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

描述（由申请人提供）：肌动蛋白是一种必需且高度保守的细胞骨架蛋白，其聚合成螺旋双链细丝并为广泛的真核细胞运动提供动力。肌动蛋白调节蛋白，cofilin，切断丝，并增加亚基添加和解离的末端数量。切断对于前沿的快速细丝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质功能、丝组装动力学和整体细胞运动性有关。因此，肌动蛋白丝弹性的定量分子描述是开发细胞力学和肌动蛋白为基础的运动预测物理模型的核心。在这个建议的研究工作集中在确定肌动蛋白丝弹性的分子起源和丝切割的机械基础的cofilin。将检验两个一般假设。第一个是，双链，螺旋结构的肌动蛋白丝产生强耦合的扭曲和弯曲运动，占主导地位的细丝弹性自由能在小变形与正常的细胞功能。第二个是，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，例如部分装饰的长丝的裸露和cofilin结合片段的接合处，从而增加在这些位点处的切断概率。 我们将整合数学建模和全原子分子动力学模拟与实验操作的单丝，开发预测的肌动蛋白丝力学和测试假设制定从cofilin-actin相互作用的生化和生物物理分析的分子模型。我们将开发介观肌动蛋白和cofilactin细丝模型，捕捉关键功能，包括亚基尺寸，相互作用能，螺旋度和双链结构。模型细丝将在外部机械（屈曲或扭矩）载荷下发生应变，并从平面外变形中评估扭曲-弯曲耦合的出现。单个肌动蛋白丝的直接扭转操作将测试由计算模型做出的肌动蛋白丝弹性的预测。对具有不同结构（例如股线数和螺旋度）的模型细丝的评估将揭示扭曲-弯曲耦合的几何起源。将确定模型长丝的弹性自由能和扭转剪切密度，以评估扭转-弯曲耦合如何有助于应力积累和在裸露和cofilin装饰的长丝片段的边界处切断。 拟议的活动将提供一个明确的联系之间的微观性质（细丝半径，单体尺寸，掩埋的亚基界面面积，横向或纵向接触），全球机械行为（弯曲，扭曲变形和扭曲弯曲耦合）的细丝和生物功能（如切断活性）的基本调控蛋白。螺旋生物聚合物的弹性，结构和稳定性之间的关系的一般原则将出现从这项工作。1