Identification and characterization of CF kinase

胞质分裂是细胞分裂过程中所有必需的细胞成分被分离成有丝分裂后的子细胞的过程。蛋白质磷酸化在有丝分裂控制中起着关键作用，但胞质分裂中细胞分离的机制还不清楚。我们报道了一种蛋白激酶活性，磷酸化的III型中间丝蛋白，胶质纤维酸性蛋白（GFAP），特别是在分裂沟的细胞动力学细胞。它被称为裂解沟（CF）激酶。现在，我们获得的证据表明，Rho相关激酶（Rho-激酶）是一个候选的CF激酶; Rho-激酶磷酸化GFAP在体外的相同位点，被CF激酶在体内磷酸化。我们还分析了CF激酶/Rho激酶活性的功能，通过引入突变GFAPs到III型中间毒性阴性细胞。CF激酶/Rho激酶磷酸化位点的突变损害了GFAP向有丝分裂后子细胞的分离。结果，未分离的细胞之间形成异常长的胞质桥样结构。这些结果表明，CF激酶/Rho-激酶对于GFAP向子细胞的分离是必需的，这反过来又确保了有效的细胞分离。

Cytokinesis is the mitotic precess in which all the essential cell components are segregated into postmitotic daughter cells It is suggested that protein phoshorylation plays pivotal roles in mitotic control, however the mechanisms for the cellular separation in cytokineses are not well characterized. We reported a protein kinase activity that phosphorylates a type III intermediate filament protein, glial fiberllary acidic protein (GFAP), specifically at the cleavage furrow of cytokinetic cells. It was termed cleavage furrow (CF) kinase. Now, we obtained evidence that Rho-associated Kinase (Rho-kinase) is a candidate for CF kinase ; Rho-kinase phosphorylated GFAP in vitro at the same sites that were phosphorylated by CF kinase in vivo. We also analyzed the functions of CF kinase/Rho-kinase activity by introducing mutant GFAPs into type III intermediate filament-negative cells. The mutation in CF kinase/Rho-kinase phosphorylation sites impaired GFAP segregation into postmitotic daughter cells. As a result, unusually long cytoplasmic bridge-like structure was formed between unseparated dughter cells. These results suggst that CF kinase/Rho-kinase is essential for the segragation of GFAP into daughter cells which in turn ensures efficient cellular separation.