IDENTIFICATION OF SIGNAL-INDUCED I-KAPPA-B-ALPHA KINASES IN HUMAN ENDOTHELIAL-CELLS

Activation of the nuclear transcription factor-kappa B is an early eve nt in endothelial activation. NF-kappa B activation is regulated by th e inducible phosphorylation and subsequent degradation of the inhibito ry subunit I kappa B-alpha. We identified two discrete kinases of appr oximately 36 and 41 kDa in the cytoplasm of human umbilical vein endot helial cells that specifically bind to and phosphorylate the I kappa B -alpha subunit. I kappa B-alpha kinase activity is transiently elevate d following treatment with either tumor necrosis factor alpha, interle ukin-1 beta, or bacterial lipopolysaccharides and precedes activation of either mitogen-activated kinase or Jun kinase. Furthermore, activat ion of the I kappa B-alpha kinases precedes both the appearance of hyp erphosphorylated I kappa B-alpha and its subsequent degradation, as we ll as the translocation of NF-kappa B to the nucleus, Deletion mutagen esis of the I kappa B-alpha polypeptide revealed that these kinases bi nd in or around the ankyrin repeat domains and phosphorylate residues within the C terminus. These kinases, however, were not identical to c asein kinase II and displayed a pharmacologic profile distinct from ot her known kinases. These kinases may represent components of a signal transduction pathway regulating I kappa B-alpha levels in vascular end othelium.