title: Epilepsy-associated gene Nedd4-2 mediates neuronal activity and seizure susceptibility through AMPA receptors.
abstract: The neural precursor cell expressed developmentally down-regulated gene 4-2, Nedd4-2, is an epilepsy-associated gene with at least three missense mutations identified in epileptic patients. Nedd4-2 encodes a ubiquitin E3 ligase that has high affinity toward binding and ubiquitinating membrane proteins. It is currently unknown how Nedd4-2 mediates neuronal circuit activity and how its dysfunction leads to seizures or epilepsies. In this study, we provide evidence to show that Nedd4-2 mediates neuronal activity and seizure susceptibility through ubiquitination of GluA1 subunit of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor, (AMPAR). Using a mouse model, termed Nedd4-2andi, in which one of the major forms of Nedd4-2 in the brain is selectively deficient, we found that the spontaneous neuronal activity in Nedd4-2andi cortical neuron cultures, measured by a multiunit extracellular electrophysiology system, was basally elevated, less responsive to AMPAR activation, and much more sensitive to AMPAR blockade when compared with wild-type cultures. When performing kainic acid-induced seizures in vivo, we showed that elevated seizure susceptibility in Nedd4-2andi mice was normalized when GluA1 is genetically reduced. Furthermore, when studying epilepsy-associated missense mutations of Nedd4-2, we found that all three mutations disrupt the ubiquitination of GluA1 and fail to reduce surface GluA1 and spontaneous neuronal activity when compared with wild-type Nedd4-2. Collectively, our data suggest that impaired GluA1 ubiquitination contributes to Nedd4-2-dependent neuronal hyperactivity and seizures. Our findings provide critical information to the future development of therapeutic strategies for patients who carry mutations of Nedd4-2.
authors.affiliation: Department of Molecular and Integrative Physiology, School of Molecular and Cellular Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States of America.
authors.forename: Jiuhe
authors.initials: J
authors.lastname: Zhu
authors.affiliation: Department of Molecular and Integrative Physiology, School of Molecular and Cellular Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States of America.
authors.forename: Kwan Young
authors.initials: KY
authors.lastname: Lee
authors.affiliation: Department of Molecular and Integrative Physiology, School of Molecular and Cellular Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States of America.
authors.forename: Kathryn A
authors.identifier: 0000-0002-7029-7132
authors.initials: KA
authors.lastname: Jewett
authors.affiliation: Department of Biology, Boston University, Boston, MA, United States of America.|Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA, United States of America.
authors.forename: Heng-Ye
authors.initials: HY
authors.lastname: Man
authors.affiliation: Department of Molecular and Integrative Physiology, School of Molecular and Cellular Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States of America.|Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America.|Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, United States of America.
authors.forename: Hee Jung
authors.initials: HJ
authors.lastname: Chung
authors.affiliation: Department of Molecular and Integrative Physiology, School of Molecular and Cellular Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States of America.|Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America.|Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, United States of America.
authors.forename: Nien-Pei
authors.identifier: 0000-0003-1032-0107
authors.initials: NP
authors.lastname: Tsai
mesh_terms: D048948:14-3-3 Proteins / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D002478:Cells, Cultured; D056827:Endosomal Sorting Complexes Required for Transport / Q000235:genetics* / Q000378:metabolism; D004827:Epilepsy / Q000235:genetics* / Q000378:metabolism; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D020022:Genetic Predisposition to Disease / Q000235:genetics; D057809:HEK293 Cells; D006801:Humans; D008239:Lysine / Q000235:genetics / Q000378:metabolism; D008297:Male; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D020125:Mutation, Missense; D000075702:Nedd4 Ubiquitin Protein Ligases; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D011810:Quinoxalines / Q000494:pharmacology; D018091:Receptors, AMPA / Q000235:genetics* / Q000378:metabolism; D012640:Seizures / Q000235:genetics* / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics* / Q000378:metabolism; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
chemical_list: D048948:14-3-3 Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D011810:Quinoxalines; D018091:Receptors, AMPA; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D000075702:Nedd4 Ubiquitin Protein Ligases; C000618483:Nedd4 protein, human; C000618485:Nedd4L protein, human; C000618461:Nedd4l protein, mouse; D044767:Ubiquitin-Protein Ligases; D008239:Lysine