Postsynaptic density 95 (PSD-95) serine 561 phosphorylation regulates a conformational switch and bidirectional dendritic spine structural plasticity

J Biol Chem. 2017 Sep 29;292(39):16150-16160. doi: 10.1074/jbc.M117.782490. Epub 2017 Aug 8.


Postsynaptic density 95 (PSD-95) is a major synaptic scaffolding protein that plays a key role in bidirectional synaptic plasticity, which is a process important for learning and memory. It is known that PSD-95 shows increased dynamics upon induction of plasticity. However, the underlying structural and functional changes in PSD-95 that mediate its role in plasticity remain unclear. Here we show that phosphorylation of PSD-95 at Ser-561 in its guanylate kinase (GK) domain, which is mediated by the partitioning-defective 1 (Par1) kinases, regulates a conformational switch and is important for bidirectional plasticity. Using a fluorescence resonance energy transfer (FRET) biosensor, we show that a phosphomimetic mutation of Ser-561 promotes an intramolecular interaction between GK and the nearby Src homology 3 (SH3) domain, leading to a closed conformation, whereas a non-phosphorylatable S561A mutation or inhibition of Par1 kinase activity decreases SH3-GK interaction, causing PSD-95 to adopt an open conformation. In addition, S561A mutation facilitates the interaction between PSD-95 and its binding partners. Fluorescence recovery after photobleaching imaging reveals that the S561A mutant shows increased stability, whereas the phosphomimetic S561D mutation increases PSD-95 dynamics at the synapse. Moreover, molecular replacement of endogenous PSD-95 with the S561A mutant blocks dendritic spine structural plasticity during chemical long-term potentiation and long-term depression. Endogenous Ser-561 phosphorylation is induced by synaptic NMDA receptor activation, and the SH3-GK domains exhibit a Ser-561 phosphorylation-dependent switch to a closed conformation during synaptic plasticity. Our results provide novel mechanistic insight into the regulation of PSD-95 in dendritic spine structural plasticity through phosphorylation-mediated regulation of protein dynamics and conformation.

Keywords: PSD-95; conformational change; dendritic spine; fluorescence resonance energy transfer (FRET); phosphorylation; synaptic plasticity.

MeSH terms

  • Amino Acid Substitution
  • Animals
  • Cells, Cultured
  • Dendrites / drug effects
  • Dendrites / metabolism*
  • Disks Large Homolog 4 Protein
  • Embryo, Mammalian / cytology
  • Hippocampus / cytology
  • Hippocampus / drug effects
  • Hippocampus / metabolism*
  • Intracellular Signaling Peptides and Proteins / antagonists & inhibitors
  • Intracellular Signaling Peptides and Proteins / chemistry
  • Intracellular Signaling Peptides and Proteins / genetics
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Membrane Proteins / antagonists & inhibitors
  • Membrane Proteins / chemistry
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Models, Molecular*
  • Mutation
  • Nerve Tissue Proteins / antagonists & inhibitors
  • Nerve Tissue Proteins / chemistry
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism
  • Neuronal Plasticity / drug effects
  • Neurons / cytology
  • Neurons / drug effects
  • Neurons / metabolism*
  • Peptide Fragments / antagonists & inhibitors
  • Peptide Fragments / chemistry
  • Peptide Fragments / genetics
  • Peptide Fragments / metabolism
  • Phosphorylation / drug effects
  • Protein Conformation
  • Protein Interaction Domains and Motifs
  • Protein Kinase Inhibitors / pharmacology
  • Protein Processing, Post-Translational* / drug effects
  • Protein Serine-Threonine Kinases / antagonists & inhibitors
  • Protein Serine-Threonine Kinases / metabolism*
  • RNA Interference
  • Rats
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / metabolism
  • Serine / metabolism


  • Disks Large Homolog 4 Protein
  • Dlg4 protein, rat
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Nerve Tissue Proteins
  • Peptide Fragments
  • Protein Kinase Inhibitors
  • Recombinant Fusion Proteins
  • Serine
  • F2r protein, rat
  • Protein Serine-Threonine Kinases