A role for AMPK in the regulation of mitosis and cytokinesis

AMP-activated protein kinase (AMPK) has a central role in maintaining cellular energy homeostasis. AMPK is activated allosterically by AMP and signals to inhibit ATP consuming pathways while simultaneously promoting ATP producing pathways. As such AMPK exerts an anti-proliferative effect to induce cell cycle arrest when nutrient resources are limited. Although many of the anti-proliferative effects of AMPK have been well documented during interphase, less is known about how AMPK signalling may influence mitosis. A few publications have reported that levels of active phospho-T172 AMPK increase as mitosis progresses and a link has also been reported between AMPK and myosin regulatory light chain (MRLC) in mitosis. In this Thesis, a combination of cellular, genetic and biochemical techniques were used to further characterise the role of AMPK in mitosis. A novel localisation of the AMPKα1 subunit was described, where AMPKα1 was detected at the microtubule organising centres (MTOCs) during mitosis in both primary human cells and in HeLa cells. AMPKα2 localisation to the midbody was also demonstrated in primary cells and in cell lines. Modulation of AMPK activity by either pharmacological or genetic means caused cell cycle arrest and influenced polyploidy in a number of cell lines. A yeast genetic approach was utilised to investigate the link between the AMPK pathway and a number of key mitotic regulates. Genetic interactions were detected between the AMPK pathway and S. pombe aurora kinase (ark1), polo-like kinase (plo1), anillin (mid1) and components of the endosomal sorting complex required for transport (ESCRT) machinery. Furthermore, a network of cross phosphorylation events were described in vitro between the mammalian protein orthologues. This included the phosphorylation of aurora A, aurora B and PLK1 by AMPK and the phosphorylation of aurora A and aurora B by Ca2+/calmodulin-dependent protein kinase kinase β (CaMKKβ). Considering the localisation of AMPK to mitotic structures and the numerous interactions documented with mitotic proteins, a role for AMPK in the regulation of mitosis is clear although the precise cellular effects remain difficult to discern.