Mio depletion links mTOR regulation to Aurora A and Plk1 activation at mitotic centrosomes.
Bottom Line: In this study, we report that Mio, a highly conserved member of the SEACAT/GATOR2 complex necessary for the activation of mTORC1 kinase, plays a critical role in mitotic spindle formation and subsequent chromosome segregation by regulating the proper concentration of active key mitotic kinases Plk1 and Aurora A at centrosomes and spindle poles.Mio-depleted cells showed reduced activation of Plk1 and Aurora A kinase at spindle poles and an impaired localization of MCAK and HURP, two key regulators of mitotic spindle formation and known substrates of Aurora A kinase, resulting in spindle assembly and cytokinesis defects.Our results indicate that a major function of Mio in mitosis is to regulate the activation/deactivation of Plk1 and Aurora A, possibly by linking them to mTOR signaling in a pathway to promote faithful mitotic progression.
Affiliation: Wellcome Trust Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Edinburgh EH9 3BF, Scotland, UK firstname.lastname@example.org Bill.Earnshaw@ed.ac.uk.Show MeSH
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Mentions: Depletion of Mio had significant effects on the activation of Aurora A and Plk1 at centrosomes. For example, although we observed no changes in total Aurora A localization or the amount on centrosomes and spindles (Fig. 6 A), the level of active Aurora A (Aurora AT288ph, which is phosphorylated at Thr288 on the activation loop) on centrosomes was significantly lower in Mio-depleted cells than in RNAi control cells (Fig. 6, B and D). We confirmed this by immunoblotting (Fig. 6 G). Rescue experiments on HeLa si02ResGFP-Mio cells, where the endogenous Mio was depleted using si02, rescued the prometaphase delay phenotype and restored Aurora AT288ph levels at spindle poles (Fig. S1, C–E). Depletion of all Mio using si01 gave the expected prometaphase delay and reduced Aurora AT288ph signal.
Affiliation: Wellcome Trust Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Edinburgh EH9 3BF, Scotland, UK email@example.com Bill.Earnshaw@ed.ac.uk.