Pre- and postsynaptic nanostructures increase in size and complexity after LTP induction

Synapses, specialized contact sites between neurons, are the fundamental elements of neuronal information transfer. Synaptic plasticity is related to changes in synaptic morphology and the number of neurotransmitter receptors, and thought to underlie learning and memory. However, it is not clear how these structural and functional changes are connected. We utilized time-lapse super-resolution STED microscopy to visualize structural changes of the synaptic nano-organization of the postsynaptic scaffolding protein PSD95, the presynaptic scaffolding protein Bassoon, and the GluA2 subunit of AMPA receptors by chemically induced long-term potentiation (cLTP) at the level of single synapses. We found that the nano-organization of all three proteins undergoes an increase in complexity and size after cLTP induction. The increase was largely synchronous, peaking at [~]60 min after stimulation. Therefore, both the size and complexity of single pre- and post-synaptic nanostructures serve as substrates for adjusting and determining synaptic strength. Highlights- Time-lapse super-resolution images the structural changes of the PSD95 nano-organization after Cltp - cLTP-induced growth of the PSD95 nano-organization is less than spine head growth and peaks at 60 min, i.e. much slower than the increase in spine volume. - Most PSD95 nanostructures increase in complexity upon cLTP. - Synchronous growth - Nanostructures of pre- and postsynaptic scaffolding proteins and AMPA receptors increase simultaneously and equally strong upon cLTP. - GluA2-containing synaptic AMPA receptors form nanoclusters that increase in size and slightly in number upon cLTP and form subdomains on PSD95. - Bassoon forms complex structures similar to the PSD95 nano-organization.