CaMKII-dependent Phosphorylation Regulates SAP97/NR2A Interaction

• Published in: The Journal of biological chemistry 2003-11, Vol.278 (45), p.44745-44752
• Main Authors: Gardoni, Fabrizio, Mauceri, Daniela, Fiorentini, Chiara, Bellone, Camilla, Missale, Cristina, Cattabeni, Flaminio, Luca, Monica Di
• Format: Article
• Language: English
• Subjects: Adaptor Proteins, Signal Transducing; Amino Acid Sequence; Animals; Benzylamines - pharmacology; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Calcium-Calmodulin-Dependent Protein Kinases - analysis; Calcium-Calmodulin-Dependent Protein Kinases - antagonists & inhibitors; Calcium-Calmodulin-Dependent Protein Kinases - metabolism; Cells, Cultured; COS Cells; Dendrites - chemistry; Embryo, Mammalian; Enzyme Inhibitors - pharmacology; Escherichia coli - genetics; Gene Expression; Hippocampus; Immunosorbent Techniques; Membrane Proteins; Mutagenesis, Site-Directed; N-Methylaspartate - pharmacology; Nerve Tissue Proteins - analysis; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - metabolism; Neurons - ultrastructure; Phosphorus Radioisotopes; Phosphorylation; Rats; Receptors, N-Methyl-D-Aspartate - analysis; Receptors, N-Methyl-D-Aspartate - metabolism; Recombinant Fusion Proteins; Structure-Activity Relationship; Sulfonamides - pharmacology; Synaptosomes - chemistry; Transfection
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M303576200

Synapse-associated protein 97 (SAP97), a member of membrane-associated guanylate kinase protein family, has been implicated in the processes of targeting ionotropic glutamate receptors at postsynaptic sites. Here we show that SAP97 is enriched at the postsynaptic density where it co-localizes with both ionotropic glutamate receptors and downstream signaling proteins such as Ca2+/calmodulin-dependent protein kinase II (CaMKII). SAP97 and αCaMKII display a high co-localization pattern in hippocampal neurons as well as in transfected COS-7 cells. Metabolic labeling of hippocampal cultures reveals that N-methyl-d-aspartic acid (NMDA) receptor activation induces CaMKII-dependent phosphorylation of SAP97; co-incubation with the CaMKII-specific inhibitor KN-93 reduces SAP97 phosphorylation to basal levels. Our results show that SAP97 directly interacts with the NR2A subunit of NMDA receptor both in an in vitro “pull-out” assay and in co-immunoprecipitation experiments from homogenates and synaptosomes purified from hippocampal rat tissue. Interestingly, in the postsynaptic density fraction, SAP97 fails to co-precipitate with NR2A. We show here that SAP97 is directly associated with NR2A through its PDZ1 domain, and CaMKII-dependent phosphorylation of SAP97-Ser-232 disrupts NR2A interaction both in an in vitro pull-out assay and in transfected COS-7 cells. Moreover, expression of SAP97(S232D) mutant has effects similar to those observed upon constitutively activating CaMKII. Our findings suggest that SAP97/NR2A interaction is regulated by CaMKII-dependent phosphorylation and provide a novel mechanism for the regulation of synaptic targeting of NMDA receptor subunits.