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.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Active Transport, Cell Nucleus / drug effects
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Active Transport, Cell Nucleus / physiology*
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Animals
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Animals, Newborn
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Apoptosis / drug effects
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Apoptosis / physiology*
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Brain / cytology
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Brain / enzymology*
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Brain / growth & development*
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Calcium-Calmodulin-Dependent Protein Kinases / drug effects
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Calcium-Calmodulin-Dependent Protein Kinases / metabolism*
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Cell Compartmentation / drug effects
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Cell Compartmentation / physiology
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Cell Nucleus / drug effects
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Cell Nucleus / enzymology
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Cell Nucleus / ultrastructure
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Cytoplasm / drug effects
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Cytoplasm / enzymology
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Cytoplasm / ultrastructure
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Cytoskeleton / drug effects
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Cytoskeleton / metabolism
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Excitatory Amino Acid Antagonists / pharmacology
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Female
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Glycogen Synthase Kinase 3
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Glycogen Synthase Kinases
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Male
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Nerve Degeneration / chemically induced
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Nerve Degeneration / metabolism
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Nerve Degeneration / physiopathology
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Neurons / cytology
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Neurons / drug effects
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Neurons / enzymology*
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Peptide Fragments / drug effects
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Peptide Fragments / metabolism
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Phosphorylation / drug effects
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Rats
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Rats, Wistar
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Receptors, N-Methyl-D-Aspartate / antagonists & inhibitors
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Receptors, N-Methyl-D-Aspartate / metabolism
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Stress, Physiological / chemically induced
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Stress, Physiological / enzymology
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Stress, Physiological / physiopathology
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tau Proteins / drug effects
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tau Proteins / metabolism*
Substances
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Excitatory Amino Acid Antagonists
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Peptide Fragments
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Receptors, N-Methyl-D-Aspartate
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tau Proteins
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Glycogen Synthase Kinases
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Calcium-Calmodulin-Dependent Protein Kinases
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Glycogen Synthase Kinase 3