ABSTRACT
PSD-95 is a major scaffolding protein of the postsynaptic density, tethering NMDA- and AMPA-type glutamate receptors to signaling proteins and the neuronal cytoskeleton. Here we show that PSD-95 is regulated by the ubiquitin-proteasome pathway. PSD-95 interacts with and is ubiquitinated by the E3 ligase Mdm2. In response to NMDA receptor activation, PSD-95 is ubiquitinated and rapidly removed from synaptic sites by proteasome-dependent degradation. Mutations that block PSD-95 ubiquitination prevent NMDA-induced AMPA receptor endocytosis. Likewise, proteasome inhibitors prevent NMDA-induced AMPA receptor internalization and synaptically induced long-term depression. This is consistent with the notion that PSD-95 levels are an important determinant of AMPA receptor number at the synapse. These data suggest that ubiquitination of PSD-95 through an Mdm2-mediated pathway is critical in regulating AMPA receptor surface expression during synaptic plasticity.
Subject(s)
Acetylcysteine/analogs & derivatives , Nerve Tissue Proteins/metabolism , Neurons/metabolism , Nuclear Proteins , Receptors, AMPA/metabolism , Tacrolimus/analogs & derivatives , Ubiquitin/metabolism , Acetylcysteine/pharmacology , Analysis of Variance , Animals , Animals, Newborn , Blotting, Western , Calcium/metabolism , Cells, Cultured , Colforsin/pharmacology , Cysteine Proteinase Inhibitors/pharmacology , Disks Large Homolog 4 Protein , Drug Interactions , Electric Stimulation , Embryo, Mammalian , Endocytosis , Epitopes/metabolism , Excitatory Amino Acid Agonists/pharmacology , Hippocampus/cytology , Hippocampus/drug effects , Hippocampus/physiology , Humans , Immunoglobulin G/metabolism , Immunohistochemistry , Immunosuppressive Agents/pharmacology , In Vitro Techniques , Intracellular Signaling Peptides and Proteins , Kidney , Leupeptins/pharmacology , Membrane Potentials/drug effects , Membrane Potentials/physiology , Membrane Proteins , Mutation , N-Methylaspartate/pharmacology , Neural Inhibition/drug effects , Neural Inhibition/physiology , Neurons/drug effects , Patch-Clamp Techniques , Proto-Oncogene Proteins/metabolism , Proto-Oncogene Proteins c-mdm2 , Rats , Rats, Long-Evans , Synapses/drug effects , Synapses/metabolism , Synapsins/metabolism , Tacrolimus/pharmacology , Time Factors , TransfectionABSTRACT
The Scar/WAVE family of scaffolding proteins organize molecular networks that relay signals from the GTPase Rac to the actin cytoskeleton. The WAVE-1 isoform is a brain-specific protein expressed in variety of areas including the regions of the hippocampus and the Purkinje cells of the cerebellum. Targeted disruption of the WAVE-1 gene generated mice with reduced anxiety, sensorimotor retardation, and deficits in hippocampal-dependent learning and memory. These sensorimotor and cognitive deficits are analogous to the symptoms of patients with 3p-syndrome mental retardation who are haploinsufficient for WRP/MEGAP, a component of the WAVE-1 signaling network. Thus WAVE-1 is required for normal neural functioning.
