Abstract
We addressed the regulatory function of mammalian target of rapamycin (mTOR) in the mechanism of thrombin-induced ICAM-1 gene expression in endothelial cells. Pretreatment of HUVECs with rapamycin, an inhibitor of mTOR, augmented thrombin-induced ICAM-1 expression. Inhibition of mTOR by this approach promoted whereas over-expression of mTOR inhibited thrombin-induced transcriptional activity of NF-kappaB, an essential regulator of ICAM-1 transcription. Analysis of the NF-kappaB signaling pathway revealed that inhibition of mTOR potentiated IkappaB kinase activation resulting in a rapid and persistent phosphorylation of IkappaBalpha on Ser32 and Ser36, a requirement for IkappaBalpha degradation. Consistent with these data, we observed a more efficient and stable nuclear localization of RelA/p65 and, subsequently, the DNA binding activity of NF-kappaB by thrombin following mTOR inhibition. These data define a novel role of mTOR in down-regulating thrombin-induced ICAM-1 expression in endothelial cells by controlling a delayed and transient activation of NF-kappaB.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Cell Line
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Cell Nucleus / metabolism
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DNA-Binding Proteins / metabolism
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DNA-Binding Proteins / physiology
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Down-Regulation / drug effects
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Drug Synergism
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Endothelium, Vascular / cytology
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Endothelium, Vascular / drug effects
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Endothelium, Vascular / enzymology*
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Endothelium, Vascular / metabolism
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Enzyme Activation / drug effects
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Humans
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I-kappa B Kinase
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I-kappa B Proteins / metabolism
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Intercellular Adhesion Molecule-1 / biosynthesis*
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Intercellular Adhesion Molecule-1 / metabolism
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NF-KappaB Inhibitor alpha
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NF-kappa B / metabolism*
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NF-kappa B / physiology
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Phosphorylation
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Protein Kinase Inhibitors / pharmacology*
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Protein Kinases / metabolism*
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Protein Kinases / physiology
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Protein Serine-Threonine Kinases / metabolism
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Sirolimus / pharmacology
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TOR Serine-Threonine Kinases
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Thrombin / antagonists & inhibitors
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Thrombin / pharmacology*
Substances
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DNA-Binding Proteins
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I-kappa B Proteins
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NF-kappa B
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NFKBIA protein, human
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Protein Kinase Inhibitors
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Intercellular Adhesion Molecule-1
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NF-KappaB Inhibitor alpha
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Protein Kinases
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MTOR protein, human
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Protein Serine-Threonine Kinases
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TOR Serine-Threonine Kinases
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CHUK protein, human
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I-kappa B Kinase
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IKBKB protein, human
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IKBKE protein, human
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Thrombin
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Sirolimus