AMPK phosphorylates GBF1 for mitotic Golgi disassembly.

In mammalian cells, the Golgi apparatus undergoes extensive fragmentation during mitosis; this is required not only for the partitioning of the complex but also for the process of mitosis. However, the molecular mechanism underlying the mitotic fragmentation of the Golgi is far from clear. Here, we show that AMP-activated protein kinase (AMPK) is phosphorylated and activated when cells enter mitosis. Activated AMPK phosphorylates GBF1, a guanine nucleotide exchange factor (GEF) for Arf-GTPases, disassociating GBF1 from the Golgi membrane and abolishing the action of GBF1 as an Arf1-GEF. We further demonstrate that the phosphorylation of AMPK and GBF1 is essential for Golgi disassembly and subsequent mitosis entry. These data suggest that AMPK-GBF1-Arf1 signaling is involved in the regulation of Golgi fragmentation during mitosis.