IQ-ArfGEF/BRAG1 is a guanine nucleotide exchange factor for Arf6 that interacts with PSD-95 at postsynaptic density of excitatory synapses

Neurosci Res. 2008 Feb;60(2):199-212. doi: 10.1016/j.neures.2007.10.013. Epub 2007 Nov 17.

Abstract

ADP ribosylation factor 6 (Arf6) is a small GTPase that regulates dendritic differentiation possibly through the organization of actin cytoskeleton and membrane traffic. Here, we characterized IQ-ArfGEF/BRAG1, a guanine nucleotide exchange factor (GEF) for Arf6, in the mouse brain. In vivo Arf pull down assay demonstrated that IQ-ArfGEF/BRAG1 activated Arf6 more potently than Arf1. IQ-ArfGEF/BRAG1 mRNA was abundantly expressed in the brain with higher levels in forebrain structures and cerebellar granule cells. In hippocampal neurons, IQ-ArfGEF/BRAG1 mRNA was localized not only at neuronal cell bodies but also at dendritic processes, indicating its dendritic transport and localization. Immunoprecipitation and in vitro binding experiments revealed that IQ-ArfGEF/BRAG1 formed a protein complex with N-methyl-d-aspartate (NMDA)-type glutamate receptors through the interaction with a postsynaptic density (PSD) scaffold protein, PSD-95. Immunohistochemical analysis demonstrated that IQ-ArfGEF/BRAG1 was localized preferentially at the postsynaptic density of asymmetrical synapses on dendritic spines, but was lacking at GABAa receptor-carrying inhibitory synapses. Taken together, IQ-ArfGEF/BRAG1 forms a postsynaptic protein complex containing PSD-95 and NMDA receptors at excitatory synapses, where it may function as a GEF for Arf6.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ADP-Ribosylation Factors / metabolism*
  • Animals
  • Brain / cytology
  • Brain / metabolism
  • COS Cells
  • Chlorocebus aethiops
  • Cloning, Molecular / methods
  • Disks Large Homolog 4 Protein
  • Electrophoretic Mobility Shift Assay
  • Gene Expression Regulation, Developmental / physiology
  • Guanine Nucleotide Exchange Factors / genetics
  • Guanine Nucleotide Exchange Factors / metabolism*
  • Guanylate Kinases
  • Guinea Pigs
  • Immunoprecipitation / methods
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Membrane Proteins / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Neurons / metabolism
  • Rabbits
  • Receptors, GABA-A / metabolism
  • Receptors, N-Methyl-D-Aspartate / metabolism*
  • Synapses / metabolism*
  • Synapses / ultrastructure
  • Transfection

Substances

  • Disks Large Homolog 4 Protein
  • Dlg4 protein, mouse
  • Guanine Nucleotide Exchange Factors
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Receptors, GABA-A
  • Receptors, N-Methyl-D-Aspartate
  • Guanylate Kinases
  • ADP-Ribosylation Factors
  • ADP-ribosylation factor 6