Predictive multi-scale model of focal adhesion-based durotaxis

项目摘要 该方案的最终目标是建立预测性多尺度数学模型， 硬脊膜扩张的机制趋硬性是细胞向更硬的细胞外基质（ECM）迁移的偏好，并且具有 在从胚胎发育到肿瘤转移的许多生物学过程中起重要作用。粘着斑（FA） 是硬旋转的功能单位，它是一种基于整合素的多蛋白跨膜连接，细胞通过它产生肌动蛋白 基于ECM的牵引力来牵引ECM并感测刚度。尽管与生物医学的高度相关性 在应用中，FA如何介导ECM刚度的机械感测并在很大程度上驱动硬旋转， 因为预测性的数学模型落后于该领域的描述性实验发现。在单FA水平， 虽然以前的模型解释了FA机械传感中的分子离合器行为，但它们不能解释FA是如何以及为什么发生的。 局部蛋白质活动通过独特的时空模式（类似于足迹）适应环境， 被证明是硬脊膜扩张的关键。FA局部化“足迹”的全部潜在机制及其确切的 因此，在硬脊膜扩张中的作用是未知的。此外，硬旋转必须协调细胞体和突出/回缩的运动 细胞边缘。当FA介导的牵引力驱动细胞体时，FA定位的机械感知事件如何协调 与小区边缘的动态是未知的。最后，在单细胞水平上，不同发育阶段存在着多个脂肪酸 立即使尚不清楚细胞如何整合单个FA的机械感应活动以驱动硬旋转。 一个有意义地与实验相结合的预测模型是可取的，并且可能掌握着破译的关键。 硬脊膜扩张为了实现这一目标，我们已经并将在迭代对话中独特地整合数学建模， 实验测试中心假设是：牵引力产生的FA局部时空动力学， 传输定义了FA介导的机械感测和硬旋转。这一建议的基础是我们以前的调查结果。我们 建立了第一个数学模型，捕捉整个FA成熟过程的本质。也就是说，FA是从 新生复合体，向心生长的FA，将分支肌动蛋白网络的逆行流耦合到成熟的肌动蛋白网络。 FA将应力纤维（SF）介导的收缩传递到ECM上。该模型唯一地将FA局部化精细 蛋白质活动的特征-从FA成熟过程出现-FA机械传感事件。该模型预测 并且通过实验证实，FA接合SF的伸长和收缩之间存在负反馈， 是FA局部牵引振荡和ECM刚度的机械感测的基础。根据这些发现，我们 具体目标是确定：1）FA力传递和SF伸长如何在FA机械感测中串扰; 2）如何 FA机械感觉影响细胞边缘突出/缩回，以及3）细胞如何整合单个FA的机械感觉 来驱动硬脊膜扩张如果成功，拟议的研究将提供一个定量平台，解释数据和指导 durotaxis实验设计，它具有多尺度分辨率，从FA局部动力学，细胞边缘 突出/回缩，到全细胞水平的细胞运动。

Project Summary The over-arching goal of this proposal is to establish the predictive multi-scale mathematical model to decipher the mechanism of durotaxis. Durotaxis is the preference of cells migrating toward a stiffer extracellular matrix (ECM) and has important roles in many biological processes, ranging from embryo development to tumor metastasis. Focal adhesion (FA) is the functional unit of durotaxis; it an integrin-based multi-protein transmembrane linkage, through which cell exerts actin cytoskeleton-based traction force to tug the ECM and sense the stiffness. Despite the high relevance to biomedical applications, it is not well understood how FA mediates mechanosensing of ECM stiffness and drives durotaxis, largely because predictive mathematical models lag behind the descriptive experimental finding in the field. At single-FA level, while previous models explain molecular-clutch behaviors in FA mechanosensing, they cannot explain how and why FA- localized protein activities adapt to environments by distinctive spatial-temporal patterns (akin to footprints) that are demonstrated to be essential for durotaxis. The full underlying mechanisms of the FA-localized “footprint” and its exact roles in durotaxis are thus unknown. Further, durotaxis must coordinate movements of cell body and protrusion/retraction of cell edge. While the FA-mediated tractions drive the cell body, how the FA-localized mechanosensing events coordinate with the cell edge dynamics is unknown. Last, at a single-cell level, there exist many FAs at different developmental stages at any time. It is not understood how the cell integrates the mechanosensing activities of individual FAs to drive durotaxis. A predictive model that meaningfully engages with experiments is desirable and likely holds the key to decipher durotaxis. Toward this goal, we have been and will uniquely integrate mathematical modeling in iterative dialogues with experimental testing. The central hypothesis is: FA-localized spatial-temporal dynamics of the traction force generation and transmission defines FA-mediated mechanosensing and durotaxis. The basis of this proposal is our previous findings. We built the first mathematical model that captures the essence of entire FA maturation process. That is, FA evolves from a nascent complex, the centripetally growing FA that couples the retrograde flux of branching actin network, to the mature FA that transmits the stress fiber (SF)-mediated contractions onto ECM. This model uniquely links the FA-localized fine features of protein activities – emerging from FA maturation process – to FA mechanosensing events. The model predicted and was experimentally confirmed that a negative feedback between the elongation and contractility of the FA-engaging SF underlies the FA-localized traction oscillation and mechanosensing of ECM stiffness. Ushered by these findings, our specific aims are to determine: 1) how FA force-transmission and SF elongation cross-talk in FA mechanosensing; 2) how FA mechanosensing affects cell edge protrusion/retraction, and 3) how cell integrates mechanosensation of individual FAs to drive durotaxis. If successful, the proposed research would provide a quantitative platform interpret data and guide durotaxis experimental designs, which has the multi-scale resolutions ranging from FA-localized dynamics, cell edge protrusion/retraction, to cell movement at whole-cell level.