Protein kinase C isozyme expression and down-modulation in growing, quiescent, and transformed renal proximal tubule epithelial cells.
Protein kinase C isozyme expression and down-modulation in growing, quiescent, and transformed renal proximal tubule epithelial cells.
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发表时间：
1994-08
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通讯作者：
Liqun Dong;James L. Stevens;Doriano Fabbro;S. Jaken
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作者：
Liqun Dong;James L. Stevens;Doriano Fabbro;S. Jaken
肾α蛋白激酶C （PKC）在肾毒素和肿瘤启动子叶酸的作用下迅速下调（董等，癌症研究，53:4542-4549,1993）。为了进一步探讨PKC同工酶在肾脏生长和癌变中的作用，我们比较了原发性和癌基因改变的大鼠肾近端小管上皮细胞（RPTE）中phbol酯受体和PKC同工酶的含量、分布和调控。免疫印迹分析和RNase保护实验表明，RPTE至少表达了四种PKC同工酶，α、δ、epsilon和zeta。与原代静止RPTE相比，原代增殖、e1a永生化和sv40转化的RPTE中总磷酯受体减少。PDBu结合的减少主要是由于α - pkc蛋白含量特异性下降到静止RPTE水平的约50%。我们比较了退化率和消息水平，以确定α - pkc减少的机制。虽然α - pkc信息水平在静止和增殖的原代RPTE中是相似的，但α - pkc降解在增殖细胞中增加。这些结果表明，α - pkc含量的降低主要是由于周转量的增加。佛波酯刺激了降解速度，从而证明了降解速度和PKC激活之间的联系。这些结果表明，在增殖和癌基因改变的细胞中，基础降解率的增加反映了这些细胞中PKC活性的增加。
Renal alpha-protein kinase C (PKC) is rapidly down-modulated modulated in animals treated with the renal toxin and tumor promoter, folic acid (Dong et al., Cancer Res., 53: 4542-4549, 1993). To further explore the role of PKC isozymes in renal growth and carcinogenesis, we compared phorbol ester receptor and PKC isozyme content, distribution, and regulation in primary and oncogene-altered rat renal proximal tubule epithelial cells (RPTE) in culture. Immunoblot analysis and RNase protection assays indicated that RPTE expressed at least four PKC isozymes, alpha, delta, epsilon, and zeta. Total phorbol ester receptors were decreased in primary proliferating, E1A-immortalized, and SV40-transformed RPTE compared to primary quiescent RPTE. The decrease in PDBu binding was largely due to a specific decrease in alpha-PKC protein content to approximately 50% of the level in quiescent RPTE. Degradation rates and message levels were compared to determine the mechanism for the decrease in alpha-PKC. Whereas alpha-PKC message levels in quiescent and proliferating primary RPTE were comparable, alpha-PKC degradation was increased in proliferating cells. These results indicate that the decreased alpha-PKC content was due largely to increased turnover. Phorbol ester stimulated the rate of degradation, thus demonstrating a link between degradation rate and PKC activation. These results suggest that the increased basal degradation rate in proliferating and oncogene-altered cells reflects an increase in activity of PKC in these cells.