Shen Kuo-Fang, Osmani Aysha H, Govindaraghavan Meera, Osmani Stephen A
Department of Molecular Genetics and Molecular, Cellular and Developmental Biology Program, Ohio State University, Columbus, OH 43210.
Mol Biol Cell. 2014 Mar;25(6):763-75. doi: 10.1091/mbc.E13-12-0718. Epub 2014 Jan 22.
Intercellular bridges are a conserved feature of multicellular organisms. In multicellular fungi, cells are connected directly via intercellular bridges called septal pores. Using Aspergillus nidulans, we demonstrate for the first time that septal pores are regulated to be opened during interphase but closed during mitosis. Septal pore-associated proteins display dynamic cell cycle-regulated locations at mature septa. Of importance, the mitotic NIMA kinase locates to forming septa and surprisingly then remains at septa throughout interphase. However, during mitosis, when NIMA transiently locates to nuclei to promote mitosis, its levels at septa drop. A model is proposed in which NIMA helps keep septal pores open during interphase and then closed when it is removed from them during mitosis. In support of this hypothesis, NIMA inactivation is shown to promote interphase septal pore closing. Because NIMA triggers nuclear pore complex opening during mitosis, our findings suggest that common cell cycle regulatory mechanisms might control septal pores and nuclear pores such that they are opened and closed out of phase to each other during cell cycle progression. The study provides insights into how and why cytoplasmically connected Aspergillus cells maintain mitotic autonomy.
细胞间桥是多细胞生物的一个保守特征。在多细胞真菌中，细胞通过称为隔膜孔的细胞间桥直接相连。我们利用构巢曲霉首次证明，隔膜孔在间期被调控为开放状态，而在有丝分裂期间关闭。与隔膜孔相关的蛋白质在成熟隔膜处呈现出动态的细胞周期调控定位。重要的是，有丝分裂期的NIMA激酶定位于正在形成的隔膜，并且令人惊讶的是，在整个间期它都保留在隔膜处。然而，在有丝分裂期间，当NIMA短暂定位于细胞核以促进有丝分裂时，其在隔膜处的水平下降。我们提出了一个模型，其中NIMA在间期帮助保持隔膜孔开放，而在有丝分裂期间当它从隔膜孔上移除时则使其关闭。为支持这一假设，研究表明NIMA失活会促进间期隔膜孔关闭。由于NIMA在有丝分裂期间触发核孔复合体开放，我们的研究结果表明，常见的细胞周期调控机制可能控制隔膜孔和核孔，使得它们在细胞周期进程中彼此异相地开放和关闭。这项研究为细胞质相连的曲霉细胞如何以及为何维持有丝分裂自主性提供了见解。
