GCK is essential to systemic inflammation and pattern recognition receptor signaling to JNK and p38

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.

The mycobacterial phosphatase PtpA regulates the expression of host genes and promotes cell proliferation

Mycobacterium tuberculosis PtpA is a secreted effector protein that dephosphorylates several proteins in the host cell cytoplasm, such as p-JNK, p-p38, and p-VPS33B, leading to suppression of host innate immunity. Here we show that, in addition, PtpA enters the nucleus of host cells and regulates the expression of host genes, some of which are known to be involved in host innate immunity or in cell proliferation and migration (such as GADD45A). PtpA can bind directly to the promoter region of GADD45A in vitro. Both phosphatase activity and DNA-binding ability of PtpA are important in suppressing host innate immune responses. Furthermore, PtpA-expressing Mycobacterium bovis BCG promotes proliferation and migration of human lung adenoma A549 cells in vitro and in a mouse xenograft model. Further research is needed to test whether mycobacteria, via PtpA, might affect cell proliferation or migration in humans.

Mycobacterium tuberculosis secretes a protein, PtpA, that dephosphorylates proteins in the host cell cytoplasm, weakening immune responses. Here, the authors show that PtpA also enters the nucleus, affects the expression of several host genes, and promotes proliferation and migration of a cancer cell line.

MST-4 and TRAF-6 expression in the peripheral blood mononuclear cells of patients with Graves' disease and its significance

BACKGROUND

MST-4 and TRAF-6 are involved in the regulation of inflammatory and immune responses. However, whether they participate in the pathogenesis of Graves' disease (GD) has not yet been reported. Therefore, the purpose of this study was to investigate the expression of MST-4 and TRAF-6 in the peripheral blood of patients with GD to understand their role in the pathogenesis of GD.

METHODS

Thirty newly diagnosed GD patients, 24 GD patients in remission (eGD) and 30 normal controls (NC) were recruited. Thyroid function and autoantibody levels were determined using a chemiluminescence immunoassay. Peripheral blood mononuclear cells (PBMCs) were extracted, and MST-4 and TRAF-6 mRNA and protein levels were determined using real-time PCR and Western blotting, respectively.

RESULTS

1. Thyroid function in the GD group was significantly different from that in the eGD and NC groups (P < 0.05); however, there was no difference in thyroid function between the eGD group and the NC group (P > 0.05). The autoantibody levels in the NC group were significantly different from those in the GD and eGD groups (P < 0.05); however, the difference in the levels between the GD group and eGD group was not statistically significant (P > 0.05). 2. The MST-4 and TRAF-6 mRNA and protein levels in the GD group were significantly lower than those in the NC group (P < 0.05); however, there were no differences in mRNA and protein levels between the GD group and the eGD group or between the eGD group and the NC group (P > 0.05). 3. The correlation between the MST-4 and TRAF-6 mRNA and protein levels was not significant. However, there was a significant correlation between the TRAF-6 mRNA and TPO Ab levels in the eGD group and between the TRAF-6 mRNA and TR Ab levels in the NC group.

CONCLUSION

The MST-4 and TRAF-6 mRNA and protein levels were lower in the GD group than in the NC group, suggesting that MST-4 and TRAF-6 may be important in the pathogenesis of GD. Whether MST-4 influences the innate immune response through TRAF-6 and thus regulates the imbalance in downstream effector T cells requires further study. Investigating the expression of MST-4 and TRAF-6 in GD can provide a new perspective and targets for further study of the upstream mechanism responsible for effector T cell imbalance.

Influences of the circadian clock on neuronal susceptibility to excitotoxicity

Stroke is the third leading cause of death and the primary cause of morbidity in the United States, thus posing an enormous burden on the healthcare system. The factors that determine the risk of an individual toward precipitation of an ischemic event possess a strong circadian component as does the ischemic event itself. This predictability provided a window of opportunity toward the development of chronopharmaceuticals which provided much better clinical outcomes. Experiments from our lab showed for the first time that neuronal susceptibility to ischemic events follows a circadian pattern; hippocampal neurons being most susceptible to an ischemic insult occurring during peak activity in a rodent model of global cerebral ischemia. We also demonstrated that the SCN2.2 cells (like their in vivo counterpart) are resistant to excitotoxicity by glutamate and that this was dependent on activation of ERK signaling. We are currently working on elucidating the complete neuroprotective pathway that provides a barricade against glutamate toxicity in the SCN2.2 cells. Our future experiments will be engaged in hijacking the neuroprotective mechanism in the SCN2.2 cells and applying it to glutamate-susceptible entities in an effort to prevent their death in the presence of excitotoxicity. Despite the advancement in chronopharmaceuticals, optimal clinical outcome with minimal adverse events are difficult to come by at an affordable price. Superior treatment options require a better understanding of molecular mechanisms that define the disease, including the role of the circadian clock.

Molecular biology of atherosclerosis

At least 468 individual genes have been manipulated by molecular methods to study their effects on the initiation, promotion, and progression of atherosclerosis. Most clinicians and many investigators, even in related disciplines, find many of these genes and the related pathways entirely foreign. Medical schools generally do not attempt to incorporate the relevant molecular biology into their curriculum. A number of key signaling pathways are highly relevant to atherogenesis and are presented to provide a context for the gene manipulations summarized herein. The pathways include the following: the insulin receptor (and other receptor tyrosine kinases); Ras and MAPK activation; TNF-α and related family members leading to activation of NF-κB; effects of reactive oxygen species (ROS) on signaling; endothelial adaptations to flow including G protein-coupled receptor (GPCR) and integrin-related signaling; activation of endothelial and other cells by modified lipoproteins; purinergic signaling; control of leukocyte adhesion to endothelium, migration, and further activation; foam cell formation; and macrophage and vascular smooth muscle cell signaling related to proliferation, efferocytosis, and apoptosis. This review is intended primarily as an introduction to these key signaling pathways. They have become the focus of modern atherosclerosis research and will undoubtedly provide a rich resource for future innovation toward intervention and prevention of the number one cause of death in the modern world.

De novo design of protein kinase inhibitors by in silico identification of hinge region-binding fragments

Protein kinases constitute an attractive family of enzyme targets with high relevance to cell and disease biology. Small molecule inhibitors are powerful tools to dissect and elucidate the function of kinases in chemical biology research and to serve as potential starting points for drug discovery. However, the discovery and development of novel inhibitors remains challenging. Here, we describe a structure-based de novo design approach that generates novel, hinge-binding fragments that are synthetically feasible and can be elaborated to small molecule libraries. Starting from commercially available compounds, core fragments were extracted, filtered for pharmacophoric properties compatible with hinge-region binding, and docked into a panel of protein kinases. Fragments with a high consensus score were subsequently short-listed for synthesis. Application of this strategy led to a number of core fragments with no previously reported activity against kinases. Small libraries around the core fragments were synthesized, and representative compounds were tested against a large panel of protein kinases and subjected to co-crystallization experiments. Each of the tested compounds was active against at least one kinase, but not all kinases in the panel were inhibited. A number of compounds showed high ligand efficiencies for therapeutically relevant kinases; among them were MAPKAP-K3, SRPK1, SGK1, TAK1, and GCK for which only few inhibitors are reported in the literature.

Germinal center kinases in immune regulation

Germinal center kinases (GCKs) participate in a variety of signaling pathways needed to regulate cellular functions including apoptosis, cell proliferation, polarity and migration. Recent studies have shown that GCKs are participants in both adaptive and innate immune regulation. However, the differential activation and regulatory mechanisms of GCKs, as well as upstream and downstream signaling molecules, remain to be fully defined. It remains unresolved whether and how GCKs may cross-talk with existing signaling pathways. This review stresses the progresses in research of GCKs relevant to the immune system.

BAY61-3606 affects the viability of colon cancer cells in a genotype-directed manner

Background

K-RAS mutation poses a particularly difficult problem for cancer therapy. Activating mutations in K-RAS are common in cancers of the lung, pancreas, and colon and are associated with poor response to therapy. As such, targeted therapies that abrogate K-RAS-induced oncogenicity would be of tremendous value.

Methods

We searched for small molecule kinase inhibitors that preferentially affect the growth of colorectal cancer cells expressing mutant K-RAS. The mechanism of action of one inhibitor was explored using chemical and genetic approaches.

Results

We identified BAY61-3606 as an inhibitor of proliferation in colorectal cancer cells expressing mutant forms of K-RAS, but not in isogenic cells expressing wild-type K-RAS. In addition to its anti-proliferative effects in mutant cells, BAY61-3606 exhibited a distinct biological property in wild-type cells in that it conferred sensitivity to inhibition of RAF. In this context, BAY61-3606 acted by inhibiting MAP4K2 (GCK), which normally activates NFκβ signaling in wild-type cells in response to inhibition of RAF. As a result of MAP4K2 inhibition, wild-type cells became sensitive to AZ-628, a RAF inhibitor, when also treated with BAY61-3606.

Conclusions

These studies indicate that BAY61-3606 exerts distinct biological activities in different genetic contexts.

c-Jun N-terminal kinase phosphorylates DCP1a to control formation of P bodies

Cytokines and stress-inducing stimuli signal through c-Jun N-terminal kinase (JNK) using a diverse and only partially defined set of downstream effectors. In this paper, the decapping complex subunit DCP1a was identified as a novel JNK target. JNK phosphorylated DCP1a at residue S315 in vivo and in vitro and coimmunoprecipitated and colocalized with DCP1a in processing bodies (P bodies). Sustained JNK activation by several different inducers led to DCP1a dispersion from P bodies, whereas IL-1 treatment transiently increased P body number. Inhibition of TAK1-JNK signaling also affected the number and size of P bodies and the localization of DCP1a, Xrn1, and Edc4. Transcriptome analysis further identified a central role for DCP1a in IL-1-induced messenger ribonucleic acid (mRNA) expression. Phosphomimetic mutation of S315 stabilized IL-8 but not IκBα mRNA, whereas overexpressed DCP1a blocked IL-8 transcription and suppressed p65 NF-κB nuclear activity. Collectively, these data reveal DCP1a as a multifunctional regulator of mRNA expression and suggest a novel mechanism controlling the subcellular localization of DCP1a in response to stress or inflammatory stimuli.

Increased skin papilloma formation in mice lacking glutathione transferase GSTP

The glutathione S-transferase GSTP is overexpressed in many human cancers and chemotherapy-resistant cancer cells, where there is evidence that GSTP may have additional functions beyond its known catalytic role. On the basis of evidence that Gstp-deficient mice have a comparatively higher susceptibility to skin carcinogenesis, we investigated whether this phenotype reflected an alteration in carcinogen detoxification or not. For this study, Gstp(-/-) mice were interbred with Tg.AC mice that harbor initiating H-ras mutations in the skin. Gstp(-/-)/Tg.AC mice exposed to the proinflammatory phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) exhibited higher tumor incidence and multiplicity with a significant thickening of skin after treatment, illustrating hyperproliferative growth. Unexpectedly, we observed no difference in cellular proliferation or apoptosis or in markers of oxidative stress, although higher levels of the inflammatory marker nitrotyrosine were found in Gstp(-/-)/Tg.AC mice. Instead, gene set enrichment analysis of microarray expression data obtained from skin revealed a more proapoptotic and proinflammatory environment shortly after TPA treatment. Within 4 weeks of TPA treatment, Gstp(-/-)/Tg.AC mice displayed altered lipid/sterol metabolism and Wnt signaling along with aberrant processes of cytoskeletal control and epidermal morphogenesis at both early and late times. In extending the evidence that GSTP has a vital role in normal homeostatic control and cancer prevention, they also strongly encourage the emerging concept that GSTP is a major determinant of the proinflammatory character of the tumor microenvironment. This study shows that the GSTP plays a major role in carcinogenesis distinct from its role in detoxification and provides evidence that the enzyme is a key determinant of the proinflammatory tumor environment.

Tilapia hepcidin 2-3 peptide modulates lipopolysaccharide-induced cytokines and inhibits tumor necrosis factor-alpha through cyclooxygenase-2 and phosphodiesterase 4D

The antimicrobial peptide, tilapia hepcidin (TH) 2-3, belongs to the hepcidin family, and its antibacterial function has been reported. Here, we examined the TH2-3-mediated regulation of proinflammatory cytokines in bacterial endotoxin lipopolysaccharide (LPS)-stimulated mouse macrophages. The presence of TH2-3 in LPS-stimulated cells reduced the amount of tumor necrosis factor (TNF)-α secretion. From a microarray, real-time polymerase chain reaction (PCR), and cytokine array studies, we showed down-regulation of the proinflammatory cytokines TNF-α, interleukin (IL)-1α, IL-1β, IL-6, and the prostaglandin synthesis gene, cyclooxygenase (COX)-2, by TH2-3. Studies with the COX-2-specific inhibitor, melaxicam, and with COX-2-overexpressing cells demonstrated the positive regulation of TNF-α and negative regulation of cAMP degradation-specific phosphodiesterase (PDE) 4D by COX-2. In LPS-stimulated cells, TH2-3 acts like melaxicam and down-regulates COX-2 and up-regulates PDE4D. The reduction in intracellular cAMP by TH2-3 or melaxicam in LPS-stimulated cells supports the negative regulation of PDE4D by COX-2 and TH2-3. This demonstrates that the inhibition of COX-2 is among the mechanisms through which TH2-3 controls TNF-α release. At 1 h after treatment, the presence of TH2-3 in LPS-stimulated cells had suppressed the induction of pERK1/2 and prevented the LPS-stimulated nuclear accumulation of NF-κB family proteins of p65, NF-κB2, and c-Rel. In conclusion, TH2-3 inhibits TNF-α and other proinflammatory cytokines through COX-2-, PDE4D-, and pERK1/2-dependent mechanisms.

Targeting kinases for the treatment of inflammatory diseases

IMPORTANCE OF THE FIELD

Inflammatory diseases are one of the major health issues and have become a major focus in the pharmaceutical and biotech industries. To date, drugs prescribed for treatment of these diseases target enzymes that are not specific to the immune system resulting in adverse effects. The main challenge of this research field is, therefore, identifying targets that act specifically on the diseased tissue.

AREAS COVERED IN THIS REVIEW

This review summarizes drug discovery efforts on kinases that have been identified as key players mediating inflammation and autoimmune disorders. In particular, we discuss recent developments on well-established targets such as mammalian target of rapamycin, JAK3, spleen tyrosine kinase, p38α and lymphocyte specific kinase but provide also a perspective on emerging targets.

WHAT THE READER WILL GAIN

The reader will obtain an overview of drug discovery efforts on kinases in inflammation, recent clinical and preclinical data and developed inhibitor scaffolds. In addition, the reader will be updated on issues in target validation of current drug targets and the potential of selected novel kinase targets in this important disease area.

TAKE HOME MESSAGE

Cellular signaling networks that regulate inflammatory response are still poorly understood making rational selection of targets challenging. Recent data suggest that kinase targets that are specific to the immune system and mediate signals immediately downstream of surface receptors are most efficacious in the clinic.

Evolution of host innate defence: insights from Caenorhabditis elegans and primitive invertebrates

The genetically tractable model organism Caenorhabditis elegans was first used to model bacterial virulence in vivo a decade ago. Since then, great strides have been made in identifying the host response pathways that are involved in its defence against infection. Strikingly, C. elegans seems to detect, and respond to, infection without the involvement of its homologue of Toll-like receptors, in contrast to the well-established role for these proteins in innate immunity in mammals. What, therefore, do we know about host defence mechanisms in C. elegans and what can they tell us about innate immunity in higher organisms?

Activation of SAPK/JNKs in vitro

The stress-activated protein kinase/c-jun N-terminal kinases (SAPK/JNKs) are mitogen-activated protein kinases (MAPKs) that are activated by stressful and inflammatory stimuli and regulate cellular responses such as proliferation, differentiation, and apoptosis. The SAPK/JNKs are phosphorylated and activated by the MAP kinase kinases (MAP2Ks), SEK1/MKK4 and MKK7. These MAP2Ks are phosphorylated and activated by upstream stress-activated MAPK kinase kinases (MAP3Ks). Upon activation, SAPK/JNKs translocate to the nucleus and phosphorylate transcription factors, ultimately resulting in the modulation of gene expression. We have analyzed the activation of SAPK/JNK and stress-activated MAP3Ks using in vitro kinase assays. In addition, we have studied the role of different MAP3Ks in SAPK/JNK signaling by silencing specific MAP3K expression with RNAi and then analyzing the effect on activation of SAPK/JNKs and other MAPKs.