Potassium ion stimulation triggers protein translation in synaptoneurosomal polyribosomes.

Synaptoneurosomes, a subcellular fraction of resealed presynaptic plus postsynaptic entities, contain polyribosomal aggregates and are capable of protein synthesis. Upon treatment with K(+), which has been shown to cause depolarization, we observed a rapid increase followed by a decrease in the size of polyribosomal complexes. These were shown by sucrose density gradient analysis to represent a shift of part of the total RNA into polyribosomes; accelerated incorporation of amino acids into polypeptides was also demonstrated. Calcium chelators in the medium reduce the steady-state size of polyribosomal complexes, but do not eliminate the response to depolarization, while intracellular calcium chelators have more profound effects, suggesting that there is mobilization of intracellular calcium stores. Thus depolarization-related changes may affect binding and release of translation initiation complexes with messenger RNA found near synaptic junctions.