Activation of Syk by protein kinase C-delta regulates thrombin-induced intercellular adhesion molecule-1 expression in endothelial cells via tyrosine phosphorylation of RelA/p65.
Protein kinase C-delta (PKC-delta) plays a pivotal role in mediating thrombin-induced NF-kappaB activation and ICAM-1 expression in endothelial cells. However, the downstream mechanisms mediating its function are unclear. In this study, we show that PKC-delta-mediated activation of protein-tyrosine kinase Syk plays an important role in thrombin signaling of NF-kappaB activation and intercellular adhesion molecule-1 (ICAM-1) expression in endothelial cells. Stimulation of human vascular endothelial cells with thrombin resulted in a time-dependent phosphorylation of Syk on tyrosine 525 and 526, an indication of Syk activation. Inhibition of PKC-delta by pharmacological and genetic approaches prevented Syk activation by thrombin. These results place Syk downstream of PKC-delta in transmitting thrombin-activated signaling in endothelial cells. Consistent with this, thrombin-induced NF-kappaB activity and ICAM-1 expression were prevented by the expression of a kinase-defective mutant or RNA interference knockdown of Syk. Similarly, inhibiting Syk also impaired NF-kappaB activity and ICAM-1 expression induced by a constitutively active mutant of PKC-delta. Analysis of the NF-kappaB pathway showed that Syk contributes to thrombin-induced NF-kappaB activation by controlling its transactivation potential and that this response is associated with tyrosine phosphorylation of RelA/p65. Thus, these data unveil a novel pathway in which Syk signals downstream of PKC-delta to mediate thrombin induced ICAM-1 expression in endothelial cells by increasing transcriptional capacity of NF-kappaB via a mechanism that relies on tyrosine phosphorylation of RelA/p65.
Bijli
Kaiser M
KM
Department of Pediatrics (Neonatology), Lung Biology and Disease Program, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA.
Fazal
Fabeha
F
Minhajuddin
Mohd
M
Rahman
Arshad
A
D021581:Active Transport, Cell Nucleus; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism*; D004789:Enzyme Activation; D005786:Gene Expression Regulation; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D019000:Phosphotyrosine / Q000378:metabolism*; D011485:Protein Binding; D051745:Protein Kinase C-delta / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D000072377:Syk Kinase; D013917:Thrombin / Q000378:metabolism*; D051996:Transcription Factor RelA / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation / Q000235:genetics
D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B; C498143:RELA protein, human; D051996:Transcription Factor RelA; D018799:Intercellular Adhesion Molecule-1; D019000:Phosphotyrosine; D004247:DNA; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; D051550:I-kappa B Kinase; D051745:Protein Kinase C-delta; D013917:Thrombin