In vivo STED microscopy visualizes PSD95 sub-structures and morphological changes over several hours in the mouse...

Area of Science:

• Neuroscience
• Cell Biology
• Structural Biology

Background:

• The post-synaptic density (PSD) is a critical protein complex at excitatory synapses, regulating synaptic function and strength.
• PSD95 is a major scaffolding protein within the PSD, organizing numerous synaptic proteins, including receptors and ion channels.

Purpose of the Study:

• To investigate the size, shape, and structural dynamics of PSD95 assemblies in the living mouse brain.
• To understand how PSD95 organization changes over time in response to synaptic activity.

Main Methods:

• Utilized super-resolution STED (STimulated Emission Depletion) nanoscopy to image PSD95.
• Employed adult knock-in mice expressing eGFP-fused PSD95 for live imaging.
• Analyzed PSD95 assembly morphology at various time points (1 minute to 6 hours) in the anaesthetized visual cortex.

Main Results:

• Super-resolved PSD95 assemblies displayed diverse sub-structures, predominantly ring-like, but also horseshoe and figure-8 shapes.
• These structures were either continuous or composed of distinct nanoclusters.
• While stable in the short term, over 50% of large PSD95 assemblies altered their sub-structure after 1 hour.

Conclusions:

• Large PSD95 assemblies possess a dynamic sub-morphology that changes within a 6-hour observation period.
• These findings highlight the plasticity of synaptic protein organization and its potential role in synaptic function.