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Beta-adrenergic regulation of synaptic NMDA receptors by cAMP-dependent protein kinase
1Vollum Institute Oregon Health Sciences University, Portland 97201, USA.
Abstract:
To identify the protein kinases regulating synaptic NMDA receptors, as well as the conditions favoring enhancement of NMDA receptor-mediated excitatory postsynaptic currents (EPSCs) by phosphorylation, we studied the effects of kinase activation and inhibition in hippocampal neurons. Inhibition of cAMP-dependent protein kinase (PKA) prevented recovery of NMDA receptors from calcineurin-mediated dephosphorylation induced by synaptic activity, suggesting that tonically active PKA phosphorylates receptors during quiescent periods. Conversely, elevation of PKA activity by forskolin, cAMP analogs, or the beta-adrenergic receptor agonists norepinephrine and isoproterenol overcame the ability of calcineurin to depress the amplitude of NMDA EPSCs. Thus, stimulation of beta-adrenergic receptors during excitatory synaptic transmission can increase charge transfer and Ca2+ influx through NMDA receptors.
Insights
cAMP-dependent protein kinase (PKA) activity is crucial for synaptic NMDA receptor function. Beta-adrenergic receptor stimulation enhances NMDA receptor currents, increasing calcium influx during neuronal activity.
Area of Science:
- Neuroscience
- Molecular Biology
- Cellular Signaling
Background:
- Synaptic plasticity relies on the regulation of NMDA receptors.
- Protein phosphorylation plays a key role in modulating NMDA receptor function.
- Understanding kinase regulation is vital for comprehending synaptic transmission.
Purpose of the Study:
- To identify protein kinases that regulate synaptic NMDA receptors.
- To determine conditions that enhance NMDA receptor function via phosphorylation.
- To investigate the role of cAMP-dependent protein kinase (PKA) in NMDA receptor regulation.
Main Methods:
- Studied kinase activation and inhibition in hippocampal neurons.
- Utilized forskolin, cAMP analogs, and beta-adrenergic receptor agonists.
- Examined effects on NMDA receptor-mediated excitatory postsynaptic currents (EPSCs).
Main Results:
- Inhibition of PKA hindered NMDA receptor recovery from calcineurin-mediated dephosphorylation.
- Tonically active PKA appears to phosphorylate NMDA receptors during rest.
- Elevated PKA activity counteracted calcineurin's depressive effect on NMDA EPSCs.
Conclusions:
- PKA is a key regulator of synaptic NMDA receptor phosphorylation.
- Beta-adrenergic receptor stimulation enhances NMDA receptor activity and calcium influx.
- This mechanism contributes to increased charge transfer during excitatory synaptic transmission.