Dasari Anvesh K R, Sengupta Urmi, Viverette Elizabeth, Borgnia Mario J, Kayed Rakez, Lim Kwang Hun
Department of Chemistry, East Carolina University, Greenville, NC, 27858, USA.
Departments of Neurology, Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX, 77555, USA.
Biochem Biophys Rep. 2024 Mar 19;38:101687. doi: 10.1016/j.bbrep.2024.101687. eCollection 2024 Jul.
Aggregation of α-synuclein into oligomers and fibrils is associated with numerous neurodegenerative diseases such as Parkinson's disease (PD). Although the identity of the pathogenic species formed during the aggregation process is still under active debate, mounting evidence suggests that small oligomeric species rather than fibrillar aggregates are real toxic species. Isolation and characterization of small oligomers is essential to developing therapeutic strategies to prevent oligomer formation. Preparation of misfolded oligomeric species for biophysical characterization is, however, a great challenge due to their heterogenous, transient nature. Here we report the preparation of toxic and non-toxic α-synuclein oligomeric species formed at different pH values in the presence of lipid vesicles that mimic mitochondria membranes containing cardiolipin. Biophysical characterization of the lipid-induced α-synuclein oligomeric assemblies revealed that α-synuclein oligomers formed at pH 7.4 have higher surface hydrophobicity than the aggregates formed at pH 6.0. In addition, the high-pH oligomers were shown to exhibit higher toxicity than the low-pH aggregates. Structural, dynamic properties of the oligomers were also investigated by using circular dichroism (CD) and NMR spectroscopy. Our CD analyses revealed that the two oligomeric species have distinct molecular conformations, and 2D H/N HSQC NMR experiments suggested that the high-pH oligomers have more extended dynamic regions than the low-pH aggregates. The distinct structural and dynamic properties of the oligomers might be associated with their different cytotoxic properties.
α-突触核蛋白聚集成寡聚体和纤维与许多神经退行性疾病相关，如帕金森病（PD）。尽管在聚集过程中形成的致病物种的身份仍在激烈争论中，但越来越多的证据表明，小的寡聚物种而非纤维状聚集体才是真正的有毒物种。分离和表征小寡聚体对于开发预防寡聚体形成的治疗策略至关重要。然而，由于其异质性和瞬态性质，制备用于生物物理表征的错误折叠寡聚物种是一项巨大挑战。在此，我们报告了在存在模拟含心磷脂线粒体膜的脂质囊泡的情况下，在不同pH值下形成的有毒和无毒α-突触核蛋白寡聚物种的制备。脂质诱导的α-突触核蛋白寡聚体组装体的生物物理表征表明，在pH 7.4形成的α-突触核蛋白寡聚体比在pH 6.0形成的聚集体具有更高的表面疏水性。此外，高pH值的寡聚体显示出比低pH值的聚集体更高的毒性。还通过圆二色性（CD）和核磁共振（NMR）光谱研究了寡聚体的结构和动态性质。我们的CD分析表明，这两种寡聚体物种具有不同的分子构象，二维H/N HSQC NMR实验表明，高pH值的寡聚体比低pH值的聚集体具有更扩展的动态区域。寡聚体独特的结构和动态性质可能与其不同的细胞毒性性质有关。
