Howard Hughes Medical Institute, Department of Biological Sciences, Columbia University, New York, New York, USA.
Nat Chem Biol. 2010 Dec;6(12):900-6. doi: 10.1038/nchembio.467. Epub 2010 Oct 31.
A hallmark of many neurodegenerative diseases is accumulation of misfolded proteins within neurons, leading to cellular dysfunction and cell death. Although several mechanisms have been proposed to link protein misfolding to cellular toxicity, the connection remains enigmatic. Here, we report a cell death pathway involving protein disulfide isomerase (PDI), a protein chaperone that catalyzes isomerization, reduction and oxidation of disulfides. Through a small molecule screening approach, we discovered five structurally distinct compounds that prevent apoptosis induced by mutant huntingtin protein. Using modified Huisgen cycloaddition chemistry, we then identified PDI as the molecular target of these small molecules. Expression of polyglutamine-expanded huntingtin exon 1 in PC12 cells caused PDI to accumulate at mitochondrial-associated ER membranes and trigger apoptotic cell death via mitochondrial outer-membrane permeabilization. Inhibiting PDI in rat brain cells suppressed the toxicity of mutant huntingtin exon 1 and Aβ peptides processed from the amyloid precursor protein. This pro-apoptotic function of PDI represents a new mechanism linking protein misfolding and apoptotic cell death.
许多神经退行性疾病的一个标志是错误折叠的蛋白质在神经元内积累，导致细胞功能障碍和细胞死亡。尽管已经提出了几种将蛋白质错误折叠与细胞毒性联系起来的机制，但这种联系仍然很神秘。在这里，我们报告了一种涉及蛋白质二硫键异构酶（PDI）的细胞死亡途径，PDI 是一种蛋白伴侣，它催化二硫键的异构化、还原和氧化。通过小分子筛选方法，我们发现了五种结构不同的化合物，可预防突变 huntingtin 蛋白诱导的细胞凋亡。然后，我们使用改良的 Huisgen 环加成化学，鉴定了 PDI 是这些小分子的分子靶标。在 PC12 细胞中表达多聚谷氨酰胺扩展的 huntingtin 外显子 1 会导致 PDI 在与内质网相关的线粒体膜上积累，并通过线粒体外膜通透性引发细胞凋亡。在大鼠脑细胞中抑制 PDI 可抑制突变 huntingtin 外显子 1 和淀粉样前体蛋白加工的 Aβ肽的毒性。PDI 的这种促凋亡功能代表了将蛋白质错误折叠与细胞凋亡联系起来的新机制。
