Kosaka C, Sasaguri T, Masuda J, Zen K, Shimokado K, Yokota T, Ogata J
National Cardiovascular Center Research Institute, Osaka, Japan.
Biochem Biophys Res Commun. 1993 Jun 30;193(3):991-8. doi: 10.1006/bbrc.1993.1723.
Proliferation of cultured human vascular endothelial cells may be negatively regulated by the protein kinase C (PKC) pathway, because phorbol 12-myristate, 13-acetate (PMA) inhibits DNA synthesis and cell population doubling in PKC-retaining cells, but not in cells depleted of PKC by a long-term exposure to PMA. We investigated the mechanism through which PKC arrests the cell cycle with regard to cyclin A, which has been reported to play a key role in G1/S progression activating CDK2. Cyclin A mRNA was elevated from late G1 in accordance with the protein expression, which reached the maximal level during the S phase. PMA added at late G1 potently reduced the levels of cyclin A mRNA and the protein in concentration-dependent manners parallel to its effect on the proliferation. However, it failed to inhibit the expression in PKC-depleted cells. The mRNA reduction by PMA was due to inhibition of the transcription. The PMA effects were mimicked by multiple doses of 1,2-dioctanoylglycerol. These findings suggest that PKC inhibits G1/S progression through suppression of cyclin A gene transcription in endothelial cells.
培养的人血管内皮细胞的增殖可能受到蛋白激酶C（PKC）途径的负调控，因为佛波醇12 - 肉豆蔻酸酯13 - 乙酸酯（PMA）抑制PKC保留细胞中的DNA合成和细胞群体倍增，但在长期暴露于PMA而耗尽PKC的细胞中则不然。我们研究了PKC使细胞周期停滞的机制，该机制与细胞周期蛋白A有关，据报道细胞周期蛋白A在激活CDK2的G1/S进程中起关键作用。细胞周期蛋白A mRNA从G1晚期开始升高，与蛋白表达一致，在S期达到最高水平。在G1晚期添加的PMA以浓度依赖的方式有效降低细胞周期蛋白A mRNA和蛋白的水平，这与其对增殖的影响平行。然而，它未能抑制PKC耗尽细胞中的表达。PMA导致的mRNA减少是由于转录受到抑制。PMA的作用可被多剂量的1,2 - 二辛酰甘油模拟。这些发现表明，PKC通过抑制内皮细胞中细胞周期蛋白A基因的转录来抑制G1/S进程。
