We have recently shown that DLK/JNK signaling becomes activated in multiple animal models of neurodegenerative disease, and that deleting DLK or inhibiting it is protective and can delay, and even in some cases reverse, disease progression (Le Pichon et al., 2017). The mouse models examined in this study included the SOD1(G93A) model of amyotrophic lateral sclerosis (ALS), and two mouse lines that model aspects of Alzheimers disease (AD), a PS2APP model and the Tau(P301L) model. We also correlated these findings with evidence of DLK/JNK signaling in human tissue of ALS and AD patients. Despite these diseases being characterized by very distinct genetic and pathological features, loss of DLK signaling appeared to protect neurons in both types of models. This work strongly suggested that DLK signaling is a pathway common to at least several distinct neurodegenerative diseases, that can potentially act as an integrator of neuronal stress signaling. Previous work had shown that DLK is a neuronally-enriched kinase and an upstream regulator of the well-studied JNK (c-Jun N-terminal kinase) signaling pathway. The function of DLK is critical for healthy developmental neurodegeneration as well as for an appropriate response to acute nerve injury. Given that the DLK response appears to be a feature common to so many different contexts and diseases, we aim to understand the mechanism(s) by which DLK activation occurs, especially in pathological settings of chronic disease. We also seek to better understand the events downstream of DLK. For example, DLK signaling directs the transcriptional activation of genes associated with both degeneration and regeneration. What determines the ultimate outcome for the neuron, and does this response vary from cell to cell, or within a given neuron over time? Finally, if DLK is a true integrator of cellular stress, how does it fit in relative to these other stress pathways? One novel aspect downstream of DLK signaling that we have recently uncovered (Wlaschin et al., 2018) is a direct link between activation of DLK in neurons and recruitment of a neuroinflammatory response in areas in contact with these neurons. DLK activation in dorsal root ganglion neurons (DRGs) by peripheral nerve injury results in microgliosis in the dorsal horn, the region of the spinal cord to which the DRGs project, via upregulation of Csf1 (colony stimulating factor 1) in DRG neurons. While the DLK-dependent response to injury in neurons has mainly been studied for its cell autonomous effects, we now show it extends beyond the injured neuron to recruit other cellular players into a tissue-wide response, which has important implications for neurological disease.
| Wlaschin, Josette J; Gluski, Jacob M; Nguyen, Eileen et al. (2018) Dual leucine zipper kinase is required for mechanical allodynia and microgliosis after nerve injury. Elife 7: |
| Le Pichon, Claire E; Meilandt, William J; Dominguez, Sara et al. (2017) Loss of dual leucine zipper kinase signaling is protective in animal models of neurodegenerative disease. Sci Transl Med 9: |
| Ghitani, Nima; Barik, Arnab; Szczot, Marcin et al. (2017) Specialized Mechanosensory Nociceptors Mediating Rapid Responses to Hair Pull. Neuron 95:944-954.e4 |
| Lee, Seung-Hye; Le Pichon, Claire E; Adolfsson, Oskar et al. (2016) Antibody-Mediated Targeting of Tau In Vivo Does Not Require Effector Function and Microglial Engagement. Cell Rep 16:1690-700 |
| Chesler, Alexander T; Szczot, Marcin; Bharucha-Goebel, Diana et al. (2016) The Role of PIEZO2 in Human Mechanosensation. N Engl J Med 375:1355-1364 |
