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

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Abstract
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 phosphorylation of GRASP65 by Plk may be a critical event in the reorganization of the Golgi structure during mitosis.