title: Synaptic strength is bidirectionally controlled by opposing activity-dependent regulation of Nedd4-1 and USP8.
abstract: The trafficking of AMPA receptors (AMPARs) to and from synapses is crucial for synaptic plasticity. Previous work has demonstrated that AMPARs undergo activity-dependent ubiquitination by the E3 ubiquitin ligase Nedd4-1, which promotes their internalization and degradation in lysosomes. Here, we define the molecular mechanisms involved in ubiquitination and deubiquitination of AMPARs. We report that Nedd4-1 is rapidly redistributed to dendritic spines in response to AMPAR activation and not in response to NMDA receptor (NMDAR) activation in cultured rat neurons. In contrast, NMDAR activation directly antagonizes Nedd4-1 function by promoting the deubiquitination of AMPARs. We show that NMDAR activation causes the rapid dephosphorylation and activation of the deubiquitinating enzyme (DUB) USP8. Surface AMPAR levels and synaptic strength are inversely regulated by Nedd4-1 and USP8. Strikingly, we show that homeostatic downscaling of synaptic strength is accompanied by an increase and decrease in Nedd4-1 and USP8 protein levels, respectively. Furthermore, we show that Nedd4-1 is required for homeostatic loss of surface AMPARs and downscaling of synaptic strength. This study provides the first mechanistic evidence for rapid and opposing activity-dependent control of a ubiquitin ligase and DUB at mammalian CNS synapses. We propose that the dynamic regulation of these opposing forces is critical in maintaining synapses and scaling them during homeostatic plasticity.
authors.affiliation: University of California San Diego, Section of Neurobiology, Division of Biological Sciences, La Jolla, California 92093.
authors.forename: Samantha L
authors.initials: SL
authors.lastname: Scudder
authors.affiliation: University of California San Diego, Section of Neurobiology, Division of Biological Sciences, La Jolla, California 92093.
authors.forename: Marisa S
authors.identifier: http://orcid.org/0000-0002-1755-5649
authors.initials: MS
authors.lastname: Goo
authors.affiliation: ICB International, La Jolla, California 92037.
authors.forename: Anna E
authors.initials: AE
authors.lastname: Cartier
authors.affiliation: University of California San Diego, Section of Neurobiology, Division of Biological Sciences, La Jolla, California 92093.
authors.forename: Alice
authors.initials: A
authors.lastname: Molteni
authors.affiliation: Department of Biology, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, and.
authors.forename: Lindsay A
authors.initials: LA
authors.lastname: Schwarz
authors.affiliation: The Salk Institute for Biological Studies, La Jolla, California 92037.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Wright
authors.affiliation: University of California San Diego, Section of Neurobiology, Division of Biological Sciences, La Jolla, California 92093, gpatrick@ucsd.edu.
authors.forename: Gentry N
authors.initials: GN
authors.lastname: Patrick
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D010450:Endopeptidases / Q000502:physiology*; D056827:Endosomal Sorting Complexes Required for Transport / Q000502:physiology*; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D051379:Mice; D000075702:Nedd4 Ubiquitin Protein Ligases; D021381:Protein Transport / Q000502:physiology; D051381:Rats; D013569:Synapses / Q000502:physiology*; D043222:Ubiquitin Thiolesterase / Q000502:physiology*; D044767:Ubiquitin-Protein Ligases / Q000502:physiology*
chemical_list: D056827:Endosomal Sorting Complexes Required for Transport; C000618479:NEDD4L protein, rat; D000075702:Nedd4 Ubiquitin Protein Ligases; C000618483:Nedd4 protein, human; C000618484:Nedd4 protein, rat; C000618461:Nedd4l protein, mouse; D044767:Ubiquitin-Protein Ligases; D010450:Endopeptidases; C541534:USP8 protein, human; D043222:Ubiquitin Thiolesterase
keywords: AMPA receptors; E3 ubiquitin ligase; deubiquitination; endocytosis; lysosome; ubiquitin