Jänicke R U, Sprengart M L, Wati M R, Porter A G
Institute of Molecular and Cell Biology, The National University of Singapore, 30 Medical Drive, Singapore 117609, Republic of Singapore.
J Biol Chem. 1998 Apr 17;273(16):9357-60. doi: 10.1074/jbc.273.16.9357.
Interleukin 1beta-converting enzyme-like proteases (caspases) are crucial components of cell death pathways. Among the caspases identified, caspase-3 stands out because it is commonly activated by numerous death signals and cleaves a variety of important cellular proteins. Studies in caspase-3 knock-out mice have shown that this protease is essential for brain development. To investigate the requirement for caspase-3 in apoptosis, we took advantage of the MCF-7 breast carcinoma cell line, which we show here has lost caspase-3 owing to a 47-base pair deletion within exon 3 of the CASP-3 gene. This deletion results in the skipping of exon 3 during pre-mRNA splicing, thereby abrogating translation of the CASP-3 mRNA. Although MCF-7 cells were still sensitive to tumor necrosis factor (TNF)- or staurosporine-induced apoptosis, no DNA fragmentation was observed. In addition, MCF-7 cells undergoing cell death did not display some of the distinct morphological features typical of apoptotic cells such as shrinkage and blebbing. Introduction of the CASP-3 gene into MCF-7 cells resulted in DNA fragmentation and cellular blebbing following TNF treatment. These results indicate that although caspase-3 is not essential for TNF- or staurosporine-induced apoptosis, it is required for DNA fragmentation and some of the typical morphological changes of cells undergoing apoptosis.
白细胞介素1β转换酶样蛋白酶（半胱天冬酶）是细胞死亡途径的关键组成部分。在已鉴定的半胱天冬酶中，半胱天冬酶-3尤为突出，因为它通常被多种死亡信号激活，并能切割多种重要的细胞蛋白。对半胱天冬酶-3基因敲除小鼠的研究表明，这种蛋白酶对大脑发育至关重要。为了研究半胱天冬酶-3在细胞凋亡中的作用，我们利用了MCF-7乳腺癌细胞系，我们在此表明该细胞系由于CASP-3基因外显子3内47个碱基对的缺失而失去了半胱天冬酶-3。这种缺失导致前体mRNA剪接过程中外显子3的跳跃，从而废除了CASP-3 mRNA的翻译。尽管MCF-7细胞对肿瘤坏死因子（TNF）或星形孢菌素诱导的细胞凋亡仍敏感，但未观察到DNA片段化。此外，正在经历细胞死亡的MCF-7细胞未表现出凋亡细胞典型的一些明显形态特征，如细胞皱缩和出泡。将CASP-3基因导入MCF-7细胞后，TNF处理会导致DNA片段化和细胞出泡。这些结果表明，尽管半胱天冬酶-3对TNF或星形孢菌素诱导的细胞凋亡不是必需的，但它是DNA片段化和细胞凋亡过程中一些典型形态变化所必需的。
