title: Activity-dependent ubiquitination of GluA1 mediates a distinct AMPA receptor endocytosis and sorting pathway.
abstract: The accurate trafficking of AMPA receptors (AMPARs) to and from the synapse is a critical component of learning and memory in the brain, whereas dysfunction of AMPAR trafficking is hypothesized to be an underlying mechanism of Alzheimer's disease. Previous work has shown that ubiquitination of integral membrane proteins is a common posttranslational modification used to mediate endocytosis and endocytic sorting of surface proteins in eukaryotic cells. Here we report that mammalian AMPARs become ubiquitinated in response to their activation. Using a mutant of GluA1 that is unable to be ubiquitinated at lysines on its C-terminus, we demonstrate that ubiquitination is required for internalization of surface AMPARs and their trafficking to the lysosome in response to the AMPAR agonist AMPA but not for internalization of AMPARs in response to the NMDA receptor agonist NMDA. Through overexpression or RNA interference-mediated knockdown, we identify that a specific E3 ligase, Nedd4-1 (neural-precursor cell-expressed developmentally downregulated gene 4-1), is necessary for this process. Finally, we show that ubiquitination of GluA1 by Nedd4-1 becomes more prevalent as neurons mature. Together, these data show that ubiquitination of GluA1-containing AMPARs by Nedd4-1 mediates their endocytosis and trafficking to the lysosome. Furthermore, these results provide insight into how hippocampal neurons regulate AMPAR trafficking and degradation with high specificity in response to differing neuronal signaling cues and suggest that changes to this pathway may occur as neurons mature.
authors.affiliation: Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093, USA.
authors.forename: Lindsay A
authors.initials: LA
authors.lastname: Schwarz
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Hall
authors.forename: Gentry N
authors.initials: GN
authors.lastname: Patrick
mesh_terms: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D056827:Endosomal Sorting Complexes Required for Transport / Q000378:metabolism; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000235:genetics; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D047468:Immunoprecipitation / Q000379:methods; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics; D018613:Microscopy, Confocal / Q000379:methods; D016202:N-Methylaspartate / Q000494:pharmacology; D000075702:Nedd4 Ubiquitin Protein Ligases; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D021381:Protein Transport / Q000187:drug effects / Q000235:genetics; D034622:RNA Interference / Q000502:physiology; D051381:Rats; D018091:Receptors, AMPA / Q000378:metabolism*; D014162:Transfection / Q000379:methods; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D054875:Ubiquitination / Q000187:drug effects / Q000502:physiology*; D014633:Valine / Q000031:analogs & derivatives / Q000494:pharmacology; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
chemical_list: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D056827:Endosomal Sorting Complexes Required for Transport; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D049452:Green Fluorescent Proteins; D016202:N-Methylaspartate; D000075702:Nedd4 Ubiquitin Protein Ligases; D018091:Receptors, AMPA; D044767:Ubiquitin-Protein Ligases; D014633:Valine; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; C056639:2-amino-5-phosphopentanoic acid; C000618479:NEDD4L protein, rat; C000618483:Nedd4 protein, human; C000618484:Nedd4 protein, rat