Modeling Contractile Ring Constriction in Fission Yeast

 描述(申请人提供)：细胞质分裂是细胞周期的最后阶段，当细胞质分裂成两部分时。适当的时间和位置的分裂对于细胞分裂产生两个正常的子细胞是至关重要的。在动物、真菌和阿米巴细胞中，胞质分裂涉及肌动蛋白收缩环的收缩。裂殖酵母的收缩环特别适合于定量建模，因为环蛋白具有特别好的特性。然而，产生环张力和收缩环的机制还不是很清楚。从第一个支持阶段开始，我们已经开发了一个用于裂解酵母收缩环的工作计算机模拟框架，第一个实验测量环张力的工作方法，以及伴随着环收缩的分离过程的模型。这项拟议研究的第一个目标是建立一个完全动态的3D模拟来捕捉环的超微结构。我们将实现分裂酵母环中两种肌球蛋白-II亚型Myo2和Myp2的详细组织，以及肌动蛋白、肌动蛋白核仁形成蛋白、肌动蛋白交联剂和其他关键成分。模拟将通过计算环张力和部件运动来测试假设的组织，以便直接与实验值进行比较。每个组织都将接受结构不稳定性测试，特别是在模拟环蛋白质突变的环中。这个 模型还将模拟在酵母原生质体、细胞中滑动的环中详细的组件运动 其墙壁已被移除，以与实验成像的滑环进行比较。第二个目标是建立一个完整的裂解酵母环收缩和分离模型。在耦合模拟方案中，隔膜形状决定了环所连接的演化表面，而时空变化的环张力反馈到隔膜生长。将综合模型的张力、组织稳定性、隔膜形态等输出与实验进行比较。第三个目标是模拟分离的分裂酵母细胞动环的行为，就像在使用渗透性酵母原生质体的实验中所研究的那样。在这些情况下，正常的成分周转被阻止，因为新的成分不结合环，并且环经常从质膜上部分脱离。因此，环在这些条件下的行为探索了翻转和锚定在环的张力产生和收缩机制中的作用。环模拟将在没有组件绑定和部分锚定的环的情况下运行，并与实验进行比较。

 DESCRIPTION (provided by applicant): Cytokinesis is the final stage of the cell cycle when the cytoplasm is cleaved into two parts. Proper timing and location of the cleavage is essential for cell division to result in two normal daughter cells. In animal, fungal and amoeboid cells cytokinesis involves constriction of an actomyosin contractile ring. The contractile ring of fissio yeast Schizosaccharomyces pombe is particularly amenable to quantitative modeling, as the ring proteins are particularly well characterized. However the mechanisms that generate ring tension and constrict the ring are not well understood. From the first period of support, we have developed a working computer simulation framework for the fission yeast contractile ring, the first working method to measure ring tension experimentally, and a model of the septation process that accompanies ring constriction. The first Aim of the proposed research is to build a fully dynamic 3D simulation to capture the ultrastructure of the ring. We will implement detailed organizations of the two myosin-II isoforms in the fission yeast ring, Myo2 and Myp2, together with actin, the actin nucleator formin, actin crosslinkers and other key components. The simulations will test hypothesized organizations by calculating ring tension and component motions for direct comparison with experimental values. Each organization will be tested for structural instabilities, particularly in simulations of rings with mutations in ring proteins. The model will also simulate detailed component motions in rings that slide in yeast protoplasts, cells whose walls have been removed, for comparison with experimentally imaged sliding rings. The second Aim is to develop an integrated model of fission yeast ring constriction and septation. In the coupled simulation scheme the septum shape dictates to the ring the evolving surface to which it is attached, while spatiotemporally varying ring tension feeds back to septum growth. Tensions, organizational stability, septum morphology and other outputs of the integrated model will be compared to experiment. The third Aim is to model the behavior of isolated fission yeast cytokinetic rings, as studied in experiments using permeabilized yeast protoplasts. In these circumstances normal component turnover is blocked, as new components do not bind the ring, and rings often become partially unanchored from the plasma membrane. As a result, the behavior of rings in these conditions probes the role of turnover and anchoring in the mechanisms of tension production and constriction of the ring. The ring simulations will be run without component binding, and with partially anchored rings, and the behavior compared to experiments.