Palmitoylation Couples DLK to JNK3 to Facilitate Pro-degenerative Axon-to-Soma Signaling

Dual Leucine-zipper Kinase (DLK, a MAP3K) mediates neuronal responses to diverse injuries and insults via c-Jun N-terminal Kinase (JNK) family Mitogen-activated Protein Kinases (MAPKs). It is unclear why DLK couples to JNKs in mammalian neurons versus other MAPKs, especially because some invertebrate DLK orthologs couple instead to the related p38 family MAPKs. Here we identify two mechanisms that potentially explain this DLK-JNK coupling. First, neural-specific JNK3, but not p38-MAPK, catalyzes positive feedback phosphorylation of DLK that further activates DLK and locks the DLK-JNK3 module in a highly active state. Furthermore, the pro-degenerative JNK2 and JNK3, but not the related JNK1, are endogenously palmitoylated. Moreover, palmitoylation targets both DLK and JNK3 to the same axonal vesicles and JNK3 palmitoylation is essential for pro-degenerative axonal retrograde signaling in vivo. These findings provide insights into DLK-JNK signaling relevant to multiple neuropathological conditions and answer long-standing questions regarding the selective pro-degenerative roles of JNK2/3.