Bursac Predrag, Lenormand Guillaume, Fabry Ben, Oliver Madavi, Weitz David A, Viasnoff Virgile, Butler James P, Fredberg Jeffrey J
Physiology Program, School of Public Health, Harvard University, Boston, Massachusetts 02115, USA.
Nat Mater. 2005 Jul;4(7):557-61. doi: 10.1038/nmat1404. Epub 2005 Jun 5.
The cytoskeleton (CSK) is a crowded network of structural proteins that stabilizes cell shape and drives cell motions. Recent studies on the dynamics of the CSK have established that a wide variety of cell types exhibit rheology in which responses are not tied to any particular relaxation times and are thus scale-free. Scale-free rheology is often found in a class of materials called soft glasses, but not all materials expressing scale-free rheology are glassy (see plastics, wood, concrete or some metals for example). As such, the extent to which dynamics of the CSK might be regarded as glassy remained an open question. Here we report both forced and spontaneous motions of microbeads tightly bound to the CSK of human muscle cells. Large oscillatory shear fluidized the CSK matrix, which was followed by slow scale-free recovery of rheological properties (aging). Spontaneous bead motions were subdiffusive at short times but superdiffusive at longer times; intermittent motions reflecting nanoscale CSK rearrangements depended on both the approach to kinetic arrest and energy release due to ATP hydrolysis. Aging, intermittency, and approach to kinetic arrest establish a striking analogy between the behaviour of the living CSK and that of inert non-equilibrium systems, including soft glasses, but with important differences that are highly ATP-dependent. These mesoscale dynamics link integrative CSK functions to underlying molecular events, and represent an important intersection of topical issues in condensed matter physics and systems biology.
细胞骨架（CSK）是由结构蛋白构成的密集网络，可稳定细胞形状并驱动细胞运动。近期关于CSK动力学的研究表明，多种细胞类型都表现出流变学特性，其响应与任何特定的弛豫时间无关，因此是无标度的。无标度流变学常见于一类称为软玻璃的材料中，但并非所有表现出无标度流变学的材料都是玻璃态的（例如可参见塑料、木材、混凝土或某些金属）。因此，CSK动力学在多大程度上可被视为玻璃态仍是一个悬而未决的问题。在此，我们报告了紧密结合于人肌肉细胞CSK的微珠的受迫运动和自发运动。大振幅振荡剪切使CSK基质流化，随后流变特性缓慢地进行无标度恢复（老化）。自发的微珠运动在短时间内是亚扩散的，但在较长时间内是超扩散的；反映纳米级CSK重排的间歇性运动既取决于接近动力学停滞的程度，也取决于ATP水解导致的能量释放。老化、间歇性以及接近动力学停滞在有生命的CSK行为与包括软玻璃在内的惰性非平衡系统行为之间建立了惊人的类比，但也存在高度依赖ATP的重要差异。这些中尺度动力学将CSK的综合功能与潜在的分子事件联系起来，代表了凝聚态物理和系统生物学中热门问题的一个重要交叉点。
