Niyangoda Chamani, Barton Jeremy, Bushra Nabila, Karunarathne Kanchana, Strauss Graham, Fakhre Fadia, Koria Piyush, Muschol Martin
Dept. of Physics, University of South Florida Tampa FL 33620 USA
Dept. of Chemical and Biomedical Engineering, University of South Florida Tampa FL 33620 USA.
RSC Chem Biol. 2021 Aug 25;2(6):1631-1642. doi: 10.1039/d1cb00081k. eCollection 2021 Dec 2.
There is compelling evidence that small oligomeric aggregates, emerging during the assembly of amyloid fibrils and plaques, are important molecular pathogens in many amyloid diseases. While significant progress has been made in revealing the mechanisms underlying fibril growth, understanding how amyloid oligomers fit into the fibril assembly process, and how they contribute to the pathogenesis of amyloid diseases, has remained elusive. Commonly, amyloid oligomers are considered to be metastable, early-stage precursors to fibril formation that are either on- or off-pathway from fibril growth. In addition, amyloid oligomers have been reported to colocalize with late-stage fibrils and plaques. Whether these early and late-stage oligomer species are identical or distinct, and whether both are relevant to pathogenesis remains unclear. Here we report on the formation of two distinct oligomer species of lysozyme, formed either during the early or late-stages of fibril growth. We further observe that the pH change from growth conditions to cell media used for toxicity studies induced distinct mesoscopic precipitates, two of which resemble either diffuse or neuritic plaques seen in Alzheimer's histology. Our biophysical characterization indicates that both oligomer species share morphological and tinctorial features considered characteristic for amyloid oligomers. At the same time, their sizes, morphologies, their immunostaining, detailed tinctorial profiles and, most prominently, their biological activity are clearly distinct from each other. Probing the conditions promoting the formation of these two distinct oligomer species suggests distinct roles of charge interactions, hydrophobicity and monomer flexibility in directing oligomer assembly.
有令人信服的证据表明，在淀粉样纤维和斑块组装过程中出现的小寡聚聚集体是许多淀粉样疾病中的重要分子病原体。虽然在揭示纤维生长的潜在机制方面已经取得了重大进展，但了解淀粉样寡聚体如何融入纤维组装过程以及它们如何导致淀粉样疾病的发病机制仍然难以捉摸。通常，淀粉样寡聚体被认为是纤维形成的亚稳态早期前体，它们要么处于纤维生长的途径上，要么处于纤维生长的非途径上。此外，据报道淀粉样寡聚体与晚期纤维和斑块共定位。这些早期和晚期寡聚体种类是否相同或不同，以及两者是否都与发病机制相关仍不清楚。在这里，我们报告了溶菌酶两种不同寡聚体种类的形成，它们分别在纤维生长的早期或晚期形成。我们进一步观察到，从用于毒性研究的生长条件到细胞培养基的pH变化会诱导出不同的介观沉淀物，其中两种类似于阿尔茨海默病组织学中看到的弥漫性或神经炎斑块。我们的生物物理表征表明，这两种寡聚体种类都具有被认为是淀粉样寡聚体特征的形态和染色特征。与此同时，它们的大小、形态、免疫染色、详细的染色谱，以及最显著的是它们的生物活性彼此明显不同。探究促进这两种不同寡聚体种类形成的条件表明，电荷相互作用、疏水性和单体柔韧性在指导寡聚体组装中具有不同的作用。
