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Thrombin activates transcriptional factors NF‐kappaB and NFAT to induce optimal ICAM‐1 expression in endothelial cells.
Author(s) -
Xue Jiaping,
Bair Angela,
Christman John W,
Malik Asrar B,
Tiruppathi Chinnaswamy
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.782.32
Subject(s) - nfat , thrombin , microbiology and biotechnology , reporter gene , gene knockdown , transfection , icam 1 , transcription factor , transactivation , chromatin immunoprecipitation , enhancer , biology , gene expression , promoter , chemistry , gene , intracellular , biochemistry , immunology , platelet
Thrombin‐induced increase in intracellular Ca2+ activates transcription factors NF‐?B and NFAT in endothelial cells (ECs). We investigated the possible role of NF‐?B and NFAT in the signaling mechanism of thrombin‐induced ICAM‐1 expression in ECs. We identified the presence of two NF‐?B binding sites in the intron‐1 (+ 70, NF‐?B site 1; +611, NF‐?B site 2) of human ICAM‐1 gene. We observed the binding of both RelA and NFATc1 to the intronic NF‐?B site 1 of ICAM‐1 gene in thrombin‐stimulated ECs by chromatin immunoprecipitation. To delineate the role of intronic NF‐?B site 1 in the ICAM‐1 gene, we transiently transfected ECs with ICAM‐1‐promoter‐intronic NF‐?B site 1 reporter construct. Thrombin increased the reporter expression several‐fold. Exposure of transfected cells to calcineurin inhibitor FK506 markedly reduced thrombin‐induced reporter expression. Introduction of mutation in the intronic NF‐?B site 1 significantly reduced thrombin‐induced reporter expression. Knockdown of either RelA or NFATc1 with siRNA inhibited ~80% of thrombin‐induced ICAM‐1 expression; however, NFATc1 knockdown with siRNA had no effect on TNF‐a‐induced ICAM‐1 expression in ECs. These findings suggest that both RelA and NFATc1 bind to the intronic enhancer elements in the ICAM‐1 gene and signal the transcription of ICAM‐1 gene in response to thrombin in endothelial cells.