Phosphatase inhibitor-2 balances protein phosphatase 1 and aurora B kinase for chromosome segregation and cytokinesis in human retinal epithelial cells.
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.
Wang
Weiping
W
Center for Cell Signaling, Departments of Microbiology and Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
Stukenberg
P Todd
PT
Brautigan
David L
DL
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
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