The mRNA for elongation factor 1α is localized in dendrites and translated in response to treatments that induce long-term depression

There is increasing evidence that long-lasting forms of activity-dependent synaptic plasticity, such as long-term potentiation ( LTP) and long-term depression ( LTD), require local synthesis of proteins within dendrites. Identifying novel dendritic mRNAs and determining how their distribution and translation is regulated is a high priority. We demonstrate here that the mRNA for the elongation factor 1 alpha ( EF1 alpha) is present in vivo in the dendrites of neurons that exhibit LTP and LTD, and that its translation is locally regulated. The subcellular distribution of EF1 alpha mRNA differs from any of the dendritic mRNAs that have been described previously. In the hippocampus, the mRNA is highly expressed in cell bodies and is also concentrated in the zone of termination of commissural/associational afferents in the inner molecular layer, suggesting that mRNA localization is in some way related to the distribution of different types of synapses. Nevertheless, the localization of EF1 alpha mRNA is not altered by prolonged periods of synaptic activation that are sufficient to cause a dramatic redistribution of Arc mRNA. Local application of the metabotropic glutamate receptor agonist ( R, S)-3,5-dihydroxyphenylglycine ( DHPG) led to dramatic increases in immunostaining for EF1 alpha protein in dendrites, and treatment of hippocampal slices with DHPG, which is known to induce LTD, led to increases in EF1 alpha protein levels. Both responses were blocked by the protein synthesis inhibitor anisomycin. In contrast, stimulation of the perforant path using patterns of stimulation that induce LTP caused rapid increases of immunostaining for EF1 alpha protein in the activated dendritic lamina, but these increases were not blocked by anisomycin or rapamycin. The findings suggest that local synthesis of EF1 alpha protein may be important for the synaptic mechanisms that underlie protein synthesis-dependent LTD.