Regulation of eukaryotic initiation factor 4E phosphorylation in the nervous system of Aplysia californica

We have used an antibody that specifically recognizes eukaryotic initiation factor 4E (elF4E) when it is phosphorylated at Ser(207) to characterize elf4E phosphorylation in the nervous system of Aplysia. The level of phosphorylated elF4E, but not the level of total elF4E, was significantly correlated with the basal rate of translation measured from different animals. Serotonin (5-HT), a transmitter that regulates the rate of translation in Aplysia neurons, had mixed effects on elF4E phosphorylation. 5-HT decreased elF4E phosphorylation in sensory cell clusters through activation of protein kinase C. 5-HT increased elF4E phosphorylation in the whole pleural ganglia. In the Aplysia nervous system, elF4E phosphorylation correlated with phosphorylation of the p38 MAP kinase, but not the p42 MAP kinase (ERK). Furthermore, an inhibitor of the p38 MAP kinase significantly decreased basal elF4E phosphorylation, but an inhibitor of the MAP or ERK kinase (MEK) did not. Despite the correlation of elF4E phosphorylation with the basal rate of translation, inhibition of elF4E phosphorylation by an inhibitor of the p38 MAP kinase did not significantly decrease the rate of translation.