Electron microscopic immunocytochemical detection of PSD-95, PSD-93, SAP-102, and SAP-97 at postsynaptic, presynaptic, and nonsynaptic sites of adult and neonatal rat visual cortex

Chiye Aoki, Ilona Miko, Hysell Oviedo, Tamara Mikeladze-Dvali, Lucien Alexandre, Neal Sweeney, David S. Bredt

Research output: Contribution to journalArticle

Abstract

Membrane-associated guanylate kinases (MAGUKs) assemble protein complexes at sites of cell-cell contact. At excitatory synapses in brain, MAGUKs localize to the postsynaptic density (PSD) and interact with N-methyl-D-aspartate (NMDA) glutamate receptors and downstream signaling proteins. However, NMDA receptors are not restricted to the PSDs, as electron microscopic immunocytochemical (EM-ICC) results indicate that NMDA receptors also occur at nonsynaptic portions of dendrites, perhaps functioning as reserves for rapid insertion into synaptic membranes in response to appropriate synaptic activity. NMDA receptors also occur in axons, at least in part to support glutamate-dependent enhancement of transmitter release. In this study, a systematic EM-ICC survey was performed to determine whether the distributions of four neuronal MAGUKs - PSD-95, PSD-93, SAP-102, and SAP-97 - resemble that of NMDA receptors. Quantitative analysis revealed that the density of PSD-95 over thick PSDs of asymmetric axo-spinous synaptic junctions is 2-3-fold the level in the immediately adjacent cytoplasm of spines and terminals, while symmetric synapses show no association with PSD-95. Similarly, all four MAGUKs occur over PSDs of spines. However, we also detected MAGUK immunoreactivity, albeit more diffusely, along presynaptic membranes and in the cytoplasm of axons and dendritic shafts. In fact, the overall distribution of PSD-95 within the neuropil is equally prevalent along plasma membranes (including synaptic portions) as in the cytoplasm, away from plasma membranes. These results suggest that MAGUKs have dual roles: to maintain receptors at synapses and to regulate shuttling of receptors between nonsynaptic and synaptic sites.

Original languageEnglish (US)
Pages (from-to)239-257
Number of pages19
JournalSynapse
Volume40
Issue number4
DOIs
StatePublished - Jun 15 2001

Fingerprint

Guanylate Kinases
Post-Synaptic Density
Visual Cortex
N-Methyl-D-Aspartate Receptors
Electrons
Synapses
Cytoplasm
Axons
Spine
Cell Membrane
Synaptic Membranes
Neuropil
Glutamate Receptors
Dendrites
Glutamic Acid
Proteins
Membranes
Brain

Keywords

  • Glutamate receptors
  • Membrane-associated guanylate kinases
  • Postembedding gold labeling
  • Postsynaptic density
  • Receptor trafficking
  • Synaptic strength
  • Synaptogenesis

ASJC Scopus subject areas

  • Physiology
  • Neuroscience(all)
  • Pharmacology

Cite this

Electron microscopic immunocytochemical detection of PSD-95, PSD-93, SAP-102, and SAP-97 at postsynaptic, presynaptic, and nonsynaptic sites of adult and neonatal rat visual cortex. / Aoki, Chiye; Miko, Ilona; Oviedo, Hysell; Mikeladze-Dvali, Tamara; Alexandre, Lucien; Sweeney, Neal; Bredt, David S.

In: Synapse, Vol. 40, No. 4, 15.06.2001, p. 239-257.

Research output: Contribution to journalArticle

Aoki, Chiye ; Miko, Ilona ; Oviedo, Hysell ; Mikeladze-Dvali, Tamara ; Alexandre, Lucien ; Sweeney, Neal ; Bredt, David S. / Electron microscopic immunocytochemical detection of PSD-95, PSD-93, SAP-102, and SAP-97 at postsynaptic, presynaptic, and nonsynaptic sites of adult and neonatal rat visual cortex. In: Synapse. 2001 ; Vol. 40, No. 4. pp. 239-257.
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abstract = "Membrane-associated guanylate kinases (MAGUKs) assemble protein complexes at sites of cell-cell contact. At excitatory synapses in brain, MAGUKs localize to the postsynaptic density (PSD) and interact with N-methyl-D-aspartate (NMDA) glutamate receptors and downstream signaling proteins. However, NMDA receptors are not restricted to the PSDs, as electron microscopic immunocytochemical (EM-ICC) results indicate that NMDA receptors also occur at nonsynaptic portions of dendrites, perhaps functioning as reserves for rapid insertion into synaptic membranes in response to appropriate synaptic activity. NMDA receptors also occur in axons, at least in part to support glutamate-dependent enhancement of transmitter release. In this study, a systematic EM-ICC survey was performed to determine whether the distributions of four neuronal MAGUKs - PSD-95, PSD-93, SAP-102, and SAP-97 - resemble that of NMDA receptors. Quantitative analysis revealed that the density of PSD-95 over thick PSDs of asymmetric axo-spinous synaptic junctions is 2-3-fold the level in the immediately adjacent cytoplasm of spines and terminals, while symmetric synapses show no association with PSD-95. Similarly, all four MAGUKs occur over PSDs of spines. However, we also detected MAGUK immunoreactivity, albeit more diffusely, along presynaptic membranes and in the cytoplasm of axons and dendritic shafts. In fact, the overall distribution of PSD-95 within the neuropil is equally prevalent along plasma membranes (including synaptic portions) as in the cytoplasm, away from plasma membranes. These results suggest that MAGUKs have dual roles: to maintain receptors at synapses and to regulate shuttling of receptors between nonsynaptic and synaptic sites.",
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AU - Miko, Ilona

AU - Oviedo, Hysell

AU - Mikeladze-Dvali, Tamara

AU - Alexandre, Lucien

AU - Sweeney, Neal

AU - Bredt, David S.

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