Abstract
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.
Highlights
Processing bodies (P-bodies) were first described as cytoplasmic sites of mRNA decapping and degradation
Zinc application causes disruption of polysomes It was previously shown that tau RNP includes HuD and IMP1 RNA-binding proteins, which are found in association with polysomes
These results indicate that zinc treatment causes a shift in the distribution of heavy polysomes towards the lighter monosomes fraction, which indicates the disruption of polysomes and an affect on protein synthesis
Summary
Processing bodies (P-bodies) were first described as cytoplasmic sites of mRNA decapping and degradation. They were shown to contain various enzymes that are engaged in mRNA decay, such as: Dcp1a, Dcp and XrnI (Sheth and Parker, 2003; Hillebrand et al, 2007). Immunostaining of cells using antibodies for Dcp1a and Dcp, which are key markers for P-bodies, revealed P-bodies to be large macroscopic cytoplasmic granules (Teixeira et al, 2005). Much less is known about the physiological role of P-bodies in neurons. In Drosophila neurons, staufen and dFMR1 ribonucleoparticles (RNPs) contain somatic P-body enzymes, such as Dcp and pacman proteins, which are the Drosophila homologues for Dcp1a and Xrn, respectively (Barbee et al, 2006). Previous data demonstrated the presence of Dcp containing neuronal granules in dendrites (Vessey et al, 2006)
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