title: Pin1 Modulates the Synaptic Content of NMDA Receptors via Prolyl-Isomerization of PSD-95.
abstract: Phosphorylation of serine/threonine residues preceding a proline regulates the fate of its targets through postphosphorylation conformational changes catalyzed by the peptidyl-prolyl cis-/trans isomerase Pin1. By flipping the substrate between two different functional conformations, this enzyme exerts a fine-tuning of phosphorylation signals. Pin1 has been detected in dendritic spines and shafts where it regulates protein synthesis required to sustain the late phase of long-term potentiation (LTP). Here, we demonstrate that Pin1 residing in postsynaptic structures can interact with postsynaptic density protein-95 (PSD-95), a key scaffold protein that anchors NMDA receptors (NMDARs) in PSD via GluN2-type receptor subunits. Pin1 recruitment by PSD-95 occurs at specific serine-threonine/proline consensus motifs localized in the linker region connecting PDZ2 to PDZ3 domains. Upon binding, Pin1 triggers structural changes in PSD-95, thus negatively affecting its ability to interact with NMDARs. In electrophysiological experiments, larger NMDA-mediated synaptic currents, evoked in CA1 principal cells by Schaffer collateral stimulation, were detected in hippocampal slices obtained from Pin1(-/-) mice compared with controls. Similar results were obtained in cultured hippocampal cells expressing a PSD-95 mutant unable to undergo prolyl-isomerization, thus indicating that the action of Pin1 on PSD-95 is critical for this effect. In addition, an enhancement in spine density and size was detected in CA1 principal cells of Pin1(-/-) or in Thy-1GFP mice treated with the pharmacological inhibitor of Pin1 catalytic activity PiB.Our data indicate that Pin1 controls synaptic content of NMDARs via PSD-95 prolyl-isomerization and the expression of dendritic spines, both required for LTP maintenance.
  
  
  
  PSD-95, a membrane-associated guanylate kinase, is the major scaffolding protein at excitatory postsynaptic densities and a potent regulator of synaptic strength and plasticity. The activity of PSD-95 is tightly controlled by several post-translational mechanisms including proline-directed phosphorylation. This signaling cascade regulates the fate of its targets through postphosphorylation conformational modifications catalyzed by the peptidyl-prolyl cis-/trans isomerase Pin1. Here, we uncover a new role of Pin1 in glutamatergic signaling. By interacting with PSD-95, Pin1 dampens PSD-95 ability to complex with NMDARs, thus negatively affecting NMDAR signaling and spine morphology. Our findings further emphasize the emerging role of Pin1 as a key modulator of synaptic transmission.
authors.affiliation: International School for Advanced Studies, 34136 Trieste, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Antonelli
authors.affiliation: International School for Advanced Studies, 34136 Trieste, Italy.
authors.forename: Roberto
authors.identifier: 0000-0002-9382-0053
authors.initials: R
authors.lastname: De Filippo
authors.affiliation: National Research Council Institute of Cell Biology and Neurobiology, Santa Lucia Foundation, 00143 Rome, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Middei
authors.affiliation: Istituto Italiano di Tecnologia, 16163 Genoa, Italy, and.
authors.forename: Stefka
authors.initials: S
authors.lastname: Stancheva
authors.affiliation: International School for Advanced Studies, 34136 Trieste, Italy.
authors.forename: Beatrice
authors.initials: B
authors.lastname: Pastore
authors.affiliation: National Research Council Institute of Cell Biology and Neurobiology, Santa Lucia Foundation, 00143 Rome, Italy.
authors.forename: Martine
authors.initials: M
authors.lastname: Ammassari-Teule
authors.affiliation: Istituto Italiano di Tecnologia, 16163 Genoa, Italy, and.
authors.forename: Andrea
authors.initials: A
authors.lastname: Barberis
authors.affiliation: International School for Advanced Studies, 34136 Trieste, Italy, European Brain Research Institute, 00143 Rome, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Cherubini
authors.affiliation: International School for Advanced Studies, 34136 Trieste, Italy, European Brain Research Institute, 00143 Rome, Italy zacchi@sissa.it.
authors.forename: Paola
authors.initials: P
authors.lastname: Zacchi
mesh_terms: D000818:Animals; D056547:CA1 Region, Hippocampal / Q000166:cytology; D002478:Cells, Cultured; D000076122:Disks Large Homolog 4 Protein; D005260:Female; D051528:Guanylate Kinases / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D007536:Isomerism; D017774:Long-Term Potentiation; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D000072340:NIMA-Interacting Peptidylprolyl Isomerase / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism* / Q000502:physiology; D009435:Synaptic Transmission
chemical_list: D000076122:Disks Large Homolog 4 Protein; C501447:Dlg4 protein, mouse; D008565:Membrane Proteins; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D016194:Receptors, N-Methyl-D-Aspartate; D051528:Guanylate Kinases; C000606850:Pin1 protein, mouse
keywords: NMDA receptors; PSD-95; Pin1; dendritic spines; glutamatergic transmission; hippocampus