title: Stoichiometry and phosphoisotypes of hippocampal AMPA-type glutamate receptor phosphorylation.
abstract: It has been proposed that the AMPAR phosphorylation regulates trafficking and channel activity, thereby playing an important role in synaptic plasticity. However, the actual stoichiometry of phosphorylation, information critical to understand the role of phosphorylation, is not known because of the lack of appropriate techniques for measurement. Here, using Phos-tag SDS-PAGE, we estimated the proportion of phosphorylated AMPAR subunit GluA1. The level of phosphorylated GluA1 at S831 and S845, two major sites implicated in AMPAR regulation, is almost negligible. Less than 1% of GluA1 is phosphorylated at S831 and less than 0.1% at S845. Considering the number of AMPAR at each synapse, the majority of synapses do not contain any phosphorylated AMPAR. Also, we did not see evidence of GluA1 dually phosphorylated at S831 and S845. Neuronal stimulation and learning increased phosphorylation, but the proportion was still low. Our results impel us to reconsider the mechanisms underlying synaptic plasticity.
authors.affiliation: Brain Science Institute, RIKEN, Wako, Saitama 351-0198, Japan.
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Hosokawa
authors.affiliation: Department of Physiology, Yokohama City University Graduate School of Medicine, Yokohama, Kanagawa 236-0004, Japan; Department of Systems Neuroscience, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi 755-8505, Japan.
authors.forename: Dai
authors.initials: D
authors.lastname: Mitsushima
authors.affiliation: Brain Science Institute, RIKEN, Wako, Saitama 351-0198, Japan.
authors.forename: Rina
authors.initials: R
authors.lastname: Kaneko
authors.affiliation: Brain Science Institute, RIKEN, Wako, Saitama 351-0198, Japan; Saitama University Brain Science Institute, Saitama University, Saitama 338-8570, Japan. Electronic address: yhayashi@brain.riken.jp.
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Hayashi
mesh_terms: D000818:Animals; D001362:Avoidance Learning / Q000502:physiology*; D004591:Electrophoresis, Polyacrylamide Gel; D057809:HEK293 Cells; D006624:Hippocampus / Q000378:metabolism*; D006801:Humans; D009473:Neuronal Plasticity / Q000502:physiology*; D010766:Phosphorylation; D051381:Rats; D018091:Receptors, AMPA / Q000378:metabolism*; D012694:Serine / Q000378:metabolism*
chemical_list: D018091:Receptors, AMPA; D012694:Serine