The JNK/c-Jun signaling axis contributes to the TDP-43-induced cell death.

Dysregulation of transactive response DNA-binding protein-43 (TDP-43) is closely linked to the pathogenesis of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U). The contribution of the upregulation of TDP-43 expression to the pathogenesis has been strongly suggested by the observation that the level of TDP-43 expression is increased in both ALS and FTLD-U patients. We previously found that the low-grade (twice to five times more than the endogenous level) overexpression of TDP-43 induces neuronal cell death through the upregulation of Bim and CHOP expression and the downregulation of Bcl-xL expression. In this study, we further show that the low-grade overexpression of TDP-43 increases the level of phosphorylated c-Jun N-terminal kinase (JNK) and the co-incubation with a JNK inhibitor, the expression of a dominant-negative JNK, or the expression of a dominant-negative c-Jun inhibited the TDP-43-induced death in NSC34 motor neuronal cells. These data together suggest that the JNK/c-Jun signaling axis contributes to the TDP-43-induced cell death.