title: Phosphatase inhibitor-2 balances protein phosphatase 1 and aurora B kinase for chromosome segregation and cytokinesis in human retinal epithelial cells.
abstract: Mitosis in Saccharomyces cerevisiae depends on IPL1 kinase, which genetically interacts with GLC8. The metazoan homologue of GLC8 is inhibitor-2 (I-2), but its function is not understood. We found endogenous and ectopic I-2 localized to the spindle, midzone, and midbody of mitotic human epithelial ARPE-19 cells. Knockdown of I-2 by RNA interference produced multinucleated cells, with supernumerary centrosomes, multipolar spindles and lagging chromosomes during anaphase. These defects did not involve changes in levels of protein phosphatase-1 (PP1), and the multinuclear phenotype was rescued by overexpression of I-2. Appearance of multiple nuclei and supernumerary centrosomes required progression through the cell cycle and I-2 knockdown cells failed cytokinesis, as observed by time-lapse microscopy. Inhibition of Aurora B by hesperadin produced multinucleated cells and reduced H3S10 phosphorylation. I-2 knockdown enhanced this latter effect. Partial knockdown of PP1Calpha prevented multiple nuclei caused by either knockdown of I-2 or treatment with hesperadin. Expression of enhanced green fluorescent protein-I-2 or hemagglutinin-I-2 made cells resistant to hesperadin. We propose that I-2 acts to enhance Aurora B by inhibiting specific PP1 holoenzymes that dephosphorylate Aurora B substrates necessary for chromosome segregation and cytokinesis. Conserved together throughout eukaryotic evolution, I-2, PP1 and Aurora B function interdependently during mitosis.
authors: Center for Cell Signaling, Departments of Microbiology and Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
authors: Weiping
authors: W
authors: Wang
authors: P Todd
authors: PT
authors: Stukenberg
authors: David L
authors: DL
authors: Brautigan
mesh_terms: D064107:Aurora Kinase B; D064127:Aurora Kinases; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000201:enzymology; D018385:Centrosome / Q000187:drug effects / Q000201:enzymology; D020090:Chromosome Segregation / Q000187:drug effects; D048749:Cytokinesis / Q000187:drug effects; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D006657:Histones / Q000378:metabolism; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D008938:Mitosis / Q000187:drug effects; D008954:Models, Biological; D017239:Paclitaxel / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D054645:Protein Phosphatase 1 / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D011506:Proteins / Q000378:metabolism*; D034622:RNA Interference / Q000187:drug effects; D012160:Retina / Q000166:cytology*; D012694:Serine / Q000378:metabolism; D008941:Spindle Apparatus / Q000187:drug effects / Q000201:enzymology; D013449:Sulfonamides / Q000494:pharmacology; D000097847:Protein Phosphatase Inhibitory Proteins
chemical_list: D064107:Aurora Kinase B; D064127:Aurora Kinases; D006657:Histones; D007211:Indoles; D017239:Paclitaxel; D047428:Protein Kinase Inhibitors; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases; D011506:Proteins; D012694:Serine; D013449:Sulfonamides; C024833:protein phosphatase inhibitor-2; D000097847:Protein Phosphatase Inhibitory Proteins; C576921:AURKB protein, human; C474723:hesperadin