Characterization of Cep85 - a new antagonist of Nek2A that is involved in the regulation of centrosome disjunction.

Canhe Chen,Lin Lu,Chengtao Yu,Zhe Xiao,Xianwen Yu,Fang Tian,Yun Wang

doi:10.1242/jcs.171637

Abstract

ABSTRACTNek2 has been implicated in centrosome disjunction at the onset of mitosis to promote bipolar spindle formation, and hyperactivation of Nek2 leads to the premature centrosome separation. Its activity, therefore, needs to be strictly regulated. In this study, we report that Cep85, an uncharacterized centrosomal protein, acts as a binding partner of Nek2A. It colocalizes with isoform A of Nek2 (Nek2A) at centrosomes and forms a granule meshwork enveloping the proximal ends of centrioles. Opposite to the effects of Nek2A, overexpression of Cep85 in conjunction with inhibition of the motor protein Eg5 (also known as KIF11) leads to the failure of centrosome disjunction. By contrast, depletion of Cep85 results in the precocious centrosome separation. We also define the Nek2A binding and centrosome localization domains within Cep85. Although the Nek2A-binding domain alone is sufficient to inhibit Nek2A kinase activity in vitro, both domains are indispensable for full suppression of centrosome disjunction in cells. Thus, we propose that Cep85 is a bona fide Nek2A-binding partner that surrounds the proximal ends of centrioles where it cooperates with PP1γ (also known as PPP1CC) to antagonize Nek2A activity in order to maintain the centrosome integrity in interphase in mammalian cells.

Highlights

The centrosome is an organelle that serves as the main microtubuleorganizing center (MTOC) to promote bipolar spindle formation and timely mitotic progression (Bornens, 2002; Nigg and Raff, 2009)
Identification of Cep85 protein as a binding partner of Nek2A Nek2A expression levels remain high in the S to G2 phase, its activity at the proximal ends of centrioles needs to be kept low to ensure that the centrosome is not to be separated precociously (Mardin and Schiebel, 2012)
Cep85 has been shown to localize to the proximal ends of centrioles, where Nek2A localizes and functions as a kinase to phosphorylate the proteinaceous linker connecting two mother centrioles (Bahe et al, 2005; Fry et al, 1998a; Mardin and Schiebel, 2012)

Summary

Introduction

The centrosome is an organelle that serves as the main microtubuleorganizing center (MTOC) to promote bipolar spindle formation and timely mitotic progression (Bornens, 2002; Nigg and Raff, 2009). It consists of a pair of centrioles and a surrounding protein meshwork called pericentriolar material (Bornens et al, 1987). C-Nap localizes at the proximal ends of the centriole and is considered to act as a docking site for rootletin and LRRC45. Both rootletin and LRRC45 interact and form a fiber-like structure

Methods

Results

Conclusion