Regulated lysosomal trafficking as a mechanism for regulating GABAA receptor abundance at synapses in Caenorhabditis elegans

Mol Cell Neurosci. 2010 Aug;44(4):307-17. doi: 10.1016/j.mcn.2010.04.002. Epub 2010 Apr 18.

Abstract

GABA(A) receptor plasticity is important for both normal brain function and disease progression. We are studying GABA(A) receptor plasticity in Caenorhabditis elegans using a genetic approach. Acute exposure of worms to the GABA(A) agonist muscimol hyperpolarizes postsynaptic cells, causing paralysis. Worms adapt after several hours, but show uncoordinated locomotion consistent with decreased GABA signaling. Using patch-clamp and immunofluorescence approaches, we show that GABA(A) receptors are selectively removed from synapses during adaptation. Subunit mRNA levels were unchanged, suggesting a post-transcriptional mechanism. Mutants with defective lysosome function (cup-5) show elevated GABA(A) receptor levels at synapses prior to muscimol exposure. During adaptation, these receptors are removed more slowly, and accumulate in intracellular organelles positive for the late endosome marker GFP-RAB-7. These findings suggest that chronic agonist exposure increases endocytosis and lysosomal trafficking of GABA(A) receptors, leading to reduced levels of synaptic GABA(A) receptors and reduced postsynaptic GABA sensitivity.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Caenorhabditis elegans / physiology*
  • Caenorhabditis elegans Proteins / genetics
  • Endocytosis / physiology
  • Fluorescent Antibody Technique
  • GABA Agonists / metabolism
  • GABA-A Receptor Agonists
  • Locomotion / drug effects
  • Lysosomes / physiology*
  • Membrane Proteins / genetics
  • Muscimol / pharmacology
  • Mutation / genetics
  • Patch-Clamp Techniques
  • Protein Transport / physiology*
  • Receptors, GABA-A / metabolism*
  • Recombinant Fusion Proteins / analysis
  • Synapses / physiology*
  • Synaptic Transmission / drug effects
  • rab GTP-Binding Proteins / analysis

Substances

  • CUP-5 protein, C elegans
  • Caenorhabditis elegans Proteins
  • GABA Agonists
  • GABA-A Receptor Agonists
  • Membrane Proteins
  • Receptors, GABA-A
  • Recombinant Fusion Proteins
  • rab7 protein
  • Muscimol
  • rab GTP-Binding Proteins