Quaternary Structure, Protein Dynamics, and Synaptic Function of SAP97 Controlled by L27 Domain Interactions

• Published in: Neuron (Cambridge, Mass.) Mass.), 2004-10, Vol.44 (3), p.453-467
• Main Authors: Nakagawa, Terunaga, Futai, Kensuke, Lashuel, Hilal A., Lo, Irene, Okamoto, Kenichi, Walz, Thomas, Hayashi, Yasunori, Sheng, Morgan
• Format: Article
• Language: English
• Subjects: Adaptor Proteins, Signal Transducing; Analysis of Variance; Animals; Baculoviridae - physiology; Biophysics - methods; Brain - cytology; Cells, Cultured; Chromatography, Gel - methods; Dendritic Spines - metabolism; Discs Large Homolog 1 Protein; Disks Large Homolog 4 Protein; Excitatory Amino Acid Agonists - pharmacology; Excitatory Amino Acid Antagonists - pharmacology; Excitatory Postsynaptic Potentials - genetics; Experiments; Gene Expression Regulation - physiology; Genetic Vectors; Guanylate Kinases; Humans; Immunohistochemistry - methods; In Vitro Techniques; Insecta; Intracellular Signaling Peptides and Proteins; Kinases; Lentivirus - genetics; Long-Term Potentiation - genetics; Medical research; Membrane Proteins; Mice; Microscopy, Confocal - methods; Microscopy, Electron, Scanning - methods; Microscopy, Energy-Filtering Transmission Electron - methods; Molecular weight; Mutagenesis; N-Methylaspartate - pharmacology; Nerve Tissue Proteins - chemistry; Nerve Tissue Proteins - metabolism; Nerve Tissue Proteins - physiology; Nerve Tissue Proteins - ultrastructure; Neurons; Neurons - cytology; Neurons - physiology; Patch-Clamp Techniques - methods; Protein Structure, Tertiary - physiology; Proteins; Rats; Receptors, AMPA - metabolism; Receptors, AMPA - physiology; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; RNA, Antisense - metabolism; RNA, Small Interfering; Sequence Alignment - methods; Synapses - physiology; Synaptic Transmission - physiology; Time Factors; Transfection - methods; Valine - analogs & derivatives; Valine - pharmacology
• ISSN: 0896-6273; 1097-4199
• DOI: 10.1016/j.neuron.2004.10.012

Single-particle electron microscopy (EM) combined with biochemical measurements revealed the molecular shape of SAP97 and a monomer-dimer transition that depended on the N-terminal L27 domain. Overexpression of SAP97 drove GluR1 to synapses, potentiated AMPA receptor (AMPAR) excitatory postsynaptic currents (EPSCs), and occluded LTP. Synaptic potentiation and GluR1 delivery were dissociable by L27 domain mutants that inhibit multimerization of SAP97. Loss of potentiation was correlated with faster turnover of monomeric SAP97 mutants in dendritic spines. We propose that L27-mediated interactions of SAP97 with itself or other proteins regulate the synaptic delivery of AMPARs. RNAi knockdown of endogenous PSD-95 depleted surface GluR1 and impaired AMPA EPSCs. In contrast, RNAi knockdown of endogenous SAP97 reduced surface expression of both GluR1 and GluR2 and inhibited both AMPA and NMDA EPSCs. Thus SAP97 has a broader role than its close relative, PSD-95, in the maintenance of synaptic function.