Tau蛋白
Tau蛋白(英語:Tau proteins;「Tau」為「Tubulin associated unit」即「微管蛋白相關單位」的縮寫),又譯濤蛋白[1]。是一種微管相關蛋白,在中樞神經系統的神經元非常豐富而少見於其它細胞,在中樞神經系統的星形膠質細胞和少突膠質細胞中表達量也很低[2]。tau蛋白有缺陷並不再正常穩定微管時,可導致神經系統病變和失智症,如阿茲海默病。
tau蛋白的多種蛋白異型體是由單個基因(人類基因組中為MAPT,microtubule-associated protein tau,微管相關蛋白tau)mRNA的選擇性剪接而形成的[3][4]。1975年,它們由Marc Kirschner在普林斯頓大學的實驗室中發現[5]。
功能
編輯tau蛋白是一種高度可溶的微管相關蛋白(MAP)。與非神經元細胞相較,人體內tau更多地在神經元內發現。tau蛋白的主要功能之一是維持軸突微管的穩定性。而其它神經系統中的MAPs家族蛋白也有著相似的功能,這體現在tau敲除的小鼠並沒有發現其腦組織的發育受到影響。這可能是在tau缺失後,其它MAPs家族蛋白在神經元內起到代償tau的作用,從而繼續維持軸突微管的穩定,保證腦功能的正常運作。[6] tau並不在樹突發揮功能,而主要作用在軸突遠端維持微管的穩定性和必要的靈活性。這與MAP6蛋白(位於軸突近端固定微管)與MAP2(主要維持樹突的穩定性)的功能相對。
Tau蛋白與微管蛋白(Tubulin)相互作用以穩定微管,同時驅動Tubulin在微管內組裝。Tau蛋白通過異構和磷酸化控制微管的穩定性。
結構
編輯六tau蛋白異構體存在於人類腦部組織中,以在結合區域中的編號為標識。其中三個異構體擁有三個結合區域,其餘三個異構體則有四個。此結合區域位於該蛋白的羥基末端並帶有正電(可與帶負電的微管結合)。而帶有四個結合區域的異構體有更好的穩定微管的功能。此異構體則為tau基因的2、3和10號外顯子被選擇性剪切的產物。
tau蛋白可視為一個在最長的tau蛋白異構體上擁有79個絲氨酸和蘇氨酸磷酸化位點的磷酸蛋白。有報道稱磷酸蛋白在普通tau蛋白的這些位點上的數量已達到30個左右。
磷酸蛋白同時也受激酶宿主的控制,包括PKN(絲氨酸/蘇氨酸蛋白激酶)。當PKN被激活,便會磷酸化tau蛋白從而造成微管組織破壞。
tau蛋白的磷酸蛋白也被先天性地控制。例如嬰兒中樞神經系統的tau蛋白的磷酸化程度比成人的更高。而所有異構體中的磷酸化程度由於磷酸酶的作用會隨著人年齡的增長而減弱。比如激酶,磷酸酶也在對這個tau蛋白的磷酸蛋白的調節中起到作用。
基因
編輯臨床意義
編輯tau蛋白(tau包含物,pTau)的過度磷酸化可導致配對的螺旋絲和直絲的纏結的自組裝,其參與阿茲海默症,額顳葉痴呆,和其他tau蛋白病的發病機理[7]。
腦損傷
編輯相互作用
編輯另見
編輯- Tau蛋白病變,一類與tau蛋白積累有關的疾病
- 慢性創傷性腦病變 (Chronic traumatic encephalopathy, CTE)
- 拳擊員痴呆
- 阿茲海默病
- 皮質基地變性
- Template:進行性核上性麻痹
- 蛋白質構象病
- 皮克氏病
- 17號染色體額顳葉痴呆症和帕金森氏症
- 朊病毒
參考文獻
編輯- ^ 楊雨哲, 孫承洲. 阿茲海默症的成因及治療 30 (3). 2014-09-30 [2015-01-23]. ISSN 2220-6493. (原始內容存檔於2015-01-23).
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進一步閱讀
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外部連結
編輯- 醫學主題詞表(MeSH):tau+Proteins
- GeneReviews/NCBI/NIH/UW entry on MAPT-Related Disorders(頁面存檔備份,存於網際網路檔案館)
- MR scans of variant CJD CSF Tau positive man