title: Constitutive overexpression of CDK2 inhibits neuronal differentiation of rat pheochromocytoma PC12 cells.
abstract: Changes in the levels of cyclins A, D, and E, p21, and cyclin-dependent kinase 2 (CDK2) were examined in rat pheochromocytoma PC12 cells during neuronal differentiation induced by nerve growth factor (NGF). Expression of cyclin A decreased to an undetectable level after 5 days of exposure to NGF, while expression of CDK2 decreased gradually after day 3. In contrast, the levels of cyclins D1 and E increased gradually through day 10, yet the amount of cyclin E associated with CDK2 decreased concomitant with a decrease in the CDK2 protein level. p21 expression increased gradually after day 7, while the level of CDK2-associated p21 remained unchanged. When human cDNAs encoding cyclins and CDK2 were introduced into PC12 cells, only CDK2 overexpression inhibited NGF-induced differentiation. The cell lines overexpressing CDK2 showed stable and high levels of CDK2 kinase activity during differentiation, whereas parental and vector-transfected cell lines displayed a marked decline in CDK2 kinase activity 1 day after NGF treatment. In cell lines overexpressing cyclins A, D, and E, this reduction of the kinase activity was not apparent until day 3. These results suggest that down-regulation of CDK2 activity is a crucial event for the neuronal differentiation of PC12 cells.
authors.affiliation: Department of Oncogene Research, Osaka University, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Dobashi
authors.forename: T
authors.initials: T
authors.lastname: Kudoh
authors.forename: A
authors.initials: A
authors.lastname: Matsumine
authors.forename: K
authors.initials: K
authors.lastname: Toyoshima
authors.forename: T
authors.initials: T
authors.lastname: Akiyama
mesh_terms: D000310:Adrenal Gland Neoplasms; D000818:Animals; D042846:CDC2-CDC28 Kinases; D002454:Cell Differentiation; D002455:Cell Division; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000096:biosynthesis / Q000378:metabolism*; D016213:Cyclins / Q000096:biosynthesis / Q000378:metabolism*; D018076:DNA, Complementary; D015870:Gene Expression; D006801:Humans; D007700:Kinetics; D009474:Neurons / Q000166:cytology*; D016716:PC12 Cells; D010673:Pheochromocytoma; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D014162:Transfection
chemical_list: D016213:Cyclins; D018076:DNA, Complementary; D011994:Recombinant Proteins; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; C495892:Cdk2 protein, rat; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases