Molecular Biomedical Sciences Department, College of Veterinary Medicine, North Carolina State University, Raleigh, NC.
J Cell Biol. 2021 Mar 1;220(3). doi: 10.1083/jcb.202008032.
The molecular organization of cytokinesis proteins governs contractile ring function. We used single molecule localization microscopy in live cells to elucidate the molecular organization of cytokinesis proteins and relate it to the constriction rate of the contractile ring. Wild-type fission yeast cells assemble contractile rings by the coalescence of cortical proteins complexes called nodes whereas cells without Anillin/Mid1p (Δmid1) lack visible nodes yet assemble contractile rings competent for constriction from the looping of strands. We leveraged the Δmid1 contractile ring assembly mechanism to determine how two distinct molecular organizations, nodes versus strands, can yield functional contractile rings. Contrary to previous interpretations, nodes assemble in Δmid1 cells. Our results suggest that Myo2p heads condense upon interaction with actin filaments and an excess number of Myo2p heads bound to actin filaments hinders constriction thus reducing the constriction rate. Our work establishes a predictive correlation between the molecular organization of nodes and the behavior of the contractile ring.
细胞分裂蛋白的分子组织决定了收缩环的功能。我们使用活细胞中单分子定位显微镜来阐明细胞分裂蛋白的分子组织，并将其与收缩环的收缩速度联系起来。野生型裂殖酵母细胞通过称为节点的皮质蛋白复合物的凝聚组装收缩环，而没有 Anillin/Mid1p（Δmid1）的细胞没有可见的节点，但可以从环的环化组装出能够收缩的收缩环。我们利用 Δmid1 收缩环组装机制来确定两种不同的分子组织，节点与链，如何产生功能性的收缩环。与之前的解释相反，节点在Δmid1 细胞中组装。我们的结果表明，Myo2p 头部在与肌动蛋白丝相互作用时发生凝聚，并且与肌动蛋白丝结合的过量 Myo2p 头部阻碍了收缩，从而降低了收缩速度。我们的工作建立了节点的分子组织与收缩环行为之间的预测相关性。
