Positioning the Plane of Cell Division during Cytokinesis

描述(申请人提供)：成功的细胞分裂需要对细胞骨架进行精细的空间和时间控制，以便在分离的姐妹染色单体之间形成内向的分裂沟。收缩环组装发生在细胞皮质，细胞质区域与质膜并列。这一过程的主要调节者，小的GTP酶RhoA在赤道细胞皮质被激活的机制不是 很好理解。新的证据揭示了一种以前未知的抑制机制。初步结果表明，对这种抑制机制的表征将为了解交换因素如何促进RhoA激活提供见解。这些结果和来自不同系统的证据表明，质膜靶向鸟核苷酸交换因子是激活GTP酶途径的关键步骤，一旦激活，GTP酶的主要功能是将效应物招募到合适的膜环境中。这一假说将在细胞质分裂的背景下使用最近开发的光遗传工具进行直接测试，这些工具可以利用光来控制活细胞中的蛋白质定位和功能。最后，将进行实验以揭示一种新的含有GYF结构域的蛋白的分子功能，该蛋白调节依赖于RhoA的皮质收缩能力。

DESCRIPTION (provided by applicant): Successful cell division requires exquisite spatial and temporal control of the cytoskeleton such that the ingressing cleavage furrow forms between the separating sisters chromatids. Contractile ring assembly occurs in the cell cortex, the cytoplasmic region juxtaposed to the plasma membrane. The mechanism by which the master regulator of this process, the small GTPase RhoA, is activated at the equatorial cell cortex is not well understood. New evidence has been obtained that reveals a previously unidentified inhibitory mechanism. Preliminary results suggest that characterization of this inhibitory mechanism will provide insights into how exchange factors promote RhoA activation. These results and evidence from a variety of systems suggest a hypothesis in which plasma membrane targeting of guanine nucleotide exchange factors is a key step in activating GTPase pathways and that, once active, the primary function that GTPases serve is to recruit effectors to the appropriate membrane environment. This hypothesis will be directly tested in the context of cytokinesis using recently developed optogenetic tools that affords control of protein localization and function in living cells using light. Lastly, experiments will be performed to uncover the molecular function of a novel GYF-domain containing protein that regulates RhoA-dependent cortical contractility.