Tribbles 2 (Trib2) is a novel regulator of toll-like receptor 5 signaling

The Impact of A3AR Antagonism on the Differential Expression of Chemoresistance-Related Genes in Glioblastoma Stem-like Cells

Glioblastoma (GB) is the most aggressive and common primary malignant tumor of the brain and central nervous system. Without treatment, the average patient survival time is about six months, which can be extended to fifteen months with multimodal therapies. The chemoresistance observed in GB is, in part, attributed to the presence of a subpopulation of glioblastoma-like stem cells (GSCs) that are characterized by heightened tumorigenic capacity and chemoresistance. GSCs are situated in hypoxic tumor niches, where they sustain and promote the stem-like phenotype and have also been correlated with high chemoresistance. GSCs have the particularity of generating high levels of extracellular adenosine (ADO), which causes the activation of the A3 adenosine receptor (A3AR) with a consequent increase in the expression and activity of genes related to chemoresistance. Therefore, targeting its components is a promising alternative for treating GB. This analysis determined genes that were up- and downregulated due to A3AR blockades under both normoxic and hypoxic conditions. In addition, possible candidates associated with chemoresistance that were positively regulated by hypoxia and negatively regulated by A3AR blockades in the same condition were analyzed. We detected three potential candidate genes that were regulated by the A3AR antagonist MRS1220 under hypoxic conditions: LIMD1, TRIB2, and TGFB1. Finally, the selected markers were correlated with hypoxia-inducible genes and with the expression of adenosine-producing ectonucleotidases. In conclusion, we detected that hypoxic conditions generate extensive differential gene expression in GSCs, increasing the expression of genes associated with chemoresistance. Furthermore, we observed that MRS1220 could regulate the expression of LIMD1, TRIB2, and TGFB1, which are involved in chemoresistance and correlate with a poor prognosis, hypoxia, and purinergic signaling.

The immunopathogenesis of narcolepsy type 1

Narcolepsy type 1 (NT1) is a chronic sleep disorder resulting from the loss of a small population of hypothalamic neurons that produce wake-promoting hypocretin (HCRT; also known as orexin) peptides. An immune-mediated pathology for NT1 has long been suspected given its exceptionally tight association with the MHC class II allele HLA-DQB1*06:02, as well as recent genetic evidence showing associations with polymorphisms of T cell receptor genes and other immune-relevant loci and the increased incidence of NT1 that has been observed after vaccination with the influenza vaccine Pandemrix. The search for both self-antigens and foreign antigens recognized by the pathogenic T cell response in NT1 is ongoing. Increased T cell reactivity against HCRT has been consistently reported in patients with NT1, but data demonstrating a primary role for T cells in neuronal destruction are currently lacking. Animal models are providing clues regarding the roles of autoreactive CD4+ and CD8+ T cells in the disease. Elucidation of the pathogenesis of NT1 will allow for the development of targeted immunotherapies at disease onset and could serve as a model for other immune-mediated neurological diseases.

The molecular characteristic analysis of TRIB2 gene and its expressional patterns in Bos grunniens tissue and granulosa cells

Tribbles homolog 2 (TRIB2) plays an important role in the follicular development of female mammals. However, its expression and function in the yak (Bos grunniens) are still unclear. In this study, we predicted the molecular characteristics of TRIB2, and revealed its expression pattern in yak (Bos grunniens) tissues and ovarian granulosa cells. We cloned the full length of the yak TRIB2 gene obtained by RT-PCR was 1368 bp and the coding sequence (CDS) was 624 bp, encoding 207 amino acids (AA). Homology analysis showed that the yak TRIB2 is highly conserved among species. TRIB2 was detected to be extensively expressed in seven tissues of the yak liver, spleen, lung, kidney, ovary, oviduct and uterus by qPCR. The expression of TRIB2 mRNA in the ovary during gestation was significantly lower than that in the non-pregnant (p < 0.05). At each stage of follicle development, the TRIB2 mRNA in granulosa cells showed a significant upward trend with the development of follicles. The expression of TRIB2 gradually decreased with the increase of the culture time of the granulosa cells in vitro. In conclusion, these results suggest that TRIB2 may play an important role in the follicular development of yaks.

The role of tribbles homolog 2 in vascular smooth muscle cell proliferation

Tribbles homolog 2 (TRIB2) functions as an adapter protein that regulates signal transductions involved in a variety of cellular functions, including tumorigenesis. However, the role of TRIB2 in the proliferation of vascular smooth muscle cells (VSMCs) and the underlying expression mechanisms remain unclear. The present study investigated the role of TRIB2 in VSMC proliferation and revealed that TRIB2 expression increases following vascular injury and platelet-derived growth factor (PDGF)-BB-stimulated VSMCs. We found that pretreatment with diphenyleneiodonium (a nicotinamide adenine dinucleotide phosphate oxidase inhibitor), U0126 (an inhibitor of mitogen-activated protein kinase kinase 1 [MEK1]), or siRNA targeting the gene encoding early growth response 1 (EGR-1) significantly inhibits PDGF-BB-induced TRIB2 expression in VSMCs. Furthermore, TRIB2 knockdown significantly inhibits PDGF-BB-induced proliferation of VSMCs but does not affect the phosphorylation of AKT. However, phosphorylation of ERK1 and expression of proliferating cell nuclear antibody are significantly suppressed in VSMCs by PDGF-BB stimulation. Thus, PDGF-BB-induced TRIB2 expression is mediated by ROS/ERK/EGR-1 pathways and plays a critical role in VSMC proliferation via modulation of ERK activity. We propose TRIB2 as a promising therapeutic target for the prevention of neointima formation and vascular disease.

Identification of menaquinone-4 (vitamin K2) target genes in bovine endometrial epithelial cells in vitro

The effect of vitamin K on bovine endometrial epithelial cells has not been thoroughly investigated. The objective of this study was to examine the effect of the biologically active form of vitamin K, menaquinone-4, on gene expression in bovine endometrial epithelial cells. First, we examined the mRNA and protein expression levels of UBIAD1, a menaquinone-4 biosynthetic enzyme. Second, we screened for potential target genes of menaquinone-4 in bovine endometrial epithelial cells using RNA-sequencing. We found 50 differentially expressed genes; 42 were upregulated, and 8 were downregulated. Among them, a dose-dependent response to menaquinone-4 was observed for the top three upregulated (TRIB3, IL6, and TNFAIP3) and downregulated (CDC6, ORC1, and RRM2) genes. It has been suggested that these genes play important roles in reproductive events. In addition, GDF15 and VEGFA, which are important for cellular functions as they are commonly involved in pathways, such as positive regulation of cell communication, cell differentiation, and positive regulation of MAPK cascade, were upregulated in endometrial epithelial cells by menaquinone-4 treatment. To the best of our knowledge, this is the first study showing the expression of UBIAD1 in the bovine uterus. Moreover, the study determined menaquinone-4 target genes in bovine endometrial epithelial cells, which may positively affect pregnancy with alteration of gene expression in cattle uterus.

Recent advances in targeting protein kinases and pseudokinases in cancer biology

Kinases still remain the most favorable members of the druggable genome, and there are an increasing number of kinase inhibitors approved by the FDA to treat a variety of cancers. Here, we summarize recent developments in targeting kinases and pseudokinases with some examples. Targeting the cell cycle machinery garnered significant clinical success, however, a large section of the kinome remains understudied. We also review recent developments in the understanding of pseudokinases and discuss approaches on how to effectively target in cancer.

Narcolepsy: a model interaction between immune system, nervous system, and sleep-wake regulation

Narcolepsy is a rare chronic neurological disorder characterized by an irresistible excessive daytime sleepiness and cataplexy. The disease is considered to be the result of the selective disruption of neuronal cells in the lateral hypothalamus expressing the neuropeptide hypocretin, which controls the sleep-wake cycle. Diagnosis and management of narcolepsy represent still a substantial medical challenge due to the large heterogeneity in the clinical manifestation of the disease as well as to the lack of understanding of the underlying pathophysiological mechanisms. However, significant advances have been made in the last years, thus opening new perspective in the field. This review describes the current knowledge of clinical presentation and pathology of narcolepsy as well as the existing diagnostic criteria and therapeutic intervention for the disease management. Recent evidence on the potential immune-mediated mechanisms that may underpin the disease establishment and progression are also highlighted.

Potential innate immunity-related markers of endometrial receptivity and recurrent implantation failure (RIF)

The successful implantation of the embryo into a receptive endometrium is essential for the establishment of a viable pregnancy while recurrent implantation failure (RIF) is a real challenge in assisted reproduction. The maternal innate immune system, specifically the Toll-like receptors (TLRs), are involved in maintaining immunity in the female reproductive tract (FRT) required for fertility. In this study, we aimed to investigate the importance of innate immunity-related gene expression in the regulation of human fertility and as a prediction of potential outcome of in vitro fertilization - embryo transfer (IVF-ET), thus, we assessed the gene expression levels of TLR signalling molecules using quantitative real-time PCR between endometrial biopsies of healthy fertile women, and the patients experiencing RIF. Interestingly, our results showed that, TRIB2 and TLR9 genes were differentially expressed between the endometrial biopsies of healthy women and those with RIF. However, comparing expression levels of same genes between pre-receptive and receptive healthy endometrial biopsies showed different genes (ICAM1, NFKBIA, VCAM1, LIF, VEGFB, TLR5) had significantly altered expression, suggesting their involvement in endometrial receptivity. Thus, further investigations will enable us to better understand the role of these genes in the biology of FRT and as a possible target for the improvement of infertility treatments and/or development of non-hormonal contraception.

A methyltransferase-like 14/miR-99a-5p/tribble 2 positive feedback circuit promotes cancer stem cell persistence and radioresistance via histone deacetylase 2-mediated epigenetic modulation in esophageal squamous cell carcinoma

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is a highly aggressive and treatment-resistant tumor. The biological implications and molecular mechanism of cancer stem-like cells (CSCs) in ESCC, which contribute to therapeutic resistance such as radioresistance, remain elusive.

METHODS

Quantitative real-time polymerase chain reaction, western blotting, immunohistochemistry, and in situ hybridization assays were used to detect methyltransferase-like 14 miR-99a-5p tribble 2 (METTL14/miR-99a-5p/TRIB2) expression in ESCC. The biological functions of METTL14/miR-99a-5p/TRIB2 were demonstrated in vitro and in vivo. Mass spectrum analysis was used to identify the downstream proteins regulated by TRIB2. Chromatin immunoprecipitation (IP), IP, N6 -methyladenosine (m6 A)-RNA IP, luciferase reporter, and ubiquitination assays were employed to explore the molecular mechanisms underlying this feedback circuit and its downstream pathways.

RESULTS

We found that miR-99a-5p was significantly decreased in ESCC. miR-99a-5p inhibited CSCs persistence and the radioresistance of ESCC cells, and miR-99a-5p downregulation predicted an unfavorable prognosis of ESCC patients. Mechanically, we unveiled a METTL14-miR-99a-5p-TRIB2 positive feedback loop that enhances CSC properties and radioresistance of ESCC cells. METTL14, an m6 A RNA methyltransferase downregulated in ESCC, suppresses TRIB2 expression via miR-99a-5p-mediated degradation of TRIB2 mRNA by targeting its 3' untranslated region, whereas TRIB2 induces ubiquitin-mediated proteasomal degradation of METTL14 in a COP1-dependent manner. METTL14 upregulates miR-99a-5p by modulating m6 A-mediated, DiGeorge critical region 8-dependent pri-mir-99a processing. Hyperactivation of TRIB2 resulting from this positive circuit was closely correlated with radioresistance and CSC characteristics. Furthermore, TRIB2 activates HDAC2 and subsequently induces p21 epigenetic repression through Akt/mTOR/S6K1 signaling pathway activation. Pharmacologic inhibition of HDAC2 effectively attenuates the TRIB2-mediated effect both in vitro and in patient-derived xenograft models.

CONCLUSION

Our data highlight the presence of the METTL14/miR-99a-5p/TRIB2 axis and show that it is positively associated with CSC characteristics and radioresistance of ESCC, suggesting potential therapeutic targets for ESCC treatment.

LncRNA UCA1 Accelerates the Progression of Ulcerative Colitis via Mediating the miR-331-3p/BRD4 Axis

Background

Ulcerative colitis (UC) has become one of the fastest-growing severe diseases worldwide with high morbidity. This research aimed to explore the function of lncRNA UCA1 in UC progression.

Methods

RT-qPCR analysis was used to examine the expression of UCA1 level in colonic mucosa tissues of UC patients. Then, fetal human cells (FHCs) were stimulated by LPS to induce inflammatory injury. CCK-8, flow cytometry and ELISA were adopted to determine the influence of UCA1 depletion on cell viability, apoptosis and pro-inflammatory factors levels in LPS-induced FHCs. The interaction between UCA1 and miR-331-3p or BRD4 was confirmed by luciferase reporter assay. The expressions of key factors involved in NF-κB pathway were assessed by Western blotting.

Results

LncRNA UCA1 level was elevated in colonic mucosa tissues of UC patients. LPS stimulation restrained cell viability and promoted the apoptosis and inflammatory factors levels, thus inducing FHCs inflammatory injury, while these effects were partially abolished by UCA1 knockdown. Moreover, it was found that UCA1 silence improved LPS-triggered cell injury via miR-331-3p. In addition, BRD4 was directly targeted by miR-331-3p, and BRD4 deficiency neutralized the effects of miR-331-3p repression on LPS-triggered injury in LPS-treated FHCs.

Conclusion

Our data determined that UCA1 knockdown attenuated UC development via targeting the miR-331-3p/BRD4/NF-κB pathway.

The Critical Role of TRIB2 in Cancer and Therapy Resistance

Simple Summary

The Tribbles proteins are members of CAMK Ser/Thr protein kinase family. They are evolutionary conserved pseudokinases found in most tissues of eukaryotic organisms. This ubiquitously expressed protein family is characterized by containing a catalytically deficient kinase domain which lacks amino acid residues required for the productive interaction with ATP and metal ions. Tribbles proteins exert their biological functions mainly through direct interaction with MAPKK and AKT proteins, therefore regulating important pathways involved in cell proliferation, apoptosis and differentiation. Due to the role of MAPKK and AKT signalling in the context of cancer development, Tribbles proteins have been recently considered as biomarkers of cancer progression. Furthermore, as the atypical pseudokinase domain retains a binding platform for substrates, Tribbles targeting provides an attractive opportunity for drug development.

Abstract

The Tribbles pseudokinases family consists of TRIB1, TRIB2, TRIB3 and STK40 and, although evolutionarily conserved, they have distinctive characteristics. Tribbles members are expressed in a context and cell compartment-dependent manner. For example, TRIB1 and TRIB2 have potent oncogenic activities in vertebrate cells. Since the identification of Tribbles proteins as modulators of multiple signalling pathways, recent studies have linked their expression with several pathologies, including cancer. Tribbles proteins act as protein adaptors involved in the ubiquitin-proteasome degradation system, as they bridge the gap between substrates and E3 ligases. Between TRIB family members, TRIB2 is the most ancestral member of the family. TRIB2 is involved in protein homeostasis regulation of C/EBPα, β-catenin and TCF4. On the other hand, TRIB2 interacts with MAPKK, AKT and NFkB proteins, involved in cell survival, proliferation and immune response. Here, we review the characteristic features of TRIB2 structure and signalling and its role in many cancer subtypes with an emphasis on TRIB2 function in therapy resistance in melanoma, leukemia and glioblastoma. The strong evidence between TRIB2 expression and chemoresistance provides an attractive opportunity for targeting TRIB2.

Tribbles homolog 2 (Trib2), a pseudo serine/threonine kinase in tumorigenesis and stem cell fate decisions

The family of Tribbles proteins play many critical nonenzymatic roles and regulate a wide range of key signaling pathways. Tribbles homolog 2 (Trib2) is a pseudo serine/threonine kinase that functions as a scaffold or adaptor in various physiological and pathological processes. Trib2 can interact with E3 ubiquitin ligases and control protein stability of downstream effectors. This protein is induced by mitogens and enhances the propagation of several cancer cells, including myeloid leukemia, liver, lung, skin, bone, brain, and pancreatic. Thus, Trib2 can be a predictive and valuable biomarker for the diagnosis and treatment of cancer. Recent studies have illustrated that Trib2 plays a major role in cell fate determination of stem cells. Stem cells have the capacity to self-renew and differentiate into specific cell types. Stem cells are important sources for cell-based regenerative medicine and drug screening. Trib2 has been found to increase the self-renewal ability of embryonic stem cells, the reprogramming efficiency of somatic cells, and chondrogenesis. In this review, we will focus on the recent advances of Trib2 function in tumorigenesis and stem cell fate decisions.

Tribbles Pseudokinase 2 (TRIB2) Regulates Expression of Binding Partners in Bovine Granulosa Cells

Members of the Tribbles (TRIB) family of pseudokinases are critical components of intracellular signal transduction pathways in physiological and pathological processes. TRIBs, including TRIB2, have been previously shown as signaling mediators and scaffolding proteins regulating numerous cellular events such as proliferation, differentiation and cell death through protein stability and activity. However, the signaling network associated with TRIB2 and its binding partners in granulosa cells during ovarian follicular development is not fully defined. We previously reported that TRIB2 is differentially expressed in growing dominant follicles while downregulated in ovulatory follicles following the luteinizing hormone (LH) surge or human chorionic gonadotropin (hCG) injection. In the present study, we used the yeast two-hybrid screening system and in vitro coimmunoprecipitation assays to identify and confirm TRIB2 interactions in granulosa cells (GCs) of dominant ovarian follicles (DFs), which yielded individual candidate binding partners including calmodulin 1 (CALM1), inhibin subunit beta A (INHBA), inositol polyphosphate phosphatase-like 1 (INPPL1), 5'-nucleotidase ecto (NT5E), stearoyl-CoA desaturase (SCD), succinate dehydrogenase complex iron sulfur subunit B (SDHB) and Ras-associated protein 14 (RAB14). Further analyses showed that all TRIB2 binding partners are expressed in GCs of dominant follicles but are differentially regulated throughout the different stages of follicular development. CRISPR/Cas9-driven inhibition along with pQE-driven overexpression of TRIB2 showed that TRIB2 differently regulates expression of binding partners, which reveals the importance of TRIB2 in the control of gene expression linked to various biological processes such as proliferation, differentiation, cell migration, apoptosis, calcium signaling and metabolism. These data provide a larger view of potential TRIB2-regulated signal transduction pathways in GCs and provide strong evidence that TRIB2 may act as a regulator of target genes during ovarian follicular development.

Regulation of gene expression in the bovine blastocyst by colony-stimulating factor 2 is disrupted by CRISPR/Cas9-mediated deletion of CSF2RA

Colony-stimulating factor 2 (CSF2) functions in the reproductive tract to modulate the function of the preimplantation embryo. The β subunit of the CSF2 receptor (CSF2RB) is not expressed in the embryo, and signal transduction is therefore different than for myeloid cells where the receptor is composed of α (CSF2RA) and β subunits. Here, we produced embryos in which exons 5 and 6 of CSF2RA were disrupted using the CRISPR/Cas 9 system to test whether CSF2RA signaling was essential for actions of CSF2 in the bovine embryo. Wild-type and CSF2RA knockout embryos were treated with 10 ng/mL CSF2 or vehicle at day 5 of development. Blastocysts were harvested at day 8 to determine transcript abundance of 90 genes by real-time polymerase chain reaction (PCR). Responses in female blastocysts were examined separately from male blastocysts because actions of CSF2 are sex-dependent. For wild-type embryos, CSF2 altered expression of 10 genes in females and 20 in males. Only three genes were affected by CSF2 in a similar manner for both sexes. Disruption of CSF2RA prevented the effect of CSF2 on expression for 9 of 10 CSF2-regulated genes in females and 19 of 20 genes in males. The results confirm the importance of CSF2RA for regulation of gene expression by CSF2 in the blastocyst.

Narcolepsy Type I as an autoimmune disorder

Narcolepsy Type 1 (NT1) is hypothesized to be an autoimmune disease targeting the hypocretin/orexin neurons in the lateral hypothalamus. Ample genetic and epidemiologic evidence point in the direction of a pathogenesis involving the immune system. Many autoantibodies have been detected in blood samples from NT1 patients, but none in a consistent manner. Importantly, T cells directed toward hypocretin/orexin neurons have been detected in samples from NT1 patients. However, it remains to be seen if these potentially autoreactive T cells are also present in the hypothalamus and if they are pathogenic. For this reason, NT1 does still not fully meet the criteria for being classified as a genuine autoimmune disease, even though more and more results are pointing in that direction as will be described in this chapter. The autoimmune hypothesis has led to many attempts at slowing or stopping disease progression with immunomodulatory treatment, but so far the overall results have not been very encouraging. It is clear that more research into the pathogenesis of NT1 is needed to establish the precise role of the immune system in disease development.

TRIM21 causes abnormal expression of IL-6 in oral lichen planus via the TRIB2-MAPK signal axis

Oral lichen planus (OLP) is a common chronic inflammatory disease in the oral cavity, and has the risk of developing into oral squamous cell carcinoma (OSCC). It is necessary to discover the role of TRIM21 in the pathogenesis of OLP and its underlying mechanism.

METHODS

Western bolt and qPCR assays were used to detect the effects of TRIM21 on cellular levels of ERK, p-ERK, AP-1, IL-6, TRIB2, IRF3, and IRF7, while co-immunoprecipitation was performed to verify the interaction between Trim21 and TRIB2 protein. The TRIM21 effect on TH1/TH2 balance in T cells was also evaluated using ELISA.

RESULTS

The results of western blot showed that TRIM21 overexpression significantly increased p-ERK, c-fos, c-jun, IL-6 and TRIB2 levels in H9 cells (P<0.01 and P<0.001), however, inhibited the IRF3 and IRF7 levels (P<0.05). On the other hand, TRIM21 did not regulate the phosphorylation of ERK and the mRNA expression of AP-1 and TRIB2. In addition, TRIM21 was in relation to the proteasome degradation in TRIB2-ERK. TRIM21 also regulated the level of TRIB2 not only by inhibiting the ubiquitination of TRIB2, but also by affecting IL-6 through the ERK pathway.

CONCLUSION

TRIM21 caused abnormal expression of IL-6 in OLP via regulating TRIB2-MAPK signal axis, leading to the disrupted Th1/Th2 balance in T lymphocytes.

Functional effects of Tribbles homolog 2 in bovine ovarian granulosa cells†

Tribbles homologs (TRIB) 1, 2, and 3 represent atypical members of the serine/threonine kinase superfamily. We previously identified TRIB2 as a differentially expressed gene in granulosa cells (GCs) of bovine preovulatory follicles. The current study aimed to further investigate TRIB2 regulation and study its function in the ovary. GCs were collected from follicles at different developmental stages: small antral follicles (SF), dominant follicles (DF) at day 5 of the estrous cycle, and hCG-induced ovulatory follicles (OFs). RT-qPCR analyses showed greater expression of TRIB2 in GC of DF as compared to OF and a significant downregulation of TRIB2 steady-state mRNA amounts by hCG/LH, starting at 6 h through 24 h post-hCG as compared to 0 h. Specific anti-TRIB2 polyclonal antibodies were generated and western blot analysis confirmed TRIB2 downregulation by hCG at the protein level. In vitro studies showed that FSH stimulates TRIB2 expression in GC. Inhibition of TRIB2 using CRISPR/Cas9 resulted in a significant increase in PCNA expression and an increase in steroidogenic enzyme CYP19A1 expression, while TRIB2 overexpression tended to decrease GC proliferation. TRIB2 inhibition also resulted in a decrease in transcription factors connective tissue growth factor (CTGF) and ankyrin repeat domain-containing protein 1 (ANKRD1) expression, while TRIB2 overexpression increased CTGF and ANKRD1. Additionally, western blot analyses showed reduction in ERK1/2 (MAPK3/1) and p38MAPK (MAPK14) phosphorylation levels following TRIB2 inhibition, while TRIB2 overexpression increased p-ERK1/2 and p-p38MAPK. These results provide evidence that TRIB2 modulates MAPK signaling in GC and that TRIB2 could act as a regulator of GC proliferation and function, which could affect steroidogenesis during follicular development.

Association Analysis of a Microsatellite Repeat in the TRIB1 Gene With Prostate Cancer Risk, Aggressiveness and Survival

With an estimated 1.1 million men worldwide diagnosed with prostate cancer yearly, effective and more specific biomarkers for early diagnosis could lead to better patient outcome. As such, novel genetic markers are sought for this purpose. The tribbles homologue 1 gene (TRIB1) has recently shown to have a role in prostate tumorigenesis and data-mining of prostate cancer expression data confirmed clinical significance of TRIB1 in prostate cancer. For the first time, a polymorphic microsatellite in this gene was studied for its potential association with prostate cancer risk and aggressiveness. Genomic DNA was extracted from a cohort of 1,152 prostate cancer patients and 1,196 cancer-free controls and the TTTTG-TRIB1 microsatellite was genotyped. The socio-demographic and clinical characteristics were analyzed using the non-parametric t-test and two-way ANOVA. Association of the TTTTG-TRIB1 microsatellite and prostate cancer risk and aggressiveness were analyzed by binary logistic regression and confirmed by bootstrapping. Total and prostate cancer mortality was analyzed using the Kaplan Meier test. Genotype and allele correlation with TRIB1 mRNA levels was analyzed using the non-parametric Kolmogorov-Smirnov test. To predict the effect that the TTTTG-TRIB1 polymorphisms had on the mRNA structure, the in silico RNA folding predictor tool, mfold, was used. By analyzing the publicly available data, we confirmed a significant over-expression of TRIB1 in prostate cancer compared to other cancer types, and an over-expression in prostate cancerous tissue compared to adjacent benign. Three alleles (three-five repeats) were observed for TTTTG-TRIB1. The three-repeat allele was associated with prostate cancer risk at the allele (OR = 1.16; P = 0.044) and genotypic levels (OR = 1.70; P = 0.006) and this association was age-independent. The four-repeat allele was inversely associated with prosatet cancer risk (OR = 0.57; P < 0.0001). TRIB1 expression was upregulated in tumors when compared to adjacent cancer-free tissue but was not allele specific. In silico analysis suggested that the TTTTG-TRIB1 alleles may alter TRIB1 mRNA structure. In summary, the three-repeat allele was significantly associated with prostate cancer risk, suggesting a biomarker potential for this microsatellite to predict prostate cancer. Further studies are needed to elucidate the functional role of this microsatellite in regulating TRIB1 expression, perhaps by affecting the TRIB1 mRNA structure and stability.

A Trib2-p38 axis controls myeloid leukaemia cell cycle and stress response signalling

Trib2 pseudokinase is involved in the etiology of a number of cancers including leukaemia, melanoma, ovarian, lung and liver cancer. Both high and low Trib2 expression levels correlate with different types of cancer. Elevated Trib2 expression has oncogenic properties in both leukaemia and lung cancer dependent on interactions with proteasome machinery proteins and degradation of transcription factors. Here, we demonstrated that Trib2 deficiency conferred a growth and survival advantage both at steady state and in stress conditions in leukaemia cells. In response to stress, wild type leukaemia cells exited the cell cycle and underwent apoptosis. In contrast, Trib2 deficient leukaemia cells continued to enter mitosis and survive. We showed that Trib2 deficient leukaemia cells had defective MAPK p38 signalling, which associated with a reduced γ-H2Ax and Chk1 stress signalling response, and continued proliferation following stress, associated with inefficient activation of cell cycle inhibitors p21, p16 and p19. Furthermore, Trib2 deficient leukaemia cells were more resistant to chemotherapy than wild type leukaemia cells, having less apoptosis and continued propagation. Trib2 re-expression or pharmacological activation of p38 in Trib2 deficient leukaemia cells sensitised the cells to chemotherapy-induced apoptosis comparable with wild type leukaemia cells. Our data provide evidence for a tumour suppressor role of Trib2 in myeloid leukaemia via activation of p38 stress signalling. This newly identified role indicates that Trib2 may counteract the propagation and chemotherapy resistance of leukaemia cells.

Down-regulation of toll-like receptor 4 alleviates intestinal ischemia reperfusion injury and acute lung injury in mice

Intestinal ischemia reperfusion (IR) injury is a critical problem, which can cause intestinal injury locally and acute lung injury (ALI) distally by inflammatory responses and oxidative stress. Toll-like receptor 4 (TLR4) is involved in innate immune and inflammatory responses. This study was to determine whether TLR4 mutant can attenuate intestinal and lung injuries after intestinal IR. Wild type (WT) and TLR4 mutant mice were submitted to intestinal IR by occluding the superior mesenteric artery. Histological assessment of the intestine and the lung were conducted by HE staining. The levels of proinflammatory cytokines, oxidative stress markers, apoptotic index and other mediators were measured. In addition, a 24-hour survival study was performed. Histological assessment showed that intestinal IR caused serious injuries in the intestine and the lung, corroborated by increased proinflammatory cytokines in the circulation. TLR4 mutant suppressed the histological injuries as demonstrated by significantly decreased pathological scores. Consistent with the morphological results, the TLR4 mutant mice exhibited remarkably lowered cytokine expressions in the intestine (TNF-α, IL-6, IL-1β, and NF-κB) and the lung (NO, iNOS, MCP-1, MIP-2, NF-κB, and Caspase-3). ALT and creatinine were also significantly dampened in the liver and kidney, respectively. Furthermore, the survival rate over the course of 24 hours was significantly improved. Collectively, the findings reveal that TLR4 mutant significantly abated the intestinal IR injury and ALI at least in part by alleviating the inflammatory response and oxidative stress.

Tribbles 2 mediates cisplatin sensitivity and DNA damage response in epithelial ovarian cancer

Aim was to identify methylated genes with functional involvement in cisplatin-resistance development of epithelial ovarian cancer (EOC). Genome-wide analyses of hypermethylated CpG-islands in resistant cell lines in combination with qRT-PCR analyses were used to identify epigenetically silenced genes. EOC-Type-II tumors were analyzed for gene methylation and expression and TCGA data were interrogated in-silico. Experiments revealed 37 commonly hypermethylated genes in resistant cells of which Tribbles 2 (TRIB2) showed the most pronounced downregulation on mRNA level and was characterized further. TRIB2 showed a reactivation after 5'-Aza-Cytidine treatment in resistant cells but a cisplatin-dependent, prominent upregulation on mRNA level in sensitive cells, only. Re-expression in resistant A2780 cells increased the sensitivity to cisplatin and other DNA-damaging agents, but not taxanes. Contrary, knockdown of TRIB2 increased resistance to cisplatin in sensitive cells. TRIB2 was involved in the induction of a cisplatin-dependent cell cycle arrest and apoptosis by influencing p21 and survivin expression. An increased Pt-DNA-adduct formation in TRIB2 re-expressing cells did not translate in higher levels of dsDNA damage (yH2AX-foci). Thus, TRIB2 is potentially involved in the signal transduction from nucleotide excision repair of intrastrand cross links. Importantly, patient stratification of two homogenous cohorts of EOC-Type-II patients from Jena (n = 38) and the TCGA (n = 149) by TRIB2 mRNA expression consistently revealed a significantly decreased PFS for patients with low TRIB2 levels (log-rank p < 0.05). Tumors from resistant patients expressed the lowest levels of TRIB2. Downregulation of TRIB2 contributes to platin-resistance and TRIB2 expression should be validated as prognostic and predictive marker for EOC.

Tribbles ortholog NIPI-3 and bZIP transcription factor CEBP-1 regulate a Caenorhabditis elegans intestinal immune surveillance pathway

BACKGROUND

Many pathogens secrete toxins that target key host processes resulting in the activation of immune pathways. The secreted Pseudomonas aeruginosa toxin Exotoxin A (ToxA) disrupts intestinal protein synthesis, which triggers the induction of a subset of P. aeruginosa-response genes in the nematode Caenorhabditis elegans.

RESULTS

We show here that one ToxA-induced C. elegans gene, the Tribbles pseudokinase ortholog nipi-3, is essential for host survival following exposure to P. aeruginosa or ToxA. We find that NIPI-3 mediates the post-developmental expression of intestinal immune genes and proteins and primarily functions in parallel to known immune pathways, including p38 MAPK signaling. Through mutagenesis screening, we identify mutants of the bZIP C/EBP transcription factor cebp-1 that suppress the hypersusceptibility defects of nipi-3 mutants.

CONCLUSIONS

NIPI-3 is a negative regulator of CEBP-1, which in turn negatively regulates protective immune mechanisms. This pathway represents a previously unknown innate immune signaling pathway in intestinal epithelial cells that is involved in the surveillance of cellular homeostasis. Because NIPI-3 and CEBP-1 are also essential for C. elegans development, NIPI-3 is analogous to other key innate immune signaling molecules such as the Toll receptors in Drosophila that have an independent role during development.

Competition between members of the tribbles pseudokinase protein family shapes their interactions with mitogen activated protein kinase pathways

Spatio-temporal regulation of intracellular signalling networks is key to normal cellular physiology; dysregulation of which leads to disease. The family of three mammalian tribbles proteins has emerged as an important controller of signalling via regulating the activity of mitogen activated protein kinases (MAPK), the PI3-kinase induced signalling network and E3 ubiquitin ligases. However, the importance of potential redundancy in the action of tribbles and how the differences in affinities for the various binding partners may influence signalling control is currently unclear. We report that tribbles proteins can bind to an overlapping set of MAPK-kinases (MAPKK) in live cells and dictate the localisation of the complexes. Binding studies in transfected cells reveal common regulatory mechanisms and suggest that tribbles and MAPKs may interact with MAPKKs in a competitive manner. Computational modelling of the impact of tribbles on MAPK activation suggests a high sensitivity of this system to changes in tribbles levels, highlighting that these proteins are ideally placed to control the dynamics and balance of activation of concurrent signalling pathways.

Tribbles and arthritis: what are the links?

The pseudo-kinase family of tribbles (TRIB) proteins has been linked to a variety of cell signalling pathways and appears to have functionally divergent roles with respect to intracellular protein degradation and the ability to regulate signal transduction pathways. In the arthritides, inflammation and a wide variety of pro-inflammatory pathways have been implicated to drive the cartilage destruction and consequent disability associated with both rheumatoid arthritis (RA) and osteoarthritis (OA). Despite burgeoning evidence linking the TRIB to inflammation-related pathologies such as diabetes, multiple sclerosis and cancer, very little is known about their roles in arthritis. The present review discusses current knowledge of the impact of TRIB on pro-inflammatory cellular mechanisms and pathways known to be important in the pathogenesis of RA and OA.

Tribbles role in reproduction

Tribbles (TRIB) proteins, a family of evolutionary conserved psuedokinase proteins, modulate various signalling pathways within the cell. The regulatory roles of TRIB make them an important part of a number of biological processes ranging from cell proliferation to metabolism, immunity, inflammation and carcinogenesis. Innate immune system plays a pivotal role during the regulation of reproductive processes that allows successful creation of an offspring. Its involvement initiates from fertilization of the oocyte by spermatozoon and lasts throughout early embryonic development, pregnancy and labour. Therefore, there is a close cooperation between the reproductive system and the innate immune system. Evidence from our lab has demonstrated that improper activation of the innate immune system can reduce embryo implantation, thus leading to infertility. Therefore, control mechanisms regulating the innate immune system function can be critical for successful reproductive events.

TRIB2 regulates normal and stress-induced thymocyte proliferation

TRIB2, a serine/threonine pseudokinase identified as an oncogene, is expressed at high levels in the T-cell compartment of hematopoiesis. The proliferation of developing thymocytes is tightly controlled to prevent leukemic transformation of T cells. Here we examine Trib2 loss in murine hematopoiesis under steady state and proliferative stress conditions, including genotoxic and oncogenic stress. Trib2^−/− developing thymocytes show increased proliferation, and Trib2^−/− mice have significantly higher thymic cellularity at steady state. During stress hematopoiesis, Trib2^−/− developing thymocytes undergo accelerated proliferation and demonstrate hypersensitivity to 5-fluorouracil (5-FU)-induced cell death. Despite the increased cell death post 5-FU-induced proliferative stress, Trib2^−/− mice exhibit accelerated thymopoietic recovery post treatment due to increased cell division kinetics of developing thymocytes. The increased proliferation in Trib2^−/− thymocytes was exacerbated under oncogenic stress. In an experimental murine T-cell acute lymphoblastic leukemia (T-ALL) model, Trib2^−/− mice had reduced latency in vivo, which associated with impaired MAP kinase (MAPK) activation. High and low expression levels of Trib2 correlate with immature and mature subtypes of human T-ALL, respectively, and associate with MAPK. Thus, TRIB2 emerges as a novel regulator of thymocyte cellular proliferation, important for the thymopoietic response to genotoxic and oncogenic stress, and possessing tumor suppressor function.

Tribbles in inflammation

Inflammation is part of the physiological innate immune response to invading pathogens and tissue injury. However, unresolved inflammation leads to human disease. The tribbles (TRIB) family of pseudokinase proteins has been shown to modulate key inflammatory signalling pathways, including the MAPK (mitogen-activated protein kinase) and PI3K (phosphoinositide 3-kinase) networks. This review summarizes our current knowledge on TRIBs in the context of inflammation, both at the level of molecular mechanisms and in disease development.

Type 1 narcolepsy: a CD8(+) T cell-mediated disease?

Type 1 narcolepsy is a sleep disorder characterized by excessive daytime sleepiness with unintentional sleep attacks and cataplexy. The disorder is caused by a loss of hypocretinergic neurons in the brain. The specific loss of these neurons in narcolepsy is thought to result from an autoimmune attack, and this is supported by evidence of both environmental and genetic factors pointing toward an involvement of the immune system. However, definitive proof of an autoimmune etiology is still missing. Several different immune-mediated disorders targeting neurons are known, and many of these are believed to be caused by autoreactive CD8(+) T cells. In this paper, we review the current knowledge on CD8(+) T cell-mediated neuronal damage on the basis of our understanding of other autoimmune disorders and experimental studies. We identify major histocompatibility complex class I presentation of autoantigens on neurons as a possible mechanism in the development of the disease, and propose T cell-mediated pathogenesis, with cytotoxic CD8(+) T cells targeting the hypocretinergic neurons, as a central element.

Functional fingerprinting of human mesenchymal stem cells using high-throughput RNAi screening

Mesenchymal stem cells (MSCs) are promising candidates for cellular therapies ranging from tissue repair in regenerative medicine to immunomodulation in graft versus host disease after allogeneic transplantation or in autoimmune diseases. Nonetheless, progress has been hampered by their enormous phenotypic as well as functional heterogeneity and the lack of uniform standards and guidelines for quality control. In this study, we describe a method to perform cellular phenotyping by high-throughput RNA interference in primary human bone marrow MSCs. We have shown that despite heterogeneity of MSC populations, robust functional assays can be established that are suitable for high-throughput and high-content screening. We profiled primary human MSCs against human fibroblasts. Network analysis showed a kinome fingerprint that differs from human primary fibroblasts as well as fibroblast cell lines. In conclusion, this study shows that high-throughput screening in primary human MSCs can be reliably used for kinome fingerprinting.

Paeoniflorin abrogates DSS-induced colitis via a TLR4-dependent pathway

Paeonia lactiflora Pall is one of the most well-known herbs in China, Korea, and Japan for more than 1,200 years. Paeoniflorin, the major bioactive component of peony root, has recently been reported to have anticolitic activity. However, the underlying molecular mechanism is unclear. The present study was to explore the possible mechanism of paeoniflorin in attenuating dextran sulfate sodium (DSS)-induced colitis. Pre- and coadministration of paeoniflorin significantly reduced the severity of colitis and resulted in downregulation of several inflammatory parameters in the colon, including the activity of myeloperoxidase (MPO), the levels of TNF-α and IL-6, and the mRNA expression of proinflammatory mediators (MCP-1, Cox2, IFN-γ, TNF-α, IL-6, and IL-17). The decline in the activation of NF-κB p65, ERK, JNK, and p38 MAPK correlated with a decrease in mucosal Toll-like receptor 4 (TLR4) but not TLR2 or TLR5 expression. In accordance with the in vivo results, paeoniflorin downregulated TLR4 expression, blocked nuclear translocation of NF-κB p65, and reduced the production of IL-6 in LPS-stimulated mouse macrophage RAW264.7 cells. Transient transfection assay performed in LPS-stimulated human colon cancer HT-29 cells indicated that paeoniflorin inhibits NF-κB transcriptional activity in a dose-dependent manner. TLR4 knockdown and overexpression experiments demonstrated a requirement for TLR4 in paeoniflorin-mediated downregulation of inflammatory cytokines. Thus, for the first time, the present study indicates that paeoniflorin abrogates DSS-induced colitis via decreasing the expression of TLR4 and suppressing the activation of NF-κB and MAPK pathways.

The functionally diverse roles of tribbles

Tribbles are members of the pseudokinase family of proteins, with no associated kinase activity detectable to date. As tribbles appear not to function as kinases, there has been debate surrounding their functional classification. Tribbles have been proposed to function as adaptor molecules facilitating degradation of their target proteins. Tribbles have also been proposed to mediate signalling changes to MAPK (mitogen-activated protein kinase) cascades and also to function as decoy kinases interfering with the activity of known kinases. The present review discusses the functionally divergent roles of tribbles as molecular adaptors mediating degradation, changes to signalling cascades and action as decoy kinases.

Let-7c inhibits A549 cell proliferation through oncogenic TRIB2 related factors

MicroRNAs have tumor suppressive or oncogenic roles in carcinogenesis. This study aimed to investigate the mechanism of let-7c in suppressing lung cancer cell proliferation. First, let-7c was revealed to be able to inhibit lung adenocarcinoma cell proliferation significantly. TRIB2 was further demonstrated to be a novel target and negatively regulated by let-7c. As downstream signals of TRIB2, the activities of C/EBP-α and phosphorylated p38MAPK were increased obviously in let-7c-treated cells compared with controls. Our results demonstrate that, through regulating the expression of TRIB2 and its downstream factors, let-7c can effectively inhibit A549 cell proliferation in vitro and in vivo.

Different activation of TRAF4 and TRAF6 in inflammatory bowel disease

In recent years, interests combining the exploration of tumor necrosis factor receptor-associated factor 4 (TRAF4) and TRAF6 in immune cells and transgenic mice are emerging. Although it has been found that TRAF4 and TRAF6 share the same TRAF binding sites, comprehensive study of TRAF4 and TRAF6 in inflammatory bowel disease (IBD) is still lacking. This paper shows similar and different expression patterns of TRAF4 and TRAF6 in patients with IBD. The results indicate that TRAF4 and TRAF6 are overexpressed in IBD. TRAF4 and TRAF6 play different roles in the pathogenesis of IBD. Moreover, TRAF4 may be an indicator of endoscopic disease activity of UC and TRAF6 preactivation can be detected in noninflamed colonic segments.

Mammalian tribbles homologs at the crossroads of endoplasmic reticulum stress and Mammalian target of rapamycin pathways

In 2000, investigators discovered Tribbles, a Drosophila protein that coordinates morphogenesis by inhibiting mitosis. Further work has delineated Xenopus (Xtrb2), Nematode (Nipi-3), and mammalian homologs of Drosophila tribbles, which include TRB1, TRB2, and TRB3. The sequences of tribbles homologs are highly conserved, and despite their protein kinase structure, to date they have not been shown to have kinase activity. TRB family members play a role in the differentiation of macrophages, lymphocytes, muscle cells, adipocytes, and osteoblasts. TRB isoforms also coordinate a number of critical cellular processes including glucose and lipid metabolism, inflammation, cellular stress, survival, apoptosis, and tumorigenesis. TRB family members modulate multiple complex signaling networks including mitogen activated protein kinase cascades, protein kinase B/AKT signaling, mammalian target of rapamycin, and inflammatory pathways. The following review will discuss metazoan homologs of Drosophila tribbles, their structure, expression patterns, and functions. In particular, we will focus on TRB3 function in the kidney in podocytes. This review will also discuss the key signaling pathways with which tribbles proteins interact and provide a rationale for developing novel therapeutics that exploit these interactions to provide better treatment options for both acute and chronic kidney disease.