結締組織生長因子於阿茲海默症乙型類澱粉質生成與降解之角色

The Roles of Connective Tissue Growth Factor on Amyloid-beta Generation and Degradation in Alzheimer’s Disease

范家睿(Jia-Ruei Fan)

指導教授 ： 張正琪

國立臺灣大學/牙醫專業學院/口腔生物科學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.11205

摘要

乙型類澱粉樣蛋白(amyloid-beta, Aβ)之累積為阿茲海默症(Alzheimer's Disease, AD)的病理機轉中重要的機制，Aβ是經由澱粉樣前驅蛋白(amyloid precursor protein, APP)經由β-secretase與γ-secretase所截切而導致的水解反應而產生；而α-secretase 之截切則會阻止Aβ的生成。近年研究指出，經由調控APP水解過程抑制Aβ生成在AD的致病機轉上扮演重要的角色。人類結締組織生長因子(Connective tissue growth factor, CTGF)是一種分泌型蛋白質，目前已知數種細胞活動與疾病機轉相關。過去的文獻在AD病理切片中發現澱粉樣斑塊(senile plagues)周圍的神經具有CTGF之高表現量，然而，在阿茲海默症中人類結締組織生長因子所扮演之角色仍尚未釐清。此篇論文中，於神經纖維母細胞瘤細胞株SH-SY5Y穩定表現APP瑞典型突變(Swedish mutant)APP中發現CTGF能夠調控APP水解反應。異位性表現CTGF與人類CTGF重組蛋白之處理能夠降低細胞外Aβ的累積並減少細胞內的APP-C端片段之表現，我們更進一步的證明在細胞中CTGF能夠抑制BACE1之表現；此外，CTGF能夠促進細胞外Aβ之分解，而其作用機制並不經由提高細胞對於Aβ之吸收能力所造成。總結以上結果，在本篇論文中證明CTGF能夠抑制β-secretase之表現並進一步降低Aβ的生成而促進Aβ之分解。依據本論文之研究，期待未來CTGF可能發展成為用於治療阿茲海默症之小分子蛋白藥物。

關鍵字

人類結締組織生長因子 ； 阿茲海默症 ； 澱粉樣蛋白生成與分解 ； Beta-secretase 1

並列摘要

The accumulation of amyloid-beta (Aβ) peptide plays a critical role in the pathogenesis of Alzheimer’s disease (AD). Aβ is derived from the cleavage of amyloid precursor protein (APP) though a proteolytic processing, which is executed sequentially by β- and γ-secretases, while α-secretase cleavage intercepts Aβ generation. Currently, inhibition of Aβ generation via regulation of APP processing has been highlighted in AD pathogenesis. Connective tissue growth factor (CTGF; also known as CCN2) is a matricellular protein, which physiologically and pathologically contributes to various cellular and molecular events. In the previous study, high expression level of CTGF in amyloid plague-associated neurons has been observed. However, the role of CTGF in AD is completely unknown. Herein, we found that CTGF modulates the APP processing process in human neuroblastoma cell SH-SY5Y stably expressed Swedish mutant APP (SH-SY5Y/APPSwe). Ectopic overexpression CTGF and recombinant CTGF treatment could significantly reduced extracellular Aβ 1-42 accumulation, and simultaneously decreased the expression of APP C-terminal fragment α and β. Moreover, we proved the evidence that CTGF decrease BACE1 expression resulted in Aβ diminish in vitro. Furthermore, CTGF could enhance Aβ degradation but showed no effect in Aβ uptake ratio in SH-SY5Y/APPSwe cells. Taken together, our results provide evidences that CTGF could reduce β-secretase expression to block Aβ generation and enhance Aβ degradation. CTGF may be developed as a small protein drug to treat AD in the future.

並列關鍵字

Alzheimer's disease ； Connective tissue growth factor ； Aβ generation ； Aβ degradation ； beta-secretase 1

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