Villa P G, Henzel W J, Sensenbrenner M, Henderson C E, Pettmann B
INSERM U.382, Developmental Biology Institute of Marseille, Campus de Luminy, Marseille, France.
J Cell Sci. 1998 Mar;111 ( Pt 6):713-22. doi: 10.1242/jcs.111.6.713.
Apoptosis, or programmed cell death, involves a cascade of regulatory events leading to the activation of specific proteases. However, the key substrates for these proteases remain to be identified. We previously demonstrated that levels of five unidentified polypeptides were specifically increased in neurons from embryonic chicken ciliary ganglia undergoing apoptosis by trophic deprivation. Here we show by microsequencing of two of these polypeptides that they are fragments of actin. One of them represents cleavage of actin at the site of interaction with DNase I. The same actin fragments are also found at early stages of apoptosis in chicken and rat dorsal root ganglion neurons, chicken spinal motoneurons and rat thymocytes. Actin fragmentation may play a role in the apoptotic process, since calpain inhibitors I and II both inhibit neuronal death and suppress actin fragmentation. In contrast, caspase (ICE family) inhibitors, though effective in delaying neuronal death, do not prevent actin cleavage or DNA fragmentation. These results indicate a key role for calpain-like proteases in neuronal programmed cell death and suggest that actin fragmentation in the cell is correlated with subsequent DNA fragmentation.
细胞凋亡，即程序性细胞死亡，涉及一系列导致特定蛋白酶激活的调控事件。然而，这些蛋白酶的关键底物仍有待确定。我们之前证明，在因营养剥夺而发生凋亡的胚胎鸡睫状神经节神经元中，五种未鉴定多肽的水平会特异性升高。在此我们通过对其中两种多肽进行微量测序表明，它们是肌动蛋白的片段。其中一个代表肌动蛋白在与脱氧核糖核酸酶I相互作用位点处的裂解。在鸡和大鼠背根神经节神经元、鸡脊髓运动神经元以及大鼠胸腺细胞凋亡的早期阶段也发现了相同的肌动蛋白片段。肌动蛋白片段化可能在凋亡过程中起作用，因为钙蛋白酶抑制剂I和II都能抑制神经元死亡并抑制肌动蛋白片段化。相比之下，半胱天冬酶（ICE家族）抑制剂虽然能有效延迟神经元死亡，但不能阻止肌动蛋白裂解或DNA片段化。这些结果表明类钙蛋白酶在神经元程序性细胞死亡中起关键作用，并提示细胞中的肌动蛋白片段化与随后的DNA片段化相关。
