Cyclic AMP promotes neuronal survival by phosphorylation of glycogen synthase kinase 3beta.
Agents that elevate intracellular cyclic AMP (cAMP) levels promote neuronal survival in a manner independent of neurotrophic factors. Inhibitors of phosphatidylinositol 3 kinase and dominant-inactive mutants of the protein kinase Akt do not block the survival effects of cAMP, suggesting that another signaling pathway is involved. In this report, we demonstrate that elevation of intracellular cAMP levels in rat cerebellar granule neurons leads to phosphorylation and inhibition of glycogen synthase kinase 3beta (GSK-3beta). The increased phosphorylation of GSK-3beta by protein kinase A (PKA) occurs at serine 9, the same site phosphorylated by Akt. Purified PKA is able to phosphorylate recombinant GSK-3beta in vitro. Inhibitors of GSK-3 block apoptosis in these neurons, and transfection of neurons with a GSK-3beta mutant that cannot be phosphorylated interferes with the prosurvival effects of cAMP. These data suggest that activated PKA directly phosphorylates GSK-3beta and inhibits its apoptotic activity in neurons.
Li
M
M
Department of Pharmacology, University of Colorado Health Sciences Center, and The Denver Veterans Affairs Medical Center, Denver, Colorado 80220, USA.
Wang
X
X
Meintzer
M K
MK
Laessig
T
T
Birnbaum
M J
MJ
Heidenreich
K A
KA
D000818:Animals; D017209:Apoptosis; D001923:Brain Chemistry; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002458:Cell Fractionation; D002470:Cell Survival; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology; D005576:Colforsin / Q000494:pharmacology; D016895:Culture Media, Serum-Free; D000242:Cyclic AMP / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D015151:Immunoblotting; D007546:Isoquinolines / Q000494:pharmacology; D009474:Neurons / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013449:Sulfonamides; D014162:Transfection
D016895:Culture Media, Serum-Free; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007546:Isoquinolines; D047428:Protein Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D013449:Sulfonamides; D005576:Colforsin; D000242:Cyclic AMP; D038341:Glycogen Synthase Kinases; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one