Combinatorial chemistry identifies additional compounds that selectively inhibit DLK-dependent retrograde signaling while minimally affecting other axonal roles of DLK

Dual leucine-zipper kinase (DLK) is implicated in at least two distinct processes that drive neurodegeneration: retrograde (axon-to-soma) signaling to activate pro-degenerative transcription programs, and axon-intrinsic action to drive Wallerian and Wallerian-like axon degeneration. Inhibiting DLK-dependent signaling is thus an attractive neuroprotective strategy, but compounds that inhibit all cellular pools of DLK cause unintended side effects. We recently successfully deployed a complementary approach to identify compounds that selectively block DLK retrograde (axon-to-soma) signaling and subsequent neurodegeneration by inhibiting acute, axonal palmitoylation of DLK. Here, we explored chemical space for one of our two most effective compounds and identified multiple analogs that are equally neuroprotective in a model of transcription-dependent neurodegeneration that requires DLK-dependent retrograde signaling. In contrast, our original hits and these additional analogs had minimal effect in two models of DLK-dependent, but transcription-independent, distal axon degeneration. Moreover, our original hits did not phenocopy the stabilization of axon survival factor proteins that is a well-described effect of conventional DLK kinase domain inhibitors. These findings reveal additional potential neuroprotective compounds and further support the notion that the pool of DLK that conveys axonal retrograde signals can be selectively targeted therapeutically.