Rac1-dependent transcriptional up-regulation of p27(Kip1) by homophilic cell-cell contact in vascular endothelial cells

摘要

The mechanism for the transcriptional up-regulation of p27(Kip1) due to the formation of the cell-cell contact was investigated in vascular endothelial cells. The induction of the cell-cell contact by adding an extra number of endothelial cells activated Rac1, up-regulated p27(Kip1) mRNA and protein, and also facilitated the cell cycle arrest. Transduction of the Rac1 inhibitor protein using the cell-penetrating peptide or treatment with a Rac1 inhibitor NSC23766 inhibited the p27(Kip1) up-regulation and delayed the cell cycle arrest. Rac1 was therefore suggested to mediate the contact-induced transcriptional up-regulation of p27(Kip1). The role of Rac1 in the regulation of the p27(Kip1) promoter activity was next examined with a luciferase reporter assay. The promoter activity was increased by inducing the cell-cell contact, which was significantly inhibited by the Rac1 inhibitory protein and NSC23766. The evaluation of various truncated promoter regions determined region -620 to -573 nucleotides from the initiation codon to be responsible for the contact-induced, Rac1-dependent activation of the p27(Kip1) promoter. The present study thus demonstrated for the first time that the activation of Rac1 due to the cell-cell contact plays a critical role in the transcriptional up-regulation of P27(Kip1) in vascular endothelial cells. (C) 2007 Elsevier B.V. All fights reserved.