AMPA-receptor activation regulates the diffusion of a membrane marker in parallel with dendritic spine motility in
D A Richards1, V De Paola, P Caroni
1Brain Research Institute, University of Zurich, Zurich, Switzerland. richards@physiology.wisc.edu
Abstract:
Dendritic spines are the site of most excitatory connections in the hippocampus. We have investigated the diffusibility of a membrane-bound green fluorescent protein (mGFP) within the inner leaflet of the plasma membrane using Fluorescence Recovery After Photobleaching. In dendritic spines the diffusion of mGFP was significantly retarded relative to the dendritic shaft. In parallel, we have assessed the motility of dendritic spines, and found an inverse correlation between spine motility and the rate of diffusion of mGFP. We then tested the influence of glutamate receptor activation or blockade, and the involvement of the actin cytoskeleton (using latrunculin A) on spine motility and mGFP diffusion. These results show that glutamate receptors regulate the mobility of molecules in the inner leaflet of the plasma membrane through an action upon the actin cytoskeleton, suggesting a novel mechanism for the regulation of postsynaptic receptor density and composition.
Insights
Dendritic spine membrane diffusion is slower than in the shaft, correlating inversely with spine motility. Glutamate receptors, via the actin cytoskeleton, regulate this membrane diffusion and spine dynamics.
Area of Science:
- Neuroscience
- Cell Biology
- Biophysics
Background:
- Dendritic spines are crucial postsynaptic sites for excitatory neurotransmission in the hippocampus.
- Understanding molecular dynamics within the spine plasma membrane is key to synaptic function.
Purpose of the Study:
- To investigate the diffusion of membrane-bound molecules within hippocampal dendritic spines.
- To explore the relationship between molecular diffusion, spine motility, and the influence of glutamate receptors and the actin cytoskeleton.
Main Methods:
- Utilized Fluorescence Recovery After Photobleaching (FRAP) to measure the diffusion of membrane-bound green fluorescent protein (mGFP).
- Assessed dendritic spine motility.
- Manipulated glutamate receptor activity and disrupted the actin cytoskeleton using latrunculin A.
Main Results:
- Diffusion of mGFP was significantly slower in dendritic spines compared to the dendritic shaft.
- A negative correlation was observed between dendritic spine motility and mGFP diffusion rate.
- Glutamate receptor activation/blockade and actin cytoskeleton integrity modulated mGFP diffusion and spine motility.
Conclusions:
- Glutamate receptors regulate inner plasma membrane leaflet mobility in dendritic spines.
- This regulation occurs via the actin cytoskeleton, suggesting a novel mechanism for controlling postsynaptic receptor composition and density.
