近日，我组设计和制备了一对手性氨基酸修饰的磷脂分子，并且构筑了手性磷脂囊泡，成功实现了对朊蛋白片段（PrP106-126）纤维化过程的精确调控。
朊蛋白是一种臭名昭著的蛋白质，可引起具有传染性和快速进展的神经退行性疾病。虽然朊蛋白疾病的传播频率相对较低，但由于其潜伏期长，致死率高，给疾病控制和公众健康带来了不可预知的风险。研究发现朊蛋白错误折叠的过程常发生于细胞的小窝状区域，此区域富含脂类，因此研究朊蛋白与磷脂的相互作用是非常必要的。以往研究表明，正常朊蛋白与带负电荷的膜结合，形成富含纤维化的结构。然而，关于磷脂膜手性如何影响朊蛋白聚集的研究却很少。一般来说，天然磷脂分子对其L-对映体表现出强烈的偏好，细胞膜上覆盖着大量手性生物分子，如氨基酸、多肽、蛋白质和多糖。这些手性生物分子要么嵌入磷脂双分子层，要么修饰在磷脂分子的顶端。重要的是，氨基酸手性已被认为是决定侧链方向、肽主链折叠、通过立体选择性氢键作用与来宾体特异性结合，甚至蛋白质生物功能的主要驱动力。因此，研究手性氨基酸修饰的磷脂对朊蛋白的错误折叠和聚集的影响是至关重要的。
本研究选择手性天冬氨酸(Asp)修饰磷脂，与D-脂质体相比，发现L-脂质体明显的抑制了朊蛋白的纤维化，因此小鼠神经母瘤细胞中钙离子和活性氧处于正常稳态。后通过吸附动力学、亲和力评价和荧光共定位实验分析了抑制朊蛋白聚集的具体机制，结果表明无论在细胞环境内或无细胞环境，朊蛋白在L-磷脂表面的结合能力都大大高于在D-磷脂面的结合能力。L-脂质体对朊蛋白纤维化的抑制效果优于D-脂质体，此研究为脂质体类抑制剂的发展提供了一个新的方向。相关成果发表在《中国化学快报》Chinese Chemical Letters，第一作者是18T7组博士研究生王存利、王雪。以上研究工作得到国家自然科学基金项目、我所创新特区组启动基金、兴辽英才计划等项目的支持。
Remarkable difference of phospholipid molecular chirality in regulating PrP aggregation and cell responses
Cunli Wang, Xue Wang, Dongdong Wang, Shengxu Qian, Fusheng Zhang, Mingyang Li, Minmin Li, Wenqi Lu, Bo Liu, Guangyan Qing*
Chinese Chemical Letters, 2022, DOI:10.1016/ j.cclet.2022.03.055
Prion diseases are fatal neurodegenerative diseases that can cause severe dementia. The misfolding and accumulation of the prion peptide (PrP)106-126 is crucial, and this process is closely relevant to biological membranes. However, how PrP106-126 aggregation is affected by the molecular chirality of phospholipid membrane is unknown. Thus, in this study, a pair of L- and D-aspartic acid (Asp)-modified 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) were synthesized to construct chiral liposomes. We discover that L-Asp-DPPE liposomes strongly inhibit the oligomerization and amyloidogenesis of PrP106-126, whether acting on monomers or oligomers, which rescues cytotoxicity induced by PrP106-126. By comparison, D-Asp-DPPE liposomes inhibit peptide oligomerization only at a high concentration and cannot prevent amyloidogenesis when acting on oligomers, which lead to pronounced cytotoxicity. Apoptosis experiment, dynamic change of intracellular Ca2+ (iCa2+) and Ca2+ release from endoplasmic reticulum (ER), reactive oxygen species (ROS) production, adsorption dynamics and affinity tests, and fluorescent imaging clearly disclose that molecular chirality of the liposomes dominates conformational transition of PrP106-126 from random coil to b-sheet, binding and adsorption of the monomers and oligomers, and subsequent fibrillation process, resulting in distinct inhibition effect in Ca2+ overload and release, ROS production and cell apoptosis. This work is the first to report that interfacial molecular chirality is a potentially crucial influence on the fibrillation process of PrP106-126 and its cell responses, whereas the convergence of chiral amino acids and liposomes can be considered potential inhibitors in prion diseases.
