Protein masking of a ribosomal RNA epitope is an early event in afferent deprivation-induced neuronal death.

Cell death in the developing nervous system is regulated by both afferent synaptic activity and target-derived neurotrophic factors. Loss of afferent innervation via unilateral cochlea removal results in the death of 20-40% of neurons in the neonatal chick cochlear nucleus, nucleus magnocellularis (NM). The process of NM neuronal death involves structural and functional alterations in ribosomes, including decreased protein synthesis, loss of immunoreactivity for a monoclonal anti-ribosomal RNA (rRNA) antibody, Y10B, and eventual ribosome degradation. In the present report we confirm that the Y10B antibody binds specifically to ribosomes in chick NM neurons by electron microscopy. We then performed experiments designed to determine whether loss of rRNA immunoreactivity observed in NM neurons following cochlea removal involves induction of a protein-rRNA interaction. Brain stem tissue from animals subjected to unilateral cochlea removal was treated with protease prior to immunolabeling. Protease treatment restored rRNA immunoreactivity after 3 h of afferent deprivation, confirming that afferent deprivation induces protein-rRNA interactions which mask the Y10B epitope. Immunoprecipitation experiments confirmed that the Y10B antibody recognizes a specific rRNA sequence without posttranscriptional modification.