Polo-like kinase is required for the fragmentation of pericentriolar Golgi stacks during mitosis

The pericentriolar stacks of Golgi cisternae undergo extensive reorganization during mitosis in mammalian cells. GM130 and GRASP65 (Golgi reassembly stacking protein of 65 kDa) are Golgi-associated proteins that are targets of mitotic kinases, and they have also been implicated in the reorganization of the Golgi structure during cell division. Previous studies have reported that mitogen-activated protein kinase kinase-1 (MEK1} and Cdc2 protein kinases are involved in these dynamic changes in the Golgi structure. More recently, the mitotic polo-like kinase (Plk} has been shown to interact with and phosphorylate GRASP65. Here, we provide evidence that Plk is involved in the mitosis-specific fragmentation of the Golgi apparatus. The addition of kinase-defective Plk or immunodepletion of Plk disrupts the fragmentation process. Furthermore, Golgi fragmentation is inhibited by the addition of either full-length or truncated GRASP65. These findings suggest that phospharylation of GRASP65 by Plk may be a critical event in the reorganization of the Golgi structure during mitosis.