Project description:Mitogen-activated protein kinases (MAPKs) drive key signaling cascades during neuronal survival and degeneration. The re-localization of kinases to specific subcellular compartments is a critical mechanism to locally control signaling activity and specificity upon stimulation. However, how MAPK signaling components tightly control their localization remains largely unknown. Here, we systematically analyzed the phosphorylation and membrane localization of all MAPKs expressed in dorsal root ganglia neurons, under control and stress conditions. We found that MAP3K12/ dual leucine zipper kinase (DLK) is the only MAPK that becomes phosphorylated and palmitoylated, and it is recruited to sphingomyelin rich vesicles upon stress. The DLK stress-induced vesicle assembly is essential for kinase activation; blocking DLK-membrane interactions inhibits downstream signaling, while DLK recruitment to ectopic subcellular structures is sufficient to induce kinase activation. We show that the localization of DLK to newly formed vesicles is essential for local signaling and inhibition of membrane internalization blocks DLK activation and protects against neurodegeneration. These data establish vesicular assemblies as dynamically regulated platforms for DLK signaling during neuronal stress responses.
Project description:Alzheimer’s disease (AD) is the most prevalent form of neurodegeneration. Despite the well-established link between tau aggregation and clinical progression, the major pathways driven by this protein to intrinsically damage neurons are incompletely understood. To model AD-relevant neurodegeneration driven by tau, we overexpressed non-mutated human tau in primary mouse neurons and observed substantial axonal degeneration and cell death, a process accompanied by activated caspase 3. Mechanistically, we detected deformation of the nuclear envelope and increased DNA damage response in tau-expressing neurons. Gene profiling analysis further revealed significant alterations in the mitogen-activated protein kinase (MAPK) pathway; moreover, inhibitors of dual leucine zipper kinase (DLK) and c-Jun N-terminal kinase (JNK) were effective in alleviating wild-type human tau-induced neurodegeneration. In contrast, mutant P301L human tau was less toxic to neurons, despite causing comparable DNA damage. Axonal DLK activation induced by wild-type tau potentiated the impact of DNA damage response, resulting in overt neurotoxicity. In summary, we have established a cellular tauopathy model highly relevant to AD and identified a functional synergy between the MAPK-DLK axis and DNA damage response in the neuronal degenerative process.
Project description:Dual Leucine-zipper Kinase (DLK)-dependent stress signaling is a critical determinant of neuronal survival and regenerative potential following axon damage, but it remains uncertain whether injury-activated DLK is adequate to initiate and maintain a pro-regenerative transcriptional response in the CNS. Using a drug-activatable DLK construct, we stimulated stress signaling for comparison of the retinal transcriptional response to, and in addition to, the response stimulated by mouse optic nerve injury in wildtype mice and in the context of partial axon regeneration enabled by disruption of the tumor suppressor PTEN.
Project description:Most transcription factors possess at least one long intrinsically disordered transactivation domain that binds to a variety of co-activators and co-repressors and plays a key role in modulating the transcriptional activity. Despite the crucial importance of these mechanisms, the structural and functional basis of transactivation domain in yet poorly understood. Here, we focused on ATF4/CREB-2, an essential transcription factor for cellular stress adaptation. We found that the N-terminal region of the transactivation domain is involved in transient long-range interactions with the basic-leucine zipper domain. In vitro phosphorylation assays with the protein kinase CK2 show that the presence of the basic-leucine zipper domain is required for optimal phosphorylation of the transactivation domain. This study uncovers the intricate coupling existing between the transactivation and basic-leucine zipper domains of ATF4 and highlights its potential functional relevance.
Project description:Injury to peripheral axons initiates a complex cascade of cellular responses, including cytoskeletal disassembly, axon transport disruption, and ultimately axon regeneration. Central to this process is the MAP triple kinase Dual-Leucine Zipper Kinase (DLK), activated by injury and other neuronal stressors. Here, we propose the existence of a homeostatic mechanism termed the Cytoskeletal Perturbation Response (CPR). We investigate this hypothesis by examining the response of cultured dorsal root ganglion (DRG) neurons to low dose nocodazole treatment, a cytoskeletal perturbing agent. To gain insights into DLK-dependent transcriptional changes following cytoskeletal insult, we performed bulk RNA sequencing on cultured neurons treated for 16 hours. Using a fully crossed two-factor design, we determined the interactive effect of DLK on nocodazole- dependent transcriptional changes. Our study demonstrates that cytoskeletal perturbation triggers DLK-dependent signaling cascades, leading to significant transcriptional changes. These changes involve transcription factors (Jun, Egr1, Atf3) and MAP kinase regulators (DUSPs), pointing to a regulatory network that attenuates DLK signaling. Taken together, our findings suggest that cytoskeletal perturbation activates a DLK-dependent homeostatic mechanism, the CPR, which orchestrates transcriptional changes and morphological adaptations to repair neuronal damage. The CPR bears similarities to established homeostatic responses, offering insights into the intricate processes that underlie axon regeneration and cellular repair.
Project description:Excitotoxicity is a primary pathological process directing neuronal cell death in both acute neurological disorders and neurodegenerative diseases such as ischemic stroke and Alzheimer’s disease. We use mouse cultured cortical neuron treated with 100uM of Glutamate for a model of excitotoxicity and applied N-terminomics (TAILS) method to identify the neuronal proteins aberrantly modified in excitotoxicity
Project description:The significant changes of hematopoietic cells induced by Xbp1S expression indicate that there is global alteration in gene expression. UPR induces transcription of Xbp1, and phosphorylation of the ER transmembrane kinase IRE1 initiates UPR-mediated mRNA splicing of Xbp1, resulting in the production of Xbp1S, an active form of a basic leucine zipper transcription factor. In the present study, Xbp1S retrovirus vector infected 32cl3 cells show cell cycle arrest and myeloid differentiation. Xbp1S may modulate important genes of differentiation and the cell cycle.