title: The Wnt pool of glycogen synthase kinase 3beta is critical for trophic-deprivation-induced neuronal death.
abstract: Glycogen synthase kinase 3 (GSK-3) is implicated in neuronal death through a causal role, and precise mechanisms have not been unambiguously defined. We show that short hairpin RNA (shRNA) knockdown of GSK-3beta, but not GSK-3alpha, protects cerebellar granule neurons from trophic-deprivation-induced death. Using compartment-targeted inhibitors of the Wnt-regulated GSK-3 pool, NLS-FRAT1, NES-FRAT1, and axin-GSK-3-interacting domain (axin-GID), we locate proapoptotic GSK-3 action to the cytosol and regulation of Bim protein turnover despite constitutive cycling of GSK-3 between the cytosol and nucleus, revealed by leptomycin B. We examine the importance of Ser21/9 (GSK-3alpha/beta) phosphorylation on proapoptotic GSK-3 function. Neurons isolated from GSK-3alpha/beta(S21A/S9A) knock-in mice survive normally and are fully sensitive to trophic-deprivation-induced death. Nonetheless, inhibition of GSK-3 catalytic activity with lithium or SB216763 protects GSK-3alpha/beta(S21A/S9A) neurons from death. This indicates that dephosphorylation of GSK-3beta/Ser9 and GSK-3alpha/Ser21 is insufficient for GSK-3 proapoptotic function and that another level of regulation is required. Gel filtration reveals a stress-induced loss of neuronal GSK-3beta from a high-molecular-mass complex with a concomitant decrease in axin-bound GSK-3beta. These data imply that Wnt-regulated GSK-3beta plays a nonredundant role in trophic-deprivation-induced death of neurons.
authors.affiliation: Turku Centre for Biotechnology, Turku University and Abo Akademi University, BioCity, Tykistokatu 6, Turku FIN-20521, Finland.
authors.forename: Vesa
authors.initials: V
authors.lastname: Hongisto
authors.forename: Jenni C
authors.initials: JC
authors.lastname: Vainio
authors.forename: Róisín
authors.initials: R
authors.lastname: Thompson
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Courtney
authors.forename: Eleanor T
authors.initials: ET
authors.lastname: Coffey
mesh_terms: D000409:Alanine / Q000378:metabolism; D019943:Amino Acid Substitution; D000818:Animals; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D005786:Gene Expression Regulation; D005982:Glutathione Transferase / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D000071679:Glycogen Synthase Kinase 3 beta; D006720:Homozygote; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007668:Kidney / Q000166:cytology; D008094:Lithium / Q000494:pharmacology; D008301:Maleimides / Q000494:pharmacology; D051379:Mice; D009474:Neurons / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D010766:Phosphorylation; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D051153:Wnt Proteins / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D005231:Fatty Acids, Unsaturated; D007211:Indoles; D008301:Maleimides; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; C417521:SB 216763; D051153:Wnt Proteins; D008094:Lithium; D005982:Glutathione Transferase; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; C000605508:Gsk3b protein, rat; D038362:Glycogen Synthase Kinase 3; D000409:Alanine; C038753:leptomycin B