Role of Lbc GEFs in cellular morphodynamics

动态形状变化在许多细胞功能中起着核心作用。其中一个功能是细胞定向迁移到其目标部位。在这个过程中，细胞必须在空间和时间上协调动态的细胞突起和缩回以引导它们的运动。在拟议的研究中，我们的目标是研究这些动态的细胞形状变化是如何由细胞内信号网络控制的。我们将专注于Rho GT3家族的两种信号蛋白之间的相互作用，这被认为是细胞形状变化的主要调节因子：Rho家族成员Rac，刺激细胞突起，Rho，刺激细胞收缩和细胞收缩。我们将特别关注Rho GTP酶的一类特定调节剂：Lbc GEF。这些调节剂通过激活Rho刺激细胞收缩。有趣的是，一些家庭成员被Rac激活。因此，Lbc GEFs可以介导Rac/Rho活性串扰，并将细胞突起和细胞收缩的产生联系起来。这种联系可以导致细胞在定向迁移过程中利用局部突出/收缩循环来探索其环境的特性。Lbc GEFs也可以被Rho激活。通过这种机制，这些调节剂可以参与放大细胞中Rho活性的正反馈回路。这种正反馈在产生高度动态的局部细胞收缩脉冲中起着核心作用。通过产生这些收缩脉冲，细胞获得了主动的触觉，通过这种触觉，它们可以探测周围环境的机械特性。这种机械传导过程被认为在器官和组织的功能和发育中起重要作用。我们将研究每个Lbc GEF家族成员在Rac 1/Rho GTdR串扰和Rho正反馈放大中的作用，以及这些分子如何在细胞迁移和机械转导过程中对细胞形态动力学做出贡献。为了解决这些问题，我们将利用我们开发的新工具，使光遗传学或光化学扰动和监测Rho GTdR活性反应。这些方法的结合将使我们能够直接研究活细胞中Rho GTdR信号网络的时空信号处理，我们期望这些研究将揭示不同Lbc GEF家族成员的分子特性差异以及这些特性如何转化为不同的细胞功能。通过专注于定向细胞迁移和机械转导，我们期望更深入地了解细胞的两个基本功能，这些功能在许多生理和病理生理过程中起着核心作用。

Dynamic shape changes play a central role in many cellular functions. One of these functions is the directional migration of cells to their target sites. During this process, cells have to coordinate dynamic cell protrusions and retractions in space and time to steer their movements.In the proposed research, we aim to study how these dynamic cell shape changes are controlled by intracellular signal networks. We will focus on the interplay between two signal proteins of the Rho GTPase family, which are thought to be master regulators of cell shape changes: The Rho family member Rac, which stimulates cell protrusion, and Rho, which stimulates cell contraction and cell retraction. We will particularly focus on a specific class of regulators of Rho GTPases: The Lbc GEFs. These regulators stimulate cell contraction by activating Rho. Interestingly, some family members are activated by Rac. Thereby, Lbc GEFs can mediate Rac/Rho activity crosstalk and link the generation of cell protrusions and cell retractions. This link can result in local protrusion/retraction cycles that are used by cells to explore the properties of their environment during directed migration.Lbc GEFs can also get activated by Rho. Via this mechanism, these regulators can participate in a positive feedback loop that amplifies Rho activity in cells. This positive feedback plays a central role in the generation of highly dynamic local cell contraction pulses. By generating these contraction pulses, cells acquire an active sense of touch, by which they can probe the mechanical properties of their environment. This mechanotransduction process is thought to play an important role in the function and development of organs and tissues. We will study the role of each individual Lbc GEF family member in Rac1/Rho GTPase crosstalk and Rho positive feedback amplification, and how these molecules contribute to cellular morphodynamics during cell migration and mechanotransduction. To address these questions we will capitalize on new tools that we developed, that enable optogenetic or photochemical perturbations and monitoring of Rho GTPase activity responses. The combination of these approaches will allow us to directly investigate spatio-temporal signal processing in Rho GTPase signal networks in living cells.We expect that these studies will uncover differences in the molecular properties of distinct Lbc GEF family members and how these properties translate into distinct cellular functions. By focusing on directed cell migration and mechanotransduction, we expect to gain a deeper insight into two fundamental functions of cells that play a central role in many physiological and pathophysiological processes.