Rambold Angelika S, Miesbauer Margit, Rapaport Doron, Bartke Till, Baier Michael, Winklhofer Konstanze F, Tatzelt Jörg
Department of Biochemistry, Neurobiochemistry, Ludwig-Maximilians-Universität München, D-80336 München, Germany.
Mol Biol Cell. 2006 Aug;17(8):3356-68. doi: 10.1091/mbc.e06-01-0083. Epub 2006 May 17.
Protein misfolding is linked to different neurodegenerative disorders like Alzheimer's disease, polyglutamine, and prion diseases. We investigated the cytotoxic effects of aberrant conformers of the prion protein (PrP) and show that toxicity is specifically linked to misfolding of PrP in the cytosolic compartment and involves binding of PrP to the anti-apoptotic protein Bcl-2. PrP targeted to different cellular compartments, including the cytosol, nucleus, and mitochondria, adopted a misfolded and partially proteinase K-resistant conformation. However, only in the cytosol did the accumulation of misfolded PrP induce apoptosis. Apoptotic cell death was also induced by two pathogenic mutants of PrP, which are partially localized in the cytosol. A mechanistic analysis revealed that the toxic potential is linked to an internal domain of PrP (amino acids 115-156) and involves coaggregation of cytosolic PrP with Bcl-2. Increased expression of the chaperones Hsp70 and Hsp40 prevented the formation of PrP/Bcl-2 coaggregates and interfered with PrP-induced apoptosis. Our study reveals a compartment-specific toxicity of PrP misfolding that involves coaggregation of Bcl-2 and indicates a protective role of molecular chaperones.
蛋白质错误折叠与不同的神经退行性疾病相关，如阿尔茨海默病、多聚谷氨酰胺病和朊病毒疾病。我们研究了朊病毒蛋白（PrP）异常构象的细胞毒性作用，结果表明毒性与胞质区室中PrP的错误折叠特异性相关，并且涉及PrP与抗凋亡蛋白Bcl-2的结合。靶向不同细胞区室（包括胞质溶胶、细胞核和线粒体）的PrP呈现出错误折叠且部分抗蛋白酶K的构象。然而，只有在胞质溶胶中，错误折叠的PrP积累才会诱导细胞凋亡。PrP的两个致病突变体（部分定位于胞质溶胶中）也诱导了凋亡性细胞死亡。机制分析表明，毒性潜能与PrP的一个内部结构域（氨基酸115 - 156）相关，并且涉及胞质PrP与Bcl-2的共聚集。伴侣蛋白Hsp70和Hsp40表达的增加阻止了PrP/Bcl-2共聚集体的形成，并干扰了PrP诱导的细胞凋亡。我们的研究揭示了PrP错误折叠的区室特异性毒性，其涉及Bcl-2的共聚集，并表明分子伴侣具有保护作用。
