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Association of Rgs7/Gβ5 complexes with girk channels and GABA B receptors in hippocampal CA1 pyramidal neurons
Author(s) -
FajardoSerrano Ana,
Wydeven Nicole,
Young Daniele,
Watanabe Masahiko,
Shigemoto Ryuichi,
Martemyanov Kirill A.,
Wickman Kevin,
Luján Rafael
Publication year - 2013
Publication title -
hippocampus
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.767
H-Index - 155
eISSN - 1098-1063
pISSN - 1050-9631
DOI - 10.1002/hipo.22161
Subject(s) - g protein coupled inwardly rectifying potassium channel , gabab receptor , g protein , chemistry , g protein coupled receptor , dendritic spine , microbiology and biotechnology , neuroscience , receptor , hippocampal formation , biophysics , biology , biochemistry , gabaa receptor
In the hippocampus, signaling through G protein‐coupled receptors is modulated by Regulators of G protein signaling (Rgs) proteins, which act to stimulate the rate of GTP hydrolysis, and consequently, G protein inactivation. The R7‐Rgs subfamily selectively deactivates the G i/o ‐class of Gα subunits that mediate the action of several GPCRs. Here, we used co‐immunoprecipitation, electrophysiology and immunoelectron microscopy techniques to investigate the formation of macromolecular complexes and spatial relationship of Rgs7/Gβ5 complexes and its prototypical signaling partners, the GABA B receptor and Girk channel. Co‐expression of recombinant GABA B receptors and Girk channels in combination with co‐immunoprecipitation experiments established that the Rgs7/Gβ5 forms complexes with GABA B receptors or Girk channels. Using electrophysiological experiments, we found that GABA B ‐Girk current deactivation kinetics was markedly faster in cells coexpressing Rgs7/Gβ5. At the electron microscopic level, immunolabeling for Rgs7 and Gβ5 proteins was found primarily in the dendritic layers of the hippocampus and showed similar distribution patterns. Immunoreactivity was mostly localized along the extrasynaptic plasma membrane of dendritic shafts and spines of pyramidal cells and, to a lesser extent, to that of presynaptic terminals. Quantitative analysis of immunogold particles for Rgs7 and Gβ5 revealed an enrichment of the two proteins around excitatory synapses on dendritic spines, virtually identical to that of Girk2 and GABA B1 . These data support the existence of macromolecular complexes composed of GABA B receptor‐G protein‐Rgs7‐Girk channels in which Rgs7 and Gβ5 proteins may preferentialy modulate GABA B receptor signaling through the deactivation of Girk channels on dendritic spines. In contrast, Rgs7 and Girk2 were associated but mainly segregated from GABA B1 in dendritic shafts, where Rgs7/Gβ5 signaling complexes might modulate Girk‐dependent signaling via a different metabotropic receptor(s). © 2013 Wiley Periodicals, Inc.