Neuronal ribosomes exhibit dynamic and context-dependent exchange of ribosomal proteins

Ribosomes, assembled in the nucleus and perinuclear region, are thought to remain invariant throughout their lifetime. Here the authors document the dynamic association or exchange of ribosomal proteins within mature ribosomes of neuronal cells. Owing to their morphological complexity and dense network connections, neurons modify their proteomes locally, using mRNAs and ribosomes present in the neuropil (tissue enriched for dendrites and axons). Although ribosome biogenesis largely takes place in the nucleus and perinuclear region, neuronal ribosomal protein (RP) mRNAs have been frequently detected remotely, in dendrites and axons. Here, using imaging and ribosome profiling, we directly detected the RP mRNAs and their translation in the neuropil. Combining brief metabolic labeling with mass spectrometry, we found that a group of RPs rapidly associated with translating ribosomes in the cytoplasm and that this incorporation was independent of canonical ribosome biogenesis. Moreover, the incorporation probability of some RPs was regulated by location (neurites vs. cell bodies) and changes in the cellular environment (following oxidative stress). Our results suggest new mechanisms for the local activation, repair and/or specialization of the translational machinery within neuronal processes, potentially allowing neuronal synapses a rapid means to regulate local protein synthesis.

Automated summary

This research reveals the dynamic association or exchange of ribosomal proteins within mature ribosomes of neuronal cells, suggesting neurons can modify their proteomes using mRNAs and ribosomes present in the neuropil. The study also found translation activity of ribosomal protein mRNAs in the neuropil, indicating new mechanisms for local protein synthesis regulation within neuronal processes.