Protein kinase CK2 in postsynaptic densities: phosphorylation of PSD-95/SAP90 and NMDA receptor regulation.
Protein kinase CK2 (CK2) is highly expressed in rat forebrain where its function is not well understood. Subcellular distribution studies showed that the catalytic subunit of CK2 (CK2alpha) was enriched in postsynaptic densities (PSDs) by 68%. We studied the putative role of CK2 activity on N-methyl-D-aspartate receptor (NMDAR) function using isolated, patch-clamped PSDs in the presence of 2 mM extracellular Mg(2+). The usual activation by phosphorylation of the NMDARs in the presence of ATP was inhibited by the selective CK2 inhibitor 5,6-dichloro-1-beta-ribofuranosyl benzimidazole (DRB). This inhibition was voltage-dependent, i.e., 100% at positive membrane potentials, while at negative potentials, inhibition was incomplete. Endogenous CK2 substrates were characterized by their ability to use GTP as a phosphoryl donor and susceptibility to inhibition by DRB. Immunoprecipitation assays and 2D gels indicated that PSD-95/SAP90, the NMDAR scaffolding protein, was a CK2 substrate, while the NR2A/B and NR1 NMDAR subunits were not. These results suggest that postsynaptic NMDAR regulation by CK2 is mediated by indirect mechanisms possibly involving PSD-95/SAP90.
Neuroscience Laboratory, Faculty of Medicine, Universidad de Los Andes, Santiago-6782468, Chile.
Dagoberto
D
Soto
Floria
F
Pancetti
Juan José
JJ
Marengo
Mauricio
M
Sandoval
Rodrigo
R
Sandoval
Fernando
F
Orrego
Ursula
U
Wyneken
D000818:Animals; D047390:Casein Kinase II; D000076122:Disks Large Homolog 4 Protein; D047908:Intracellular Signaling Peptides and Proteins; D008274:Magnesium / Q000378:metabolism; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D000074407:SAP90-PSD95 Associated Proteins
D000076122:Disks Large Homolog 4 Protein; C501449:Dlg4 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D016194:Receptors, N-Methyl-D-Aspartate; D000074407:SAP90-PSD95 Associated Proteins; C033652:postsynaptic density proteins; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; D008274:Magnesium