title: p27 Kip1 nuclear localization and cyclin-dependent kinase inhibitory activity are regulated by glycogen synthase kinase-3 in human colon cancer cells.
abstract: The cellular mechanisms regulating intestinal differentiation are poorly understood. Sodium butyrate (NaBT), a short-chain fatty acid, increases p27 Kip1 expression and induces cell cycle arrest associated with intestinal cell differentiation. Here, we show that treatment of intestinal-derived cells with NaBT induced G0/G1 arrest and intestinal alkaline phosphatase, a marker of differentiation, activity and mRNA expression; this induction was attenuated by inhibition of glycogen synthase kinase-3 (GSK-3). Moreover, treatment with NaBT increased the nuclear, but not the cytosolic, expression and activity of GSK-3beta. NaBT decreased cyclin-dependent kinase CDK2 activity and induced p27 Kip1 expression; inhibition of GSK-3 rescued NaBT-inhibited CDK2 activity and blocked NaBT-induced p27 Kip1 expression in the nucleus but not in the cytoplasm. In addition, we demonstrate that NaBT decreased the expression of S-phase kinase-associated protein 2 (Skp2), and this decrease was attenuated by GSK-3 inhibition. Furthermore, NaBT increased p27 Kip1 binding to CDK2, which was completely abolished by GSK-3 inhibition. Overexpression of an active form of GSK-3beta reduced Skp2 expression, increased p27 Kip1 in the nucleus and increased p27 Kip1 binding to CDK2. Our results suggest that GSK-3 not only regulates nuclear p27 Kip1 expression through the downregulation of nuclear Skp2 expression but also functions to regulate p27 Kip1 assembly with CDK2, thereby playing a critical role in the G0/G1 arrest associated with intestinal cell differentiation.
authors.affiliation: Department of Surgery, The University of Texas Medical Branch, Galveston, TX 77555-0536, USA.
authors.forename: Q
authors.initials: Q
authors.lastname: Wang
authors.forename: Y
authors.initials: Y
authors.lastname: Zhou
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.forename: B M
authors.initials: BM
authors.lastname: Evers
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002087:Butyrates / Q000378:metabolism; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism*; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism*; D051357:Cyclin-Dependent Kinase 2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics / Q000378:metabolism*; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D044786:S-Phase Kinase-Associated Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
chemical_list: D002087:Butyrates; D044786:S-Phase Kinase-Associated Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D051057:Proto-Oncogene Proteins c-akt; D051357:Cyclin-Dependent Kinase 2; D038362:Glycogen Synthase Kinase 3; D000469:Alkaline Phosphatase