levels of , , and were increased in cells overexpressing TBK1 but not in cells overexpressing TBK1 K38A. The transcription of , , and and NF-B luciferase activity were inhibited by silencing TBK1 in LPS-stimulated RAW264.7 cells and MyD88-transfected HEK293 cells. Syk was the key mediator of the TBK1-dependent NF-B pathway and bound directly to the coiled coil domain of TBK1, which was necessary to activate Syk and the Syk-p85 pathway. This research advances the understanding of the role of TBK1 in NF-B signaling, emphasizing Syk as a key mediator. The interaction between TBK1 and Syk has potential for precise immune modulation that can be applied to treat immune-related disorders.