title: Glycogen synthase kinase 3beta (GSK3beta) mediates 6-hydroxydopamine-induced neuronal death.
abstract: The causes of sporadic Parkinson's disease (PD) are poorly understood. 6-Hydroxydopamine (6-OHDA), a PD mimetic, is widely used to model this neurodegenerative disorder in vitro and in vivo; however, the underlying mechanisms remain incompletely elucidated. We demonstrate here that 6-OHDA evoked endoplasmic reticulum (ER) stress, which was characterized by an up-regulation in the expression of GRP78 and GADD153 (Chop), cleavage of procaspase-12, and phosphorylation of eukaryotic initiation factor-2 alpha in a human dopaminergic neuronal cell line (SH-SY5Y) and cultured rat cerebellar granule neurons (CGNs). Glycogen synthase kinase-3 beta (GSK3beta) responds to ER stress, and its activity is regulated by phosphorylation. 6-OHDA significantly inhibited phosphorylation of GSK3beta at Ser9, whereas it induced hyperphosphorylation of Tyr216 with little effect on GSK3beta expression in SH-SY5Y cells and PC12 cells (a rat dopamine cell line), as well as CGNs. Furthermore, 6-OHDA decreased the expression of cyclin D1, a substrate of GSK3beta, and dephosphorylated Akt, the upstream signaling component of GSK3beta. Protein phosphatase 2A (PP2A), an ER stress-responsive phosphatase, was involved in 6-OHDA-induced GSK3beta dephosphorylation (Ser9). Blocking GSK3beta activity by selective inhibitors (lithium, TDZD-8, and L803-mts) prevented 6-OHDA-induced cleavage of caspase-3 and poly(ADP-ribose) polymerase (PARP), DNA fragmentations and cell death. With a tetracycline (Tet)-controlled TrkB inducible system, we demonstrated that activation of TrkB in SH-SY5Y cells alleviated 6-OHDA-induced GSK3beta dephosphorylation (Ser9) and ameliorated 6-OHDA neurotoxicity. TrkB activation also protected CGNs against 6-OHDA-induced damage. Although antioxidants also offered neuroprotection, they had little effect on 6-OHDA-induced GSK3beta activation. These results suggest that GSK3beta is a critical intermediate in pro-apoptotic signaling cascades that are associated with neurodegenerative diseases, thus providing a potential target site amenable to pharmacological intervention.
authors.affiliation: Department of Microbiology, Immunology & Cell Biology, West Virginia University School of Medicine, Robert C. Byrd Health Sciences Center, Morgantown, West Virginia 26506, USA.
authors.forename: Gang
authors.initials: G
authors.lastname: Chen
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Bower
authors.forename: Cuiling
authors.initials: C
authors.lastname: Ma
authors.forename: Shengyun
authors.initials: S
authors.lastname: Fang
authors.forename: Carol J
authors.initials: CJ
authors.lastname: Thiele
authors.forename: Jia
authors.initials: J
authors.lastname: Luo
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology; D022762:CCAAT-Enhancer-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D002525:Cerebellar Cortex / Q000166:cytology; D019938:Cyclin D1 / Q000096:biosynthesis / Q000235:genetics; D000091342:Endoplasmic Reticulum Chaperone BiP; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000502:physiology*; D000071679:Glycogen Synthase Kinase 3 beta; D006360:Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D018021:Lithium Chloride / Q000494:pharmacology; D018832:Molecular Chaperones / Q000096:biosynthesis / Q000235:genetics; D009410:Nerve Degeneration; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D009474:Neurons / Q000187:drug effects* / Q000473:pathology; D016627:Oxidopamine / Q000633:toxicity*; D016716:PC12 Cells / Q000187:drug effects / Q000473:pathology; D010300:Parkinson Disease / Q000201:enzymology; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D054648:Protein Phosphatase 2; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D020813:Receptor, trkB / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013830:Thiadiazoles / Q000494:pharmacology; D051742:Transcription Factor CHOP; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics
chemical_list: C494356:4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione; D019208:Brain-Derived Neurotrophic Factor; D022762:CCAAT-Enhancer-Binding Proteins; C497249:DDIT3 protein, human; C497251:Ddit3 protein, rat; D000091342:Endoplasmic Reticulum Chaperone BiP; D004791:Enzyme Inhibitors; D015852:Eukaryotic Initiation Factor-2; C051684:GRP78 protein, rat; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D009419:Nerve Tissue Proteins; D011518:Proto-Oncogene Proteins; D013830:Thiadiazoles; D014157:Transcription Factors; D019938:Cyclin D1; D051742:Transcription Factor CHOP; D016627:Oxidopamine; D020813:Receptor, trkB; C494918:AKT1 protein, human; C494920:Akt1 protein, rat; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D018021:Lithium Chloride