Abstract
Proliferation and apoptosis are increased in many types of inflammatory diseases. A role for the cyclin kinase inhibitor p27(Kip1) (p27) in limiting proliferation has been shown. In this study, we show that p27(-/-) mesangial cells and fibroblasts have strikingly elevated rates of apoptosis, not proliferation, when deprived of growth factors. Apoptosis was rescued by restoration of p27 expression. Cyclin A-cyclin-dependent kinase 2 (CDK2) activity, but not cyclin E-CDK2 activity, was increased in serum-starved p27(-/-) cells, and decreasing CDK2 activity, either pharmacologically (Roscovitine) or by a dominant-negative mutant, inhibited apoptosis. Our results show that a new biological function for the CDK inhibitor p27 is protection of cells from apoptosis by constraining CDK2 activity. These results suggest that CDK inhibitors are necessary for coordinating the cell cycle and cell-death programs so that cell viability is maintained during exit from the cell cycle.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Apoptosis* / genetics
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CDC2-CDC28 Kinases*
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Cell Cycle Proteins*
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Cyclin E / genetics
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Cyclin E / metabolism
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Cyclin-Dependent Kinase 2
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Cyclin-Dependent Kinase Inhibitor p27
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Cyclin-Dependent Kinases / antagonists & inhibitors
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Cyclin-Dependent Kinases / genetics
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Cyclin-Dependent Kinases / metabolism
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Gene Expression Regulation, Enzymologic
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Genes, Tumor Suppressor
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Glomerular Mesangium / metabolism*
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Glomerular Mesangium / pathology*
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Mice
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Microtubule-Associated Proteins / genetics
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Microtubule-Associated Proteins / metabolism*
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism
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Rats
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Rats, Sprague-Dawley
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Tumor Suppressor Proteins*
Substances
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Cdkn1b protein, mouse
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Cdkn1b protein, rat
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Cell Cycle Proteins
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Cyclin E
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Microtubule-Associated Proteins
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Tumor Suppressor Proteins
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Cyclin-Dependent Kinase Inhibitor p27
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Protein Serine-Threonine Kinases
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CDC2-CDC28 Kinases
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Cdk2 protein, mouse
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Cdk2 protein, rat
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Cyclin-Dependent Kinase 2
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Cyclin-Dependent Kinases