title: In vivo activation and nuclear translocation of phosphorylated glycogen synthase kinase-3beta in neuronal apoptosis: links to tau phosphorylation.
abstract: The roles of glycogen synthase kinase-3beta (GSK-3beta) and tau phosphorylation were examined in seven-day-old rats injected with the NMDA receptor antagonist (MK801) that is known to induce neuronal apoptosis. Immunoblot and immunohistochemical analysis of brain samples demonstrated a site-specific increase in tau phosphorylation associated with the relocalization of the protein to the nuclear/perinuclear region of apoptotic neurons. In addition, a tau 32-kDa fragment was detected, suggesting that tau was a target of intracellular proteolysis in MK801-treated brains. The proteolytically modified form of tau has reduced ability to bind to microtubules. GSK-3beta kinase assay and immunoblottings of active (tyrosine-216) and inactive (serine-9) forms of GSK-3beta revealed a rapid and transient increase in the kinase activity. Lithium chloride, a GSK-3beta inhibitor, prevented tau phosphorylation suggesting that tau phosphorylation is mediated by the activation of GSK-3beta. Confocal microscopy using double labelling of tau and GSK-3beta revealed that the activation of GSK-3beta in neurons was associated with early (2 h) nuclear translocation of tyrosine-216 GSK-3beta. The execution phase of neuronal apoptosis was accompanied by a selective phosphorylation of serine-9 and dephosphorylation of tyrosine-216 GSK-3beta. These findings demonstrate that in vivo, GSK-3beta kinase activation and nuclear translocation are early stress signals of neuronal apoptosis.
authors.affiliation: Department of Anatomy, Faculty of Medicine, The University of Hong Kong, Hong Kong, SAR.
authors.forename: W
authors.initials: W
authors.lastname: Elyaman
authors.forename: F
authors.initials: F
authors.lastname: Terro
authors.forename: N S
authors.initials: NS
authors.lastname: Wong
authors.forename: J
authors.initials: J
authors.lastname: Hugon
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001921:Brain / Q000166:cytology / Q000201:enzymology* / Q000254:growth & development*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D002451:Cell Compartmentation / Q000187:drug effects / Q000502:physiology; D002467:Cell Nucleus / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure; D003593:Cytoplasm / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D008297:Male; D009410:Nerve Degeneration / Q000139:chemically induced / Q000378:metabolism / Q000503:physiopathology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D010446:Peptide Fragments / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000378:metabolism; D013312:Stress, Physiological / Q000139:chemically induced / Q000201:enzymology / Q000503:physiopathology; D016875:tau Proteins / Q000187:drug effects / Q000378:metabolism*
chemical_list: D018691:Excitatory Amino Acid Antagonists; D010446:Peptide Fragments; D016194:Receptors, N-Methyl-D-Aspartate; D016875:tau Proteins; D038341:Glycogen Synthase Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3