Cloning and expression of ZAK, a mixed lineage kinase-like protein containing a leucine-zipper and a sterile-alpha motif

An atypical E3 ligase safeguards the ribosome during nutrient stress

Metabolic stress must be effectively mitigated for the survival of cells and organisms. Ribosomes have emerged as signaling hubs that sense metabolic perturbations and coordinate responses that either restore homeostasis or trigger cell death. As yet, the mechanisms governing these cell fate decisions are not well understood. Here, we report an unexpected role for the atypical E3 ligase HOIL-1 in safeguarding the ribosome. We find HOIL-1 mutations associated with cardiomyopathy broadly sensitize cells to nutrient and translational stress. These signals converge on the ribotoxic stress sentinel ZAKα. Mechanistically, mutant HOIL-1 excludes a ribosome quality control E3 ligase from its functional complex and remodels the ribosome ubiquitin landscape. This quality control failure renders glucose starvation ribotoxic, precipitating a ZAKα-ATF4-xCT-driven noncanonical cell death. We further show HOIL-1 loss exacerbates cardiac dysfunction under pressure overload. These data reveal an unrecognized ribosome signaling axis and a molecular circuit controlling cell fate during nutrient stress.

Dysregulated ribosome quality control in human diseases

Precise regulation of mRNA translation is of fundamental importance for maintaining homeostasis. Conversely, dysregulated general or transcript-specific translation, as well as abnormal translation events, have been linked to a multitude of diseases. However, driven by the misconception that the transient nature of mRNAs renders their abnormalities inconsequential, the importance of mechanisms that monitor the quality and fidelity of the translation process has been largely overlooked. In recent years, there has been a dramatic shift in this paradigm, evidenced by several seminal discoveries on the role of a key mechanism in monitoring the quality of mRNA translation - namely, Ribosome Quality Control (RQC) - in the maintenance of homeostasis and the prevention of diseases. Here, we will review recent advances in the field and emphasize the biological significance of the RQC mechanism, particularly its implications in human diseases.

Predicting bladder cancer survival with high accuracy: insights from MAPK pathway-related genes

The mitogen-activated protein kinase (MAPK) pathway plays a critical role in tumor development and immunotherapy. Nevertheless, additional research is necessary to comprehend the relationship between the MAPK pathway and the prognosis of bladder cancer (BLCA), as well as its influence on the tumor immune microenvironment. To create prognostic models, we screened ten genes associated with the MAPK pathway using COX and least absolute shrinkage and selection operator (LASSO) regression analysis. These models were validated in the Genomic Data Commons (GEO) cohort and further examined for immune infiltration, somatic mutation, and drug sensitivity characteristics. Finally, the findings were validated using The Human Protein Atlas (HPA) database and through Quantitative Real-time PCR (qRT-PCR). Patients were classified into high-risk and low-risk groups based on the prognosis-related genes of the MAPK pathway. The high-risk group had poorer overall survival than the low-risk group and showed increased immune infiltration compared to the low-risk group. Additionally, the nomograms built using the risk scores and clinical factors exhibited high accuracy in predicting the survival of BLCA patients. The prognostic profiling of MAPK pathway-associated genes represents a potent clinical prediction tool, serving as the foundation for precise clinical treatment of BLCA.

Heterozygous MAP3K20 variants cause ectodermal dysplasia, craniosynostosis, sensorineural hearing loss, and limb anomalies

Biallelic pathogenic variants in MAP3K20, which encodes a mitogen-activated protein kinase, are a rare cause of split-hand foot malformation (SHFM), hearing loss, and nail abnormalities or congenital myopathy. However, heterozygous variants in this gene have not been definitively associated with a phenotype. Here, we describe the phenotypic spectrum associated with heterozygous de novo variants in the linker region between the kinase domain and leucine zipper domain of MAP3K20. We report five individuals with diverse clinical features, including craniosynostosis, limb anomalies, sensorineural hearing loss, and ectodermal dysplasia-like phenotypes who have heterozygous de novo variants in this specific region of the gene. These individuals exhibit both shared and unique clinical manifestations, highlighting the complexity and variability of the disorder. We propose that the involvement of MAP3K20 in endothelial-mesenchymal transition provides a plausible etiology of these features. Together, these findings characterize a disorder that both expands the phenotypic spectrum associated with MAP3K20 and highlights the need for further studies on its role in early human development.

Myofibrillar myopathy hallmarks associated with ZAK deficiency

The ZAK gene encodes two functionally distinct kinases, ZAKα and ZAKβ. Homozygous loss of function mutations affecting both isoforms causes a congenital muscle disease. ZAKβ is the only isoform expressed in skeletal muscle and is activated by muscle contraction and cellular compression. The ZAKβ substrates in skeletal muscle or the mechanism whereby ZAKβ senses mechanical stress remains to be determined. To gain insights into the pathogenic mechanism, we exploited ZAK-deficient cell lines, zebrafish, mice and a human biopsy. ZAK-deficient mice and zebrafish show a mild phenotype. In mice, comparative histopathology data from regeneration, overloading, ageing and sex conditions indicate that while age and activity are drivers of the pathology, ZAKβ appears to have a marginal role in myoblast fusion in vitro or muscle regeneration in vivo. The presence of SYNPO2, BAG3 and Filamin C (FLNC) in a phosphoproteomics assay and extended analyses suggested a role for ZAKβ in the turnover of FLNC. Immunofluorescence analysis of muscle sections from mice and a human biopsy showed evidence of FLNC and BAG3 accumulations as well as other myofibrillar myopathy markers. Moreover, endogenous overloading of skeletal muscle exacerbated the presence of fibres with FLNC accumulations in mice, indicating that ZAKβ signalling is necessary for an adaptive turnover of FLNC that allows for the normal physiological response to sustained mechanical stress. We suggest that accumulation of mislocalized FLNC and BAG3 in highly immunoreactive fibres contributes to the pathogenic mechanism of ZAK deficiency.

Run, Ribosome, Run: From Compromised Translation to Human Health

Significance: Translation is an essential cellular process, and diverse signaling pathways have evolved to deal with problems arising during translation. Erroneous stalls and unresolved ribosome collisions are implicated in many pathologies, including neurodegeneration and metabolic dysregulation. Recent Advances: Many proteins involved in detection and clearance of stalled and collided ribosomes have been identified and studied in detail. Ribosome profiling techniques have revealed extensive and nonprogrammed ribosome stalling and leaky translation into the 3' untranslated regions of mRNAs. Impairment of protein synthesis has been linked to aging in yeast and mice. Critical Issues: Ribosomes act as sensors of cellular states, but the molecular mechanisms, as well as physiological relevance, remain understudied. Most of our current knowledge stems from work in yeast and simple multicellular organisms such as Caenorhabditis elegans, while we are only beginning to comprehend the role of ribosome surveillance in higher organisms. As an example, the ribotoxic stress response, a pathway responding to global translational stress, has been studied mostly in response to small translation inhibitors and ribotoxins, and has only recently been explored in physiological settings. This review focuses on ribosome-surveillance pathways and their importance for cell and tissue homeostasis upon naturally occurring insults such as oxidative stress, nutrient deprivation, and viral infections. Future Directions: A better insight into the physiological roles of ribosome-surveillance pathways and their crosstalk could lead to an improved understanding of human pathologies and aging. Antioxid. Redox Signal. 39, 336-350.

Proteomic and phosphoproteomic characteristics of the cortex, hippocampus, thalamus, lung, and kidney in COVID-19-infected female K18-hACE2 mice

BACKGROUND

Neurological damage caused by coronavirus disease 2019 (COVID-19) has attracted increasing attention. Recently, through autopsies of patients with COVID-19, the direct identification of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in their central nervous system (CNS) has been reported, indicating that SARS-CoV-2 might directly attack the CNS. The need to prevent COVID-19-induced severe injuries and potential sequelae is urgent, requiring the elucidation of large-scale molecular mechanisms in vivo.

METHODS

In this study, we performed liquid chromatography-mass spectrometry-based proteomic and phosphoproteomic analyses of the cortex, hippocampus, thalamus, lungs, and kidneys of SARS-CoV-2-infected K18-hACE2 female mice. We then performed comprehensive bioinformatic analyses, including differential analyses, functional enrichment, and kinase prediction, to identify key molecules involved in COVID-19.

FINDINGS

We found that the cortex had higher viral loads than did the lungs, and the kidneys did not have SARS-COV-2. After SARS-CoV-2 infection, RIG-I-associated virus recognition, antigen processing and presentation, and complement and coagulation cascades were activated to different degrees in all five organs, especially the lungs. The infected cortex exhibited disorders of multiple organelles and biological processes, including dysregulated spliceosome, ribosome, peroxisome, proteasome, endosome, and mitochondrial oxidative respiratory chain. The hippocampus and thalamus had fewer disorders than did the cortex; however, hyperphosphorylation of Mapt/Tau, which may contribute to neurodegenerative diseases, such as Alzheimer's disease, was found in all three brain regions. Moreover, SARS-CoV-2-induced elevation of human angiotensin-converting enzyme 2 (hACE2) was observed in the lungs and kidneys, but not in the three brain regions. Although the virus was not detected, the kidneys expressed high levels of hACE2 and exhibited obvious functional dysregulation after infection. This indicates that SARS-CoV-2 can cause tissue infections or damage via complicated routes. Thus, the treatment of COVID-19 requires a multipronged approach.

INTERPRETATION

This study provides observations and in vivo datasets for COVID-19-associated proteomic and phosphoproteomic alterations in multiple organs, especially cerebral tissues, of K18-hACE2 mice. In mature drug databases, the differentially expressed proteins and predicted kinases in this study can be used as baits to identify candidate therapeutic drugs for COVID-19. This study can serve as a solid resource for the scientific community. The data in this manuscript will serve as a starting point for future research on COVID-19-associated encephalopathy.

FUNDING

This study was supported by grants from the Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences, the National Natural Science Foundation of China, and the Natural Science Foundation of Beijing.

Domain Architecture of the Nonreceptor Tyrosine Kinase Ack1

The nonreceptor tyrosine kinase (NRTK) Ack1 comprises a distinct arrangement of non-catalytic modules. Its SH3 domain has a C-terminal to the kinase domain (SH1), in contrast to the typical SH3-SH2-SH1 layout in NRTKs. The Ack1 is the only protein that shares a region of high homology to the tumor suppressor protein Mig6, a modulator of EGFR. The vertebrate Acks make up the only tyrosine kinase (TK) family known to carry a UBA domain. The GTPase binding and SAM domains are also uncommon in the NRTKs. In addition to being a downstream effector of receptor tyrosine kinases (RTKs) and integrins, Ack1 can act as an epigenetic regulator, modulate the degradation of the epidermal growth factor receptor (EGFR), confer drug resistance, and mediate the progression of hormone-sensitive tumors. In this review, we discuss the domain architecture of Ack1 in relation to other protein kinases that possess such defined regulatory domains.

Targeted inhibition of ZAK ameliorates renal interstitial fibrosis

ZAK (sterile alpha motif and leucine zipper-containing kinase) is a newly discovered member of the subfamily of mitogen-activated protein kinase kinase kinases (MAP3Ks). The role of ZAK in kidney disease remains largely unknown. In this study, we systematically investigated the expression and function of ZAK in the progression of tubulointerstitial fibrosis (TIF). ZAK was induced, predominantly in tubular epithelium, in both fibrotic kidneys of human and mouse models with TIF. ZAK expression level was correlated with the extent of renal fibrosis and the decline of eGFR of CKD patients. Depleting ZAK attenuated TIF and inflammation induced by unilateral ureteral occlusion (UUO) together with decreased activation of p38 MAPK and Smads signaling. Moreover, we demonstrated that overexpressed ZAK was in complex with Smad2/3 and TGF-β receptor Ⅰ (TβRI). Whereas, silencing endogenous ZAK ameliorated the amount of Smad2/3 recruited to TβRI. Moreover, we discovered a novel small molecule inhibitor of ZAK, named 6p. In vitro, incubation with 6p inhibited TGF-β1-induced fibrogenic response in NRK52E cells. In vivo, intragastric administration of 6p ameliorated TIF and inflammation in UUO and unilateral ischemia-reperfusion injury model. Delayed administration of 6p was also effective in retarding the progression of the established TIF. In conclusion, ZAK is a novel therapeutic target for TIF, and 6p might be a potential therapeutic agent for TIF.

ZAKβ Alleviates Oxidized Low-density Lipoprotein (ox-LDL)-Induced Apoptosis and B-type Natriuretic Peptide (BNP) Upregulation in Cardiomyoblast

Oxidized low-density lipoprotein (ox-LDL) is a type of modified cholesterol that promotes apoptosis and inflammation and advances the progression of heart failure. Leucine-zipper and sterile-α motif kinase (ZAK) is a kinase of the MAP3K family which is highly expressed in the heart and encodes two variants, ZAKα and ZAKβ. Our previous study serendipitously found opposite effects of ZAKα and ZAKβ in which ZAKβ antagonizes ZAKα-induced apoptosis and hypertrophy of the heart. This study aims to test the hypothesis of whether ZAKα and ZAKβ are involved in the damaging effects of ox-LDL in the cardiomyoblast. Cardiomyoblast cells H9c2 were treated with different concentrations of ox-LDL. Cell viability and apoptosis were measured by MTT and TUNEL assay, respectively. Western blot was used to detect apoptosis, hypertrophy, and pro-survival signaling proteins. Plasmid transfection, pharmacological inhibition with D2825, and siRNA transfection were utilized to upregulate or downregulate ZAKβ, respectively. Ox-LDL concentration-dependently reduces the viability and expression of several pro-survival proteins, such as phospho-PI3K, phospho-Akt, and Bcl-xL. Furthermore, ox-LDL increases cleaved caspase-3, cleaved caspase-9 as indicators of apoptosis and increases B-type natriuretic peptide (BNP) as an indicator of hypertrophy. Overexpression of ZAKβ by plasmid transfection attenuates apoptosis and prevents upregulation of BNP. Importantly, these effects were abolished by inhibiting ZAKβ either by D2825 or siZAKβ application. Our results suggest that ZAKβ upregulation in response to ox-LDL treatment confers protective effects on cardiomyoblast.

Influence of Genetic Polymorphisms on Clinical Outcomes of Glatiramer Acetate in Multiple Sclerosis Patients

Multiple sclerosis (MS) is a chronic, inflammatory, demyelinating disease of autoimmune origin, in which inflammation and demyelination lead to neurodegeneration and progressive disability. Treatment is aimed at slowing down the course of the disease and mitigating its symptoms. One of the first-line treatments used in patients with MS is glatiramer acetate (GA). However, in clinical practice, a response rate of between 30% and 55% is observed. This variability in the effectiveness of the medication may be influenced by genetic factors such as polymorphisms in the genes involved in the pathogenesis of MS. Therefore, this review assesses the impact of genetic variants on the response to GA therapy in patients diagnosed with MS. The results suggest that a relationship exists between the effectiveness of the treatment with GA and the presence of polymorphisms in the following genes: CD86, CLEC16A, CTSS, EOMES, MBP, FAS, TRBC1, IL1R1, IL12RB2, IL22RA2, PTPRT, PVT1, ALOX5AP, MAGI2, ZAK, RFPL3, UVRAG, SLC1A4, and HLA-DRB1*1501. Consequently, the identification of polymorphisms in these genes can be used in the future as a predictive marker of the response to GA treatment in patients diagnosed with MS. Nevertheless, there is a lack of evidence for this and more validation studies need to be conducted to apply this information to clinical practice.

Hearing Function: Identification of New Candidate Genes Further Explaining the Complexity of This Sensory Ability

To date, the knowledge of the genetic determinants behind the modulation of hearing ability is relatively limited. To investigate this trait, we performed Genome-Wide Association Study (GWAS) meta-analysis using genotype and audiometric data (hearing thresholds at 0.25, 0.5, 1, 2, 4, and 8 kHz, and pure-tone averages of thresholds at low, medium, and high frequencies) collected in nine cohorts from Europe, South-Eastern USA, Caucasus, and Central Asia, for an overall number of ~9000 subjects. Three hundred seventy-five genes across all nine analyses were tagged by single nucleotide polymorphisms (SNPs) reaching a suggestive p-value (p < 10⁻⁵). Amongst these, 15 were successfully replicated using a gene-based approach in the independent Italian Salus in the Apulia cohort (n = 1774) at the nominal significance threshold (p < 0.05). In addition, the expression level of the replicated genes was assessed in published human and mouse inner ear datasets. Considering expression patterns in humans and mice, eleven genes were considered particularly promising candidates for the hearing function: BNIP3L, ELP5, MAP3K20, MATN2, MTMR7, MYO1E, PCNT, R3HDM1, SLC9A9, TGFB2, and YTHDC2. These findings represent a further contribution to our understanding of the genetic basis of hearing function and its related diseases.

Ribosomal stress-surveillance: three pathways is a magic number

Cells rely on stress response pathways to uphold cellular homeostasis and limit the negative effects of harmful environmental stimuli. The stress- and mitogen-activated protein (MAP) kinases, p38 and JNK, are at the nexus of numerous stress responses, among these the ribotoxic stress response (RSR). Ribosomal impairment is detrimental to cell function as it disrupts protein synthesis, increase inflammatory signaling and, if unresolved, lead to cell death. In this review, we offer a general overview of the three main translation surveillance pathways; the RSR, Ribosome-associated Quality Control (RQC) and the Integrated Stress Response (ISR). We highlight recent advances made in defining activation mechanisms for these pathways and discuss their commonalities and differences. Finally, we reflect on the physiological role of the RSR and consider the therapeutic potential of targeting the sensing kinase ZAKα for treatment of ribotoxin exposure.

Selective Activation of ZAK β Expression by 3-Hydroxy-2-Phenylchromone Inhibits Human Osteosarcoma Cells and Triggers Apoptosis via JNK Activation

Although various advancements in radical surgery and neoadjuvant chemotherapy have been developed in treating osteosarcoma (OS), their clinical prognosis remains poor. A synthetic chemical compound, 3-hydroxylflavone, that is reported to regulate ROS production is known to inhibit human bone osteosarcoma cells. However, its role and mechanism in human OS cells remains unclear. In this study, we have determined the potential of 3-Hydroxy-2-phenylchromone (3-HF) against OS using human osteosarcoma (HOS) cells. Our previous studies showed that Zipper sterile-alpha-motif kinase (ZAK), a kinase member of the MAP3K family, was involved in various cellular events such as cell proliferation and cell apoptosis, and encoded two transcriptional variants, ZAKα and β. In this study, we show that 3-HF induces the expression of ZAK and thereby enhances cellular apoptosis. Using gain of function and loss of function studies, we have demonstrated that ZAK activation by 3-HF in OS cells is confined to a ZAKβ form that presumably plays a leading role in triggering ZAKα expression, resulting in an aggravated cancer apoptosis. Our results also validate ZAKβ as the predominant form of ZAK to drive the anticancer mechanism in HOS cells.

Design, Synthesis, and Structure-Activity Relationships of 1,2,3-Triazole Benzenesulfonamides as New Selective Leucine-Zipper and Sterile-α Motif Kinase (ZAK) Inhibitors

ZAK is a new promising target for discovery of drugs with activity against antihypertrophic cardiomyopathy (HCM). A series of 1,2,3-triazole benzenesulfonamides were designed and synthesized as selective ZAK inhibitors. One of these compounds, 6p binds tightly to ZAK protein (Kd = 8.0 nM) and potently suppresses the kinase function of ZAK with single-digit nM (IC50 = 4.0 nM) and exhibits excellent selectivity in a KINOMEscan screening platform against a panel of 403 wild-type kinases. This compound dose dependently blocks p38/GATA-4 and JNK/c-Jun signaling and demonstrates promising in vivo anti-HCM efficacy upon oral administration in a spontaneous hypertensive rat (SHR) model. Compound 6p may serve as a lead compound for new anti-HCM drug discovery.

MicroRNA gga-miR-200a-3p modulates immune response via MAPK signaling pathway in chicken afflicted with necrotic enteritis

MicroRNAs (miRNAs) are small non-coding RNAs that contribute to host immune response as post-transcriptional regulation. The current study investigated the biological role of the chicken (Gallus gallus) microRNA-200a-3p (gga-miR-200a-3p), using 2 necrotic enteritis (NE) afflicted genetically disparate chicken lines, 6.3 and 7.2, as well as the mechanisms underlying the fundamental signaling pathways in chicken. The expression of gga-miR-200a-3p in the intestinal mucosal layer of NE-induced chickens, was found to be upregulated during NE infection in the disease-susceptible chicken line 7.2. To validate the target genes, we performed an overexpression analysis of gga-miR-200a-3p using chemically synthesized oligonucleotides identical to gga-miR-200a-3p, reporter gene analysis including luciferase reporter assay, and a dual fluorescence reporter assay in cultured HD11 chicken macrophage cell lines. Gga-miR-200a-3p was observed to be a direct transcriptional repressor of ZAK, MAP2K4, and TGFβ2 that are involved in mitogen-activated protein kinase (MAPK) pathway by targeting the 3′-UTR of their transcripts. Besides, gga-miR-200a-3p may indirectly affect the expression of protein kinases including p38 and ERK1/2 at both transcriptional and translational levels, suggesting that this miRNA may function as an important regulator of the MAPK signaling pathway. Proinflammatory cytokines consisting of IL-1β, IFN-γ, IL-12p40, IL-17A, and LITAF belonging to Th1 and Th17-type cytokines, were upregulated upon gga-miR-200a-3p overexpression. These findings have enhanced our knowledge of the immune function of gga-miR-200a-3p mediating the chicken immune response via regulation of the MAPK signaling pathway and indicate that this miRNA may serve as an important biomarker of diseases in domestic animals.

Therapeutic potential of targeting mixed lineage kinases in cancer and inflammation

Dysregulation of intracellular signaling pathways is a key attribute of diseases associated with chronic inflammation, including cancer. Mitogen activated protein kinases have emerged as critical conduits of intracellular signal transmission, yet due to their ubiquitous roles in cellular processes, their direct inhibition may lead to undesired effects, thus limiting their usefulness as therapeutic targets. Mixed lineage kinases (MLKs) are mitogen-activated protein kinase kinase kinases (MAP3Ks) that interact with scaffolding proteins and function upstream of p38, JNK, ERK, and NF-kappaB to mediate diverse cellular signals. Studies involving gene silencing, genetically engineered mouse models, and small molecule inhibitors suggest that MLKs are critical in tumor progression as well as in inflammatory processes. Recent advances indicate that they may be useful targets in some types of cancer and in diseases driven by chronic inflammation including neurodegenerative diseases and metabolic diseases such as nonalcoholic steatohepatitis. This review describes existing MLK inhibitors, the roles of MLKs in various aspects of tumor progression and in the control of inflammatory processes, and the potential for therapeutic targeting of MLKs.

Cardioembolic Ischemic Stroke Gene Expression Fingerprint in Blood: a Systematic Review and Verification Analysis

An accurate etiological classification is key to optimize secondary prevention after ischemic stroke, but the cause remains undetermined in one third of patients. Several studies pointed out the usefulness of circulating gene expression markers to discriminate cardioembolic (CE) strokes, mainly due to atrial fibrillation (AF), while only exploring them in small cohorts. A systematic review of studies analyzing high-throughput gene expression in blood samples to discriminate CE strokes was performed. Significantly dysregulated genes were considered as candidates, and a selection of them was validated by RT-qPCR in 100 patients with defined CE or atherothrombotic (LAA) stroke etiology. Longitudinal performance was evaluated in 12 patients at three time points. Their usefulness as biomarkers for AF was tested in 120 cryptogenic strokes and 100 individuals at high-risk for stroke. Three published studies plus three unpublished datasets were considered for candidate selection. Sixty-seven genes were found dysregulated in CE strokes. CREM, PELI1, and ZAK were verified to be up-regulated in CE vs LAA (p = 0.010, p = 0.003, p < 0.001, respectively), without changes in their expression within the first 24 h after stroke onset. The combined up-regulation of these three biomarkers increased the probability of suffering from CE stroke by 23-fold. In cryptogenic strokes with subsequent AF detection, PELI1 and CREM showed overexpression (p = 0.017, p = 0.059, respectively), whereas in high-risk asymptomatic populations, all three genes showed potential to detect AF (p = 0.007, p = 0.007, p = 0.015). The proved discriminatory capacity of these gene expression markers to detect cardioembolism even in cryptogenic strokes and asymptomatic high-risk populations might bring up their use as biomarkers.

Studies of pharmacokinetics in beagle dogs and drug-drug interaction potential of a novel selective ZAK inhibitor 3h for hypertrophic cardiomyopathy treatment

Overexpression of leucine-zipper and sterile-α motif kinase (ZAK) in heart has been closely associated with the development of hypertrophic cardiomyopathy (HCM). N-(3-(1H-pyrazolo[3,4-b]pyridin-5-yl)ethynyl) benzene-sulfonamides, novel highly selective ZAK inhibitors, had exhibited reasonable orally therapeutic effects on HCM in spontaneous hypertensive rat models. In the present study, a rapid and sensitive HPLC-MS/MS method for determining ZAK inhibitor 3h in beagle dog plasma was developed and validated. Meanwhile, the pharmacokinetics in beagle dog and drug-drug interaction potential of 3h had been conducted. The pharmacokinetic results showed that the absolute oral bioavailability for 3h in beagle dogs was determined to be 61.9%, which was significantly higher than that in the previous determination in Spragur-Dawley rats (F = 20%). The Cytochrome P450 enzymes and P-glycoprotein mediated drug-drug interactions by 3h were also investigated using dog and human liver microsomes and Caco-2 cells. The results demonstrated that only CYP2C9 was obviously inhibited (IC₅₀ = 1.66 μM). Besides, 3h could significantly decrease digoxin efflux ratio in Caco-2 experiments in a dose-dependent manner (IC₅₀ = 13.3 μM). Considering 3h strongly suppressed the ZAK kinase activity with an IC₅₀ of 3.3 nM, there are significantly differences between this IC₅₀ value for ZAK inhibition and the present determinations of IC₅₀ values. In general, the clinical drug-drug interaction potential for 3h could be well monitored during the treatment of HCM.

Novel Insights into MSK1 Phosphorylation by MRKβ in Intracerebral Hemorrhage-Induced Neuronal Apoptosis

Neuronal apoptosis is regarded as one of the most important pathophysiological changes of intracerebral hemorrhagic (ICH) stroke—a major public health problem that leads to high mortality rates and functional dependency. Mitogen-and stress-activated kinase (MSK) 1 is implicated in various biological functions in different cell types, including proliferation, tumorigenesis and responses to stress. Our previous study showed that MSK1 phosphorylation (p-MSK1) is related to the regulation of LPS-induced astrocytic inflammation, and possibly acts as a negative regulator of inflammation. In this study, we identified a specific interaction between MSK1 and MRKβ (MLK-related kinase)—a member of the MAPK pathway—during neuronal apoptosis. In an ICH rat model, western blotting and immunohistochemical analysis revealed that both MRKβ and phosphorylation of MSK1 (p-MSK1 Ser376) were significantly upregulated in cells surrounding the hematoma. Triple-immunofluorescent labeling demonstrated the co-localization of MRKβ and p-MSK1 in neurons, but not astrocytes. Furthermore, MRKβ was partially transported into the nucleus, and interacted with p-MSK1 in hemin-treated neurons. Immunoprecipitation showed that MRKβ and p-MSK1 exhibited an enhanced interaction during the pathophysiology process. Utilizing small interfering RNAs to knockdown MRKβ or MSK1, we verified that MSK1 Ser376 is a phosphorylation site targeted by MRKβ. We also observed that the phosphorylation of NF-κB p65 at Ser276 was mediated by the MRKβ-p-MSK1 complex. Furthermore, it was found that the neuronal apoptosis marker, active caspase-3, was co-localized with MRKβ and p-MSK1. In addition, flow cytometry analysis revealed that knockdown of MRKβ or MSK1 specifically resulted in increased neuronal apoptosis, which suggested that the MRKβ-p-MSK1 complex might exert a neuroprotective function against ICH-induced neuronal apoptosis. Taken together, our data suggest that MRKβ translocated into the nucleus and phosphorylated MSK1 to protect neurons via phosphorylation of p65—a subunit of nuclear factor κB.

ERβ targets ZAK and attenuates cellular hypertrophy via SUMO-1 modification in H9c2 cells

Aberrant expression of leucine zipper- and sterile ɑ motif-containing kinase (ZAK) observed in pathological human myocardial tissue is associated with the progression and elevation of hypertrophy. Our previous reports have correlated high levels of estrogen (E2) and abundant estrogen receptor (ER) α with a low incidence of pathological cardiac-hypertrophy and heart failure in the premenopause female population. However, the effect of elevated ERβ expression is not well known yet. Therefore, in this study, we have analyzed the cardioprotective effects and mechanisms of E2 and/or ERβ against ZAK overexpression-induced cellular hypertrophy. We have used transient transfection to overexpress ERβ into the ZAK tet-on H9c2 cells that harbor the doxycycline-inducible ZAK plasmid. The results show that ZAK overexpression in H9c2 cells resulted in hypertrophic effects, which was correlated with the upregulation of p-JNK and p-p38 MAPKs and their downstream transcription factors c-Jun and GATA-4. However, ERβ and E2 with ERβ overexpressions totally suppressed the effects of ZAK overexpression and inhibited the levels of p-JNK, p-p38, c-Jun, and GATA-4 effectively. Our results further reveal that ERβ directly binds with ZAK under normal conditions; however, ZAK overexpression reduced the association of ZAK-ERβ. Interestingly, increase in ERβ and E2 along with ERβ overexpression both enhanced the binding strengths of ERβ and ZAK and reduced the ZAK protein level. ERβ overexpression also suppressed the E3 ligase-casitas B-lineage lymphoma (CBL) and attenuated CBL-phosphoinositide 3-kinase (PI3K) protein association to prevent PI3K protein degradation. Moreover, ERβ and/or E2 blocked ZAK nuclear translocation via the inhibition of small ubiquitin-like modifier (SUMO)-1 modification. Taken together, our results further suggest that ERβ overexpression strongly suppresses ZAK-induced cellular hypertrophy and myocardial damage.

Overexpression of ZAKβ in human osteosarcoma cells enhances ZAKα expression, resulting in a synergistic apoptotic effect

ZAK is a novel mixed lineage kinase-like protein that contains a leucine-zipper and a sterile-alpha motif as a protein-protein interaction domain, and it is located in the cytoplasm. There are 2 alternatively spliced forms of ZAK: ZAKα and ZAKβ. Previous studies showed that ZAKα is involved in various cell processes, including cell proliferation, cell differentiation, and cardiac hypertrophy, but the molecular mechanism of ZAKβ is not yet known. In a recent study in our laboratory, we found that ZAKβ can ameliorate the apoptotic effect induced by ZAKα in H9c2 cells. We further hypothesized that ZAKβ could also improve the apoptotic effect induced by ZAKα in human osteosarcoma cells. The results of this study show that ZAKβ can induce apoptosis and decrease cell viability similar to the effects of ZAKα. Interestingly, our ZAKα-specific inhibitor assay shows that the expression of ZAKβ is highly dependent on ZAKα expression. However, ZAKβ expression effectively induces ZAKα expression and results in synergistic enhancement of apoptosis in human osteosarcoma cells. Furthermore, co-immunoprecipitation results revealed that ZAKα can directly interact with ZAKβ, and this interaction may contribute to the enhanced apoptotic effects.

SIGNIFICANCE OF THE STUDY

ZAK is a mixed lineage kinase involved in cell differentiation, proliferation, and hypertrophic growth. ZAKα isoform of ZAK is associated with tumorigenesis, but the function of ZAKβ is not yet known. In H9c2 cells, ZAKβ was found to ameliorate the apoptotic effect induced by ZAKα. However, in osteosarcoma cells, ZAKβ elevates the apoptotic effect induced by ZAKα. In this study, we show that similar to ZAKα, the ZAKβ induces apoptosis and decreases cell viability. Interestingly, the expression of ZAKβ is dependent on ZAKα expression, and ZAKβ further enhances ZAKα expression and results in synergistic enhancement of apoptosis in osteosarcoma cells.

Mixed lineage kinase ZAK promotes epithelial-mesenchymal transition in cancer progression

ZAK, a mixed lineage kinase, is often described as a positive or negative regulator of cell growth. We identified it as one of the top hits in our kinome cDNA screen for potent regulators of epithelial mesenchymal transition (EMT). Ectopic expression of ZAK promoted EMT phenotypes and apoptosis resistance in multiple epithelial cell lines, while having different impacts on cell growth in different cell lines. Conversely, depletion of ZAK in aggressive mesenchymal cancer cells reversed EMT phenotypes, increased sensitivity to conventional cytotoxic drugs, and attenuated bone metastasis potential, with little impact on primary tumor growth. Mechanistically, ZAK-mediated EMT is associated with activation of ZEB1 and suppression of epithelial splicing regulatory proteins (ESRPs), which results in a switch in CD44 expression from the epithelial CD44v8-9 isoform to the mesenchymal CD44s isoform. Of note, transcriptomic analysis showed that ZAK overexpression is significantly associated with poor survival in a number of human cancer types. Tissue microarray analysis on breast invasive carcinoma further supported that ZAK overexpression is an independent poor prognostic factor for overall survival in breast cancer. Through combination with ZAK, prognostic accuracy of other common clinicopathological markers in breast cancer is improved by up to 21%. Taken together, these results suggest that promoting EMT is the primary role for ZAK in cancer progression. They also highlight its potential as a biomarker to identify high-risk patients, and suggest its promise as a therapeutic target for inhibiting metastasis and overcoming drug resistance.

Novel genetic variants in the P38MAPK pathway gene ZAK and susceptibility to lung cancer

The P38MAPK pathway participates in regulating cell cycle, inflammation, development, cell death, cell differentiation, and tumorigenesis. Genetic variants of some genes in the P38MAPK pathway are reportedly associated with lung cancer risk. To substantiate this finding, we used six genome-wide association studies (GWASs) to comprehensively investigate the associations of 14 904 single nucleotide polymorphisms (SNPs) in 108 genes of this pathway with lung cancer risk. We identified six significant lung cancer risk-associated SNPs in two genes (CSNK2B and ZAK) after correction for multiple comparisons by a false discovery rate (FDR) <0.20. After removal of three CSNK2B SNPs that are located in the same locus previously reported by GWAS, we performed the LD analysis and found that rs3769201 and rs7604288 were in high LD. We then chose two independent representative SNPs of rs3769201 and rs722864 in ZAK for further analysis. We also expanded the analysis by including these two SNPs from additional GWAS datasets of Harvard University (984 cases and 970 controls) and deCODE (1319 cases and 26 380 controls). The overall effects of these two SNPs were assessed using all eight GWAS datasets (OR = 0.92, 95%CI = 0.89-0.95, and P = 1.03 × 10-5 for rs3769201; OR = 0.91, 95%CI = 0.88-0.95, and P = 2.03 × 10-6 for rs722864). Finally, we performed an expression quantitative trait loci (eQTL) analysis and found that these two SNPs were significantly associated with ZAK mRNA expression levels in lymphoblastoid cell lines. In conclusion, the ZAK rs3769201 and rs722864 may be functional susceptibility loci for lung cancer risk.

Doxorubicin induces ZAKα overexpression with a subsequent enhancement of apoptosis and attenuation of survivability in human osteosarcoma cells

Human osteosarcoma (OS) is a malignant cancer of the bone. It exhibits a characteristic malignant osteoblastic transformation and produces a diseased osteoid. A previous study demonstrated that doxorubicin (DOX) chemotherapy decreases human OS cell proliferation and might enhance the relative RNA expression of ZAK. However, the impact of ZAKα overexpression on the OS cell proliferation that is inhibited by DOX and the molecular mechanism underlying this effect are not yet known. ZAK is a protein kinase of the MAPKKK family and functions to promote apoptosis. In our study, we found that ZAKα overexpression induced an apoptotic effect in human OS cells. Treatment of human OS cells with DOX enhanced ZAKα expression and decreased cancer cell viability while increasing apoptosis of human OS cells. In the meantime, suppression of ZAKα expression using shRNA and inhibitor D1771 both suppressed the DOX therapeutic effect. These findings reveal a novel molecular mechanism underlying the DOX effect on human OS cells. Taken together, our findings demonstrate that ZAKα enhances the apoptotic effect and decreases cell viability in DOX-treated human OS cells.

Structure Based Design of N-(3-((1H-Pyrazolo[3,4-b]pyridin-5-yl)ethynyl)benzenesulfonamides as Selective Leucine-Zipper and Sterile-α Motif Kinase (ZAK) Inhibitors

A series of N-(3-((1H-pyrazolo[3,4-b]pyridin-5-yl)ethynyl)benzenesulfonamides were designed as the first class of highly selective ZAK inhibitors. The representative compound 3h strongly inhibits the kinase activity of ZAK with an IC50 of 3.3 nM and dose-dependently suppresses the activation of ZAK downstream signals in vitro and in vivo, while it is significantly less potent for the majority of 403 nonmutated kinases evaluated. Compound 3h also exhibits orally therapeutic effects on cardiac hypertrophy in a spontaneous hypertensive rat model.

Recessive mutations in the kinase ZAK cause a congenital myopathy with fibre type disproportion

Congenital myopathies define a heterogeneous group of neuromuscular diseases with neonatal or childhood hypotonia and muscle weakness. The genetic cause is still unknown in many patients, precluding genetic counselling and better understanding of the physiopathology. To identify novel genetic causes of congenital myopathies, exome sequencing was performed in three consanguineous families. We identified two homozygous frameshift mutations and a homozygous nonsense mutation in the mitogen-activated protein triple kinase ZAK. In total, six affected patients carry these mutations. Reverse transcription polymerase chain reaction and transcriptome analyses suggested nonsense mRNA decay as a main impact of mutations. The patients demonstrated a generalized slowly progressive muscle weakness accompanied by decreased vital capacities. A combination of proximal contractures with distal joint hyperlaxity is a distinct feature in one family. The low endurance and compound muscle action potential amplitude were strongly ameliorated on treatment with anticholinesterase inhibitor in another patient. Common histopathological features encompassed fibre size variation, predominance of type 1 fibre and centralized nuclei. A peculiar subsarcolemmal accumulation of mitochondria pointing towards the centre of the fibre was a novel histological hallmark in one family. These findings will improve the molecular diagnosis of congenital myopathies and implicate the mitogen-activated protein kinase (MAPK) signalling as a novel pathway altered in these rare myopathies.

A Requirement for ZAK Kinase Activity in Canonical TGF-β Signaling

The sterile alpha motif and leucine zipper containing kinase ZAK (AZK, MLT, MLK7), is a MAPK-kinase kinase (MKKK). Like most MAPKKKs which are known to activate the c-Jun. amino-terminal kinase (JNK) pathway, ZAK has been shown to participate in the transduction of Transforming growth factor-β (TGF-β)-mediated non-canonical signaling. A role for ZAK in SMAD-dependent, canonical TGF-β signaling has not been previously appreciated. Using a combination of functional genomics and biochemical techniques, we demonstrate that ZAK regulates canonical TGFβRI/II signaling in lung and breast cancer cell lines and may serve as a key node in the regulation of TGFBR kinase activity. Remarkably, we demonstrate that siRNA mediated depletion of ZAK strongly inhibited TGF-β dependent SMAD2/3 activation and subsequent promoter activation (SMAD binding element driven luciferase expression; SBE4-Luc). A ZAK specific inhibitor (DHP-2), dose-dependently activated the bioluminescent TGFBR-kinase activity reporter (BTR), blocked TGF-β induced SMAD2/3 phosphorylation and SBE4-Luc activation and cancer cell-invasion. In aggregate, these findings identify a novel role for the ZAK kinase in canonical TGF-β signaling and an invasive cancer cell phenotype thus providing a novel target for TGF-β inhibition.

Structure of the Human Protein Kinase ZAK in Complex with Vemurafenib

The mixed lineage kinase ZAK is a key regulator of the MAPK pathway mediating cell survival and inflammatory response. ZAK is targeted by several clinically approved kinase inhibitors, and inhibition of ZAK has been reported to protect from doxorubicin-induced cardiomyopathy. On the other hand, unintended targeting of ZAK has been linked to severe adverse effects such as the development of cutaneous squamous cell carcinoma. Therefore, both specific inhibitors of ZAK, as well as anticancer drugs lacking off-target activity against ZAK, may provide therapeutic benefit. Here, we report the first crystal structure of ZAK in complex with the B-RAF inhibitor vemurafenib. The cocrystal structure displayed a number of ZAK-specific features including a highly distorted P loop conformation enabling rational inhibitor design. Positional scanning peptide library analysis revealed a unique substrate specificity of the ZAK kinase including unprecedented preferences for histidine residues at positions -1 and +2 relative to the phosphoacceptor site. In addition, we screened a library of clinical kinase inhibitors identifying several inhibitors that potently inhibit ZAK, demonstrating that this kinase is commonly mistargeted by currently used anticancer drugs.

Pharmacological Inhibition of the Protein Kinase MRK/ZAK Radiosensitizes Medulloblastoma

Medulloblastoma is a cerebellar tumor and the most common pediatric brain malignancy. Radiotherapy is part of the standard care for this tumor, but its effectiveness is accompanied by significant neurocognitive sequelae due to the deleterious effects of radiation on the developing brain. We have previously shown that the protein kinase MRK/ZAK protects tumor cells from radiation-induced cell death by regulating cell-cycle arrest after ionizing radiation. Here, we show that siRNA-mediated MRK depletion sensitizes medulloblastoma primary cells to radiation. We have, therefore, designed and tested a specific small molecule inhibitor of MRK, M443, which binds to MRK in an irreversible fashion and inhibits its activity. We found that M443 strongly radiosensitizes UW228 medulloblastoma cells as well as UI226 patient-derived primary cells, whereas it does not affect the response to radiation of normal brain cells. M443 also inhibits radiation-induced activation of both p38 and Chk2, two proteins that act downstream of MRK and are involved in DNA damage-induced cell-cycle arrest. Importantly, in an animal model of medulloblastoma that employs orthotopic implantation of primary patient-derived UI226 cells in nude mice, M443 in combination with radiation achieved a synergistic increase in survival. We hypothesize that combining radiotherapy with M443 will allow us to lower the radiation dose while maintaining therapeutic efficacy, thereby minimizing radiation-induced side effects. Mol Cancer Ther; 15(8); 1799-808. ©2016 AACR.

MLK3 Signaling in Cancer Invasion

Mixed-lineage kinase 3 (MLK3) was first cloned in 1994; however, only in the past decade has MLK3 become recognized as a player in oncogenic signaling. MLK3 is a mitogen-activated protein kinase kinase kinase (MAP3K) that mediates signals from several cell surface receptors including receptor tyrosine kinases (RTKs), chemokine receptors, and cytokine receptors. Once activated, MLK3 transduces signals to multiple downstream pathways, primarily to c-Jun terminal kinase (JNK) MAPK, as well as to extracellular-signal-regulated kinase (ERK) MAPK, P38 MAPK, and NF-κB, resulting in both transcriptional and post-translational regulation of multiple effector proteins. In several types of cancer, MLK3 signaling is implicated in promoting cell proliferation, as well as driving cell migration, invasion and metastasis.

Exome sequencing and CRISPR/Cas genome editing identify mutations of ZAK as a cause of limb defects in humans and mice

The CRISPR/Cas technology enables targeted genome editing and the rapid generation of transgenic animal models for the study of human genetic disorders. Here we describe an autosomal recessive human disease in two unrelated families characterized by a split-foot defect, nail abnormalities of the hands, and hearing loss, due to mutations disrupting the SAM domain of the protein kinase ZAK. ZAK is a member of the MAPKKK family with no known role in limb development. We show that Zak is expressed in the developing limbs and that a CRISPR/Cas-mediated knockout of the two Zak isoforms is embryonically lethal in mice. In contrast, a deletion of the SAM domain induces a complex hindlimb defect associated with down-regulation of Trp63, a known split-hand/split-foot malformation disease gene. Our results identify ZAK as a key player in mammalian limb patterning and demonstrate the rapid utility of CRISPR/Cas genome editing to assign causality to human mutations in the mouse in <10 wk.

The MAP3K ZAK, a novel modulator of ERK-dependent migration, is upregulated in colorectal cancer

Often described as a mediator of cell cycle arrest or as a pro-apoptotic factor in stressful conditions, the MAP3K ZAK (Sterile alpha motif and leucine zipper-containing kinase) has also been proven to positively regulate epidermal growth factor receptor (EGFR) and WNT signaling pathways, cancer cell proliferation and cellular neoplastic transformation. Here, we show that both isoforms of ZAK, ZAK-α and ZAK-β are key factors in cancer cell migration. While ZAK depletion reduced cell motility of HeLa and HCT116 cells, its overexpression triggered the activation of all three mitogen-activated protein kinases (MAPKs), extracellular signal-regulated kinase (ERK), c-JUN N-terminal kinase (JNK) and p38, as well as an increase in cell motion. On the contrary, the kinase-dead mutants, ZAK-α K45M and ZAK-β K45M, were not able to provoke such events, and instead exerted a dominant-negative effect on MAPK activation and cell migration. Pharmacological inhibition of ZAK by nilotinib, preventing ZAK-autophosphorylation and thereby auto-activation, led to the same results. Activated by epidermal growth factor (EGF), we further showed that ZAK constitutes an essential element of the EGF/ERK-dependent cell migration pathway. Using public transcriptomic databases and tissue microarrays, we finally established that, as strong factors of the EGFR signaling pathway, ZAK-α and/or ZAK-β transcripts and protein(s) are frequently upregulated in colorectal adenoma and carcinoma patients. Notably, gene set enrichment analysis disclosed a significant correlation between ZAK+ colorectal premalignant lesions and gene sets belonging to the MAPK/ERK and motility-related signaling pathways of the reactome database, strongly suggesting that ZAK induces such pro-tumoral reaction cascades in human cancers.

ZAK induces cardiomyocyte hypertrophy and brain natriuretic peptide expression via p38/JNK signaling and GATA4/c-Jun transcriptional factor activation

Cardiomyocyte hypertrophy is an adaptive response of heart to various stress conditions. During the period of stress accumulation, transition from physiological hypertrophy to pathological hypertrophy results in the promotion of heart failure. Our previous studies found that ZAK, a sterile alpha motif and leucine zipper containing kinase, was highly expressed in infarcted human hearts and demonstrated that overexpression of ZAK induced cardiac hypertrophy. This study evaluates, cellular events associated with the expression of two doxycycline (Dox) inducible Tet-on ZAK expression systems, a Tet-on ZAK WT (wild-type), and a Tet-on ZAK DN (mutant, Dominant-negative form) in H9c2 myoblast cells; Tet-on ZAK WT was found to increase cell size and hypertrophic marker BNP in a dose-dependent manner. To ascertain the mechanism of ZAK-mediated hypertrophy, expression analysis with various inhibitors of the related upstream and downstream proteins was performed. Tet-on ZAK WT expression triggered the p38 and JNK pathway and also activated the expression and nuclear translocation of p-GATA4 and p-c-Jun transcription factors, without the involvement of p-ERK or NFATc3. However, Tet-on ZAK DN showed no effect on the p38 and JNK signaling cascade. The results showed that the inhibitors of JNK1/2 and p38 significantly suppressed ZAK-induced BNP expression. The results show the role of ZAK and/or the ZAK downstream events such as JNK and p38 phosphorylation, c-Jun, and GATA-4 nuclear translocation in cardiac hypertrophy. ZAK and/or the ZAK downstream p38, and JNK pathway could therefore be potential targets to ameliorate cardiac hypertrophy symptoms in ZAK-overexpressed patients.

Long non-coding RNA URHC regulates cell proliferation and apoptosis via ZAK through the ERK/MAPK signaling pathway in hepatocellular carcinoma

Long non-coding RNAs (lncRNAs) have previously been implicated in human disease states, especially cancer. Although the aberrant expression of lncRNAs has been observed in cancer, the biological functions and molecular mechanisms underlying aberrantly expressed lncRNAs in hepatocellular carcinoma (HCC) have not been widely established. In the present study, we investigated a novel lncRNA, termed URHC (up-regulated in hepatocellular carcinoma), and evaluated its role in the progression of HCC. Expression profiling using a lncRNA microarray revealed that URHC was highly expressed in 3 HCC cell lines compared to normal hepatocytes. Quantitative real-time polymerase chain reaction (qRT-PCR) analyses confirmed that URHC expression was increased in hepatoma cells and HCC tissues. Moreover, using qRT-PCR, we confirmed that URHC expression was up-regulated in 30 HCC cases (57.7%) and that its higher expression was correlated with poor overall survival. We further demonstrated that URHC inhibition reduced cell proliferation and promoted apoptosis. We hypothesize that URHC may function by regulating the sterile alpha motif and leucine zipper containing kinase AZK (ZAK) gene, which is located near URHC on the same chromosome. We found that ZAK mRNA levels were down-regulated in HCC tissues and the expression levels of ZAK were negatively correlated with those of URHC in the above HCC tissues. Next, we confirmed that URHC down-regulated ZAK, which is involved in URHC-mediated cell proliferation and apoptosis. Furthermore, ERK/MAPK pathway inactivation partially accounted for URHC-ZAK-induced cell growth and apoptosis. Thus, we concluded that high URHC expression can promote cell proliferation and inhibit apoptosis by repressing ZAK expression through inactivation of the ERK/MAPK pathway. These findings may provide a novel mechanism and therapeutic targets for the treatment of HCC.

Integrated exome and transcriptome sequencing reveals ZAK isoform usage in gastric cancer

Gastric cancer is the second leading cause of worldwide cancer mortality, yet the underlying genomic alterations remain poorly understood. Here we perform exome and transcriptome sequencing and SNP array assays to characterize 51 primary gastric tumours and 32 cell lines. Meta-analysis of exome data and previously published data sets reveals 24 significantly mutated genes in microsatellite stable (MSS) tumours and 16 in microsatellite instable (MSI) tumours. Over half the patients in our collection could potentially benefit from targeted therapies. We identify 55 splice site mutations accompanied by aberrant splicing products, in addition to mutation-independent differential isoform usage in tumours. ZAK kinase isoform TV1 is preferentially upregulated in gastric tumours and cell lines relative to normal samples. This pattern is also observed in colorectal, bladder and breast cancers. Overexpression of this particular isoform activates multiple cancer-related transcription factor reporters, while depletion of ZAK in gastric cell lines inhibits proliferation. These results reveal the spectrum of genomic and transcriptomic alterations in gastric cancer, and identify isoform-specific oncogenic properties of ZAK.

The genetic basis of gastric cancer, the fourth most common cancer worldwide, remains poorly understood. Here, the authors sequence and analyse the exomes and transcriptomes of primary gastric tumours and cell lines, and identify a ZAK kinase isoform that may have an oncogenic role in gastric cancer.

Searching for genomic region of high-fat diet-induced type 2 diabetes in mouse chromosome 2 by analysis of congenic strains

SMXA-5 mice are a high-fat diet-induced type 2 diabetes animal model established from non-diabetic SM/J and A/J mice. By using F2 intercross mice between SMXA-5 and SM/J mice under feeding with a high-fat diet, we previously mapped a major diabetogenic QTL (T2dm2sa) on chromosome 2. We then produced the congenic strain (SM.A-T2dm2sa (R0), 20.8–163.0 Mb) and demonstrated that the A/J allele of T2dm2sa impaired glucose tolerance and increased body weight and body mass index in the congenic strain compared to SM/J mice. We also showed that the combination of T2dm2sa and other diabetogenic loci was needed to develop the high-fat diet-induced type 2 diabetes. In this study, to narrow the potential genomic region containing the gene(s) responsible for T2dm2sa, we constructed R1 and R2 congenic strains. Both R1 (69.6–163.0 Mb) and R2 (20.8–128.2 Mb) congenic mice exhibited increases in body weight and abdominal fat weight and impaired glucose tolerance compared to SM/J mice. The R1 and R2 congenic analyses strongly suggested that the responsible genes existed in the overlapping genomic interval (69.6–128.2 Mb) between R1 and R2. In addition, studies using the newly established R1A congenic strain showed that the narrowed genomic region (69.6–75.4 Mb) affected not only obesity but also glucose tolerance. To search for candidate genes within the R1A genomic region, we performed exome sequencing analysis between SM/J and A/J mice and extracted 4 genes (Itga6, Zak, Gpr155, and Mtx2) with non-synonymous coding SNPs. These four genes might be candidate genes for type 2 diabetes caused by gene-gene interactions. This study indicated that one of the genes responsible for high-fat diet-induced diabetes exists in the 5.8 Mb genomic interval on mouse chromosome 2.

An integrative analysis of colon cancer identifies an essential function for PRPF6 in tumor growth

The spliceosome machinery is composed of multimeric protein complexes that generate a diverse repertoire of mRNA. Here, Adler et al. discover that PRPF6, a member of the tri-snRNP spliceosome complex, drives cancer proliferation. Inhibition of PRPF6 and other tri-snRNP complex proteins selectively abrogated growth in cancer cells with high tri-snRNP levels. Reducing PRPF6 altered the splicing of a discrete number of genes, including an oncogenic isoform of the ZAK kinase. This study identifies an essential role for PRPF6 in cancer via splicing of distinct growth-related gene products.

The spliceosome machinery is composed of multimeric protein complexes that generate a diverse repertoire of mRNA through coordinated splicing of heteronuclear RNAs. While somatic mutations in spliceosome components have been discovered in several cancer types, the molecular bases and consequences of spliceosome aberrations in cancer are poorly understood. Here we report for the first time that PRPF6, a member of the tri-snRNP (small ribonucleoprotein) spliceosome complex, drives cancer proliferation by preferential splicing of genes associated with growth regulation. Inhibition of PRPF6 and other tri-snRNP complex proteins, but not other snRNP spliceosome complexes, selectively abrogated growth in cancer cells with high tri-snRNP levels. High-resolution transcriptome analyses revealed that reduced PRPF6 alters the constitutive and alternative splicing of a discrete number of genes, including an oncogenic isoform of the ZAK kinase. These findings implicate an essential role for PRPF6 in cancer via splicing of distinct growth-related gene products.

Identification of the ZAK-MKK4-JNK-TGFβ signaling pathway as a molecular target for novel synthetic iminoquinone anticancer compound BA-TPQ

Identification and validation of molecular targets are considered as key elements in new drug discovery and development. We have recently demonstrated that a novel synthetic iminoquinone analog, termed [7-(benzylamino)- 1,3,4,8-tetrahydropyrrolo [4,3, 2-de]quinolin-8(1H)-one] (BA-TPQ), has significant anti-breast cancer activity both in vitro and in vivo, but the underlying molecular mechanisms are not fully understood. Herein, we report the molecular studies for BA-TPQ's effects on JNK and its upstream and downstream signaling pathways. The compound up-regulates the JNK protein levels by increasing its phosphorylation and decreasing its polyubiquitination-mediated degradation. It activates ZAK at the MAPKKK level and MKK4 at the MAPKK level. It also up-regulates the TGFβ2 mRNA level, which can be abolished by the JNK-specific inhibitor SP600125, but not TGFβ pathway-specific inhibitor SD-208, indicating that both JNK and TGFβ signaling pathways are activated by BA-TPQ and that the JNK pathway activation precedes TGFβ activation. The pro-apoptotic and anti-growth effects of BA-TPQ are significantly blocked by both the JNK and TGFβ pathway inhibitors. In addition, BA-TPQ activates the ZAK-MKK4-JNK pathway in MCF7 cells, but not normal MCF10A cells, demonstrating its cancer-specific activities. In conclusion, our results demonstrate that BA-TPQ activates the ZAK-MKK4-JNK-TGFβ signaling cascade as a molecular target for its anticancer activity.

BRAF inhibitors suppress apoptosis through off-target inhibition of JNK signaling

Vemurafenib and dabrafenib selectively inhibit the v-Raf murine sarcoma viral oncogene homolog B1 (BRAF) kinase, resulting in high response rates and increased survival in melanoma. Approximately 22% of individuals treated with vemurafenib develop cutaneous squamous cell carcinoma (cSCC) during therapy. The prevailing explanation for this is drug-induced paradoxical ERK activation, resulting in hyperproliferation. Here we show an unexpected and novel effect of vemurafenib/PLX4720 in suppressing apoptosis through the inhibition of multiple off-target kinases upstream of c-Jun N-terminal kinase (JNK), principally ZAK. JNK signaling is suppressed in multiple contexts, including in cSCC of vemurafenib-treated patients, as well as in mice. Expression of a mutant ZAK that cannot be inhibited reverses the suppression of JNK activation and apoptosis. Our results implicate suppression of JNK-dependent apoptosis as a significant, independent mechanism that cooperates with paradoxical ERK activation to induce cSCC, suggesting broad implications for understanding toxicities associated with BRAF inhibitors and for their use in combination therapies. DOI: http://dx.doi.org/10.7554/eLife.00969.001.

The MLK-related kinase (MRK) is a novel RhoC effector that mediates lysophosphatidic acid (LPA)-stimulated tumor cell invasion

The small GTPase RhoC is overexpressed in many invasive tumors and is essential for metastasis. Despite its high structural homology to RhoA, RhoC appears to perform functions that are different from those controlled by RhoA. The identity of the signaling components that are differentially regulated by these two GTPases is only beginning to emerge. Here, we show that the MAP3K protein MRK directly binds to the GTP-bound forms of both RhoA and RhoC in vitro. However, siRNA-mediated depletion of MRK in cells phenocopies depletion of RhoC, rather than that of RhoA. MRK depletion, like that of RhoC, inhibits LPA-stimulated cell invasion, while depletion of RhoA increases invasion. We also show that active MRK enhances LPA-stimulated invasion, further supporting a role for MRK in the regulation of invasion. Depletion of either RhoC or MRK causes sustained myosin light chain phosphorylation after LPA stimulation. In addition, activation of MRK causes a reduction in myosin light chain phosphorylation. In contrast, as expected, depletion of RhoA inhibits myosin light chain phosphorylation. We also present evidence that both RhoC and MRK are required for LPA-induced stimulation of the p38 and ERK MAP kinases. In conclusion, we have identified MRK as a novel RhoC effector that controls LPA-stimulated cell invasion at least in part by regulating myosin dynamics, ERK and p38.

Small molecule kinase inhibitors block the ZAK-dependent inflammatory effects of doxorubicin

The adverse side effects of doxorubicin, including cardiotoxicity and cancer treatment-related fatigue, have been associated with inflammatory cytokines, many of which are regulated by mitogen-activated protein kinases (MAPKs). ZAK is an upstream kinase of the MAPK cascade. Using mouse primary macrophages cultured from ZAK-deficient mice, we demonstrated that ZAK is required for the activation of JNK and p38 MAPK by doxorubicin. Nilotinib, ponatinib and sorafenib strongly suppressed doxorubicin-mediated phosphorylation of JNK and p38 MAPK. In addition, these small molecule kinase inhibitors blocked the expression of IL-1β, IL-6 and CXCL1 RNA and the production of these proteins. Co-administration of nilotinib and doxorubicin to mice decreased the expression of IL-1β RNA in the liver and suppressed the level of IL-6 protein in the serum compared with mice that were injected with doxorubicin alone. Therefore, by reducing the production of inflammatory mediators, the inhibitors identified in the current study may be useful in minimizing the side effects of doxorubicin and potentially other chemotherapeutic drugs.

Role of a DNA damage checkpoint pathway in ionizing radiation-induced glioblastoma cell migration and invasion

Ionizing radiation (IR) induces a DNA damage response that includes activation of cell cycle checkpoints, leading to cell cycle arrest. In addition, IR enhances cell invasiveness of glioblastoma cells, among other tumor cell types. Using RNA interference, we found that the protein kinase MRK, previously implicated in the DNA damage response to IR, also inhibits IR-induced cell migration and invasion of glioblastoma cells. We showed that MRK activation by IR requires the checkpoint protein Nbs1 and that Nbs1 is also required for IR-stimulated migration. In addition, we show that MRK acts upstream of Chk2 and that Chk2 is also required for IR-stimulated migration and invasion. Thus, we have identified Nbs1, MRK, and Chk2 as elements of a novel signaling pathway that mediates IR-stimulated cell migration and invasion. Interestingly, we found that inhibition of cell cycle progression, either with the CDK1/2 inhibitor CGP74514A or by downregulation of the CDC25A protein phosphatase, restores IR-induced migration and invasion in cells depleted of MRK or Chk2. These data indicate that cell cycle progression, at least in the context of IR, exerts a negative control on the invasive properties of glioblastoma cells and that checkpoint proteins mediate IR-induced invasive behavior by controlling cell cycle arrest.

The protein kinase MLTK regulates chondrogenesis by inducing the transcription factor Sox6

Sox9 acts together with Sox5 or Sox6 as a master regulator for chondrogenesis; however, the inter-relationship among these transcription factors remains unclear. Here, we show that the protein kinase MLTK plays an essential role in the onset of chondrogenesis through triggering the induction of Sox6 expression by Sox9. We find that knockdown of MLTK in Xenopus embryos results in drastic loss of craniofacial cartilages without defects in neural crest development. We also find that Sox6 is specifically induced during the onset of chondrogenesis, and that the Sox6 induction is inhibited by MLTK knockdown. Remarkably, Sox6 knockdown phenocopies MLTK knockdown. Moreover, we find that ectopic expression of MLTK induces Sox6 expression in a Sox9-dependent manner. Our data suggest that p38 and JNK pathways function downstream of MLTK during chondrogenesis. These results identify MLTK as a novel key regulator of chondrogenesis, and reveal its action mechanism in chondrocyte differentiation during embryonic development.

Ricin and Shiga toxins: effects on host cell signal transduction

Shiga toxins and ricin are potent inhibitors of protein synthesis. In addition to causing inhibition of protein synthesis, these toxins activate proinflammatory signaling cascades that may contribute to the severe diseases associated with toxin exposure. Treatment of cells with Shiga toxins and ricin have been shown to activate a number of signaling pathways including those associated with the ribotoxic stress response, Nuclear factor kappa B activation, inflammasome activation, the unfolded protein response, mTOR signaling, hemostasis, and retrograde trafficking. In this chapter, we review our current understanding of these signaling pathways as they pertain to intoxication by Shiga toxins and ricin.

Transient global cerebral ischemia induces up-regulation of MLTKα in hippocampal CA1 neurons

MLTK (mixed-lineage kinase-like mitogen-activated protein triple kinase) is a member of the mitogen-activated protein kinase family and functioned as a mitogen activated kinase kinase kinase. MLTKα, one of the alternatively spliced forms of MLTK, could activate the c-Jun N-terminal kinase pathway, which involved in cellular stress responses and apoptosis. But the role of MLTKα in neural apoptosis was still unclear. Here, we performed a transient global cerebral ischemia model (TGCI) in adult rats and detected the dynamic changes of MLTKα in hippocampal CA1 neurons and brain cortex. We found the MLTKα expression was increased shortly after TGCI and peaked after 8 h. In spatial distribution, MLTKα was widely located in neurons rather than astrocytes and microglia. Moreover, there was a concomitant up-regulation of active caspase-3. Taken together, we hypothesized the up-regulation of MLTKα played an essential role in the apoptosis of hippocampal CA1 neurons.

Transcriptional responses of host peripheral blood cells to tuberculosis infection

Host responses following exposure to Mycobacterium tuberculosis (TB) are complex and can significantly affect clinical outcome. These responses, which are largely mediated by complex immune mechanisms involving peripheral blood cells (PBCs) such as T-lymphocytes, NK cells and monocyte-derived macrophages, have not been fully characterized. We hypothesize that different clinical outcome following TB exposure will be uniquely reflected in host gene expression profiles, and expression profiling of PBCs can be used to discriminate between different TB infectious outcomes. In this study, microarray analysis was performed on PBCs from three TB groups (BCG-vaccinated, latent TB infection, and active TB infection) and a control healthy group. Supervised learning algorithms were used to identify signature genomic responses that differentiate among group samples. Gene Set Enrichment Analysis was used to determine sets of genes that were co-regulated. Multivariate permutation analysis (p < 0.01) gave 645 genes differentially expressed among the four groups, with both distinct and common patterns of gene expression observed for each group. A 127-probeset, representing 77 known genes, capable of accurately classifying samples into their respective groups was identified. In addition, 13 insulin-sensitive genes were found to be differentially regulated in all three TB infected groups, underscoring the functional association between insulin signaling pathway and TB infection.