title: PKC phosphorylation regulates mGluR5 trafficking by enhancing binding of Siah-1A.
abstract: Glutamate is the major excitatory neurotransmitter in the mammalian CNS and acts on both ionotropic and metabotropic glutamate receptors (mGluRs). The mGluRs are widely distributed in the CNS and modulate a variety of neuronal processes, including neurotransmitter release and ion channel function. In hippocampus and cortex, mGluR5 is highly expressed and plays an important role in the regulation of synaptic plasticity. Calmodulin (CaM) binding dynamically regulates mGluR5 surface expression; however, the mechanisms linking CaM to mGluR5 trafficking are not clear. Recent studies showed that CaM binding to mGluR7 regulates its trafficking in a phosphorylation-dependent manner by disrupting the binding of protein interacting with C kinase 1. The E3 ligase seven in absentia homolog (Siah)-1A binds to mGluR5 and competes with CaM binding, making it an intriguing molecule to regulate phosphorylation-dependent trafficking of mGluR5. In the present study, we find that CaM competes with Siah-1A for mGluR5 binding in a phosphorylation-dependent manner in rat hippocampal neurons. Specifically, phosphorylation of mGluR5 S901 favors Siah-1A binding by displacing CaM. We identified critical residues regulating Siah-1A binding to mGluR5 and showed that binding is essential for the Siah-1A effects on mGluR5 trafficking. Siah-1A binding decreases mGluR5 surface expression and increases endosomal trafficking and lysosomal degradation of mGluR5. Thus CaM-regulated Siah-1A binding to mGluR5 dynamically regulates mGluR5 trafficking. These findings support a conserved role for CaM in regulating mGluR trafficking by PKC-dependent regulation of receptor-binding proteins.
authors.affiliation: Department of Pharmacology, Yonsei University College of Medicine, Seoul 120-752, Korea.
authors.forename: Suk Jin
authors.initials: SJ
authors.lastname: Ko
authors.forename: Kaname
authors.initials: K
authors.lastname: Isozaki
authors.forename: Insook
authors.initials: I
authors.lastname: Kim
authors.forename: Jeong Ho
authors.initials: JH
authors.lastname: Lee
authors.forename: Ho Jin
authors.initials: HJ
authors.lastname: Cho
authors.forename: Sun Young
authors.initials: SY
authors.lastname: Sohn
authors.forename: So Ra
authors.initials: SR
authors.lastname: Oh
authors.forename: Steven
authors.initials: S
authors.lastname: Park
authors.forename: Dong Goo
authors.initials: DG
authors.lastname: Kim
authors.forename: Chul Hoon
authors.initials: CH
authors.lastname: Kim
authors.forename: Katherine W
authors.initials: KW
authors.lastname: Roche
mesh_terms: D001665:Binding Sites; D019921:Biotinylation; D015153:Blotting, Western; D002147:Calmodulin / Q000378:metabolism / Q000502:physiology; D018698:Glutamic Acid / Q000502:physiology; D006367:HeLa Cells; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D008026:Ligation; D018377:Neurotransmitter Agents / Q000502:physiology; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D064529:Receptor, Metabotropic Glutamate 5; D011956:Receptors, Cell Surface / Q000378:metabolism; D018094:Receptors, Metabotropic Glutamate / Q000502:physiology*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D015003:Yeasts / Q000378:metabolism; D000098563:Seven in Absentia Proteins
chemical_list: D002147:Calmodulin; C578935:GRM5 protein, human; C578937:Grm5 protein, rat; D018377:Neurotransmitter Agents; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; D064529:Receptor, Metabotropic Glutamate 5; D011956:Receptors, Cell Surface; D018094:Receptors, Metabotropic Glutamate; D018698:Glutamic Acid; D044767:Ubiquitin-Protein Ligases; D000098563:Seven in Absentia Proteins; D011493:Protein Kinase C