Analysis of the midbody interactome reveals new roles for PP1 phosphatases in late cytokinesis

The midbody is an organelle assembled at the intercellular bridge connecting the two daughter cells at the end of mitosis. It is essential for the final separation of the daughter cells and involved in other important processes, including cell fate, pluripotency, apical-basal polarity, and cilium/lumen formation. The midbody is composed of numerous proteins with diverse functions distributed in a precise pattern. Here we report the first characterization of the midbody protein-protein interaction network (interactome), which provides an extremely valuable resource for understanding its multiple roles. Analysis of this midbody interactome led to the discovery that PP1/MYPT1 phosphatase regulates microtubule dynamics in late cytokinesis through de-phosphorylation of the kinesin MKLP1/KIF23, a finding that unexpectedly expands the temporal window of activity of this phosphatase during mitosis.

中体（midbody）是在有丝分裂末期，于连接两个子细胞的细胞间桥处组装形成的细胞器。其对子细胞的最终分离至关重要，并参与诸多重要生物学过程，涵盖细胞命运、多能性、顶基极性以及纤毛/管腔形成等。中体由大量功能多样的蛋白质构成，这些蛋白质以精准的模式分布于其中。本研究首次完成了中体蛋白质-蛋白质相互作用网络（相互作用组，interactome）的系统表征，该资源为解析中体的多重生物学功能提供了极具价值的研究基础。通过对该中体相互作用组的分析，我们发现PP1/MYPT1磷酸酶可通过对驱动蛋白MKLP1/KIF23的去磷酸化修饰，在胞质分裂后期调控微管动力学；这一发现意外拓宽了该磷酸酶在有丝分裂过程中的活性时间窗口。