Thiyagarajan Sathish, Wang Shuyuan, O'Shaughnessy Ben
Department of Physics, Columbia University, New York, NY 10027.
Department of Chemical Engineering, Columbia University, New York, NY 10027
Mol Biol Cell. 2017 Nov 7;28(23):3286-3297. doi: 10.1091/mbc.E17-06-0386. Epub 2017 Sep 27.
During cytokinesis, a contractile actomyosin ring constricts and divides the cell in two. How the ring marshals actomyosin forces to generate tension is not settled. Recently, a superresolution microscopy study of the fission yeast ring revealed that myosins and formins that nucleate actin filaments colocalize in plasma membrane-anchored complexes called nodes in the constricting ring. The nodes move bidirectionally around the ring. Here we construct and analyze a coarse-grained mathematical model of the fission yeast ring to explore essential consequences of the recently discovered ring ultrastructure. The model reproduces experimentally measured values of ring tension, explains why nodes move bidirectionally, and shows that tension is generated by myosin pulling on barbed-end-anchored actin filaments in a stochastic sliding-filament mechanism. This mechanism is not based on an ordered sarcomeric organization. We show that the ring is vulnerable to intrinsic contractile instabilities, and protection from these instabilities and organizational homeostasis require both component turnover and anchoring of components to the plasma membrane.
在胞质分裂过程中，一个收缩性的肌动球蛋白环会收缩并将细胞一分为二。该环如何组织肌动球蛋白产生张力仍未明确。最近，一项对裂殖酵母环的超分辨率显微镜研究表明，成核肌动蛋白丝的肌球蛋白和formin蛋白在收缩环中被称为节点的质膜锚定复合物中共定位。这些节点在环周围双向移动。在此，我们构建并分析了一个裂殖酵母环的粗粒度数学模型，以探索最近发现的环超微结构的重要影响。该模型再现了实验测量的环张力值，解释了节点双向移动的原因，并表明张力是由肌球蛋白以随机滑动丝机制拉动带刺端锚定的肌动蛋白丝产生的。这种机制并非基于有序的肌节组织。我们表明，该环容易受到内在收缩不稳定性的影响，而防止这些不稳定性和组织稳态需要成分周转以及成分与质膜的锚定。
