N-Methyl d-Aspartate Receptor-mediated Bidirectional Control of Extracellular Signal-regulated Kinase Activity in Cortical Neuronal Cultures

Abstract

, and PP2B did not prevent the inhibitory effect of NMDA. In the presence of tetrodotoxin, NMDA produced a bell-shaped dose-response curve with stimulation of phospho-ERK2 at 10, 25, and 50 M NMDA and reduced stimulation at 100 M NMDA. NMDA (50 M) stimulation of phospho-ERK2 was completely blocked by pertussis toxin and inhibitors of phosphatidylinositol 3-kinase and was partially blocked by a calcium/calmodulin-dependent kinase II inhibitor. These results suggests that NMDA receptors can bidirectionally control ERK signaling.Mitogen-activated protein kinases constitute a family of serine/threonine kinases, the best understood of which are the extracellular signal-regulated kinases (ERKs 1 ; Ref. 1). Ras proteins belong to a superfamily of small GTPases that cycle between inactive GDP-bound states and active GTP-bound states, and represent a point of convergence for the transduction and integration of many extracellular signals that activate mitogen-activated protein kinases (2). Ras-GTP initiates a sequential cascade of events involving recruitment to the membrane and activation of Raf-1, activation of the dual-specificity kinases termed mitogen-activated protein kinase/ERK kinases (MEKs), and finally activation of ERK. Activated ERKs phosphorylate cellular substrates and translocate to the nucleus, where they play an important role in regulating gene transcription (3, 4). In mitotic cells, ERKs constitute a primary effector pathway in controlling cellular proliferation, differentiation, cell cycle regulation, and survival. In brain, recent studies indicate that ERKs play an important role in synaptic plasticity and memory formation (5). Glutamate is the major excitatory neurotransmitter in the vertebrate brain, and the NMDA subtype of glutamate receptors are among the most widely distributed and abundant receptor-operated ion channels in the central nervous system. In addition to mediating the slow component of glutamate-dependent excitatory postsynaptic currents, NMDA receptors play a vital role in a variety of processes, including neuronal development, synaptic plasticity, learning and memory, and neuronal survival and death (6). NMDA receptor-mediated increases in intracellular calcium have been shown to stimulate ERK signaling, and evidence suggests that NMDA receptormediated ERK activation may play an important role in neurotransmission and synaptic plasticity (7,8). NMDA-dependent hippocampal long-term potentiation is associated with activation of ERK and is blocked by compounds that inhibit the ability of MEK to activate ERK (9, 10). ERK activation has also been shown to be required for hippocampal-dependent associative learning in rats (11), and mice lacking Ras-guanine nucleotide-releasing factor (Ras-GRF) display impaired amygdaladependent memory consolidation (12).

Mice lacking the AMPA GluR1 receptor exhibit striatal hyperdopaminergia and ‘schizophrenia-related’ behaviors

“…One potential explanation is that this reflects an important mechanistic role for GluR1 in a downstream intracellular signaling pathway mediating the locomotor-stimulant effects of MK-801. However, this pathway has not been fully elucidated 52 and further studies will serve to delineate fully the nature of altered NMDA receptor function in GluR1 KO.…”

NMDA Receptor Function and NMDA Receptor-Dependent Phosphorylation of Huntingtin Is Altered by the Endocytic Protein HIP1

“…Recent evidence suggests that this dualistic nature of NMDARs is mostly dependent on their localization at synaptic and extrasynaptic sites and associated with different electrophysiological properties, altered protein composition, and initiation of distinct signaling pathways (Li et al, 1998Tovar and Westbrook, 1999;. For example, activation of synaptic NMDARs promotes neuronal survival through activation of phosphoinositide 3-kinase (PI3K)/Akt and Ras/ ERK pathways leading to CREB activation and BDNF gene expression (Chandler et al, 2001;Perkinton et al, 2002;Lee et al, 2005;Papadia et al, 2005). In contrast, activation of extrasynaptic NMDARs is coupled to loss of mitochondrial membrane potential and inhibition of PI3K/Akt and Ras/ERK, as part of a dominant CREB shut-off pathway triggering cell death (Chalecka-Franaszek and Chuang, 1999;Hardingham, 2006).…”

Interleukin-1β impairs brain derived neurotrophic factor-induced signal transduction

“…Rat recombinant IL-1β (Sigma, St. Louis, MO) was dissolved in DMEM and used after one freeze-thaw cycle. Cells were treated with tetrodoxin (TTX, 1 μM) and amino-5-phosphonovaleric acid (100 μM), respectively 2 h and 30 min before exposure to IL-1β to reduce endogenous synaptic activity and to block glutamate release induced by BDNF [34,51] in order to reduce the basal level of activated signaling molecules [12]. The IL-1 receptor antagonist IL-1ra (R&D Systems, Minneapolis, MN) was used at 5 μg/ml, and when applied, cells were preincubated for 30 min before the addition of IL-1β.…”