Cheng S C, Luo D, Xie Y
Department of Biology, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, SAR China.
Cell Biol Int. 2001;25(3):261-5. doi: 10.1006/cbir.2000.0619.
Bcl-2 family proteins play a critical role in the regulation of apoptosis. Treatment of a human hepatocellular carcinoma cell line, QGY-7703, with Taxol induced apoptosis and Bcl-2 protein phosphorylation. Microscopic observation indicated that apoptotic bodies (0-15%) of Taxol-treated QGY cells appeared after 12 h of treatment, and apoptotic QGY cells gradually increased to 40% after 24 h and 70% after 48 h. A DNA fragmentation assay showed that Taxol induced genomic DNA cleavage into 200 bp DNA fragments. Bcl-2 protein was phosphorylated in Taxol-treated QGY cells within 3 h of treatment, and continued gradually up to 24 h. By 48 h, the protein was unphosphorylated. Other Bcl-2 family proteins, including Bax (a heterodimerization partner of Bcl-2), Bcl-XL, Bak and Bad, were expressed, but at constant levels. The results show a close correlation between Bcl-2 phosphorylation and apoptosis in QGY cells. The inactivation of Bcl-2 protein phosphorylation could be one of the key mechanisms needed for the induction of apoptosis in Taxol-treated QGY cells.
Bcl-2家族蛋白在细胞凋亡调控中发挥关键作用。用紫杉醇处理人肝癌细胞系QGY-7703可诱导细胞凋亡和Bcl-2蛋白磷酸化。显微镜观察表明，紫杉醇处理的QGY细胞在处理12小时后出现凋亡小体（0 - 15%），24小时后凋亡的QGY细胞逐渐增加到40%，48小时后增加到70%。DNA片段化分析表明，紫杉醇诱导基因组DNA裂解为200 bp的DNA片段。在紫杉醇处理的QGY细胞中，Bcl-2蛋白在处理3小时内发生磷酸化，并持续逐渐增加直至24小时。到48小时时，该蛋白去磷酸化。其他Bcl-2家族蛋白，包括Bax（Bcl-2的异二聚化伙伴）、Bcl-XL、Bak和Bad均有表达，但水平恒定。结果表明QGY细胞中Bcl-2磷酸化与细胞凋亡密切相关。Bcl-2蛋白磷酸化失活可能是紫杉醇处理的QGY细胞诱导凋亡所需的关键机制之一。
