Sivaramakrishnan Sivaraj, DeGiulio James V, Lorand Laszlo, Goldman Robert D, Ridge Karen M
Department of Biomedical Engineering, Northwestern University, 2145 North Sheridan Road, Evanston, IL 60208, USA.
Proc Natl Acad Sci U S A. 2008 Jan 22;105(3):889-94. doi: 10.1073/pnas.0710728105. Epub 2008 Jan 16.
Keratin intermediate filaments (KIFs) form cytoskeletal KIF networks that are essential for the structural integrity of epithelial cells. However, the mechanical properties of the in situ network have not been defined. Particle-tracking microrheology (PTM) was used to obtain the micromechanical properties of the KIF network in alveolar epithelial cells (AECs), independent of other cytoskeletal components, such as microtubules and microfilaments. The storage modulus (G') at 1 Hz of the KIF network decreases from the perinuclear region (335 dyn/cm(2)) to the cell periphery (95 dyn/cm(2)), yielding a mean value of 210 dyn/cm(2). These changes in G' are inversely proportional to the mesh size of the network, which increases approximately 10-fold from the perinuclear region (0.02 microm(2)) to the cell periphery (0.3 microm(2)). Shear stress (15 dyn/cm(2) for 4 h) applied across the surface of AECs induces a more uniform distribution of KIF, with the mesh size of the network ranging from 0.02 microm(2) near the nucleus to only 0.04 microm(2) at the cell periphery. This amounts to a 40% increase in the mean G'. The storage modulus of the KIF network in the perinuclear region accurately predicts the shear-induced deflection of the cell nucleus to be 0.87 +/- 0.03 microm. The high storage modulus of the KIF network, coupled with its solid-like rheological behavior, supports the role of KIF as an intracellular structural scaffold that helps epithelial cells to withstand external mechanical forces.
角蛋白中间丝（KIFs）形成细胞骨架KIF网络，这对于上皮细胞的结构完整性至关重要。然而，原位网络的力学性能尚未明确。颗粒追踪微流变学（PTM）被用于获取肺泡上皮细胞（AECs）中KIF网络的微观力学性能，独立于其他细胞骨架成分，如微管和微丝。KIF网络在1Hz时的储能模量（G'）从核周区域（335达因/平方厘米）降至细胞周边（95达因/平方厘米），平均值为210达因/平方厘米。G'的这些变化与网络的网格大小成反比，网格大小从核周区域（0.02微米²）到细胞周边（0.3微米²）大约增加10倍。施加在AECs表面的剪切应力（15达因/平方厘米，持续4小时）诱导KIF分布更均匀，网络的网格大小从细胞核附近的0.02微米²到细胞周边仅为0.04微米²。这相当于平均G'增加40%。核周区域KIF网络的储能模量准确预测细胞核的剪切诱导偏转量为0.87±0.03微米。KIF网络的高储能模量及其类似固体的流变行为，支持了KIF作为细胞内结构支架的作用，有助于上皮细胞抵御外部机械力。
