Chemical and Physical Control of Ectopic Contractile Rings

生命系统最令人着迷和最重要的特性之一是它们应对物理损伤的能力。这一特性在单细胞和多细胞系统中都很明显，而且不仅在许多不同的动物门中广泛保守，在植物中也是如此。由于其明显的临床重要性，多细胞伤口愈合长期以来一直是人们密切关注的主题。相比之下，单细胞质膜损伤的修复直到最近才被忽视。至少有两种机制已被描述：一种是极快的膜融合事件，它立即阻止离子的涌入，否则离子就会杀死细胞；另一种是较慢的收缩反应，即由肌动蛋白细丝和肌球蛋白-2组成的环状环聚集在伤口周围，然后关闭。这个项目的主要目标是描述调节这种异位收缩环的组装和闭合的机制。以非洲爪哇卵母细胞为模型系统，将采用物理、显微和基于DNA的重组方法相结合的方法来测试细胞张力、Rho类GTPase活性的局部增加和细胞内游离钙在肌动蛋白细丝和肌球蛋白-2向伤口边缘募集过程中的关系。除了提供与修复质膜损伤的基本生物学过程直接相关的信息外，拟议的研究还有可能为类似于异位收缩环组装和关闭的过程提供见解，如动物细胞胞质分裂。

One of the most fascinating and important properties of living systems is their ability to cope with physical damage. This property is manifest in both single cells and multicellular systems, and is broadly conserved not only in a number of different animal phyla, but in plants as well. Because of its obvious clinical importance, multicellular wound healing has long been the subject of intense scrutiny. In contrast, repair of plasma membrane wounds in single cells has been overlooked until relatively recently. At least two mechanisms have been described: an extremely rapid membrane fusion event that provides an immediate block to the inrush of ions that would otherwise kill the cell, and a slower contractile response in which a circumferential ring of actin filaments and myosin-2 assembles around the wound and then closes. The primary goal of this project is to characterize the mechanisms that regulate assembly and closure of this ectopic contractile ring. Using Xenopus oocytes as a model system, a combination of physical, microscopic, and recombinant DNA-based approaches will be employed to test relationships between cell tension, local increases in rho class GTPase activity, and intracellular free calcium, in the recruitment of actin filaments and myosin-2 to the wound border. In addition to providing information directly relevant to the basic biological process of repair of damage to the plasma membrane, the proposed studies have the potential to provide insights into processes which resemble ectopic contractile ring assembly and closure, such as animal cell cytokinesis.