title: S6K Promotes Dopaminergic Neuronal Differentiation Through PI3K/Akt/mTOR-Dependent Signaling Pathways in Human Neural Stem Cells.
abstract: It has recently been reported that the phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling pathway regulates neuronal differentiation of neural stem cells (NSCs) derived from rats or mice and is essential for the self-renewal of human embryonic stem cells (hESCs). However, the roles of PI3K/Akt/mTOR signaling pathways during proliferation and dopaminergic neuronal differentiation of human neural stem cells (hNSCs) are poorly understood. In this study, we examined the effect of regulation of these intracellular signaling pathways in hNSCs on the potential to maintain proliferation and induce dopaminergic neuronal differentiation. Dopaminergic neuronal differentiation depended on the concentration of insulin in our culture system. Inhibition of PI3K/Akt with LY294002 reduced proliferation and inhibited dopaminergic neuronal differentiation of these cells. We also found that rapamycin, a specific inhibitor of mTOR, significantly reduced neuronal differentiation without affecting proliferation. Inhibition of the Akt/mTOR signaling pathway led to inhibition of p70 ribosomal S6 kinase (S6K) signaling, which reduced dopaminergic neuronal differentiation in hNSCs. Inhibition of S6K by a specific chemical inhibitor, PF-4708671 inhibited dopaminergic neuronal differentiation of hNSCs. As expected, transduction with a dominant negative S6K1 (S6K1-DN) construct impaired dopaminergic neuronal differentiation of hNSCs. Conversely, overexpression of constitutively active S6K1 (S6K1-CA) promoted dopaminergic neuronal differentiation of these cells. In a survival study, 4 weeks after transplantation, no or very few donor cells were viable in striata grafted with S6K1-DN-transduced hNSCs. In contrast, S6K1-CA-transduced hNSCs survived, integrated into striata to generate tubular masses of grafts and differentiated toward TH-positive cells. Taken together, these data demonstrated that insulin promotes dopaminergic neuronal differentiation through a PI3K/Akt/mTOR-dependent pathway and that S6K plays a critical role in dopaminergic neuronal differentiation in hNSCs.
authors.affiliation: Hanyang Biomedical Research Institute, Hanyang University, 133-791, Seoul, Republic of Korea.|Department of Pharmacology, College of Medicine, Hanyang University, 133-791, Seoul, Republic of Korea.
authors.forename: Jeong Eun
authors.initials: JE
authors.lastname: Lee
authors.affiliation: Hanyang Biomedical Research Institute, Hanyang University, 133-791, Seoul, Republic of Korea.|Graduate School of Biomedical Science and Engineering, Hanyang University, 133-791, Seoul, Republic of Korea.
authors.forename: Mi Sun
authors.initials: MS
authors.lastname: Lim
authors.affiliation: Hanyang Biomedical Research Institute, Hanyang University, 133-791, Seoul, Republic of Korea.|Department of Pharmacology, College of Medicine, Hanyang University, 133-791, Seoul, Republic of Korea.
authors.forename: Jae Hyun
authors.initials: JH
authors.lastname: Park
authors.affiliation: Hanyang Biomedical Research Institute, Hanyang University, 133-791, Seoul, Republic of Korea. chshpark@hanyang.ac.kr.|Graduate School of Biomedical Science and Engineering, Hanyang University, 133-791, Seoul, Republic of Korea. chshpark@hanyang.ac.kr.
authors.forename: Chang Hwan
authors.initials: CH
authors.lastname: Park
authors.affiliation: Hanyang Biomedical Research Institute, Hanyang University, 133-791, Seoul, Republic of Korea. hckoh@hanyang.ac.kr.|Department of Pharmacology, College of Medicine, Hanyang University, 133-791, Seoul, Republic of Korea. hckoh@hanyang.ac.kr.
authors.forename: Hyun Chul
authors.initials: HC
authors.lastname: Koh
mesh_terms: D000818:Animals; D002452:Cell Count; D002454:Cell Differentiation / Q000187:drug effects*; D019070:Cell Lineage / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D059290:Dopaminergic Neurons / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D000066449:Human Embryonic Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D058953:Neural Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051381:Rats; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D033581:Stem Cell Transplantation; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D014161:Transduction, Genetic; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: D007328:Insulin; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; D014446:Tyrosine 3-Monooxygenase
keywords: Dopaminergic neuronal differentiation; Human neural stem cells; PI3K/Akt/mTOR signaling; Proliferation; S6K