Regulation of RelA/p65 and Endothelial Cell Inflammation by Proline-Rich Tyrosine Kinase 2.

Department of Pediatrics (Neonatology), Lung Biology and Disease Program, University of Rochester School of Medicine and Dentistry, Rochester, New York, United States.
American Journal of Respiratory Cell and Molecular Biology (Impact Factor: 4.11). 07/2012; DOI: 10.1165/rcmb.2012-0047OC
Source: PubMed

ABSTRACT We investigated the role of proline-rich tyrosine kinase 2 (Pyk2) in the mechanism of NF-κB activation and endothelial cell (EC) inflammation induced by thrombin, a procoagulant serine protease released in high amounts during sepsis and other inflammatory conditions. Stimulation of EC with thrombin resulted in a time-dependent activation of Pyk2. RNAi knockdown of Pyk2 attenuated thrombin-induced activity of NF-κB and expression of its target genes, vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemoattractant protein-1 (MCP-1). Depletion of Pyk2 also inhibited NF-κB activity induced by TNFα, suggesting that Pyk2 is a general regulator of NF-κB. Pyk2 knockdown impaired thrombin-induced activation of IKK and phosphorylation (Ser32 and Ser36) of IκBα, but surprisingly failed to prevent IκBα degradation. However, depletion of IKKα or IKKβ was effective in inhibiting IκBα phosphorylation/degradation, as expected. Intriguingly, Pyk2 knockdown impaired nuclear translocation and DNA binding of RelA/p65 despite the inability to prevent IκBα degradation. Additionally, Pyk2 knockdown was associated with inhibition of RelA/p65 phosphorylation at Ser536, which is important for transcriptional activity of RelA/p65. Depletion of IKKα or IKKβ, each impaired RelA/p65 phosphorylation. Taken together, these data identify Pyk2 as a critical regulator of EC inflammation by virtue of engaging IKK to promote the release and the transcriptional capacity of RelA/p65, and additionally, by its ability to facilitate the nuclear translocation of the released RelA/p65. Thus, specific targeting of Pyk2 may be an effective anti-inflammatory strategy in vascular diseases associated with EC inflammation and intravascular coagulation.

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