Inhibition of SRC Tyrosine Kinases Suppresses Activation of Nuclear Factor-κB, and Serine and Tyrosine Phosphorylation of IκB-α in Lipopolysaccharide-Stimulated Raw 264.7 Macrophages

Abstract

Involvement of protein tyrosine kinases (PTK) in lipopolysaccharide (LPS)-induced nuclear factor-kappa B (NF-κB) activation has been demonstrated. Studies investigated the role of PTK and the underlying mechanisms by which PTK play a role in LPS induction of pathways leading to NF-κB activation in macrophages. Inhibitors of PTK—genistein, herbimycin A, or AG126—blocked LPS-induced NF-κB activation. Genistein also blocked pervanadate-induced NF-κB activation. Furthermore, Src TK selective inhibitors—damnacanthal or PP1—blocked LPS-induced NF-κB activation over a range of nanomolar concentrations. Genistein, damnacanthal, or PP1 blocked the LPS-induced serine phosphorylation, the degradation of IκB-α, and the consequent translocation of the p65 subunit of NF-κB to the nucleus. In addition to serine phosphorylation of IκB-α, LPS-induced NF-κB activation also required tyrosine phosphorylation of IκB-α. These TK inhibitors blocked substantially LPS induction of tyrosine phosphorylation of IκB-α. Furthermore, cSrc and Lck were physically associated with IκB-α. These results suggest that the LPS-induced NF-κB pathways are dependent on both serine and tyrosine phosphorylation of IκB-α, and that Src TK, such as cSrc and Lck, are key components of the LPS signaling pathway through at least two different mechanisms associated with NF-κB activation.

This work was supported by grant R04-2002-000-00023-0 from the Basic Research Program of the Korea Science and Engineering Foundation.

Notes

This work was supported by grant R04-2002-000-00023-0 from the Basic Research Program of the Korea Science and Engineering Foundation.