EPSILON: a method for pulse-chase labeling to probe synaptic AMPAR exocytosis during memory formation

Area of Science:

• Neuroscience
• Molecular Biology
• Cell Biology

Background:

• Understanding synaptic plasticity is key to deciphering learning and memory mechanisms.
• Synaptic strength changes are fundamental to memory formation.
• Mapping receptor dynamics at synapses offers insights into neural circuit function.

Purpose of the Study:

• To develop a novel technique for mapping alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) exocytosis in vivo.
• To visualize synaptic potentiation during memory formation at single-synapse resolution.
• To investigate the relationship between AMPAR exocytosis and neuronal activity markers during memory encoding.

Main Methods:

• Developed Extracellular Protein Surface Labeling in Neurons (EPSILON) technique.
• Utilized sequential pulse-chase labeling with membrane-impermeable dyes.
• Applied the method to genetically targeted neurons in mice during contextual fear conditioning.

Main Results:

• Achieved synaptic-resolution mapping of AMPAR exocytosis in vivo.
• Observed a strong correlation between AMPAR exocytosis and cFos expression in CA1 pyramidal neurons.
• Demonstrated that EPSILON can visualize synaptic plasticity associated with memory formation.

Conclusions:

• The EPSILON technique provides a powerful tool for studying synaptic plasticity and memory mechanisms.
• Synaptic AMPAR exocytosis is closely linked to neuronal activity markers like cFos in memory engrams.
• EPSILON has potential applications for studying the trafficking of other transmembrane proteins.