現今許多的神經退化性疾病，包括: 阿茲海默症、漢丁頓舞蹈症、運動神經元退化性疾病、帕金森氏病和肌萎縮性脊髓側索硬化症等都已經被證實與蛋白質形成inclusion body，以及蛋白質於分子和細胞間產生不正常聚集體的機制有極大的關係；而那些所產生的聚集體通常以纖維的形態出現，而且這些纖維是由β-sheet 摺疊所構成。在神經退化性疾病中，肌萎縮性脊髓側索硬化症是位居成人死亡的第三名，僅次於阿茲海默症和帕金森氏症，同時是最多的成人運動神經元退化性疾病；這種疾病會造成肌肉逐漸萎縮以及漸進式地退化其身體運動機能，並且會在幾年內死亡。然而，目前對於肌萎縮性脊髓側索硬化症的致病機制以及治療方法依然不清楚。在2006年時，包含了414個胺基酸的TAR DNA-binding protein (TDP-43)被認為是肌萎縮性脊髓側索硬化症及腦前額顳葉退化症的inclusion body裡主要的組成。最近已經有許多研究證明，在肌萎縮性脊髓側索硬化症及腦前額顳葉退化症病人的inclusion body中，所找到TDP-43的C端大部分都有被高度磷酸化的現象。為了更進一步探討TDP-43的C端在肌萎縮性脊髓側索硬化症的病人中所扮演的角色，我們將TDP-43的C端切成四個片段(D1-D4)，探討其結構與不正常聚集體沉澱及纖維形成之間的關係。令人感到有趣的是，在磷酸鈉緩衝溶液培養兩個禮拜之後，只有D1片段會形成纏繞的纖維；而在D2、D3 和 D4方面，在穿透式電子顯微鏡的觀察下只有形成不特定形狀的聚集體並沒有纖維的產生。此外，我們亦合成D1片段的兩條變異的胜肽片段為A315T 和G294A，而這兩條胜肽也會形成纖維的結構，且所產生的纖維結構與神經內的細胞質inclusions相似。同時，我們利用圓二色光譜儀去追蹤二級結構的變化，只有G294A有明顯的結構轉變。除此之外，我們利用拉曼光譜儀以及螢光光譜儀成功定義了D1、A315T 和 G294A的纖維結構特性。我們發現在加入ThT之後，只有G294A有很強的放射光訊號；而從拉曼光譜的結果來看， D1、A315T 和 G294A的結構特性是屬於beta類澱粉沉澱。我們推論在所合成的D1片段中(序列: 287-322)包含了許多甘胺酸重複的序列，使這段序列扮演了很重要的角色，而造成此片段形成纖維結構和不正常聚集體產生的主要原因。

Many neurodegenerative diseases (NDDs), including Alzheimer’s disease (AD), Huntington’s disease (HD), Motor neuron disease (MND), Parkinson’s disease (PD), and Amyotrophic lateral sclerosis (ALS), have been realized to associate with inclusion body formation and protein aggregation of molecular and cellular mechanisms. These aggregates usually appear as fibril morphology and consist of β-sheet structure. ALS is the third common neuron degenerative cause of adult death, after AD and PD. It is also the most adult-onset motor neuron disease (MND), cause of progressive weakness, muscular wasting, and death within a few years. However, the exhaustive mechanism and the possible treatment for this disease remained unavailable. In 2006, TAR DNA-binding protein (TDP-43), containing 414 residues, was identified as the main sediments in the histopathological inclusion bodies of ALS and frontotemporal lobar degeneration (FTLD-U). Recent literatures have further indicated that the major component in the inclusions of ALS and FTLD patients were hyperphosphorylated TDP-43 C-terminal fragments. In order to understand the role of C-terminal domain of TDP-43 in ALS, we have synthesized four peptide fragments located in different regions of C-terminus to uncover the relationship between fibrial structure and aggregation state. Interestingly, only the D1 formed twisted fibrils after incubating in phosphate buffer for two weeks. D2, D3 and D4, on the other hand, were detected as amorphous aggregates by EM measurement. Moreover, two pathological mutant peptides, A315T and G294A, also had the ability to form fibrils that displayed the similar morphology with neuronal cytoplasmic inclusions (NCIs). In the meantime, we used the circular dichroism (CD) spectroscopy to trace the change of secondary structure. It revealed that only the G294A had significantly been altered. Moreover, we successfully identified the specific conformation of D1, A315T, and G294A peptide fragments by applying fluorescence and Raman spectroscopy. We found only G294A had strong emission with the addition of ThT. From the results of FT-Raman spectra, the aggregation of all three peptides belongs to amyloid structures. Base on these results, we proposed that the region (sequence: 287-322) contains many glycine repeats in C-terminus may play an important role in the fibril formation as well as aggregation formation.

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