Activity-Dependent Inhibitory Synapse Scaling Is Determined by Gephyrin Phosphorylation and Subsequent Regulation of GABAA Receptor Diffusion

eNeuro. 2018 Jan 18;5(1):ENEURO.0203-17.2017. doi: 10.1523/ENEURO.0203-17.2017. eCollection 2018 Jan-Feb.

Abstract

Synaptic plasticity relies on the rapid changes in neurotransmitter receptor number at postsynaptic sites. Using superresolution photoactivatable localization microscopy imaging and quantum dot-based single-particle tracking in rat hippocampal cultured neurons, we investigated whether the phosphorylation status of the main scaffolding protein gephyrin influenced the organization of the gephyrin scaffold and GABAA receptor (GABAAR) membrane dynamics. We found that gephyrin phosphorylation regulates gephyrin microdomain compaction. Extracellular signal-regulated kinase 1/2 and glycogen synthase kinase 3β (GSK3β) signaling alter the gephyrin scaffold mesh differentially. Differences in scaffold organization similarly affected the diffusion of synaptic GABAARs, suggesting reduced gephyrin receptor-binding properties. In the context of synaptic scaling, our results identify a novel role of the GSK3β signaling pathway in the activity-dependent regulation of extrasynaptic receptor surface trafficking and GSK3β, protein kinase A, and calcium/calmodulin-dependent protein kinase IIα pathways in facilitating adaptations of synaptic receptors.

Keywords: GABAA receptor; PALM; homeostatic plasticity; post-translation modification; single particle tracking.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Diffusion
  • Female
  • Glycogen Synthase Kinase 3 beta / metabolism
  • Hippocampus / metabolism
  • MAP Kinase Signaling System
  • Male
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Neuronal Plasticity*
  • Neurons / metabolism*
  • Phosphorylation
  • Primary Cell Culture
  • Rats, Sprague-Dawley
  • Receptors, GABA-A / metabolism*
  • Signal Transduction
  • Synapses / metabolism*

Substances

  • Carrier Proteins
  • Membrane Proteins
  • Receptors, GABA-A
  • gephyrin
  • Glycogen Synthase Kinase 3 beta
  • Gsk3b protein, rat