beta-catenin mediates insulin-like growth factor-I actions to promote cyclin D1 mRNA expression, cell proliferation and survival in oligodendroglial cultures.
By promoting cell proliferation, survival and maturation insulin-like growth factor (IGF)-I is essential to the normal growth and development of the central nervous system. It is clear that IGF-I actions are primarily mediated by the type I IGF receptor (IGF1R), and that phosphoinositide 3 (PI3)-Akt kinases and MAP kinases signal many of IGF-I-IGF1R actions in neural cells, including oligodendrocyte lineage cells. The precise downstream targets of these signaling pathways, however, remain to be defined. We studied oligodendroglial cells to determine whether beta-catenin, a molecule that is a downstream target of glycogen synthase kinase-3beta (GSK3beta) and plays a key role in the Wnt canonical signaling pathway, mediates IGF-I actions. We found that IGF-I increases beta-catenin protein abundance within an hour after IGF-I-induced phosphorylation of Akt and GSK3beta. Inhibiting the PI3-Akt pathway suppressed IGF-I-induced increases in beta-catenin and cyclin D1 mRNA, while suppression of GSK3beta activity simulated IGF-I actions. Knocking-down beta-catenin mRNA by RNA interference suppressed IGF-I-stimulated increases in the abundance of cyclin D1 mRNA, cell proliferation, and cell survival. Our data suggest that beta-catenin is an important downstream molecule in the PI3-Akt-GSK3beta pathway, and as such it mediates IGF-I upregulation of cyclin D1 mRNA and promotion of cell proliferation and survival in oligodendroglial cells.
Ye
Ping
P
Department of Pediatrics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7039, USA. ping_ye@med.unc.edu
Hu
Qichen
Q
Liu
Hedi
H
Yan
Yun
Y
D'ercole
A Joseph
AJ
D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D056741:Cyclin D / Q000378:metabolism*; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D009836:Oligodendroglia / Q000502:physiology*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D013234:Stem Cells / Q000502:physiology; D013997:Time Factors; D051176:beta Catenin / Q000378:metabolism*
C495268:Ctnnb1 protein, rat; D056741:Cyclin D; D012333:RNA, Messenger; D051176:beta Catenin; D007334:Insulin-Like Growth Factor I; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3