Cdk1/Erk2- and Plk1-Dependent Phosphorylation of a Centrosome Protein, Cep55, Is Required for Its Recruitment to Midbody and Cytokinesis

Megan Fabbro, Bin-Bing Zhou, Mikiko Takahashi, Boris Sarcevic, Preeti Lal, Mark E. Graham, Brian G. Gabrielli, Phillip J. Robinson, Erich A. Nigg, Yoshitaka Ono, Kum Kum Khanna

Centrosomes in mammalian cells have recently been implicated in cytokinesis; however, their role in this process is poorly defined. Here, we describe a human coiled-coil protein, Cep55 (centrosome protein 55 kDa), that localizes to the mother centriole during interphase. Despite its association with gamma-TuRC anchoring proteins CG-NAP and Kendrin, Cep55 is not required for microtubule nucleation. Upon mitotic entry, centrosome dissociation of Cep55 is triggered by Erk2/Cdk1-dependent phosphorylation at S425 and S428. Furthermore, Cep55 locates to the midbody and plays a role in cytokinesis, as its depletion by siRNA results in failure of this process. S425/428 phosphorylation is required for interaction with Plk1, enabling phosphorylation of Cep55 at S436. Cells expressing phosphorylation-deficient mutant forms of Cep55 undergo cytokinesis failure. These results highlight the centrosome as a site to organize phosphorylation of Cep55, enabling it to relocate to the midbody to function in mitotic exit and cytokinesis.