3月30日,，美國The FASEB Journal在線發(fā)表了中科院上海生命科學研究院生化與細胞所胡紅雨課題組的研究論文,。該論文闡明了TDP-43蛋白的降解片段TDP-35是其在細胞質(zhì)內(nèi)形成包涵體的主要原因,，并且包涵體的形成引起該蛋白質(zhì)參與RNA加工功能的改變。
肌萎縮側(cè)索硬化癥(Amyotrophic Lateral Sclerosis, ALS)和額顳葉變性（Frontotemporal Lobar Degeneration,，F(xiàn)TLD)是兩類有類似臨床表征的神經(jīng)退行性疾病,，它們的主要病理特征是神經(jīng)元的退化，而存活的神經(jīng)細胞內(nèi)有大量包涵體存在,。在這兩類疾病患者神經(jīng)細胞的包涵體中發(fā)現(xiàn)有TDP-43蛋白及其C-端裂解產(chǎn)物的大量沉積,。TDP-43蛋白的N-端含有兩個串聯(lián)的RNA識別模體，而C-端為豐富甘氨酸的天然無結(jié)構(gòu)區(qū)域,。在病理情況下,，TDP-43蛋白會發(fā)生片段化，產(chǎn)生兩個C-端的降解片段,。然而,，TDP-43發(fā)生積聚的分子機制以及形成的包涵體對細胞造成的影響還不清楚。
博士生車美霞等人首先利用生物化學和細胞生物學方法研究了TDP-43片段化對包涵體形成及對細胞mRNA加工的影響,。在HEK 293T細胞株中過表達TDP-43及其C-端片段時發(fā)現(xiàn),，TDP-43蛋白定位于細胞核內(nèi)且不形成包涵體；而TDP-35在細胞質(zhì)中形成包涵體,，并且能夠?qū)DP-43蛋白招募至細胞質(zhì)包涵體中,。TDP-43蛋白參與mRNA前體的剪切，而TDP-35則表現(xiàn)出與其相反的功能,。通過對體外純化蛋白質(zhì)的研究發(fā)現(xiàn),，TDP-43蛋白雖然是一個寡聚體，但不容易積聚形成沉淀,，而TDP-35蛋白則容易積聚形成沉淀,；而且TDP-35蛋白具有種子效應，能夠促進TDP-43蛋白的積聚和沉淀,，這可能是病理情況下TDP-43蛋白形成包涵體的一個重要因素,。
這些研究成果加深了人們對于細胞內(nèi)包涵體形成和上述兩類神經(jīng)退行性疾病病理發(fā)生過程的認識。
該研究工作得到了國家科技部,、基金委,、中國科學院的經(jīng)費支持。（生物谷Bioon.com）
生物谷推薦原文出處：
The FASEB Journal doi: 10.1096/fj.10-174482
Aggregation of the 35-kDa fragment of TDP-43 causes formation of cytoplasmic inclusions and alteration of RNA processing
Mei-Xia Che, Ya-Jun Jiang, Yuan-Yuan Xie, Lei-Lei Jiang and Hong-Yu Hu1
TAR DNA binding protein of 43 kDa (TDP-43) is a nuclear factor functioning in RNA processing. It is also a major deposited protein in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with ubiquitin (FTLD-U). To understand the mechanism underlying the inclusion body formation and possible functional alteration, we studied some TDP-43 fragments and their effects on RNA processing in cell models. The results show that the 35-kDa fragment of TDP-43 (namely TDP-35, residues 90–414), but not TDP-25A (184–414), is capable of forming cytoplasmic inclusion bodies and altering pre-mRNA splicing. The inclusions formed by TDP-35 can also recruit full-length TDP-43 to cytoplasmic deposition from functionally nuclear localization. The in vitro studies demonstrate that TDP-35, rather than TDP-43 and TDP-25A, is prone to aggregation, and it further serves as a seed to facilitate aggregation of full-length TDP-43. This suggests that fragmentation of TDP-43 leads to cellular redistribution, inclusion body formation, and altered RNA processing, which are implicated in the molecular pathogenesis of ALS and FTLD.—Che, M.-X., Jiang, Y.-J., Xie, Y.-Y., Jiang, L.-L., Hu, H.-Y. Aggregation of the 35-kDa fragment of TDP-43 causes formation of cytoplasmic inclusions and alteration of RNA processing.
