Serpico Angela Flavia, Pisauro Caterina, Trano Asia, Grieco Domenico
DMMBM, University of Naples "Federico II", via S. Pansini 5, 80131, Naples, Italy.
CEINGE Biotecnologie Avanzate "Franco Salvatore", via Gaetano Salvatore 486, 80145, Naples, Italy.
Commun Biol. 2025 May 30;8(1):841. doi: 10.1038/s42003-025-08281-8.
During cell division, the onset of mitosis is granted by activation of cyclin B-dependent kinase 1 (Cdk1), master mitotic kinase, coordinated with inactivation of Cdk1-counteracting phosphatases. PP2A-B55, a major of these phosphatases, is inhibited in mitosis by Arpp-19 and Ensa, two very similar proteins, once phosphorylated by the Cdk1-stimulated kinase Greatwall (Gwl). We show here that Arpp-19 is also phosphorylated in a Cdk1-dependent manner at serine 23, a site missing in mammalian Ensa, in mitotic human cells and dephosphorylated at this site during mitosis exit. Moreover, we found that this phosphorylation control grants chromosome stability since substituting endogenous Arpp-19 with a S23-Arpp-19 phosphorylation-resistant mutant increased the frequency of chromosome segregation errors and accelerated the timing of mitosis exit. Conversely, substitution with a S23-Arpp-19 phosphorylation-mimicking mutant delayed mitosis exit. S23-Arpp-19 dephosphorylation resisted to the potent PP2A inhibitor Okadaic Acid but required the phosphatase Fcp1. Our data unveil a phosphorylation switch that grants timely mitosis exit and chromosome stability.
在细胞分裂过程中，有丝分裂的起始是由细胞周期蛋白B依赖性激酶1（Cdk1，主要的有丝分裂激酶）的激活所促成的，这一过程与Cdk1拮抗磷酸酶的失活相协调。PP2A-B55是这些磷酸酶中的一种主要类型，在有丝分裂过程中，一旦被Cdk1刺激的激酶Greatwall（Gwl）磷酸化，就会被两种非常相似的蛋白质Arpp-19和Ensa抑制。我们在此表明，在有丝分裂的人类细胞中，Arpp-19在丝氨酸23位点也以Cdk1依赖性方式被磷酸化，这是哺乳动物Ensa中缺失的一个位点，并且在有丝分裂退出过程中该位点会发生去磷酸化。此外，我们发现这种磷酸化控制赋予了染色体稳定性，因为用一种对S23-Arpp-19磷酸化具有抗性的突变体替代内源性Arpp-19会增加染色体分离错误的频率，并加速有丝分裂退出的时间。相反，用一种模拟S23-Arpp-19磷酸化的突变体替代则会延迟有丝分裂退出。S23-Arpp-19的去磷酸化对强效PP2A抑制剂冈田酸具有抗性，但需要磷酸酶Fcp1。我们的数据揭示了一种磷酸化开关，它赋予了适时的有丝分裂退出和染色体稳定性。
