Actin filament elasticity and actin-binding protein function

肌动蛋白丝弹性和肌动蛋白结合蛋白功能

• 批准号: 8470662
• 负责人: ENRIQUE M DE LA CRUZ
• 金额: $ 37.82万
• 依托单位: YALE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-15 至 2015-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8470662
• 关键词: Accounting; Actin-Binding Protein; Actins; Architecture; Area; Binding; Biochemical; Biological Process; Biopolymers; Cell physiology; Cells; Computer Simulation; Computing Methodologies; Contractile Proteins; Coupling; Cytoskeleton; Dimensions; Elasticity; Eukaryotic Cell; Evaluation; Filament; Free Energy; Funding; Growth; Individual; Knowledge; Lateral; Link; Magnetism; Measures; Mechanics; Medical; Microfilaments; Microscopic; Modeling; Molecular; Molecular Models; Molecular Motors; Motion; Motor; Myosin ATPase; Physiology; Play; Probability; Property; Proteins; Radial; Research; Research Activity; Role; Site; Source; Stress; Structure; Testing; Torque; Work; base; cell motility; cofilin; density; flexibility; genetic regulatory protein; improved; mathematical model; mechanical behavior; molecular dynamics; molecular modeling; monomer; physical model; protein function; shear stress

DESCRIPTION (provided by applicant): Actin is an essential and highly conserved cytoskeleton protein that polymerizes into helical double- stranded filaments and powers a broad range of eukaryotic cell movements. The actin regulatory protein, cofilin, severs filaments and increases the number of ends from which subunits add and dissociate. Severing is critical for rapid filament growth at the leading edge, as well as subunit turnover and network remodeling. Modulation of actin filament bending and twisting elasticity has been linked to regulatory and contractile protein function, filament assembly dynamics, and overall cell motility. A quantitative molecular description of actin filament elasticity is therefore central for developing predictive physical models of cell mechanics and actin-based motility. Research efforts in this proposal focus on indentifying the molecular origins of actin filament elasticity and the mechanical basis of filament severing by cofilin. Two general hypotheses will be tested. The first is that the double-stranded, helical structure of actin filaments gives rise to a strong coupling of twisting and bending motions that dominates the filament elastic free energy at small deformations associated with normal cellular function. The second is that twist-bend coupling causes stress to accumulate locally at regions of mechanical and topological asymmetry, such as junctions of bare and cofilin-bound segments of partially-decorated filaments, thereby increasing the severing probability at these sites. We will integrate mathematical modeling and all-atom molecular dynamics simulations with experimental manipulation of single filaments to develop predictive molecular models of actin filament mechanics and test hypotheses formulated from biochemical and biophysical analysis of cofilin-actin interactions. We will develop mesoscopic actin and cofilactin filament models that capture key features, including subunit dimensions, interaction energies, helicity and the double stranded structure. Model filaments will be strained with external mechanical (buckling or torque) loads and the emergence of twist-bend coupling be assessed from out of plane deformations. Direct twisting manipulation of individual actin filaments will test predictions of actin filament elasticity made by the computational models. Evaluation of model filaments with different architectures (e.g. number of strands and helicity) will reveal the geometric origin of twist-bend coupling. The elastic free energy and twist shear density of model filaments will be determined to evaluate how twist-bend coupling contributes to stress accumulation and severing at boundaries of bare and cofilin-decorated filament segments. The proposed activities will provide an explicit link between the microscopic properties (filament radius, monomer dimensions, buried subunit interface area, lateral or longitudinal contacts), the global mechanical behavior (bending, twisting deformation and twist-bend coupling) of filaments and the biological function (e.g. severing activity) of essential regulatory proteins. General principles regarding the relation between helical biopolymer elasticity, structure and stability will emerge from this work. 1

说明(申请人提供)：肌动蛋白是一种基本的高度保守的细胞骨架蛋白，可聚合成螺旋双链细丝，为真核细胞的广泛运动提供动力。肌动蛋白调节蛋白，cofilin，切断细丝，增加亚基添加和解离的末端数量。切断对于前缘细丝的快速生长以及亚单位的周转和网络重建是至关重要的。肌动蛋白微丝弯曲和扭转弹性的调节与调节和收缩蛋白功能、微丝组装动力学和整体细胞运动有关。因此，对肌动蛋白细丝弹性的定量分子描述对于开发细胞力学和基于肌动蛋白的运动性的预测物理模型至关重要。这项建议的研究工作集中在确定肌动蛋白细丝弹性的分子来源和粘连蛋白切断细丝的力学基础上。我们将检验两个普遍的假设。首先，肌动蛋白细丝的双链螺旋结构引起扭转和弯曲运动的强烈耦合，在与正常细胞功能相关的小变形中主导着细丝的弹性自由能。第二种是扭转-弯曲耦合导致应力在机械和拓扑不对称的区域局部积累，例如部分装饰的细丝的裸段和胶丝结合段的连接处，从而增加了这些位置的断裂概率。我们将把数学建模和全原子分子动力学模拟与单丝的实验操作结合起来，开发肌动蛋白细丝力学的预测分子模型，并验证从粘连蛋白-肌动蛋白相互作用的生化和生物物理分析得出的假说。我们将开发介观肌动蛋白和共丝蛋白细丝模型，以捕捉关键特征，包括亚单位尺寸、相互作用能量、螺旋度和双链结构。模型丝将在外部机械(屈曲或扭矩)载荷下受到应变，扭弯联轴器的出现将从平面外变形进行评估。对单个肌动蛋白细丝的直接扭转操作将检验计算模型对肌动蛋白细丝弹性的预测。对具有不同结构(如股数和螺旋度)的模型丝的评估将揭示扭弯耦合的几何起源。模型纤维的弹性自由能和扭转剪切密度将被用来评估扭转-弯曲耦合如何有助于在裸丝和胶丝装饰的纤维段的边界处应力积累和断裂。拟议的活动将在细丝的微观性质(细丝半径、单体尺寸、埋藏亚单位界面面积、横向或纵向接触)、细丝的整体力学行为(弯曲、扭转变形和扭转-弯曲耦合)和基本调节蛋白的生物功能(例如，切断活性)之间提供明确的联系。关于螺旋生物聚合物弹性、结构和稳定性之间关系的一般原理将从这项工作中产生。1