Synapse- and Stimulus-Specific Local Translation During Long-Term Neuronal Plasticity

Sensorin Reporter Long-term memory and synaptic plasticity require changes in gene expression and yet can occur in a synapse-specific manner. Messenger RNA (mRNA) localization and regulated translation at synapses have been proposed as mechanisms for spatially restricting gene expression during transcription-dependent, synapse-specific forms of neuronal plasticity. In the sea slug Aplysia, which is a frequently used model system for studying learning and memory, sensorin is a sensory cell–specific peptide neurotransmitter. The mRNA encoding sensorin localizes to distal sensory neurites and further concentrates at sites of synaptic contact between sensory and motor neurons. Wang et al. (p. 1536, published online 14 May; see the Perspective by Korte) demonstrate, using translational reporters of sensorin mRNA expressed in individual cultured Aplysia sensory and motor neurons, that local translation occurs at synapses during transcription-dependent, learning-related forms of synaptic plasticity. Live-cell microscopy reveals local translation during long-term facilitation of Aplysia sensory-motor synapses. Long-term memory and synaptic plasticity require changes in gene expression and yet can occur in a synapse-specific manner. Messenger RNA localization and regulated translation at synapses are thus critical for establishing synapse specificity. Using live-cell microscopy of photoconvertible fluorescent protein translational reporters, we directly visualized local translation at synapses during long-term facilitation of Aplysia sensory-motor synapses. Translation of the reporter required multiple applications of serotonin, was spatially restricted to stimulated synapses, was transcript- and stimulus-specific, and occurred during long-term facilitation but not during long-term depression of sensory-motor synapses. Translational regulation only occurred in the presence of a chemical synapse and required calcium signaling in the postsynaptic motor neuron. Thus, highly regulated local translation occurs at synapses during long-term plasticity and requires trans-synaptic signals.

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