Tyrosine Phosphorylation of I-κB Kinase α/β by Protein Kinase C-Dependent c-Src Activation Is Involved in TNF-α-Induced Cyclooxygenase-2 Expression

Abstract

The signaling pathway involved in TNF-α-induced cyclooxygenase-2 (COX-2) expression was further studied in human NCI-H292 epithelial cells. A protein kinase C (PKC) inhibitor (staurosporine), tyrosine kinase inhibitors (genistein and herbimycin A), or a Src kinase inhibitor (PP2) attenuated TNF-α- or 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced COX-2 promoter activity. TNF-α- or TPA-induced I-κB kinase (IKK) activation was also blocked by these inhibitors, which reversed I-κBα degradation. Activation of c-Src and Lyn kinases, two Src family members, was inhibited by the PKC, tyrosine kinase, or Src kinase inhibitors. The dominant-negative c-Src (KM) mutant inhibited induction of COX-2 promoter activity by TNF-α or TPA. Overexpression of the constitutively active PKCα (PKCα A/E) or wild-type c-Src plasmids induced COX-2 promoter activity, and these effects were inhibited by the dominant-negative c-Src (KM), NF-κB-inducing kinase (NIK) (KA), or IKKβ (KM) mutant. The dominant-negative PKCα (K/R) or c-Src (KM) mutant failed to block induction of COX-2 promoter activity caused by wild-type NIK overexpression. In coimmunoprecipitation experiments, IKKα/β was found to be associated with c-Src and to be phosphorylated on its tyrosine residues after TNF-α or TPA treatment. Two tyrosine residues, Tyr188 and Tyr199, near the activation loop of IKKβ, were identified to be crucial for NF-κB activation. Substitution of these residues with phenylalanines attenuated COX-2 promoter activity and c-Src-dependent phosphorylation of IKKβ induced by TNF-α or TPA. These data suggest that, in addition to activating NIK, TNF-α also activates PKC-dependent c-Src. These two pathways cross-link between c-Src and NIK and converge at IKKα/β, and go on to activate NF-κB, via serine phosphorylation and degradation of IκB-α, and, finally, to initiate COX-2 expression.

IL‐12, IL‐23, and IL‐27 enhance human β‐defensin‐2 production in human keratinocytes

“…In these cells, JAK2 is involved in the activation of NF-jB; JAK2 may activate IKK via the downstream pathways PI3K/Akt [24,25] and/or PKC/c-src [26]. The IL-12-and IL-23-activated JAK2 are phosphorylated at multiple tyrosine residues, and these serve as docking sites for other signal-transducing proteins containing src homology 2 (SH2) domains [18].…”

TNF Activates Syk Protein Tyrosine Kinase Leading to TNF-Induced MAPK Activation, NF-κB Activation, and Apoptosis

“…Proline-rich tyrosine kinase (Pyk2) 3 (18,19) and p53/Lyn p56 (20) have roles in TNF-induced neutrophil activation; Etk/Bmx in TNF-induced endothelial cell migration and angiogenesis; c-Src in TNF-induced NF-B activation in the marrow macrophages (21,22); and TNF in regulation of gap junctions in airway epithelial cells (23). Pyk2 has also been implicated in TNF-induced JNK activation (24).…”

Activation of the NF-κB pathway by the leukemogenic TEL-Jak2 and TEL-Abl fusion proteins leads to the accumulation of antiapoptotic IAP proteins and involves IKKα

“…Involvement of members of the src kinase family required for in vivo Bcr-Abl leukemogenic properties (Hu et al, 2004), and known to stimulate NIK activity and to phosphorylate IKK directly (Huang et al, 2003) has also been reported. The present and previous studies (Constantino Rosa Santos et al, 2001) agree that the TEL-Abl oncogene, as well as Bcr-Abl, activates NF-kB but in a manner that presumably involves IKKa and do not strongly affect the p65/RelA nuclear translocation process (Figure 2a).…”