2014年5月29日訊/生物谷BIOON/-近日,來自賓夕法尼亞州的匹茲堡大學的Albert H Kim & Robert M Friedlander團隊在亨廷頓症候群的發病機制中獲得了突破,他們發現突變的huntingtin蛋白能夠抑制其他的線粒體蛋白向線粒體內的轉運。
亨廷頓病性痴呆由Huntington於1872年首先報導,故而得名。屬單基因常染色體顯性遺傳疾病。其腦變性部位廣泛,尤以尾狀核的萎縮明顯,系一種罕見的特發性神經變性疾病。臨床主要表現為痴呆和舞蹈樣動作。
亨廷頓疾病在細胞水平上表現為線粒體功能喪失相關的神經元的減少,這種神經退化疾病的分子機制為huntingtin (Htt)中插入了異常多聚穀氨醯胺片段。然而在亨廷頓疾病中突變的Htt和線粒體功能喪失之間的關係之前並沒有得到深入的研究。
Albert H Kim & Robert M Friedlander團隊發現突變的huntingtin蛋白能夠抑制其他的線粒體蛋白向線粒體內的轉運,這項研究發表在Nature Neuroscience上。他們發現突變的Htt和TIM23線粒體蛋白轉運複合體結合。同樣,在體外實驗中表達重組的Htt突變體能夠直接抑制線粒體蛋白的轉運。
進一步的實驗發現,在症狀出現前的亨廷頓動物模型中突出的線粒體表現出蛋白轉運障礙,在突變的Htt表達的原代神經元中也出現了同樣的現象,這些表明線粒體蛋白轉運障礙是亨廷頓疾病的一個早期事件。
通過過表達TIM23複合體的亞基能夠逆轉突變Htt誘導的線粒體轉運缺陷和隨之而來的神經死亡,這也說明了線粒體蛋白轉運缺陷是突變Htt誘導的神經死亡的原因。
這項研究對於突變的Htt,線粒體功能的缺陷和神經病理之間提供了直接的聯繫,為亨廷頓疾病提供了新的治療思路,即基於線粒體蛋白轉運的治療。(生物谷Bioon.com)
Inhibition of mitochondrial protein import by mutant huntingtin
Hiroko Yano, Sergei V Baranov, Oxana V Baranova, Jinho Kim, Yanchun Pan, Svitlana Yablonska, Diane L Carlisle, Robert J Ferrante, Albert H Kim & Robert M Friedlander
Mitochondrial dysfunction is associated with neuronal loss in Huntington's disease (HD), a neurodegenerative disease caused by an abnormal polyglutamine expansion in huntingtin (Htt). However, the mechanisms linking mutant Htt and mitochondrial dysfunction in HD remain unknown. We identify an interaction between mutant Htt and the TIM23 mitochondrial protein import complex. Remarkably, recombinant mutant Htt directly inhibited mitochondrial protein import in vitro. Furthermore, mitochondria from brain synaptosomes of presymptomatic HD model mice and from mutant Htt-expressing primary neurons exhibited a protein import defect, suggesting that deficient protein import is an early event in HD. The mutant Htt–induced mitochondrial import defect and subsequent neuronal death were attenuated by overexpression of TIM23 complex subunits, demonstrating that deficient mitochondrial protein import causes mutant Htt-induced neuronal death. Collectively, these findings provide evidence for a direct link between mutant Htt, mitochondrial dysfunction and neuronal pathology, with implications for mitochondrial protein import–based therapies in HD.