Signal Transducer Of Transcription Research Articles

Abstract 5408: SERPINB3 impact on cervical cancer cell mobility and migration

Abstract Cervical cancer is the fourth most common cancer in women, with 311,000 deaths worldwide in 2018. About two thirds of patients with cervical cancer exhibit elevated serum levels of squamous cell carcinoma antigen (SCCA), also known as SERPINB3. SERPINB3 is associated with advanced stage and lymph node metastasis and we have previously shown it has a protective role against radiation treatment and chemotherapy induced cell death. We have also shown that SERPINB3 promotes tumor growth in both immunocompromised and immune competent murine models, yet the molecular mechanism is unknown. We have recently shown that SERPINB3 expression results in activation of signal transducer of transcription 3 (STAT3) and extracellular signal regulated kinase (ERK) in cervical cancer cells. These signaling cascades promote cell proliferation, survival, invasion, and metastasis. Proximity labeling using biotin-ligase fused to SERPINB3 revealed STAT3 and ERK as potential interacting partners. We aim to identify the molecular mechanism by which SERPINB3 promotes tumor progression, and determine if SERPINB3 drives invasion and metastasis in-vivo. We hypothesized that SERPINB3 directly interacts with and activates STAT3 and ERK leading to downstream signaling promoting invasion and metastasis. To test this hypothesis, we used cervical tumor cell lines engineered with SERPINB3 or empty vector control and determined migration by wound healing assay and downstream activation of STAT3 and ERK. Co-immunoprecipitation (co-IP) with western blot was performed to determine an interaction between SERPINB3 and STAT3 and ERK. E6/E7-expressing TC-1, and Lewis Lung Carcinoma cells, LL2, to develop a method for injecting the cervix of immunocompetent c57BL/6 albino mice (no available murine cervical carcinoma line). Wound healing assays revealed that knocking out SERPINB3 shows a decrease in wound closure in both SW756 and HT3 cervical cancer cells compared to control cells, respectively. Co-IP of STAT3 in HT3 cells revealed the presence of SERPINB3, providing further evidence for an interaction between STAT3 and SERPINB3. We were able to grow tumors in the cervix of the C57/BL6 mice and identified potential metastatic deposits in the lung. Moving forward, we plan to identify the minimal functional domain of the interaction between SERPINB3 and STAT3/ERK using a step-wise genetic approach for protein domain deletion. To determine the role of SERPINB3 on metastasis in vivo, we will use, LL2 and TC-1 engineered with the mouse orthologue mSERPINB3a to determine effect of SERPINB3 on invasion and metastasis. Conducting this study will provide insights as to how SERPINB3 may function in a pro-tumor role in cervical cancer and allow the development of SERPINB3-targeted drugs. Citation Format: Marlene L. Campos Guerrero, Li-Yun Chen, Stephanie Markovina. SERPINB3 impact on cervical cancer cell mobility and migration [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5408.

English version of Japanese guidance for the use of oral Janus kinase inhibitors (JAK1 and TYK2 inhibitors) in the treatments of psoriasis.

This is the English version of Japanese guidance for the use of oral Janus kinase (JAK) inhibitors (JAK1 and tyrosine kinase 2 [TYK2] inhibitors) in the treatments of psoriasis. Several cytokines, such as interleukin (IL)-6, IL-7, IL-12, IL-21, IL-22, IL-23, interferon (IFN)-α, and IFN-γ, are involved in the pathogenesis of psoriasis (including psoriatic arthritis). As oral JAK inhibitors hinder the JAK-signal transducers and activators of transcription signal transduction routes involved in the signal transduction of these cytokines, they may be effective for the treatment of psoriasis. JAK has four types: JAK1, JAK2, JAK3, and TYK2. Regarding the use of oral JAK inhibitors for the treatment of psoriasis in Japan, indications of the JAK1 inhibitor upadacitinib were extended also to psoriatic arthritis in 2021, and the use of the TYK2 inhibitor deucravacitinib for plaque-type psoriasis, pustular psoriasis, and erythrodermic psoriasis became covered by health insurance in 2022. This guidance was developed for board-certified dermatologists who specialize in the treatment of psoriasis and to promote the proper use of oral JAK inhibitors. In the package inserts and guides for appropriate use, upadacitinib and deucravacitinib are classified as a "JAK inhibitor" and a "TYK2 inhibitor", respectively, and it is possible that there may be differences in safety between the two drugs. The safety of these drugs will be evaluated for the future by the postmarketing surveillance for molecularly targeted drugs for psoriasis of the Japanese Dermatological Association.

English version of Japanese guidance for the use of oral Janus kinase (JAK) inhibitors in the treatments of atopic dermatitis.

This is the English version of guidance for the use of oral Janus kinase (JAK) inhibitors in the treatment of atopic dermatitis. Several cytokines, such as interleukin (IL)-4, IL-13, IL-22, IL-31, thymic stromal lymphopoietin, and interferon-γ, are involved in the pathogenesis of atopic dermatitis. As oral JAK inhibitors hinder the JAK-signal transducers and activators of transcription signal transduction routes involved in the signal transduction of these cytokines, they may be effective for the treatment of atopic dermatitis. In Japan, as oral JAK inhibitors for atopic dermatitis, a JAK1/2 inhibitor, baricitinib, expanded its authorized indications for atopic dermatitis in 2020. Consequentially, a JAK1 inhibitor, upadacitinib, also expanded its indications to atopic dermatitis in 2021, followed by new approval of another JAK1 inhibitor, abrocitinib, for the use under the Japanese health insurance system. Physicians who intend to use them should sufficiently understand and comply with contents of guidelines prepared by the Japanese Ministry of Health, Labour and Welfare to promote optimal use of these drugs. In the treatment with oral JAK inhibitors, it is important to sufficiently consider disease factors, treatment factors and patient backgrounds, and share them with patients to choose treatment options. Points to be considered for drug selection include the efficacy and safety of drugs, age of patients, and dosage and administration of the drug. This guidance was developed for board certified dermatologists, who are specialized in the treatment of atopic dermatitis, and for promoting proper use of oral JAK inhibitors, taking into account a variety of factors in individual patients.

Recent research on tofacitinib in the treatment of pediatric rheumatic diseases

Tofacitinib is a Janus kinase inhibitor and can block the Janus kinase-signal transducer and activator of transcription signal transduction pathway and reduce the production and release of a variety of cytokines. It has great potential in the treatment of various rheumatic diseases with a rapid onset of action and can reduce corticosteroid dependence and related adverse events. The therapeutic effect of tofacitinib in adult patients has been confirmed, and it has been increasingly used in pediatric patients in recent years. This article reviews the clinical application of tofacitinib in the treatment of pediatric autoimmune diseases.

Comparative transcriptome and metabolome analysis reveal glutathione metabolic network and functional genes underlying blue and red-light mediation in maize seedling leaf

BackgroundLight quality severely affects biosynthesis and metabolism-associated process of glutathione. However, the role of specific light is still unclear on the glutathione metabolism. In this article, comparatively transcriptome and metabolome methods are used to fully understand the blue and red-light conditions working on the glutathione metabolism in maize seedling leaf.ResultsThere are 20 differently expressed genes and 4 differently expressed metabolites in KEGG pathway of glutathione metabolism. Among them, 12 genes belong to the glutathione S-transferase family, 3 genes belong to the ascorbate peroxidase gene family and 2 genes belong to the ribonucleoside-diphosphate reductase gene family. Three genes, G6PD, SPDS1, and GPX1 belong to the gene family of glucose 6-phosphate dehydrogenase, spermidine synthase, and glutathione peroxidase, respectively. Four differently expressed metabolites are identified. Three of them, Glutathione disulfide, Glutathione, and l-γ-Glutamyl-L-amino acid are decreased while L-Glutamate is increased. In addition, Through PPI analysis, two annotated genes gst16 and DAAT, and 3 unidentified genes 100381533, pco105094 and umc2770, identified as RPP13-like3, BCAT-like1and GMPS, were obtained. By the analysis of protein sequence and PPI network, we predict that pco105094 and umc2770 were involved in the GSSG-GSH and AsA-GSH cycle in the network of glutathione metabolism.ConclusionsCompared to red light, blue light remarkably changed the transcription signal transduction and metabolism of glutathione metabolism. Differently expressed genes and metabolic mapped to the glutathione metabolism signaling pathways. In total, we obtained three unidentified genes, and two of them were predicted in current glutathione metabolism network. This result will contribute to the research of glutathione metabolism of maize.

(20S) Ginsenoside Rh2 Inhibits STAT3/VEGF Signaling by Targeting Annexin A2

Signal transducers and activators of transcription 3 (STAT3) acts as a transcriptional signal transducer, converting cytokine stimulation into specific gene expression. In tumor cells, aberrant activation of the tyrosine kinase pathway leads to excessive and continuous activation of STAT3, which provides further signals for tumor cell growth and surrounding angiogenesis. In this process, the tumor-associated protein Annexin A2 interacts with STAT3 and promotes Tyr705 phosphorylation and STAT3 transcriptional activation. In this study, we found that (20S) ginsenoside Rh2 (G-Rh2), a natural compound inhibitor of Annexin A2, inhibited STAT3 activity in HepG2 cells. (20S) G-Rh2 interfered with the interaction between Annexin A2 and STAT3, and inhibited Tyr705 phosphorylation and subsequent transcriptional activity. The inhibitory activity of STAT3 leaded to the negative regulation of the four VEGFs, which significantly reduced the enhanced growth and migration ability of HUVECs in co-culture system. In addition, (20S)G-Rh2 failed to inhibit STAT3 activity in cells overexpressing (20S)G-Rh2 binding-deficient Annexin A2-K301A mutant, further proving Annexin A2-mediated inhibition of STAT3 by (20S)G-Rh2. These results indicate that (20S)G-Rh2 is a potent inhibitor of STAT3, predicting the potential activity of (20S)G-Rh2 in targeted therapy applications.

Transcriptome and Metabolomic Analyses Reveal Regulatory Networks Controlling Maize Stomatal Development in Response to Blue Light.

(1) Background: Blue light is important for the formation of maize stomata, but the signal network remains unclear. (2) Methods: We replaced red light with blue light in an experiment and provided a complementary regulatory network for the stomatal development of maize by using transcriptome and metabolomics analysis. (3) Results: Exposure to blue light led to 1296 differentially expressed genes and 419 differential metabolites. Transcriptome comparisons and correlation signaling network analysis detected 55 genes, and identified 6 genes that work in the regulation of the HY5 module and MAPK cascade, that interact with PTI1, COI1, MPK2, and MPK3, in response to the substitution of blue light in environmental adaptation and signaling transduction pathways. Metabolomics analysis showed that two genes involved in carotenoid biosynthesis and starch and sucrose metabolism participate in stomatal development. Their signaling sites located on the PHI1 and MPK2 sites of the MAPK cascade respond to blue light signaling. (4) Conclusions: Blue light remarkably changed the transcriptional signal transduction and metabolism of metabolites, and eight obtained genes worked in the HY5 module and MAPK cascade.

STAT1 N-terminal domain discriminatively controls type I and type II IFN signaling

The seven signal transducers of transcription (STATs) are cytokine-inducible modular transcription factors. They transmit the stimulation of cells with type I interferons (IFN-α/IFN-β) and type II interferon (IFN-ɣ) into altered gene expression patterns. The N-terminal domain (NTD) of STAT1 is a surface for STAT1/STAT1 homodimer and STAT1/STAT2 heterodimer formation and allows the cooperative DNA binding of STAT1. We investigated whether the STAT1 NTD-mediated dimerization affected the IFN-induced tyrosine phosphorylation of STAT1, its nuclear translocation, STAT1-dependent gene expression, and IFN-dependent antiviral defense. We reconstituted human STAT1-negative and STAT2-negative fibrosarcoma cells with STAT1, NTD-mutated STAT1 (STAT1AA), STAT1 with a mutated DNA-binding domain (DBD), or STAT2. We treated these cells with IFN-α and IFN-ɣ to assess differences between IFN-α-induced STAT1 homo- and heterodimers and IFN-ɣ-induced STAT1 homodimers. Our data demonstrate that IFNs induce the phosphorylation of STAT1 and STAT1AA at Y701 and their nuclear accumulation. We further reveal that STAT1AA can be phosphorylated in response to IFN-α in the absence of STAT2 and that IFN-ɣ-induced STAT1AA can activate gene expression directly. However, STAT1AA largely fails to bind STAT2 and to activate IFN-α-induced expression of endogenous antiviral STAT1/STAT2 target proteins. Congruent herewith, both an intact STAT1 NTD and STAT2 are indispensable to establish an antiviral state with IFN-α. These data provide new insights into the biological importance of the STAT1 NTD.

In Vitro and In Vivo Anti-Allergic and Anti-Inflammatory Effects of eBV, a Newly Developed Derivative of Bee Venom, through Modulation of IRF3 Signaling Pathway in a Carrageenan-Induced Edema Model.

BackgroundBee venom (BV), a type of toxin extracted from honeybees (Apis mellifera), has been empirically and widely used to treat inflammatory diseases throughout Asia. Essential BV (eBV) was developed by removing phospholipase A2 (PLA2) and histamine to lower occurrence of allergic reaction. This study investigated the anti-allergic and anti-inflammatory activities of eBV in vitro and in vivo and its underlying mechanism of action.MethodsThe anti-inflammatory potential of eBV was assessed in vivo using a carrageenan-induced paw edema model. To further investigate the mechanism by which eBV exerts anti-allergic and anti-inflammatory effects, compound 48/80-stimulated RBL-2H3 cells and lipopolysaccharide (LPS)-stimulated RAW 264.7 murine macrophage cells were studied in vitro.ResultsRelease of β-hexosaminidase and histamine was increased by eBV in a dose-dependent manner, but these levels were lower in eBV compared to original BV at the same concentration. In addition, eBV suppressed compound 48/80-induced expression of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in RBL-2H3 cells. eBV was also shown to suppress nitric oxide (NO) production by down-regulating mRNA expression and subsequent protein expression of inflammatory mediators in LPS-induced RAW 264.7 cells. Phosphorylation of activators and signal transducers of transcription 1/interferon regulatory factor 3 (STAT1/IRF3) was attenuated by eBV treatment. eBV significantly inhibited carrageenan-induced acute edema in vivo. Serum levels of prostaglandin E2 (PGE2), TNF-α, and IL-1β were also down-regulated by eBV.ConclusionsThese results demonstrate that eBV inhibits allergic and inflammatory response by reducing inflammatory mediator production via regulation of the STAT1/IRF3 signaling pathway, suggesting that eBV is a feasible candidate for regulation of allergic-inflammatory response in complementary and alternative medicine.

Novel transcripts from a distinct promoter that encode the full-length AKT1 in human breast cancer cells

BackgroundThe serine-threonine kinase AKT1 plays essential roles during normal mammary gland development as well as the initiation and progression of breast cancer. AKT1 is generally considered a ubiquitously expressed gene, and its persistent activation is transcriptionally controlled by regulatory elements characteristic of housekeeping gene promoters. We recently identified a novel Akt1 transcript in mice (Akt1m), which is induced by growth factors and their signal transducers of transcription from a previously unknown promoter. The purpose of this study was to examine whether normal and neoplastic human breast epithelial cells express an orthologous AKT1m transcript and whether its expression is deregulated in cancer cells.MethodsInitial sequence analyses were performed using the UCSC Genome Browser and GenBank to assess the potential occurrence of an AKT1m transcript variant in human cells and to identify conserved promoter sequences that are orthologous to the murine Akt1m. Quantitative RT-PCR was used to determine the transcriptional activation of AKT1m in mouse mammary tumors as well as 41 normal and neoplastic human breast epithelial cell lines and selected primary breast cancers.ResultsWe identified four new AKT1 transcript variants in human breast cancer cells that are orthologous to the murine Akt1m and that encode the full-length kinase. These transcripts originate from an alternative promoter that is conserved between humans and mice. Akt1m is upregulated in the majority of luminal-type and basal-type mammary cancers in four different genetically engineered mouse models. Similarly, a subset of human breast cancer cell lines and primary breast cancers exhibited a higher expression of orthologous AKT1m transcripts.ConclusionsThe existence of an alternative promoter that drives the expression of the unique AKT1m transcript may provide a mechanism by which the levels of AKT1 can be temporally and spatially regulated at particular physiological states, such as cancer, where a heightened activity of this kinase is required.

Integrated cistromic and expression analysis of amplified NKX2-1 in lung adenocarcinoma identifies LMO3 as a functional transcriptional target

The NKX2-1 transcription factor, a regulator of normal lung development, is the most significantly amplified gene in human lung adenocarcinoma. To study the transcriptional impact of NKX2-1 amplification, we generated an expression signature associated with NKX2-1 amplification in human lung adenocarcinoma and analyzed DNA-binding sites of NKX2-1 by genome-wide chromatin immunoprecipitation. Integration of these expression and cistromic analyses identified LMO3, itself encoding a transcription regulator, as a candidate direct transcriptional target of NKX2-1. Further cistromic and overexpression analyses indicated that NKX2-1 can cooperate with the forkhead box transcription factor FOXA1 to regulate LMO3 gene expression. RNAi analysis of NKX2-1-amplified cells compared with nonamplified cells demonstrated that LMO3 mediates cell survival downstream from NKX2-1. Our findings provide new insight into the transcriptional regulatory network of NKX2-1 and suggest that LMO3 is a transcriptional signal transducer in NKX2-1-amplified lung adenocarcinomas.

Pasteurella multocida Toxin-induced Pim-1 expression disrupts suppressor of cytokine signalling (SOCS)-1 activity

Pasteurella multocida Toxin (PMT) is a mitogenic protein toxin that manipulates signal transduction cascades of mammalian host cells and upregulates Janus kinase (JAK) and signal transducers of transcription (STAT) activity. Here we show that in the presence of PMT, increased levels of suppressors of cytokine signalling-1 (SOCS-1) proteins significantly enhance STAT activity. This occurs via PMT-induced expression of the serine/threonine kinase Pim-1 and subsequent threonine phosphorylation of SOCS-1. The ability of SOCS-1 to act as an E3 ubiquitin ligase is regulated by its phosphorylation status. Thus, the tyrosine kinase JAK2 cannot be marked for proteasomal degradation by threonine phosphorylated SOCS-1. Consequently, the expression levels of JAK2 are increased, eventually leading to hyperactivity of JAK2 and its target, the transcription factor STAT3. Eventually this causes increased anchorage-independent cell growth that correlates with the expression levels of SOCS-1. Interestingly, endogenous SOCS-1 production after Toll-like receptor activation also causes STAT3 hyperactivation. Thus we hypothesize that P. multocida Toxin alters host cell signalling using mechanisms that have so far only been known to be employed by oncogenic viral kinases to avoid host immune defence mechanisms.

Transcriptional profiles of drought-responsive genes in modulating transcription signal transduction, and biochemical pathways in tomato

To unravel the molecular mechanisms of drought responses in tomato, gene expression profiles of two drought-tolerant lines identified from a population of Solanum pennellii introgression lines, and the recurrent parent S. lycopersicum cv. M82, a drought-sensitive cultivar, were investigated under drought stress using tomato microarrays. Around 400 genes identified were responsive to drought stress only in the drought-tolerant lines. These changes in genes expression are most likely caused by the two inserted chromosome segments of S. pennellii, which possibly contain drought-tolerance quantitative trait loci (QTLs). Among these genes are a number of transcription factors and signalling proteins which could be global regulators involved in the tomato responses to drought stress. Genes involved in organism growth and development processes were also specifically regulated by drought stress, including those controlling cell wall structure, wax biosynthesis, and plant height. Moreover, key enzymes in the pathways of gluconeogenesis (fructose-bisphosphate aldolase), purine and pyrimidine nucleotide biosynthesis (adenylate kinase), tryptophan degradation (aldehyde oxidase), starch degradation (β-amylase), methionine biosynthesis (cystathionine β-lyase), and the removal of superoxide radicals (catalase) were also specifically affected by drought stress. These results indicated that tomato plants could adapt to water-deficit conditions through decreasing energy dissipation, increasing ATP energy provision, and reducing oxidative damage. The drought-responsive genes identified in this study could provide further information for understanding the mechanisms of drought tolerance in tomato.

Identification of Drosophila Genes Modulating Janus Kinase/Signal Transducer and Activator of Transcription Signal Transduction

The JAK/STAT pathway was first identified in mammals as a signaling mechanism central to hematopoiesis and has since been shown to exert a wide range of pleiotropic effects on multiple developmental processes. Its inappropriate activation is also implicated in the development of numerous human malignancies, especially those derived from hematopoietic lineages. The JAK/STAT signaling cascade has been conserved through evolution and although the pathway identified in Drosophila has been closely examined, the full complement of genes required to correctly transduce signaling in vivo remains to be identified. We have used a dosage-sensitive dominant eye overgrowth phenotype caused by ectopic activation of the JAK/STAT pathway to screen 2267 independent, newly generated mutagenic P-element insertions. After multiple rounds of retesting, 23 interacting loci that represent genes not previously known to interact with JAK/STAT signaling have been identified. Analysis of these genes has identified three signal transduction pathways, seven potential components of the pathway itself, and six putative downstream pathway target genes. The use of forward genetics to identify loci and reverse genetic approaches to characterize them has allowed us to assemble a collection of genes whose products represent novel components and regulators of this important signal transduction cascade.

Inadequacy of the Janus Kinase 2/Signal Transducer and Activator of Transcription Signal Transduction Pathway to Mediate Episodic Growth Hormone-Dependent Regulation of Hepatic CYP2C11

CYP2C11, the most commonly expressed hepatic cytochrome P450 isoform in male rats, is induced by the masculine "episodic" secretory growth hormone profile. A considerable number of reports have indicated that episodic growth hormone effects are mediated by the activation of the Janus kinase 2 (Jak2)/signal transducer and activator of transcription (Stat)5B signal transduction pathway. We observed that restoration of the normal masculine plasma growth hormone pulse in hypophysectomized male rats did indeed rapidly activate (phosphorylate) Jak2, shortly followed by activation and nuclear translocation of Stat5B. Infusion of a growth hormone pulse with an amplitude that was 10% of the normal height induced a dramatic overexpression of CYP2C11, had little effect activating Jak2, but induced a more rapid and greater accumulation of activated nuclear Stat5B. Restoration of a growth hormone pulse with an amplitude of only 1% of normal had little effect phosphorylating Jak2, activated and translocated to the hepatic nucleus approximately 70% of the normally induced levels of Stat5B, but had no inductive effect on CYP2C11. Last, the hypophysectomized male rat receiving no growth hormone replacement expressed 25 to 35% of normal concentrations of CYP2C11 despite no measurable activation of either Jak2 or Stat5B. These results raise concerns regarding the requisite role of the Jak2/Stat5B pathway in mediating episodic growth hormone regulation of CYP2C11. However, accumulation of activated extracellular signal-regulated kinase (ERK)1 and ERK2 were the only transducers measured in the study not affected by the 1% replacement pulse of growth hormone and were elevated 2- to 3-fold above normal when the pulse was renaturalized to 10% of physiological amplitude, suggesting the possible involvement of mitogen-activated protein kinase in episodic growth hormone regulation of CYP2C11.

Leptin enhances oocyte nuclear and cytoplasmic maturation via the mitogen-activated protein kinase pathway.

Recent studies have suggested that leptin has a central role in female reproduction, including ovarian function. The leptin receptor (Ob-R) has six isoforms and can signal through either the MAPK or the Janus-activated kinase/signal transducer and activator of transcription signal-transduction pathway, depending on the isoform. Expression of Ob-R has been reported in human and mouse oocytes; however, the physiological role of leptin during follicular development and oocyte maturation is largely unknown. In the current study, expression of Ob-R during oocyte growth and maturation was investigated in porcine oocytes from small, medium, and large follicles and in oocytes in the germinal vesicle (GV), GV breakdown, and metaphase II (MII) stages at both the mRNA and protein levels. The proportion of oocytes expressing Ob-R was maximal in oocytes from medium follicles and at the GV breakdown stage (P < 0.05), whereas the proportion of oocytes expressing the long isoform, Ob-Rb, was found to be consistently low throughout growth and maturation. When included in oocyte maturation medium, leptin significantly increased the proportion of oocytes reaching MII (P < 0.01), elevated cyclin B1 protein content in MII-stage oocytes (P < 0.05), and enhanced embryo developmental potential (P < 0.05), suggesting that leptin plays a role in both nuclear and cytoplasmic maturation. During oocyte maturation, leptin increased phosphorylated MAPK content by 2.8-fold (P < 0.05), and leptin-stimulated oocyte maturation was blocked when leptin-induced MAPK phosphorylation was suppressed by a specific MAPK activation inhibitor, U0126 (P < 0.01), demonstrating that leptin enhances nuclear maturation via activation of the MAPK pathway.

Inactivation of SSI-1, a JAK/STAT inhibitor, in human hepatocellular carcinomas, as revealed by two-dimensional electrophoresis

Background/Aims: Hepatocellular carcinoma (HCC) is one of the most common human cancers, and many efforts have been paid to discover aberrant expression control in HCC, however the specific molecular mechanisms involved in hepatocarcinogenesis remain to be determined.Methods: To investigate genomic changes that occur in human primary hepatocellular carcinomas (HCC), we carried out restriction landmark genomic scanning. This two-dimensional electrophoretic system displays 2000–3000 NotI-landmark sites in a single gel.Results: We detected one landmark spot that showed diminished signal intensities in a majority of the HCCs we examined. Cloning revealed that this spot represented a NotI-cluster sequence that was enriched with CpG dinucleotides in the promoter region of a gene encoding Janus kinase (JAK)-binding protein, SSI-1 (also known as JAB1 or SOCS-1). Expression of the SSI-1 gene was markedly reduced in half of eight HCCs analyzed.Conclusions: This protein regulates the Janus kinase signal transducers and activators of transcription signal transduction pathway, which transmits signals from cytokines to the intracellular apparatus. These data suggest that dysregulation of the pathway relate with progression of HCC.

Substrate specificity and signal transduction pathways in the glucose-specific enzyme II (EII(Glc)) component of the Escherichia coli phosphotransferase system.

Escherichia coli adapted to glucose-limited chemostats contained mutations in ptsG resulting in V12G, V12F, and G13C substitutions in glucose-specific enzyme II (EII(Glc)) and resulting in increased transport of glucose and methyl-alpha-glucoside. The mutations also resulted in faster growth on mannose and glucosamine in a PtsG-dependent manner. By use of enhanced growth on glucosamine for selection, four further sites were identified where substitutions caused broadened substrate specificity (G176D, A288V, G320S, and P384R). The altered amino acids include residues previously identified as changing the uptake of ribose, fructose, and mannitol. The mutations belonged to two classes. First, at two sites, changes affected transmembrane residues (A288V and G320S), probably altering sugar selectivity directly. More remarkably, the five other specificity mutations affected residues unlikely to be in transmembrane segments and were additionally associated with increased ptsG transcription in the absence of glucose. Increased expression of wild-type EII(Glc) was not by itself sufficient for growth with other sugars. A model is proposed in which the protein conformation determining sugar accessibility is linked to transcriptional signal transduction in EII(Glc). The conformation of EII(Glc) elicited by either glucose transport in the wild-type protein or permanently altered conformation in the second category of mutants results in altered signal transduction and interaction with a regulator, probably Mlc, controlling the transcription of pts genes.