Department of Biological Sciences, Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
Gunma University Initiative for Advanced Research (GIAR), Gunma University, Maebashi, Gunma, Japan; Institute for Molecular and Cellular Regulation (IMCR), Gunma University, Maebashi, Gunma, Japan.
Biochem Biophys Res Commun. 2021 Jan 1;534:1026-1032. doi: 10.1016/j.bbrc.2020.10.043. Epub 2020 Oct 29.
Cytokinesis is the final step in cell division and is driven by the constriction of the medial actomyosin-based contractile ring (CR) in many eukaryotic cells. In the fission yeast Schizosaccharomyces pombe, the IQGAP-like protein Rng2 is required for assembly and constriction of the CR, and specifically interacts with actin filaments (F-actin) in the CR after anaphase. However, the mechanism that timely activates Rng2 has not yet been elucidated. We herein tested the hypothesis that the cytokinetic function of Rng2 is regulated by phosphorylation by examining phenotypes of a series of non-phosphorylatable and phosphomimetic rng2 mutant strains. In phosphomimetic mutant cells, F-actin in the CR was unstable. Genetic analyses indicated that phosphorylated Rng2 was involved in CR assembly in cooperation with myosin-II, whereas the phosphomimetic mutation attenuated the localization of Rng2 to CR F-actin. The present results suggest that Rng2 is phosphorylated during CR assembly and then dephosphorylated, which enhances the interaction between Rng2 and CR F-actin to stabilize the ring, thereby ensuring secure cytokinesis.
有丝分裂是细胞分裂的最后一步，在许多真核细胞中，由中侧肌动球蛋白收缩环（CR）的收缩驱动。在裂殖酵母 Schizosaccharomyces pombe 中，IQGAP 样蛋白 Rng2 是 CR 组装和收缩所必需的，并且在后期与 CR 中的肌动蛋白丝（F-actin）特异性相互作用。然而，尚未阐明及时激活 Rng2 的机制。我们在此通过检查一系列不可磷酸化和磷酸模拟 rng2 突变株的表型来检验 Rng2 的细胞分裂功能受磷酸化调节的假设。在磷酸模拟突变细胞中，CR 中的 F-actin 不稳定。遗传分析表明，磷酸化的 Rng2 与肌球蛋白-II 一起参与 CR 组装，而磷酸模拟突变削弱了 Rng2 向 CR F-actin 的定位。本研究结果表明，Rng2 在 CR 组装过程中发生磷酸化，然后去磷酸化，这增强了 Rng2 与 CR F-actin 之间的相互作用，从而稳定环，确保安全的细胞分裂。
