Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA.
Biophys J. 2010 Nov 3;99(9):2748-56. doi: 10.1016/j.bpj.2010.09.023.
Keratin intermediate filaments (IFs) fulfill an important function of structural support in epithelial cells. The necessary mechanical attributes require that IFs be organized into a crosslinked network and accordingly, keratin IFs are typically organized into large bundles in surface epithelia. For IFs comprised of keratins 5 and 14 (K5, K14), found in basal keratinocytes of epidermis, bundling can be self-driven through interactions between K14's carboxy-terminal tail domain and two regions in the central α-helical rod domain of K5. Here, we exploit theoretical principles and computational modeling to investigate how such cis-acting determinants best promote IF crosslinking. We develop a simple model where keratin IFs are treated as rigid rods to apply Brownian dynamics simulation. Our findings suggest that long-range interactions between IFs are required to initiate the formation of bundlelike configurations, while tail domain-mediated binding events act to stabilize them. Our model explains the differences observed in the mechanical properties of wild-type versus disease-causing, defective IF networks. This effort extends the notion that the structural support function of keratin IFs necessitates a combination of intrinsic and extrinsic determinants, and makes specific predictions about the mechanisms involved in the formation of crosslinked keratin networks in vivo.
角蛋白中间丝（IFs）在上皮细胞中发挥着重要的结构支撑功能。必要的机械属性要求 IF 形成交联网络，因此，角蛋白 IF 通常在表面上皮组织中组织成大束。对于表皮基底层角质细胞中存在的角蛋白 5 和 14（K5、K14）组成的 IF 来说，通过 K14 的羧基末端尾部结构域与 K5 的中央α螺旋杆域中的两个区域之间的相互作用，可以实现自发束状聚集。在这里，我们利用理论原理和计算建模来研究这些顺式作用决定因素如何最好地促进 IF 交联。我们开发了一个简单的模型，将角蛋白 IF 视为刚性棒，以应用布朗动力学模拟。我们的研究结果表明，需要 IF 之间的长程相互作用来启动束状结构的形成，而尾部结构域介导的结合事件则起到稳定作用。我们的模型解释了野生型和致病、有缺陷的 IF 网络在机械性能上的差异。这一研究扩展了角蛋白 IF 的结构支撑功能需要内在和外在决定因素相结合的观点，并对体内交联角蛋白网络形成所涉及的机制提出了具体预测。
