Separate intramolecular targets for protein kinase A control N-methyl-D-aspartate receptor gating and Ca2+ permeability.
Protein kinase A (PKA) enhances synaptic plasticity in the central nervous system by increasing NMDA receptor current amplitude and Ca(2+) flux in an isoform-dependent yet poorly understood manner. PKA phosphorylates multiple residues on GluN1, GluN2A, and GluN2B subunits in vivo, but the functional significance of this multiplicity is unknown. We examined gating and permeation properties of recombinant NMDA receptor isoforms and of receptors with altered C-terminal domain (CTDs) prior to and after pharmacological inhibition of PKA. We found that PKA inhibition decreased GluN1/GluN2B but not GluN1/GluN2A gating; this effect was due to slower rates for receptor activation and resensitization and was mediated exclusively by the GluN2B CTD. In contrast, PKA inhibition reduced NMDA receptor-relative Ca(2+) permeability (PCa/PNa) regardless of the GluN2 isoform and required the GluN1 CTD; this effect was due primarily to decreased unitary Ca(2+) conductance, because neither Na(+) conductance nor Ca(2+)-dependent block was altered substantially. Finally, we show that both the gating and permeation effects can be reproduced by changing the phosphorylation state of a single residue: GluN2B Ser-1166 and GluN1 Ser-897, respectively. We conclude that PKA effects on NMDA receptor gating and Ca(2+) permeability rely on distinct phosphorylation sites located on the CTD of GluN2B and GluN1 subunits. This separate control of NMDA receptor properties by PKA may account for the specific effects of PKA on plasticity during synaptic development and may lead to drugs targeted to alter NMDA receptor gating or Ca(2+) permeability.
From the Department of Biochemistry.
Teresa K
TK
Aman
From the Department of Biochemistry, Neuroscience Program, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York 14214.
Bruce A
BA
Maki
From the Department of Biochemistry.
Thomas J
TJ
Ruffino
From the Department of Biochemistry.
Eileen M
EM
Kasperek
From the Department of Biochemistry, Neuroscience Program, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York 14214 popescu@buffalo.edu.
Gabriela K
GK
Popescu
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D055724:Electrophysiological Phenomena / Q000187:drug effects; D057809:HEK293 Cells; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects; D010539:Permeability / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000737:chemistry / Q000378:metabolism*; D012694:Serine / Q000378:metabolism
D047428:Protein Kinase Inhibitors; D021122:Protein Subunits; D016194:Receptors, N-Methyl-D-Aspartate; D012694:Serine; D017868:Cyclic AMP-Dependent Protein Kinases; D002118:Calcium
Calcium Signaling; Ionotropic Glutamate Receptor; Neurotransmitter Receptor; Permeation Mechanism; Protein Phosphorylation; Reaction Mechanism; Receptor Desensitization; Single-channel Kinetics; cAMP Protein Kinase