Informational flow from mechanosensing to signaling for extracellular matrix stiffness sensing

项目摘要 组织硬度在发育、衰老和疾病过程中发生变化。细胞感知到这种硬度， 分化、增殖、迁移和存活，这些都对发育和组织 再生局部组织硬化是癌症的一个标志，癌细胞对其的感知导致进一步的 肿瘤进展和转移。因此，了解刚度传感机制对于设计 针对发育障碍和癌症的适当治疗策略。一个突出的组织传感器 硬度是位于细胞和环境之间的分子复合物，称为粘着斑。 刚度感测的第一步涉及在焦点中的分子之间传递增加水平的力。 对较高组织硬度的粘附。从持续的资助中，我们发现这种差异力 传输不依赖于肌球蛋白收缩性，肌球蛋白收缩性是细胞骨架内的主要力发生器， 依赖于肌动蛋白的聚合，并由其成核剂通过对细胞产生反向流动来辅助 膜的剩下的问题是如何响应于组织硬度的这种差动力可以是 翻译成不同的信号，最终调节细胞的发育功能。该提案的目的是 为了理解关键的基于粘着的信号传导是否是由关键结构的感知活动引起的， 传感器蛋白质和通过它的力量。为了实现这一目标，我们已经开发了一套实验， 微观、计算和统计框架，使我们能够得出因果关系的结论 在从活细胞成像捕获的单个粘着灶处的两个时间依赖性信号之间， 计算机视觉具体来说，我们专注于黏着斑激酶（FAK），这是一个信号枢纽，为局灶性 基于粘附的信号传导，但其与机械传感器talin的偶联并不为人所知。塔林可以是 在外力作用下被拉伸，暴露出与其他分子结合的位点，如粘着斑蛋白，另一种机械连接物 蛋白这一更新提案的总体目标是利用这些多学科管道来测试一种新的 刚度感知的概念模型，其中刚度依赖性FAK激活由塔林氏 机械感测和差动力以取决于焦点粘连的动态状态的方式进行。 我们将确定1）FAK募集和激活是否由talin募集和机械敏感性引起， 2)如果FAK激活是由机械力引起的，3）FAK激活如何促进RhoA信号传导， 刚度检测增强对这些过程的机械理解将增加我们的基础知识。 细胞如何感知和响应组织力学的知识。因此，拟议的研究与 NIH的使命，因为他们将导致生理学和病理生理学，包括组织发育的新见解， 再生和癌症进展。

Project Summary Tissue stiffness changes during development, aging and diseases. Sensing this stiffness by cells determines differentiation, proliferation, migration, and survival, which are all important for development and tissue regeneration. Local tissue stiffening is a hallmark of cancer, sensing of which by cancer cells causes further tumor progression and metastasis. Understanding stiffness sensing mechanism is thus essential for designing appropriate treatment strategy against developmental disorders and cancer. A prominent sensor for the tissue stiffness is a molecular complex located between the cell and the environment, referred to as a focal adhesion. The first step in stiffness sensing involves transmission of increased level of a force across molecules in the focal adhesion against higher tissue stiffness. From the on-going funding, we discovered that this differential force transmission is independent of myosin contractility, the main force generator within cytoskeleton, and strongly depends on actin polymerization assisted by its nucleators by creating a backward flow against the cell membrane. The remaining question is how this differential force in response to the tissue stiffness can be translated to different signals that ultimately regulate cells’ developmental functions. The goal of the proposal is to understand whether a key focal adhesion-based signaling is caused by sensing activity of a key structural sensor protein and the force running through it. To achieve this goal, we have developed a set of experimental, microscopic, computational, and statistical frameworks that allow us to draw a conclusion about causality between the two time-dependent signals at individual focal adhesions captured from a live-cell imaging and computer vision. Specifically, we focus on focal adhesion kinase (FAK), which is a signaling hub for focal adhesion-based signaling but not well known for its coupling to the mechanical sensor, talin. Talin can be stretched under force and expose binding sites for other molecules like a vinculin, another mechanical linker protein. The overall objective of this renewal proposal is to use these multi-disciplinary pipelines to test a novel conceptual model of stiffness sensing in which the stiffness-dependent FAK activation is induced by talin’s mechanical sensing and the differential force in a manner that is dependent on focal adhesions’ dynamic state. We will determine 1) if FAK recruitment and activation are caused by talin recruitment and mechanosensitivity, 2) if FAK activation is caused by the mechanical force, 3) how FAK activation promotes RhoA signaling for stiffness sensing. An enhanced mechanistic understanding of these processes would increase our fundamental knowledge of how cells sense and respond to tissue mechanics. Thus, the proposed studies are relevant to the NIH's mission, as they will lead to new insights in physiology and pathophysiology including tissue development, regeneration and cancer progression.