Stress increases addictive behaviors and is a common cause of relapse. Corticotropin-releasing factor (CRF) plays a key role in the modulation of drug taking by stress. However, the mechanism by which CRF modulates neuronal activity in circuits involved in drug addiction is poorly understood. Here we show that CRF induces a potentiation of NMDAR (N-methyl-D-aspartate receptor)-mediated synaptic transmission in dopamine neurons of the ventral tegmental area (VTA). This effect involves CRF receptor 2 (CRF-R2) and activation of the phospholipase C (PLC)-protein kinase C (PKC) pathway. We also find that this potentiation requires CRF binding protein (CRF-BP). Accordingly, CRF-like peptides, which do not bind the CRF-BP with high affinity, do not potentiate NMDARs. These results provide evidence of the first specific roles for CRF-R2 and CRF-BP in the modulation of neuronal activity and suggest that NMDARs in the VTA may be a target for both drugs of abuse and stress.
Phosphorylation regulates the function of ligand-gated ion channels such as the N-methyl D-aspartate (NMDA) receptor. Here we report a mechanism for modulation of the phosphorylation state and function of the NMDA receptor via an inhibitory scaffolding protein, RACK1. We found that RACK1 binds both the NR2B subunit of the NMDA receptor and the nonreceptor protein tyrosine kinase, Fyn. RACK1 inhibits Fyn phosphorylation of NR2B and decreases NMDA receptor-mediated currents in CA1 hippocampal slices. Peptides that disrupt the interactions between RACK1, NR2B, and Fyn induce phosphorylation and potentiate NMDA receptor-mediated currents. Therefore, RACK1 is a regulator of NMDA receptor function and may play a role in synaptic plasticity, addiction, learning, and memory.
A. 99, 5710 -5715). Here, we identified the signaling cascade by which RACK1 is released from the NMDA receptor complex and identified the consequences of the dissociation. We found that activation of the cAMP/protein kinase A pathway in hippocampal slices induced the release of RACK1 from NR2B and Fyn. This resulted in the induction of NR2B phosphorylation and the enhancement of NMDA receptor-mediated activity via Fyn. We identified the neuropeptide, pituitary adenylate cyclase activating polypeptide (PACAP(1-38)), as a ligand that induced phosphorylation of NR2B and enhanced NMDA receptor potentials. Finally, we found that activation of the cAMP/protein kinase A pathway induced the movement of RACK1 to the nuclear compartment in dissociated hippocampal neurons. Nuclear RACK1 in turn was found to regulate the expression of brain-derived neurotrophic factor induced by PACAP(1-38). Taken together our results suggest that activation of adenylate cyclase by PACAP(1-38) results in the release of RACK1 from the NMDA receptor and Fyn. This in turn leads to NMDA receptor phosphorylation, enhanced activity mediated by Fyn, and to the induction of brain-derived neurotrophic factor expression by RACK1. The ionotropic glutamate receptor subtype, N-methyl-D-as-1 plays an essential role in neuronal development, excitotoxicity, synaptic plasticity, and learning and memory (2). The ligand-gated NMDA receptor channel is a heteromer comprised of NR1 and at least one of four NR2 subunits (A-D) (3). The cytoplasmic tail of the NR2B subunit is phosphorylated on tyrosine residues (4) and is the most abundant tyrosine-phosphorylated protein in the postsynaptic density (5). Phosphorylation of NMDA receptor subunits regulates the activity of the channel (6). Specifically, application of a tyrosine kinase inhibitor causes a progressive decrease in NMDA receptor-mediated currents, and conversely, inhibition of protein-tyrosine phosphatases results in an increase in NMDA receptor-mediated currents (7). Subsequent studies have identified the Src family of protein-tyrosine kinases (PTKs) as enzymes that phosphorylate the NR2 subunits, regulating NMDA receptor activities (6 -8). Hence, modulation of NMDA receptor phosphorylation by Src family protein-tyrosine kinases is likely to play an important role in modulating glutamate-mediated pathways. In the recent years it has become increasingly apparent that the formation of localized signaling complexes, which include receptors, kinases, phosphatases and their substrates, are highly important for the regulation of signal transduction cascades (9, 10). Scaffolding proteins play a major role in the assembly of such signaling complexes (11). Recently, we identified the scaffolding protein RACK1 as a novel regulator of the phosphorylation state and function of the NMDA receptor. We found that RACK1 interacts with both the cytoplasmic tail of the NR2B subunit and Fyn and inhibits the ability of Fyn to phosphorylate the NR2B subunit and consequently inhibits NMDA receptor-mediated excitatory postsyna...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.