TDP-43-induced Death Is Associated with Altered Regulation of BIM and Bcl-xL and Attenuated by Caspase-mediated TDP-43 Cleavage
TDP-43-induced Death Is Associated with Altered Regulation of BIM and Bcl-xL and Attenuated by Caspase-mediated TDP-43 Cleavage
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DOI：
10.1074/jbc.m110.197483
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发表时间：
2011-04-15
影响因子：
4.8
通讯作者：
Matsuoka, Masaaki
中科院分区：
文献类型：
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作者：
Suzuki, Hiroaki;Lee, Kikyo;Matsuoka, Masaaki
在肌萎缩侧索硬化症（ALS）和额颞叶变性伴泛素化包涵体（FTLD-U）的大多数病例中，反式反应DNA结合蛋白-43（TDP-43）及其过度磷酸化和N-末端截短的C-末端片段（CTF）的异常聚集体作为泛素化包涵体的主要成分沉积。TDP-43对这些神经退行性疾病发病机制的作用机制仍不清楚。在这项研究中，我们发现TDP-43表达在内源性水平上增加2-5倍诱导NSC 34运动神经元细胞和原代皮层神经元死亡。TDP-43诱导的死亡与Bim表达的上调和Bcl-xL表达的下调有关。siRNA介导的Bim表达减少减弱TDP-43诱导的死亡。累积的证据表明，半胱天冬酶在ALS和FTLD-U患者的神经元中被激活，并且激活的半胱天冬酶介导的TDP-43的切割产生TDP-43的CTF。在此，我们进一步发现ER（内质网）应激或星形孢菌素介导的半胱天冬酶活化导致TDP-43在Asp（89）和Asp（169）处裂解，在培养的神经元细胞中产生CTF 35（TDP-43-（90-414））和CTF 27（TDP-43-（170- 414））。与TDP-43相反，CTF 27在形成聚集体时不能诱导死亡。CTF 35在诱导死亡方面弱于全长TDP-43。TDP-43的抗裂解突变体（TDP-43-D89 E/D169 E）显示出比野生型TDP-43更强的死亡诱导活性。这些结果表明，疾病相关的半胱天冬酶激活可能会通过促进TDP-43切割来减弱TDP-43诱导的毒性。
Abnormal aggregates of transactive response DNA-binding protein-43 (TDP-43) and its hyperphosphorylated and N-terminal truncated C-terminal fragments (CTFs) are deposited as major components of ubiquitinated inclusions in most cases of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with ubiquitinated inclusions (FTLD-U). The mechanism underlying the contribution of TDP-43 to the pathogenesis of these neurodegenerative diseases remains unknown. In this study, we found that a 2-5-fold increase in TDP-43 expression over the endogenous level induced death of NSC34 motor neuronal cells and primary cortical neurons. TDP-43-induced death is associated with up-regulation of Bim expression and down-regulation of Bcl-xL expression. siRNA-mediated reduction of Bim expression attenuates TDP-43-induced death. Accumulated evidence indicates that caspases are activated in neurons of ALS and FTLD-U patients, and activated caspase-mediated cleavage of TDP-43 generates CTFs of TDP-43. Here, we further found that the ER (endoplasmic reticulum) stress- or staurosporine-mediated activation of caspases leads to cleavage of TDP-43 at Asp(89) and Asp(169), generating CTF35 (TDP-43-(90-414)) and CTF27 (TDP-43-(170- 414)) in cultured neuronal cells. In contrast to TDP-43, CTF27 is unable to induce death while it forms aggregates. CTF35 was weaker than full-length TDP-43 in inducing death. A cleavage-resistant mutant of TDP-43 (TDP-43-D89E/D169E) showed stronger death-inducing activity than wild-type TDP-43. These results suggest that disease-related activation of caspases may attenuate TDP-43-induced toxicity by promoting TDP-43 cleavage.