Glutamatergic Regulation of the p70S6 Kinase in Primary Mouse Neurons

• Published in: The Journal of biological chemistry 2005-11, Vol.280 (46), p.38121-38124
• Main Authors: Lenz, Guido, Avruch, Joseph
• Format: Article
• Language: English
• Subjects: 2-Amino-5-phosphonovalerate - pharmacology; 4-Aminopyridine - chemistry; Animals; Bicuculline - metabolism; Calcium - metabolism; Calcium Channels - metabolism; Calcium Channels, L-Type - metabolism; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Calcium-Calmodulin-Dependent Protein Kinases - metabolism; Cells, Cultured; Dopamine - pharmacology; gamma-Aminobutyric Acid - metabolism; Glutamine - metabolism; Mice; Mitogen-Activated Protein Kinase 1 - metabolism; Mitogen-Activated Protein Kinase 3 - metabolism; Neurons - metabolism; Norepinephrine - pharmacology; Peptide Elongation Factor 2 - metabolism; Phosphatidylinositol 3-Kinases - metabolism; Phosphorylation; Potassium Channels - metabolism; Protein Kinases - physiology; Ribosomal Protein S6 Kinases, 70-kDa - metabolism; Ribosomal Protein S6 Kinases, 70-kDa - physiology; RNA, Messenger - metabolism; Signal Transduction; Sirolimus - metabolism; Synapses - metabolism; Time Factors; TOR Serine-Threonine Kinases
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.C500363200

Brief glutamatergic stimulation of neurons from fetal mice, cultured in vitro for 6 days, activates the mTOR-S6 kinase, ERK1/2 and Akt pathways, to an extent approaching that elicited by brain-derived neurotrophic factor. In contrast, sustained glutamatergic stimulation inhibits ERK, Akt, and S6K. Glutamatergic activation of S6K is calcium/calmodulin-dependent and is prevented by inhibitors of calcium/calmodulin-dependent protein kinase 2, phosphatidylinositol 3-OH-kinase and by rapamycin. 2-Amino-5-phosphonovaleric acid, an inhibitor of N′-methyl-D-aspartate receptors, abolishes glutamatergic activation of ERK1/2 but not the activation of mTOR-S6K; the latter is completely abolished by inhibitors of voltage-dependent calcium channels. Added singly, dopamine gives slight, and norepinephrine a more significant, activation of ERK and S6K; both catecholeamines, however, enhance glutamatergic activation of S6K but not ERK. After 12 days in culture, the response to direct glutamatergic activation is attenuated but can be uncovered by suppression of γ-aminobutyric acid interneurons with bicuculline in the presence of the weak K+ channel blocker 4-aminopyridine (4-AP). This selective synaptic activation of mTOR-S6K is also resistant to APV and inhibited by Ca2+ channel blockers and higher concentrations of glutamate. Elongation factor 2 (EF2) is phosphorylated and inhibited by the eEF2 kinase (CaM kinase III); the latter is inhibited by the S6K or Rsk. Bicuculline/4-AP or KCl-induced depolarization reduces, whereas higher concentrations of glutamate increases, EF2 phosphorylation. Thus the mTOR-S6K pathway in neurons, a critical component of the late phase of LTP, is activated by glutamatergic stimulation in a calcium/calmodulin-dependent fashion through a calcium pool controlled by postsynaptic voltage-dependent calcium channels, whereas sustained stimulation of extrasynaptic glutamate receptors is inhibitory.