Tsutusmi A, Shiota G, Yamazaki H, Kunisada T, Terada T, Kawasaki H
Second Department of Internal Medicine, Faculty of Medicine, Tottori University, Yonago 683-8504, Japan.
Biochem Biophys Res Commun. 2000 Nov 11;278(1):229-35. doi: 10.1006/bbrc.2000.3786.
Retinoids play an important role in pathogenesis of liver diseases. To clarify the functional role of retinoic acid (RA) in liver, we developed transgenic mice (Tg) which express the dominant negative form of retinoic acid receptor (RARE) in liver. Here, we report that proliferation of hepatocytes in RARE Tg is greatly enhanced and that cyclin E is up-regulated in RARE Tg. Liver weight, liver/body weight, and proliferating cell nuclear antigen (PCNA) labeling index in RARE Tg were significantly increased, compared to those in wild-type mice (P < 0.01, each). Cell cycle analysis showed that 2N DNA content cells and aneuploid area between 2N and 4N DNA, reflecting S phase cells, were significantly increased in RARE Tg, compared to wild-type mice (P < 0.01, each). Of G1 phase-related proteins including cyclins, cyclin-dependent protein kinases (CDKs) and cyclin-dependent protein kinase inhibitors (CKIs), cyclin E mRNA and protein was up-regulated in liver from RARE Tg by reverse transcription polymerase chain reaction and Western blot analysis. Furthermore, the immunoprecipitation with anti-cdk2 antibody, followed by Western blot analysis with anti-cyclin E antibody indicated that cyclin E/cdk2 complex is increased in liver of RARE Tg. The results of the present study suggest that cyclin E in association with cdk2 governs cell cycle progression through G1 in hepatocytes where function of RA is inhibited.
维甲酸在肝脏疾病的发病机制中发挥着重要作用。为了阐明视黄酸（RA）在肝脏中的功能作用，我们构建了在肝脏中表达视黄酸受体（RARE）显性负性形式的转基因小鼠（Tg）。在此，我们报告RARE Tg小鼠的肝细胞增殖显著增强，且细胞周期蛋白E在RARE Tg小鼠中上调。与野生型小鼠相比，RARE Tg小鼠的肝脏重量、肝重/体重以及增殖细胞核抗原（PCNA）标记指数均显著增加（每组P < 0.01）。细胞周期分析显示，与野生型小鼠相比，RARE Tg小鼠中反映S期细胞的2N DNA含量细胞以及2N和4N DNA之间的非整倍体区域显著增加（每组P < 0.01）。在包括细胞周期蛋白、细胞周期蛋白依赖性蛋白激酶（CDK）和细胞周期蛋白依赖性蛋白激酶抑制剂（CKI）在内的G1期相关蛋白中，通过逆转录聚合酶链反应和蛋白质印迹分析发现，RARE Tg小鼠肝脏中的细胞周期蛋白E mRNA和蛋白上调。此外，用抗cdk2抗体进行免疫沉淀，随后用抗细胞周期蛋白E抗体进行蛋白质印迹分析表明，RARE Tg小鼠肝脏中细胞周期蛋白E/cdk2复合物增加。本研究结果表明，在视黄酸功能受到抑制的肝细胞中，细胞周期蛋白E与cdk2共同调控细胞通过G1期的进程。
