Protein phosphatase 6 regulates mitotic spindle formation by controlling the T-loop phosphorylation state of Aurora A bound to its activator TPX2

• Published in: The Journal of cell biology Vol. 191; no. 7; pp. 1315 - 1332
• Main Authors: Zeng, Kang, Bastos, Ricardo Nunes, Barr, Francis A, Gruneberg, Ulrike
• Format: Journal Article
• Language: English
• Published: United States The Rockefeller University Press 27-12-2010; Rockefeller University Press
• Subjects: Anaphase - genetics; Antigens, Nuclear - metabolism; Aurora Kinases; Azepines - pharmacology; Catalytic Domain - genetics; Cell Cycle Proteins - genetics; Cell Cycle Proteins - metabolism; Cell division; Cell Line; Cell lines; Cell nucleus; Cell Nucleus - drug effects; Cell Nucleus - genetics; Cell Nucleus - pathology; Chromosome Segregation - genetics; Chromosomes; Cyclin B - metabolism; Enzymes; Fibroblasts - pathology; Gene expression regulation; Genotype & phenotype; HeLa Cells; Histones - genetics; Histones - metabolism; Holoenzymes - genetics; Holoenzymes - metabolism; Humans; Kinases; Kinesins - antagonists & inhibitors; Kinesins - metabolism; Microtubule-Associated Proteins - genetics; Microtubule-Associated Proteins - metabolism; Mitosis; Mitosis - physiology; Mitotic spindle apparatus; Models, Biological; Mutation - genetics; Nuclear Matrix-Associated Proteins - metabolism; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Phosphatases; Phosphoprotein Phosphatases - genetics; Phosphoprotein Phosphatases - metabolism; Phosphoric Monoester Hydrolases - genetics; Phosphorylation; Phosphorylation - drug effects; Polo-Like Kinase 1; Protein Binding - physiology; Protein Kinase Inhibitors - pharmacology; Protein Serine-Threonine Kinases - antagonists & inhibitors; Protein Serine-Threonine Kinases - metabolism; Protein Subunits - genetics; Protein Subunits - metabolism; Proteins; Proto-Oncogene Proteins - metabolism; Pyrimidines - pharmacology; RNA, Small Interfering - genetics; Small interfering RNA; Spindle Apparatus - drug effects; Spindle Apparatus - physiology; Telophase - genetics; Tubulin - genetics; Tubulin - metabolism
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.201008106

Many protein kinases are activated by a conserved regulatory step involving T-loop phosphorylation. Although there is considerable focus on kinase activator proteins, the importance of specific T-loop phosphatases reversing kinase activation has been underappreciated. We find that the protein phosphatase 6 (PP6) holoenzyme is the major T-loop phosphatase for Aurora A, an essential mitotic kinase. Loss of PP6 function by depletion of catalytic or regulatory subunits interferes with spindle formation and chromosome alignment because of increased Aurora A activity. Aurora A T-loop phosphorylation and the stability of the Aurora A-TPX2 complex are increased in cells depleted of PP6 but not other phosphatases. Furthermore, purified PP6 acts as a T-loop phosphatase for Aurora A-TPX2 complexes in vitro, whereas catalytically inactive mutants cannot dephosphorylate Aurora A or rescue the PPP6C depletion phenotype. These results demonstrate a hitherto unappreciated role for PP6 as the T-loop phosphatase regulating Aurora A activity during spindle formation and suggest the general importance of this form of regulation.