Ito Yoshimasa, Oh-Hashi Kentaro, Kiuchi Kazutoshi, Hirata Yoko
Department of Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Japan.
Brain Res. 2006 Jul 12;1099(1):1-7. doi: 10.1016/j.brainres.2006.03.126. Epub 2006 Jun 19.
Caspase-3 (32 kDa) is one of the primary protease executioners of apoptosis and is activated by intra-chain proteolytic cleavage, which generates a large subunit (17 kDa) and a small subunit (12 kDa). Typically, after apoptotic stimuli, the level of cleaved caspase-3 increases while that of caspase-3 decreases. It has been shown that caspase-3 mRNA levels increase in cortex following traumatic brain injury or focal ischemia. In the present study, we demonstrate that both caspase-3 mRNA and protein increase in apoptotic PC12 cells following exposure to manganese which strongly induces caspase-3 cleavage. Up-regulation of caspase-3 protein was evident in manganese-treated PC12 cells and was moderate in cisplatin-, rotenone- and A23187-treated cells but was not observed in serum deprivation-, anisomycin-, camptothecin-, cycloheximide- or staurosporine-treated cells in which all treatments induced extensive DNA fragmentation. Manganese-induced up-regulation of caspase-3 mRNA was partially attenuated by the pretreatment with the MEK inhibitor U0126, but not with the c-Jun N-terminal kinase (JNK) inhibitor SP600125. In contrast, the increase in caspase-3 protein was suppressed by both U0126 and SP600125. These results suggest that p44/42 MAPK contributes to the up-regulation of caspase-3 mRNA and the JNK pathway regulates caspase-3 protein levels posttranslationally in manganese-induced apoptosis in PC12 cells.
半胱天冬酶 -3（32 kDa）是细胞凋亡的主要蛋白酶执行者之一，通过链内蛋白水解切割被激活，产生一个大亚基（17 kDa）和一个小亚基（12 kDa）。通常，在凋亡刺激后，切割后的半胱天冬酶 -3水平升高，而半胱天冬酶 -3水平降低。研究表明，创伤性脑损伤或局灶性缺血后，皮质中的半胱天冬酶 -3 mRNA水平会升高。在本研究中，我们证明，暴露于锰后，凋亡的PC12细胞中的半胱天冬酶 -3 mRNA和蛋白质均增加，锰强烈诱导半胱天冬酶 -3的切割。在锰处理的PC12细胞中，半胱天冬酶 -3蛋白的上调很明显，在顺铂、鱼藤酮和A23187处理的细胞中上调程度中等，但在血清剥夺、茴香霉素、喜树碱、环己酰亚胺或星形孢菌素处理的细胞中未观察到上调，所有这些处理均诱导广泛的DNA片段化。用MEK抑制剂U0126预处理可部分减弱锰诱导的半胱天冬酶 -3 mRNA上调，但用c-Jun N末端激酶（JNK）抑制剂SP600125预处理则不能。相反，U0126和SP600125均抑制了半胱天冬酶 -3蛋白的增加。这些结果表明，p44/42丝裂原活化蛋白激酶（MAPK）有助于半胱天冬酶 -3 mRNA的上调，而JNK途径在PC12细胞锰诱导的凋亡过程中对翻译后半胱天冬酶 -3蛋白水平起调节作用。
