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 affer ent synaptic activity and target-derived neurotrophic factors. Loss of afferent innervation via unilateral cochlea removal results in the de ath of 20-40% of neurons in the neonatal chick cochlear nucleus, nucle us magnocellularis (NM). The process of NM neuronal death involves str uctural and functional alterations in ribosomes, including decreased p rotein synthesis, loss of immunoreactivity for a monoclonal anti-ribos omal RNA (rRNA) antibody, Y10B, and eventual ribosome degradation. In the present report we confirm that the Y10B antibody binds specificall y to ribosomes in chick NM neurons by electron microscopy. We then per formed experiments designed to determine whether loss of rRNA immunore activity observed in NM neurons following cochlea removal involves ind uction of a protein-rRNA interaction. Brain stem tissue from animals s ubjected 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 deprivatio n induces protein-rRNA interactions which mask the Y10B epitope. Immun oprecipitation experiments confirmed that the Y10B antibody recognizes a specific rRNA sequence without posttranscriptional modification.