Protein Kinase C-delta (PKC{delta}) Regulates Pro-inflammatory Chemokine Expression through Cytosolic Interaction with the NF-{kappa}B Subunit p65 in Vascular Smooth Muscle Cells [Signal Transduction]

February 11th, 2014 by Ren, J., Wang, Q., Morgan, S., Si, Y., Ravichander, A., Dou, C., Kent, K. C., Liu, B.

Pro-inflammatory chemokines released by vascular smooth muscle cells (VSMCs) play a critical role in vascular inflammation. Protein kinase C-delta (PKCδ) has been shown to be upregulated in VSMCs of injured arteries. PKCδ-/- mice are resistant to inflammation as well as apoptosis in models of abdominal aortic aneurysm. However, the precise mechanism by which PKCδ modulates inflammation remains incompletely understood. In this study, we identified 4 inflammatory chemokines (MCP-1/CCL2, CCL7, CXCL16 and CX3CL1) over 45 PKCδ-regulated genes associated with inflammatory response by microarray analysis. Using MCP-1 as a prototype, we demonstrated that PKCδ stimulated chemokine expression at the transcriptional level. Inhibition of NF-κB pathway or siRNA knockdown of subunit p65, but not p50, eliminated PKCδ′s effect on MCP-1 expression. Overexpressing PKCδ followed by incubation with PMA resulted in an increase in p65 Ser536 phosphorylation and enhanced DNA-binding affinity without affecting IκB degradation or p65 nuclear translocation. PKCδ gene deficiency impaired p65 Ser536 phosphorylation and DNA-binding affinity in response to TNFα. Results from in situ proximity ligation analysis and co-immunoprecipitation performed on cultured VSMCs and aneurysmal aorta demonstrated physical interaction between PKCδ and p65, which took place largely outside the nucleus. Promoting nuclear translocation of PKCδ with peptide ψδRACK diminished MCP-1 production, whereas inhibition of PKCδ translocation with peptide δV1-1 enhanced MCP-1 expression. Together, these results suggest that PKCδ modulates inflammation at least in part through the NF-κB-mediated chemokines. Mechanistically, PKCδ activates NF-κB through an IκB-independent cytosolic interaction, which subsequently leads to enhanced p65 phosphorylation and DNA-binding affinity.
  • Posted in Journal of Biological Chemistry, Publications
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