JBC：神经元代谢以及变性疾病中TDP-43及FUS的作用

在肌萎缩侧索硬化和额颞叶痴呆病人的病理组织中，RNA结合蛋白TDP-43及FUS在细胞质中形成了不正常的凝集，但是其作用机理还不明确。近日，印度米兰比可卡大学的Antonia Ratti等人研究发现，TDP-43和FUS能够识别不同的转录产物，而且差异性的调节它们的命运。相关研究发表在3月16日的美国《生化周刊》（Journal of Biological Chemistry）上。

在肌萎缩侧索硬化和额颞叶痴呆病人的病理组织中，RNA结合蛋白TDP-43及FUS在细胞质中形成了不正常的凝集。已知TDP-43和FUS主要定位于细胞核内，参与调节pre-mRNA的剪接，但是他们也与mRNA的转运、稳定性及翻译有关。为了更好的研究它们胞浆活性，我们利用RNA免疫沉淀以及芯片分析来确定与它们有关的mRNA。

研究发现，虽然作用于相同的细胞内通路，它们却结合在mRNA的不同位点。生物信息分析鉴定了80%的位于3'UTR TDP-43靶点的(UG)n一致序列模体。然而，对于FUS，这个结合模体还不太明确。通过体外分析，研究人员确定，结合在选择性靶向3'UTRs的模体有：结合在TDP-43蛋白的Vegfa和Grn及结合FUS蛋白的Vps54、Nvl以及Taf15。

研究表明，TDP-43对Vegfa及Grn mRNA有着还不确定的作用，这样的作用很可能会根本性的影响Progranulin蛋白含量。然而FUS不会影响mRNA的稳定性及翻译过程。实验也证明，位于TDP-43三个不同的点突变不会改变它对Vegfa及Grn mRNAs的亲和性或者是它的表达水平。

数据表明，TDP-43及FUS可以识别mRNA的特异位点，并差异性的调节它们在运动神经元样细胞细胞质中的命运。这表明，在神经元细胞的RNA代谢和神经元变性中，TDP-43及FUS起到了辅助作用。（生物谷Bioon.com）

doi: 10.1074/jbc.M111.333450
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TDP-43 and FUS RNA-binding proteins bind distinct sets of cytoplasmic messenger RNAs and differently regulate their post-transcriptional fate in motoneuron-like cells

Claudia Colombrita, Elisa Onesto, Francesca Megiorni, Antonio Pizzuti, Francisco E. Baralle, Emanuele Buratti, Vincenzo Silani and Antonia Ratti

The RNA-binding proteins TDP-43 and FUS form abnormal cytoplasmic aggregates in affected tissues of patients with amyotrophic lateral sclerosis and frontotemporal lobar dementia. TDP-43 and FUS localize mainly in the nucleus where they regulate pre-mRNA splicing, but they are also involved in mRNA transport, stability and translation. To better investigate their cytoplasmic activities, we applied a RNA immunoprecipitation and chip analysis to define the mRNAs associated to TDP-43 and FUS in the cytoplasmic ribonucleoprotein complexes from motoneuronal NSC-34 cells.We found that they bind different sets of mRNAs although converging on common cellular pathways. Bioinformatical analyses identified the (UG)n consensus motif in 80% of 3'UTR sequences of TDP-43 targets, while for FUS the binding motif was less evident. By in vitro assays we validated binding to selected target 3'UTRs, including Vegfa and Grn for TDP-43, and Vps54, Nvl and Taf15 for FUS.We showed that TDP-43 has a destabilizing activity on Vegfa and Grn mRNA and may ultimately affect Progranulin protein content, while FUS does not affect mRNA stability/translation of its targets. We also demonstrated that three different point mutations in TDP-43 did not change the binding affinity for Vegfa and Grn mRNAs or their protein level.Our data indicate that TDP-43 and FUS recognize distinct sets of mRNAs and differently regulate their fate in the cytoplasm of motoneuron-like cells, therefore suggesting complementary roles in neuronal RNA metabolism and urodegeneration..