title: Insulin-like growth factor-I-stimulated Akt phosphorylation and oligodendrocyte progenitor cell survival require cholesterol-enriched membranes.
abstract: Previously we showed that insulin-like growth factor-I (IGF-I) promotes sustained phosphorylation of Akt in oligodendrocyte progenitor cells (OPCs) and that Akt phosphorylation is required for survival of these cells. The direct mechanisms, however, by which IGF-I promotes Akt phosphorylation are currently undefined. Recently, cholesterol-enriched membranes (CEMs) have been implicated in regulation of growth factor-mediated activation of the PI3K/Akt pathway and survival of mature oligodendrocytes; however, less is know about their role in OPC survival. In the present study, we investigate the role of CEMs in IGF-I-mediated Akt phosphorylation and OPC survival. We report that acute disruption of membrane cholesterol with methyl-beta-cyclodextrin results in altered OPC morphology and inhibition of IGF-I-mediated Akt phosphorylation. We also report that long-term inhibition of cholesterol biosynthesis with 25-hydroxycholesterol blocks IGF-I stimulated Akt phosphorylation and cell survival. Moreover, we show that the PI3K regulatory subunit, p85, Akt, and the IGF-IR are sequestered within cholesterol-enriched fractions in steady-state stimulation of the IGF-IR and that phosphorylated Akt and IGF-IR are present in cholesterol-enriched fractions with IGF-I stimulation. Together, the results of these studies support a role for CEMs or "lipid rafts" in IGF-I-mediated Akt phosphorylation and provide a better understanding of the mechanisms by which IGF-I promotes OPC survival.
authors.affiliation: Department of Neurology and Neurosciences, University Hospital Cancer Center, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Romanelli
authors.forename: Kedar R
authors.initials: KR
authors.lastname: Mahajan
authors.forename: Clifton G
authors.initials: CG
authors.lastname: Fulmer
authors.forename: Teresa L
authors.initials: TL
authors.lastname: Wood
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D006888:Hydroxycholesterols / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000378:metabolism* / Q000494:pharmacology; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D009836:Oligodendroglia / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017526:Receptor, IGF Type 1 / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013234:Stem Cells / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D047392:beta-Cyclodextrins / Q000494:pharmacology
chemical_list: D006888:Hydroxycholesterols; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; D007334:Insulin-Like Growth Factor I; C007997:25-hydroxycholesterol; D002784:Cholesterol; D019869:Phosphatidylinositol 3-Kinases; D017526:Receptor, IGF Type 1; D051057:Proto-Oncogene Proteins c-akt