N-Methyl-D-aspartate and Brain-Derived Neurotrophic Factor Induce Distinct Profiles of Extracellular Signal-Regulated Kinase, Mitogen- and Stress-Activated Kinase, and Ribosomal S6 Kinase Phosphorylation in Cortical Neurons

Abstract

Stimulation of N-methyl-D-aspartate (NMDA) receptors is believed to underlie long-term memory formation, and excessive NMDA receptor activation has been linked to several neuropathological conditions. Phosphorylation and activation of p42/44 mitogen-activated protein kinase (ERK) is believed to mediate many of these effects, but the downstream targets of ERK in response to NMDA activation have not been determined. In primary cultures of rat cortical neurons, we found that NMDA was able to elevate phosphorylation of mitogen-and stress-activated kinase 1 (MSK1) as well as ERK. Likewise, brain-derived neurotrophic factor (BDNF) treatment increased phosphorylation of MSK1 and ERKs. The NMDA-induced MSK1 phosphorylation was sensitive to the MEK inhibitor 2Ј-amino-3Ј-methoxyflavone (PD98059) and the p38 inhibitor 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole (SB203580). MSK1 activation by NMDA was transient, although ERK remained phosphorylated within the neuronal cytoplasm for several hours. Although BDNF increased ribosomal S6 kinase (RSK) phosphorylation, NMDA had no discernable effect on the phosphorylation of RSKs. Thus, phosphorylation and activation of MSK1 but not RSK could be an important step in the pathway linking NMDA-induced ERK phosphorylation to the activation of transcription factors required for the formation of long-term memory.Activation of the N-methyl-D-aspartate (NMDA) class of ionotropic glutamate receptor is a key stimulus for the induction of long-term plasticity in neuronal cells. Stimulation of NMDA receptors in neurons not only underlies activitydependent changes in synaptic strength such as long-term potentiation (LTP) but is linked to pathological changes leading to neurotoxic damage, such as during stroke.The NMDA receptor is a ligand-gated sodium/calcium ion channel, and maximum ion flow requires the coincidence of both presynaptic activity, which releases glutamate to bind the receptor, and postsynaptic depolarization, which is needed to relieve blockade of the receptor channel by extracellular magnesium. Calcium entry leads to the activation of signaling intermediates such as protein kinase C, ERKs, and Ca 2ϩ /calmodulin-dependent kinases, which are necessary for LTP induction Sweatt, 1996, 1997;Morris, 2004). Activation of these pathways subsequently leads to phosphorylation of the transcription factor cAMP-response element binding protein (CREB), which, together with CREB-binding protein, may initiate transcription of immediate early genes required for LTP.The later phases of LTP are dependent on gene transcription and protein synthesis, and CREB has been implicated in mediating enhanced gene transcription in response to NMDA receptor stimulation (Impey et al., 1996(Impey et al., , 1998. However, the signaling pathways that link activation of NMDA receptors to phosphorylation of CREB have only begun to be understood. The best-characterized CREB kinases belong to the ribosomal S6 kinase (RSK) family, consisting of RSKs 1 to 4. The fact that phosph...

Role of MSK1 in the signaling pathway leading to VEGF‐mediated PAF synthesis in endothelial cells

“…These data are in agreement with previous studies, in which a similar MSK1 kinetic activation was observed upon stimulation of different cell types (Hela, SK-N-MC, PC12, cardiac myocytes and embryonic rat cortical cells) with various agonists including tumor necrosis factor, fibroblast growth factor, neuronal growth factor, endothelin-1, N-methyl-D-Aspartate and brain-derived neurotrophic factor [Deak et al, 1998;Markou and Lazou, 2002;Rakhit et al, 2005]. It has recently been defined that Thr 581 residue in the MSK1 C-terminal kinase domain is a prolinedirected site, which can be phosphorylated either by p38 or p42/44 MAPKs [McCoy et al, 2005].…”

A Role for RhoB in Synaptic Plasticity and the Regulation of Neuronal Morphology

“…Membrane-bound secondary antibodies were detected using the ECL Plus procedure developed by GE Healthcare Life Sciences. Integrative optical density readings were obtained using NIH Image (W. Rasband, National Institutes of Health, Bethesda, MD), and differences in specific density between RhoB ϩ/ϩ and mutant animals were analyzed for statistical significance as described (Rakhit et al, 2005;James et al, 2006). Where the number of samples was too great to be run on a single gel, band intensities were expressed as a percentage of the mean band intensity from the control RhoB ϩ/ϩ group on that gel.…”

Specificity and timing of neocortical transcriptome changes in response to BDNF gene ablation during embryogenesis or adulthood

“…48 IEG induction is known to be strongly regulated via the MEK-ERK pathway, 49,50 which is also one of the main effectors of BDNF signaling. 51,52 Hence, we propose that the IEG transcript downregulations we see in the BDNF-deficient animals are due to the lack of release of BDNF and impaired trophic support. 53,54 Second, the cyclin-dependent kinase inhibitor 1C (CDKN1c) and cyclin D2 (CCND2) also showed Figure 3 Expression changes specific for mice with the embryonic deletion of brain-derived neurotrophic factor (BDNF).…”