A role for glycogen synthase kinase-3 in mitotic spindle dynamics and chromosome alignment.
Glycogen synthase kinase-3 (GSK-3) is a conserved, multifunctional kinase that is constitutively active in resting cells, and inactivated through phosphorylation by protein kinase B (PKB). We have investigated the temporal and spatial control of GSK-3 phosphorylation during the cell cycle in mammalian cells. We show that GSK-3 is present along the length of spindle microtubules and that a fraction of GSK-3 is phosphorylated during mitosis. Phospho-GSK-3 is abundant at the centrosomes and spindle poles but absent from other areas of the spindle. GSK-3 phosphorylation occurs concomitantly with the appearance of phosphorylated and active PKB at the centrosome, which suggests that PKB is the kinase responsible for phosphorylating and inactivating GSK-3 at the centrosome during mitosis. We demonstrate that lithium and two structurally distinct inhibitors of GSK-3 promote defects in microtubule length and chromosomal alignment during prometaphase. Treated cells contain mono-oriented chromosomes concentrated at the plus ends of astral microtubules, which are longer than in untreated cells. Live microscopy of cells expressing Histone-2B-GFP confirms that the inhibition of GSK-3 suppresses mitotic chromosome movement and leads to a prometaphase-like arrest. We propose that GSK-3 is regulated in a temporal and spatial manner during mitosis and, through controlling microtubule dynamics, plays an important role in chromosomal alignment on the metaphase plate.
Wakefield
James G
JG
Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK. james.wakefield@zoo.ox.ac.uk
Stephens
David J
DJ
Tavaré
Jeremy M
JM
D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D018385:Centrosome / Q000187:drug effects / Q000201:enzymology; D020090:Chromosome Segregation / Q000187:drug effects / Q000235:genetics*; D002875:Chromosomes / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005057:Eukaryotic Cells / Q000187:drug effects / Q000201:enzymology*; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008094:Lithium / Q000494:pharmacology; D008677:Metaphase / Q000187:drug effects / Q000235:genetics; D008870:Microtubules / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D008938:Mitosis / Q000187:drug effects / Q000235:genetics*; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D008941:Spindle Apparatus / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics
D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D011518:Proto-Oncogene Proteins; D008094:Lithium; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3