title: IGF-I and FGF-2 coordinately enhance cyclin D1 and cyclin E-cdk2 association and activity to promote G1 progression in oligodendrocyte progenitor cells.
abstract: A critical question in developmental neurobiology is how stem and progenitor cells interpret multiple signals to decide whether to proliferate or exit the cell cycle. Insulin-like growth factor (IGF)-I and fibroblast growth factor (FGF)-2 have known functions individually in development of neural stem cells as well as more restricted neuronal and glial progenitor cells. The goal of this study was to elucidate how IGF-I and FGF-2 coordinately regulate the cell cycle machinery in primary oligodendrocyte progenitors (OPs). IGF-I/FGF-2 synergistically increased the numbers of OP cells recruited into S phase. IGF-I enhanced FGF-2 induction of cyclin D1, activation of G(1) cyclin-cyclin-dependent kinase (cdk) complexes, and hyperphosphorylation of retinoblastoma protein (pRb). Moreover, IGF-I was required for G(2)/M progression. In contrast, FGF-2 decreased levels of the cdk inhibitor p27(Kip1) associated with cyclin E-cdk2. These studies provide a mechanistic basis for coordinate regulation of cell cycle progression in progenitor cells by multiple growth factors.
authors.affiliation: Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, PA 17033, USA.
authors.forename: Terra J
authors.initials: TJ
authors.lastname: Frederick
authors.forename: Teresa L
authors.initials: TL
authors.lastname: Wood
mesh_terms: D000818:Animals; D042846:CDC2-CDC28 Kinases / Q000378:metabolism; D002478:Cells, Cultured; D019938:Cyclin D1 / Q000378:metabolism*; D019927:Cyclin E / Q000378:metabolism*; D051357:Cyclin-Dependent Kinase 2; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D016193:G1 Phase / Q000187:drug effects / Q000502:physiology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D009836:Oligodendroglia / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013234:Stem Cells / Q000187:drug effects* / Q000378:metabolism
chemical_list: D019927:Cyclin E; D016222:Fibroblast Growth Factor 2; D019938:Cyclin D1; D007334:Insulin-Like Growth Factor I; D042846:CDC2-CDC28 Kinases; C495892:Cdk2 protein, rat; D051357:Cyclin-Dependent Kinase 2