Local protein synthesis in axon terminals and dendritic spines differentiates plasticity contexts

While there is ample evidence for localized mRNAs and protein synthesis in mature neuronal postsynaptic compartments, clear demonstrations of these processes in presynaptic terminals are extremely limited. Using expansion microscopy to resolve pre- and postsynaptic compartments we discovered that most presynaptic terminals contain mRNA and ribosomes. Using fluorescence-activated synaptosome sorting, we directly visualized or sequenced hundreds of mRNA species within excitatory boutons. Following brief metabolic labeling, over 30% of all presynaptic terminals exhibit a signal, providing evidence for ongoing protein synthesis. Using different classic plasticity paradigms, we discovered unique patterns of rapid pre- and/or postsynaptic translation. These data suggest that local protein synthesis in both pre- and postsynaptic elements is differentially recruited to drive the unique compartment-specific phenotypes that underlie different forms of plasticity.