title: NMDA receptor-dependent regulation of dendritic spine morphology by SAP102 splice variants.
abstract: Membrane-associated guanylate kinases (MAGUKs) are major components of the postsynaptic density and play important roles in synaptic organization and plasticity. Most excitatory synapses are located on dendritic spines, which are dynamic structures that undergo morphological changes during synapse formation and plasticity. Synapse-associated protein 102 (SAP102) is a MAGUK that is highly expressed early in development and mediates receptor trafficking during synaptogenesis. Mutations in human SAP102 cause mental retardation, which is often accompanied with abnormalities in dendritic spines. However, little is known about the role of SAP102 in regulating synapse formation or spine morphology. We now find that SAP102 contains a novel NMDA receptor binding site in the N-terminal domain, which is specific for the NR2B subunit. The interaction between SAP102 and NR2B is PDZ (postsynaptic density-95/Discs large/zona occludens-1) domain independent and is regulated by alternative splicing of SAP102. We show that SAP102 that possesses an N-terminal insert is developmentally regulated at both mRNA and protein levels. In addition, expression of SAP102 increases synapse formation. Furthermore, the alternative splicing of SAP102 regulates dendritic spine morphology. SAP102 containing the N-terminal insert promotes lengthening of dendritic spines and preferentially promotes the formation of synapses at long spines, whereas a short hairpin RNA knockdown of the same SAP102 splice variant causes spine shrinkage. Finally, blocking NMDA receptor activity prevents the spine lengthening induced by the N-terminal splice variant of SAP102. Thus, our data provide the first evidence that SAP102 links NMDA receptor activation to alterations in spine morphology.
authors.affiliation: Receptor Biology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA. bochen@mcg.edu
authors.forename: Bo-Shiun
authors.initials: BS
authors.lastname: Chen
authors.forename: Eleanor V
authors.initials: EV
authors.lastname: Thomas
authors.forename: Antonio
authors.initials: A
authors.lastname: Sanz-Clemente
authors.forename: Katherine W
authors.initials: KW
authors.lastname: Roche
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002478:Cells, Cultured; D049229:Dendritic Spines / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D004622:Embryo, Mammalian; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D066298:In Vitro Techniques; D018613:Microscopy, Confocal; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000648:ultrastructure*; D009479:Neuropeptides / Q000235:genetics*; D057907:Post-Synaptic Density / Q000187:drug effects / Q000235:genetics*; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics*; D021381:Protein Transport / Q000187:drug effects / Q000235:genetics; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000235:genetics / Q000378:metabolism*; D014162:Transfection / Q000379:methods; D020798:Two-Hybrid System Techniques; D014633:Valine / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: C101195:Dlg3 protein, rat; D018691:Excitatory Amino Acid Antagonists; C121001:NR2B NMDA receptor; D009419:Nerve Tissue Proteins; D009479:Neuropeptides; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D016194:Receptors, N-Methyl-D-Aspartate; C033652:postsynaptic density proteins; D049452:Green Fluorescent Proteins; C056639:2-amino-5-phosphopentanoic acid; D014633:Valine