Goodwani, S. | Search bioRxiv

bioRxiv2025

DLK inhibition has sex-specific effects on neuroprotection and locomotor recovery after spinal cord injury

Spinal cord injury (SCI) causes devastating functional deficits, in part due to neuroinflammation, oxidative stress, and excitotoxicity that drive death of lesion-adjacent viable neurons. Dual leucine zipper kinase (DLK) is a neuron-enriched kinase that responds to cellular stress by activating the c-Jun N-terminal kinase (JNK) pathway, driving both stress-responsive gene expression and neuronal apoptosis. We hypothesized that SCI would robustly activate DLK signaling and that acute pharmacological inhibition of DLK would suppress JNK pathway activation, thereby enhancing neuroprotection and locomotor recovery in our mouse model of moderate contusion SCI. Using western blotting, we observed that SCI induced strong and sustained activation of the JNK pathway in the injured spinal cord starting at 4 hours post-injury through 7 days. Complementary analysis of single-nucleus RNA-seq revealed that DLK expression is highly enriched in neurons across all injury phases. Following SCI, neurons exhibited robust, time-dependent upregulation of multiple DLK-responsive transcripts, consistent with sustained pathway activation during the acute and subacute periods. Systemic treatment with the selective DLK inhibitor IACS-52825 effectively suppressed intraspinal JUN activation in a dose-dependent manner. However, unexpectedly, treatment delayed functional recovery and expanded lesion volume by 71% in male mice with no significant effect in females. These findings highlight the complex roles of DLK signaling after SCI, revealing a need to understand the sex-specific molecular mechanisms that modulate injury outcomes. Future studies should further optimize timing, location, and cellular targeting of DLK therapeutic strategies to improve neuroprotection and neurologic recovery after SCI.

neuroscience↗

bioRxiv2018

Homeostatic versus pathological functions of Dual Leucine Zipper Kinase in the adult mouse brain

Dual Leucine Zipper Kinase (DLK, Map3k12), is an injury-induced axonal protein that governs the balance between degeneration and regeneration through its downstream effectors c-jun N-terminal kinase (JNK) and phosphorylated c-jun (p-c-Jun). DLK is generally considered to be inactive in healthy neurons until induced by injury. However we report that DLK in the cerebellum appears constitutively active and drives nuclear p-c-Jun in cerebellar granule neurons in the absence of injury. In contrast the adult hippocampus expresses similar levels of apparently constitutively active DLK, but p-c-Jun is lower and does not accumulate in the nucleus. Injury is required there for p-c-jun nuclear expression, because in the rTg4510 model of tauopathy, where there is extensive hippocampal pathology, nuclear p-c-Jun is induced in a DLK-dependent manner. This context-specific regulation of DLK signaling could relate to availability of JNK scaffolding proteins, as the cerebellum preferentially expresses JNK-interacting protein-1 (JIP-1) whereas the hippocampus contains more JIP-3 and Plenty of SH3 (POSH). To understand how DLK signaling differs between the hippocampus and cerebellum, we selectively blocked DLK and measured changes in protein and mRNA expression. In the cerebellum, p-c-Jun levels correlated with synaptophysin, suggesting a link between DLK activity and synaptic maintenance. In rTg4510 mice, hippocampal p-c-Jun instead correlated with markers of neuronal injury and gliosis (Iba1 and GFAP). RNA sequencing revealed that in both brain regions DLK inhibition reduced expression of JNK/c-Jun pathway components and a novel set of co-regulated genes. In the cerebellum, Jun mRNA levels were co-regulated with genes mapping to metabolic pathways, while in the rTg4510 hippocampus, Jun-correlated mRNAs correspond primarily to neuroinflammation. These data suggest that in the uninjured cerebellum, DLK/p-c-Jun signaling is linked to synaptic regulation, but in the hippocampus, pathologically activated DLK/p-c-Jun signaling regulates genes associated with the injury response.

neuroscience↗