Retrograde axonal transport of JNK signaling molecules influence injury induced nuclear changes in p-c-Jun and ATF3 in adult rat sensory neurons

In the present study, we investigated if the previously observed JNK-mediated activation of c-Jun and induction of ATF3 could be ascribed to axonal transport of JNK signaling components, or if axonal transport of the transcription factors themselves contributes to the nuclear changes in injured sensory neurons. We observed retrograde axonal transport of a number of JNK upstream kinases in ligated rat sciatic nerve. In these preparations, axonal transport of JNK/p-JNK, the JNK scaffolding protein JIP, and the transcription factors ATF3 and ATF2/p-ATF2 was also found. No or little retrograde transport of c-Jun and p-c-Jun was found, whereas an anterograde transport of Hsp27, a protein previously reported in the context of p-c-Jun and ATF3, was observed. In separate experiments, we found that in vitro inhibition of axonal transport or axonal inhibition of JNK reduced the number of p-c-Jun- and ATF3-positive neuronal nuclei. The results suggest that retrograde axonal transport of JNK signaling components contributes to the injury induced c-Jun phosphorylation and ATF3 induction.