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: 8333339
• 负责人: ENRIQUE M DE LA CRUZ
• 金额: $ 31.53万
• 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/8333339
• 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

描述（由申请人提供）：肌动蛋白是一种重要且高度保守的细胞骨架蛋白，其聚合成螺旋双链丝并为广泛的真核细胞运动提供动力。肌动蛋白调节蛋白肌动蛋白丝切蛋白切断丝并增加亚基添加和解离的末端数量。切断对于前沿的细丝快速生长以及亚基周转和网络重塑至关重要。 肌动蛋白丝弯曲和扭曲弹性的调节与调节和收缩蛋白功能、丝组装动力学和整体细胞运动有关。因此，肌动蛋白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的预测物理模型至关重要。该提案的研究工作重点是确定肌动蛋白丝弹性的分子起源以及肌动蛋白丝切蛋白切断丝的机械基础。将测试两个一般假设。首先，肌动蛋白丝的双链螺旋结构引起扭曲和弯曲运动的强烈耦合，在与正常细胞功能相关的小变形下主导丝弹性自由能。第二个是，扭弯耦合导致应力在机械和拓扑不对称的区域局部累积，例如部分装饰的细丝的裸露部分和丝切蛋白结合部分的连接处，从而增加了这些部位的断裂概率。 我们将把数学模型和全原子分子动力学模拟与单丝的实验操作相结合，开发肌动蛋白丝力学的预测分子模型，并测试根据丝切蛋白-肌动蛋白相互作用的生化和生物物理分析得出的假设。我们将开发介观肌动蛋白和辅丝乳蛋白丝模型，以捕获关键特征，包括亚基尺寸、相互作用能、螺旋度和双链结构。模型细丝将受到外部机械（屈曲或扭矩）载荷的拉紧，并通过平面外变形来评估扭转弯曲耦合的出现。对单个肌动蛋白丝的直接扭转操作将测试计算模型对肌动蛋白丝弹性的预测。对具有不同结构（例如股数和螺旋度）的模型细丝的评估将揭示扭转弯曲耦合的几何起源。将确定模型细丝的弹性自由能和扭转剪切密度，以评估扭转弯曲耦合如何促进应力累积以及在裸露和丝丝蛋白装饰的细丝段边界处的断裂。 拟议的活动将提供细丝的微观特性（细丝半径、单体尺寸、埋藏亚基界面面积、横向或纵向接触）、整体机械行为（弯曲、扭转变形和扭转弯曲耦合）和生物必需调节蛋白的功能（例如切断活性）。这项工作将得出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则。 1