The C. Eugene Bennett Department of Chemistry, West Virginia University, 217 Clark Hall, Morgantown, WV 26506, United States.
Division of Exercise Physiology, West Virginia School of Medicine, Morgantown, WV 26506, United States; Mitochondria, Metabolism & Bioenergetics Working Group, West Virginia University School of Medicine, Morgantown, WV, USA.
Biochim Biophys Acta Biomembr. 2021 Oct 1;1863(10):183663. doi: 10.1016/j.bbamem.2021.183663. Epub 2021 Jun 2.
Huntington's disease (HD) is a neurodegenerative disease caused by the expansion of a polyglutamine (polyQ) tract near the N-terminus of the huntingtin (htt) protein. Expanded polyQ tracts are prone to aggregate into oligomers and insoluble fibrils. Mutant htt (mhtt) localizes to variety of organelles, including mitochondria. Specifically, mitochondrial defects, morphological alteration, and dysfunction are observed in HD. Mitochondrial lipids, cardiolipin (CL) in particular, are essential in mitochondria function and have the potential to directly interact with htt, altering its aggregation. Here, the impact of mitochondrial membranes on htt aggregation was investigated using a combination of mitochondrial membrane mimics and tissue-derived mitochondrial-enriched fractions. The impact of exposure of outer and inner mitochondrial membrane mimics (OMM and IMM respectively) to mhtt was explored. OMM and IMM reduced mhtt fibrillization, with IMM having a larger effect. The role of CL in mhtt aggregation was investigated using a simple PC system with varying molar ratios of CL. Lower molar ratios of CL (<5%) promoted fibrillization; however, increased CL content retarded fibrillization. As revealed by in situ AFM, mhtt aggregation and associated membrane morphological changes at the surface of OMM mimics was markedly different compared to IMM mimics. While globular deposits of mhtt with few fibrillar aggregates were observed on OMM, plateau-like domains were observed on IMM. A similar impact on htt aggregation was observed with exposure to purified mitochondrial-enriched fractions. Collectively, these observations suggest mitochondrial membranes heavily influence htt aggregation with implication for HD.
亨廷顿病（HD）是一种神经退行性疾病，由亨廷顿蛋白（htt）蛋白 N 端附近的聚谷氨酰胺（polyQ）片段扩展引起。扩展的 polyQ 片段易于聚集形成寡聚物和不溶性纤维。突变的 htt（mhtt）定位于多种细胞器，包括线粒体。具体而言，在 HD 中观察到线粒体缺陷、形态改变和功能障碍。线粒体脂质，特别是心磷脂（CL），对于线粒体功能至关重要，并且有可能直接与 htt 相互作用，改变其聚集。在这里，使用线粒体膜模拟物和组织衍生的富含线粒体的部分的组合研究了线粒体膜对 htt 聚集的影响。探索了暴露于外线粒体膜模拟物（OMM）和内线粒体膜模拟物（IMM）对 mhtt 的影响。OMM 和 IMM 减少了 mhtt 的纤维化，而 IMM 的影响更大。通过具有不同 CL 摩尔比的简单 PC 系统研究了 CL 在 mhtt 聚集中的作用。较低的 CL 摩尔比（<5％）促进了纤维化；然而，增加 CL 含量会延迟纤维化。通过原位 AFM 揭示，与 IMM 模拟物相比，mhtt 聚集及其在 OMM 模拟物表面的相关膜形态变化明显不同。在 OMM 上观察到 mhtt 的球状沉积物，很少有纤维状聚集体，而在 IMM 上观察到类似的板状区域。暴露于纯化的富含线粒体的部分也观察到对 htt 聚集的类似影响。总之，这些观察结果表明线粒体膜对 htt 聚集有很大影响，这对 HD 具有影响。
