title: A novel signaling by vitamin A/retinol promotes self renewal of mouse embryonic stem cells by activating PI3K/Akt signaling pathway via insulin-like growth factor-1 receptor.
abstract: Pluripotent embryonic stem (ES) cells are a potential source of all types of cells for regenerative medicine. ES cells maintain pluripotency through a complex interplay of different signaling pathways and transcription factors, including leukemia inhibitory factor (LIF), Nanog, Sox2, and Oct3/4. Nanog, however, plays a key role in maintaining the pluripotency of mouse and human ES cells. Phosphoinositde 3-kinase (PI3K) signaling pathway which is activated in response to growth factors and cytokines also plays a critical role in promoting the survival and proliferation of ES cells. Our earlier studies revealed that retinol, the alcohol form of vitamin A, enhances the expression of Nanog and prevents differentiation of ES cells in long-term cultures. Normally vitamin A/retinol is associated with cell differentiation via its potent metabolite, retinoic acid. Thus far, no direct function has been ascribed to retinol itself. In this study, we demonstrate for the first time that retinol directly activates phosphoinositide three (PI3) kinase signaling pathway through IGF-1 receptor/insulin receptor substrate one (IRS-1) by engaging Akt/PKB-mTORC1 mammalian target of rapamycin-2 (mammalian target of rapamycin complex 2), indicating a growth factor-like function of vitamin A. Furthermore, ES cells do not express enzymes to metabolize retinol into retinoic acid and lack receptors for retinol transport into the cytoplasm, indicating that retinol signaling is independent of retinoic acid. This study presents a novel system to investigate how extracellular signals control the self renewal of ES cells which will be important for high-quality ES cells for regenerative medicine.
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
authors.forename: Liguo
authors.initials: L
authors.lastname: Chen
authors.forename: Jaspal S
authors.initials: JS
authors.lastname: Khillan
mesh_terms: D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D053595:Embryonic Stem Cells / Q000187:drug effects* / Q000201:enzymology; D004789:Enzyme Activation; D018398:Homeodomain Proteins / Q000378:metabolism; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D053605:Leukemia Inhibitory Factor / Q000378:metabolism; D051379:Mice; D000071317:Nanog Homeobox Protein; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D039904:Pluripotent Stem Cells / Q000187:drug effects* / Q000201:enzymology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017526:Receptor, IGF Type 1 / Q000187:drug effects* / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D058570:TOR Serine-Threonine Kinases; D013997:Time Factors; D014212:Tretinoin / Q000378:metabolism; D014801:Vitamin A / Q000378:metabolism / Q000494:pharmacology*; D018631:ras Proteins / Q000378:metabolism
chemical_list: D018398:Homeodomain Proteins; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; D053605:Leukemia Inhibitory Factor; D000071317:Nanog Homeobox Protein; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D017526:Receptor, IGF Type 1; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; D014212:Tretinoin; D014801:Vitamin A; D018631:ras Proteins; C526295:Irs1 protein, mouse; C507838:Lif protein, mouse; C475540:Nanog protein, mouse; C546842:MTOR protein, human; C546843:mTOR protein, mouse