A novel human STE20-related protein kinase, HGK, that specifically activates the c-Jun N-terminal kinase signaling pathway

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.

Identification of potential inhibitors for MAP4K4 in glaucoma using meta-dynamics-based dissociation free energy calculation

Glaucoma, a prevalent eye ailment causing irreversible vision loss, affects over 295 million individuals globally, necessitating the exploration of novel therapeutic avenues. Despite extensive research on targets like the phosphodiesterase enzyme and rho kinase, the potential of MAP4K4 in glaucoma remains untapped. This study aims to identify potent MAP4K4 inhibitors to counteract retinal cell apoptosis and oxidative stress associated with glaucoma. Using HTVS and XP docking, 911,059 compounds were screened. The MMGBSA calculation and pharmacokinetics analysis were used to shortlist the compounds. After performing 75 molecular dynamics simulations, further meta-dynamics were employed to calculate dissociation-free energy and find potential MAP4K4 inhibitors. Findings indicated that ZINC06717217 and ZINC38836256 exhibited remarkable promise, with docking scores of -9.57 and -11.12 and MMGBSA binding energies of -91.07 kcal/mol and -87.52 kcal/mol, respectively. Comparative analysis with the reference compound Q27453723 underscored their superior stability, requiring dissociation-free energies of -15.11 kcal/mol and -12.46 kcal/mol to disengage from the docked complex. This underscored their robust binding affinity. ZINC06717217 and ZINC38836256 show promising stability and strong binding to the MAP4K4 protein. Hence, these findings are promising in inhibiting MAP4K4 for glaucoma treatment, potentially leading to more effective treatment and curing blindness. KEY MESSAGES: First to incorporate the dissociation-free energy for identifying compounds for glaucoma treatment. In-silico analysis showed that ZINC06717217 and ZINC38836256 are promising compounds for targeting MAP4K4.

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.

The Dual-specificity Phosphatase 3 (DUSP3): A Potential Target Against Renal Ischemia/Reperfusion Injury

Renal ischemia/reperfusion (I/R) injury is a common clinical challenge faced by clinicians in kidney transplantation. I/R is the leading cause of acute kidney injury, and it occurs when blood flow to the kidney is interrupted and subsequently restored. I/R impairs renal function in both short and long terms. Renal ischemic preconditioning refers to all maneuvers intended to prevent or attenuate ischemic damage. In this context, the present review focuses on the dual-specificity phosphatase 3 (DUSP3), also known as vaccinia H1-related phosphatase, an uncommon regulator of mitogen-activated protein kinase (MAPK) phosphorylation. DUSP3 has different biological functions: (1) it acts as a tumor modulator and (2) it is involved in the regulation of immune response, thrombosis, hemostasis, angiogenesis, and genomic stability. These functions occur either through MAPK-dependent or MAPK-independent mechanisms. DUSP3 genetic deletion dampens kidney damage and inflammation caused by I/R in mice, suggesting DUSP3 as a potential target for preventing renal I/R injury. Here, we discuss the putative role of DUSP3 in ischemic preconditioning and the potential mechanisms of such an attenuated inflammatory response via improved kidney perfusion and adequate innate immune response.

Role of Mitogen-Activated Protein Kinase Kinase Kinase Kinase 4 Signaling in Liver and Metabolic Diseases

MAP4K4 is a serine/threonine protein kinase belonging to the germinal center kinase subgroup of sterile 20 protein family of kinases. MAP4K4 has been involved in regulating multiple biologic processes and a plethora of pathologies, including systemic inflammation, cardiovascular diseases, cancers, and metabolic and hepatic diseases. Recently, multiple reports have indicated the upregulation of MAP4K4 expression and signaling in hyperglycemia and liver diseases. This review provides an overview of our current knowledge of MAP4K4 structure and expression, as well as its regulation and signaling, specifically in metabolic and hepatic diseases. Reviewing these promising studies will enrich our understanding of MAP4K4 signaling pathways and, in the future, will help us design innovative therapeutic interventions against metabolic and liver diseases using MAP4K4 as a target. SIGNIFICANCE STATEMENT: Although most studies on the involvement of MAP4K4 in human pathologies are related to cancers, only recently its role in liver and other metabolic diseases is beginning to unravel. This mini review discusses recent advancements in MAP4K4 biology within the context of metabolic dysfunction and comprehensively characterizes MAP4K4 as a clinically relevant therapeutic target against liver and metabolic diseases.

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.

In silico identification and biological evaluation of a selective MAP4K4 inhibitor against pancreatic cancer

Inhibiting a specific target in cancer cells and reducing unwanted side effects has become a promising strategy in pancreatic cancer treatment. MAP4K4 is associated with pancreatic cancer development and correlates with poor clinical outcomes. By phosphorylating MKK4, proteins associated with cell apoptosis and survival are translated. Therefore, inhibiting MAP4K4 activity in pancreatic tumours is a new therapeutic strategy. Herein, we performed a structure-based virtual screening to identify MAP4K4 inhibitors and discovered the compound F389-0746 with a potent inhibition (IC₅₀ 120.7 nM). The results of kinase profiling revealed that F389-0746 was highly selective to MAP4K4 and less likely to cause side effects. Results of in vitro experiments showed that F389-0746 significantly suppressed cancer cell growth and viability. Results of in vivo experiments showed that F389-0746 displayed comparable tumour growth inhibition with the group treated with gemcitabine. These findings suggest that F389-0746 has promising potential to be further developed as a novel pancreatic cancer treatment.

Map4k4 is up-regulated and modulates granulosa cell injury and oxidative stress in polycystic ovary syndrome via activating JNK/c-JUN pathway: An experimental study

The regulatory mechanism on granulosa cells (GCs) oxidative injury is becoming increasingly important in polycystic ovary syndrome (PCOS) studies. Serine/threonine kinase mitogen-activated protein 4 kinase 4 (Map4k4) is linked with oxidative injury and possibly associated with premature ovarian failure and ovarian dysgenesis. Herein, we investigated the function and mechanism of Map4k4 in a PCOS rat model. A microarray from GEO database identified Map4k4 was up-regulated in the ovarian of PCOS rats, and functional enrichments suggested that oxidative stress-associated changes are involved. We verified the raised Map4k4 expression in an established PCOS rat model and also in the isolated PCOS-GCs, which were consistent with the microarray data. Map4k4 knockdown in vivo contributed to regular estrous cycle, restrained steroid concentrations and ovarian injury in PCOS rats. Both Map4k4 silencing in vivo and in vitro attenuated the PCOS-related GC oxidative stress and apoptosis. Mechanically, Map4k4 activated the JNK/c-JUN signaling pathway. Importantly, a JNK agonist restored the suppressive effects of Map4k4 silencing on PCOS-induced granulosa cell injury and oxidative stress. Besides, Map4k4 may be a target gene of miR-185-5p. In conclusion, Map4k4, a potential target of miR-185-5p, is up-regulated and induces ovarian GC oxidative injury by activating JNK/c-JUN pathway in PCOS. The Map4k4/JNK/c-JUN mechanism may provide a new idea on the treatment of PCOS.

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.

Abrogation of MAP4K4 protein function causes congenital anomalies in humans and zebrafish

We report 21 families displaying neurodevelopmental differences and multiple congenital anomalies while bearing a series of rare variants in mitogen-activated protein kinase kinase kinase kinase 4 (MAP4K4). MAP4K4 has been implicated in many signaling pathways including c-Jun N-terminal and RAS kinases and is currently under investigation as a druggable target for multiple disorders. Using several zebrafish models, we demonstrate that these human variants are either loss-of-function or dominant-negative alleles and show that decreasing Map4k4 activity causes developmental defects. Furthermore, MAP4K4 can restrain hyperactive RAS signaling in early embryonic stages. Together, our data demonstrate that MAP4K4 negatively regulates RAS signaling in the early embryo and that variants identified in affected humans abrogate its function, establishing MAP4K4 as a causal locus for individuals with syndromic neurodevelopmental differences.

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.

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.

MAP4K4/JNK Signaling Pathway Stimulates Proliferation and Suppresses Apoptosis of Human Spermatogonial Stem Cells and Lower Level of MAP4K4 Is Associated with Male Infertility

Spermatogonial stem cells (SSCs) serve as a foundation for spermatogenesis and they are essential for male fertility. The fate of SSC is determined by genetic and epigenetic regulatory networks. Many molecules that regulate SSC fate determinations have been identified in mice. However, the molecules and signaling pathways underlying human SSCs remain largely unclear. In this study, we have demonstrated that MAP4K4 was predominantly expressed in human UCHL1-positive spermatogonia by double immunocytochemical staining. MAP4K4 knockdown inhibited proliferation of human SSCs and induced their apoptosis. Moreover, MAP4K4 silencing led to inhibition of JNK phosphorylation and MAP4K4 phosphorylation at Ser801. RNA sequencing indicated that MAP4K4 affected the transcription of SPARC, ADAM19, GPX7, GNG2, and COLA1. Interestingly, the phenotype of inhibiting JNK phosphorylation by SP600125 was similar to MAP4K4 knockdown. Notably, MAP4K4 protein was lower in the testes of patients with non-obstructive azoospermia than those with normal spermatogenesis as shown by Western blots and immunohistochemistry. Considered together, our data implicate that MAP4K4/JNK signaling pathway mediates proliferation and apoptosis of human SSCs, which provides a novel insight into molecular mechanisms governing human spermatogenesis and might offer new targets for gene therapy of male infertility.

Bioinformatics and Experimental Analyses Reveal MAP4K4 as a Potential Marker for Gastric Cancer

Background: Gastric cancer remains the most prevalent and highly lethal disease worldwide. MAP4K4, a member of Ste20, plays an important role in various pathologies, including cancer. However, its role in gastric cancer is not yet fully elucidated. Therefore, this study aims to determine the tumor-promoting role of MAP4K4 in gastric cancer and whether it can be used as a new and reliable biomarker to predict the prognosis of gastric cancer. For this purpose, we divide the samples into high- and low-expression groups according to the expression level of MAP4K4. The association of MAP4K4 expression with prognosis is assessed using the Kaplan–Meier survival analysis. Furthermore, immune infiltration analysis using ESTIMATE is conducted to evaluate the tumor immune scores of the samples. Results: The findings reveal a significantly higher expression of MAP4K4 in tumor samples than in adjacent samples. The high-expression group was significantly enriched in tumor-related pathways, such as the PI3K-Akt signaling pathway. In addition, immune infiltration analysis revealed a positive correlation between immune scores and MAP4K4 expression. We also observed that miRNAs, such as miR-192-3p (R = −0.317, p-value 3.111 × 10⁻⁹), miR-33b-5p (R= −0.238, p-value 1.166 × 10⁻⁵), and miR-582-3p (R = −0.214, p-value 8.430 × 10⁻⁵), had potential negative regulatory effects on MAP4K4. Moreover, we identified several transcription factors, ubiquitinated proteins, and interacting proteins that might regulate MAP4K4. The relationship between MAP4K4 and DNA methylation was also identified. Finally, we verified the high expression of MAP4K4 and its effect on promoting cancer. Conclusion: MAP4K4 might be closely related to gastric cancer’s progression, invasion, and metastasis. Its high expression negatively impacts the prognosis of gastric cancer patients. This suggests MAP4K4 as an important prognostic factor for gastric cancer and could be regarded as a new potential prognostic detection and therapeutic target.

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.

Identification and Validation of Aging-Related Genes in Alzheimer’s Disease

Aging is recognized as the key risk factor for Alzheimer’s disease (AD). This study aimed to identify and verify potential aging-related genes associated with AD using bioinformatics analysis. Aging-related differential expression genes (ARDEGs) were determined by the intersection of limma test, weighted correlation network analysis (WGCNA), and 1153 aging and senescence-associated genes. Potential biological functions and pathways of ARDEGs were determined by GO, KEGG, GSEA, and GSVA. Then, LASSO algorithm was used to identify the hub genes and the diagnostic ability of the five ARDEGs in discriminating AD from the healthy control samples. Further, the correlation between hub ARDEGs and clinical characteristics was explored. Finally, the expression level of the five ARDEGs was validated using other four GEO datasets and blood samples of patients with AD and healthy individuals. Five ARDEGs (GFAP, PDGFRB, PLOD1, MAP4K4, and NFKBIA) were obtained. For biological function analysis, aging, cellular senescence, and Ras protein signal transduction regulation were enriched. Diagnostic ability of the five ARDEGs in discriminating AD from the control samples demonstrated a favorable diagnostic value. Eventually, quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) validation test revealed that compared with healthy controls, the mRNA expression level of PDGFRB, PLOD1, MAP4K4, and NFKBIA were elevated in AD patients. In conclusion, this study identified four ARDEGs (PDGFRB, PLOD1, MAP4K4, and NFKBIA) associated with AD. They provide an insight into potential novel biomarkers for diagnosing AD and monitoring progression.

The HPK1 Inhibitor A-745 Verifies the Potential of Modulating T Cell Kinase Signaling for Immunotherapy

Hematopoietic progenitor kinase 1 (HPK1) is an MAP4K family member within the Ste20-like serine/threonine branch of the kinome. HPK1 expression is limited to hematopoietic cells and has a predominant role as a negative regulator of T cell function. Because of the central/dominant role in negatively regulating T cell function, HPK1 has long been in the center of interest as a potential pharmacological target for immune therapy. The development of a small molecule HPK1 inhibitor remains challenging because of the need for high specificity relative to other kinases, including additional MAP4K family members, that are required for efficient immune cell activation. Here, we report the identification of the selective and potent HPK1 chemical probe, A-745. In unbiased cellular kinase-binding assays, A-745 demonstrates an excellent cellular selectivity binding profile within pharmacologically relevant concentrations. This HPK1 selectivity translates to an in vitro immune cell activation phenotype reminiscent of Hpk1-deficient and Hpk1-kinase-dead T cells, including augmented proliferation and cytokine production. The results from this work give a path forward for further developmental efforts to generate additional selective and potent small molecule HPK1 inhibitors with the pharmacological properties for immunotherapy.

Recent Advances in Small Molecule Stimulation of Regeneration and Repair

Therapeutic approaches to stimulate regeneration and repair have the potential to transform healthcare and improve outcomes for patients suffering from numerous chronic degenerative diseases. To date most approaches have involved the transplantation of therapeutic cells, and while there have been a small number of clinical approvals, major hurdles exist to the routine adoption of such therapies. In recent years humans and other mammals have been shown to possess a regenerative capacity across multiple tissues and organs, and an innate regenerative and repair response has been shown to be activated in these organs in response to injury. These realisations have inspired a transformative approach in regenerative medicine: the development of new agents to directly target these innate regeneration and repair pathways. In this article we will review the current state of the art in the discovery of small molecule modulators of regeneration and their translation towards therapeutic agents, focussing specifically on the areas of neuroregeneration and cardiac regeneration.

The genetic deletion of the Dual Specificity Phosphatase 3 (DUSP3) attenuates kidney damage and inflammation following ischaemia/reperfusion injury in mouse

AIM

Dual Specificity Phosphatase 3 (DUSP3) regulates the innate immune response, with a putative role in angiogenesis. Modulating inflammation and perfusion contributes to renal conditioning against ischaemia/reperfusion (I/R). We postulate that the functional loss of DUSP3 is associated with kidney resistance to I/R.

METHODS

Ten C57BL/6 male WT and Dusp3^-/- mice underwent right nephrectomy and left renal I/R (30 min/48 hours). Renal injury was assessed based on serum levels of urea (BUN) and Jablonski score. The expression of CD31 and VEGF vascular markers was quantified by RT-qPCR and immuno-staining. Renal resistivity index (RRI) was measured in vivo by Doppler ultrasound. Comparative phosphoproteomics was conducted using IMAC enrichment of phosphopeptides. Inflammatory markers were quantified at both mRNA and protein levels in ischaemic vs non-ischaemic kidneys in WT vs Dusp3^-/- .

RESULTS

At baseline, we located DUSP3 in renal glomeruli and endothelial cells. CD31-positive vascular network was significantly larger in Dusp3^-/- kidneys compared to WT, with a lower RRI in Dusp3^-/- mice. Following I/R, BUN and Jablonski score were significantly lower in Dusp3^-/- vs WT mice. Phosphoproteomics highlighted a down-regulation of inflammatory pathways and up-regulation of phospho-sites involved in cell metabolism and VEGF-related angiogenesis in Dusp3^-/- vs WT ischaemic kidneys. Dusp3^-/- ischaemic kidneys showed decreased mRNA levels of CD11b, TNF-α, KIM-1, IL-6, IL-1β and caspase-3 compared to controls. The numbers of PCNA-, F4-80- and CD11b-positive cells were reduced in Dusp3^-/- vs WT kidneys post-I/R.

CONCLUSION

Genetic inactivation of Dusp3 is associated with kidney conditioning against I/R, possibly due to attenuated inflammation and improved perfusion.

Epidrugs in Amyotrophic Lateral Sclerosis/Frontotemporal Dementia: Contextualizing a Role for Histone Kinase Inhibition in Neurodegenerative Disease

Breakthroughs in understanding the epigenetic mechanisms involved in neurodegenerative disease have highlighted "epidrugs" as a potential avenue for therapeutic development. Here, we expand on the future of epidrugs against neurodegeneration and discuss promising novel targets underexploited thus far: histone kinases.

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.

AR-negative prostate cancer is vulnerable to loss of JMJD1C demethylase

Prostate cancer is a leading cause of cancer-related mortality in men. The widespread use of androgen receptor (AR) inhibitors has generated an increased incidence of AR-negative prostate cancer, triggering the need for effective therapies for such patients. Here, analysis of public genome-wide CRISPR screens in human prostate cancer cell lines identified histone demethylase JMJD1C (KDM3C) as an AR-negative context-specific vulnerability. Secondary validation studies in multiple cell lines and organoids, including isogenic models, confirmed that small hairpin RNA (shRNA)-mediated depletion of JMJD1C potently inhibited growth specifically in AR-negative prostate cancer cells. To explore the cooperative interactions of AR and JMJD1C, we performed comparative transcriptomics of 1) isogenic AR-positive versus AR-negative prostate cancer cells, 2) AR-positive versus AR-negative prostate cancer tumors, and 3) isogenic JMJD1C-expressing versus JMJD1C-depleted AR-negative prostate cancer cells. Loss of AR or JMJD1C generates a modest tumor necrosis factor alpha (TNFα) signature, whereas combined loss of AR and JMJD1C strongly up-regulates the TNFα signature in human prostate cancer, suggesting TNFα signaling as a point of convergence for the combined actions of AR and JMJD1C. Correspondingly, AR-negative prostate cancer cells showed exquisite sensitivity to TNFα treatment and, conversely, TNFα pathway inhibition via inhibition of its downstream effector MAP4K4 partially reversed the growth defect of JMJD1C-depleted AR-negative prostate cancer cells. Given the deleterious systemic side effects of TNFα therapy in humans and the viability of JMJD1C-knockout mice, the identification of JMJD1C inhibition as a specific vulnerability in AR-negative prostate cancer may provide an alternative drug target for prostate cancer patients progressing on AR inhibitor therapy.

A 5'-tRNA halve, tiRNA-Gly promotes cell proliferation and migration via binding to RBM17 and inducing alternative splicing in papillary thyroid cancer

Background

tRNA-derived small noncoding RNAs (sncRNAs) are mainly categorized into tRNA halves (tiRNAs) and fragments (tRFs). Biological functions of tiRNAs in human solid tumor are attracting more and more attention, but researches concerning the mechanisms in tiRNAs-mediated tumorigenesis are rarely. The direct regulatory relationship between tiRNAs and splicing-related proteins remain elusive.

Methods

Papillary thyroid carcinoma (PTC) associated tRNA fragments were screened by tRNA fragments deep sequencing and validated by qRT-PCR and Northern Blot in PTC tissues. The biological function of tRNA fragments were assessed by cell counting kit, transwells and subcutaneous transplantation tumor of nude mice. For mechanistic study, tRNA fragments pull-down, RNA immunoprecipitation, Western Blot, Immunofluorescence, Immunohistochemical staining were performed.

Results

Herein, we have identified a 33 nt tiRNA-Gly significantly increases in papillary thyroid cancer (PTC) based on tRFs & tiRNAs sequencing. The ectopic expression of tiRNA-Gly promotes cell proliferation and migration, whereas down-regulation of tiRNA-Gly exhibits reverse effects. Mechanistic investigations reveal tiRNA-Gly directly bind the UHM domain of a splicing-related RNA-binding protein RBM17. The interaction with tiRNA-Gly could translocate RBM17 from cytoplasm into nucleus. In addition, tiRNA-Gly increases RBM17 protein expression via inhibiting its degradation in a ubiquitin/proteasome-dependent way. Moreover, RBM17 level in tiRNA-Gly high-expressing human PTC tissues is upregulated. In vivo mouse model shows that suppression of tiRNA-Gly decreases RBM17 expression. Importantly, tiRNA-Gly can induce exon 16 splicing of MAP4K4 mRNA leading to phosphorylation of downstream signaling pathway, which is RBM17 dependent.

Conclusions

Our study firstly illustrates tiRNA-Gly can directly bind to RBM17 and display oncogenic effect via RBM17-mediated alternative splicing. This fully novel model broadens our understanding of molecular mechanism in which tRNA fragment in tumor cells directly bind RNA binding protein and play a role in alternative splicing.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02024-3.

Comprehensive analysis of DNA methylation and gene expression profiles in gestational diabetes mellitus

ABSTRACT

Gestational diabetes mellitus (GDM) has a high prevalence during pregnancy. This research aims to identify genes and their pathways related to GDM by combining bioinformatics analysis.The DNA methylation and gene expression profiles data set was obtained from Gene Expression Omnibus. Differentially expressed genes (DEG) and differentially methylated genes (DMG) were screened by R package limma. The methylation-regulated differentially expressed genes (MeDEGs) were obtained by overlapping the DEGs and DMGs. A protein-protein interaction network was constructed using the search tool for searching interacting genes. The results are visualized in Cytoscape. Disease-related miRNAs and pathways were retrieved from Human MicroRNA Disease Database and Comparative Toxic Genome Database. Real-time quantitative PCR further verified the expression changes of these genes in GDM tissues and normal tissues.After overlapping DEGs and DMGs, 138 MeDEGs were identified. These genes were mainly enriched in the biological processes of the "immune response," "defense response," and "response to wounding." Pathway enrichment shows that these genes are involved in "Antigen processing and presentation," "Graft-versus-host disease," "Type I diabetes mellitus," and "Allograft rejection." Six mRNAs (including superoxide dismutase 2 (SOD2), mitogen-activated protein kinase kinase kinase kinase 3 (MAP4K3), dual specificity phosphatase 5 (DUSP5), p21-activated kinases 2 (PAK2), serine protease inhibitor clade E member 1 (SERPINE1), and protein phosphatase 1 regulatory subunit 15B (PPP1R15B)) were identified as being related to GDM. The results obtained by real-time quantitative PCR are consistent with the results of the microarray analysis.This study identified new types of MeDEGs and discovered their related pathways and functions in GDM, which may be used as molecular targets and diagnostic biomarkers for the precise diagnosis and treatment of GDM.

MAP4K4 expression in cardiomyocytes: multiple isoforms, multiple phosphorylations and interactions with striatins

The Ser/Thr kinase MAP4K4, like other GCKIV kinases, has N-terminal kinase and C-terminal citron homology (CNH) domains. MAP4K4 can activate c-Jun N-terminal kinases (JNKs), and studies in the heart suggest it links oxidative stress to JNKs and heart failure. In other systems, MAP4K4 is regulated in striatin-interacting phosphatase and kinase (STRIPAK) complexes, in which one of three striatins tethers PP2A adjacent to a kinase to keep it dephosphorylated and inactive. Our aim was to understand how MAP4K4 is regulated in cardiomyocytes. The rat MAP4K4 gene was not properly defined. We identified the first coding exon of the rat gene using 5′-RACE, we cloned the full-length sequence and confirmed alternative-splicing of MAP4K4 in rat cardiomyocytes. We identified an additional α-helix C-terminal to the kinase domain important for kinase activity. In further studies, FLAG-MAP4K4 was expressed in HEK293 cells or cardiomyocytes. The Ser/Thr protein phosphatase inhibitor calyculin A (CalA) induced MAP4K4 hyperphosphorylation, with phosphorylation of the activation loop and extensive phosphorylation of the linker between the kinase and CNH domains. This required kinase activity. MAP4K4 associated with myosin in untreated cardiomyocytes, and this was lost with CalA-treatment. FLAG-MAP4K4 associated with all three striatins in cardiomyocytes, indicative of regulation within STRIPAK complexes and consistent with activation by CalA. Computational analysis suggested the interaction was direct and mediated via coiled-coil domains. Surprisingly, FLAG-MAP4K4 inhibited JNK activation by H₂O₂ in cardiomyocytes and increased myofibrillar organisation. Our data identify MAP4K4 as a STRIPAK-regulated kinase in cardiomyocytes, and suggest it regulates the cytoskeleton rather than activates JNKs.

HGK promotes metastatic dissemination in prostate cancer

Metastasis is the process of cancer cell dissemination from primary tumors to different organs being the bone the preferred site for metastatic homing of prostate cancer (PCa) cells. Prostate tumorigenesis is a multi-stage process that ultimately tends to advance to become metastatic PCa. Once PCa patients develop skeletal metastases, they eventually succumb to the disease. Therefore, it is imperative to identify essential molecular drivers of this process to develop new therapeutic alternatives for the treatment of this devastating disease. Here, we have identified MAP4K4 as a relevant gene for metastasis in PCa. Our work shows that genetic deletion of MAP4K4 or pharmacological inhibition of its encoded kinase, HGK, inhibits metastatic PCa cells migration and clonogenic properties. Hence, MAP4K4 might promote metastasis and tumor growth. Mechanistically, our results indicate that HGK depleted cells exhibit profound differences in F-actin organization, increasing cell spreading and focal adhesion stability. Additionally, HGK depleted cells fails to respond to TNF-α stimulation and chemoattractant action. Moreover, here we show that HGK upregulation in PCa samples from TCGA and other databases correlates with a poor prognosis of the disease. Hence, we suggest that it could be used as prognostic biomarker to predict the appearance of an aggressive phenotype of PCa tumors and ultimately, the appearance of metastasis. In summary, our results highlight an essential role for HGK in the dissemination of PCa cells and its potential use as prognostic biomarker.

A new function for MAP4K4 inhibitors during platelet aggregation and platelet-mediated clot retraction

Mitogen-activated protein kinase kinase kinase kinase 4 (MAP4K4) is implicated in type 2 diabetes mellitus, insulin tolerance, inflammation, cancer, and atherosclerosis. We found that GNE 495 and PF 06260933 (both potent and selective MAP4K4 inhibitors) regulated human platelet activation. Immunoblotting revealed human platelets express MAP4K4, and that GNE 495 and PF 06260933 inhibited collagen-, ADP-, and thrombin-induced platelet aggregation and eventually suppressed granule release, TXA₂ generation, integrin α_IIbβ₃ activation, and clot retraction. In addition, both inhibitors elevated intracellular levels of cAMP, and coincubation with GNE 495 and aspirin or dipyridamole (a phosphodiesterase inhibitor) synergistically inhibited collagen-induced platelet aggregation and TXA₂ generation. Moreover, both inhibitors phosphorylated VASP (ser¹⁵⁷), IP3 receptor, and PKA and attenuated MAPK and PI3K/Akt/GSK3β signaling pathways. This study is the first to demonstrate that MAP4K4 inhibitors reduce thrombus formation by inhibiting platelet activation. These findings also suggest MAP4K4 be considered an emerging target protein for the treatment of thrombosis.

Activation of c-Jun N-Terminal Kinase, a Potential Therapeutic Target in Autoimmune Arthritis

The c-Jun-N-terminal kinase (JNK) is a critical mediator involved in various physiological processes, such as immune responses, and the pathogenesis of various diseases, including autoimmune disorders. JNK is one of the crucial downstream signaling molecules of various immune triggers, mainly proinflammatory cytokines, in autoimmune arthritic conditions, mainly including rheumatoid arthritis, ankylosing spondylitis, and psoriatic arthritis. The activation of JNK is regulated in a complex manner by upstream kinases and phosphatases. Noticeably, different subtypes of JNKs behave differentially in immune responses. Furthermore, aside from biologics targeting proinflammatory cytokines, small-molecule inhibitors targeting signaling molecules such as Janus kinases can act as very powerful therapeutics in autoimmune arthritis patients unresponsiveness to conventional synthetic antirheumatic drugs. Nevertheless, despite these encouraging therapies, a population of patients with an inadequate therapeutic response to all currently available medications still remains. These findings identify the critical signaling molecule JNK as an attractive target for investigation of the immunopathogenesis of autoimmune disorders and for consideration as a potential therapeutic target for patients with autoimmune arthritis to achieve better disease control. This review provides a useful overview of the roles of JNK, how JNK is regulated in immunopathogenic responses, and the potential of therapeutically targeting JNK in patients with autoimmune arthritis.

DUSP11 Attenuates Lipopolysaccharide-Induced Macrophage Activation by Targeting TAK1

Dual-specificity phosphatase 11 (DUSP11, also named as PIR1) is a member of the atypical DUSP protein tyrosine phosphatase family. DUSP11 is only known to be an RNA phosphatase that regulates noncoding RNA stability. To date, the role of DUSP11 in immune cell signaling and immune responses remains unknown. In this study, we generated and characterized the immune cell functions of DUSP11-deficient mice. We identified TGF-β-activated kinase 1 (TAK1) as a DUSP11-targeted protein. DUSP11 interacted directly with TAK1, and the DUSP11-TAK1 interaction was enhanced by LPS stimulation in bone marrow-derived macrophages. DUSP11 deficiency enhanced the LPS-induced TAK1 phosphorylation and cytokine production in bone marrow-derived macrophages. Furthermore, DUSP11-deficient mice were more susceptible to LPS-induced endotoxic shock. The LPS-induced serum levels of IL-1β, TNF-α, and IL-6 were significantly elevated in DUSP11-deficient mice compared with those of wild-type mice. The data indicate that DUSP11 inhibits LPS-induced macrophage activation by targeting TAK1.

TAK1 mediates convergence of cellular signals for death and survival

TGF-β activated kinase 1, a MAPK kinase kinase family serine threonine kinase has been implicated in regulating diverse range of cellular processes that include embryonic development, differentiation, autophagy, apoptosis and cell survival. TAK1 along with its binding partners TAB1, TAB2 and TAB3 displays a complex pattern of regulation that includes serious crosstalk with major signaling pathways including the C-Jun N-terminal kinase (JNK), p38 MAPK, and I-kappa B kinase complex (IKK) involved in establishing cellular commitments for death and survival. This review also highlights how TAK1 orchestrates regulation of energy homeostasis via AMPK and its emerging role in influencing mTORC1 pathway to regulate death or survival in tandem.

Kinome Profiling Reveals Abnormal Activity of Kinases in Skeletal Muscle From Adults With Obesity and Insulin Resistance

CONTEXT

Obesity-related insulin resistance (OIR) is one of the main contributors to type 2 diabetes and other metabolic diseases. Protein kinases are implicated in insulin signaling and glucose metabolism. Molecular mechanisms underlying OIR involving global kinase activities remain incompletely understood.

OBJECTIVE

To investigate abnormal kinase activity associated with OIR in human skeletal muscle.

DESIGN

Utilization of stable isotopic labeling-based quantitative proteomics combined with affinity-based active enzyme probes to profile in vivo kinase activity in skeletal muscle from lean control (Lean) and OIR participants.

PARTICIPANTS

A total of 16 nondiabetic adults, 8 Lean and 8 with OIR, underwent hyperinsulinemic-euglycemic clamp with muscle biopsy.

RESULTS

We identified the first active kinome, comprising 54 active protein kinases, in human skeletal muscle. The activities of 23 kinases were different in OIR muscle compared with Lean muscle (11 hyper- and 12 hypo-active), while their protein abundance was the same between the 2 groups. The activities of multiple kinases involved in adenosine monophosphate-activated protein kinase (AMPK) and p38 signaling were lower in OIR compared with Lean. On the contrary, multiple kinases in the c-Jun N-terminal kinase (JNK) signaling pathway exhibited higher activity in OIR vs Lean. The kinase-substrate-prediction based on experimental data further confirmed a potential downregulation of insulin signaling (eg, inhibited phosphorylation of insulin receptor substrate-1 and AKT1/2).

CONCLUSIONS

These findings provide a global view of the kinome activity in OIR and Lean muscle, pinpoint novel specific impairment in kinase activities in signaling pathways important for skeletal muscle insulin resistance, and may provide potential drug targets (ie, abnormal kinase activities) to prevent and/or reverse skeletal muscle insulin resistance in humans.

STRIPAK directs PP2A activity toward MAP4K4 to promote oncogenic transformation of human cells

Alterations involving serine-threonine phosphatase PP2A subunits occur in a range of human cancers, and partial loss of PP2A function contributes to cell transformation. Displacement of regulatory B subunits by the SV40 Small T antigen (ST) or mutation/deletion of PP2A subunits alters the abundance and types of PP2A complexes in cells, leading to transformation. Here, we show that ST not only displaces common PP2A B subunits but also promotes A-C subunit interactions with alternative B subunits (B''', striatins) that are components of the Striatin-interacting phosphatase and kinase (STRIPAK) complex. We found that STRN4, a member of STRIPAK, is associated with ST and is required for ST-PP2A-induced cell transformation. ST recruitment of STRIPAK facilitates PP2A-mediated dephosphorylation of MAP4K4 and induces cell transformation through the activation of the Hippo pathway effector YAP1. These observations identify an unanticipated role of MAP4K4 in transformation and show that the STRIPAK complex regulates PP2A specificity and activity.

MAP4K Family Kinases and DUSP Family Phosphatases in T-Cell Signaling and Systemic Lupus Erythematosus

T cells play a critical role in the pathogenesis of systemic lupus erythematosus (SLE), which is a severe autoimmune disease. In the past 60 years, only one new therapeutic agent with limited efficacy has been approved for SLE treatment; therefore, the development of early diagnostic biomarkers and therapeutic targets for SLE is desirable. Mitogen-activated protein kinase kinase kinase kinases (MAP4Ks) and dual-specificity phosphatases (DUSPs) are regulators of MAP kinases. Several MAP4Ks and DUSPs are involved in T-cell signaling and autoimmune responses. HPK1 (MAP4K1), DUSP22 (JKAP), and DUSP14 are negative regulators of T-cell activation. Consistently, HPK1 and DUSP22 are downregulated in the T cells of human SLE patients. In contrast, MAP4K3 (GLK) is a positive regulator of T-cell signaling and T-cell-mediated immune responses. MAP4K3 overexpression-induced RORγt–AhR complex specifically controls interleukin 17A (IL-17A) production in T cells, leading to autoimmune responses. Consistently, MAP4K3 and the RORγt–AhR complex are overexpressed in the T cells of human SLE patients, as are DUSP4 and DUSP23. In addition, DUSPs are also involved in either human autoimmune diseases (DUSP2, DUSP7, DUSP10, and DUSP12) or T-cell activation (DUSP1, DUSP5, and DUSP14). In this review, we summarize the MAP4Ks and DUSPs that are potential biomarkers and/or therapeutic targets for SLE.

Development of MAP4 Kinase Inhibitors as Motor Neuron-Protecting Agents

Disease-causing mutations in many neurodegenerative disorders lead to proteinopathies that trigger endoplasmic reticulum (ER) stress. However, few therapeutic options exist for patients with these diseases. Using an in vitro screening platform to identify compounds that protect human motor neurons from ER stress-mediated degeneration, we discovered that compounds targeting the mitogen-activated protein kinase kinase kinase kinase (MAP4K) family are neuroprotective. The kinase inhibitor URMC-099 (compound 1) stood out as a promising lead compound for further optimization. We coupled structure-based compound design with functional activity testing in neurons subjected to ER stress to develop a series of analogs with improved MAP4K inhibition and concomitant increases in potency and efficacy. Further structural modifications were performed to enhance the pharmacokinetic profiles of the compound 1 derivatives. Prostetin/12k emerged as an exceptionally potent, metabolically stable, and blood-brain barrier-penetrant compound that is well suited for future testing in animal models of neurodegeneration.

MAP4K3/GLK in autoimmune disease, cancer and aging

MAP4K3 (also named GLK) is a serine/threonine kinase, which belongs to the mammalian Ste20-like kinase family. At 22 years of age, GLK was initially cloned and identified as an upstream activator of the MAPK JNK under an environmental stress and proinflammatory cytokines. The data derived from GLK-overexpressing or shRNA-knockdown cell lines suggest that GLK may be involved in cell proliferation through mTOR signaling. GLK phosphorylates the transcription factor TFEB and retains TFEB in the cytoplasm, leading to inhibition of cell autophagy. After generating and characterizing GLK-deficient mice, the important in vivo roles of GLK in T-cell activation were revealed. In T cells, GLK directly interacts with and activates PKCθ through phosphorylating PKCθ at Ser-538 residue, leading to activation of IKK/NF-κB. Thus, GLK-deficient mice display impaired T-cell-mediated immune responses and decreased inflammatory phenotypes in autoimmune disease models. Consistently, the percentage of GLK-overexpressing T cells is increased in the peripheral blood from autoimmune disease patients; the GLK-overexpressing T cell population is correlated with disease severity of patients. The pathogenic mechanism of autoimmune disease by GLK overexpression was unraveled by characterizing T-cell-specific GLK transgenic mice and using biochemical analyses. GLK overexpression selectively promotes IL-17A transcription by inducing the AhR-RORγt complex in T cells. In addition, GLK overexpression in cancer tissues is correlated with cancer recurrence of human lung cancer and liver cancer; the predictive power of GLK overexpression for cancer recurrence is higher than that of pathologic stage. GLK directly phosphorylates and activates IQGAP1, resulting in induction of Cdc42-mediated cell migration and cancer metastasis. Furthermore, treatment of GLK inhibitor reduces disease severity of mouse autoimmune disease models and decreases IL-17A production of human autoimmune T cells. Due to the inhibitory function of HPK1/MAP4K1 in T-cell activation and the promoting effects of GLK on tumorigenesis, HPK1 and GLK dual inhibitors could be useful therapeutic drugs for cancer immunotherapy. In addition, GLK deficiency results in extension of lifespan in Caenorhabditis elegans and mice. Taken together, targeting MAP4K3 (GLK) may be useful for treating/preventing autoimmune disease, cancer metastasis/recurrence, and aging.

MAP4K4 Inhibition Promotes Survival of Human Stem Cell-Derived Cardiomyocytes and Reduces Infarct Size In Vivo

Heart disease is a paramount cause of global death and disability. Although cardiomyocyte death plays a causal role and its suppression would be logical, no clinical counter-measures target the responsible intracellular pathways. Therapeutic progress has been hampered by lack of preclinical human validation. Mitogen-activated protein kinase kinase kinase kinase-4 (MAP4K4) is activated in failing human hearts and relevant rodent models. Using human induced-pluripotent-stem-cell-derived cardiomyocytes (hiPSC-CMs) and MAP4K4 gene silencing, we demonstrate that death induced by oxidative stress requires MAP4K4. Consequently, we devised a small-molecule inhibitor, DMX-5804, that rescues cell survival, mitochondrial function, and calcium cycling in hiPSC-CMs. As proof of principle that drug discovery in hiPSC-CMs may predict efficacy in vivo, DMX-5804 reduces ischemia-reperfusion injury in mice by more than 50%. We implicate MAP4K4 as a well-posed target toward suppressing human cardiac cell death and highlight the utility of hiPSC-CMs in drug discovery to enhance cardiomyocyte survival.

Role of TLR4-MAP4K4 signaling pathway in models of oxygen-induced retinopathy

Retinopathy of prematurity is a vision-threatening condition, and therapies based on antagonizing VEGF may elicit serious side effects in premature infants. Mechanisms of retinal angiogenesis, particularly the signaling pathways independent of VEGF, remain elusive. The goals of our study were to explore TLR4-mediated signaling pathways in human retinal microvascular endothelial cells (HRMECs) and to examine the effects of TLR4 antagonists in models of oxygen-induced retinopathy (OIR). Our results show that intravitreal injection of the TLR4 antagonist TAK-242 reduced areas of nonperfusion, inhibited aberrant angiogenesis, and improved vascular density in the retina of OIR mice. The effects were further potentiated by the anti-VEGF antibody ranibizumab. In cultured HRMECs, the TLR4 agonist LPS up-regulated TLR4/MAPKK kinase kinase 4 (MAP4K4) signaling, and promoted cell proliferation and migration, and reduced barrier functions of the cells. Down-regulation of MAP4K4 in HRMECs abolished the proangiogenic effects by LPS. Our data suggest that the TLR4-MAP4K4 pathway can regulate retinal neovascularization via mechanisms independent of VEGF.-Chen, W., Zhang, J., Zhang, P., Hu, F., Jiang, T., Gu, J., Chang, Q. Role of TLR4-MAP4K4 signaling pathway in models of oxygen-induced retinopathy.

MAP4K4 Activation Mediates Motor Neuron Degeneration in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease affecting both upper and lower motor neurons (MNs). To date, its underlying mechanisms have yet to be clarified completely, and there are no truly effective treatments. Here, we show that MAP4K4, a MAP kinase family member, regulates MN death, with its suppression not only promoting survival but preventing neurite degeneration and decreasing mutant SOD1 levels through autophagy activation. Moreover, we report that MAP4K4 signaling specifically modulates MN viability via phosphorylated JNK3 and activation of the canonical c-Jun apoptotic pathway. Finally, we show the feasibility of MAP4K4 as a drug target by using an available MAP4K4-specific inhibitor, which improves survival of ESC and/or iPSC-derived MNs and MNs cultured from mouse spinal cords. In summary, our studies highlight a MAP4K4-initiated signaling cascade that induces MN degeneration, shedding light on the mechanism underlying MN degeneration and providing a druggable target for ALS therapeutics.

HGK-sestrin 2 signaling-mediated autophagy contributes to antitumor efficacy of Tanshinone IIA in human osteosarcoma cells

Tanshinone IIA (TIIA) is a diterpenoid naphthoquinone isolated from the herb Salvia miltiorrhiza with antitumor effects manifested at multiple levels that are mechanistically obscure. In our previous studies, we illustrated that TIIA treatment triggered apoptosis in human osteosarcoma 143B cells both in vitro and in vivo, accompanied with mitochondrial dysfunction. Importantly, the overall survival rate of patients with osteosarcoma who were randomly recruited to S. miltiorrhiza treatment was significantly higher than those without. Pursuing this observation, we evaluated the potential effect of TIIA on autophagy induction in osteosarcoma both in vivo and in vitro. We discovered that TIIA inhibited osteosarcoma cell survival through class I PI3K and Akt signaling pathways. In contrast, expression of class III PI3K required in the early stages of autophagosome generation was predominantly enhanced by TIIA treatment. Our study indicated that treatment of TIIA effectively induced autophagy in human osteosarcoma cells, which contributed to the blockade of anchorage-independent growth of osteosarcoma cells and ameliorated tumor progression in NOD/SCID mice. We demonstrated that TIIA-mediated autophagy occurred in a sestrin 2 (SESN2)-dependent but not Beclin 1-dependent manner. In addition, we defined the activation of HGK (MAP4K4 or mitogen-activated protein kinase kinase kinase kinase)/SAPK/JNK1/Jun kinase pathways in upregulating transcription of SESN2, in which TIIA triggered HGK/JNK1-dependent Jun activation and led to increased Jun recruitment to AP-1-binding site in the SESN2 promoter region. Our results offer novel mechanistic insight into how TIIA inhibits osteosarcoma growth and suggest TIIA as a promising therapeutic agent for the treatment of cancer.

Downregulated miR-98-5p promotes PDAC proliferation and metastasis by reversely regulating MAP4K4

BACKGROUND

The aberrant expression of microRNAs (miRNAs) has emerged as important hallmarks of cancer. However, the molecular mechanisms underlying the differences of miRNA expression remain unclear. Many studies have reported that miR-98-5p plays vital functions in the development and progression of multiple cancers. However, its role in pancreatic ductal adenocarcinoma (PDAC) remains unknown.

METHODS

The expression of miR-98-5p and its specific target gene were determined in human PDAC specimens and cell lines by miRNA qRT-PCR, qRT-PCR and western blot. The effects of miR-98-5p depletion or ectopic expression on PDAC proliferation, migration and invasion were evaluated in vitro using CCK-8 proliferation assays, colony formation assays, wound healing assays and transwell assays. Furthermore, the in vivo effects were investigated using the mouse subcutaneous xenotransplantation and pancreatic tail xenotransplantation models. Luciferase reporter assays were employed to identify interactions between miR-98-5p and its specific target gene.

RESULTS

MiR-98-5p expression was significantly lower in cancerous tissues and associated with tumor size, TNM stage, lymph node metastasis and survival. Notably, a series of gain- and loss-of-function assays elucidated that miR-98-5p suppressed PDAC cell proliferation, migration and invasion both in vitro and in vivo. Luciferase reporter assays, western blot and qRT-PCR revealed MAP4K4 to be a direct target of miR-98-5p. The effects of ectopic miR-98-5p were rescued by MAP4K4 overexpression. In contrast, the effects of miR-98-5p depletion were impaired by MAP4K4 knockdown. Furthermore, miR-98-5p suppressed the MAPK/ERK signaling pathway through downregulation of MAP4K4. In addition, the expression level of miR-98-5p was negatively correlated with MAP4K4 expression in PDAC tissues and cell lines.

CONCLUSIONS

These results suggest that downregulation of miR-98-5p promotes tumor development by downregulation of MAP4K4 and inhibition of the downstream MAPK/ERK signaling, thus, highlighting the potential of miR-98-5p as a therapeutic target for PDAC.

2-Aminopyridine-Based Mitogen-Activated Protein Kinase Kinase Kinase Kinase 4 (MAP4K4) Inhibitors: Assessment of Mechanism-Based Safety

Studies have linked the serine-threonine kinase MAP4K4 to the regulation of a number of biological processes and/or diseases, including diabetes, cancer, inflammation, and angiogenesis. With a majority of the members of our lead series (e.g., 1) suffering from time-dependent inhibition (TDI) of CYP3A4, we sought design avenues that would eliminate this risk. One such approach arose from the observation that carboxylic acid-based intermediates employed in our discovery efforts retained high MAP4K4 inhibitory potency and were devoid of the TDI risk. The medicinal chemistry effort that led to the discovery of this central nervous system-impaired inhibitor together with its preclinical safety profile is described.

GLK/MAP4K3 overexpression associates with recurrence risk for non-small cell lung cancer

Lung cancer is the leading cause of cancer death worldwide. Non-small cell lung cancer (NSCLC) accounts for 85% of total lung cancers; 40% to 60% of NSCLC patients die of cancer recurrence after cancer resection. Since GLK (also named MAP4K3) induces activation of NF-κB, which contributes to tumor progression, we investigated the role of GLK in NSCLC. GLK protein levels of 190 samples from pulmonary tissue arrays and 58 pulmonary resection samples from stage I to stage III NSCLC patients were studied using immunohistochemistry or immunoblotting. High levels of GLK proteins were detected in pulmonary tissues from NSCLC patients. Elevated GLK protein levels were correlated with increased recurrence risks and poor recurrence-free survival rates in NSCLC patients after adjusting for pathologic stage, smoking status, alcohol status, and EGFR levels. Thus, GLK is a novel prognostic biomarker for NSCLC recurrence.

Epigenetic regulation of HGK/MAP4K4 in T cells of type 2 diabetes patients

Type 2 diabetes (T2D) is a complex and heterogeneous disease. Obesity increases the risk of obese T2D; but in Asia non-obese T2D is prevalent. The cause of non-obese T2D has remained elusive. We studied the potential involvement of HGK/MAP4K4 in T2D using clinical samples from newly diagnosed, drug-naïve patients and healthy controls. HGK levels fell and IL-6 levels increased in T cells from T2D patients. Frequencies of IL-6-producing T cells were correlated with glucose levels after glucose-tolerance tests (but not body mass index and waist circumference) and inversely correlated with HGK expression levels. Moreover, methylation frequencies of the HGK promoter were increased in T2D patients and correlated with glucose levels after glucose-tolerance tests. The correlation was independent of body mass index. Demethylation treatment increased HGK expression levels and reduced IL-6 production in T2D T cells. This report identifies HGK methylation/downregulation in T cells as a potential biomarker for non-obese T2D.

MAP4K4 is a novel MAPK/ERK pathway regulator required for lung adenocarcinoma maintenance

About 76% of patients with lung adenocarcinoma harbor activating mutations in the receptor tyrosine kinase (RTK)/RAS/RAF pathways, leading to aberrant activation of the mitogen-activated protein kinase (MAPK) pathways particularly the MAPK/ERK pathway. However, many lung adenocarcinomas lacking these genomic mutations also display significant MAPK pathway activation, suggesting that additional MAPK pathway alterations remain undetected. This study has identified serine/threonine kinase mitogen-activated protein 4 kinase 4 (MAP4K4) as a novel positive regulator of MAPK/ERK signaling in lung adenocarcinoma. The results showed that MAP4K4 was drastically elevated in lung adenocarcinoma independently of KRAS or EGFR mutation status. Knockdown of MAP4K4 inhibited proliferation, anchorage-independent growth and migration of lung adenocarcinoma cells, and also inhibited human lung adenocarcinoma xenograft growth and metastasis. Mechanistically, we found that MAP4K4 activated ERK through inhibiting protein phosphatase 2 activity. Our results further showed that downregulation of MAP4K4 prevented ERK reactivation in EGFR inhibitor erlotinib-treated lung adenocarcinoma cells. Together, our findings identify MAP4K4 as a novel MAPK/ERK pathway regulator in lung adenocarcinoma that is required for lung adenocarcinoma maintenance.

MAP4K4 and IL-6+ Th17 cells play important roles in non-obese type 2 diabetes

Obesity is a causal factor of type 2 diabetes (T2D); however, people without obesity (including lean, normal weight, or overweight) may still develop T2D. Non-obese T2D is prevalent in Asia and also frequently occurs in Europe. Recently, multiple evidences oppose the notion that either obesity or central obesity (visceral fat accumulation) promotes non-obese T2D. Several factors such as inflammation and environmental factors contribute to non-obese T2D. According to the data derived from gene knockout mice and T2D clinical samples in Asia and Europe, the pathogenesis of non-obese T2D has been unveiled recently. MAP4K4 downregulation in T cells results in enhancement of the IL-6⁺ Th17 cell population, leading to insulin resistance and T2D in both human and mice. Moreover, MAP4K4 single nucleotide polymorphisms and epigenetic changes are associated with T2D patients. Interactions between MAP4K4 gene variants and environmental factors may contribute to MAP4K4 attenuation in T cells, leading to non-obese T2D. Future investigations of the pathogenesis of non-obese T2D shall lead to development of precision medicine for non-obese T2D.