The nuclear translocation of MAPKs as a drug target for signaling-related diseases.

Rony Seger, The Weizmann Institute of Science, Rehovot, Israel

The rapid nuclear translocation of signaling proteins upon stimulation is important for the regulation of de-novo gene expression. We have studied the stimulated nuclear shuttling of ERK, JNK and p38 MAPKs, and found that they translocate into the nucleus in Ran dependent, but NLS- or NTS-independent manner. We show that this translocation involves three beta-like importins (Imps 3,7&9). Imp7 is sufficient to induce the translocation of ERK, which is mediated by its binding to a phosphorylated NTS in the kinase insert domain of ERK. On the other hand, the translocation of JNK and p38 is mediated by binding of a distinct N-terminal NTS to dimers of Imp3/Imp7 or Imp3/Imp9. In order to study the importance of the nuclear translocation we undertook to study the effect of its prevention on signaling-related diseases. First we used an ERK NTS-derived phosphomimetic peptide to block Imp7-ERK1/2 interaction, and consequently, nuclear translocation of the kinases. In culture, the peptide induced apoptosis of melanoma cells, inhibited the proliferation/survival of other cancer cells, but had no effect on immortalized cells. The peptide even inhibited the growth of PLX4032 and U0126-resistant melanoma cells. In xenografts, the peptide inhibited the growth of breast, colon, and melanoma cancer cells, and eradicates B-Raf mutated melanoma. We then studied peptides derived from the NTS of JNK and p38 and found that they prevent the nuclear translocation of these kinases. Application of these peptides to a colitis model in mice prevented wound formation weight loss associated with this bowl disease. Therefore our studies provide a proof of concept for using the nuclear translocation of ERK, JNK and p38 as a signaling-related drug targets.