Self-organization and mechanics of actomyosin networks attached to artificial and cellular plasma membranes

附着于人造和细胞质膜的肌动球蛋白网络的自组织和机制

• 批准号: 427751228
• 负责人: Professor Dr. Andreas Janshoff
• 金额: --
• 依托单位: Institut für Physikalische Chemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/427751228?language=en
• 关键词: Self; organization; mechanics; actomyosin; networks

The cortex of animal cells is a thin, highly dynamically crosslinked actin network directly connected to the plasma membrane. Even though cortical actin plays a pivotal role in cellular mechanics and morphogenesis, only very little is known about the organization of the cortex attached to the plasma membrane, its collective dynamics, and how its dynamics affects mechanical properties that eventually generate function. A profound understanding requires to study model systems that permit control over composition and architecture of the network. The overarching goal of this project is to disentangle how network architecture, dynamic attachment to the plasma membrane, and contractility contribute to the viscoelastic properties of the cellular cortex. Convergence of the mechanical behavior of artificial cortices obtained in bottom-up approaches and natural cortices derived in a top-down approach is sought-after. Starting point of the project is a recently established minimal actin cortex (MAC), which dynamically cross-links a lipid membrane doped with the receptor lipid PtdIns(4,5)P2 with F-actin through the protein ezrin. In prior work, we quantified the organization of the F-actin network as a function of ezrin pinning sites on the membrane and related the viscoelastic properties of the F-actin/membrane composite to actin organization. Based on the established MAC, we are now in the position to elucidate the influence of the ezrin cross-linker’s dynamic nature on the F-actin architecture and its viscoelastic properties using ezrin mutants with an altered F-actin binding site. We will further address the question how F-actin cross-linkers alter the organization of the actin network on the membrane and how this influences the dynamics and rheological properties of the system. We will actively drive the actin cortex out of equilibrium by adding non-muscle myosin II motors and ATP to monitor the collective behavior in the networks and quantify the associated athermal fluctuations. In comparison to the MACs, we plan to manipulate the attachment sites of natural cell membrane fragments with preserved cortices to be able to pin down the importance of the different components for mesoscopic organization of the dynamic network. The use of both active and passive microrheology will help us to investigate the effect of athermal fluctuations on the viscoelastic properties of the cortex. Nonlinear behavior of the networks will be explored by using active microrheology with externally applied high-amplitude noise. This will permit us to address the discrepancy between rheological properties of artificial networks and the soft glassy rheology found for living cell.

动物细胞的皮层是一个薄的、高度动态交联的肌动蛋白网络，直接连接到质膜上。尽管皮质肌动蛋白在细胞力学和形态发生中起着关键作用，但人们对附着在质膜上的皮质组织、其集体动力学以及其动力学如何影响最终产生功能的机械特性知之甚少。一个深刻的理解需要研究模型系统，允许控制网络的组成和架构。这个项目的首要目标是解开网络结构，动态附着到质膜，和收缩性如何有助于细胞皮质的粘弹性。在自下而上的方法中获得的人工皮质和在自上而下的方法中获得的天然皮质的机械行为的收敛是受欢迎的。该项目的起点是最近建立的最小肌动蛋白皮质（MAC），其通过蛋白质ezrin将掺杂有受体脂质PtdIns（4，5）P2的脂质膜与F-肌动蛋白动态交联。在以前的工作中，我们量化的F-肌动蛋白网络的组织作为一个功能的埃兹林钉扎网站上的膜和相关的F-肌动蛋白/膜复合材料的粘弹性肌动蛋白组织。基于已建立的MAC，我们现在能够使用具有改变的F-肌动蛋白结合位点的ezrin突变体来阐明ezrin交联剂的动态性质对F-肌动蛋白结构及其粘弹性的影响。我们将进一步解决的问题，F-肌动蛋白交联剂如何改变组织的肌动蛋白网络的膜上，这是如何影响系统的动力学和流变学特性。我们将通过添加非肌肉肌球蛋白II马达和ATP来主动驱动肌动蛋白皮质脱离平衡，以监测网络中的集体行为并量化相关的非热波动。与MAC相比，我们计划操纵天然细胞膜片段与保存的皮质的附着位点，以便能够确定动态网络的介观组织的不同组件的重要性。使用主动和被动的微观流变学将有助于我们调查的影响，非热波动的粘弹性能的皮质。网络的非线性行为将通过使用外部施加高振幅噪声的主动微流变学来探索。这将使我们能够解决人工网络的流变特性和活细胞的软玻璃流变学之间的差异。