探究磷酸化濤蛋白纖維的形成

Abstract

濤蛋白為一種微管結合蛋白，主要功能為維持微管的結構穩定並協助神經訊號傳遞正常運作，一旦一些磷酸激酶像肝醣合成激酶過度磷酸化濤蛋白，使其形成高度磷酸化的濤蛋白，這些過度磷酸化的濤蛋白則會降低和微管結合的能力而游離在細胞中，進一步聚集堆疊形成成對螺旋配對纖維，再進一步堆疊形成神經纖維糾結，這些糾結對神經細胞產生毒性病導致阿茲海默症。 到目前為止，因為製備磷酸化蛋白並不容易，因此許多研究針對濤蛋白而不是過度磷酸化的濤蛋白，所以建立一個可以表現磷酸化的濤蛋白很重要。有研究指出在肝素誘導形成的濤蛋白纖維結構中的 275VQIINK280 和 306VQIVYK311 為形成纖維的核心區域，最近則有另一研究使用冷凍電子顯微鏡去觀察由阿茲海默病患腦中取出的神經纖維糾結，則發現只有在 306VQIVYK311 被包含在形成纖維的核心區域。 在我們的研究主題中，我們想要了解究竟濤蛋白和過度磷酸化的濤蛋白在形成纖維是否會使用不一樣的區域進行堆疊；除此之外，我們也想了解是否一些轉譯後修飾會影響纖維形成；最後，依據我們對濤蛋白纖維的了解，我們嘗試設計胜肽抑制物期望可以抑制纖維的形成，希望可以做為治療阿茲海默症的藥物。

Tau protein is a microtubule-associated protein which can stabilize the microtubule and help the signal transduction work normally. When kinases like GSK over phosphorylates tau, the hyperphosphorylated tau (p-tau) cannot bind to microtubules but forms paired helical filaments and turn into neurofibrillary tangles. These neurofibrillary tangles lead to neuron death and eventually cause Alzheimer’s disease (AD). So far, most of the structural studies focus on tau but not p-tau because of the difficulty in preparing phosphorylated protein. Establishing the p-tau expression system is important for tau research. It has been reported that 275VQIINK280 and 306VQIVYK311 are the core regions of the in vitro heparin-induced tau fibrils. Very recently, cryo-EM data showed that only 306VQIVYK311 is in the amyloid core region of the p-tau paired helical filaments obtained from AD patients. In this study, we aimed to investigate whether the fibrils formed of tau and p-tau might use different regions as the amyloid core. In addition, we wanted to know whether the post-translational modification near the fibril core region can affect the fibril formation. Furthermore, based on our knowledge about the p-tau fibrils, we aim to design the peptide inhibitors to suppress the p-tau fibril formation as a therapeutic strategy to treat AD.