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J Neurosci. 2017 Feb 15;37(7):1747-1756. doi: 10.1523/JNEUROSCI.0514-16.2016. Epub 2017 Jan 10.

Nanoscale Molecular Reorganization of the Inhibitory Postsynaptic Density Is a Determinant of GABAergic Synaptic Potentiation.

Author information

1
Nanoscopy Department.
2
Nikon Imaging Center, Fondazione Istituto Italiano di Tecnologia, 16163 Genoa, Italy.
3
Università di Genova, Department of Physics, 16146 Genoa, Italy.
4
Pattern Analysis and Computer Vision Department.
5
Neuroscience and Brain Technologies Department, and.
6
Institute of Pharmacology and Toxicology, University of Zurich, 8057 Zurich, Switzerland, and.
7
Neuroscience and Brain Technologies Department, and andrea.barberis@iit.it francesca.cella@iit.it.
8
Nanoscopy Department, andrea.barberis@iit.it francesca.cella@iit.it.

Abstract

Gephyrin is a key scaffold protein mediating the anchoring of GABAA receptors at inhibitory synapses. Here, we exploited superresolution techniques combined with proximity-based clustering analysis and model simulations to investigate the single-molecule gephyrin reorganization during plasticity of inhibitory synapses in mouse hippocampal cultured neurons. This approach revealed that, during the expression of inhibitory LTP, the increase of gephyrin density at postsynaptic sites is associated with the promoted formation of gephyrin nanodomains. We demonstrate that the gephyrin rearrangement in nanodomains stabilizes the amplitude of postsynaptic currents, indicating that, in addition to the number of synaptic GABAA receptors, the nanoscale distribution of GABAA receptors in the postsynaptic area is a crucial determinant for the expression of inhibitory synaptic plasticity. In addition, the methodology implemented here clears the way to the application of the graph-based theory to single-molecule data for the description and quantification of the spatial organization of the synapse at the single-molecule level.SIGNIFICANCE STATEMENT The mechanisms of inhibitory synaptic plasticity are poorly understood, mainly because the size of the synapse is below the diffraction limit, thus reducing the effectiveness of conventional optical and imaging techniques. Here, we exploited superresolution approaches combined with clustering analysis to study at unprecedented resolution the distribution of the inhibitory scaffold protein gephyrin in response to protocols inducing LTP of inhibitory synaptic responses (iLTP). We found that, during the expression of iLTP, the increase of synaptic gephyrin is associated with the fragmentation of gephyrin in subsynaptic nanodomains. We demonstrate that such synaptic gephyrin nanodomains stabilize the amplitude of inhibitory postsynaptic responses, thus identifying the nanoscale gephyrin rearrangement as a key determinant for inhibitory synaptic plasticity.

KEYWORDS:

GABAA receptors; PALM; STORM; clustering; gephyrin; model simulations; plasticity

PMID:
28073939
PMCID:
PMC6589977
DOI:
10.1523/JNEUROSCI.0514-16.2016
[Indexed for MEDLINE]
Free PMC Article

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