The Ste20 Family Kinases MAP4K4, MINK1, and TNIK Converge to Regulate Stress-Induced JNK Signaling in Neurons

The Citron homology domain of MAP4Ks improves outcomes of traumatic brain injury

JOURNAL/nrgr/04.03/01300535-202511000-00027/figure1/v/2024-12-20T164640Z/r/image-tiff The mitogen-activated protein kinase kinase kinase kinases (MAP4Ks) signaling pathway plays a pivotal role in axonal regrowth and neuronal degeneration following insults. Whether targeting this pathway is beneficial to brain injury remains unclear. In this study, we showed that adeno-associated virus-delivery of the Citron homology domain of MAP4Ks effectively reduces traumatic brain injury-induced reactive gliosis, tauopathy, lesion size, and behavioral deficits. Pharmacological inhibition of MAP4Ks replicated the ameliorative effects observed with expression of the Citron homology domain. Mechanistically, the Citron homology domain acted as a dominant-negative mutant, impeding MAP4K-mediated phosphorylation of the dishevelled proteins and thereby controlling the Wnt/β-catenin pathway. These findings implicate a therapeutic potential of targeting MAP4Ks to alleviate the detrimental effects of traumatic brain injury.

Protein kinases in neurodegenerative diseases: current understandings and implications for drug discovery

Neurodegenerative diseases (e.g., Alzheimer's, Parkinson's, Huntington's disease, and Amyotrophic Lateral Sclerosis) are major health threats for the aging population and their prevalences continue to rise with the increasing of life expectancy. Although progress has been made, there is still a lack of effective cures to date, and an in-depth understanding of the molecular and cellular mechanisms of these neurodegenerative diseases is imperative for drug development. Protein phosphorylation, regulated by protein kinases and protein phosphatases, participates in most cellular events, whereas aberrant phosphorylation manifests as a main cause of diseases. As evidenced by pharmacological and pathological studies, protein kinases are proven to be promising therapeutic targets for various diseases, such as cancers, central nervous system disorders, and cardiovascular diseases. The mechanisms of protein phosphatases in pathophysiology have been extensively reviewed, but a systematic summary of the role of protein kinases in the nervous system is lacking. Here, we focus on the involvement of protein kinases in neurodegenerative diseases, by summarizing the current knowledge on the major kinases and related regulatory signal transduction pathways implicated in diseases. We further discuss the role and complexity of kinase-kinase networks in the pathogenesis of neurodegenerative diseases, illustrate the advances of clinical applications of protein kinase inhibitors or novel kinase-targeted therapeutic strategies (such as antisense oligonucleotides and gene therapy) for effective prevention and early intervention.

SAMD12 as a Master Regulator of MAP4Ks by Decoupling Kinases From the CNKSR2 Scaffold

The MAP4K member TNIK and the multi-domain scaffold protein CNKSR2, both of which are clustered at neuronal synapses, interact with each other and are closely associated with neurodevelopmental disorders, although the mechanism underlying their interaction is unclear. In this study, we characterized the interaction mechanisms between MAP4K kinases (MAP4K4, MINK1 and TNIK) and the CNKSR1/2/3 scaffold proteins, and discovered that SAMD12, a familial adult myoclonic epilepsy disease gene product, or its close homolog SAMD10, binds to CNKSR1/2/3 with exceptionally strong affinities and can quantitatively displace MAP4K from CNKSR1/2/3 scaffolds. Additionally, we demonstrated that CNKSR2 acts as both a scaffold and an activator of TNIK during neuronal synapse development. Ectopic expression of SAMD12 can effectively alter synapse development, likely by inhibiting TNIK activity through the dissociation of the kinase from CNKSR2. Our findings may have broad implications on the roles of MAP4Ks and CNKSR1/2/3 in the nervous system and in other tissues under physiological and pathophysiological processes.

Inhibiting acute, axonal DLK palmitoylation is neuroprotective and avoids deleterious effects of cell-wide DLK inhibition

Inhibiting dual leucine-zipper kinase (DLK) could potentially ameliorate diverse neuropathological conditions, but a direct inhibitor of DLK's kinase domain caused unintended side effects in human patients, indicative of neuronal cytoskeletal disruption. We sought a more precise intervention and show here that axon-to-soma pro-degenerative signaling requires acute, axonal palmitoylation of DLK. To identify potential modulators of this modification, we screened >28,000 compounds using a high-content imaging readout of DLK's palmitoylation-dependent subcellular localization. Several hits alter DLK localization in non-neuronal cells, reduce DLK retrograde signaling and protect cultured dorsal root ganglion neurons from neurodegeneration. Mechanistically, the two most neuroprotective compounds selectively prevent DLK's stimulus-dependent palmitoylation and subsequent recruitment to axonal vesicles, but do not affect palmitoylation of other axonal proteins assessed and avoid the cytoskeletal disruption associated with direct DLK inhibition. Our hit compounds also reduce pro-degenerative retrograde signaling in vivo, revealing a previously unrecognized neuroprotective strategy.

Exploring the role of EBV in multiple sclerosis pathogenesis through EBV interactome

Background

Epstein-Barr virus (EBV) is a known risk factor for multiple sclerosis (MS), even though the underlying molecular mechanisms are unclear and engage multiple immune pathways. Furthermore, the ultimate role of EBV in MS pathogenesis is still elusive. In contrast, Cytomegalovirus (CMV) has been identified as a protective factor for MS.

Objectives

This study aims to identify MS-associated genes that overlap with EBV interactome and to examine their expression in immune and glial cell subtypes.

Methods

We used P-HIPSTer, GWAS, and the Human Protein Atlas (HPA) to derive data on the EBV interactome, MS-associated genes and single-cell gene expression in immune and glial cells. The geneOverlap and dplyr R packages identified overlapping genes. A similar analysis was done for CMV and Adenovirus as negative control. Metascape and GTEx analyzed biological pathways and brain-level gene expression; transcriptomic analysis was performed on glial cells and peripheral blood in MS and controls. All the analyses performed in this study were generated using publicly available data sets.

Results

We identified a "core" group of 21 genes shared across EBV interactome, MS genes, and immune and glial cells (p<0.001). Pathway analysis revealed expected associations, such as immune system activation, and unforeseen results, like the prolactin signaling pathway. BCL2 in astrocytes, MINK1 in microglia were significantly upregulated while AHI1 was downregulated in MS compared to controls.

Conclusions

Our findings offer novel insights into EBV and CMV interaction with immune and glial cells in MS, that may shed light on mechanisms involved in disease pathophysiology.

CellFIE: Integrating Pathway Discovery With Pooled Profiling of Perturbations Uncovers Pathways of Huntington's Disease, Including Genetic Modifiers of Neuronal Development and Morphology

Genomic screens and GWAS are powerful tools for identifying disease-modifying genes, but it is often challenging to understand the pathways by which these genes function. Here, we take an integrated approach that combines network analysis and an imaging-based pooled genetic perturbation study to examine modifiers of Huntington's disease (HD). The computational analysis highlighted several genes in a subnetwork enriched for modifiers of neuronal development and morphology. To test the functional roles of these genes, we developed an experimental pipeline that allows pooled CRISPRi KD of 21 genes in human iPSC-derived neurons followed by optical analysis of genotypes, neuronal arborization, multiplexed pathway activity and morphological fingerprint readout. This approach recovered known genes involved in morphology and confirmed unexpected links from the network between several genetic modifiers of HD and morphology. Our approach overcomes challenges in pooled measurement of neuronal function and health and could be adapted for other phenotypes in HD and other neurological diseases.

In Silico Enabled Discovery of KAI-11101, a Preclinical DLK Inhibitor for the Treatment of Neurodegenerative Disease and Neuronal Injury

Dual leucine zipper kinase (DLK), expressed primarily in neuronal cells, is a regulator of neuronal degeneration in response to cellular stress from chronic disease or neuronal injury. This makes it an attractive target for the treatment of neurodegenerative diseases such as Alzheimer's, Parkinson's, and amyotrophic lateral sclerosis, and neuronal injury, such as chemotherapy-induced peripheral neuropathy. Here, we describe the discovery of a potent, selective, brain-penetrant DLK inhibitor, KAI-11101 (59). Throughout the program's progression, medicinal chemistry challenges such as potency, hERG inhibition, CNS penetration, CYP3A time-dependent inhibition, and kinase selectivity were overcome through the implementation of cutting-edge in silico tools. KAI-11101 displayed an excellent in vitro safety profile and showed neuroprotective properties in an ex vivo axon fragmentation assay as well as dose-dependent activity in a mouse PD model.

Transcriptome-Based Survival Analysis Identifies MAP4K4 as a Prognostic Marker in Gastric Cancer with Microsatellite Instability

Background/Objectives: Gastric cancer (GC) is a highly aggressive malignancy with diverse molecular subtypes. While microsatellite instability (MSI) GC generally carries a favorable prognosis, a subset of patients experiences poor outcomes, highlighting the need for refined prognostic markers. Methods: This study utilized transcriptomic and clinical data from two independent cohorts, The Cancer Genome Atlas (TCGA) and the Asian Cancer Research Group (ACRG), to identify novel prognostic genes in MSI-GC. Results: Through rigorous survival analysis, we identified high MAP4K4 expression (MAP4K4high) as an independent and robust predictor of poor overall survival (OS) and disease-free survival (DFS) specifically within the MSI-GC subtype. MAP4K4high was associated with increased hazard ratios for both OS and DFS in both cohorts, even after adjusting for clinicopathological factors. Further analysis revealed that MAP4K4high MSI-GC tumors exhibit a distinct molecular profile characterized by increased extracellular matrix remodeling, epithelial-mesenchymal transition, and a microenvironment enriched in monocytes and cancer-associated fibroblasts (CAFs). Notably, a subgroup of MSI-GC patients with a CIN-like phenotype and high MAP4K4 expression exhibited particularly dismal outcomes. Conclusions: Our findings establish MAP4K4 as a promising prognostic biomarker for risk stratification in MSI-GC and suggest its potential role in driving aggressive tumor behavior through modulation of the tumor microenvironment.

A small-molecule TNIK inhibitor targets fibrosis in preclinical and clinical models

Idiopathic pulmonary fibrosis (IPF) is an aggressive interstitial lung disease with a high mortality rate. Putative drug targets in IPF have failed to translate into effective therapies at the clinical level. We identify TRAF2- and NCK-interacting kinase (TNIK) as an anti-fibrotic target using a predictive artificial intelligence (AI) approach. Using AI-driven methodology, we generated INS018_055, a small-molecule TNIK inhibitor, which exhibits desirable drug-like properties and anti-fibrotic activity across different organs in vivo through oral, inhaled or topical administration. INS018_055 possesses anti-inflammatory effects in addition to its anti-fibrotic profile, validated in multiple in vivo studies. Its safety and tolerability as well as pharmacokinetics were validated in a randomized, double-blinded, placebo-controlled phase I clinical trial (NCT05154240) involving 78 healthy participants. A separate phase I trial in China, CTR20221542, also demonstrated comparable safety and pharmacokinetic profiles. This work was completed in roughly 18 months from target discovery to preclinical candidate nomination and demonstrates the capabilities of our generative AI-driven drug-discovery pipeline.

Clinical Potential of Misshapen/NIKs-Related Kinase (MINK) 1-A Many-Sided Element of Cell Physiology and Pathology

Misshapen/NIKs-related kinase (MINK) 1 belongs to the mammalian germinal center kinase (GCK) family. It contains the N-terminal, conserved kinase domain, a coiled-coil region, a proline-rich region, and a GCK, C-terminal domain with the Citron-NIK-Homology (CNH) domain. The kinase is an essential component of cellular signaling pathways, which include Wnt signaling, JNK signaling, pathways engaging Ras proteins, the Hippo pathway, and STRIPAK complexes. It thus contributes to regulating the cell cycle, apoptosis, cytoskeleton organization, cell migration, embryogenesis, or tissue homeostasis. MINK1 plays an important role in immunological responses, inhibiting Th17 and Th1 cell differentiation and regulating NLRP3 inflammasome function. It may be considered a link between ROS and the immunological system, and a potential antiviral target for human enteroviruses. The kinase has been implicated in the pathogenesis of sepsis, rheumatoid arthritis, asthma, SLE, and more. It is also involved in tumorigenesis and drug resistance in cancer. Silencing MINK1 reduces cancer cell migration, suggesting potential for new therapeutic approaches. Targeting MINK1 could be a promising treatment strategy for patients insensitive to current chemotherapies, and could improve their prognosis. Moreover, MINK1 plays an important role in the nervous system and the cardiovascular system development and function. The modulation of MINK1 activity could influence the course of neurodegenerative diseases, including Alzheimer's disease. Further exploration of the activity of the kinase could also help in gaining more insight into factors involved in thrombosis or congenital heart disease. This review aims to summarize the current knowledge on MINK1, highlight its therapeutic and prognostic potential, and encourage more studies in this area.

Discovery of 5-phenyl-3-ureidothiophene-2-carboxamides as protective agents for ALS patient iPSC-derived motor neurons

We discovered novel neuroprotective compounds by phenotypic screening using SOD1-mutant amyotrophic lateral sclerosis (ALS) patient induced pluripotent stem cell (iPSC)-derived motor neurons. Mechanistic analysis showed that the protective effect of initial hit compound 1 was likely due to the inhibition of MAP4Ks, including MAP4K4, a member of the MAP4K kinase family. Structural transformation led to compound 15f, which showed improved MAP4K4 inhibitory activity and superior neuroprotective effects compared to 1 in motor neurons. The results suggest that structural optimization based on MAP4K4 inhibitory activity might improve the neuroprotective effect of this series of compounds.

Rab11 suppresses neuronal stress signaling by localizing dual leucine zipper kinase to axon terminals for protein turnover

Dual leucine zipper kinase (DLK) mediates multiple neuronal stress responses, and its expression levels are constantly suppressed to prevent excessive stress signaling. We found that Wallenda (Wnd), the Drosophila ortholog of DLK, is highly enriched in the axon terminals of Drosophila sensory neurons in vivo and that this subcellular localization is necessary for Highwire-mediated Wnd protein turnover under normal conditions. Our structure-function analysis found that Wnd palmitoylation is essential for its axon terminal localization. Palmitoylation-defective Wnd accumulated in neuronal cell bodies, exhibited dramatically increased protein expression levels, and triggered excessive neuronal stress responses. Defective intracellular transport is implicated in neurodegenerative conditions. Comprehensive dominant-negative Rab protein screening identified Rab11 as an essential factor for Wnd localization in axon terminals. Consequently, Rab11 loss-of-function increased the protein levels of Wnd and induced neuronal stress responses. Inhibiting Wnd activity significantly ameliorated neuronal loss and c-Jun N-terminal kinase signaling triggered by Rab11 loss-of-function. Taken together, these suggest that DLK proteins are constantly transported to axon terminals for protein turnover and a failure of such transport can lead to neuronal loss. Our study demonstrates how subcellular protein localization is coupled to protein turnover for neuronal stress signaling.

Rab11 suppresses neuronal stress signaling by localizing Dual leucine zipper kinase to axon terminals for protein turnover

Dual Leucine Zipper Kinase (DLK) mediates multiple neuronal stress responses, and its expression levels are constantly suppressed to prevent excessive stress signaling. We found that Wallenda (Wnd), the Drosophila ortholog of DLK, is highly enriched in the axon terminals of Drosophila sensory neurons in vivo and that this subcellular localization is necessary for Highwire-mediated Wnd protein turnover under normal conditions. Our structure-function analysis found that Wnd palmitoylation is essential for its axon terminal localization. Palmitoylation-defective Wnd accumulated in neuronal cell bodies, exhibited dramatically increased protein expression levels, and triggered excessive neuronal stress responses. Defective intracellular transport is implicated in neurodegenerative conditions. Comprehensive dominant-negative Rab protein screening identified Rab11 as an essential factor for Wnd localization in axon terminals. Consequently, Rab11 loss-of-function increased the protein levels of Wnd and induced neuronal stress responses. Inhibiting Wnd activity significantly ameliorated neuronal loss and c-Jun N-terminal kinase signaling triggered by Rab11 loss-of-function. Taken together, these suggest that DLK proteins are constantly transported to axon terminals for protein turnover and a failure of such transport can lead to neuronal loss. Our study demonstrates how subcellular protein localization is coupled to protein turnover for neuronal stress signaling.

Highlights

Wnd is highly enriched in axon terminals.Wnd protein turnover by Hiw is restricted in the axon terminals.Protein palmitoylation of Wnd and Rab11 activity is essential for Wnd axonal localization. Rab11 mutations and defective Wnd palmitoylation impair Wnd protein turnover leading to increased Wnd protein levels and neuronal loss. Inhibiting Wnd activity mitigates neuronal stress response caused by Rab11 loss-of-function.

Transcriptome analysis to explore the mechanism of downregulated TNIK influencing the effect of risperidone

Background

Risperidone is one of the most reliable and effective antipsychotics for schizophrenia treatment. However, the mechanism of action of risperidone is not yet fully understood. Traf2 and Nck-interacting protein kinase (TNIK), a schizophrenia susceptibility gene, is associated with risperidone treatment response. Our previous in vitro experiments confirmed that downregulated TNIK affected the effect of risperidone on downstream targets. However, the effect of downregulated TNIK on risperidone-induced molecular expression remains to be further explored.

Methods

Transcriptome analysis was performed on U251 cells subjected to risperidone, TNIK siRNA, and no treatment, respectively. Compared to the no-treatment group, two groups of DEGs were screened out and then intersected with the schizophrenia-related genes to screen the cross-talk genes. Those DEGs were analyzed using GO and KEGG. STRING and Cytoscape were used to construct a protein-protein interaction (PPI) network for the cross-talk gene.

Results

The results showed that the parathyroid hormone synthesis, secretion, and action were significantly enriched after risperidone treatment. Downregulated TNIK could have an impact on the collagen-containing extracellular matrix, signaling receptor activator activity, and PI3K-Akt signaling pathway. Interestingly, bone mineralization function and calcium signaling pathway were enriched in the cross-talk genes. Additionally, FGFR2, FGF1, and FGFR might be the potential targets for TNIK affecting the effects of risperidone.

Conclusion

The study indicated that risperidone primarily influences functions and/or pathways associated with bone metabolism, potentially contributing to the adverse effect of osteoporosis. Our study may offer a novel perspective on investigating the mechanisms underlying the adverse effects of risperidone.

METTL3-mediated upregulation of FAM135B promotes EMT of esophageal squamous cell carcinoma via regulating the Wnt/β-catenin pathway

Family with sequence similarity 135 member B (FAM135B) is a novel driver gene in esophageal squamous cell carcinoma (ESCC). However, little is known regarding its biological functions and mechanisms in ESCC. Here, we identified that the high expression of FAM135B was associated with lymph node metastasis and infiltrating development of ESCC. Elevated FAM135B expression promoted ESCC migration and invasion in vitro and lung metastasis in vivo. Furthermore, epithelial-mesenchymal transition (EMT)-related pathways were enriched in ESCC samples with high levels of FAM135B and FAM135B positively regulated EMT markers. Mechanistically, we observed that FAM135B interacted with the intermediate domain of TRAF2 and NCK-interacting kinase (TNIK), activating the Wnt/β-catenin signaling pathway. The facilitation of TNIK on ESCC migration and invasion was reversed by FAM135B siRNA. In addition, the N6-methyladenosine (m6A) modification positively regulated FAM135B expression, with methyltransferase like 3 (METTL3) acting as its substantial m6A writer. The pro-EMT effects of METTL3 overexpression were reversed by silencing FAM135B. Collectively, these findings illustrate the critical role of ABCDE in ESCC progression and provide new insights into the upstream and downstream mechanisms of FAM135B.NEW & NOTEWORTHY This study reveals for the first time that the novel cancer-related gene, FAM135B, promotes ESCC metastasis both in vitro and in vivo. Besides, we substantiate FAM135B's action on the β-catenin pathway through interacting with TNIK, thereby elucidating the promotional effect of FAM135B on ESCC EMT. Furthermore, we provide initial evidence demonstrating that METTL3-mediated m6A modification upregulates the expression of FAM135B in ESCC cells.

Convergent and divergent transcriptional reprogramming of motor and sensory neurons underlying response to peripheral nerve injury

INTRODUCTION

Motor neurons differ from sensory neurons in aspects including origins and surrounding environment. Understanding the similarities and differences in molecular response to peripheral nerve injury (PNI) and regeneration between sensory and motor neurons is crucial for developing effective drug targets for CNS regeneration. However, genome-wide comparisons of molecular changes between sensory and motor neurons following PNI remains limited.

OBJECTIVES

This study aims to investigate genome-wide convergence and divergence of injury response between sensory and motor neurons to identify novel drug targets for neural repair.

METHODS

We analyzed two large-scale RNA-seq datasets of in situ captured sensory neurons (SNs) and motoneurons (MNs) upon PNI, retinal ganglion cells and spinal cord upon CNS injury. Additionally, we integrated these with other related single-cell level datasets. Bootstrap DESeq2 and WGCNA were used to detect and explore co-expression modules of differentially expressed genes (DEGs).

RESULTS

We found that SNs and MNs exhibited similar injury states, but with a delayed response in MNs. We identified a conserved regeneration-associated module (cRAM) with 274 shared DEGs. Of which, 47% of DEGs could be changed in injured neurons supported by single-cell resolution datasets. We also identified some less-studied candidates in cRAM, including genes associated with transcription, ubiquitination (Rnf122), and neuron-immune cells cross-talk. Further in vitro experiments confirmed a novel role of Rnf122 in axon growth. Analysis of the top 10% of DEGs with a large divergence suggested that both extrinsic (e.g., immune microenvironment) and intrinsic factors (e.g., development) contributed to expression divergence between SNs and MNs following injury.

CONCLUSIONS

This comprehensive analysis revealed convergent and divergent injury response genes in SNs and MNs, providing new insights into transcriptional reprogramming of sensory and motor neurons responding to axonal injury and subsequent regeneration. It also identified some novel regeneration-associated candidates that may facilitate the development of strategies for axon regeneration.

TNIK depletion induces inflammation and apoptosis in injured renal proximal tubule epithelial cells

In the aftermath of acute kidney injury (AKI), surviving proximal tubule epithelia repopulate injured tubules to promote repair. However, a portion of cells fail to repair [termed failed-repair proximal tubule cells (FR-PTCs)] and exert ongoing proinflammatory and profibrotic effects. To better understand the molecular drivers of the FR-PTC state, we reanalyzed a mouse ischemia-reperfusion injury single-nucleus RNA-sequencing (snRNA-seq) atlas to identify Traf2 and Nck interacting kinase (Tnik) to be exclusively expressed in FR-PTCs but not in healthy or acutely injured proximal tubules after AKI (2 and 6 wk) in mice. We confirmed expression of Tnik protein in injured mouse and human tissues by immunofluorescence. Then, to determine the functional role of Tnik in FR-PTCs, we depleted TNIK with siRNA in two human renal proximal tubule epithelial cell lines (primary and immortalized hRPTECs) and analyzed each by bulk RNA-sequencing. Pathway analysis revealed significant upregulation of inflammatory signaling pathways, whereas pathways associated with differentiated proximal tubules such as organic acid transport were significantly downregulated. TNIK gene knockdown drove reduced cell viability and increased apoptosis, including differentially expressed poly(ADP-ribose) polymerase (PARP) family members, cleaved PARP-1 fragments, and increased annexin V binding to phosphatidylserine. Together, these results indicate that Tnik upregulation in FR-PTCs acts in a compensatory fashion to suppress inflammation and promote proximal tubule epithelial cell survival after injury. Modulating TNIK activity may represent a prorepair therapeutic strategy after AKI.NEW & NOTEWORTHY The molecular drivers of successful and failed repair in the proximal tubule after acute kidney injury (AKI) are incompletely understood. We identified Traf2 and Nck interacting kinase (Tnik) to be exclusively expressed in failed-repair proximal tubule cells after AKI. We tested the effect of siTNIK depletion in two proximal tubule cell lines followed by bulk RNA-sequencing analysis. Our results indicate that TNIK acts to suppress inflammatory signaling and apoptosis in injured renal proximal tubule epithelial cells to promote cell survival.

Novel inhibitors of acute, axonal DLK palmitoylation are neuroprotective and avoid the deleterious side effects of cell-wide DLK inhibition

Dual leucine-zipper kinase (DLK) drives acute and chronic forms of neurodegeneration, suggesting that inhibiting DLK signaling could ameliorate diverse neuropathological conditions. However, direct inhibition of DLK's kinase domain in human patients and conditional knockout of DLK in mice both cause unintended side effects, including elevated plasma neurofilament levels, indicative of neuronal cytoskeletal disruption. Indeed, we found that a DLK kinase domain inhibitor acutely disrupted the axonal cytoskeleton and caused vesicle aggregation in cultured dorsal root ganglion (DRG) neurons, further cautioning against this therapeutic strategy. In seeking a more precise intervention, we found that retrograde (axon-to-soma) pro-degenerative signaling requires acute, axonal palmitoylation of DLK and hypothesized that modulating this post-translational modification might be more specifically neuroprotective than cell-wide DLK inhibition. To address this possibility, we screened >28,000 compounds using a high-content imaging assay that quantitatively evaluates DLK's palmitoylation-dependent subcellular localization. Of the 33 hits that significantly altered DLK localization in non-neuronal cells, several reduced DLK retrograde signaling and protected cultured DRG neurons from DLK-dependent neurodegeneration. Mechanistically, the two most neuroprotective compounds selectively prevent stimulus-dependent palmitoylation of axonal pools of DLK, a process crucial for DLK's recruitment to axonal vesicles. In contrast, these compounds minimally impact DLK localization and signaling in healthy neurons and avoid the cytoskeletal disruption associated with direct DLK inhibition. Importantly, our hit compounds also reduce pro-degenerative retrograde signaling in vivo, suggesting that modulating DLK's palmitoylation-dependent localization could be a novel neuroprotective strategy.

The response of Dual-leucine zipper kinase (DLK) to nocodazole: Evidence for a homeostatic cytoskeletal repair mechanism

Genetic and pharmacological perturbation of the cytoskeleton enhances the regenerative potential of neurons. This response requires Dual-leucine Zipper Kinase (DLK), a neuronal stress sensor that is a central regulator of axon regeneration and degeneration. The damage and repair aspects of this response are reminiscent of other cellular homeostatic systems, suggesting that a cytoskeletal homeostatic response exists. In this study, we propose a framework for understanding DLK mediated neuronal cytoskeletal homeostasis. We demonstrate that low dose nocodazole treatment activates DLK signaling. Activation of DLK signaling results in a DLK-dependent transcriptional signature, which we identify through RNA-seq. This signature includes genes likely to attenuate DLK signaling while simultaneously inducing actin regulating genes. We identify alterations to the cytoskeleton including actin-based morphological changes to the axon. These results are consistent with the model that cytoskeletal disruption in the neuron induces a DLK-dependent homeostatic mechanism, which we term the Cytoskeletal Stress Response (CSR) pathway.

Dichotomous role of the serine/threonine kinase MAP4K4 in pancreatic ductal adenocarcinoma onset and metastasis through control of AKT and ERK pathways

MAP4K4 is a serine/threonine kinase of the STE20 family involved in the regulation of actin cytoskeleton dynamics and cell motility. It has been proposed as a target of angiogenesis and inhibitors show potential in cardioprotection. MAP4K4 also mediates cell invasion in vitro, is overexpressed in various types of cancer, and is associated with poor patient prognosis. Recently, MAP4K4 has been shown to be overexpressed in pancreatic cancer, but its role in tumour initiation, progression, and metastasis is unknown. Here, using the KrasG12D Trp53R172H Pdx1-Cre (KPC) mouse model of pancreatic ductal adenocarcinoma (PDAC), we show that deletion of Map4k4 drives tumour initiation and progression. Moreover, we report that the acceleration of tumour onset is also associated with an overactivation of ERK and AKT, two major downstream effectors of KRAS, in vitro and in vivo. In contrast to the accelerated tumour onset caused by loss of MAP4K4, we observed a reduction in metastatic burden with both the KPC model and in an intraperitoneal transplant assay indicating a major role of MAP4K4 in metastatic seeding. In summary, our study sheds light on the dichotomous role of MAP4K4 in the initiation of PDAC onset, progression, and metastatic dissemination. It also identifies MAP4K4 as a possible druggable target against pancreatic cancer spread, but with the caveat that targeting MAP4K4 might accelerate early tumorigenesis. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Regulation of the Activity of the Dual Leucine Zipper Kinase by Distinct Mechanisms

The dual leucine zipper kinase (DLK) alias mitogen-activated protein 3 kinase 12 (MAP3K12) has gained much attention in recent years. DLK belongs to the mixed lineage kinases, characterized by homology to serine/threonine and tyrosine kinase, but exerts serine/threonine kinase activity. DLK has been implicated in many diseases, including several neurodegenerative diseases, glaucoma, and diabetes mellitus. As a MAP3K, it is generally assumed that DLK becomes phosphorylated and activated by upstream signals and phosphorylates and activates itself, the downstream serine/threonine MAP2K, and, ultimately, MAPK. In addition, other mechanisms such as protein-protein interactions, proteasomal degradation, dephosphorylation by various phosphatases, palmitoylation, and subcellular localization have been shown to be involved in the regulation of DLK activity or its fine-tuning. In the present review, the diverse mechanisms regulating DLK activity will be summarized to provide better insights into DLK action and, possibly, new targets to modulate DLK function.

Analyzing the ER stress response in ALS patient derived motor neurons identifies druggable neuroprotective targets

Amyotrophic lateral sclerosis (ALS) is a degenerative motor neuron (MN) disease with severely limited treatment options. Identification of effective treatments has been limited in part by the lack of predictive animal models for complex human disorders. Here, we utilized pharmacologic ER stressors to exacerbate underlying sensitivities conferred by ALS patient genetics in induced pluripotent stem cell (iPSC)-derived motor neurons (MNs). In doing so, we found that thapsigargin and tunicamycin exposure recapitulated ALS-associated degeneration, and that we could rescue this degeneration via MAP4K4 inhibition (MAP4K4i). We subsequently identified mechanisms underlying MAP4K4i-mediated protection by performing phosphoproteomics on iPSC-derived MNs treated with ER stressors ±MAP4K4i. Through these analyses, we found JNK, PKC, and BRAF to be differentially modulated in MAP4K4i-protected MNs, and that inhibitors to these proteins could also rescue MN toxicity. Collectively, this study highlights the value of utilizing ER stressors in ALS patient MNs to identify novel druggable targets.

Screens in aging-relevant human ALS-motor neurons identify MAP4Ks as therapeutic targets for the disease

Effective therapeutics is much needed for amyotrophic lateral sclerosis (ALS), an adult-onset neurodegenerative disease mainly affecting motor neurons. By screening chemical compounds in human patient-derived and aging-relevant motor neurons, we identify a neuroprotective compound and show that MAP4Ks may serve as therapeutic targets for treating ALS. The lead compound broadly improves survival and function of motor neurons directly converted from human ALS patients. Mechanistically, it works as an inhibitor of MAP4Ks, regulates the MAP4Ks-HDAC6-TUBA4A-RANGAP1 pathway, and normalizes subcellular distribution of RANGAP1 and TDP-43. Finally, in an ALS mouse model we show that inhibiting MAP4Ks preserves motor neurons and significantly extends animal lifespan.

Targeting synapse function and loss for treatment of neurodegenerative diseases

Synapse dysfunction and loss are hallmarks of neurodegenerative diseases that correlate with cognitive decline. However, the mechanisms and therapeutic strategies to prevent or reverse synaptic damage remain elusive. In this Review, we discuss recent advances in understanding the molecular and cellular pathways that impair synapses in neurodegenerative diseases, including the effects of protein aggregation and neuroinflammation. We also highlight emerging therapeutic approaches that aim to restore synaptic function and integrity, such as enhancing synaptic plasticity, preventing synaptotoxicity, modulating neuronal network activity and targeting immune signalling. We discuss the preclinical and clinical evidence for each strategy, as well as the challenges and opportunities for developing effective synapse-targeting therapeutics for neurodegenerative diseases.

Histone lactylation-derived LINC01127 promotes the self-renewal of glioblastoma stem cells via the cis-regulating the MAP4K4 to activate JNK pathway

Gliomas are the most prevalent and aggressive brain tumors, exhibiting high proliferation, abnormal glycolysis, and poor prognosis. LncRNAs act as regulatory molecules and play crucial roles in the malignant behaviors of GBM cells, including cell self-renewal. However, the regulatory mechanisms involved are largely unknown. In this study, we performed bioinformatics analysis to explore NF-κB pathway-related lncRNAs. ECAR and qRT-PCR were used to measure the relationship between glycolytic activity and lncRNA expression. Assays such as RIP-PCR and ChIP-PCR were employed to reveal the regulatory mechanisms of the lncRNA. Neurosphere formation and limiting dilution assays were performed to evaluate the self-renewal capacity of GBM cells. In our study, we identified an NF-κB pathway-related lncRNA named LINC01127 in GBM, which was found to be associated with poor progression of GBM. Functionally, the NF-κB pathway promoted warburg effect, which, in turn, induced the lactylation of H3 histone and increased the expression of LINC01127. Consequently, this enhancement of LINC01127 expression led to the promotion of self-renewal in GBM cells. Furthermore, LINC01127 regulated MAP4K4 expression in cis by directly guiding POLR2A to the MAP4K4 promoter regions, thereby leading to JNK pathway activation, and ultimately modulating the self-renewal of GBM cells. Moreover, the activated JNK pathway promoted the phosphorylation of IκBα. Overall, targeting LINC01127-mediated axis impeded orthotopic tumor growth in GBM xenografts. Taken together these results revealed that warburg effect-induced histone lactylation drives NF-κB-related LINC01127 expression, thereby promoting the self-renewal of GBM cells through the MAP4K4/JNK/NF-κB axis, and providing substantial evidence that LINC01127 might provide a novel therapeutic strategy for GBM patients.

Effects of MAP4K inhibition on neurite outgrowth

Protein kinases are responsible for protein phosphorylation and are involved in important intracellular signal transduction pathways in various cells, including neurons; however, a considerable number of poorly characterized kinases may be involved in neuronal development. Here, we considered mitogen-activated protein kinase kinase kinase kinases (MAP4Ks), related to as candidate regulators of neurite outgrowth and synaptogenesis, by examining the effects of a selective MAP4K inhibitor PF06260933. PF06260933 treatments of the cultured neurons reduced neurite lengths, not the number of synapses, and phosphorylation of GAP43 and JNK, relative to the control. These results suggest that MAP4Ks are physiologically involved in normal neuronal development and that the resultant impaired neurite outgrowth by diminished MAP4Ks' activity, is related to psychiatric disorders.

Genetic risk factors for severe and fatigue dominant long COVID and commonalities with ME/CFS identified by combinatorial analysis

BACKGROUND

Long COVID is a debilitating chronic condition that has affected over 100 million people globally. It is characterized by a diverse array of symptoms, including fatigue, cognitive dysfunction and respiratory problems. Studies have so far largely failed to identify genetic associations, the mechanisms behind the disease, or any common pathophysiology with other conditions such as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) that present with similar symptoms.

METHODS

We used a combinatorial analysis approach to identify combinations of genetic variants significantly associated with the development of long COVID and to examine the biological mechanisms underpinning its various symptoms. We compared two subpopulations of long COVID patients from Sano Genetics' Long COVID GOLD study cohort, focusing on patients with severe or fatigue dominant phenotypes. We evaluated the genetic signatures previously identified in an ME/CFS population against this long COVID population to understand similarities with other fatigue disorders that may be triggered by a prior viral infection. Finally, we also compared the output of this long COVID analysis against known genetic associations in other chronic diseases, including a range of metabolic and neurological disorders, to understand the overlap of pathophysiological mechanisms.

RESULTS

Combinatorial analysis identified 73 genes that were highly associated with at least one of the long COVID populations included in this analysis. Of these, 9 genes have prior associations with acute COVID-19, and 14 were differentially expressed in a transcriptomic analysis of long COVID patients. A pathway enrichment analysis revealed that the biological pathways most significantly associated with the 73 long COVID genes were mainly aligned with neurological and cardiometabolic diseases. Expanded genotype analysis suggests that specific SNX9 genotypes are a significant contributor to the risk of or protection against severe long COVID infection, but that the gene-disease relationship is context dependent and mediated by interactions with KLF15 and RYR3. Comparison of the genes uniquely associated with the Severe and Fatigue Dominant long COVID patients revealed significant differences between the pathways enriched in each subgroup. The genes unique to Severe long COVID patients were associated with immune pathways such as myeloid differentiation and macrophage foam cells. Genes unique to the Fatigue Dominant subgroup were enriched in metabolic pathways such as MAPK/JNK signaling. We also identified overlap in the genes associated with Fatigue Dominant long COVID and ME/CFS, including several involved in circadian rhythm regulation and insulin regulation. Overall, 39 SNPs associated in this study with long COVID can be linked to 9 genes identified in a recent combinatorial analysis of ME/CFS patient from UK Biobank. Among the 73 genes associated with long COVID, 42 are potentially tractable for novel drug discovery approaches, with 13 of these already targeted by drugs in clinical development pipelines. From this analysis for example, we identified TLR4 antagonists as repurposing candidates with potential to protect against long term cognitive impairment pathology caused by SARS-CoV-2. We are currently evaluating the repurposing potential of these drug targets for use in treating long COVID and/or ME/CFS.

CONCLUSION

This study demonstrates the power of combinatorial analytics for stratifying heterogeneous populations in complex diseases that do not have simple monogenic etiologies. These results build upon the genetic findings from combinatorial analyses of severe acute COVID-19 patients and an ME/CFS population and we expect that access to additional independent, larger patient datasets will further improve the disease insights and validate potential treatment options in long COVID.

Realgar-Induced Neurotoxicity: Crosstalk Between the Autophagic Flux and the p62-NRF2 Feedback Loop Mediates p62 Accumulation to Promote Apoptosis

Realgar is a traditional Chinese medicine that contains arsenic. It has been reported that the abuse of medicine-containing realgar has potential central nervous system (CNS) toxicity, but the toxicity mechanism has not been elucidated. In this study, we established an in vivo realgar exposure model and selected the end product of realgar metabolism, DMA, to treat SH-SY5Y cells in vitro. Many assays, including behavioral, analytical chemistry, and molecular biology, were used to elucidate the roles of the autophagic flux and the p62-NRF2 feedback loop in realgar-induced neurotoxicity. The results showed that arsenic could accumulate in the brain, causing cognitive impairment and anxiety-like behavior. Realgar impairs the ultrastructure of neurons, promotes apoptosis, perturbs autophagic flux homeostasis, amplifies the p62-NRF2 feedback loop, and leads to p62 accumulation. Further analysis showed that realgar promotes the formation of the Beclin1-Vps34 complex by activating JNK/c-Jun to induce autophagy and recruit p62. Meanwhile, realgar inhibits the activities of CTSB and CTSD and changes the acidity of lysosomes, leading to the inhibition of p62 degradation and p62 accumulation. Moreover, the amplified p62-NRF2 feedback loop is involved in the accumulation of p62. Its accumulation promotes neuronal apoptosis by upregulating the expression levels of Bax and cleaved caspase-9, resulting in neurotoxicity. Taken together, these data suggest that realgar can perturb the crosstalk between the autophagic flux and the p62-NRF2 feedback loop to mediate p62 accumulation, promote apoptosis, and induce neurotoxicity. Realgar promotes p62 accumulation to produce neurotoxicity by perturbing the autophagic flux and p62-NRF2 feedback loop crosstalk.

Off-target pharmacological activity at various kinases: Potential functional and pathological side effects

In drug discovery, during the lead optimization and candidate characterization stages, novel small molecules are frequently evaluated in a battery of in vitro pharmacology assays to identify potential unintended, off-target interactions with various receptors, transporters, ion channels, and enzymes, including kinases. Furthermore, these screening panels may also provide utility at later stages of development to provide a mechanistic understanding of unexpected safety findings. Here, we present a compendium of the most likely functional and pathological outcomes associated with interaction(s) to a panel of 95 kinases based on an extensive curation of the scientific literature. This panel of kinases was designed by AbbVie based on safety-related data extracted from the literature, as well as from over 20 years of institutional knowledge generated from discovery efforts. For each kinase, the scientific literature was reviewed using online databases and the most often reported functional and pathological effects were summarized. This work should serve as a practical guide for small molecule drug discovery scientists and clinical investigators to predict and/or interpret adverse effects related to pharmacological interactions with these kinases.

A nerve-wracking buzz: lessons from Drosophila models of peripheral neuropathy and axon degeneration

The degeneration of axons and their terminals occurs following traumatic, toxic, or genetically-induced insults. Common molecular mechanisms unite these disparate triggers to execute a conserved nerve degeneration cascade. In this review, we will discuss how models of peripheral nerve injury and neuropathy in Drosophila have led the way in advancing molecular understanding of axon degeneration and nerve injury pathways. Both neuron-intrinsic as well as glial responses to injury will be highlighted. Finally, we will offer perspective on what additional questions should be answered to advance these discoveries toward clinical interventions for patients with neuropathy.

MAP4K4 is involved in the neuronal development of retinal photoreceptors

Mitogen-activated protein kinase kinase kinase kinase-4 (MAP4K4) is a potential regulator of photoreceptor development. To investigate the mechanisms underlying MAP4K4 during the neuronal development of retinal photoreceptors, we generated knockout models of C57BL/6j mice in vivo and 661 W cells in vitro. Our findings revealed homozygous lethality and neural tube malformation in mice subjected to Map4k4 DNA ablation, providing evidence for the involvement of MAP4K4 in early stage embryonic neural formation. Furthermore, our study demonstrated that the ablation of Map4k4 DNA led to the vulnerability of photoreceptor neurites during induced neuronal development. By monitoring transcriptional and protein variations in mitogen-activated protein kinase (MAPK) signaling pathway-related factors, we discovered an imbalance in neurogenesis-related factors in Map4k4 -/- cells. Specifically, MAP4K4 promotes jun proto-oncogene (c-JUN) phosphorylation and recruits other factors related to nerve growth, ultimately leading to the robust formation of photoreceptor neurites. These data suggest that MAP4K4 plays a decisive role in regulating the fate of retinal photoreceptors through molecular modulation and contributes to our understanding of vision formation.

Chemical screens in aging-relevant human motor neurons identify MAP4Ks as therapeutic targets for amyotrophic lateral sclerosis

Effective therapeutics is much needed for amyotrophic lateral sclerosis (ALS), an adult-onset neurodegenerative disease mainly affecting motor neurons. By screening chemical compounds in human patient-derived and aging-relevant motor neurons, we identify a neuroprotective compound and show that MAP4Ks may serve as therapeutic targets for treating ALS. The lead compound broadly improves survival and function of motor neurons directly converted from human ALS patients. Mechanistically, it works as an inhibitor of MAP4Ks, regulates the MAP4Ks-HDAC6-TUBA4A-RANGAP1 pathway, and normalizes subcellular distribution of RANGAP1 and TDP-43. Finally, in an ALS mouse model we show that inhibiting MAP4Ks preserves motor neurons and significantly extends animal lifespan.

MAP4Ks inhibition promotes retinal neuron regeneration from Müller glia in adult mice

Mammalian Müller glia (MG) possess limited regenerative capacities. However, the intrinsic capacity of mammalian MG to transdifferentiate to generate mature neurons without transgenic manipulations remains speculative. Here we show that MAP4K4, MAP4K6 and MAP4K7, which are conserved Misshapen subfamily of ste20 kinases homologs, repress YAP activity in mammalian MG and therefore restrict their ability to be reprogrammed. However, by treating with a small molecule inhibitor of MAP4K4/6/7, mouse MG regain their ability to proliferate and enter into a retinal progenitor cell (RPC)-like state after NMDA-induced retinal damage; such plasticity was lost in YAP knockout MG. Moreover, spontaneous trans-differentiation of MG into retinal neurons expressing both amacrine and retinal ganglion cell (RGC) markers occurs after inhibitor withdrawal. Taken together, these findings suggest that MAP4Ks block the reprogramming capacity of MG in a YAP-dependent manner in adult mammals, which provides a novel avenue for the pharmaceutical induction of retinal regeneration in vivo.

Deciphering the multifunctional role of dual leucine zipper kinase (DLK) and its therapeutic potential in disease

Dual leucine zipper kinase (DLK, MAP3K12), a serine/threonine protein kinase, plays a key role in neuronal development, as it regulates axon regeneration and degeneration through its downstream kinase. Importantly, DLK is closely related to the pathogenesis of numerous neurodegenerative diseases and the induction of β-cell apoptosis that leads to diabetes. In this review, we summarize the current understanding of DLK function, and then discuss the role of DLK signaling in human diseases. Furthermore, various types of small molecule inhibitors of DLK that have been published so far are described in detail in this paper, providing some strategies for the design of DLK small molecule inhibitors in the future.

Molecular Insights of MAP4K4 Signaling in Inflammatory and Malignant Diseases

Mitogen-activated protein kinase (MAPK) cascades are crucial in extracellular signal transduction to cellular responses. The classical three-tiered MAPK cascades include signaling through MAP kinase kinase kinase (MAP3K) that activates a MAP kinase kinase (MAP2K), which in turn induces MAPK activation and downstream cellular responses. The upstream activators of MAP3K are often small guanosine-5'-triphosphate (GTP)-binding proteins, but in some pathways, MAP3K can be activated by another kinase, which is known as a MAP kinase kinase kinase kinase (MAP4K). MAP4K4 is one of the widely studied MAP4K members, known to play a significant role in inflammatory, cardiovascular, and malignant diseases. The MAP4K4 signal transduction plays an essential role in cell proliferation, transformation, invasiveness, adhesiveness, inflammation, stress responses, and cell migration. Overexpression of MAP4K4 is frequently reported in many cancers, including glioblastoma, colon, prostate, and pancreatic cancers. Besides its mainstay pro-survival role in various malignancies, MAP4K4 has been implicated in cancer-associated cachexia. In the present review, we discuss the functional role of MAP4K4 in malignant/non-malignant diseases and cancer-associated cachexia and its possible use in targeted therapy.

MAP4K4 promotes ovarian cancer metastasis through diminishing ADAM10-dependent N-cadherin cleavage

Peritoneal metastasis is a key feature of advanced ovarian cancer, but the critical protein required for ovarian cancer metastasis and progression is yet to be defined. Thus, an unbiased high throughput and in-depth study is warranted to unmask the mechanism. Transcriptomic sequencing of paired primary ovarian tumors and metastases unveiled that MAP4K4, a serine/threonine kinase belongs to the Ste20 family of kinases, was highly expressed in metastatic sites. Increased MAP4K4 expression in metastasis was further validated in other independent patients, with higher MAP4K4 expression associated with poorer survival, higher level of CA125 and more advanced FIGO stage. Down regulation of MAP4K4 inhibited cancer cell adhesion, migration, and invasion. Notably, MAP4K4 was found to stabilize N-cadherin. Further results showed that MAP4K4 mediated phosphorylation of ADAM10 at Ser436 results in suppression of N-cadherin cleavage by ADAM10, leading to N-cadherin stabilization. Pharmacologic inhibition of MAP4K4 abrogated peritoneal metastases. Overall, our data reveal MAP4K4 as a significant promoter in ovarian cancer metastasis. Targeting MAP4K4 may be a potential therapeutic approach for ovarian cancer patients.

Alzheimer's Disease: An Updated Overview of Its Genetics

Alzheimer's disease (AD) is the most common neurodegenerative disease in the world. It is classified as familial and sporadic. The dominant familial or autosomal presentation represents 1-5% of the total number of cases. It is categorized as early onset (EOAD; <65 years of age) and presents genetic mutations in presenilin 1 (PSEN1), presenilin 2 (PSEN2), or the Amyloid precursor protein (APP). Sporadic AD represents 95% of the cases and is categorized as late-onset (LOAD), occurring in patients older than 65 years of age. Several risk factors have been identified in sporadic AD; aging is the main one. Nonetheless, multiple genes have been associated with the different neuropathological events involved in LOAD, such as the pathological processing of Amyloid beta (Aβ) peptide and Tau protein, as well as synaptic and mitochondrial dysfunctions, neurovascular alterations, oxidative stress, and neuroinflammation, among others. Interestingly, using genome-wide association study (GWAS) technology, many polymorphisms associated with LOAD have been identified. This review aims to analyze the new genetic findings that are closely related to the pathophysiology of AD. Likewise, it analyzes the multiple mutations identified to date through GWAS that are associated with a high or low risk of developing this neurodegeneration. Understanding genetic variability will allow for the identification of early biomarkers and opportune therapeutic targets for AD.

Discovery of Potent and Selective Dual Leucine Zipper Kinase/Leucine Zipper-Bearing Kinase Inhibitors with Neuroprotective Properties in In Vitro and In Vivo Models of Amyotrophic Lateral Sclerosis

Dual leucine zipper kinase (DLK) and leucine zipper-bearing kinase (LZK) are regulators of neuronal degeneration and axon growth. Therefore, there is a considerable interest in developing DLK/LZK inhibitors for neurodegenerative diseases. Herein, we use ligand- and structure-based drug design approaches for identifying novel amino-pyrazine inhibitors of DLK/LZK. DN-1289 (14), a potent and selective dual DLK/LZK inhibitor, demonstrated excellent in vivo plasma half-life across species and is anticipated to freely penetrate the central nervous system with no brain impairment based on in vivo rodent pharmacokinetic studies and human in vitro transporter data. Proximal target engagement and disease relevant pathway biomarkers were also favorably regulated in an in vivo model of amyotrophic lateral sclerosis.

The molecular basis of the dichotomous functionality of MAP4K4 in proliferation and cell motility control in cancer

The finely tuned integration of intra- and extracellular cues by components of the mitogen-activated protein kinase (MAPK) signaling pathways controls the mutually exclusive phenotypic manifestations of uncontrolled growth and tumor cell dissemination. The Ser/Thr kinase MAP4K4 is an upstream integrator of extracellular cues involved in both proliferation and cell motility control. Initially identified as an activator of the c-Jun N-terminal kinase (JNK), the discovery of diverse functions and additional effectors of MAP4K4 beyond JNK signaling has considerably broadened our understanding of this complex kinase. The implication of MAP4K4 in the regulation of cytoskeleton dynamics and cell motility provided essential insights into its role as a pro-metastatic kinase in cancer. However, the more recently revealed role of MAP4K4 as an activator of the Hippo tumor suppressor pathway has complicated the understanding of MAP4K4 as an oncogenic driver kinase. To develop a better understanding of the diverse functions of MAP4K4 and their potential significance in oncogenesis and tumor progression, we have collected and assessed the current evidence of MAP4K4 implication in molecular mechanisms that control proliferation and promote cell motility. A better understanding of these mechanisms is particularly relevant in the brain, where MAP4K4 is highly expressed and under pathological conditions either drives neuronal cell death in neurodegenerative diseases or cell dissemination in malignant tumors. We review established effectors and present novel interactors of MAP4K4, which offer mechanistic insights into MAP4K4 function and may inspire novel intervention strategies. We discuss possible implications of novel interactors in tumor growth and dissemination and evaluate potential therapeutic strategies to selectively repress pro-oncogenic functions of MAP4K4.

An induced pluripotent stem cell-based model identifies molecular targets of vincristine neurotoxicity

To model peripheral nerve degeneration and investigate molecular mechanisms of neurodegeneration, we established a cell system of induced pluripotent stem cell (iPSC)-derived sensory neurons exposed to vincristine, a drug that frequently causes chemotherapy-induced peripheral neuropathy. Sensory neurons differentiated from iPSCs exhibit distinct neurochemical patterns according to the immunocytochemical phenotypes, and gene expression of peripherin (PRPH, hereafter referred to as Peri) and neurofilament heavy chain (NEFH, hereafter referred to as NF). The majority of iPSC-derived sensory neurons were PRPH positive/NEFH negative, i.e. Peri(+)/NF(-) neurons, whose somata were smaller than those of Peri(+)/NF(+) neurons. On exposure to vincristine, projections from the cell body of a neuron, i.e. neurites, were degenerated quicker than somata, the lethal concentration to kill 50% (LC50) of neurites being below the LC50 for somata, consistent with the clinical pattern of length-dependent neuropathy. We then examined the molecular expression in the MAP kinase signaling pathways of, extracellular signal-regulated kinases 1/2 (MAPK1/3, hereafter referred to as ERK), p38 mitogen-activated protein kinases (MAPK11/12/13/14, hereafter referred to as p38) and c-Jun N-terminal kinases (MAPK8/9/10, hereafter referred to as JNK). Regarding these three cascades, only phosphorylation of JNK was upregulated but not that of p38 or ERK1/2. Furthermore, vincristine-treatment resulted in impaired autophagy and reduced autophagic flux. Rapamycin-treatment reversed the effect of impaired autophagy and JNK activation. These results not only established a platform to study peripheral degeneration of human neurons but also provide molecular mechanisms for neurodegeneration with the potential for therapeutic targets.

Multi-Omic Investigations of a 17-19 Translocation Links MINK1 Disruption to Autism, Epilepsy and Osteoporosis

Balanced structural variants, such as reciprocal translocations, are sometimes hard to detect with sequencing, especially when the breakpoints are located in repetitive or insufficiently mapped regions of the genome. In such cases, long-range information is required to resolve the rearrangement, identify disrupted genes and, in symptomatic carriers, pinpoint the disease-causing mechanisms. Here, we report an individual with autism, epilepsy and osteoporosis and a de novo balanced reciprocal translocation: t(17;19) (p13;p11). The genomic DNA was analyzed by short-, linked- and long-read genome sequencing, as well as optical mapping. Transcriptional consequences were assessed by transcriptome sequencing of patient-specific neuroepithelial stem cells derived from induced pluripotent stem cells (iPSC). The translocation breakpoints were only detected by long-read sequencing, the first on 17p13, located between exon 1 and exon 2 of MINK1 (Misshapen-like kinase 1), and the second in the chromosome 19 centromere. Functional validation in induced neural cells showed that MINK1 expression was reduced by >50% in the patient’s cells compared to healthy control cells. Furthermore, pathway analysis revealed an enrichment of changed neural pathways in the patient’s cells. Altogether, our multi-omics experiments highlight MINK1 as a candidate monogenic disease gene and show the advantages of long-read genome sequencing in capturing centromeric translocations.

Regulation of Key Immune-Related Genes in the Heart Following Burn Injury

Immune cascade is one of major factors leading to cardiac dysfunction after burn injury. TLRs are a class of pattern-recognition receptors (PRRs) that initiate the innate immune response by sensing conserved molecular patterns for early immune recognition of a pathogen. The Rat Toll-Like Receptor (TLR) Signaling Pathway RT² Profiler PCR Array profiles the expression of 84 genes central to TLR-mediated signal transduction and innate immunity, and is a validated tool for identifying differentially expressed genes (DEGs). We employed the PCR array to identify burn-induced cardiac TLR-signaling-related DEGs. A total of 38 up-regulated DEGs and 19 down-regulated DEGs were identified. Network analysis determined that all DEGS had 10 clusters, while up-regulated DEGs had 6 clusters and down-regulated DEGs had 5 clusters. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that DEGs were involved in TLR signaling, the RIG-I-Like receptor signaling pathway, the IL-17 signaling pathway, and the NFkB signaling pathway. Function analysis indicated that DEGs were associated with Toll-like receptor 2 binding, Lipopeptide binding, Toll-like receptor binding, and NAD(P)+ nucleosidase activity. The validation of 18 up-regulated DEGs (≥10-fold change) and 6 down-regulated DEGs (≤5-fold change) demonstrated that the PCR array is a trusted method for identifying DEGs. The analysis of validated DEG-derived protein–protein interaction networks will guide our future investigations. In summary, this study not only identified the TLR-signaling-pathway-related DEGs after burn injury, but also confirmed that the burn-induced cardiac cytokine cascade plays an important role in burn-induced heart dysfunction. The results will provide the novel therapeutic targets to protect the heart after burn injury.

Inhibition of MAP4K4 Signaling Initiaties Metabolic Reprogramming to Protect Hepatocytes from Lipotoxic Damage

The primary hepatic consequence of obesity is non-alcoholic fatty liver disease (NAFLD), affecting about 25% of the global adult population. Non-alcoholic steatohepatitis (NASH) is a severe form of NAFLD characterized by liver lipid accumulation, inflammation, and hepatocyte ballooning, with a different degree of hepatic fibrosis. In the light of rapidly increasing prevalence of NAFLD and NASH, there is an urgent need for improved understanding of the molecular pathogenesis of these diseases. The aim of this study was to decipher the possible role of STE20-type kinase MAP4K4 in the regulation of hepatocellular lipotoxicity and susceptibility to NAFLD. We found that MAP4K4 mRNA expression in human liver biopsies was positively correlated with key hallmarks of NAFLD (i.e., liver steatosis, lobular inflammation, hepatocellular ballooning, and fibrosis). We also found that the silencing of MAP4K4 suppressed lipid deposition in human hepatocytes by stimulating β-oxidation and triacylglycerol secretion, while attenuating fatty acid influx and lipid synthesis. Furthermore, downregulation of MAP4K4 markedly reduced the glycolysis rate and lowered incidences of oxidative/endoplasmic reticulum stress. In parallel, we observed suppressed JNK and ERK and increased AKT phosphorylation in MAP4K4-deficient hepatocytes. Together, these results provide the first experimental evidence supporting the potential involvement of STE20-type kinase MAP4K4 as a component of the hepatocellular lipotoxic milieu promoting NAFLD susceptibility.

Insights into nervous system repair from the fruit fly

Millions of people experience injury to the central nervous system (CNS) each year, many of whom are left permanently disabled, providing a challenging hurdle for the field of regenerative medicine. Repair of damage in the CNS occurs through a concerted effort of phagocytosis of debris, cell proliferation and differentiation to produce new neurons and glia, distal axon/dendrite degeneration, proximal axon/dendrite regeneration and axon re-enwrapment. In humans, regeneration is observed within the peripheral nervous system, while in the CNS injured axons exhibit limited ability to regenerate. This has also been described for the fruit fly Drosophila. Powerful genetic tools available in Drosophila have allowed the response to CNS insults to be probed and novel regulators with mammalian orthologs identified. The conservation of many regenerative pathways, despite considerable evolutionary separation, stresses that these signals are principal regulators and may serve as potential therapeutic targets. Here, we highlight the role of Drosophila CNS injury models in providing key insight into regenerative processes by exploring the underlying pathways that control glial and neuronal activation in response to insult, and their contribution to damage repair in the CNS.

Palmitoylation couples the kinases DLK and JNK3 to facilitate prodegenerative axon-to-soma signaling

Dual leucine-zipper kinase (DLK; a MAP3K) mediates neuronal responses to diverse injuries and insults through the c-Jun N-terminal kinase (JNK) family of mitogen-activated protein kinases (MAPKs). Here, we identified two ways through which DLK is coupled to the neural-specific isoform JNK3 to control prodegenerative signaling. JNK3 catalyzed positive feedback phosphorylation of DLK that further activated DLK and locked the DLK-JNK3 module in a highly active state. Neither homologous MAP3Ks nor a homologous MAPK could support this positive feedback loop. Unlike the related JNK1 isoform JNK2 and JNK3 promote prodegenerative axon-to-soma signaling and were endogenously palmitoylated. Moreover, palmitoylation targeted both DLK and JNK3 to the same axonal vesicles, and JNK3 palmitoylation was essential for axonal retrograde signaling in response to optic nerve crush injury in vivo. These findings provide previously unappreciated insights into DLK-JNK signaling relevant to neuropathological conditions and answer long-standing questions regarding the selective prodegenerative roles of JNK2 and JNK3.

LncRNA ZEB1-AS1/miR-1224-5p / MAP4K4 axis regulates mitochondria-mediated HeLa cell apoptosis in persistent Chlamydia trachomatis infection

Persistent infection of Chlamydia trachomatis is thought to be responsible for the debilitating sequelae of blinding trachoma and infertility. Inhibition of host cell apoptosis is a persistent C. trachomatis infection mechanism. ZEB1-AS1 is a long non-coding RNA (lncRNA), which was up-regulated in persistent C. trachomatis infection in our previous work. In this study, we investigated the role of ZEB1-AS1 in persistent infection and the potential mechanisms. The results showed that ZEB1-AS1 was involved in the regulation of apoptosis, and targeted silencing of ZEB1-AS1 could increase the apoptosis rate of persistently infected cells. Mechanically, interference ZEB1-AS1 caused an apparent down-regulation of the Bcl-2/Bax ratio and the repression of the mitochondrial membrane potential with the remarkable release of cytochrome c, resulting in the significant elevation level of caspase-3 activation. Meanwhile, the luciferase reporter assay confirmed that ZEB1-AS1 acted as a sponge for miR-1224-5p to target MAP4K4. The regulatory effect of miR-1224-5p/MAP4K4 on persistent infection-induced antiapoptosis was regulated by ZEB1-AS1. In addition, ZEB1-AS1 inhibited the apoptosis of Chlamydia-infected cells by activating the MAPK/ERK pathway. In conclusion, we found a new molecular mechanism that the ZEB1-AS1/miR-1224-5p/MAP4K4 axis contributes to apoptosis resistance in persistent C. trachomatis infection. This work may help understand the pathogenic mechanisms of persistent C. trachomatis infection and reveal a potential therapeutic strategy for its treatment.

Traf2 and NCK Interacting Kinase Is a Critical Regulator of Procollagen I Trafficking and Hepatic Fibrogenesis in Mice

Hepatic fibrosis is driven by deposition of matrix proteins following liver injury. Hepatic stellate cells (HSCs) drive fibrogenesis, producing matrix proteins, including procollagen I, which matures into collagen I following secretion. Disrupting intracellular procollagen processing and trafficking causes endoplasmic reticulum stress and stress-induced HSC apoptosis and thus is an attractive antifibrotic strategy. We designed an immunofluorescence-based small interfering RNA (siRNA) screen to identify procollagen I trafficking regulators, hypothesizing that these proteins could serve as antifibrotic targets. A targeted siRNA screen was performed using immunofluorescence to detect changes in intracellular procollagen I. Tumor necrosis factor receptor associated factor 2 and noncatalytic region of tyrosine kinase-interacting kinase (TNIK) was identified and interrogated in vitro and in vivo using the TNIK kinase inhibitor NCB-0846 or RNA interference-mediated knockdown. Our siRNA screen identified nine genes whose knockdown promoted procollagen I retention, including the serine/threonine kinase TNIK. Genetic deletion or pharmacologic inhibition of TNIK through the small molecule inhibitor NCB-0846 disrupted procollagen I trafficking and secretion without impacting procollagen I expression. To investigate the role of TNIK in liver fibrogenesis, we analyzed human and murine livers, finding elevated TNIK expression in human cirrhotic livers and increased TNIK expression and kinase activity in both fibrotic mouse livers and activated primary human HSCs. Finally, we tested whether inhibition of TNIK kinase activity could limit fibrogenesis in vivo. Mice receiving NCB-0846 displayed reduced CCl₄ -induced fibrogenesis compared to CCl₄ alone, although α-smooth muscle actin levels were unaltered. Conclusions: Our siRNA screen effectively identified TNIK as a key kinase involved in procollagen I trafficking in vitro and hepatic fibrogenesis in vivo.

Priming of NLRP3 inflammasome activation by Msn kinase MINK1 in macrophages

The nucleotide-binding domain, leucine-rich-repeat containing family, pyrin domain-containing 3 (NLRP3) inflammasome is essential in inflammation and inflammatory disorders. Phosphorylation at various sites on NLRP3 differentially regulates inflammasome activation. The Ser725 phosphorylation site on NLRP3 is depicted in multiple inflammasome activation scenarios, but the importance and regulation of this site has not been clarified. The present study revealed that the phosphorylation of Ser725 was an essential step for the priming of the NLRP3 inflammasome in macrophages. We also showed that Ser725 was directly phosphorylated by misshapen (Msn)/NIK-related kinase 1 (MINK1), depending on the direct interaction between MINK1 and the NLRP3 LRR domain. MINK1 deficiency reduced NLRP3 activation and suppressed inflammatory responses in mouse models of acute sepsis and peritonitis. Reactive oxygen species (ROS) upregulated the kinase activity of MINK1 and subsequently promoted inflammasome priming via NLRP3 Ser725 phosphorylation. Eliminating ROS suppressed NLRP3 activation and reduced sepsis and peritonitis symptoms in a MINK1-dependent manner. Altogether, our study reveals a direct regulation of the NLRP3 inflammasome by Msn family kinase MINK1 and suggests that modulation of MINK1 activity is a potential intervention strategy for inflammasome-related diseases.

MAP4K4 promotes pancreatic tumorigenesis via phosphorylation and activation of mixed lineage kinase 3

MAP4K4 is a Ste20 member and reported to play important roles in various pathologies, including in cancer. However, the mechanism by which MAP4K4 promotes pancreatic cancer is not fully understood. It is suggested that MAP4K4 might function as a cancer promoter via specific downstream target(s) in an organ-specific manner. Here we identified MLK3 as a direct downstream target of MAP4K4. The MAP4K4 and MLK3 associates with each other, and MAP4K4 phosphorylates MLK3 on Thr738 and increases MLK3 kinase activity and downstream signaling. The phosphorylation of MLK3 by MAP4K4 promotes pancreatic cancer cell proliferation, migration, and colony formation. Moreover, MAP4K4 is overexpressed in human pancreatic tumors and directly correlates with the disease progression. The MAP4K4-specific pharmacological inhibitor, GNE-495, impedes pancreatic cancer cell growth, migration, induces cell death, and arrests cell cycle progression. Additionally, the GNE-495 reduced the tumor burden and extended survival of the KPC mice with pancreatic cancer. The MAP4K4 inhibitor also reduced MAP4K4 protein expression, tumor stroma, and induced cell death in murine pancreatic tumors. These findings collectively suggest that MLK3 phosphorylation by MAP4K4 promotes pancreatic cancer, and therefore therapies targeting MAP4K4 might alleviate the pancreatic cancer tumor burden in patients.