Dual role of CaMKII-dependent SAP97 phosphorylation in mediating trafficking and insertion of NMDA receptor subunit NR2A.
Synapse Associated Protein 97 (SAP97), a member of membrane-associated guanylate kinase (MAGUK) protein family, has been involved in the correct targeting and clustering of ionotropic glutamate receptors (iGluRs) at postsynaptic sites. Calcium/calmodulin kinase II (CaMKII) phosphorylates SAP97 on two major sites in vivo; one located in the N-terminal domain (Ser39) and the other in the first postsynaptic density disc large ZO1 (PDZ) domain (Ser232). CaMKII-mediated phosphorylation of SAP97-Ser39 is necessary and sufficient to drive SAP97 to the postsynaptic compartment in cultured hippocampal neurons. CaMKII-dependent phosphorylation of Ser232 disrupts SAP97 interaction with NR2A subunit, thereby regulating synaptic targeting of this NMDA receptor subunit. Here we show by means of phospho-specific antibodies that SAP97-Ser39 phosphorylation represents the driving force to release SAP97/NR2A complex from the endoplasmic reticulum. Ser39 phosphorylation does not interfere with SAP97 capability to bind NR2A. On the contrary, SAP97-Ser232 phosphorylation occurs within the postsynaptic compartment and is responsible for both the disruption of NR2A/SAP97 complex and, consequently, for NR2A insertion in the postsynaptic membrane. Thus, CaMKII-dependent phosphorylation of SAP97 in different time frames and locations within the neurons controls both NR2A trafficking and insertion.
Mauceri
D
D
Department of Pharmacological Sciences and Centre of Excellence on Neurodegenerative Diseases, University of Milan, Milan, Italy.
Gardoni
F
F
Marcello
E
E
Di Luca
M
M
D048868:Adaptor Proteins, Signal Transducing / Q000502:physiology*; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000494:pharmacology*; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D004347:Drug Interactions; D004622:Embryo, Mammalian; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology; D047468:Immunoprecipitation / Q000379:methods; D066298:In Vitro Techniques; D008565:Membrane Proteins / Q000502:physiology*; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D014162:Transfection / Q000379:methods
D048868:Adaptor Proteins, Signal Transducing; C501119:Dlg1 protein, rat; D018690:Excitatory Amino Acid Agonists; D008565:Membrane Proteins; C120997:NR2A NMDA receptor; D010726:Phosphodiesterase Inhibitors; D016194:Receptors, N-Methyl-D-Aspartate; D002110:Caffeine; D012694:Serine; D016202:N-Methylaspartate; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases