Zinc as a translation regulator in neurons: implications for P-body aggregation.

Post-transcriptional mechanisms of gene expression in neuronal cells include mRNA transport and local protein synthesis, which play a vital role in the control of polarity, synaptic plasticity and growth cone motility. RNA-binding proteins, which form the transported ribonucleoparticle (RNP), control mRNA stability and local translation. Recently, the existence of processing bodies (P-bodies), in which mRNA decapping and degradation take place, was revealed in neurons. It was suggested that P-bodies serve as a transient storage compartment for mRNAs, which can be released and, upon stimulation, resume translation. In this study, we focused on the localization of the Dcp1a protein, which serves as a P-body marker, in PC12 growth cones and P19 neuronal cells and its association with the tau mRNA-binding protein HuD. We found that stimulation of neurons by zinc, which is stored and released from synaptic vesicles, caused a disruption of polysomes into monosomes, whereas HuD protein distribution in sucrose gradient fractions remained unaffected. In addition, zinc application caused an aggregation of Dcp1a protein in an RNA-dependent manner. These findings suggest a role for zinc in translation regulation via disruption of polysomes, aggregation of P-bodies in neurons and impairment of the RNP-polysome interaction.