Identification and characterization of CF kinase

胞质分裂是一个有丝分裂的过程，在这个过程中，所有重要的细胞成分都被分离到有丝分裂后的子细胞中。有人认为，蛋白质磷酸化在有丝分裂控制中起着关键作用，但细胞分裂中细胞分离的机制尚未得到很好的描述。我们报道了一种蛋白激酶活性，它能磷酸化一种III型中间丝蛋白，胶质纤维酸性蛋白(GFAP)，特别是在细胞动细胞的分裂沟中。它被命名为卵裂沟(CFK)。现在，我们获得的证据表明，Rho相关激酶(Rho-kinase，Rho-Kinase)是CFK的候选者；Rho-Kinase在体外磷酸化GFAP的位置与在体内被CFK磷酸化的位置相同。我们还通过将突变型GFAP导入III型中间丝阴性细胞，分析了CFK/Rho-Kinase活性的功能。CFK/Rho-Kinase磷酸化位点突变削弱了GFAP向有丝分裂后子代细胞的分离。结果是，在未分离的Dughter细胞之间形成了异常长的细胞质桥状结构。这些结果表明，CFK/Rho-Kinase在GFAP向子代细胞的沉积过程中是必不可少的，而子代细胞的沉积又保证了细胞的有效分离。

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.