The α-crystallin chaperones undergo a quasi-ordered co-aggregation process in response to saturating client interaction.
The α-crystallin chaperones undergo a quasi-ordered co-aggregation process in response to saturating client interaction.
复制标题
α-晶状体蛋白伴侣经历准有序共聚集过程以响应饱和客户交互。
DOI：
10.1101/2023.08.15.553435
复制
发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Reichow,SteveL
中科院分区：
文献类型：
--
作者：
Miller,AdamP;O'Neill,SusanE;Lampi,KirstenJ;Reichow,SteveL
小分子热休克蛋白（Small heat shock proteins，sHSPs）是一种非ATP依赖性的分子伴侣，对细胞的蛋白质稳定起重要作用，可防止蛋白质聚集，从而导致白内障等多种人类疾病。α-晶体蛋白，α A-晶体蛋白（αAc）和α B-晶体蛋白（αBc），代表了典型的sHSP，表现出复杂的多分散寡聚体组装和快速的亚基交换动力学。然而，我们对这种可塑性如何有助于伴侣功能的理解仍然知之甚少。利用生物化学和生物物理分析结合单粒子电子显微镜（EM），我们研究了αAc、αBc和天然异聚体透镜α-晶体蛋白（αLc）在脱辅基状态和不同程度的伴侣饱和导致共聚集时的结构变化，使用溶菌酶和胰岛素作为模型客户。定量单颗粒分析揭示了在共聚集过程中形成的低聚状态的连续谱，其特征在于sHSP低聚支架的显著的客户端触发的扩张和准有序的伸长，由此天然笼状sHSP组装显示定向生长以适应客户端螯合的饱和条件。这些结构修饰最终导致分子伴侣-客户复合物的明显无定形坍塌，导致能够散射可见光的共聚集体的产生。有趣的是，这些共聚集体保持了高度伸长的sHSP寡聚体的内部形态特征，与从老化的透镜组织分离的聚合α-晶状体蛋白种类具有惊人的相似性。这种机制在αAc、αBc和αLc中似乎是一致的，尽管对客户诱导的共聚集的敏感性程度不同。重要的是，我们的研究结果表明，客户端诱导的共聚集遵循一个独特的机械和准有序的轨迹，从一个纯粹的无定形过程不同。这些见解重塑了我们对α-晶体蛋白的生理和病理生理共聚集过程的理解，对白内障形成的途径具有潜在意义。
Small heat shock proteins (sHSPs) are ATP-independent chaperones vital to cellular proteostasis, preventing protein aggregation events linked to various human diseases including cataract. The α-crystallins, αA-crystallin (αAc) and αB-crystallin (αBc), represent archetypal sHSPs that exhibit complex polydispersed oligomeric assemblies and rapid subunit exchange dynamics. Yet, our understanding of how this plasticity contributes to chaperone function remains poorly understood. Using biochemical and biophysical analyses combined with single-particle electron microscopy (EM), we examined structural changes in αAc, αBc and native heteromeric lens α-crystallins (αLc) in their apo-states and at varying degree of chaperone saturation leading to co-aggregation, using lysozyme and insulin as model clients. Quantitative single-particle analysis unveiled a continuous spectrum of oligomeric states formed during the co-aggregation process, marked by significant client-triggered expansion and quasi-ordered elongation of the sHSP oligomeric scaffold, whereby the native cage-like sHSP assembly displays a directional growth to accommodate saturating conditions of client sequestration. These structural modifications culminated in an apparent amorphous collapse of chaperone-client complexes, resulting in the creation of co-aggregates capable of scattering visible light. Intriguingly, these co-aggregates maintain internal morphological features of highly elongated sHSP oligomers with striking resemblance to polymeric α-crystallin species isolated from aged lens tissue. This mechanism appears consistent across αAc, αBc and αLc, albeit with varying degrees of susceptibility to client-induced co-aggregation. Importantly, our findings suggest that client-induced co-aggregation follows a distinctive mechanistic and quasi-ordered trajectory, distinct from a purely amorphous process. These insights reshape our understanding of the physiological and pathophysiological co-aggregation processes of α-crystallins, carrying potential implications for a pathway toward cataract formation.