Induction of E-selectin expression by double-stranded RNA and TNF-α is attenuated in murine aortic endothelial cells derived from double-stranded RNA-activated kinase (PKR)-null mice

The adherence of leukocytes on the endothelium is mediated in part by the transient expression of the E-selectin adhesion molecule. Because we have previously shown that the dsRNA-activated kinase PKR mediates dsRNA induction of NF-κB, we used murine aortic endothelial (MuAE) cells isolated from wild- type and PKR-null mice to investigate the role of PKR in the induction of E- selectin expression by dsRNA (pIC) and TNF-α. E-selectin mRNA and protein expression was inducible by both pIC and TNF-α in wild-type MuAE cells, whereas induction of E-selectin expression by these agents was defective in PKR-null MuAE cells. Induction of E-selectin promoter activity and NF-κB DNA binding activity were substantially reduced in pIC- or TNF-α-treated PKR- null cells, indicating a role for PKR in both pIC and TNF-α induction of E- selectin via an NF-κB-dependent pathway. In PKR-null cells, pIC-mediated degradation of IκBβ is deficient. Activation of this pathway requires the PKR-dependent degradation of the IκBβ protein. Moreover, both phosphorylated and unphosphorylated activating transcription factor 2 DNA- binding activities were reduced in PKR-null aortic endothelial cells. These results indicate that the PKR is required for full activation of E-selectin expression by pIC and TNF-α in primary mouse aortic endothelial cells identifying activating transcription factor 2 as a new target for PKR- dependent regulation and suggest a role for PKR in leukocyte adhesion.