Huynen Céline, Willet Nicolas, Buell Alexander K, Duwez Anne-Sophie, Jerôme Christine, Dumoulin Mireille
Laboratory of Enzymology and Protein Folding, Centre for Protein Engineering, University of Liege, Liege, Belgium.
Nanochemistry and Molecular Systems, Department of Chemistry, University of Liege, Liege, Belgium.
Biochim Biophys Acta. 2015 Mar;1854(3):239-48. doi: 10.1016/j.bbapap.2014.12.002. Epub 2014 Dec 6.
Polyglutamine (polyQ) diseases, including Huntington's disease, are neurodegenerative disorders associated with the abnormal expansion of a polyQ tract within nine proteins. The polyQ expansion is thought to be a major determinant in the development of neurotoxicity, triggering protein aggregation into amyloid fibrils, although non-polyQ regions play a modulating role. In this work, we investigate the relative importance of the polyQ length, its location within a host protein, and the conformational state of the latter in the amyloid fibril elongation. Model polyQ proteins made of the β-lactamase BlaP containing up to 79Q inserted at two different positions, and quartz crystal microbalance and atomic force microscopy were used for this purpose. We demonstrate that, independently of the polyQ tract location and the conformational state of the host protein, the relative elongation rate of fibrils increases linearly with the polyQ length. The slope of the linear fit is similar for both sets of chimeras (i.e., the elongation rate increases by ~1.9% for each additional glutamine), and is also similar to that previously observed for polyQ peptides. The elongation rate is, however, strongly influenced by the location of the polyQ tract within BlaP and the conformational state of BlaP. Moreover, comparison of our results with those previously reported for aggregation in solution indicates that these two parameters also modulate the ability of BlaP-polyQ chimeras to form the aggregation nucleus. Altogether our results suggest that non-polyQ regions are valuable targets in order to interfere with the process of amyloid fibril formation associated with polyQ diseases.
包括亨廷顿舞蹈症在内的多聚谷氨酰胺（polyQ）疾病是与9种蛋白质中多聚谷氨酰胺序列异常扩增相关的神经退行性疾病。尽管非多聚谷氨酰胺区域起调节作用，但多聚谷氨酰胺扩增被认为是神经毒性发展的主要决定因素，它会引发蛋白质聚集成淀粉样原纤维。在这项研究中，我们调查了多聚谷氨酰胺长度、其在宿主蛋白中的位置以及宿主蛋白的构象状态在淀粉样原纤维伸长过程中的相对重要性。为此，我们构建了由β-内酰胺酶BlaP组成、在两个不同位置插入多达79个谷氨酰胺的模型多聚谷氨酰胺蛋白，并使用石英晶体微天平及原子力显微镜进行研究。我们证明，与多聚谷氨酰胺序列的位置和宿主蛋白的构象状态无关，原纤维的相对伸长率随多聚谷氨酰胺长度呈线性增加。两组嵌合体的线性拟合斜率相似（即每增加一个谷氨酰胺，伸长率增加约1.9%），并且与先前观察到的多聚谷氨酰胺肽的情况也相似。然而，伸长率受多聚谷氨酰胺序列在BlaP中的位置以及BlaP构象状态的强烈影响。此外，将我们的结果与先前报道的在溶液中聚集的结果进行比较表明，这两个参数也调节了BlaP-多聚谷氨酰胺嵌合体形成聚集核的能力。我们的结果表明，非多聚谷氨酰胺区域是干扰与多聚谷氨酰胺疾病相关的淀粉样原纤维形成过程的重要靶点。
