Loss of IQSEC3 Disrupts GABAergic Synapse Maintenance and Decreases Somatostatin Expression in the Hippocampus

Cell Rep. 2020 Feb 11;30(6):1995-2005.e5. doi: 10.1016/j.celrep.2020.01.053.


Gephyrin interacts with various GABAergic synaptic proteins to organize GABAergic synapse development. Among the multitude of gephyrin-binding proteins is IQSEC3, a recently identified component at GABAergic synapses that acts through its ADP ribosylation factor-guanine nucleotide exchange factor (ARF-GEF) activity to orchestrate GABAergic synapse formation. Here, we show that IQSEC3 knockdown (KD) reduced GABAergic synaptic density in vivo, suggesting that IQSEC3 is required for GABAergic synapse maintenance in vivo. We further show that IQSEC3 KD in the dentate gyrus (DG) increases seizure susceptibility and triggers selective depletion of somatostatin (SST) peptides in the DG hilus in an ARF-GEP activity-dependent manner. Strikingly, selective introduction of SST into SST interneurons in DG-specific IQSEC3-KD mice reverses GABAergic synaptic deficits. Thus, our data suggest that IQSEC3 is required for linking gephyrin-GABAA receptor complexes with ARF-dependent pathways to prevent aberrant, runaway excitation and thereby contributes to the integrity of SST interneurons and proper GABAergic synapse maintenance.

Keywords: ARF6; GABA; IQSEC3; dentate gyrus; epilepsy; excitation-inhibition balance; gephyrin; inhibitory synapse; somatostatin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Guanine Nucleotide Exchange Factors / deficiency*
  • Guanine Nucleotide Exchange Factors / metabolism*
  • HEK293 Cells
  • Hippocampus / cytology
  • Hippocampus / metabolism*
  • Humans
  • Male
  • Membrane Proteins / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Somatostatin / metabolism*
  • Synapses / metabolism*


  • Guanine Nucleotide Exchange Factors
  • IQSEC3 protein, human
  • Iqsec3 protein, mouse
  • Membrane Proteins
  • gephyrin
  • Somatostatin