The Wnt pool of glycogen synthase kinase 3beta is critical for trophic-deprivation-induced neuronal death

Mol Cell Biol. 2008 Mar;28(5):1515-27. doi: 10.1128/MCB.02227-06. Epub 2008 Jan 14.

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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alanine / metabolism
  • Amino Acid Substitution
  • Animals
  • Cell Death* / drug effects
  • Cell Line
  • Enzyme Inhibitors / pharmacology
  • Fatty Acids, Unsaturated / pharmacology
  • Gene Expression Regulation
  • Glutathione Transferase / metabolism
  • Glycogen Synthase Kinase 3 / antagonists & inhibitors
  • Glycogen Synthase Kinase 3 / genetics
  • Glycogen Synthase Kinase 3 / metabolism*
  • Glycogen Synthase Kinase 3 / physiology
  • Glycogen Synthase Kinase 3 beta
  • Homozygote
  • Humans
  • Indoles / pharmacology
  • Kidney / cytology
  • Lithium / pharmacology
  • Maleimides / pharmacology
  • Mice
  • Neurons / cytology*
  • Neurons / drug effects
  • Neurons / enzymology*
  • Phosphorylation
  • RNA, Small Interfering / pharmacology
  • Rats
  • Rats, Sprague-Dawley
  • Recombinant Proteins / metabolism
  • Time Factors
  • Transfection
  • Wnt Proteins / metabolism*

Substances

  • Enzyme Inhibitors
  • Fatty Acids, Unsaturated
  • Indoles
  • Maleimides
  • RNA, Small Interfering
  • Recombinant Proteins
  • SB 216763
  • Wnt Proteins
  • Lithium
  • Glutathione Transferase
  • GSK3B protein, human
  • Glycogen Synthase Kinase 3 beta
  • Gsk3b protein, mouse
  • Gsk3b protein, rat
  • Glycogen Synthase Kinase 3
  • Alanine
  • leptomycin B