title: The BTB/kelch protein, KRIP6, modulates the interaction of PICK1 with GluR6 kainate receptors.
abstract: Neuronal proteins of the BTB/kelch and PDZ domain families interact with different regions of the cytoplasmic C-terminal domain of the GluR6 kainate receptor subunit. The BTB/kelch protein KRIP6 binds within a 58 amino acid segment of GluR6 proximal to the plasma membrane. In contrast, PDZ domain proteins, such as PICK1 and PSD95, interact with the last 4 residues of the GluR6 C-terminus. KRIP6 reduces peak currents mediated by recombinant GluR6 receptors and by native kainate receptors in neurons, whereas PICK1 stabilizes kainate receptors at synapses. Thus, protein-protein interactions at the C-terminal domain of GluR6 are important for regulating kainate receptor physiology. Here, we show by co-clustering and co-immunoprecipitation that KRIP6 interacts with PICK1 in heterologous cells. In addition, we demonstrate a novel modulation of GluR6 receptors by PICK1 resulting in increased peak current and relative desensitization of GluR6-mediated currents, phenotypes opposite to those produced by KRIP6. Importantly, these effects cancel out when KRIP6 and PICK1 are co-expressed together with GluR6. KRIP6 and PICK1 strongly co-cluster and co-immunoprecipitate regardless of the presence of GluR6. Immunofluorescence analysis reveals that GluR6 can either join the KRIP6-PICK1 clusters or remain separate; however, co-expression of KRIP6 reduces the fraction of PICK1 that co-immunoprecipitates with GluR6. Taken together, these results indicate that, in addition to a previously demonstrated direct interaction with the GluR6 C-terminal domain, KRIP6 regulates kainate receptors by inhibiting PICK1 modulation via competition or a mutual blocking effect.
authors.affiliation: Department of Cell Biology and Physiology, Washington University, St Louis, MO 63110, USA. flaezza@wustl.edu
authors.forename: Fernanda
authors.initials: F
authors.lastname: Laezza
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Wilding
authors.forename: Sunitha
authors.initials: S
authors.lastname: Sequeira
authors.forename: Ann Marie
authors.initials: AM
authors.lastname: Craig
authors.forename: James E
authors.initials: JE
authors.lastname: Huettner
mesh_terms: D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D002352:Carrier Proteins / Q000502:physiology*; D002460:Cell Line; D002522:Chlorocebus aethiops; D003598:Cytoskeletal Proteins / Q000502:physiology*; D004594:Electrophysiology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D007608:Kainic Acid / Q000494:pharmacology; D009687:Nuclear Proteins / Q000502:physiology*; D054731:PDZ Domains / Q000502:physiology; D018408:Patch-Clamp Techniques; D018092:Kainic Acid Receptors / Q000502:physiology*; D000097806:GluK2 Kainate Receptor
chemical_list: D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D018690:Excitatory Amino Acid Agonists; D007608:Kainic Acid; D009687:Nuclear Proteins; D018092:Kainic Acid Receptors; D000097806:GluK2 Kainate Receptor; C586302:KLHL41 protein, human; C498297:PICk1 protein, human