摘要
Membrane-less organelles resulting from liquid–liquid phase separation of biopolymers into intracellular condensates control essential biological functions, including messenger RNA processing, cell signalling and embryogenesis1,2,3,4. It has recently been discovered that several such protein condensates can undergo a further irreversible phase transition, forming solid nanoscale aggregates associated with neurodegenerative disease5,6,7. While the irreversible gelation of protein condensates is generally related to malfunction and disease, one case where the liquid-to-solid transition of protein condensates is functional, however, is that of silk spinning8,9. The formation of silk fibrils is largely driven by shear, yet it is not known what factors control the pathological gelation of functional condensates. Here we demonstrate that four proteins and one peptide system, with no function associated with fibre formation, have a strong propensity to undergo a liquid-to-solid transition when exposed to even low levels of mechanical shear once present in their liquid–liquid phase separated form. Using microfluidics to control the application of shear, we generated fibres from single-protein condensates and characterized their structural and material properties as a function of shear stress. Our results reveal generic backbone–backbone hydrogen bonding constraints as a determining factor in governing this transition. These observations suggest that shear can play an important role in the irreversible liquid-to-solid transition of protein condensates, shed light on the role of physical factors in driving this transition in protein aggregation-related diseases and open a new route towards artificial shear responsive biomaterials.
摘要译文
生物聚合物液-液相分离成细胞内缩合物产生的膜少细胞器控制基本的生物学功能，包括信使RNA加工，细胞信号传导和胚胎发生 1,2,3,4 。最近发现，几种这样的蛋白质缩合物可以经历进一步的不可逆相变，形成与神经退行性疾病相关的固体纳米级聚集体 5,6,7 。虽然蛋白质凝结物的不可逆凝胶化通常与故障和疾病有关，但是一种情况下，蛋白质凝结物的液-固转变是起作用的，而丝绸纺丝 8,9 的情况。丝原纤维的形成很大程度上受剪切力的驱动，但是尚不清楚什么因素控制功能性缩合物的病理胶凝。在这里，我们证明了四种蛋白质和一种肽系统，与纤维的形成没有任何关系，一旦以液相-液相分离的方式经受低水平的机械剪切，它们就有很强的经历从液相到固相的趋势形成。使用微流体控制剪切的应用，我们从单一蛋白质的冷凝物中产生了纤维，并根据剪切应力对它们的结构和材料特性进行了表征。我们的结果表明，通用的骨架-主链氢键约束是控制这种过渡的决定性因素。这些观察结果表明，剪切作用在不可逆的蛋白质凝结物从液态到固态的转变中起着重要作用，阐明了物理因素在推动蛋白质聚集性相关疾病转变中的作用，并开辟了一条新的途径来实现人工剪切响应生物材料。
Yi Shen;Francesco Simone Ruggeri;Daniele Vigolo;Ayaka Kamada;Seema Qamar;Aviad Levin;Christiane Iserman;Simon Alberti;Peter St George-Hyslop;Tuomas P. J. Knowles. Biomolecular condensates undergo a generic shear-mediated liquid-to-solid transition[J]. Nature Nanotechnology, 2020,15(10): 841-847