MIG-6 negatively regulates STAT3 phosphorylation in uterine epithelial cells

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Yoo, Jung-Yoon; Yang, Woo Sub; Lee, Jae Hee; Kim, Byung Gak; Broaddus, Russell R.; Lim, Jeong M.; Kim, Tae Hoon; Jeong, Jae-Wook

2017-01-01

Endometrial cancer is the most common malignancy of the female genital tract. Progesterone (P4) has been used for several decades in endometrial cancer treatment, especially in women who wish to retain fertility. However, it is unpredictable which patients will respond to P4 treatment and which may have a P4 resistant cancer. Therefore, identifying the mechanism of P4 resistance is essential to improve the therapies for endometrial cancer. Mitogen-inducible gene 6 (Mig-6) is a critical mediator of progesterone receptor (PGR) action in the uterus. In order to study the function of Mig-6 in P4 resistance, we generated a mouse model in which we specifically ablated Mig-6 in uterine epithelial cells using Sprr2f-cre mice (Sprr2fcre+Mig-6f/f). Female mutant mice develop endometrial hyperplasia due to aberrant phosphorylation of STAT3 and proliferation of the endometrial epithelial cells. The results from our immunoprecipitation and cell culture experiments showed that MIG-6 inhibited phosphorylation of STAT3 via protein interactions. Our previous study showed P4 resistance in mice with Mig-6 ablation in Pgr positive cells (Pgrcre/+Mig-6f/f). However, Sprr2fcre+Mig-6f/f mice were P4 responsive. P4 treatment significantly decreased STAT3 phosphorylation and epithelial proliferation in the uterus of mutant mice. We showed that Mig-6 has an important function of tumor suppressor via inhibition of STAT3 phosphorylation in uterine epithelial cells and the anti-tumor effects of P4 are mediated by the endometrial stroma. This data helps to develop a new signaling pathway in the regulation of steroid hormones in the uterus, and to overcome P4 resistance in human reproductive diseases, such as endometrial cancer. PMID:28925396

A role for the JAK-STAT1 pathway in blocking replication of HSV-1 in dendritic cells and macrophages

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Town Terrence

2009-05-01

Full Text Available Abstract Background Macrophages and dendritic cells (DCs play key roles in host defense against HSV-1 infection. Although macrophages and DCs can be infected by herpes simplex virus type 1 (HSV-1, both cell types are resistant to HSV-1 replication. The aim of our study was to determine factor (s that are involved in the resistance of DCs and macrophages to productive HSV-1 infection. Results We report here that, in contrast to bone marrow-derived DCs and macrophages from wild type mice, DCs and macrophages isolated from signal transducers and activators of transcription-1 deficient (STAT1-/- mice were susceptible to HSV-1 replication and the production of viral mRNAs and DNA. There were differences in expression of immediate early, early, and late gene transcripts between STAT1+/+ and STAT1-/- infected APCs. Conclusion These results suggest for the first time that the JAK-STAT1 pathway is involved in blocking replication of HSV-1 in DCs and macrophages.

A role for the JAK-STAT1 pathway in blocking replication of HSV-1 in dendritic cells and macrophages

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Mott, Kevin R; UnderHill, David; Wechsler, Steven L; Town, Terrence; Ghiasi, Homayon

2009-01-01

Background Macrophages and dendritic cells (DCs) play key roles in host defense against HSV-1 infection. Although macrophages and DCs can be infected by herpes simplex virus type 1 (HSV-1), both cell types are resistant to HSV-1 replication. The aim of our study was to determine factor (s) that are involved in the resistance of DCs and macrophages to productive HSV-1 infection. Results We report here that, in contrast to bone marrow-derived DCs and macrophages from wild type mice, DCs and macrophages isolated from signal transducers and activators of transcription-1 deficient (STAT1-/-) mice were susceptible to HSV-1 replication and the production of viral mRNAs and DNA. There were differences in expression of immediate early, early, and late gene transcripts between STAT1+/+ and STAT1-/- infected APCs. Conclusion These results suggest for the first time that the JAK-STAT1 pathway is involved in blocking replication of HSV-1 in DCs and macrophages. PMID:19439086

Monoclonal Antibodies Specific for STAT3β Reveal Its Contribution to Constitutive STAT3 Phosphorylation in Breast Cancer

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Uddalak Bharadwaj

2014-09-01

Full Text Available Since its discovery in mice and humans 19 years ago, the contribution of alternatively spliced Stat3, Stat3β, to the overall functions of Stat3 has been controversial. Tyrosine-phosphorylated (p Stat3β homodimers are more stable, bind DNA more avidly, are less susceptible to dephosphorylation, and exhibit distinct intracellular dynamics, most notably markedly prolonged nuclear retention, compared to pStat3α homodimers. Overexpression of one or the other isoform in cell lines demonstrated that Stat3β acted as a dominant-negative of Stat3α in transformation assays; however, studies with mouse strains deficient in one or the other isoform indicated distinct contributions of Stat3 isoforms to inflammation. Current immunological reagents cannot differentiate Stat3β proteins derived from alternative splicing vs. proteolytic cleavage of Stat3α. We developed monoclonal antibodies that recognize the 7 C-terminal amino acids unique to Stat3β (CT7 and do not cross-react with Stat3α. Immunoblotting studies revealed that levels of Stat3β protein, but not Stat3α, in breast cancer cell lines positively correlated with overall pStat3 levels, suggesting that Stat3β may contribute to constitutive Stat3 activation in this tumor system. The ability to unambiguously discriminate splice alternative Stat3β from proteolytic Stat3β and Stat3α will provide new insights into the contribution of Stat3β vs. Stat3α to oncogenesis, as well as other biological and pathological processes.

PTP1B is a negative regulator of interleukin 4–induced STAT6 signaling

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Lu, Xiaoqing; Malumbres, Raquel; Shields, Benjamin; Jiang, Xiaoyu; Sarosiek, Kristopher A.; Natkunam, Yasodha

2008-01-01

Protein tyrosine phosphatase 1B (PTP1B) is a ubiquitously expressed enzyme shown to negatively regulate multiple tyrosine phosphorylation-dependent signaling pathways. PTP1B can modulate cytokine signaling pathways by dephosphorylating JAK2, TYK2, and STAT5a/b. Herein, we report that phosphorylated STAT6 may serve as a cytoplasmic substrate for PTP1B. Overexpression of PTP1B led to STAT6 dephosphorylation and the suppression of STAT6 transcriptional activity, whereas PTP1B knockdown or deficiency augmented IL-4–induced STAT6 signaling. Pretreatment of these cells with the PTK inhibitor staurosporine led to sustained STAT6 phosphorylation consistent with STAT6 serving as a direct substrate of PTP1B. Furthermore, PTP1B-D181A “substrate-trapping” mutants formed stable complexes with phosphorylated STAT6 in a cellular context and endogenous PTP1B and STAT6 interacted in an interleukin 4 (IL-4)–inducible manner. We delineate a new negative regulatory loop of IL-4–JAK-STAT6 signaling. We demonstrate that IL-4 induces PTP1B mRNA expression in a phosphatidylinositol 3-kinase–dependent manner and enhances PTP1B protein stability to suppress IL-4–induced STAT6 signaling. Finally, we show that PTP1B expression may be preferentially elevated in activated B cell–like diffuse large B-cell lymphomas. These observations identify a novel regulatory loop for the regulation of IL-4–induced STAT6 signaling that may have important implications in both neoplastic and inflammatory processes. PMID:18716132

Mutually exclusive STAT1 modifications identified by Ubc9/substrate dimerization-dependent SUMOylation.

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Zimnik, Susan; Gaestel, Matthias; Niedenthal, Rainer

2009-03-01

Post-translational modifications control the physiological activity of the signal transducer and activator of transcription STAT1. While phosphorylation at tyrosine Y701 is a prerequisite for STAT1 dimerization, its SUMOylation represses the transcriptional activity. Recently, we have demonstrated that SUMOylation at lysine K703 inhibits the phosphorylation of nearby localized Y701 of STAT1. Here, we analysed the influence of phosphorylation of Y701 on SUMOylation of K703 in vivo. For that reason, an Ubc9/substrate dimerization-dependent SUMOylation (USDDS) system was developed, which consists of fusions of the SUMOylation substrate and of the SUMO-conjugating enzyme Ubc9 to the chemically activatable heterodimerization domains FKBP and FRB, respectively. When FKBP fusion proteins of STAT1, p53, CRSP9, FOS, CSNK2B, HES1, TCF21 and MYF6 are coexpressed with Ubc9-FRB, treatment of HEK293 cells with the rapamycin-related dimerizer compound AP21967 induces SUMOylation of these proteins in vivo. For STAT1-FKBP and p53-FKBP we show that this SUMOylation takes place at their specific SUMOylation sites in vivo. Using USDDS, we then demonstrate that STAT1 phosphorylation at Y701 induced by interferon-beta treatment inhibits SUMOylation of K703 in vivo. Thus, pY701 and SUMO-K703 of STAT1 represent mutually exclusive modifications, which prevent signal integration at this molecule and probably ensure the existence of differentially modified subpopulations of STAT1 necessary for its regulated nuclear cytoplasmic activation/inactivation cycle.

Decreased STAT3 Phosphorylation Mediates Cell Swelling in Ammonia-Treated Astrocyte Cultures

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Arumugam R. Jayakumar

2016-12-01

Full Text Available Brain edema, due largely to astrocyte swelling, and the subsequent increase in intracranial pressure and brain herniation, are major complications of acute liver failure (ALF. Elevated level of brain ammonia has been strongly implicated in the development of astrocyte swelling associated with ALF. The means by which ammonia brings about astrocyte swelling, however, is incompletely understood. Recently, oxidative/nitrosative stress and associated signaling events, including activation of mitogen-activated protein kinases (MAPKs, as well as activation of the transcription factor, nuclear factor-kappaB (NF-κB, have been implicated in the mechanism of ammonia-induced astrocyte swelling. Since these signaling events are known to be regulated by the transcription factor, signal transducer and activator of transcription 3 (STAT3, we examined the state of STAT3 activation in ammonia-treated cultured astrocytes, and determined whether altered STAT3 activation and/or protein expression contribute to the ammonia-induced astrocyte swelling. STAT3 was found to be dephosphorylated (inactivated at Tyrosine705 in ammonia-treated cultured astrocytes. Total STAT3 protein level was also reduced in ammonia-treated astrocytes. We also found a significant increase in protein tyrosine phosphatase receptor type-1 (PTPRT-1 protein expression in ammonia-treated cultured astrocytes, and that inhibition of PTPRT-1 enhanced the phosphorylation of STAT3 after ammonia treatment. Additionally, exposure of cultured astrocytes to inhibitors of protein tyrosine phosphatases diminished the ammonia-induced cell swelling, while cultured astrocytes over-expressing STAT3 showed a reduction in the astrocyte swelling induced by ammonia. Collectively, these studies strongly suggest that inactivation of STAT3 represents a critical event in the mechanism of the astrocyte swelling associated with acute liver failure.

HIV-1 Promotes the Degradation of Components of the Type 1 IFN JAK/STAT Pathway and Blocks Anti-viral ISG Induction.

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Gargan, Siobhan; Ahmed, Suaad; Mahony, Rebecca; Bannan, Ciaran; Napoletano, Silvia; O'Farrelly, Cliona; Borrow, Persephone; Bergin, Colm; Stevenson, Nigel J

2018-04-01

Anti-retroviral therapy successfully suppresses HIV-1 infection, but fails to provide a cure. During infection Type 1 IFNs normally play an essential role in viral clearance, but in vivo IFN-α only has a modest impact on HIV-1 infection, suggesting its possible targeting by HIV. Here, we report that the HIV protein, Vif, inhibits effective IFN-α signalling via degradation of essential JAK/STAT pathway components. We found that STAT1 and STAT3 are specifically reduced in HEK293T cells expressing Vif and that full length, infectious HIV-1 IIIB strain promotes their degradation in a Vif-dependent manner. HIV-1 IIIB infection of myeloid ThP-1 cells also reduced the IFN-α-mediated induction of the anti-viral gene, ISG15, but not MxA, revealing a functional consequence of this HIV-1-mediated immune evasion strategy. Interestingly, while total STAT levels were not reduced upon in vitro IIIB infection of primary human PBMCs, IFN-α-mediated phosphorylation of STAT1 and STAT3 and ISG induction were starkly reduced, with removal of Vif (IIIBΔVif), partially restoring pSTATs, ISG15 and MxB induction. Similarly, pSTAT1 and pSTAT3 expression and IFN-α-induced ISG15 were reduced in PBMCs from HIV-infected patients, compared to healthy controls. Furthermore, IFN-α pre-treatment of a CEM T lymphoblast cells significantly inhibited HIV infection/replication (measured by cellular p24), only in the absence of Vif (IIIBΔVif), but was unable to suppress full length IIIB infection. When analysing the mechanism by which Vif might target the JAK/STAT pathway, we found Vif interacts with both STAT1 and STAT3, (but not STAT2), and its expression promotes ubiquitination and MG132-sensitive, proteosomal degradation of both proteins. Vif's Elongin-Cullin-SOCS-box binding motif enables the formation of an active E3 ligase complex, which we found to be required for Vif's degradation of STAT1 and STAT3. In fact, the E3 ligase scaffold proteins, Cul5 and Rbx2, were also found to be

Clinical Implications of Phosphorylated STAT3 Expression in de novo Diffuse Large B-cell Lymphoma

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Ok, Chi Y; Chen, Jiayu; Xu-Monette, Ziju

2014-01-01

PURPOSE: Activated signal transducer and activator of transcription 3 (STAT3) regulates tumor growth, invasion, cell proliferation, angiogenesis, immune response, and survival. Data regarding expression of phosphorylated (activated) STAT3 in diffuse large B-cell lymphoma (DLBCL) and the impact of...

A novel small molecule inhibits STAT3 phosphorylation and DNA binding activity and exhibits potent growth suppressive activity in human cancer cells

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Lin Li

2010-08-01

Full Text Available Abstract Background Targeting Signal Transducer and Activator of Transcription 3 (STAT3 signaling is an attractive therapeutic approach for most types of human cancers with constitutively activated STAT3. A novel small molecular STAT3 inhibitor, FLLL32 was specifically designed from dietary agent, curcumin to inhibit constitutive STAT3 signaling in multiple myeloma, glioblastoma, liver cancer, and colorectal cancer cells. Results FLLL32 was found to be a potent inhibitor of STAT3 phosphorylation, STAT3 DNA binding activity, and the expression of STAT3 downstream target genes in vitro, leading to the inhibition of cell proliferation as well as the induction of Caspase-3 and PARP cleavages in human multiple myeloma, glioblastoma, liver cancer, and colorectal cancer cell lines. However, FLLL32 exhibited little inhibition on some tyrosine kinases containing SH2 or both SH2 and SH3 domains, and other protein and lipid kinases using a kinase profile assay. FLLL32 was also more potent than four previously reported JAK2 and STAT3 inhibitors as well as curcumin to inhibit cell viability in these cancer cells. Furthermore, FLLL32 selectively inhibited the induction of STAT3 phosphorylation by Interleukin-6 but not STAT1 phosphorylation by IFN-γ. Conclusion Our findings indicate that FLLL32 exhibits potent inhibitory activity to STAT3 and has potential for targeting multiple myeloma, glioblastoma, liver cancer, and colorectal cancer cells expressing constitutive STAT3 signaling.

Multidimensional single cell based STAT phosphorylation profiling identifies a novel biosignature for evaluation of systemic lupus erythematosus activity.

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Xinfang Huang

Full Text Available INTRODUCTION: Dysregulated cytokine action on immune cells plays an important role in the initiation and progress of systemic lupus erythematosus (SLE, a complex autoimmune disease. Comprehensively quantifying basal STATs phosphorylation and their signaling response to cytokines should help us to better understand the etiology of SLE. METHODS: Phospho-specific flow cytometry was used to measure the basal STAT signaling activation in three immune cell types of peripheral-blood mononuclear cells from 20 lupus patients, 9 rheumatoid arthritis (RA patients and 13 healthy donors (HDs. A panel of 27 cytokines, including inflammatory cytokines, was measured with Bio-Plex™ Human Cytokine Assays. Serum Prolactin levels were measured with an immunoradiometric assay. STAT signaling responses to inflammatory cytokines (interferon α [IFNα], IFNγ, interleukin 2 [IL2], IL6, and IL10 were also monitored. RESULTS: We observed the basal activation of STAT3 in SLE T cells and monocytes, and the basal activation of STAT5 in SLE T cells and B cells. The SLE samples clustered into two main groups, which were associated with the SLE Disease Activity Index 2000, their erythrocyte sedimentation rate, and their hydroxychloroquine use. The phosphorylation of STAT5 in B cells was associated with cytokines IL2, granulocyte colony-stimulating factor (G-CSF, and IFNγ, whereas serum prolactin affected STAT5 activation in T cells. The responses of STAT1, STAT3, and STAT5 to IFNα were greatly reduced in SLE T cells, B cells, and monocytes, except for the STAT1 response to IFNα in monocytes. The response of STAT3 to IL6 was reduced in SLE T cells. CONCLUSIONS: The basal activation of STATs signaling and reduced response to cytokines may be helpful us to identify the activity and severity of SLE.

Morbillivirus v proteins exhibit multiple mechanisms to block type 1 and type 2 interferon signalling pathways.

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Senthil K Chinnakannan

Full Text Available Morbilliviruses form a closely related group of pathogenic viruses which encode three non-structural proteins V, W and C in their P gene. Previous studies with rinderpest virus (RPV and measles virus (MeV have demonstrated that these non-structural proteins play a crucial role in blocking type I (IFNα/β and type II (IFNγ interferon action, and various mechanisms have been proposed for these effects. We have directly compared four important morbilliviruses, rinderpest (RPV, measles virus (MeV, peste des petits ruminants virus (PPRV and canine distemper virus (CDV. These viruses and their V proteins could all block type I IFN action. However, the viruses and their V proteins had varying abilities to block type II IFN action. The ability to block type II IFN-induced gene transcription correlated with co-precipitation of STAT1 with the respective V protein, but there was no correlation between co-precipitation of either STAT1 or STAT2 and the abilities of the V proteins to block type I IFN-induced gene transcription or the creation of the antiviral state. Further study revealed that the V proteins of RPV, MeV, PPRV and CDV could all interfere with phosphorylation of the interferon-receptor-associated kinase Tyk2, and the V protein of highly virulent RPV could also block the phosphorylation of another such kinase, Jak1. Co-precipitation studies showed that morbillivirus V proteins all form a complex containing Tyk2 and Jak1. This study highlights the ability of morbillivirus V proteins to target multiple components of the IFN signalling pathways to control both type I and type II IFN action.

Characterization of STAT5B phosphorylation correlating with expression of cytokine-inducible SH2-containing protein (CIS).

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Cooper, John C; Boustead, Jared N; Yu, Chao-Lan

2006-06-01

Cytokine-inducible SH2-containing protein (CIS) is the first identified member of genes encoding for the suppressor of cytokine signaling (SOCS). CIS is also a well-known target gene of signal transducer and activator of transcription 5 (STAT5) pathways, providing normal negative feedback control of signaling by cytokines and growth factors. Three other SOCS genes, SOCS1, SOCS2, and SOCS3, can be silenced by DNA hypermethylation in human cancers, suggesting a potential mechanism for constitutive STAT activation. However, it is not known whether CIS expression is similarly perturbed in tumor cells. We report here the absence of CIS expression in T lymphoma LSTRA that overexpresses the Lck protein tyrosine kinase and exhibits elevated STAT5 activity. Pervanadate-induced CIS expression and STAT5 binding to the CIS promoter in vivo over a short time course implies that mechanisms other than DNA hypermethylation may contribute to defective CIS expression in LSTRA cells. Comparison with cytokine-dependent BaF3 cells stimulated with interleukin-3 (IL-3) further reveals that CIS induction correlates with specific STAT5b post-translational modifications. It exhibits as the slowest migrating form through SDS-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. This distinctly modified STAT5b is the predominant form that binds to the consensus STAT5 sites in the CIS promoter and accumulates in the nucleus. In vitro phosphatase assays and phosphoamino acid analysis suggest the involvement of phosphorylation on residues other than the highly conserved tyrosine and serine sites in this distinct STAT5b mobility shift. All together, our results provide a novel link between incomplete STAT5b phosphorylation and defective SOCS gene expression in cancer cells.

The small molecule, LLL12, inhibits STAT3 phosphorylation and induces apoptosis in medulloblastoma and glioblastoma cells.

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Sarah Ball

Full Text Available Tumors of the central nervous system represent a major source of cancer-related deaths, with medulloblastoma and glioblastoma being the most common malignant brain tumors in children and adults respectively. While significant advances in treatment have been made, with the 5-year survival rate for medulloblastoma at 70-80%, treating patients under 3 years of age still poses a problem due to the deleterious effects of radiation on the developing brain, and the median survival for patients with glioblastoma is only 15 months. The transcription factor, STAT3, has been found constitutively activated in a wide variety of cancers and in recent years it has become an attractive therapeutic target. We designed a non-peptide small molecule STAT3 inhibitor, LLL12, using structure-based design. LLL12 was able to inhibit STAT3 phosphorylation, decrease cell viability and induce apoptosis in medulloblastoma and glioblastoma cell lines with elevated levels of p-STAT3 (Y705. IC(50 values for LLL12 were found to be between 1.07 µM and 5.98 µM in the five cell lines expressing phosphorylated STAT3. STAT3 target genes were found to be downregulated and a decrease in STAT3 DNA binding was observed following LLL12 treatment, indicating that LLL12 is an effective STAT3 inhibitor. LLL12 was also able to inhibit colony formation, wound healing and decreased IL-6 and LIF secretion. Our results suggest that LLL12 is a potent STAT3 inhibitor and that it may be a potential therapeutic treatment for medulloblastoma and glioblastoma.

Structurally modified curcumin analogs inhibit STAT3 phosphorylation and promote apoptosis of human renal cell carcinoma and melanoma cell lines.

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Matthew A Bill

Full Text Available The Janus kinase-2 (Jak2-signal transducer and activator of transcription-3 (STAT3 pathway is critical for promoting an oncogenic and metastatic phenotype in several types of cancer including renal cell carcinoma (RCC and melanoma. This study describes two small molecule inhibitors of the Jak2-STAT3 pathway, FLLL32 and its more soluble analog, FLLL62. These compounds are structurally distinct curcumin analogs that bind selectively to the SH2 domain of STAT3 to inhibit its phosphorylation and dimerization. We hypothesized that FLLL32 and FLLL62 would induce apoptosis in RCC and melanoma cells and display specificity for the Jak2-STAT3 pathway. FLLL32 and FLLL62 could inhibit STAT3 dimerization in vitro. These compounds reduced basal STAT3 phosphorylation (pSTAT3, and induced apoptosis in four separate human RCC cell lines and in human melanoma cell lines as determined by Annexin V/PI staining. Apoptosis was also confirmed by immunoblot analysis of caspase-3 processing and PARP cleavage. Pre-treatment of RCC and melanoma cell lines with FLLL32/62 did not inhibit IFN-γ-induced pSTAT1. In contrast to FLLL32, curcumin and FLLL62 reduced downstream STAT1-mediated gene expression of IRF1 as determined by Real Time PCR. FLLL32 and FLLL62 significantly reduced secretion of VEGF from RCC cell lines in a dose-dependent manner as determined by ELISA. Finally, each of these compounds inhibited in vitro generation of myeloid-derived suppressor cells. These data support further investigation of FLLL32 and FLLL62 as lead compounds for STAT3 inhibition in RCC and melanoma.

SH2 modified STAT1 induces HLA-I expression and improves IFN-γ signaling in IFN-α resistant HCV replicon cells.

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Bret Poat

2010-09-01

Full Text Available We have developed multiple stable cell lines containing subgenomic HCV RNA that are resistant to treatment with interferon alpha (IFN-α. Characterization of these IFN-α resistant replicon cells showed defects in the phosphorylation and nuclear translocation of STAT1 and STAT2 proteins due to a defective Jak-STAT pathway.In this study, we have developed an alternative strategy to overcome interferon resistance in a cell culture model by improving intracellular STAT1 signaling. An engineered STAT1-CC molecule with double cysteine substitutions in the Src-homology 2 (SH2 domains of STAT1 (at Ala-656 and Asn-658 efficiently phosphorylates and translocates to the nucleus of IFN-resistant cells in an IFN-γ dependent manner. Transfection of a plasmid clone containing STAT1-CC significantly activated the GAS promoter compared to wild type STAT1 and STAT3. The activity of the engineered STAT1-CC is dependent upon the phosphorylation of tyrosine residue 701, since the construct with a substituted phenylalanine residue at position 701 (STAT1-CC-Y701F failed to activate GAS promoter in the replicon cells. Intracellular expression of STAT1-CC protein showed phosphorylation and nuclear translocation in the resistant cell line after IFN-γ treatment. Transient transfection of STAT1-CC plasmid clone into an interferon resistant cell line resulted in inhibition of viral replication and viral clearance in an IFN-γ dependent manner. Furthermore, the resistant replicon cells transfected with STAT1-CC constructs significantly up regulated surface HLA-1 expression when compared to the wild type and Y to F mutant controls.These results suggest that modification of the SH2 domain of the STAT1 molecule allows for improved IFN-γ signaling through increased STAT1 phosphorylation, nuclear translocation, HLA-1 surface expression, and prolonged interferon antiviral gene activation.

STAT1, STAT3 and p38MAPK are involved in the apoptotic effect induced by a chimeric cyclic interferon-{alpha}2b peptide

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Blank, Viviana C.; Pena, Clara [Institute of Biochemistry and Biophysics (UBA-CONICET), School of Pharmacy and Biochemistry, University of Buenos Aires, Junin 956-C1113AAD Buenos Aires (Argentina); Roguin, Leonor P., E-mail: rvroguin@qb.ffyb.uba.ar [Institute of Biochemistry and Biophysics (UBA-CONICET), School of Pharmacy and Biochemistry, University of Buenos Aires, Junin 956-C1113AAD Buenos Aires (Argentina)

2010-02-15

In the search of mimetic peptides of the interferon-{alpha}2b molecule (IFN-{alpha}2b), we have previously designed and synthesized a chimeric cyclic peptide of the IFN-{alpha}2b that inhibits WISH cell proliferation by inducing an apoptotic response. Here, we first studied the ability of this peptide to activate intracellular signaling pathways and then evaluated the participation of some signals in the induction of apoptosis. Stimulation of WISH cells with the cyclic peptide showed tyrosine phosphorylation of Jak1 and Tyk2 kinases, tyrosine and serine phosphorylation of STAT1 and STAT3 transcription factors and activation of p38 MAPK pathway, although phosphorylation levels or kinetics were in some conditions different to those obtained under IFN-{alpha}2b stimulus. JNK and p44/42 pathways were not activated by the peptide in WISH cells. We also showed that STAT1 and STAT3 downregulation by RNA interference decreased the antiproliferative activity and the amount of apoptotic cells induced by the peptide. Pharmacological inhibition of p38 MAPK also reduced the peptide growth inhibitory activity and the apoptotic effect. Thus, we demonstrated that the cyclic peptide regulates WISH cell proliferation through the activation of Jak/STAT signaling pathway. In addition, our results indicate that p38 MAPK may also be involved in cell growth regulation. This study suggests that STAT1, STAT3 and p38 MAPK would be mediating the antitumor and apoptotic response triggered by the cyclic peptide in WISH cells.

STAT1, STAT3 and p38MAPK are involved in the apoptotic effect induced by a chimeric cyclic interferon-α2b peptide

International Nuclear Information System (INIS)

Blank, Viviana C.; Pena, Clara; Roguin, Leonor P.

2010-01-01

In the search of mimetic peptides of the interferon-α2b molecule (IFN-α2b), we have previously designed and synthesized a chimeric cyclic peptide of the IFN-α2b that inhibits WISH cell proliferation by inducing an apoptotic response. Here, we first studied the ability of this peptide to activate intracellular signaling pathways and then evaluated the participation of some signals in the induction of apoptosis. Stimulation of WISH cells with the cyclic peptide showed tyrosine phosphorylation of Jak1 and Tyk2 kinases, tyrosine and serine phosphorylation of STAT1 and STAT3 transcription factors and activation of p38 MAPK pathway, although phosphorylation levels or kinetics were in some conditions different to those obtained under IFN-α2b stimulus. JNK and p44/42 pathways were not activated by the peptide in WISH cells. We also showed that STAT1 and STAT3 downregulation by RNA interference decreased the antiproliferative activity and the amount of apoptotic cells induced by the peptide. Pharmacological inhibition of p38 MAPK also reduced the peptide growth inhibitory activity and the apoptotic effect. Thus, we demonstrated that the cyclic peptide regulates WISH cell proliferation through the activation of Jak/STAT signaling pathway. In addition, our results indicate that p38 MAPK may also be involved in cell growth regulation. This study suggests that STAT1, STAT3 and p38 MAPK would be mediating the antitumor and apoptotic response triggered by the cyclic peptide in WISH cells.

Phosphorylated STAT5 directly facilitates parvovirus B19 DNA replication in human erythroid progenitors through interaction with the MCM complex.

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Ganaie, Safder S; Zou, Wei; Xu, Peng; Deng, Xuefeng; Kleiboeker, Steve; Qiu, Jianming

2017-05-01

Productive infection of human parvovirus B19 (B19V) exhibits high tropism for burst forming unit erythroid (BFU-E) and colony forming unit erythroid (CFU-E) progenitor cells in human bone marrow and fetal liver. This exclusive restriction of the virus replication to human erythroid progenitor cells is partly due to the intracellular factors that are essential for viral DNA replication, including erythropoietin signaling. Efficient B19V replication also requires hypoxic conditions, which upregulate the signal transducer and activator of transcription 5 (STAT5) pathway, and phosphorylated STAT5 is essential for virus replication. In this study, our results revealed direct involvement of STAT5 in B19V DNA replication. Consensus STAT5-binding elements were identified adjacent to the NS1-binding element within the minimal origins of viral DNA replication in the B19V genome. Phosphorylated STAT5 specifically interacted with viral DNA replication origins both in vivo and in vitro, and was actively recruited within the viral DNA replication centers. Notably, STAT5 interacted with minichromosome maintenance (MCM) complex, suggesting that STAT5 directly facilitates viral DNA replication by recruiting the helicase complex of the cellular DNA replication machinery to viral DNA replication centers. The FDA-approved drug pimozide dephosphorylates STAT5, and it inhibited B19V replication in ex vivo expanded human erythroid progenitors. Our results demonstrated that pimozide could be a promising antiviral drug for treatment of B19V-related diseases.

Inhibition of protein phosphatase 2A induces serine/threonine phosphorylation, subcellular redistribution, and functional inhibition of STAT3

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Woetmann, A; Nielsen, M; Christensen, S T

1999-01-01

Signal transducers and activators of transcription (STATs) are rapidly phosphorylated on tyrosine residues in response to cytokine and growth factor stimulation of cell surface receptors. STATs hereafter are translocated to the nucleus where they act as transcription factors. Recent reports suggest...

ATF3 activates Stat3 phosphorylation through inhibition of p53 expression in skin cancer cells.

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Hao, Zhen-Feng; Ao, Jun-Hong; Zhang, Jie; Su, You-Ming; Yang, Rong-Ya

2013-01-01

ATF3, a member of the ATF/CREB family of transcription factors, has been found to be selectively induced by calcineurin/NFAT inhibition and to enhance keratinocyte tumor formation, although the precise role of ATF3 in human skin cancer and possible mechanisms remain unknown. In this study, clinical analysis of 30 skin cancer patients and 30 normal donors revealed that ATF3 was accumulated in skin cancer tissues. Functional assays demonstrated that ATF3 significantly promoted skin cancer cell proliferation. Mechanically, ATF3 activated Stat3 phosphorylation in skin cancer cell through regulation of p53 expression. Moreover, the promotion effect of ATF3 on skin cancer cell proliferation was dependent on the p53-Stat3 signaling cascade. Together, the results indicate that ATF3 might promote skin cancer cell proliferation and enhance skin keratinocyte tumor development through inhibiting p53 expression and then activating Stat3 phosphorylation.

STAT3 can be activated through paracrine signaling in breast epithelial cells

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Lieblein, Jacqueline C; Ball, Sarah; Hutzen, Brian; Sasser, A Kate; Lin, Huey-Jen; Huang, Tim HM; Hall, Brett M; Lin, Jiayuh

2008-01-01

Many cancers, including breast cancer, have been identified with increased levels of phosphorylated or the active form of Signal Transducers and Activators of Transcription 3 (STAT3) protein. However, whether the tumor microenvironment plays a role in this activation is still poorly understood. Conditioned media, which contains soluble factors from MDA-MB-231 and MDA-MB-468 breast cancer cells and breast cancer associated fibroblasts, was added to MCF-10A breast epithelial and MDA-MB-453 breast cancer cells. The stimulation of phosphorylated STAT3 (p-STAT3) levels by conditioned media was assayed by Western blot in the presence or absence of neutralized IL-6 antibody, or a JAK/STAT3 inhibitor, JSI-124. The stimulation of cell proliferation in MCF-10A cells by conditioned media in the presence or absence of JSI-124 was subjected to MTT analysis. IL-6, IL-10, and VEGF levels were determined by ELISA analysis. Our results demonstrated that conditioned media from cell lines with constitutively active STAT3 are sufficient to induce p-STAT3 levels in various recipients that do not possess elevated p-STAT3 levels. This signaling occurs through the JAK/STAT3 pathway, leading to STAT3 phosphorylation as early as 30 minutes and is persistent for at least 24 hours. ELISA analysis confirmed a correlation between elevated levels of IL-6 production and p-STAT3. Neutralization of the IL-6 ligand or gp130 was sufficient to block increased levels of p-STAT3 (Y705) in treated cells. Furthermore, soluble factors within the MDA-MB-231 conditioned media were also sufficient to stimulate an increase in IL-6 production from MCF-10A cells. These results demonstrate STAT3 phosphorylation in breast epithelial cells can be stimulated by paracrine signaling through soluble factors from both breast cancer cells and breast cancer associated fibroblasts with elevated STAT3 phosphorylation. The induction of STAT3 phosphorylation is through the IL-6/JAK pathway and appears to be associated with

Regulation of c–myc expression by IFN–γ through Stat1-dependent and -independent pathways

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Ramana, Chilakamarti V.; Grammatikakis, Nicholas; Chernov, Mikhail; Nguyen, Hannah; Goh, Kee Chuan; Williams, Bryan R.G.; Stark, George R.

2000-01-01

Interferons (IFNs) inhibit cell growth in a Stat1-dependent fashion that involves regulation of c–myc expression. IFN–γ suppresses c–myc in wild-type mouse embryo fibroblasts, but not in Stat1-null cells, where IFNs induce c–myc mRNA rapidly and transiently, thus revealing a novel signaling pathway. Both tyrosine and serine phosphorylation of Stat1 are required for suppression. Induced expression of c–myc is likely to contribute to the proliferation of Stat1-null cells in response to IFNs. IFNs also suppress platelet-derived growth factor (PDGF)-induced c–myc expression in wild-type but not in Stat1-null cells. A gamma-activated sequence element in the promoter is necessary but not sufficient to suppress c–myc expression in wild-type cells. In PKR-null cells, the phosphorylation of Stat1 on Ser727 and transactivation are both defective, and c–myc mRNA is induced, not suppressed, in response to IFN–γ. A role for Raf–1 in the Stat1-independent pathway is revealed by studies with geldanamycin, an HSP90-specific inhibitor, and by expression of a mutant of p50cdc37 that is unable to recruit HSP90 to the Raf–1 complex. Both agents abrogated the IFN–γ-dependent induction of c–myc expression in Stat1-null cells. PMID:10637230

Dual inhibition of STAT1 and STAT3 activation downregulates expression of PD-L1 in human breast cancer cells.

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Sasidharan Nair, Varun; Toor, Salman M; Ali, Bassam R; Elkord, Eyad

2018-05-02

Breast cancer is the most commonly diagnosed cancer, and it is a leading cause of cancer-related deaths in females worldwide. Triple-negative breast cancer (TNBC) constitutes 15% of breast cancer and shows distinct metastasis profiles with poor prognosis. Strong PD-L1 expression has been observed in some tumors, supporting their escape from immune surveillance. Targeting PD-L1 could be a promising therapeutic approach in breast cancer patients. We investigated potential molecular mechanisms for constitutive expression of PD-L1 by inhibiting upstream STAT1 and STAT3 signals. PD-L1 expression in three breast cancer cell lines was measured using quantitative PCR and western blotting. Activation of STAT1 and STAT3 was blocked using pharmacological inhibitors and siRNA. The mechanism underlying the constitutive expression of PD-L1 was investigated using ChIP and co-immunoprecipitation assays. We found that individual inhibition of STAT1 and STAT3 activation partially downregulated PD-L1, while combined inhibition completely downregulated PD-L1 expression. Moreover, our results suggest that pSTAT1-pSTAT3 dimerize in cytosol and translocate to the nucleus, where they bind to PD-L1 promoter and induce PD-L1 expression. These findings provide a rationale for combined targeting of STAT1 and STAT3 for the development of immune-based cancer therapies for down regulation of PD-L1 expression.

A novel mechanism of skin tumor promotion involving interferon-gamma (IFNγ)/signal transducer and activator of transcription-1 (Stat1) signaling.

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Bozeman, Ronald; Abel, Erika L; Macias, Everardo; Cheng, Tianyi; Beltran, Linda; DiGiovanni, John

2015-08-01

The current study was designed to explore the role of signal transducer and activator of transcription 1 (Stat1) during tumor promotion using the mouse skin multistage carcinogenesis model. Topical treatment with both 12-O-tetradecanoylphorbol-13-acetate (TPA) and 3-methyl-1,8-dihydroxy-9-anthrone (chrysarobin or CHRY) led to rapid phosphorylation of Stat1 on both tyrosine (Y701) and serine (S727) residues in epidermis. CHRY treatment also led to upregulation of unphosphorylated Stat1 (uStat1) at later time points. CHRY treatment also led to upregulation of interferon regulatory factor 1 (IRF-1) mRNA and protein, which was dependent on Stat1. Further analyses demonstrated that topical treatment with CHRY but not TPA upregulated interferon-gamma (IFNγ) mRNA in the epidermis and that the induction of both IRF-1 and uStat1 was dependent on IFNγ signaling. Stat1 deficient (Stat1(-/-) ) mice were highly resistant to skin tumor promotion by CHRY. In contrast, the tumor response (in terms of both papillomas and squamous cell carcinomas) was similar in Stat1(-/-) mice and wild-type littermates with TPA as the promoter. Maximal induction of both cyclooxygenase-2 and inducible nitric oxide synthase in epidermis following treatment with CHRY was also dependent on the presence of functional Stat1. These studies define a novel mechanism associated with skin tumor promotion by the anthrone class of tumor promoters involving upregulation of IFNγ signaling in the epidermis and downstream signaling through activated (phosphorylated) Stat1, IRF-1 and uStat1. © 2014 Wiley Periodicals, Inc.

STAT3 Potentiates SIAH-1 Mediated Proteasomal Degradation of β-Catenin in Human Embryonic Kidney Cells.

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Shin, Minkyung; Yi, Eun Hee; Kim, Byung-Hak; Shin, Jae-Cheon; Park, Jung Youl; Cho, Chung-Hyun; Park, Jong-Wan; Choi, Kang-Yell; Ye, Sang-Kyu

2016-11-30

The β-catenin functions as an adhesion molecule and a component of the Wnt signaling pathway. In the absence of the Wnt ligand, β-catenin is constantly phosphorylated, which designates it for degradation by the APC complex. This process is one of the key regulatory mechanisms of β-catenin. The level of β-catenin is also controlled by the E3 ubiquitin protein ligase SIAH-1 via a phosphorylation-independent degradation pathway. Similar to β-catenin, STAT3 is responsible for various cellular processes, such as survival, proliferation, and differentiation. However, little is known about how these molecules work together to regulate diverse cellular processes. In this study, we investigated the regulatory relationship between STAT3 and β-catenin in HEK293T cells. To our knowledge, this is the first study to report that β-catenin-TCF-4 transcriptional activity was suppressed by phosphorylated STAT3; furthermore, STAT3 inactivation abolished this effect and elevated activated β-catenin levels. STAT3 also showed a strong interaction with SIAH-1, a regulator of active β-catenin via degradation, which stabilized SIAH-1 and increased its interaction with β-catenin. These results suggest that activated STAT3 regulates active β-catenin protein levels via stabilization of SIAH-1 and the subsequent ubiquitin-dependent proteasomal degradation of β-catenin in HEK293T cells.

Stat1-independent regulation of gene expression in response to IFN-γ

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Ramana, Chilakamarti V.; Gil, M. Pilar; Han, Yulong; Ransohoff, Richard M.; Schreiber, Robert D.; Stark, George R.

2001-01-01

Although Stat1 is essential for cells to respond fully to IFN-γ, there is substantial evidence that, in the absence of Stat1, IFN-γ can still regulate the expression of some genes, induce an antiviral state and affect cell growth. We have now identified many genes that are regulated by IFN-γ in serum-starved Stat1-null mouse fibroblasts. The proteins induced by IFN-γ in Stat1-null cells can account for the substantial biological responses that remain. Some genes are induced in both wild-type and Stat1-null cells and thus are truly Stat1-independent. Others are subject to more complex regulation in response to IFN-γ, repressed by Stat1 in wild-type cells and activated in Stat1-null cells. Many genes induced by IFN-γ in Stat1-null fibroblasts also are induced by platelet-derived growth factor in wild-type cells and thus are likely to be involved in cell proliferation. In mouse cells expressing the docking site mutant Y440F of human IFN-γ receptor subunit 1, the mouse Stat1 is not phosphorylated in response to human IFN-γ, but c-myc and c-jun are still induced, showing that the Stat1 docking site is not required for Stat1-independent signaling. PMID:11390994

Structural and functional characterization of salmon STAT1, STAT2 and IRF9 homologs sheds light on interferon signaling in teleosts

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Mehrdad Sobhkhez

2014-01-01

Full Text Available Mammalian IRF9 and STAT2, together with STAT1, form the ISGF3 transcription factor complex, which is critical for type I interferon (IFN-induced signaling, while IFNγ stimulation is mediated by homodimeric STAT1 protein. Teleost fish are known to possess most JAK and STAT family members, however, description of their functional activity in lower vertebrates is still scarce. In the present study we have identified two different STAT2 homologs and one IRF9 homolog from Atlantic salmon (Salmo salar. Both proteins have domain-like structures with functional motifs that are similar to higher vertebrates, suggesting that they are orthologs to mammalian STAT2 and IRF9. The two identified salmon STAT2s, named STAT2a and STAT2b, showed high sequence identity but were divergent in their transactivation domain (TAD. Like STAT1, ectopically expressed STAT2a and b were shown to be tyrosine phosphorylated by type I IFNs and, interestingly, also by IFNγ. Microscopy analyses demonstrated that STAT2 co-localized with STAT1a in the cytoplasm of unstimulated cells, while IFNa1 and IFNγ stimulation seemed to favor their nuclear localization. Overexpression of STAT2a or STAT2b together with STAT1a activated a GAS-containing reporter gene construct in IFNγ-stimulated cells. The highest induction of GAS promoter activation was found in IFNγ-stimulated cells transfected with IRF9 alone. Taken together, these data suggest that salmon STAT2 and IRF9 may have a role in IFNγ-induced signaling and promote the expression of GAS-driven genes in bony fish. Since mammalian STAT2 is primarily an ISGF3 component and not involved in IFNγ signaling, our finding features a novel role for STAT2 in fish.

Human Airway Eosinophils Exhibit Preferential Reduction in STAT Signaling Capacity and Increased CISH Expression1

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Burnham, Mandy E.; Koziol-White, Cynthia J.; Esnault, Stephane; Bates, Mary E.; Evans, Michael D.; Bertics, Paul J.; Denlinger, Loren C.

2013-01-01

Allergic asthma, a chronic respiratory disorder marked by inflammation and recurrent airflow obstruction, is associated with elevated levels of Interleukin-5 (IL-5) family cytokines, and elevated numbers of eosinophils (EOS). IL-5 family cytokines elongate peripheral blood EOS (EOSPB) viability, recruit EOSPB to the airways, and at higher concentrations, induce degranulation and reactive oxygen species (ROS) generation. While, EOSA remain signal ready in that GM-CSF treatment induces degranulation, treatment of EOSA with IL-5 family cytokines no longer confers a survival advantage. Since the IL-5 family receptors have common signaling capacity, but are uncoupled from EOSA survival while other IL-5 family induced endpoints remain functional, we tested the hypothesis that EOSA possess a JAK/STAT specific regulatory mechanism (since JAK/STAT signaling is critical to EOS survival). We found that IL-5 family-induced STAT3 and STAT5 phosphorylation is attenuated in EOSA relative to blood EOS from airway allergen-challenged donors (EOSCPB). However, IL-5 family induced ERK1/2 phosphorylation is not altered between EOSA and EOSCPB. These observations suggest EOSA possess a regulatory mechanism for suppressing STAT signaling distinct from ERK1/2 activation. Furthermore, we found, in EOSPB, IL-5 family cytokines induce members of the suppressors of cytokine signaling (SOCS) genes, CISH and SOCS1. Additionally, following allergen challenge, EOSA express significantly more CISH and SOCS1 mRNA and CISH protein than EOSPB counterparts. In EOSPB, long-term pretreatment with IL-5 family cytokines, to varying degrees, attenuates IL-5 family induced STAT5 phosphorylation. These data support a model wherein IL-5 family cytokines trigger a selective down-regulation mechanism in EOSA for JAK/STAT pathways. PMID:23956426

Inhibition of STAT3 signaling and induction of SHP1 mediate antiangiogenic and antitumor activities of ergosterol peroxide in U266 multiple myeloma cells

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Rhee, Yun-Hee; Jeong, Soo-Jin; Lee, Hyo-Jeong; Lee, Hyo-Jung; Koh, Wonil; Jung, Ji Hoon; Kim, Sun-Hee; Sung-Hoon, Kim

2012-01-01

Ergosterol peroxide (EP) derived from edible mushroom has been shown to exert anti-tumor activity in several cancer cells. In the present study, anti-angiogenic activity of EP was investigated with the underlying molecular mechanisms in human multiple myeloma U266 cells. Despite weak cytotoxicity against U266 cells, EP suppressed phosphorylation, DNA binding activity and nuclear translocalization of signal transducer and activator of transcription 3 (STAT3) in U266 cells at nontoxic concentrations. Also, EP inhibited phosphorylation of the upstream kinases Janus kinase 2 (JAK2) and Src in a time-dependent manner. Furthermore, EP increased the expression of protein tyrosine phosphatase SHP-1 at protein and mRNA levels, and conversely silencing of the SHP-1 gene clearly blocked EP-mediated STAT3 inactivation. In addition, EP significantly decreased vascular endothelial growth factor (VEGF), one of STAT3 target genes at cellular and protein levels as well as disrupted in vitro tube formation assay. Moreover, EP significantly suppressed the growth of U266 cells inoculated in female BALB/c athymic nude mice and immunohistochemistry revealed that EP effectively reduced the expression of STAT3 and CD34 in tumor sections compared to untreated control. These findings suggest that EP can exert antitumor activity in multiple myeloma U266 cells partly with antiangiogenic activity targeting JAK2/STAT3 signaling pathway as a potent cancer preventive agent for treatment of multiple myeloma cells

Proinflammatory Cytokines IL-6 and TNF-α Increased Telomerase Activity through NF-κB/STAT1/STAT3 Activation, and Withaferin A Inhibited the Signaling in Colorectal Cancer Cells

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Seyung S. Chung

2017-01-01

Full Text Available There are increasing evidences of proinflammatory cytokine involvement in cancer development. Here, we found that two cytokines, IL-6 and TNF-α, activated colorectal cancer cells to be more invasive and stem-like. Combined treatment of IL-6 and TNF-α phosphorylated transcription factors STAT3 in a synergistic manner. STAT3, STAT1, and NF-κB physically interacted upon the cytokine stimulation. STAT3 was bound to the promoter region of human telomerase reverse transcriptase (hTERT. IL-6 and TNF-α stimulation further enhanced STAT3 binding affinity. Stem cell marker Oct-4 was upregulated in colorectal cancer cells upon IL-6 and TNF-α stimulation. Withaferin A, an anti-inflammatory steroidal lactone, inhibited the IL-6- and TNF-α-induced cancer cell invasion and decreased colonosphere formation. Notably, withaferin A inhibited STAT3 phosphorylation and abolished the STAT3, STAT1, and NF-κB interactions. Oct-4 expression was also downregulated by withaferin A inhibition. The binding of STAT3 to the hTERT promoter region and telomerase activity showed reduction with withaferin A treatments. Proinflammatory cytokine-induced cancer cell invasiveness is mediated by a STAT3-regulated mechanism in colorectal cancer cells. Our data suggest that withaferin A could be a promising anticancer agent that effectively inhibits the progression of colorectal cancer.

IGF-1-induced MMP-11 expression promotes the proliferation and invasion of gastric cancer cells through the JAK1/STAT3 signaling pathway.

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Su, Chao; Wang, Wenchang; Wang, Cunchuan

2018-05-01

The present study aimed to investigate the association between insulin-like growth factor-1 (IGF-1) and matrix metalloproteinase-11 (MMP-11) expression in gastric cancer (GC) and the underlying mechanisms in SGC-7901 cells. Reverse transcription-quantitative polymerase chain reaction analysis revealed that the expression of IGF-1 and MMP-11 was significantly upregulated in GC tissues compared with normal gastric tissue. Furthermore, IGF-1 significantly and dose-dependently promoted MMP-11. Western blotting revealed that the addition of IGF-1 to SGC-7901 cells led to an evident enhancement in signal transducer and activator of transcription 3 (STAT3), IGF-1R and Janus kinase 1 (JAK1) phosphorylation at 20 and 40 min. A decrease in the extent of the elevated expression of MMP-11 and the enhanced phosphorylation of STAT3, JAK1 and IGF-1 receptor (IGF-1R) induced by IGF-1 in SGC-7901 cells were observed following treatment with NT157 (an IGF-1R inhibitor). Furthermore, piceatannol (a JAK1 inhibitor) or small interfering RNA against STAT3 reduced the extent of the increased expression of MMP-11 induced by IGF-1 in SGC-7901 cells. Piceatannol treatment induced the dose-dependent decline in the enhancement of STAT3 phosphorylation induced by IGF-1, indicating that the JAK1/STAT3 pathway may be implicated in the elevated expression of MMP-11 induced by IGF-1 in SGC-7901 cells. Finally, IGF-1 treatment significantly promoted the proliferation and invasion of SGC-7901 cells, which was inhibited following NT157, piceatannol or si-STAT3 treatment. The present study therefore demonstrated that IGF-1-induced MMP-11 may have facilitated the proliferation and invasion of SGC-7901 cells via the JAK1/STAT3 pathway.

A stable aspirin-triggered lipoxin A4 analog blocks phosphorylation of leukocyte-specific protein 1 in human neutrophils.

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Ohira, Taisuke; Bannenberg, Gerard; Arita, Makoto; Takahashi, Minoru; Ge, Qingyuan; Van Dyke, Thomas E; Stahl, Gregory L; Serhan, Charles N; Badwey, John A

2004-08-01

Lipoxins and their aspirin-triggered 15-epimers are endogenous anti-inflammatory agents that block neutrophil chemotaxis in vitro and inhibit neutrophil influx in several models of acute inflammation. In this study, we examined the effects of 15-epi-16-(p-fluoro)-phenoxy-lipoxin A(4) methyl ester, an aspirin-triggered lipoxin A(4)-stable analog (ATLa), on the protein phosphorylation pattern of human neutrophils. Neutrophils stimulated with the chemoattractant fMLP were found to exhibit intense phosphorylation of a 55-kDa protein that was blocked by ATLa (10-50 nM). This 55-kDa protein was identified as leukocyte-specific protein 1, a downstream component of the p38-MAPK cascade in neutrophils, by mass spectrometry, Western blotting, and immunoprecipitation experiments. ATLa (50 nM) also reduced phosphorylation/activation of several components of the p38-MAPK pathway in these cells (MAPK kinase 3/MAPK kinase 6, p38-MAPK, MAPK-activated protein kinase-2). These results indicate that ATLa exerts its anti-inflammatory effects, at least in part, by blocking activation of the p38-MAPK cascade in neutrophils, which is known to promote chemotaxis and other proinflammatory responses by these cells.

Human Cytomegalovirus Immediate-Early 1 Protein Rewires Upstream STAT3 to Downstream STAT1 Signaling Switching an IL6-Type to an IFNγ-Like Response.

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Thomas Harwardt

2016-07-01

Full Text Available The human cytomegalovirus (hCMV major immediate-early 1 protein (IE1 is best known for activating transcription to facilitate viral replication. Here we present transcriptome data indicating that IE1 is as significant a repressor as it is an activator of host gene expression. Human cells induced to express IE1 exhibit global repression of IL6- and oncostatin M-responsive STAT3 target genes. This repression is followed by STAT1 phosphorylation and activation of STAT1 target genes normally induced by IFNγ. The observed repression and subsequent activation are both mediated through the same region (amino acids 410 to 445 in the C-terminal domain of IE1, and this region serves as a binding site for STAT3. Depletion of STAT3 phenocopies the STAT1-dependent IFNγ-like response to IE1. In contrast, depletion of the IL6 receptor (IL6ST or the STAT kinase JAK1 prevents this response. Accordingly, treatment with IL6 leads to prolonged STAT1 instead of STAT3 activation in wild-type IE1 expressing cells, but not in cells expressing a mutant protein (IE1dl410-420 deficient for STAT3 binding. A very similar STAT1-directed response to IL6 is also present in cells infected with a wild-type or revertant hCMV, but not an IE1dl410-420 mutant virus, and this response results in restricted viral replication. We conclude that IE1 is sufficient and necessary to rewire upstream IL6-type to downstream IFNγ-like signaling, two pathways linked to opposing actions, resulting in repressed STAT3- and activated STAT1-responsive genes. These findings relate transcriptional repressor and activator functions of IE1 and suggest unexpected outcomes relevant to viral pathogenesis in response to cytokines or growth factors that signal through the IL6ST-JAK1-STAT3 axis in hCMV-infected cells. Our results also reveal that IE1, a protein considered to be a key activator of the hCMV productive cycle, has an unanticipated role in tempering viral replication.

Native and reconstituted HDL activate Stat3 in ventricular cardiomyocytes via ERK1/2: role of sphingosine-1-phosphate.

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Frias, Miguel A; James, Richard W; Gerber-Wicht, Christine; Lang, Ursula

2009-05-01

High-density lipoprotein (HDL) has been reported to have cardioprotective properties independent from its cholesterol transport activity. The influence of native HDL and reconstituted HDL (rHDL) on Stat3, the transcription factor playing an important role in myocardium adaptation to stress, was analysed in neonatal rat ventricular cardiomyocytes. We have investigated modulating the composition of rHDL as a means of expanding its function and potential cardioprotective effects. Stat3 phosphorylation and activation were determined by western blotting and electrophoretic mobility shift assay (EMSA). In ventricular cardiomyocytes, HDL and the HDL constituent sphingosine-1-phosphate (S1P) induce a concentration- and time-dependent increase in Stat3 activation. They also enhance extracellular signal-regulated kinases (ERK1/2) and p38 mitogen-activated protein kinase (MAPK) phosphorylation. U0126, a specific inhibitor of MEK1/2, the upstream activator of ERK1/2, abolishes HDL- and S1P-induced Stat3 activation, whereas the p38 MAPK blocker SB203580 has no significant effect. Inhibition of the tyrosine kinase family Src (Src) caused a significant reduction of Stat3 activation, whereas inhibition of phosphatidylinositol 3-kinase (PI3K) had no effect. S1P and rHDL containing S1P have a similar strong stimulatory action on Stat3, ERK1/2, and p38 MAPK comparable to native HDL. S1P-free rHDL has a much weaker effect. Experiments with agonists and antagonists of the S1P receptor subtypes indicate that HDL and S1P activate Stat3 mainly through the S1P2 receptor. In ventricular cardiomyocytes, addition of S1P to rHDL enhances its therapeutic potential by improving its capacity to activate Stat3. Activation of Stat3 occurs mainly via the S1P constituent and the lipid receptor S1P2 requiring stimulation of ERK1/2 and Src but not p38 MAPK or PI3K. The study underlines the therapeutic potential of tailoring rHDL to confront particular clinical situations.

Cross-talk between KLF4 and STAT3 regulates axon regeneration

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Qin, Song; Zou, Yuhua; Zhang, Chun-Li

2013-10-01

Cytokine-induced activation of signal transducer and activator of transcription 3 (STAT3) promotes the regrowth of damaged axons in the adult central nervous system (CNS). Here we show that KLF4 physically interacts with STAT3 upon cytokine-induced phosphorylation of tyrosine 705 (Y705) on STAT3. This interaction suppresses STAT3-dependent gene expression by blocking its DNA-binding activity. The deletion of KLF4 in vivo induces axon regeneration of adult retinal ganglion cells (RGCs) via Janus kinase (JAK)-STAT3 signalling. This regeneration can be greatly enhanced by exogenous cytokine treatment, or removal of an endogenous JAK-STAT3 pathway inhibitor called suppressor of cytokine signalling 3 (SOCS3). These findings reveal an unexpected cross-talk between KLF4 and activated STAT3 in the regulation of axon regeneration that might have therapeutic implications in promoting repair of injured adult CNS.

A STAT3-decoy oligonucleotide induces cell death in a human colorectal carcinoma cell line by blocking nuclear transfer of STAT3 and STAT3-bound NF-κB

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Le Coquil Stéphanie

2011-04-01

Full Text Available Abstract Background The transcription factor STAT3 (signal transducer and activator of transcription 3 is frequently activated in tumor cells. Activated STAT3 forms homodimers, or heterodimers with other TFs such as NF-κB, which becomes activated. Cytoplasmic STAT3 dimers are activated by tyrosine phosphorylation; they interact with importins via a nuclear localization signal (NLS one of which is located within the DNA-binding domain formed by the dimer. In the nucleus, STAT3 regulates target gene expression by binding a consensus sequence within the promoter. STAT3-specific decoy oligonucleotides (STAT3-decoy ODN that contain this consensus sequence inhibit the transcriptional activity of STAT3, leading to cell death; however, their mechanism of action is unclear. Results The mechanism of action of a STAT3-decoy ODN was analyzed in the colon carcinoma cell line SW 480. These cells' dependence on activated STAT3 was verified by showing that cell death is induced by STAT3-specific siRNAs or Stattic. STAT3-decoy ODN was shown to bind activated STAT3 within the cytoplasm, and to prevent its translocation to the nucleus, as well as that of STAT3-associated NF-κB, but it did not prevent the nuclear transfer of STAT3 with mutations in its DNA-binding domain. The complex formed by STAT3 and the STAT3-decoy ODN did not associate with importin, while STAT3 alone was found to co-immunoprecipitate with importin. Leptomycin B and vanadate both trap STAT3 in the nucleus. They were found here to oppose the cytoplasmic trapping of STAT3 by the STAT3-decoy ODN. Control decoys consisting of either a mutated STAT3-decoy ODN or a NF-κB-specific decoy ODN had no effect on STAT3 nuclear translocation. Finally, blockage of STAT3 nuclear transfer correlated with the induction of SW 480 cell death. Conclusions The inhibition of STAT3 by a STAT3-decoy ODN, leading to cell death, involves the entrapment of activated STAT3 dimers in the cytoplasm. A mechanism is

Alteration of SHP-1/p-STAT3 Signaling: A Potential Target for Anticancer Therapy

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Tzu-Ting Huang

2017-06-01

Full Text Available The Src homology 2 (SH2 domain-containing protein tyrosine phosphatase 1 (SHP-1, a non-receptor protein tyrosine phosphatase, has been reported as a negative regulator of phosphorylated signal transducer and activator of transcription 3 (STAT3 and linked to tumor development. In this present review, we will discuss the importance and function of SHP-1/p-STAT3 signaling in nonmalignant conditions as well as malignancies, its cross-talk with other pathways, the current clinical development and the potential role of inhibitors of this pathway in anticancer therapy and clinical relevance of SHP-1/p-STAT3 in cancers. Lastly, we will summarize and highlight work involving novel drugs/compounds targeting SHP-1/p-STAT3 signaling and combined strategies that were/are discovered in our and our colleagues’ laboratories.

STAT6 deficiency ameliorates Graves' disease severity by suppressing thyroid epithelial cell hyperplasia.

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Jiang, Xuechao; Zha, Bingbing; Liu, Xiaoming; Liu, Ronghua; Liu, Jun; Huang, Enyu; Qian, Tingting; Liu, Jiajing; Wang, Zhiming; Zhang, Dan; Wang, Luman; Chu, Yiwei

2016-12-01

Signal transducer and activator of transcription 6 (STAT6) is involved in epithelial cell growth. However, little is known regarding the STAT6 phosphorylation status in Graves' disease (GD) and its role in thyroid epithelial cells (TECs). In this study, we found that STAT6 phosphorylation (p-STAT6) was significantly increased in TECs from both GD patients and experimental autoimmune Graves' disease mice and that STAT6 deficiency ameliorated GD symptoms. Autocrine IL-4 signalling in TECs activated the phosphorylation of STAT6 via IL-4 R engagement, and the downstream targets of STAT6 were Bcl-xL and cyclin D1. Thus, the IL-4-STAT6-Bcl-xL/cyclin D1 pathway is crucial for TEC hyperplasia, which aggravates GD. More importantly, in vitro and in vivo experiments demonstrated that STAT6 phosphorylation inhibited by AS1517499 decreased TEC hyperplasia, thereby reducing serum T3 and T4 and ameliorating GD. Thus, our study reveals that in addition to the traditional pathogenesis of GD, in which autoantibody TRAb stimulates thyroid-stimulating hormone receptors and consequently produces T3, T4, TRAb could also trigger TECs producing IL-4, and IL-4 then acts in an autocrine manner to activate p-STAT6 signalling and stimulate unrestricted cell growth, thus aggravating GD. These findings suggest that STAT6 inhibitors could be potent therapeutics for treating GD.

Cellular response to alkylating agent MNNG is impaired in STAT1-deficients cells.

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Ah-Koon, Laurent; Lesage, Denis; Lemadre, Elodie; Souissi, Inès; Fagard, Remi; Varin-Blank, Nadine; Fabre, Emmanuelle E; Schischmanoff, Olivier

2016-10-01

The SN 1 alkylating agents activate the mismatch repair system leading to delayed G2 /M cell cycle arrest and DNA repair with subsequent survival or cell death. STAT1, an anti-proliferative and pro-apoptotic transcription factor is known to potentiate p53 and to affect DNA-damage cellular response. We studied whether STAT1 may modulate cell fate following activation of the mismatch repair system upon exposure to the alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Using STAT1-proficient or -deficient cell lines, we found that STAT1 is required for: (i) reduction in the extent of DNA lesions, (ii) rapid phosphorylation of T68-CHK2 and of S15-p53, (iii) progression through the G2 /M checkpoint and (iv) long-term survival following treatment with MNNG. Presence of STAT1 is critical for the formation of a p53-DNA complex comprising: STAT1, c-Abl and MLH1 following exposure to MNNG. Importantly, presence of STAT1 allows recruitment of c-Abl to p53-DNA complex and links c-Abl tyrosine kinase activity to MNNG-toxicity. Thus, our data highlight the important modulatory role of STAT1 in the signalling pathway activated by the mismatch repair system. This ability of STAT1 to favour resistance to MNNG indicates the targeting of STAT1 pathway as a therapeutic option for enhancing the efficacy of SN1 alkylating agent-based chemotherapy. © 2016 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.

Analysis of signal transducer and activator of transcription 3 (Stat 3) pathway in multiple myeloma: Stat 3 activation and cyclin D1 dysregulation are mutually exclusive events.

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Quintanilla-Martinez, Leticia; Kremer, Marcus; Specht, Katja; Calzada-Wack, Julia; Nathrath, Michaela; Schaich, Robert; Höfler, Heinz; Fend, Falko

2003-05-01

The signal transducer and activator of transcription molecules (Stats) play key roles in cytokine-induced signal transduction. Recently, it was proposed that constitutively activated Stat 3 (Stat 3 phosphorylated) contributes to the pathogenesis of multiple myeloma (MM) by preventing apoptosis and inducing proliferation. The study aim was to investigate Stat 3 activation in a series of multiple myeloma (MM) cases and its effect on downstream targets such as the anti-apoptotic proteins Bcl-xL, Mcl-1, and Bcl-2, and the cell-cycle protein cyclin D1. Forty-eight cases of MM were analyzed. Immunohistochemistry was performed on paraffin sections using antibodies against cyclin D1, Bcl-2, Bcl-xL, Mcl-1, p21, Stat 3, and Stat 3 phosphorylated (P). Their specificity was corroborated by Western blot analysis using eight human MM cell lines as control. The proliferation rate was assessed with the antibody MiB1. In addition, the mRNA levels of cyclin D1 and Stat 3 were determined by quantitative real-time reverse transcriptase-polymerase chain reaction of paraffin-embedded microdissected tissue. Three different groups determined by the expression of Stat 3P and cyclin D1 (protein and mRNA) were identified: group 1, Stat 3-activated (23 cases, 48%). All cases revealed nuclear expression of Stat 3P. No elevation of Stat 3 mRNA was identified in any of the cases. Three cases in this group showed intermediate to low cyclin D1 protein and mRNA expression. Group 2 included 15 (31%) cases with cyclin D1 staining and lack of Stat 3P. All cases showed intermediate to high levels of cyclin D1 mRNA expression. Group 3 included 10 (21%) cases with no expression of either cyclin D1 or Stat 3P. High levels of anti-apoptotic proteins Bcl-xL and Mcl-1 were identified in 89% and 100% of all cases, respectively. In contrast to Bcl-xL and Mcl-1, the expression of Bcl-2 showed an inverse correlation with proliferation rate (P: 0.0003). No significant differences were found between the three

Cisplatin ototoxicity involves cytokines and STAT6 signaling network

Institute of Scientific and Technical Information of China (English)

Hyung-Jin Kim; Jeong-Dug Sul; Channy Park; Sang-Young Chung; Sung-Kyun Moon; David J Lim; Hong-Seob So; Raekil Park; Gi-Su Oh; Jeong-Han Lee; Ah-Ra Lyu; Hye-Min Ji; Sang-Heon Lee; Jeho Song; Sung-Joo Park; Yong-Ouk You

2011-01-01

We herein investigated the role of the STAT signaling cascade in the production of pro-inflammatory cytokines and cisplatin ototoxicity. A significant hearing impairment caused by cisplatin injection was observed in Balb/c (wild type,WT) and STAT4-/-,but not in STAT6-/- mice. Moreover,the expression levels of the protein and mRNA of proinflammatory cytokines,including TNF-α,IL-1β,and IL-6,were markedly increased in the serum and cochlea of WT and STAT4+,but not STAT6-/- mice. Organotypic culture revealed that the shape of stereocilia bundles and arrays of sensory hair cell layers in the organ of Corti from STAT6-/- mice were intact after treatment with cisplatin,whereas those from WT and STAT4-/- mice were highly distorted and disarrayed after the treatment. Cisplatin induced the phosphorylation of STAT6 in HEI-OC1 auditory cells,and the knockdown of STAT6 by STAT6-specific siRNA significantly protected HEI-OC1 auditory cells from cisplatin-induced cell death and inhibited pro-inflammatory cytokine production. We further demonstrated that IL-4 and IL-13 induced by cisplatin modulated the phosphorylation of STAT6 by binding with IL-4 receptor alpha and IL-13Rα1. These findings suggest that STAT6 signaling plays a pivotal role in cisplatin-mediated pro-inflammatory cytokine production and ototoxicity.

Tetrandrine has anti-adipogenic effect on 3T3-L1 preadipocytes through the reduced expression and/or phosphorylation levels of C/EBP-α, PPAR-γ, FAS, perilipin A, and STAT-3

International Nuclear Information System (INIS)

Jang, Byeong-Churl

2016-01-01

Tetrandrine is a bisbenzylisoquinoline alkaloid isolated from the roots of Stephania tetrandra S. Moore and has been shown to possess anti-inflammatory and anti-cancerous activities. In this study, the effect of tetrandrine on adipogenesis in 3T3-L1 preadipocytes was investigated. Tetrandrine at 10 μM concentration strongly inhibited lipid accumulation and triglyceride (TG) synthesis during the differentiation of 3T3-L1 preadipocytes into adipocytes. On mechanistic levels, tetrandrine reduced not only the expressions of CCAAT/enhancer-binding protein-α (C/EBP-α), peroxisome proliferator-activated receptor-γ (PPAR-γ), fatty acid synthase (FAS), and perilipin A but also the phosphorylation levels of signal transducer and activator of transcription-3 (STAT-3) during 3T3-L1 adipocyte differentiation. Tetrandrine also reduced the mRNA expression of leptin, but not adiponectin, during 3T3-L1 adipocyte differentiation. Collectively, these findings show that tetrandrine has strong anti-adipogenic effect on 3T3-L1 preadipocytes and the effect is largely attributable to the reduced expression and/or phosphorylation levels of C/EBP-α, PPAR-γ, FAS, perilipin A, and STAT-3. - Highlights: • Tetrandrine, a bisbenzylisoquinoline alkaloid, inhibits adipogenesis. • Tetrandrine inhibits C/EBP-α, PPAR-γ, FAS, perilipin A, and STAT-3 in 3T3-L1 adipocytes. • Tetrandrine reduces leptin, but not adiponectin, expression in 3T3-L1 adipocytes. • Tetrandrine may thus have therapeutic potential against obesity.

Tetrandrine has anti-adipogenic effect on 3T3-L1 preadipocytes through the reduced expression and/or phosphorylation levels of C/EBP-α, PPAR-γ, FAS, perilipin A, and STAT-3

Energy Technology Data Exchange (ETDEWEB)

Jang, Byeong-Churl, E-mail: jangbc123@gw.kmu.ac.kr

2016-08-05

Tetrandrine is a bisbenzylisoquinoline alkaloid isolated from the roots of Stephania tetrandra S. Moore and has been shown to possess anti-inflammatory and anti-cancerous activities. In this study, the effect of tetrandrine on adipogenesis in 3T3-L1 preadipocytes was investigated. Tetrandrine at 10 μM concentration strongly inhibited lipid accumulation and triglyceride (TG) synthesis during the differentiation of 3T3-L1 preadipocytes into adipocytes. On mechanistic levels, tetrandrine reduced not only the expressions of CCAAT/enhancer-binding protein-α (C/EBP-α), peroxisome proliferator-activated receptor-γ (PPAR-γ), fatty acid synthase (FAS), and perilipin A but also the phosphorylation levels of signal transducer and activator of transcription-3 (STAT-3) during 3T3-L1 adipocyte differentiation. Tetrandrine also reduced the mRNA expression of leptin, but not adiponectin, during 3T3-L1 adipocyte differentiation. Collectively, these findings show that tetrandrine has strong anti-adipogenic effect on 3T3-L1 preadipocytes and the effect is largely attributable to the reduced expression and/or phosphorylation levels of C/EBP-α, PPAR-γ, FAS, perilipin A, and STAT-3. - Highlights: • Tetrandrine, a bisbenzylisoquinoline alkaloid, inhibits adipogenesis. • Tetrandrine inhibits C/EBP-α, PPAR-γ, FAS, perilipin A, and STAT-3 in 3T3-L1 adipocytes. • Tetrandrine reduces leptin, but not adiponectin, expression in 3T3-L1 adipocytes. • Tetrandrine may thus have therapeutic potential against obesity.

Artesunate inhibits adipogeneis in 3T3-L1 preadipocytes by reducing the expression and/or phosphorylation levels of C/EBP-α, PPAR-γ, FAS, perilipin A, and STAT-3

Energy Technology Data Exchange (ETDEWEB)

Jang, Byeong-Churl, E-mail: jangbc123@gw.kmu.ac.kr

2016-05-20

Differentiation of preadipocyte, also called adipogenesis, leads to the phenotype of mature adipocyte. However, excessive adipogenesis is closely linked to the development of obesity. Artesunate, one of artemisinin-type sesquiterpene lactones from Artemisia annua L., is known for anti-malarial and anti-cancerous activities. In this study, we investigated the effect of artesunate on adipogenesis in 3T3-L1 preadipocytes. Artesunate strongly inhibited lipid accumulation and triglyceride (TG) synthesis during the differentiation of 3T3-L1 preadipocytes into adipocytes at 5 μM concentration. Artesunate at 5 μM also reduced not only the expressions of CCAAT/enhancer-binding protein-α (C/EBP-α), peroxisome proliferator-activated receptor-γ (PPAR-γ), fatty acid synthase (FAS), and perilipin A but also the phosphorylation levels of signal transducer and activator of transcription-3 (STAT-3) during adipocyte differentiation. Moreover, artesunate at 5 μM reduced leptin, but not adiponectin, mRNA expression during adipocyte differentiation. Taken together, these findings demonstrate that artesunate inhibits adipogenesis in 3T3-L1 preadipoytes through the reduced expression and/or phosphorylation levels of C/EBP-α, PPAR-γ, FAS, perilipin A, and STAT-3. -- Highlights: •Artesunate, an artemisinin derivative, inhibits adipogenesis. •Artesunate inhibits C/EBP-α, PPAR-γ, FAS, perilipin A, and STAT-3 in 3T3-L1 adipocytes. •Artesunate reduces leptin, but not adiponectin, expression in 3T3-L1 adipocytes. •Artesunate thus may have therapeutic potential against obesity.

Analysis of STAT1 activation by six FGFR3 mutants associated with skeletal dysplasia undermines dominant role of STAT1 in FGFR3 signaling in cartilage.

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Pavel Krejci

Full Text Available Activating mutations in FGFR3 tyrosine kinase cause several forms of human skeletal dysplasia. Although the mechanisms of FGFR3 action in cartilage are not completely understood, it is believed that the STAT1 transcription factor plays a central role in pathogenic FGFR3 signaling. Here, we analyzed STAT1 activation by the N540K, G380R, R248C, Y373C, K650M and K650E-FGFR3 mutants associated with skeletal dysplasias. In a cell-free kinase assay, only K650M and K650E-FGFR3 caused activatory STAT1(Y701 phosphorylation. Similarly, in RCS chondrocytes, HeLa, and 293T cellular environments, only K650M and K650E-FGFR3 caused strong STAT1 activation. Other FGFR3 mutants caused weak (HeLa or no activation (293T and RCS. This contrasted with ERK MAP kinase activation, which was strongly induced by all six mutants and correlated with the inhibition of proliferation in RCS chondrocytes. Thus the ability to activate STAT1 appears restricted to the K650M and K650E-FGFR3 mutants, which however account for only a small minority of the FGFR3-related skeletal dysplasia cases. Other pathways such as ERK should therefore be considered as central to pathological FGFR3 signaling in cartilage.

[Protein kinase A inhibitor H-89 blocks polyploidization of SP600125-induced CMK cells by regulating phosphorylation of ribosomal protein S6 kinase 1].

Science.gov (United States)

Zhao, Song; Yang, Jingang; Li, Changling; Xing, Sining; Yu, Ying; Liu, Shuo; Pu, Feifei; Ma, Dongchu

2016-10-01

Objective To investigate the regulatory effect of post-translation modification of ribosomal protein S6 kinase 1 (S6K1) on the polyploidization of megakaryocytes. Methods SP600125, a c-Jun N-terminal kinase (JNK) inhibitor, and H-89, a cAMP-dependent protein kinase (PKA) inhibitor, were used to treat CMK cells separately or in combination. With propidium iodide (PI) to dye DNA in the treated cells, the relative DNA content was detected by flow cytometry, and then the DNA polyploidy was analyzed. The change of expression and phosphorylation of ribosomal protein S6 kinase 1 (S6K1), an important mammalian target of rapamycin (mTOR) downstream target molecule, was analyzed by Western blotting. Molecular docking study and kinase activity assay were performed to analyze the combination of H-89 with S6K1 and the effect of H-89 on the activity of S6K1 kinase. Results SP600125 induced CMK cell polyploidization in a time-dependent and dose-dependent manner. At the same time, it increased the phosphorylation of S6K1 at Thr421/Ser424 and decreased the phosphorylation of S6K1 at Thr389. H-89 not only blocked polyploidization, but also decreased the phosphorylation of S6K1 at Thr421/Ser424 and increased the phosphorylation of S6K1 at Thr389. Molecular docking and kinase activity assay showed that H-89 occupied the ATP binding sites of S6K1 and inhibited its activity. Noticeably, both H-89 and SP600125 inhibited the activity of PKA. Moreover, the two drugs further inhibited the activity of PKA when used together. Therefore, these data indicated that H-89 blocked the SP600125-induced polyploidization of CMK cells mainly by changing S6K1 phosphorylation state, rather than its inhibitory effect on PKA. Conclusion H-89 can block the polyploidization of SP600125-induced CMK cells by regulating S6K1 phosphorylation state.

Different associations of CD45 isoforms with STAT3, PKC and ERK regulate IL-6-induced proliferation in myeloma.

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Xu Zheng

Full Text Available In response to interleukin 6 (IL-6 stimulation, both CD45RO and CD45RB, but not CD45RA, translocate to lipid rafts. However, the significance of this distinct translocation and the downstream signals in CD45 isoforms-participated IL-6 signal are not well understood. Using sucrose fractionation, we found that phosphorylated signal transducer and activator of transcription (STAT3 and STAT1 were mainly localized in lipid rafts in response to IL-6 stimulation, despite both STAT3 and STAT1 localizing in raft and non-raft fractions in the presence or absence of IL-6. On the other hand, extracellular signal-regulated kinase (ERK, and phosphorylated ERK were localized in non-raft fractions regardless of the existence of IL-6. The rafts inhibitor significantly impeded the phosphorylation of STAT3 and STAT1 and nuclear translocation, but had little effect on (and only postponing the phosphorylation of ERK. This data suggests that lipid raft-dependent STAT3 and STAT1 pathways are dominant pathways of IL-6 signal in myeloma cells. Interestingly, the phosphorylation level of STAT3 but not STAT1 in CD45+ cells was significantly higher compared to that of CD45- cells, while the phosphorylation level of ERK in CD45+ myeloma cells was relatively low. Furthermore, exogenously expressed CD45RO/RB significantly enhanced STAT3, protein kinase C (PKC and downstream NF-κB activation; however, CD45RA/RB inhibited IL-6-induced ERK phosphorylation. CD45 also enhanced the nuclear localization of STAT3 but not that of STAT1. In response to IL-6 stimulation, CD45RO moved into raft compartments and formed a complex with STAT3 and PKC in raft fraction, while CD45RA remained outside of lipid rafts and formed a complex with ERK in non-raft fraction. This data suggests a different role of CD45 isoforms in IL-6-induced signaling, indicating that while CD45RA/RB seems inhibit the rafts-unrelated ERK pathway, CD45RO/RB may actually work to enhance the rafts-related STAT3 and PKC

Epigallocatechin-3-gallate Ameliorates Seawater Aspiration-Induced Acute Lung Injury via Regulating Inflammatory Cytokines and Inhibiting JAK/STAT1 Pathway in Rats

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Liu, Wei; Dong, Mingqing; Bo, Liyan; Li, Congcong; Liu, Qingqing; Li, Yanyan; Ma, Lijie; Xie, Yonghong; Fu, Enqing; Mu, Deguang; Pan, Lei; Jin, Faguang; Li, Zhichao

2014-01-01

Signal transducers and activators of transcriptions 1 (STAT1) play an important role in the inflammation process of acute lung injury (ALI). Epigallocatechin-3-gallate (EGCG) exhibits a specific and strong anti-STAT1 activity. Therefore, our study is to explore whether EGCG pretreatment can ameliorate seawater aspiration-induced ALI and its possible mechanisms. We detected the arterial partial pressure of oxygen, lung wet/dry weight ratios, protein content in bronchoalveolar lavage fluid, and the histopathologic and ultrastructure staining of the lung. The levels of IL-1, TNF-α, and IL-10 and the total and the phosphorylated protein level of STAT1, JAK1, and JAK2 were assessed in vitro and in vivo. The results showed that EGCG pretreatment significantly improved hypoxemia and histopathologic changes, alleviated pulmonary edema and lung vascular leak, reduced the production of TNF-α and IL-1, and increased the production of IL-10 in seawater aspiration-induced ALI rats. EGCG also prevented the seawater aspiration-induced increase of TNF-α and IL-1 and decrease of IL-10 in NR8383 cell line. Moreover, EGCG pretreatment reduced the total and the phosphorylated protein level of STAT1 in vivo and in vitro and reduced the phosphorylated protein level of JAK1 and JAK2. The present study demonstrates that EGCG ameliorates seawater aspiration-induced ALI via regulating inflammatory cytokines and inhibiting JAK/STAT1 pathway in rats. PMID:24692852

Withaferin A Inhibits STAT3 and Induces Tumor Cell Death in Neuroblastoma and Multiple Myeloma

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Lisette P. Yco

2014-01-01

Full Text Available Signal transducer and activator of transcription 3 (STAT3 is an oncogenic transcription factor that has been implicated in many human cancers and has emerged as an ideal target for cancer therapy. Withaferin A (WFA is a natural product with promising antiproliferative properties through its association with a number of molecular targets including STAT3. However, the effect of WFA in pediatric neuroblastoma (NB and its interaction with STAT3 have not been reported. In this study, we found that WFA effectively induces dose-dependent cell death in high-risk and drug-resistant NB as well as multiple myeloma (MM tumor cells, prevented interleukin-6 (IL-6–mediated and persistently activated STAT3 phosphorylation at Y705, and blocked the transcriptional activity of STAT3. We further provide computational models that show that WFA binds STAT3 near the Y705 phosphotyrosine residue of the STAT3 Src homology 2 (SH2 domain, suggesting that WFA prevents STAT3 dimer formation similar to BP-1-102, a well-established STAT3 inhibitor. Our findings propose that the antitumor activity of WFA is mediated at least in part through inhibition of STAT3 and provide a rationale for further drug development and clinical use in NB and MM.

Direct interaction of natural and synthetic catechins with signal transducer activator of transcription 1 affects both its phosphorylation and activity

KAUST Repository

Menegazzi, Marta

2013-12-10

Our previous studies showed that (-)-epigallocatechin-3-gallate (EGCG) inhibits signal transducer activator of transcription 1 (STAT1) activation. Since EGCG may be a promising lead compound for new anti-STAT1 drug design, 15 synthetic catechins, characterized by the (-)-gallocatechin-3-gallate stereochemistry, were studied in the human mammary MDA-MB-231 cell line to identify the minimal structural features that preserve the anti-STAT1 activity. We demonstrate that the presence of three hydroxyl groups of B ring and one hydroxyl group in D ring is essential to preserve their inhibitory action. Moreover, a possible molecular target of these compounds in the STAT1 pathway was investigated. Our results demonstrate a direct interaction between STAT1 protein and catechins displaying anti-STAT1 activity. In particular, surface plasmon resonance (SPR) analysis and molecular modeling indicate the presence of two putative binding sites (a and b) with different affinity. Based on docking data, site-directed mutagenesis was performed, and interaction of the most active catechins with STAT1 was studied with SPR to test whether Gln518 on site a and His568 on site b could be important for the catechin-STAT1 interaction. Data indicate that site b has higher affinity for catechins than site a as the highest affinity constant disappears in the H568ASTAT1 mutant. Furthermore, Janus kinase 2 (JAK2) kinase assay data suggest that the contemporary presence in vitro of STAT1 and catechins inhibits JAK2-elicited STAT1 phosphorylation. The very tight catechin-STAT1 interaction prevents STAT1 phosphorylation and represents a novel, specific and efficient molecular mechanism for the inhibition of STAT1 activation. © Copyright 2014 Federation of European Biochemical Societies. All rights reserved.

Dietary agent, benzyl isothiocyanate inhibits signal transducer and activator of transcription 3 phosphorylation and collaborates with sulforaphane in the growth suppression of PANC-1 cancer cells

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Deangelis Stephanie

2009-08-01

Full Text Available Abstract The Signal Transducer and Activator of Transcription (STAT proteins comprise a family of latent transcription factors with diverse functions. STAT3 has well established roles in cell proliferation, growth and survival, and its persistent activation has been detected with high frequency in many human cancers. As constitutive activation of STAT3 appears to be vital for the continued survival of these cancerous cells, it has emerged as an attractive target for chemotherapeutics. We examined whether the inhibitory activities of bioactive compounds from cruciferous vegetables, such as Benzyl isothiocyanate (BITC and sulforaphane, extended to STAT3 activation in PANC-1 human pancreatic cancer cells. BITC and sulforaphane were both capable of inhibiting cell viability and inducing apoptosis in PANC-1. Sulforaphane had minimal effect on the direct inhibition of STAT3 tyrosine phosphorylation, however, suggesting its inhibitory activities are most likely STAT3-independent. Conversely, BITC was shown to inhibit the tyrosine phosphorylation of STAT3, but not the phosphorylation of ERK1/2, MAPK and p70S6 kinase. These results suggest that STAT3 may be one of the targets of BITC-mediated inhibition of cell viability in PANC-1 cancer cells. In addition, we show that BITC can prevent the induction of STAT3 activation by Interleukin-6 in MDA-MB-453 breast cancer cells. Furthermore, combinations of BITC and sulforaphane inhibited cell viability and STAT3 phosphorylation more dramatically than either agent alone. These findings suggest that the combination of the dietary agents BITC and sulforaphane has potent inhibitory activity in pancreatic cancer cells and that they may have translational potential as chemopreventative or therapeutic agents.

STAT3 Activities and Energy Metabolism: Dangerous Liaisons

Energy Technology Data Exchange (ETDEWEB)

Camporeale, Annalisa, E-mail: annalisa.camporeale@unito.it [Molecular Biotechnology Center and Department of Molecular Biotechnology and Life Sciences, University of Turin, Via Nizza 52, Turin 10126 (Italy); Demaria, Marco [Buck Institute for Research on Aging, 8001 Redwood Blvd, Novato, CA 94945 (United States); Monteleone, Emanuele [Molecular Biotechnology Center and Department of Molecular Biotechnology and Life Sciences, University of Turin, Via Nizza 52, Turin 10126 (Italy); Giorgi, Carlotta [Department of Experimental and Diagnostic Medicine, Section of General Pathology, Laboratory for Technologies of Advances Therapies (LTTA), University of Ferrara, Via Fossato di Mortara 70, Ferrara 44121 (Italy); Wieckowski, Mariusz R. [Nencki Institute of Experimental Biology, Department of Biochemistry, Pasteur Str. 3, Warsaw 02-093 (Poland); Pinton, Paolo [Department of Experimental and Diagnostic Medicine, Section of General Pathology, Laboratory for Technologies of Advances Therapies (LTTA), University of Ferrara, Via Fossato di Mortara 70, Ferrara 44121 (Italy); Poli, Valeria, E-mail: annalisa.camporeale@unito.it [Molecular Biotechnology Center and Department of Molecular Biotechnology and Life Sciences, University of Turin, Via Nizza 52, Turin 10126 (Italy)

2014-07-31

STAT3 mediates cytokine and growth factor receptor signalling, becoming transcriptionally active upon tyrosine 705 phosphorylation (Y-P). Constitutively Y-P STAT3 is observed in many tumors that become addicted to its activity, and STAT3 transcriptional activation is required for tumor transformation downstream of several oncogenes. We have recently demonstrated that constitutively active STAT3 drives a metabolic switch towards aerobic glycolysis through the transcriptional induction of Hif-1α and the down-regulation of mitochondrial activity, in both MEF cells expressing constitutively active STAT3 (Stat3{sup C/C}) and STAT3-addicted tumor cells. This novel metabolic function is likely involved in mediating pre-oncogenic features in the primary Stat3{sup C/C} MEFs such as resistance to apoptosis and senescence and rapid proliferation. Moreover, it strongly contributes to the ability of primary Stat3{sup C/C} MEFs to undergo malignant transformation upon spontaneous immortalization, a feature that may explain the well known causative link between STAT3 constitutive activity and tumor transformation under chronic inflammatory conditions. Taken together with the recently uncovered role of STAT3 in regulating energy metabolism from within the mitochondrion when phosphorylated on Ser 727, these data place STAT3 at the center of a hub regulating energy metabolism under different conditions, in most cases promoting cell survival, proliferation and malignant transformation even though with distinct mechanisms.

STAT3 Activities and Energy Metabolism: Dangerous Liaisons

International Nuclear Information System (INIS)

Camporeale, Annalisa; Demaria, Marco; Monteleone, Emanuele; Giorgi, Carlotta; Wieckowski, Mariusz R.; Pinton, Paolo; Poli, Valeria

2014-01-01

STAT3 mediates cytokine and growth factor receptor signalling, becoming transcriptionally active upon tyrosine 705 phosphorylation (Y-P). Constitutively Y-P STAT3 is observed in many tumors that become addicted to its activity, and STAT3 transcriptional activation is required for tumor transformation downstream of several oncogenes. We have recently demonstrated that constitutively active STAT3 drives a metabolic switch towards aerobic glycolysis through the transcriptional induction of Hif-1α and the down-regulation of mitochondrial activity, in both MEF cells expressing constitutively active STAT3 (Stat3 C/C ) and STAT3-addicted tumor cells. This novel metabolic function is likely involved in mediating pre-oncogenic features in the primary Stat3 C/C MEFs such as resistance to apoptosis and senescence and rapid proliferation. Moreover, it strongly contributes to the ability of primary Stat3 C/C MEFs to undergo malignant transformation upon spontaneous immortalization, a feature that may explain the well known causative link between STAT3 constitutive activity and tumor transformation under chronic inflammatory conditions. Taken together with the recently uncovered role of STAT3 in regulating energy metabolism from within the mitochondrion when phosphorylated on Ser 727, these data place STAT3 at the center of a hub regulating energy metabolism under different conditions, in most cases promoting cell survival, proliferation and malignant transformation even though with distinct mechanisms

Lung Adenocarcinomas and Lung Cancer Cell Lines Show Association of MMP-1 Expression With STAT3 Activation

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Alexander Schütz

2015-04-01

Full Text Available Signal transducer and activator of transcription 3 (STAT3 is constitutively activated in the majority of lung cancer. This study aims at defining connections between STAT3 function and the malignant properties of non–small cell lung carcinoma (NSCLC cells. To address possible mechanisms by which STAT3 influences invasiveness, the expression of matrix metalloproteinase-1 (MMP-1 was analyzed and correlated with the STAT3 activity status. Studies on both surgical biopsies and on lung cancer cell lines revealed a coincidence of STAT3 activation and strong expression of MMP-1. MMP-1 and tyrosine-phosphorylated activated STAT3 were found co-localized in cancer tissues, most pronounced in tumor fronts, and in particular in adenocarcinomas. STAT3 activity was constitutive, although to different degrees, in the lung cancer cell lines investigated. Three cell lines (BEN, KNS62, and A549 were identified in which STAT3 activitation was inducible by Interleukin-6 (IL-6. In A549 cells, STAT3 activity enhanced the level of MMP-1 mRNA and stimulated transcription from the MMP-1 promoter in IL-6–stimulated A549 cells. STAT3 specificity of this effect was confirmed by STAT3 knockdown through RNA interference. Our results link aberrant activity of STAT3 in lung cancer cells to malignant tumor progression through up-regulation of expression of invasiveness-associated MMPs.

Caffeine inhibits STAT1 signaling and downregulates inflammatory pathways involved in autoimmunity.

Science.gov (United States)

Iris, Merve; Tsou, Pei-Suen; Sawalha, Amr H

2018-04-18

Caffeine is a widely consumed pharmacologically active product. We focused on characterizing immunomodulatory effects of caffeine on peripheral blood mononuclear cells. Caffeine at high doses showed a robust downregulatory effect on cytokine activity and genes related to several autoimmune diseases including lupus and rheumatoid arthritis. Dose-dependent validation experiments showed downregulation at the mRNA levels of key inflammation-related genes including STAT1, TNF, IFNG, and PPARG. TNF and PPARG were suppressed even with the lowest caffeine dose tested, which corresponds to the serum concentration of caffeine after administration of one cup of coffee. Cytokine levels of IL-8, MIP-1β, IL-6, IFN-γ, GM-CSF, TNF, IL-2, IL-4, MCP-1, and IL-10 were decreased significantly with caffeine treatment. Upstream regulator analysis suggests that caffeine inhibits STAT1 signaling, which was confirmed by showing reduced phosphorylated STAT1 after caffeine treatment. Further studies exploring disease-modulating potential of caffeine in autoimmune diseases and further exploring the mechanisms involved are warranted. Copyright © 2018 Elsevier Inc. All rights reserved.

An SH2 domain model of STAT5 in complex with phospho-peptides define "STAT5 Binding Signatures".

Science.gov (United States)

Gianti, Eleonora; Zauhar, Randy J

2015-05-01

The signal transducer and activator of transcription 5 (STAT5) is a member of the STAT family of proteins, implicated in cell growth and differentiation. STAT activation is regulated by phosphorylation of protein monomers at conserved tyrosine residues, followed by binding to phospho-peptide pockets and subsequent dimerization. STAT5 is implicated in the development of severe pathological conditions, including many cancer forms. However, nowadays a few STAT5 inhibitors are known, and only one crystal structure of the inactive STAT5 dimer is publicly available. With a view to enabling structure-based drug design, we have: (1) analyzed phospho-peptide binding pockets on SH2 domains of STAT5, STAT1 and STAT3; (2) generated a model of STAT5 bound to phospho-peptides; (3) assessed our model by docking against a class of known STAT5 inhibitors (Müller et al. in ChemBioChem 9:723-727, 2008); (4) used molecular dynamics simulations to optimize the molecular determinants responsible for binding and (5) proposed unique "Binding Signatures" of STAT5. Our results put in place the foundations to address STAT5 as a target for rational drug design, from sequence, structural and functional perspectives.

An SH2 domain model of STAT5 in complex with phospho-peptides define ``STAT5 Binding Signatures''

Science.gov (United States)

Gianti, Eleonora; Zauhar, Randy J.

2015-05-01

The signal transducer and activator of transcription 5 (STAT5) is a member of the STAT family of proteins, implicated in cell growth and differentiation. STAT activation is regulated by phosphorylation of protein monomers at conserved tyrosine residues, followed by binding to phospho-peptide pockets and subsequent dimerization. STAT5 is implicated in the development of severe pathological conditions, including many cancer forms. However, nowadays a few STAT5 inhibitors are known, and only one crystal structure of the inactive STAT5 dimer is publicly available. With a view to enabling structure-based drug design, we have: (1) analyzed phospho-peptide binding pockets on SH2 domains of STAT5, STAT1 and STAT3; (2) generated a model of STAT5 bound to phospho-peptides; (3) assessed our model by docking against a class of known STAT5 inhibitors (Müller et al. in ChemBioChem 9:723-727, 2008); (4) used molecular dynamics simulations to optimize the molecular determinants responsible for binding and (5) proposed unique "Binding Signatures" of STAT5. Our results put in place the foundations to address STAT5 as a target for rational drug design, from sequence, structural and functional perspectives.

Response of brain oxygenation and metabolism to deep hypothermic circulatory arrest in newborn piglets: comparison of pH-stat and alpha-stat strategies.

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Markowitz, Scott D; Mendoza-Paredes, Alberto; Liu, Huiping; Pastuszko, Peter; Schultz, Steven P; Schears, Gregory J; Greeley, William J; Wilson, David F; Pastuszko, Anna

2007-07-01

To determine the effect of pH-stat as compared with alpha-stat management on brain oxygenation, level of striatal extracellular dopamine, phosphorylation, and levels of protein kinase B (Akt) and cyclic adenosine 3', 5'-monophosphate response element-binding protein (CREB), and levels of extracellular signal-regulated kinase (ERK)1/2, Bcl-2, and Bax in a piglet model of deep hypothermic circulatory arrest (DHCA). The piglets were placed on cardiopulmonary bypass (CPB), cooled with pH-stat or alpha-stat to 18 degrees C, subjected to 90 minutes of DHCA, rewarmed, weaned from CPB, and maintained for two hours recovery. The cortical oxygen was measured by: quenching of phosphorescence; dopamine by microdialysis; phosphorylation of CREB (p-CREB), ERK (p-ERK) 1/2, Akt (p-Akt), and level of Bcl-2, Bax by Western blots. Oxygen pressure histograms for the microvasculature of the cortex show substantially higher oxygen levels during cooling and during the oxygen depletion period after cardiac arrest (up to 15 minutes) when using pH-stat compared with alpha-stat management. Significant increases in dopamine occurred at 45 minutes and 60 minutes of DHCA in the alpha-stat and pH-stat groups, respectively. The p-CREB and p-Akt in the pH-stat group were significantly higher than in the alpha-stat group (140 +/- 9%, p model, prolongs "safe" time of DHCA and provides some brain protection against ischemic injury.

Activation of Stat3 in renal tumors.

Science.gov (United States)

Guo, Charles; Yang, Guanyu; Khun, Kyle; Kong, Xiantian; Levy, David; Lee, Peng; Melamed, Jonathan

2009-02-28

Signal transducer and activator of transcription 3 (Stat3) plays a vital role in signal transduction pathways that mediate transformation and inhibit apoptosis. Oncogenic Stat3 is persistently activated in several human cancers and transformed cell lines. Previous studies indicate activation of Stat3 in renal cell carcinoma (RCC). However, the detailed characterization of the Stat3 expression pattern in different histologic types of RCC is lacking. We have analyzed the immunoprofile of activated or phosphorylated Stat3 (pStat3) in a tissue microarray of renal tumors of different histologic types, including 42 cases of conventional clear cell type, 24 chromophobe, and 7 papillary, 15 oncocytoma, 7 urothelial carcinoma and 21 normal kidney tissues using an anti-pStat3 antibody (recognizes only activated STAT3). pStat3 nuclear staining was observed in 25 of 42 conventional clear cell RCC (59.5 %), 8 of 24 chromophobe RCC (33.3%), 4 of 7 papillary RCC (57.1%). In the other tumor groups, 4 of 15 oncocytomas (26.7%) and 6 of 7 urothelial carcinomas (85.7%) showed positive nuclear staining. Weak nuclear immunoreactivity for pStat3 was seen in 4 of 21 cases of non-neoplastic kidney tissue (19.0%). The extent of Stat3 activation as determined by nuclear expression of its phosphorylated form is increased in histologic types of renal tumors with greater malignant potential, specifically conventional clear cell RCC, papillary RCC and urothelial carcinoma, only slightly increased in chromophobe RCC, and not increased in oncocytoma. These results suggest a role of Stat3 activation in different types of renal neoplasia, possibly serving as a prognostic marker or therapeutic target.

The JAK-STAT transcriptional regulator, STAT-5, activates the ATM DNA damage pathway to induce HPV 31 genome amplification upon epithelial differentiation.

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Shiyuan Hong

Full Text Available High-risk human papillomavirus (HPV must evade innate immune surveillance to establish persistent infections and to amplify viral genomes upon differentiation. Members of the JAK-STAT family are important regulators of the innate immune response and HPV proteins downregulate expression of STAT-1 to allow for stable maintenance of viral episomes. STAT-5 is another member of this pathway that modulates the inflammatory response and plays an important role in controlling cell cycle progression in response to cytokines and growth factors. Our studies show that HPV E7 activates STAT-5 phosphorylation without altering total protein levels. Inhibition of STAT-5 phosphorylation by the drug pimozide abolishes viral genome amplification and late gene expression in differentiating keratinocytes. In contrast, treatment of undifferentiated cells that stably maintain episomes has no effect on viral replication. Knockdown studies show that the STAT-5β isoform is mainly responsible for this activity and that this is mediated through the ATM DNA damage response. A downstream target of STAT-5, the peroxisome proliferator-activated receptor γ (PPARγ contributes to the effects on members of the ATM pathway. Overall, these findings identify an important new regulatory mechanism by which the innate immune regulator, STAT-5, promotes HPV viral replication through activation of the ATM DNA damage response.

Inhibition of STAT3 Expression and Signaling in Resveratrol-Differentiated Medulloblastoma Cells

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Li-Jun Yu

2008-07-01

Full Text Available In this study, the potential influence of resveratrol (3,5,4′-trihydroxy-trans-stilbene in signal transducer and activator of transcription 3 (STAT3 signaling of medulloblastoma cells was evaluated by checking the status of STAT3 signaling and its downstream gene expression in two medulloblastoma cell lines (UW228-2 and UW228-3 with and without resveratrol treatment. The results revealed that resveratrol induced neuronal differentiation of medulloblastoma cells. Signal transducer and activator of transcription 3 expression and phosphorylation were detected in normally cultured UW228-2 and UW228-3 cells that were apparently attenuated after resveratrol treatment. The expression of STAT3 downstream genes, survivin, cyclin D1, Cox-2, and c-Myc, was suppressed but Bcl-2 was enhanced by resveratrol. Meanwhile, the production and secretion of leukemia inhibitory factor, a STAT3 activator, became active in resveratrol-treated cells. To further ascertain the significance of STAT3 signaling for medulloblastoma cells, AG490, a selective inhibitor of STAT3 phosphorylation, was used to treat UW228-3 cells. Phosphorylation of STAT3 was inhibited by AG490 accompanied with growth suppression, differentiation-like changes, and down-regulation of survivin, cyclin D1, Cox-2, and c-Myc. Our data thus suggest the importance of STAT3 signaling in maintenance and survival of medulloblastoma cells. This signaling may be the major target of resveratrol. Enhanced leukemia inhibitory factor and Bcl-2 expressions in resveratrol-treated cells might reflect a compensatory response to the loss of STAT3 function.

PKCδ-mediated IRS-1 Ser24 phosphorylation negatively regulates IRS-1 function

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Greene, Michael W.; Ruhoff, Mary S.; Roth, Richard A.; Kim, Jeong-a; Quon, Michael J.; Krause, Jean A.

2006-01-01

The IRS-1 PH and PTB domains are essential for insulin-stimulated IRS-1 Tyr phosphorylation and insulin signaling, while Ser/Thr phosphorylation of IRS-1 disrupts these signaling events. To investigate consensus PKC phosphorylation sites in the PH-PTB domains of human IRS-1, we changed Ser24, Ser58, and Thr191 to Ala (3A) or Glu (3E), to block or mimic phosphorylation, respectively. The 3A mutant abrogated the inhibitory effect of PKCδ on insulin-stimulated IRS-1 Tyr phosphorylation, while reductions in insulin-stimulated IRS-1 Tyr phosphorylation, cellular proliferation, and Akt activation were observed with the 3E mutant. When single Glu mutants were tested, the Ser24 to Glu mutant had the greatest inhibitory effect on insulin-stimulated IRS-1 Tyr phosphorylation. PKCδ-mediated IRS-1 Ser24 phosphorylation was confirmed in cells with PKCδ catalytic domain mutants and by an RNAi method. Mechanistic studies revealed that IRS-1 with Ala and Glu point mutations at Ser24 impaired phosphatidylinositol-4,5-bisphosphate binding. In summary, our data are consistent with the hypothesis that Ser24 is a negative regulatory phosphorylation site in IRS-1

Canonical and Non-Canonical Aspects of JAK-STAT Signaling: Lessons from Interferons for Cytokine Responses.

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Majoros, Andrea; Platanitis, Ekaterini; Kernbauer-Hölzl, Elisabeth; Rosebrock, Felix; Müller, Mathias; Decker, Thomas

2017-01-01

Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signal transduction mediates cytokine responses. Canonical signaling is based on STAT tyrosine phosphorylation by activated JAKs. Downstream of interferon (IFN) receptors, activated JAKs cause the formation of the transcription factors IFN-stimulated gene factor 3 (ISGF3), a heterotrimer of STAT1, STAT2 and interferon regulatory factor 9 (IRF9) subunits, and gamma interferon-activated factor (GAF), a STAT1 homodimer. In recent years, several deviations from this paradigm were reported. These include kinase-independent JAK functions as well as extra- and intranuclear activities of U-STATs without phosphotyrosines. Additionally, transcriptional control by STAT complexes resembling neither GAF nor ISGF3 contributes to transcriptome changes in IFN-treated cells. Our review summarizes the contribution of non-canonical JAK-STAT signaling to the innate antimicrobial immunity imparted by IFN. Moreover, we touch upon functions of IFN pathway proteins beyond the IFN response. These include metabolic functions of IRF9 as well as the regulation of natural killer cell activity by kinase-dead TYK2 and different phosphorylation isoforms of STAT1.

PCBP2 enhances the antiviral activity of IFN-α against HCV by stabilizing the mRNA of STAT1 and STAT2.

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Zhongshuai Xin

Full Text Available Interferon-α (IFN-α is a natural choice for the treatment of hepatitis C, but half of the chronically infected individuals do not achieve sustained clearance of hepatitis C virus (HCV during treatment with IFN-α alone. The virus can impair IFN-α signaling and cellular factors that have an effect on the viral life cycles. We found that the protein PCBP2 is down-regulated in HCV-replicon containing cells (R1b. However, the effects and mechanisms of PCBP2 on HCV are unclear. To determine the effect of PCBP2 on HCV, overexpression and knockdown of PCBP2 were performed in R1b cells. Interestingly, we found that PCBP2 can facilitate the antiviral activity of IFN-α against HCV, although the RNA level of HCV was unaffected by either the overexpression or absence of PCBP2 in R1b cells. RIP-qRT-PCR and RNA half-life further revealed that PCBP2 stabilizes the mRNA of STAT1 and STAT2 through binding the 3'Untranslated Region (UTR of these two molecules, which are pivotal for the IFN-α anti-HCV effect. RNA pull-down assay confirmed that there were binding sites located in the C-rich tracts in the 3'UTR of their mRNAs. Stabilization of mRNA by PCBP2 leads to the increased protein expression of STAT1 and STAT2 and a consistent increase of phosphorylated STAT1 and STAT2. These effects, in turn, enhance the antiviral effect of IFN-α. These findings indicate that PCBP2 may play an important role in the IFN-α response against HCV and may benefit the HCV clinical therapy.

Target specificity, in vivo pharmacokinetics, and efficacy of the putative STAT3 inhibitor LY5 in osteosarcoma, Ewing's sarcoma, and rhabdomyosarcoma.

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Peter Y Yu

Full Text Available STAT3 is a transcription factor involved in cytokine and receptor kinase signal transduction that is aberrantly activated in a variety of sarcomas, promoting metastasis and chemotherapy resistance. The purpose of this work was to develop and test a novel putative STAT3 inhibitor, LY5.An in silico fragment-based drug design strategy was used to create LY5, a small molecule inhibitor that blocks the STAT3 SH2 domain phosphotyrosine binding site, inhibiting homodimerization. LY5 was evaluated in vitro demonstrating good biologic activity against rhabdomyosarcoma, osteosarcoma and Ewing's sarcoma cell lines at high nanomolar/low micromolar concentrations, as well as specific inhibition of STAT3 phosphorylation without effects on other STAT3 family members. LY5 exhibited excellent oral bioavailability in both mice and healthy dogs, and drug absorption was enhanced in the fasted state with tolerable dosing in mice at 40 mg/kg BID. However, RNAi-mediated knockdown of STAT3 did not phenocopy the biologic effects of LY5 in sarcoma cell lines. Moreover, concentrations needed to inhibit ex vivo metastasis growth using the PuMA assay were significantly higher than those needed to inhibit STAT3 phosphorylation in vitro. Lastly, LY5 treatment did not inhibit the growth of sarcoma xenografts or prevent pulmonary metastasis in mice.LY5 is a novel small molecule inhibitor that effectively inhibits STAT3 phosphorylation and cell proliferation at nanomolar concentrations. LY5 demonstrates good oral bioavailability in mice and dogs. However LY5 did not decrease tumor growth in xenograft mouse models and STAT3 knockdown did not induce concordant biologic effects. These data suggest that the anti-cancer effects of LY5 identified in vitro were not mediated through STAT3 inhibition.

Target specificity, in vivo pharmacokinetics, and efficacy of the putative STAT3 inhibitor LY5 in osteosarcoma, Ewing's sarcoma, and rhabdomyosarcoma.

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Yu, Peter Y; Gardner, Heather L; Roberts, Ryan; Cam, Hakan; Hariharan, Seethalakshmi; Ren, Ling; LeBlanc, Amy K; Xiao, Hui; Lin, Jiayuh; Guttridge, Denis C; Mo, Xiaokui; Bennett, Chad E; Coss, Christopher C; Ling, Yonghua; Phelps, Mitch A; Houghton, Peter; London, Cheryl A

2017-01-01

STAT3 is a transcription factor involved in cytokine and receptor kinase signal transduction that is aberrantly activated in a variety of sarcomas, promoting metastasis and chemotherapy resistance. The purpose of this work was to develop and test a novel putative STAT3 inhibitor, LY5. An in silico fragment-based drug design strategy was used to create LY5, a small molecule inhibitor that blocks the STAT3 SH2 domain phosphotyrosine binding site, inhibiting homodimerization. LY5 was evaluated in vitro demonstrating good biologic activity against rhabdomyosarcoma, osteosarcoma and Ewing's sarcoma cell lines at high nanomolar/low micromolar concentrations, as well as specific inhibition of STAT3 phosphorylation without effects on other STAT3 family members. LY5 exhibited excellent oral bioavailability in both mice and healthy dogs, and drug absorption was enhanced in the fasted state with tolerable dosing in mice at 40 mg/kg BID. However, RNAi-mediated knockdown of STAT3 did not phenocopy the biologic effects of LY5 in sarcoma cell lines. Moreover, concentrations needed to inhibit ex vivo metastasis growth using the PuMA assay were significantly higher than those needed to inhibit STAT3 phosphorylation in vitro. Lastly, LY5 treatment did not inhibit the growth of sarcoma xenografts or prevent pulmonary metastasis in mice. LY5 is a novel small molecule inhibitor that effectively inhibits STAT3 phosphorylation and cell proliferation at nanomolar concentrations. LY5 demonstrates good oral bioavailability in mice and dogs. However LY5 did not decrease tumor growth in xenograft mouse models and STAT3 knockdown did not induce concordant biologic effects. These data suggest that the anti-cancer effects of LY5 identified in vitro were not mediated through STAT3 inhibition.

Inhibitory Effect of Curcumol on Jak2-STAT Signal Pathway Molecules of Fibroblast-Like Synoviocytes in Patients with Rheumatoid Arthritis

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Heng Wang

2012-01-01

Full Text Available Hyperplasia of synovial membrane in rheumatoid arthritis (RA is a critical pathological foundation for inducing articular injury. The janus kinase and signal transducer and activator of transcription (Jak-STAT pathway plays a critical role in synovial membrane proliferation induced by platelet-derived growth factor (PDGF. To explore the anti-cell proliferation mechanism of curcumol, a pure monomer extracted from Chinese medical plant zedoary rhizome, the changes of Jak2-STAT1/3 signal pathway-related molecules in synoviocytes were observed in vitro. In this study, the fibroblast-like synoviocytes (FLS in patients with RA were collected and cultured. The following parameters were measured: cell proliferation (WST-1 assay, cell cycles (fluorescence-activated cell sorting, FACS, STAT1 and STAT3 activities (electrophoretic mobility shift assay, EMSA, and the protein expressions of phosphorylated Jak2, STAT1, and STAT3 (Western blot. It was shown that curcumol could inhibit the RA-FLS proliferation and DNA synthesis induced by PDGF-BB in a dose-dependent manner in vitro. The transcription factors activities of STAT1 and STAT3 were obviously elevated after PDGF-BB stimulation (P<0.05. Super-shift experiments identified the STAT1 or STAT3 proteins in the complex. Furthermore, the different concentration curcumol could downregulate the DNA binding activities of STAT1 and STAT3 (P<0.05 and inhibit the phosphorylation of Jak2 while it had no effect on the protein expressions of STAT1 and STAT3. Positive correlations were found between changes of cell proliferation and DNA-binding activities of STAT1 and STAT3, respectively (P<0.01. In conclusion, curcumol might suppress the FLS proliferation and DNA synthesis induced by PDGF-BB through attenuating Jak2 phosphorylation, downregulating STAT1 and STAT3 DNA-binding activities, which could provide theoretical foundation for clinical treatment of RA.

Benzyl isothiocyanate suppresses pancreatic tumor angiogenesis and invasion by inhibiting HIF-α/VEGF/Rho-GTPases: pivotal role of STAT-3.

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Srinivas Reddy Boreddy

Full Text Available Our previous studies have shown that benzyl isothiocyanate (BITC suppresses pancreatic tumor growth by inhibiting STAT-3; however, the exact mechanism of tumor growth suppression was not clear. Here we evaluated the effects and mechanism of BITC on pancreatic tumor angiogenesis. Our results reveal that BITC significantly inhibits neovasularization on rat aorta and Chicken-Chorioallantoic membrane. Furthermore, BITC blocks the migration and invasion of BxPC-3 and PanC-1 pancreatic cancer cells in a dose dependant manner. Moreover, secretion of VEGF and MMP-2 in normoxic and hypoxic BxPC-3 and PanC-1 cells was significantly suppressed by BITC. Both VEGF and MMP-2 play a critical role in angiogenesis and metastasis. Our results reveal that BITC significantly suppresses the phosphorylation of VEGFR-2 (Tyr-1175, and expression of HIF-α. Rho-GTPases, which are regulated by VEGF play a crucial role in pancreatic cancer progression. BITC treatment reduced the expression of RhoC whereas up-regulated the expression of tumor suppressor RhoB. STAT-3 over-expression or IL-6 treatment significantly induced HIF-1α and VEGF expression; however, BITC substantially suppressed STAT-3 as well as STAT-3-induced HIF-1α and VEGF expression. Finally, in vivo tumor growth and matrigel-plug assay show reduced tumor growth and substantial reduction of hemoglobin content in the matrigel plugs and tumors of mice treated orally with 12 µmol BITC, indicating reduced tumor angiogenesis. Immunoblotting of BITC treated tumors show reduced expression of STAT-3 phosphorylation (Tyr-705, HIF-α, VEGFR-2, VEGF, MMP-2, CD31 and RhoC. Taken together, our results suggest that BITC suppresses pancreatic tumor growth by inhibiting tumor angiogenesis through STAT-3-dependant pathway.

Canonical and Non-Canonical Aspects of JAK–STAT Signaling: Lessons from Interferons for Cytokine Responses

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Majoros, Andrea; Platanitis, Ekaterini; Kernbauer-Hölzl, Elisabeth; Rosebrock, Felix; Müller, Mathias; Decker, Thomas

2017-01-01

Janus kinase (JAK)–signal transducer and activator of transcription (STAT) signal transduction mediates cytokine responses. Canonical signaling is based on STAT tyrosine phosphorylation by activated JAKs. Downstream of interferon (IFN) receptors, activated JAKs cause the formation of the transcription factors IFN-stimulated gene factor 3 (ISGF3), a heterotrimer of STAT1, STAT2 and interferon regulatory factor 9 (IRF9) subunits, and gamma interferon-activated factor (GAF), a STAT1 homodimer. In recent years, several deviations from this paradigm were reported. These include kinase-independent JAK functions as well as extra- and intranuclear activities of U-STATs without phosphotyrosines. Additionally, transcriptional control by STAT complexes resembling neither GAF nor ISGF3 contributes to transcriptome changes in IFN-treated cells. Our review summarizes the contribution of non-canonical JAK–STAT signaling to the innate antimicrobial immunity imparted by IFN. Moreover, we touch upon functions of IFN pathway proteins beyond the IFN response. These include metabolic functions of IRF9 as well as the regulation of natural killer cell activity by kinase-dead TYK2 and different phosphorylation isoforms of STAT1. PMID:28184222

Cyclophilins contribute to Stat3 signaling and survival of multiple myeloma cells.

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Bauer, K; Kretzschmar, A K; Cvijic, H; Blumert, C; Löffler, D; Brocke-Heidrich, K; Schiene-Fischer, C; Fischer, G; Sinz, A; Clevenger, C V; Horn, F

2009-08-06

Signal transducer and activator of transcription 3 (Stat3) is the major mediator of interleukin-6 (IL-6) family cytokines. In addition, Stat3 is known to be involved in the pathophysiology of many malignancies. Here, we show that the cis-trans peptidyl-prolyl isomerase cyclophilin (Cyp) B specifically interacts with Stat3, whereas the highly related CypA does not. CypB knockdown inhibited the IL-6-induced transactivation potential but not the tyrosine phosphorylation of Stat3. Binding of CypB to Stat3 target promoters and alteration of the intranuclear localization of Stat3 on CypB depletion suggested a nuclear function of Stat3/CypB interaction. By contrast, CypA knockdown inhibited Stat3 IL-6-induced tyrosine phosphorylation and nuclear translocation. The Cyp inhibitor cyclosporine A (CsA) caused similar effects. However, Stat1 activation in response to IL-6 or interferon-gamma was not affected by Cyp silencing or CsA treatment. As a result, Cyp knockdown shifted IL-6 signaling to a Stat1-dominated pathway. Furthermore, Cyp depletion or treatment with CsA induced apoptosis in IL-6-dependent multiple myeloma cells, whereas an IL-6-independent line was not affected. Thus, Cyps support the anti-apoptotic action of Stat3. Taken together, CypA and CypB both play pivotal roles, yet at different signaling levels, for Stat3 activation and function. These data also suggest a novel mechanism of CsA action.

STAT1 in cancer: friend or foe?

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Zhang, Ying; Liu, Zhaoyong

2017-08-01

The first STAT family member, STAT1, is an essential component of interferon (IFN)-signaling, which mediates several cellular functions in response to stimulation by cytokines, growth factors, and hormones, such as the IFNs and IL-6. The role and significance of STAT1 in cancer biology have been studied for a decade. The majority of evidence shows that activating STAT1 plays a tumor suppressor role in cancer cells. Nevertheless, results from some experiments and clinical studies suggest that STAT1 also exerts tumor promoter effects under specific conditions. In some malignant phenotypes, STAT1 can function either as an oncoprotein or tumor suppressor in the same cell type, depending on the specific genetic background. Thus, the function of STAT1 in cancer biology remains a mystery. In this review, we discuss both the "friend" and "foe" features of STAT1 by summarizing its tumor suppressor or oncogenic functions and mechanisms. To explain how STAT1 may mediate its tumor suppressor effects, we discuss several possible mechanisms, one of which is linked to the role of STAT1β, an isoform of STAT1.

Icariside II induces apoptosis in U937 acute myeloid leukemia cells: role of inactivation of STAT3-related signaling.

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Sang-Hun Kang

Full Text Available BACKGROUND: The aim of this study is to determine anti-cancer effect of Icariside II purified from the root of Epimedium koreanum Nakai on human acute myeloid leukemia (AML cell line U937. METHODOLOGY/PRINCIPAL FINDINGS: Icariside II blocked the growth U937 cells in a dose- and time-dependent manner. In this anti-proliferation process, this herb compound rendered the cells susceptible to apoptosis, manifested by enhanced accumulation of sub-G1 cell population and increased the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL-positive cells. Icariside II was able to activate caspase-3 and cleaved poly (ADP-ribose polymerase (PARP in a time-dependent manner. Concurrently, the anti-apoptotic proteins, such as bcl-x(L and survivin in U937 cells, were downregulated by Icariside II. In addition, Icariside II could inhibit STAT3 phosphorylation and function and subsequently suppress the activation of Janus activated kinase 2 (JAK2, the upstream activators of STAT3, in a dose- and time-dependent manner. Icariside II also enhanced the expression of protein tyrosine phosphatase (PTP SH2 domain-containing phosphatase (SHP-1, and the addition of sodium pervanadate (a PTP inhibitor prevented Icariside II-induced apoptosis as well as STAT3 inactivation in STAT3 positive U937 cells. Furthermore, silencing SHP-1 using its specific siRNA significantly blocked STAT3 inactivation and apoptosis induced by Icariside II in U937 cells. CONCLUSIONS/SIGNIFICANCE: Our results demonstrated that via targeting STAT3-related signaling, Icariside II sensitizes U937 cells to apoptosis and perhaps serves as a potent chemotherapeutic agent for AML.

IFN regulatory factor 1 restricts hepatitis E virus replication by activating STAT1 to induce antiviral IFN-stimulated genes.

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Xu, Lei; Zhou, Xinying; Wang, Wenshi; Wang, Yijin; Yin, Yuebang; Laan, Luc J W van der; Sprengers, Dave; Metselaar, Herold J; Peppelenbosch, Maikel P; Pan, Qiuwei

2016-10-01

IFN regulatory factor 1 (IRF1) is one of the most important IFN-stimulated genes (ISGs) in cellular antiviral immunity. Although hepatitis E virus (HEV) is a leading cause of acute hepatitis worldwide, how ISGs counteract HEV infection is largely unknown. This study was conducted to investigate the effect of IRF1 on HEV replication. Multiple cell lines were used in 2 models that harbor HEV. In different HEV cell culture systems, IRF1 effectively inhibited HEV replication. IRF1 did not trigger IFN production, and chromatin immunoprecipitation sequencing data analysis revealed that IRF1 bound to the promoter region of signal transducers and activators of transcription 1 (STAT1). Functional assay confirmed that IRF1 could drive the transcription of STAT1, resulting in elevation of total and phosphorylated STAT1 proteins and further activating the transcription of a panel of downstream antiviral ISGs. By pharmacological inhibitors and RNAi-mediated gene-silencing approaches, we revealed that antiviral function of IRF1 is dependent on the JAK-STAT cascade. Furthermore, induction of ISGs and the anti-HEV effect of IRF1 overlapped that of IFNα, but was potentiated by ribavirin. We demonstrated that IRF1 effectively inhibits HEV replication through the activation of the JAK-STAT pathway, and the subsequent transcription of antiviral ISGs, but independent of IFN production.-Xu, L., Zhou, X., Wang, W., Wang, Y., Yin, Y., van der Laan, L. J. W., Sprengers, D., Metselaar, H. J., Peppelenbosch, M. P., Pan, Q. IFN regulatory factor 1 restricts hepatitis E virus replication by activating STAT1 to induce antiviral IFN-stimulated genes. © FASEB.

Therapeutic effect of Cryptotanshinone on experimental rheumatoid arthritis through downregulating p300 mediated-STAT3 acetylation.

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Wang, Ying; Zhou, Chun; Gao, Hui; Li, Cuixian; Li, Dong; Liu, Peiqing; Huang, Min; Shen, Xiaoyan; Liu, Liang

2017-08-15

The balance between T helper 17 (Th17) cells and regulatory T (Treg) cells, plays a critical role in rheumatoid arthritis (RA). The differentiation of Th17 cells requires the activation of STAT3, which determines the balance of Th17/Treg. Here, we investigated the therapeutic effect of Cryptotanshinone (CTS) on collagen induced mouse arthritis and explored the underlying mechanisms. Arthritis was induced in DBA/1 mice with bovine collagen type II and complete Freund's adjuvant. CTS was given at 20mgkg -1 d -1 or 60mgkg -1 d -1 by gavage for 6weeks. The immuno-inflammation and joint destruction were evaluated and the balance of Th17/Treg was determined. STAT3 acetylation and phosphorylation were detected by western blotting, and the involvement of p300 was investigated by siRNA and plasmid overexpression. CTS at a dose of 60mgkg -1 d -1 ameliorated the inflammation and joint destruction in CIA mice. It improved Th17/Treg imbalance, and inhibited both acetylation and phosphorylation of STAT3. CTS reduced p300 expression and its binding to STAT3, but increased phosphorylated AMPK. Knockdown of p300 mimicked the inhibitory effect of CTS on STAT3 acetylation and phosphorylation, which could be partially rescued by overexpression of p300-WT, but not p300-dominant negative (DN) construct. Our study suggested that the anti-arthritis effects of CTS were attained through suppression of p300-mediated STAT3 acetylation. Our data suggest that CTS might be a potential immune modulator for RA treatment. Copyright © 2017 Elsevier Inc. All rights reserved.

Activated Rac1 requires gp130 for Stat3 activation, cell proliferation and migration

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Arulanandam, Rozanne; Geletu, Mulu; Feracci, Helene; Raptis, Leda

2010-01-01

Rac1 (Rac) is a member of the Rho family of small GTPases which controls cell migration by regulating the organization of actin filaments. Previous results suggested that mutationally activated forms of the Rho GTPases can activate the Signal Transducer and Activator of Transcription-3 (Stat3), but the exact mechanism is a matter of controversy. We recently demonstrated that Stat3 activity of cultured cells increases dramatically following E-cadherin engagement. To better understand this pathway, we now compared Stat3 activity levels in mouse HC11 cells before and after expression of the mutationally activated Rac1 (Rac V12 ), at different cell densities. The results revealed for the first time a dramatic increase in protein levels and activity of both the endogenous Rac and Rac V12 with cell density, which was due to inhibition of proteasomal degradation. In addition, Rac V12 -expressing cells had higher Stat3, tyrosine-705 phosphorylation and activity levels at all densities, indicating that Rac V12 is able to activate Stat3. Further examination of the mechanism of Stat3 activation showed that Rac V12 expression caused a surge in mRNA of Interleukin-6 (IL6) family cytokines, known potent Stat3 activators. Knockdown of gp130, the common subunit of this family reduced Stat3 activity, indicating that these cytokines may be responsible for the Stat3 activation by Rac V12 . The upregulation of IL6 family cytokines was required for cell migration and proliferation induced by Rac V12 , as shown by gp130 knockdown experiments, thus demonstrating that the gp130/Stat3 axis represents an essential effector of activated Rac for the regulation of key cellular functions.

Activated Rac1 requires gp130 for Stat3 activation, cell proliferation and migration

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Arulanandam, Rozanne; Geletu, Mulu [Departments of Microbiology and Immunology and Pathology and Molecular Medicine, and Queen' s University Cancer Institute, Queen' s University, Botterell Hall, Rm. 713, Kingston, Ontario, Canada K7L 3N6 (Canada); Feracci, Helene [Universite Bordeaux 1, Centre de Recherche Paul Pascal, CNRS UPR 8641, 33600 Pessac (France); Raptis, Leda, E-mail: raptisl@queensu.ca [Departments of Microbiology and Immunology and Pathology and Molecular Medicine, and Queen' s University Cancer Institute, Queen' s University, Botterell Hall, Rm. 713, Kingston, Ontario, Canada K7L 3N6 (Canada)

2010-03-10

Rac1 (Rac) is a member of the Rho family of small GTPases which controls cell migration by regulating the organization of actin filaments. Previous results suggested that mutationally activated forms of the Rho GTPases can activate the Signal Transducer and Activator of Transcription-3 (Stat3), but the exact mechanism is a matter of controversy. We recently demonstrated that Stat3 activity of cultured cells increases dramatically following E-cadherin engagement. To better understand this pathway, we now compared Stat3 activity levels in mouse HC11 cells before and after expression of the mutationally activated Rac1 (Rac{sup V12}), at different cell densities. The results revealed for the first time a dramatic increase in protein levels and activity of both the endogenous Rac and Rac{sup V12} with cell density, which was due to inhibition of proteasomal degradation. In addition, Rac{sup V12}-expressing cells had higher Stat3, tyrosine-705 phosphorylation and activity levels at all densities, indicating that Rac{sup V12} is able to activate Stat3. Further examination of the mechanism of Stat3 activation showed that Rac{sup V12} expression caused a surge in mRNA of Interleukin-6 (IL6) family cytokines, known potent Stat3 activators. Knockdown of gp130, the common subunit of this family reduced Stat3 activity, indicating that these cytokines may be responsible for the Stat3 activation by Rac{sup V12}. The upregulation of IL6 family cytokines was required for cell migration and proliferation induced by Rac{sup V12}, as shown by gp130 knockdown experiments, thus demonstrating that the gp130/Stat3 axis represents an essential effector of activated Rac for the regulation of key cellular functions.

Deficiency of PTP1B Attenuates Hypothalamic Inflammation via Activation of the JAK2-STAT3 Pathway in Microglia.

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Tsunekawa, Taku; Banno, Ryoichi; Mizoguchi, Akira; Sugiyama, Mariko; Tominaga, Takashi; Onoue, Takeshi; Hagiwara, Daisuke; Ito, Yoshihiro; Iwama, Shintaro; Goto, Motomitsu; Suga, Hidetaka; Sugimura, Yoshihisa; Arima, Hiroshi

2017-02-01

Protein tyrosine phosphatase 1B (PTP1B) regulates leptin signaling in hypothalamic neurons via the JAK2-STAT3 pathway. PTP1B has also been implicated in the regulation of inflammation in the periphery. However, the role of PTP1B in hypothalamic inflammation, which is induced by a high-fat diet (HFD), remains to be elucidated. Here, we showed that STAT3 phosphorylation (p-STAT3) was increased in microglia in the hypothalamic arcuate nucleus of PTP1B knock-out mice (KO) on a HFD, accompanied by decreased Tnf and increased Il10 mRNA expression in the hypothalamus compared to wild-type mice (WT). In hypothalamic organotypic cultures, incubation with TNFα led to increased p-STAT3, accompanied by decreased Tnf and increased Il10 mRNA expression, in KO compared to WT. Incubation with p-STAT3 inhibitors or microglial depletion eliminated the differences in inflammation between genotypes. These data indicate an important role of JAK2-STAT3 signaling negatively regulated by PTP1B in microglia, which attenuates hypothalamic inflammation under HFD conditions. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Deficiency of PTP1B Attenuates Hypothalamic Inflammation via Activation of the JAK2-STAT3 Pathway in Microglia

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Taku Tsunekawa

2017-02-01

Full Text Available Protein tyrosine phosphatase 1B (PTP1B regulates leptin signaling in hypothalamic neurons via the JAK2-STAT3 pathway. PTP1B has also been implicated in the regulation of inflammation in the periphery. However, the role of PTP1B in hypothalamic inflammation, which is induced by a high-fat diet (HFD, remains to be elucidated. Here, we showed that STAT3 phosphorylation (p-STAT3 was increased in microglia in the hypothalamic arcuate nucleus of PTP1B knock-out mice (KO on a HFD, accompanied by decreased Tnf and increased Il10 mRNA expression in the hypothalamus compared to wild-type mice (WT. In hypothalamic organotypic cultures, incubation with TNFα led to increased p-STAT3, accompanied by decreased Tnf and increased Il10 mRNA expression, in KO compared to WT. Incubation with p-STAT3 inhibitors or microglial depletion eliminated the differences in inflammation between genotypes. These data indicate an important role of JAK2-STAT3 signaling negatively regulated by PTP1B in microglia, which attenuates hypothalamic inflammation under HFD conditions.

TC-PTP and PTP1B: Regulating JAK-STAT signaling, controlling lymphoid malignancies.

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Pike, Kelly A; Tremblay, Michel L

2016-06-01

Lymphoid malignancies are characterized by an accumulation of genetic lesions that act co-operatively to perturb signaling pathways and alter gene expression programs. The Janus kinases (JAK)-signal transducers and activators of transcription (STATs) pathway is one such pathway that is frequently mutated in leukemia and lymphoma. In response to cytokines and growth factors, a cascade of reversible tyrosine phosphorylation events propagates the JAK-STAT pathway from the cell surface to the nucleus. Activated STAT family members then play a fundamental role in establishing the transcriptional landscape of the cell. In leukemia and lymphoma, somatic mutations have been identified in JAK and STAT family members, as well as, negative regulators of the pathway. Most recently, inactivating mutations in the protein tyrosine phosphatase (PTP) genes PTPN1 (PTP1B) and PTPN2 (TC-PTP) were sequenced in B cell lymphoma and T cell acute lymphoblastic leukemia (T-ALL) respectively. The loss of PTP1B and TC-PTP phosphatase activity is associated with an increase in cytokine sensitivity, elevated JAK-STAT signaling, and changes in gene expression. As inactivation mutations in PTPN1 and PTPN2 are restricted to distinct subsets of leukemia and lymphoma, a future challenge will be to identify in which cellular contexts do they contributing to the initiation or maintenance of leukemogenesis or lymphomagenesis. As well, the molecular mechanisms by which PTP1B and TC-PTP loss co-operates with other genetic aberrations will need to be elucidated to design more effective therapeutic strategies. Copyright © 2016 Elsevier Ltd. All rights reserved.

Oleoylethanolamide exerts anti-inflammatory effects on LPS-induced THP-1 cells by enhancing PPARα signaling and inhibiting the NF-κB and ERK1/2/AP-1/STAT3 pathways.

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Yang, Lichao; Guo, Han; Li, Ying; Meng, Xianglan; Yan, Lu; Dan Zhang; Wu, Sangang; Zhou, Hao; Peng, Lu; Xie, Qiang; Jin, Xin

2016-10-10

The present study aimed to examine the anti-inflammatory actions of oleoylethanolamide (OEA) in lipopolysaccharide (LPS)-induced THP-1 cells. The cells were stimulated with LPS (1 μg/ml) in the presence or absence of OEA (10, 20 and 40 μM). The pro-inflammatory cytokines were evaluated by qRT-PCR and ELISA. The THP-1 cells were transiently transfected with PPARα small-interfering RNA, and TLR4 activity was determined with a blocking test using anti-TLR4 antibody. Additionally, a special inhibitor was used to analyse the intracellular signaling pathway. OEA exerted a potent anti-inflammatory effect by reducing the production of pro-inflammatory cytokines and TLR4 expression, and by enhancing PPARα expression. The modulatory effects of OEA on LPS-induced inflammation depended on PPARα and TLR4. Importantly, OEA inhibited LPS-induced NF-κB activation, IκBα degradation, expression of AP-1, and the phosphorylation of ERK1/2 and STAT3. In summary, our results demonstrated that OEA exerts anti-inflammatory effects by enhancing PPARα signaling, inhibiting the TLR4-mediated NF-κB signaling pathway, and interfering with the ERK1/2-dependent signaling cascade (TLR4/ERK1/2/AP-1/STAT3), which suggests that OEA may be a therapeutic agent for inflammatory diseases.

Mangiferin ameliorates Porphyromonas gingivalis-induced experimental periodontitis by inhibiting phosphorylation of nuclear factor-κB and Janus kinase 1-signal transducer and activator of transcription signaling pathways.

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Li, H; Wang, Q; Ding, Y; Bao, C; Li, W

2017-02-01

Mangiferin is a natural polyphenol compound with anti-inflammatory properties. However, there have been few reports on the effect of mangiferin on periodontitis. Here, we investigated the anti-inflammatory effects of this compound on experimental periodontitis and the underlying mechanisms. Mice were inoculated with Porphyromonas gingivalis to induce periodontitis, and treated with mangiferin orally (50 mg/kg bodyweight, once a day) for 8 wk. Then, the alveolar bone loss was examined using a scanning electronic microscope. Expression of tumor necrosis factor-α (TNF-α) and the phosphorylation levels of nuclear factor-κB (NF-κB) and Janus kinase 1-signal transducer and activator of adhesion (JAK1-STAT) pathways in the gingival epithelium were detected using western blot analysis and immunohistochemical staining. The results showed that mice with periodontitis exhibited greater alveolar bone loss, stronger expression of TNF-α and higher phosphorylation levels of NF-κB and JAK1-STAT1/3 pathways in gingival epithelia, compared with control mice with no periodontitis. Moreover, treatment with mangiferin could significantly inhibit alveolar bone loss, TNF-α production and phosphorylation of NF-κB and JAK1-STAT1/3 pathways in gingival epithelia. Mangiferin has anti-inflammatory effects on periodontitis, which is associated with its ability to down-regulate the phosphorylation of NF-κB and JAK1-STAT1/3 pathways in gingival epithelia. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Inhibition of interleukin-3- and interferon- α-induced JAK/STAT signaling by the synthetic α-X-2',3,4,4'-tetramethoxychalcones α-Br-TMC and α-CF3-TMC.

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Jobst, Belinda; Weigl, Julia; Michl, Carina; Vivarelli, Fabio; Pinz, Sophia; Amslinger, Sabine; Rascle, Anne

2016-11-01

The JAK/STAT pathway is an essential mediator of cytokine signaling, often upregulated in human diseases and therefore recognized as a relevant therapeutic target. We previously identified the synthetic chalcone α-bromo-2',3,4,4'-tetramethoxychalcone (α-Br-TMC) as a novel JAK2/STAT5 inhibitor. We also found that treatment with α-Br-TMC resulted in a downward shift of STAT5 proteins in SDS-PAGE, suggesting a post-translational modification that might affect STAT5 function. In the present study, we show that a single cysteine within STAT5 is responsible for the α-Br-TMC-induced protein shift, and that this modification does not alter STAT5 transcriptional activity. We also compared the inhibitory activity of α-Br-TMC to that of another synthetic chalcone, α-trifluoromethyl-2',3,4,4'-tetramethoxychalcone (α-CF3-TMC). We found that, like α-Br-TMC, α-CF3-TMC inhibits JAK2 and STAT5 phosphorylation in response to interleukin-3, however without altering STAT5 mobility in SDS-PAGE. Moreover, we demonstrate that both α-Br-TMC and α-CF3-TMC inhibit interferon-α-induced activation of STAT1 and STAT2, by inhibiting their phosphorylation and the expression of downstream interferon-stimulated genes. Together with the previous finding that α-Br-TMC and α-CF3-TMC inhibit the response to inflammation by inducing Nrf2 and blocking NF-κB activities, our data suggest that synthetic chalcones might be useful as anti-inflammatory, anti-cancer and immunomodulatory agents in the treatment of human diseases.

[Knockdown of STAT3 inhibits proliferation and migration of HepG2 hepatoma cells induced by IFN1].

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Li, Xiaofang; Wang, Yuqi; Yan, Ben; Fang, Peipei; Ma, Chao; Xu, Ning; Fu, Xiaoyan; Liang, Shujuan

2018-02-01

Objective To prepare lentiviruses expressing shRNA sequences targeting human signal transducer and activator of transcription 3 (STAT3) and detect the effect of STAT3 knockdown on type I interferon (IFN1)-induced proliferation and migration in HepG2 cells. Methods Four STAT3-targeting shRNA sequences (shRNA1-shRNA4) and one control sequence (Ctrl shRNA) were selected and cloned respectively into pLKO.1-sp6-pgk-GFP to construct shRNA-expressing vectors. Along with backbone psPAX2 and pMD2.G vectors, they were separately transfected into HEK293T cells to prepare lentiviruses. HepG2 cells were infected with the lentiviruses. Cytoplastic STAT3 level was detected by Western blotting to screen effective shRNA sequence(s) targeting STAT3. Proliferation and migration of HepG2 cells were analyzed by CCK-8 assay and Transwell TM migration and scratching assay, respectively. To detect the effect of IFN1 on cell proliferation and migration of HepG2 cells, the cells were treated with 2000 U/mL IFNα2b for indicated time and the activation of IFN-triggered STAT1 signal transduction was assayed by Western blotting. Results Two most effective STAT3-targeting shRNA sequences shRNA1 and shRNA2 were selected, and the expression of both STAT3 shRNA significantly decreased proliferation and migration of HepG2 cells. When treated with IFNα2b, 2000 U/mL of IFN1 showed more competent in attenuating growth and migration of HepG2 cells. Our data further proved that knockdown of STAT3 increased the phosphorylation of STAT1, and IFNα2b further enhanced the activation of STAT1 signaling in HepG2 cells. Conclusion Knockdown of STAT3 inhibits cell migration and growth, and rescues IFN response through up-regulating STAT1 signal transduction in HepG2 hepatoma cells.

STAT3 activation in monocytes accelerates liver cancer progression

International Nuclear Information System (INIS)

Wu, Wen-Yong; Li, Jun; Wu, Zheng-Sheng; Zhang, Chang-Le; Meng, Xiang-Ling

2011-01-01

Signal transducer and activator of transcription 3 (STAT3) is an important transcription factor ubiquitously expressed in different cell types. STAT3 plays an essential role in cell survival, proliferation, and differentiation. Aberrantly hyper-activated STAT3 signaling in cancer cells and in the tumor microenvironment has been detected in a wide variety of human cancers and is considered an important factor for cancer initiation, development, and progression. However, the role of STAT3 activation in monocytes in the development of HCC has not been well understood. Immunohistochemical analysis of phosphorylated STAT3 was performed on tissue microarray from HCC patients. Using a co-culture system in vivo, HCC cell growth was determined by the MTT assay. In vivo experiments were conducted with mice given diethylinitrosamine (DEN), which induces HCC was used to investigate the role of STAT3 expression in monocytes on tumor growth. Real-time PCR was used to determine the expression of cell proliferation and cell arrest associated genes in the tumor and nontumor tissue from liver. Phosphorylated STAT3 was found in human hepatocellular carcinoma tissue samples and was expressed in tumor cells and also in monocytes. Phosphorylated STAT3 expression in monocyte was significantly correlated to advanced clinical stage of HCC and a poor prognosis. Using a co-culture system in vivo, monocytes promoted HCC cell growth via the IL-6/STAT3 signaling pathway. The STAT3 inhibitor, NSC 74859, significantly suppressed tumor growth in vivo in mice with diethylinitrosamine (DEN)-induced HCC. In this animal model, blockade of STAT3 with NSC 74859 induced tumor cell apoptosis, while inhibiting both tumor cells and monocytes proliferation. Furthermore, NSC 74859 treatment suppressed cancer associated inflammation in DEN-induce HCC. Our data suggest constitutively activated STAT3 monocytes promote liver tumorigenesis in clinical patients and animal experiments. Thus, STAT3 in tumor

APPL1-mediated activation of STAT3 contributes to inhibitory effect of adiponectin on hepatic gluconeogenesis.

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Ding, Youming; Zhang, Deling; Wang, Bin; Zhang, Yemin; Wang, Lei; Chen, Xiaoyan; Li, Mingxin; Tang, Zhao; Wang, Changhua

2016-09-15

Adiponectin has been shown to suppress hepatic gluconeogenesis. However, the signaling pathways underlying its action remain ill-defined. The purpose of this study was to examine the potential role of APPL1 in mediating anti-gluconeogenic ability of adiponectin. Primary hepatocytes were isolated from male C57BL/6 mice. Western blot and RT-PCR were performed to detect protein expression and mRNA level, respectively. The protein-protein association was determined by immunoprecipitation and GST pull-down assay. We found that APPL1 protein levels were negatively associated with expressions of proteins and mRNAs of gluconeogenesis enzymes under stimulation with adiponectin. In addition, adiponectin-stimulated STAT3 phosphorylation and acetylation were positively regulated by APPL1 and negative regulated by SirT1. Pharmacological and genetic inhibition of STAT3 mitigated impact of adiponectin on hepatic gluconeogenesis. Furthermore, adiponectin administration facilitated the binding of APPL1 to SirT1 and suppressed the association of SirT1 with STAT3. Taken together, our study showed that APPL1-SirT1-STAT3 pathway mediated adiponectin signaling in primary hepatocytes. This new finding provides a novel mechanism by which adiponectin suppresses hepatic gluconeogenesis. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Antitumorigenic potential of STAT3 alternative splicing modulation.

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Zammarchi, Francesca; de Stanchina, Elisa; Bournazou, Eirini; Supakorndej, Teerawit; Martires, Kathryn; Riedel, Elyn; Corben, Adriana D; Bromberg, Jacqueline F; Cartegni, Luca

2011-10-25

Signal transducer and activator of transcription 3 (STAT3) plays a central role in the activation of multiple oncogenic pathways. Splicing variant STAT3β uses an alternative acceptor site within exon 23 that leads to a truncated isoform lacking the C-terminal transactivation domain. Depending on the context, STAT3β can act as a dominant-negative regulator of transcription and promote apoptosis. We show that modified antisense oligonucleotides targeted to a splicing enhancer that regulates STAT3 exon 23 alternative splicing specifically promote a shift of expression from STAT3α to STAT3β. Induction of endogenous STAT3β leads to apoptosis and cell-cycle arrest in cell lines with persistent STAT3 tyrosine phosphorylation compared with total STAT3 knockdown obtained by forced splicing-dependent nonsense-mediated decay (FSD-NMD). Comparison of the molecular effects of splicing redirection to STAT3 knockdown reveals a unique STAT3β signature, with a down-regulation of specific targets (including lens epithelium-derived growth factor, p300/CBP-associated factor, CyclinC, peroxisomal biogenesis factor 1, and STAT1β) distinct from canonical STAT3 targets typically associated with total STAT3 knockdown. Furthermore, similar in vivo redirection of STAT3 alternative splicing leads to tumor regression in a xenograft cancer model, demonstrating how pharmacological manipulation of a single key splicing event can manifest powerful antitumorigenic properties and validating endogenous splicing reprogramming as an effective cancer therapeutic approach.

The regulation effect of STAT 5 signaling pathway on the cell cycle progression of irradiated KG-1 cells

International Nuclear Information System (INIS)

Guo Dehuang; Dong Bo; Luo Qingliang; Wen Gengyun; Mao Bingzhi

2000-01-01

The author investigated the role of the JAK/STAT signaling pathway regulating cell cycle progression in the irradiated KG-1 cells. By permanent transfecting the cells with DN-STAT 5 cDNA to block the JAK/STAT signaling pathway and then transient transfecting with cyclin D 1 or cyclin B 1 cDNA, the effects of cyclin D 1 protein and cyclin B 1 protein on the cell cycle progression were examined. Results showed that after irradiation with 8Gy 60 Co rays, the irradiated KG-1 cells transfected with only DN-STAT 5 cDNA can not recover form the G 1 arrest, even though GM-CSF was added. Meanwhile, the cells transfected with both the DN-STAT 5 cDNA and cyclin D 1 cDNA or cyclin B 1 cDNA can recover from the G 1 arrest or the G 2 arrest to a great extent. Thus, it was proved indirectly that the JAK/STAT signaling pathway activated by GM-CSF regulated the cell cycle progression through cyclin D 1 and cyclin B 1 protein

Tumor-associated macrophages in oral premalignant lesions coexpress CD163 and STAT1 in a Th1-dominated microenvironment

International Nuclear Information System (INIS)

Mori, Kazumasa; Haraguchi, Shigeki; Hiori, Miki; Shimada, Jun; Ohmori, Yoshihiro

2015-01-01

Tumor-associated macrophages (TAMs) are implicated in the growth, invasion and metastasis of various solid tumors. However, the phenotype of TAMs in premalignant lesions of solid tumors has not been clarified. In the present study, we identify the phenotype of TAMs in leukoplakia, an oral premalignant lesion, by immunohistochemical analysis and investigate the involvement of infiltrated T cells that participate in the polarization of TAMs. The subjects included 30 patients with oral leukoplakia and 10 individuals with normal mucosa. Hematoxylin and eosin slides were examined for the histological grades, and immunohistochemical analysis was carried out using antibodies against CD68 (pan-MΦ), CD80 (M1 MΦ), CD163 (M2 MΦ), CD4 (helper T cells: Th), CD8 (cytotoxic T cells), CXCR3, CCR5 (Th1), CCR4 (Th2), signal transducer and activator of transcription (STAT1), phosphorylated STAT1 (pSTAT1) and chemokine CXCL9. The differences in the numbers of positively stained cells among the different histological grades were tested for statistical significance using the Kruskal-Wallis test. Correlations between different types of immune cells were determined using Spearman’s rank analysis. An increase in the rate of CD163 + TAM infiltration was observed in mild and moderate epithelial dysplasia, which positively correlated with the rate of intraepithelial CD4 + Th cell infiltration. Although CCR4 + cells rarely infiltrated, CXCR3 + and CCR5 + cells were observed in these lesions. Cells positive for STAT1 and chemokine CXCL9, interferon- (IFN)-induced gene products, and pSTAT1 were also observed in the same lesions. Double immunofluorescence staining demonstrated that the cells that were positive for CD163 were also positive for STAT1. CD163 + TAMs in oral premalignant lesions coexpress CD163 and STAT1, suggesting that the TAMs in oral premalignant lesions possess an M1 phenotype in a Th1-dominated micromilieu

Scoparone exerts anti-tumor activity against DU145 prostate cancer cells via inhibition of STAT3 activity.

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Jeong-Kook Kim

Full Text Available Scoparone, a natural compound isolated from Artemisia capillaris, has been used in Chinese herbal medicine to treat neonatal jaundice. Signal transducer and activator of transcription 3 (STAT3 contributes to the growth and survival of many human tumors. This study was undertaken to investigate the anti-tumor activity of scoparone against DU145 prostate cancer cells and to determine whether its effects are mediated by inhibition of STAT3 activity. Scoparone inhibited proliferation of DU145 cells via cell cycle arrest in G1 phase. Transient transfection assays showed that scoparone repressed both constitutive and IL-6-induced transcriptional activity of STAT3. Western blot and quantitative real-time PCR analyses demonstrated that scoparone suppressed the transcription of STAT3 target genes such as cyclin D1, c-Myc, survivin, Bcl-2, and Socs3. Consistent with this, scoparone decreased phosphorylation and nuclear accumulation of STAT3, but did not reduce phosphorylation of janus kinase 2 (JAK2 or Src, the major upstream kinases responsible for STAT3 activation. Moreover, transcriptional activity of a constitutively active mutant of STAT3 (STAT3C was inhibited by scoparone, but not by AG490, a JAK2 inhibitor. Furthermore, scoparone treatment suppressed anchorage-independent growth in soft agar and tumor growth of DU145 xenografts in nude mice, concomitant with a reduction in STAT3 phosphorylation. Computational modeling suggested that scoparone might bind the SH2 domain of STAT3. Our findings suggest that scoparone elicits an anti-tumor effect against DU145 prostate cancer cells in part through inhibition of STAT3 activity.

Human airway eosinophils exhibit preferential reduction in STAT signaling capacity and increased CISH expression.

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Burnham, Mandy E; Koziol-White, Cynthia J; Esnault, Stephane; Bates, Mary E; Evans, Michael D; Bertics, Paul J; Denlinger, Loren C

2013-09-15

Allergic asthma, a chronic respiratory disorder marked by inflammation and recurrent airflow obstruction, is associated with elevated levels of IL-5 family cytokines and elevated numbers of eosinophils (EOS). IL-5 family cytokines elongate peripheral blood EOS (EOS(PB)) viability, recruit EOS(PB) to the airways, and, at higher concentrations, induce degranulation and reactive oxygen species generation. Although airway EOS (EOS(A)) remain signal ready in that GM-CSF treatment induces degranulation, treatment of EOS(A) with IL-5 family cytokines no longer confers a survival advantage. Because the IL-5 family receptors have common signaling capacity, but are uncoupled from EOS(A) survival, whereas other IL-5 family induced endpoints remain functional, we tested the hypothesis that EOS(A) possess a JAK/STAT-specific regulatory mechanism (because JAK/STAT signaling is critical to EOS survival). We found that IL-5 family-induced STAT3 and STAT5 phosphorylation is attenuated in EOS(A) relative to blood EOS from airway allergen-challenged donors. However, IL-5 family-induced ERK1/2 phosphorylation is not altered between EOS(A) and EOS from airway allergen-challenged donors. These observations suggest EOS(A) possess a regulatory mechanism for suppressing STAT signaling distinct from ERK1/2 activation. Furthermore, we found, in EOS(PB), IL-5 family cytokines induce members of the suppressors of cytokine signaling (SOCS) genes, CISH and SOCS1. Additionally, following allergen challenge, EOS(A) express significantly more CISH and SOCS1 mRNA and CISH protein than EOS(PB) counterparts. In EOS(PB), long-term pretreatment with IL-5 family cytokines, to varying degrees, attenuates IL-5 family-induced STAT5 phosphorylation. These data support a model in which IL-5 family cytokines trigger a selective downregulation mechanism in EOS(A) for JAK/STAT pathways.

Mutation of the SHP-2 binding site in growth hormone (GH) receptor prolongs GH-promoted tyrosyl phosphorylation of GH receptor, JAK2, and STAT5B

DEFF Research Database (Denmark)

Stofega, M R; Herrington, J; Billestrup, Nils

2000-01-01

phosphorylation. Consistent with the effects on STAT5B phosphorylation, tyrosine-to-phenylalanine mutation of tyrosine 595 prolongs the duration of tyrosyl phosphorylation of GHR and JAK2. These data suggest that tyrosine 595 is a major site of interaction of GHR with SHP-2, and that GHR-bound SHP-2 negatively......Binding of GH to GH receptor (GHR) rapidly and transiently activates multiple signal transduction pathways that contribute to the growth-promoting and metabolic effects of GH. While the events that initiate GH signal transduction, such as activation of the Janus tyrosine kinase JAK2, are beginning...

Tet1 is required for Rb phosphorylation during G1/S phase transition

International Nuclear Information System (INIS)

Huang, Shengsong; Zhu, Ziqi; Wang, Yiqin; Wang, Yanru; Xu, Longxia; Chen, Xuemei; Xu, Qing; Zhang, Qimin; Zhao, Xin; Yu, Yi; Wu, Denglong

2013-01-01

Highlights: •Tet1 was required for NIT3T3 proliferation. •Tet1 depletion inhibited G1-S entry. •Cyclin D1 accumulation and Rb phosphorylation was blocked by Tet1 knockdown. -- Abstract: DNA methylation plays an important role in many biological processes, including regulation of gene expression, maintenance of chromatin conformation and genomic stability. TET-family proteins convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), which indicates that these enzymes may participate in DNA demethylation. The function of TET1 has not yet been well characterized in somatic cells. Here, we show that depletion of Tet1 in NIH3T3 cells inhibits cell growth. Furthermore, Tet1 knockdown blocks cyclin D1 accumulation in G1 phase, inhibits Rb phosphorylation and consequently delays entrance to G1/S phase. Taken together, this study demonstrates that Tet1 is required for cell proliferation and that this process is mediated through the Rb pathway

Stat1-Vitamin D Receptor Interactions Antagonize 1,25-Dihydroxyvitamin D Transcriptional Activity and Enhance Stat1-Mediated Transcription

Science.gov (United States)

Vidal, Marcos; Ramana, Chilakamarti V.; Dusso, Adriana S.

2002-01-01

The cytokine gamma interferon (IFN-γ) and the calcitropic steroid hormone 1,25-dihydroxyvitamin D (1,25D) are activators of macrophage immune function. In sarcoidosis, tuberculosis, and several granulomatoses, IFN-γ induces 1,25D synthesis by macrophages and inhibits 1,25D induction of 24-hydroxylase, a key enzyme in 1,25D inactivation, causing high levels of 1,25D in serum and hypercalcemia. This study delineates IFN-γ-1,25D cross talk in human monocytes-macrophages. Nuclear accumulation of Stat1 and vitamin D receptor (VDR) by IFN-γ and 1,25D promotes protein-protein interactions between Stat1 and the DNA binding domain of the VDR. This prevents VDR-retinoid X receptor (RXR) binding to the vitamin D-responsive element, thus diverting the VDR from its normal genomic target on the 24-hydroxylase promoter and antagonizing 1,25D-VDR transactivation of this gene. In contrast, 1,25D enhances IFN-γ action. Stat1-VDR interactions, by preventing Stat1 deactivation by tyrosine dephosphorylation, cooperate with IFN-γ/Stat1-induced transcription. This novel 1,25D-IFN-γ cross talk explains the pathogenesis of abnormal 1,25D homeostasis in granulomatous processes and provides new insights into 1,25D immunomodulatory properties. PMID:11909970

A conserved motif in the linker domain of STAT1 transcription factor is required for both recognition and release from high-affinity DNA-binding sites.

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Hüntelmann, Bettina; Staab, Julia; Herrmann-Lingen, Christoph; Meyer, Thomas

2014-01-01

Binding to specific palindromic sequences termed gamma-activated sites (GAS) is a hallmark of gene activation by members of the STAT (signal transducer and activator of transcription) family of cytokine-inducible transcription factors. However, the precise molecular mechanisms involved in the signal-dependent finding of target genes by STAT dimers have not yet been very well studied. In this study, we have characterized a sequence motif in the STAT1 linker domain which is highly conserved among the seven human STAT proteins and includes surface-exposed residues in close proximity to the bound DNA. Using site-directed mutagenesis, we have demonstrated that a lysine residue in position 567 of the full-length molecule is required for GAS recognition. The substitution of alanine for this residue completely abolished both binding to high-affinity GAS elements and transcriptional activation of endogenous target genes in cells stimulated with interferon-γ (IFNγ), while the time course of transient nuclear accumulation and tyrosine phosphorylation were virtually unchanged. In contrast, two glutamic acid residues (E559 and E563) on each monomer are important for the dissociation of dimeric STAT1 from DNA and, when mutated to alanine, result in elevated levels of tyrosine-phosphorylated STAT1 as well as prolonged IFNγ-stimulated nuclear accumulation. In conclusion, our data indicate that the kinetics of signal-dependent GAS binding is determined by an array of glutamic acid residues located at the interior surface of the STAT1 dimer. These negatively charged residues appear to align the long axis of the STAT1 dimer in a position perpendicular to the DNA, thereby facilitating the interaction between lysine 567 and the phosphodiester backbone of a bound GAS element, which is a prerequisite for transient gene induction.

KAP1 regulates type I interferon/STAT1-mediated IRF-1 gene expression

International Nuclear Information System (INIS)

Kamitani, Shinya; Ohbayashi, Norihiko; Ikeda, Osamu; Togi, Sumihito; Muromoto, Ryuta; Sekine, Yuichi; Ohta, Kazuhide; Ishiyama, Hironobu; Matsuda, Tadashi

2008-01-01

Signal transducers and activators of transcription (STATs) mediate cell proliferation, differentiation, and survival in immune responses, hematopoiesis, neurogenesis, and other biological processes. Recently, we showed that KAP1 is a novel STAT-binding partner that regulates STAT3-mediated transactivation. KAP1 is a universal co-repressor protein for the KRAB zinc finger protein superfamily of transcriptional repressors. In this study, we found KAP1-dependent repression of interferon (IFN)/STAT1-mediated signaling. We also demonstrated that endogenous KAP1 associates with endogenous STAT1 in vivo. Importantly, a small-interfering RNA-mediated reduction in KAP1 expression enhanced IFN-induced STAT1-dependent IRF-1 gene expression. These results indicate that KAP1 may act as an endogenous regulator of the IFN/STAT1 signaling pathway

Identification of STAT1 and STAT3 specific inhibitors using comparative virtual screening and docking validation.

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Malgorzata Szelag

Full Text Available Signal transducers and activators of transcription (STATs facilitate action of cytokines, growth factors and pathogens. STAT activation is mediated by a highly conserved SH2 domain, which interacts with phosphotyrosine motifs for specific STAT-receptor contacts and STAT dimerization. The active dimers induce gene transcription in the nucleus by binding to a specific DNA-response element in the promoter of target genes. Abnormal activation of STAT signaling pathways is implicated in many human diseases, like cancer, inflammation and auto-immunity. Searches for STAT-targeting compounds, exploring the phosphotyrosine (pTyr-SH2 interaction site, yielded many small molecules for STAT3 but sparsely for other STATs. However, many of these inhibitors seem not STAT3-specific, thereby questioning the present modeling and selection strategies of SH2 domain-based STAT inhibitors. We generated new 3D structure models for all human (hSTATs and developed a comparative in silico docking strategy to obtain further insight into STAT-SH2 cross-binding specificity of a selection of previously identified STAT3 inhibitors. Indeed, by primarily targeting the highly conserved pTyr-SH2 binding pocket the majority of these compounds exhibited similar binding affinity and tendency scores for all STATs. By comparative screening of a natural product library we provided initial proof for the possibility to identify STAT1 as well as STAT3-specific inhibitors, introducing the 'STAT-comparative binding affinity value' and 'ligand binding pose variation' as selection criteria. In silico screening of a multi-million clean leads (CL compound library for binding of all STATs, likewise identified potential specific inhibitors for STAT1 and STAT3 after docking validation. Based on comparative virtual screening and docking validation, we developed a novel STAT inhibitor screening tool that allows identification of specific STAT1 and STAT3 inhibitory compounds. This could increase our

Biologic activity of the novel small molecule STAT3 inhibitor LLL12 against canine osteosarcoma cell lines

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Couto Jason I

2012-12-01

Full Text Available Abstract Background STAT3 [1] has been shown to be dysregulated in nearly every major cancer, including osteosarcoma (OS. Constitutive activation of STAT3, via aberrant phosphorylation, leads to proliferation, cell survival and resistance to apoptosis. The present study sought to characterize the biologic activity of a novel allosteric STAT3 inhibitor, LLL12, in canine OS cell lines. Results We evaluated the effects of LLL12 treatment on 4 canine OS cell lines and found that LLL12 inhibited proliferation, induced apoptosis, reduced STAT3 phosphorylation, and decreased the expression of several transcriptional targets of STAT3 in these cells. Lastly, LLL12 exhibited synergistic anti-proliferative activity with the chemotherapeutic doxorubicin in the OS lines. Conclusion LLL12 exhibits biologic activity against canine OS cell lines through inhibition of STAT3 related cellular functions supporting its potential use as a novel therapy for OS.

Role of JAK-STAT pathway in reducing cardiomyocytes hypoxia/reoxygenation injury induced by S1P postconditioning.

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Wang, Yuqing; Wang, Dongfei; Zhang, Lizhi; Ye, Fangyu; Li, Mengmeng; Wen, Ke

2016-08-05

This experiment was designed to explore the protection of sphingosine1-phosphate (S1P) postconditioning on rat myocardial cells injured by hypoxia/reoxygenation acting via the Janus kinase-signal transducer and activator of transcription (JAK-STAT) signal pathway. The data showed that S1P could significantly increase cell viability, lower the rate of apoptosis, decrease the content of lactate dehydrogenase (LDH) and caspase3 activity in the culture medium, increase the activity of total superoxide dismutase (T-SOD) and manganese superoxide dismutase (Mn-SOD), reduce the loss of mitochondrial membrane potential and the fluorescence intensity of intracellular calcium, as well as increase the phosphorylation of JAK2 and STAT3 in comparison with the H/R group. When the JAK inhibitor AG490 or the STAT inhibitor stattic were added, the effects of S1P were inhibited. Our date shows that S1P protects H9c2 cells from hypoxia/reoxygenation injury and that the protection by S1P was inhibited by AG490 and stattic. Therefore S1P protects H9c2 cells against hypoxia/reoxygenation injury via the JAK-STAT pathway. Copyright © 2016 Elsevier B.V. All rights reserved.

Signal Transducer and Activator of Transcription 3 (STAT3) Mediates Amino Acid Inhibition of Insulin Signaling through Serine 727 Phosphorylation*

OpenAIRE

Kim, Jeong-Ho; Yoon, Mee-Sup; Chen, Jie

2009-01-01

Nutrient overload is associated with the development of obesity, insulin resistance, and type II diabetes. High plasma concentrations of amino acids have been found to correlate with insulin resistance. At the cellular level, excess amino acids impair insulin signaling, the mechanisms of which are not fully understood. Here, we report that STAT3 plays a key role in amino acid dampening of insulin signaling in hepatic cells. Excess amino acids inhibited insulin-stimulated Akt phosphorylation a...

Menin and RNF20 recruitment is associated with dynamic histone modifications that regulate signal transducer and activator of transcription 1 (STAT1-activated transcription of the interferon regulatory factor 1 gene (IRF1

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Buro Lauren J

2010-09-01

Full Text Available Abstract Background Signal transducer and activator of transcription (STAT activation of gene expression is both rapid and transient, and when properly executed it affects growth, differentiation, homeostasis and the immune response, but when dysregulated it contributes to human disease. Transcriptional activation is regulated by alterations to the chromatin template. However, the role of histone modification at gene loci that are activated for transcription in response to STAT signaling is poorly defined. Results Using chromatin immunoprecipitation, we profiled several histone modifications during STAT1 activation of the interferon regulatory factor 1 gene (IRF1. Methylated lysine histone proteins H3K4me2, H3K4me3, H3K79me3, H3K36me3 and monoubiquitinated histone ubH2B are dynamic and correlate with interferon (IFNγ induction of STAT1 activity. Chemical inhibition of H3K4 methylation downregulates IRF1 transcription and decreases RNA polymerase II (Pol II occupancy at the IRF1 promoter. MEN1, a component of a complex proteins associated with Set1 (COMPASS-like complex and the hBRE1 component, RNF20, are localized to IRF1 in the uninduced state and are further recruited when IRF1 is activated. RNAi-mediated depletion of RNF20 lowers both ubH2B and H3K4me3, but surprisingly, upregulates IFNγ induced IRF1 transcription. The dynamics of phosphorylation in the C-terminal domain (CTD of Pol II are disrupted during gene activation as well. Conclusions H2B monoubiquitination promotes H3K4 methylation, but the E3 ubiquitin ligase, RNF20, is repressive of inducible transcription at the IRF1 gene locus, suggesting that ubH2B can, directly or indirectly, affect Pol II CTD phosphorylation cycling to exert control on ongoing transcription.

Intracellular expression of IRF9 Stat fusion protein overcomes the defective Jak-Stat signaling and inhibits HCV RNA replication

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Balart Luis A

2010-10-01

Full Text Available Abstract Interferon alpha (IFN-α binds to a cell surface receptor that activates the Jak-Stat signaling pathway. A critical component of this pathway is the translocation of interferon stimulated gene factor 3 (a complex of three proteins Stat1, Stat2 and IRF9 to the nucleus to activate antiviral genes. A stable sub-genomic replicon cell line resistant to IFN-α was developed in which the nuclear translocation of Stat1 and Stat2 proteins was prevented due to the lack of phosphorylation; whereas the nuclear translocation of IRF9 protein was not affected. In this study, we sought to overcome defective Jak-Stat signaling and to induce an antiviral state in the IFN-α resistant replicon cell line by developing a chimera IRF9 protein fused with the trans activating domain (TAD of either a Stat1 (IRF9-S1C or Stat2 (IRF9-S2C protein. We show here that intracellular expression of fusion proteins using the plasmid constructs of either IRF9-S1C or IRF9-S2C, in the IFN-α resistant cells, resulted in an increase in Interferon Stimulated Response Element (ISRE luciferase promoter activity and significantly induced HLA-1 surface expression. Moreover, we show that transient transfection of IRF9-S1C or IRF9-S2C plasmid constructs into IFN-α resistant replicon cells containing sub-genomic HCV1b and HCV2a viruses resulted in an inhibition of viral replication and viral protein expression independent of IFN-α treatment. The results of this study indicate that the recombinant fusion proteins of IRF9-S1C, IRF9-S2C alone, or in combination, have potent antiviral properties against the HCV in an IFN-α resistant cell line with a defective Jak-Stat signaling.

Screening for MPL mutations in essential thrombocythemia and primary myelofibrosis: normal Mpl expression and absence of constitutive STAT3 and STAT5 activation in MPLW515L-positive platelets.

Science.gov (United States)

Glembotsky, Ana C; Korin, Laura; Lev, Paola R; Chazarreta, Carlos D; Marta, Rosana F; Molinas, Felisa C; Heller, Paula G

2010-05-01

To evaluate the frequency of MPL W515L, W515K and S505N mutations in essential thrombocythemia (ET) and primary myelofibrosis (PMF) and to determine whether MPLW515L leads to impaired Mpl expression, constitutive STAT3 and STAT5 activation and enhanced response to thrombopoietin (TPO). Mutation detection was performed by allele-specific PCR and sequencing. Platelet Mpl expression was evaluated by flow cytometry, immunoblotting and real-time RT-PCR. Activation of STAT3 and STAT5 before and after stimulation with increasing concentrations of TPO was studied by immunoblotting. Plasma TPO was measured by ELISA. MPLW515L was detected in 1 of 100 patients with ET and 1 of 11 with PMF. Platelets from the PMF patient showed 100% mutant allele, which was Mpl surface and total protein expression were normal, and TPO levels were mildly increased in the MPLW515L-positive ET patient, while MPL transcripts did not differ from controls in both MPLW515L-positive patients. Constitutive STAT3 and STAT5 phosphorylation was absent and dose response to TPO-induced phosphorylation was not enhanced. The low frequency of MPL mutations in this cohort is in agreement with previous studies. The finding of normal Mpl levels in MPLW515L-positive platelets indicates this mutation does not lead to dysregulated Mpl expression, as frequently shown for myeloproliferative neoplasms. The lack of spontaneous STAT3 and STAT5 activation and the normal response to TPO is unexpected as MPLW515L leads to constitutive receptor activation and hypersensitivity to TPO in experimental models.

Biologic consequences of Stat1-independent IFN signaling

Science.gov (United States)

Gil, M. Pilar; Bohn, Erwin; O'Guin, Andrew K.; Ramana, Chilakamarti V.; Levine, Beth; Stark, George R.; Virgin, Herbert W.; Schreiber, Robert D.

2001-01-01

Although Stat1 is required for many IFN-dependent responses, recent work has shown that IFNγ functions independently of Stat1 to affect the growth of tumor cells or immortalized fibroblasts. We now demonstrate that both IFNγ and IFNα/β regulate proliferative responses in cells of the mononuclear phagocyte lineage derived from Stat1-null mice. Using both representational difference analysis and gene arrays, we show that IFNγ exerts its Stat1-independent actions on mononuclear phagocytes by regulating the expression of many genes. This result was confirmed by monitoring changes in expression and function of the corresponding gene products. Regulation of the expression of these genes requires the IFNγ receptor and Jak1. The physiologic relevance of IFN-dependent, Stat1-independent signaling was demonstrated by monitoring antiviral responses in Stat1-null mice. Thus, the IFN receptors engage alternative Stat1-independent signaling pathways that have important physiological consequences. PMID:11390995

MicroRNA 17-5p regulates autophagy in Mycobacterium tuberculosis-infected macrophages by targeting Mcl-1 and STAT3.

Science.gov (United States)

Kumar, Ranjeet; Sahu, Sanjaya Kumar; Kumar, Manish; Jana, Kuladip; Gupta, Pushpa; Gupta, Umesh D; Kundu, Manikuntala; Basu, Joyoti

2016-05-01

Autophagy plays a crucial role in the control of bacterial burden during Mycobacterium tuberculosis infection. MicroRNAs (miRNAs) are small non-coding RNAs that regulate immune signalling and inflammation in response to challenge by pathogens. Appreciating the potential of host-directed therapies designed to control autophagy during mycobacterial infection, we focused on the role of miRNAs in regulating M. tuberculosis-induced autophagy in macrophages. Here, we demonstrate that M. tuberculosis infection leads to downregulation of miR-17 and concomitant upregulation of its targets Mcl-1 and STAT3, a transcriptional activator of Mcl-1. Forced expression of miR-17 reduces expression of Mcl-1 and STAT3 and also the interaction between Mcl-1 and Beclin-1. This is directly linked to enhanced autophagy, because Mcl-1 overexpression attenuates the effects of miR-17. At the same time, transfection with a kinase-inactive mutant of protein kinase C δ (PKCδ) (an activator of STAT3) augments M. tuberculosis-induced autophagy, and miR-17 overexpression diminishes phosphorylation of PKCδ, suggesting that an miR-17/PKC δ/STAT3 axis regulates autophagy during M. tuberculosis infection. © 2015 John Wiley & Sons Ltd.

A molecular model for the differential activation of STAT3 and STAT6 by the herpesviral oncoprotein tip.

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Eman Dey Mazumder

Full Text Available Constitutive STAT signaling provides growth promoting signals in many forms of malignancy. We performed molecular modeling and molecular dynamics studies of the interaction between the regulatory Src homology 2 (SH2 domains of STAT3 and 6 with phosphorylated peptides of the herpesviral oncoprotein Tip, which facilitates Src kinase mediated STAT-activation and T cell proliferation. The studies give insight into the ligand binding specificity of the STAT SH2 domains and provide the first model for the differential activation of STAT3 or STAT6 by two distinct regions of the viral Tip protein. The biological relevance of the modeled interactions was then confirmed by activation studies using corresponding recombinant oncoproteins, and finally by respective recombinant viruses. The functional data give experimental validation of the molecular dynamics study, and provide evidence for the involvement of STAT6 in the herpesvirus induced T cell proliferation.

Controlling nuclear JAKs and STATs for specific gene activation by IFNγ

International Nuclear Information System (INIS)

Noon-Song, Ezra N.; Ahmed, Chulbul M.; Dabelic, Rea; Canton, Johnathan; Johnson, Howard M.

2011-01-01

Highlights: → Gamma interferon (IFNγ) and its receptor subunit, IFNGR1, interact with the promoter region of IFNγ-associated genes along with transcription factor STAT1α. → We show that activated Janus kinases pJAK2 and pJAK1 also associate with IFNGR1 in the nucleus. → The activated Janus kinases are responsible for phosphorylation of tyrosine 41 on histone H3, an important epigenetic event for specific gene activation. -- Abstract: We previously showed that gamma interferon (IFNγ) and its receptor subunit, IFNGR1, interacted with the promoter region of IFNγ-activated genes along with transcription factor STAT1α. Recent studies have suggested that activated Janus kinases pJAK2 and pJAK1 also played a role in gene activation by phosphorylation of histone H3 on tyrosine 41. This study addresses the question of the role of activated JAKs in specific gene activation by IFNγ. We carried out chromatin immunoprecipitation (ChIP) followed by PCR in IFNγ treated WISH cells and showed association of pJAK1, pJAK2, IFNGR1, and STAT1 on the same DNA sequence of the IRF-1 gene promoter. The β-actin gene, which is not activated by IFNγ, did not show this association. The movement of activated JAK to the nucleus and the IRF-1 promoter was confirmed by the combination of nuclear fractionation, confocal microscopy and DNA precipitation analysis using the biotinylated GAS promoter. Activated JAKs in the nucleus was associated with phosphorylated tyrosine 41 on histone H3 in the region of the GAS promoter. Unphosphorylated JAK2 was found to be constitutively present in the nucleus and was capable of undergoing activation in IFNγ treated cells, most likely via nuclear IFNGR1. Association of pJAK2 and IFNGR1 with histone H3 in IFNγ treated cells was demonstrated by histone H3 immunoprecipitation. Unphosphorylated STAT1 protein was associated with histone H3 of untreated cells. IFNγ treatment resulted in its disassociation and then re-association as pSTAT1. The

Hes1 promotes the IL-22-mediated antimicrobial response by enhancing STAT3-dependent transcription in human intestinal epithelial cells

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Murano, Tatsuro [Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo (Japan); Okamoto, Ryuichi, E-mail: rokamoto.gast@tmd.ac.jp [Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo (Japan); Department of Advanced GI Therapeutics, Graduate School, Tokyo Medical and Dental University, Tokyo (Japan); Ito, Go; Nakata, Toru; Hibiya, Shuji; Shimizu, Hiromichi; Fujii, Satoru; Kano, Yoshihito; Mizutani, Tomohiro; Yui, Shiro; Akiyama-Morio, Junko; Nemoto, Yasuhiro [Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo (Japan); Tsuchiya, Kiichiro; Nakamura, Tetsuya [Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo (Japan); Department of Advanced GI Therapeutics, Graduate School, Tokyo Medical and Dental University, Tokyo (Japan); Watanabe, Mamoru [Department of Gastroenterology and Hepatology, Graduate School, Tokyo Medical and Dental University, Tokyo (Japan)

2014-01-17

Highlights: •Hes1 enhances IL-22-STAT3 signaling in human intestinal epithelial cells. •Hes1 enhances REG family gene induction by IL-22-STAT3 signaling. •Protein level of Hes1 restricts the response to IL-22. •Present regulation of a cytokine signal represents a new mode of Hes1 function. -- Abstract: Notch signaling plays an essential role in the proliferation and differentiation of intestinal epithelial cells (IECs). We have previously shown that Notch signaling is up-regulated in the inflamed mucosa of ulcerative colitis (UC) and thereby plays an indispensable role in tissue regeneration. Here we show that in addition to Notch signaling, STAT3 signaling is highly activated in the inflamed mucosa of UC. Forced expression of the Notch target gene Hes1 dramatically enhanced the IL-22-mediated STAT3-dependent transcription in human IECs. This enhancement of STAT3-dependent transcription was achieved by the extended phosphorylation of STAT3 by Hes1. Microarray analysis revealed that Hes1-mediated enhancement of IL-22-STAT3 signaling significantly increased the induction of genes encoding antimicrobial peptides, such as REG1A, REG3A and REG3G, in human IECs. Conversely, the reduction of Hes1 protein levels with a γ-secretase inhibitor significantly down-regulated the induction of those genes in IECs, resulting in a markedly poor response to IL-22. Our present findings identify a new role for the molecular function of Hes1 in which the protein can interact with cytokine signals and regulate the immune response of IECs.

Development of a STAT3 reporter prostate cancer cell line for high throughput screening of STAT3 activators and inhibitors

International Nuclear Information System (INIS)

Chau, My N.; Banerjee, Partha P.

2008-01-01

STAT3 is constitutively activated in several cancers, including prostate cancer, and is therefore, a potential target for cancer therapy. DU-145 prostate cancer cells were stably co-transfected with STAT3 reporter and puromycin resistant plasmids to create a stable STAT3 reporter cell line that can be used for high throughput screening of STAT3 modulators. The applicability of this cell line was tested with two known activators and inhibitors of STAT3. As expected, EGF and IL-6 increased STAT3 reporter activity and enhanced the nuclear localization of phosphorylated STAT3 (pSTAT3); whereas Cucurbitacin I and AG490 decreased STAT3 reporter activity dose and time-dependently and reduced the localization of pSTAT3 in the nuclei of prostate cancer cells. Given the importance of STAT3 in cancer initiation and progression, the development of a stable STAT3 reporter cell line in prostate cancer cells provides a rapid, sensitive, and cost effective method for the screening of potential STAT3 modulators.

Arctigenin enhances chemosensitivity of cancer cells to cisplatin through inhibition of the STAT3 signaling pathway.

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Yao, Xiangyang; Zhu, Fenfen; Zhao, Zhihui; Liu, Chang; Luo, Lan; Yin, Zhimin

2011-10-01

Arctigenin is a dibenzylbutyrolactone lignan isolated from Bardanae fructus, Arctium lappa L, Saussureamedusa, Torreya nucifera, and Ipomea cairica. It has been reported to exhibit anti-inflammatory activities, which is mainly mediated through its inhibitory effect on nuclear transcription factor-kappaB (NF-κB). But the role of arctigenin in JAK-STAT3 signaling pathways is still unclear. In present study, we investigated the effect of arctigenin on signal transducer and activator of transcription 3 (STAT3) pathway and evaluated whether suppression of STAT3 activity by arctigenin could sensitize cancer cells to a chemotherapeutic drug cisplatin. Our results show that arctigenin significantly suppressed both constitutively activated and IL-6-induced STAT3 phosphorylation and subsequent nuclear translocation in cancer cells. Inhibition of STAT3 tyrosine phosphorylation was found to be achieved through suppression of Src, JAK1, and JAK2, while suppression of STAT3 serine phosphorylation was mediated by inhibition of ERK activation. Pervanadate reversed the arctigenin-induced downregulation of STAT3 activation, suggesting the involvement of a protein tyrosine phosphatase. Indeed, arctigenin can obviously induce the expression of the PTP SHP-2. Furthermore, the constitutive activation level of STAT3 was found to be correlated to the resistance of cancer cells to cisplatin-induced apoptosis. Arctigenin dramatically promoted cisplatin-induced cell death in cancer cells, indicating that arctigenin enhanced the sensitivity of cancer cells to cisplatin mainly via STAT3 suppression. These observations suggest a novel anticancer function of arctigenin and a potential therapeutic strategy of using arctigenin in combination with chemotherapeutic agents for cancer treatment. Copyright © 2011 Wiley-Liss, Inc.

Biologic consequences of Stat1-independent IFN signaling

OpenAIRE

Gil, M. Pilar; Bohn, Erwin; O'Guin, Andrew K.; Ramana, Chilakamarti V.; Levine, Beth; Stark, George R.; Virgin, Herbert W.; Schreiber, Robert D.

2001-01-01

Although Stat1 is required for many IFN-dependent responses, recent work has shown that IFNγ functions independently of Stat1 to affect the growth of tumor cells or immortalized fibroblasts. We now demonstrate that both IFNγ and IFNα/β regulate proliferative responses in cells of the mononuclear phagocyte lineage derived from Stat1-null mice. Using both representational difference analysis and gene arrays, we show that IFNγ exerts its Stat1-independent actions on m...

Constitutive STAT3-activation in Sezary syndrome: tyrphostin AG490 inhibits STAT3-activation, interleukin-2 receptor expression and growth of leukemic Sezary cells

DEFF Research Database (Denmark)

Eriksen, K W; Kaltoft, K; Mikkelsen, G

2001-01-01

are IL-2Ralpha negative. An aberrant expression of IL-2Ralpha has recently been described in cutaneous T-cell lymphoma (CTCL). Here, we study the regulation of IL-2Ralpha expression and STATs in a tumor cell line obtained from peripheral blood from a patient with Sezary syndrome (SS), a leukemic variant...... of CTCL. We show that (1) STAT3 (a transcription factor known to regulate IL-2Ralpha transcription) is constitutively tyrosine-phosphorylated in SS tumor cells, but not in non-malignant T cells; (2) STAT3 binds constitutively to a STAT-binding sequence in the promotor of the IL-2Ralpha gene; (3) the Janus...... kinase inhibitor, tyrphostine AG490, inhibits STAT3 activation, STAT3 DNA binding, and IL-2Ralpha mRNA and protein expression in parallel; and (4) tyrphostine AG490 inhibits IL-2 driven mitogenesis and triggers apoptosis in SS tumor cells. In conclusion, we provide the first example of a constitutive...

Stat1 activation attenuates IL-6 induced Stat3 activity but does not alter apoptosis sensitivity in multiple myeloma

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Dimberg Lina Y

2012-07-01

Full Text Available Abstract Background Multiple myeloma (MM is at present an incurable malignancy, characterized by apoptosis-resistant tumor cells. Interferon (IFN treatment sensitizes MM cells to Fas-induced apoptosis and is associated with an increased activation of Signal transducer and activator of transcription (Stat1. The role of Stat1 in MM has not been elucidated, but Stat1 has in several studies been ascribed a pro-apoptotic role. Conversely, IL-6 induction of Stat3 is known to confer resistance to apoptosis in MM. Methods To delineate the role of Stat1 in IFN mediated sensitization to apoptosis, sub-lines of the U-266-1970 MM cell line with a stable expression of the active mutant Stat1C were utilized. The influence of Stat1C constitutive transcriptional activation on endogenous Stat3 expression and activation, and the expression of apoptosis-related genes were analyzed. To determine whether Stat1 alone would be an important determinant in sensitizing MM cells to apoptosis, the U-266-1970-Stat1C cell line and control cells were exposed to high throughput compound screening (HTS. Results To explore the role of Stat1 in IFN mediated apoptosis sensitization of MM, we established sublines of the MM cell line U-266-1970 constitutively expressing the active mutant Stat1C. We found that constitutive nuclear localization and transcriptional activity of Stat1 was associated with an attenuation of IL-6-induced Stat3 activation and up-regulation of mRNA for the pro-apoptotic Bcl-2 protein family genes Harakiri, the short form of Mcl-1 and Noxa. However, Stat1 activation alone was not sufficient to sensitize cells to Fas-induced apoptosis. In a screening of > 3000 compounds including bortezomib, dexamethasone, etoposide, suberoylanilide hydroxamic acid (SAHA, geldanamycin (17-AAG, doxorubicin and thalidomide, we found that the drug response and IC50 in cells constitutively expressing active Stat1 was mainly unaltered. Conclusion We conclude that Stat1 alters IL-6

Stat1 activation attenuates IL-6 induced Stat3 activity but does not alter apoptosis sensitivity in multiple myeloma

International Nuclear Information System (INIS)

Dimberg, Lina Y; Nilsson, Kenneth; Öberg, Fredrik; Wiklund, Helena Jernberg; Dimberg, Anna; Ivarsson, Karolina; Fryknäs, Mårten; Rickardson, Linda; Tobin, Gerard; Ekman, Simon; Larsson, Rolf; Gullberg, Urban

2012-01-01

Multiple myeloma (MM) is at present an incurable malignancy, characterized by apoptosis-resistant tumor cells. Interferon (IFN) treatment sensitizes MM cells to Fas-induced apoptosis and is associated with an increased activation of Signal transducer and activator of transcription (Stat)1. The role of Stat1 in MM has not been elucidated, but Stat1 has in several studies been ascribed a pro-apoptotic role. Conversely, IL-6 induction of Stat3 is known to confer resistance to apoptosis in MM. To delineate the role of Stat1 in IFN mediated sensitization to apoptosis, sub-lines of the U-266-1970 MM cell line with a stable expression of the active mutant Stat1C were utilized. The influence of Stat1C constitutive transcriptional activation on endogenous Stat3 expression and activation, and the expression of apoptosis-related genes were analyzed. To determine whether Stat1 alone would be an important determinant in sensitizing MM cells to apoptosis, the U-266-1970-Stat1C cell line and control cells were exposed to high throughput compound screening (HTS). To explore the role of Stat1 in IFN mediated apoptosis sensitization of MM, we established sublines of the MM cell line U-266-1970 constitutively expressing the active mutant Stat1C. We found that constitutive nuclear localization and transcriptional activity of Stat1 was associated with an attenuation of IL-6-induced Stat3 activation and up-regulation of mRNA for the pro-apoptotic Bcl-2 protein family genes Harakiri, the short form of Mcl-1 and Noxa. However, Stat1 activation alone was not sufficient to sensitize cells to Fas-induced apoptosis. In a screening of > 3000 compounds including bortezomib, dexamethasone, etoposide, suberoylanilide hydroxamic acid (SAHA), geldanamycin (17-AAG), doxorubicin and thalidomide, we found that the drug response and IC50 in cells constitutively expressing active Stat1 was mainly unaltered. We conclude that Stat1 alters IL-6 induced Stat3 activity and the expression of pro

Aqueous extract of Arbutus unedo inhibits STAT1 activation in human breast cancer cell line MDA-MB-231 and human fibroblasts through SHP2 activation.

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Mariotto, S; Ciampa, A R; de Prati, A Carcereri; Darra, E; Vincenzi, S; Sega, M; Cavalieri, E; Shoji, K; Suzuki, H

2008-05-01

Arbutus unedo L. has been for a long time employed in traditional and popular medicine as an astringent, diuretic, urinary anti-septic, and more recently, in the therapy of hypertension and diabetes. Signal transducer and activator of transcription 1 (STAT1) is a fascinating and complex protein with multiple yet contrasting transcriptional functions. Although activation of this nuclear factor is finely regulated in order to control the entire inflammatory process, its hyper-activation or time-spatially erroneous activation may lead to exacerbation of inflammation. The modulation of this nuclear factor, therefore, has recently been considered as a new strategy in the treatment of inflammatory diseases. In this study, we present data showing that the aqueous extract of Arbutus unedo's leaves exerts inhibitory action on interferon-gamma (IFN-gamma) elicited activation of STAT1, both in human breast cancer cell line MDA-MB-231 and in human fibroblasts. This down-regulation of STAT1 is shown to result from a reduced tyrosine phosphorylation of STAT1 protein. Evidence is also presented indicating that the inhibitory effect of this extract may be mediated through enhancement of tyrosine phosphorylation of SHP2 tyrosine phosphatase. The modulation of this nuclear factor turns out into the regulation of the expression of a number of genes involved in the inflammatory response such as inducible nitric oxide synthase (iNOS) and intercellular adhesion molecule-1 (ICAM-1). Taken together, our results suggest that the employment of the Arbutus unedo aqueous extract is promising, at least, as an auxiliary anti-inflammatory treatment of diseases in which STAT1 plays a critical role.

Sustained Submicromolar H2O2 Levels Induce Hepcidin via Signal Transducer and Activator of Transcription 3 (STAT3)*

Science.gov (United States)

Millonig, Gunda; Ganzleben, Ingo; Peccerella, Teresa; Casanovas, Guillem; Brodziak-Jarosz, Lidia; Breitkopf-Heinlein, Katja; Dick, Tobias P.; Seitz, Helmut-Karl; Muckenthaler, Martina U.; Mueller, Sebastian

2012-01-01

The peptide hormone hepcidin regulates mammalian iron homeostasis by blocking ferroportin-mediated iron export from macrophages and the duodenum. During inflammation, hepcidin is strongly induced by interleukin 6, eventually leading to the anemia of chronic disease. Here we show that hepatoma cells and primary hepatocytes strongly up-regulate hepcidin when exposed to low concentrations of H2O2 (0.3–6 μm), concentrations that are comparable with levels of H2O2 released by inflammatory cells. In contrast, bolus treatment of H2O2 has no effect at low concentrations and even suppresses hepcidin at concentrations of >50 μm. H2O2 treatment synergistically stimulates hepcidin promoter activity in combination with recombinant interleukin-6 or bone morphogenetic protein-6 and in a manner that requires a functional STAT3-responsive element. The H2O2-mediated hepcidin induction requires STAT3 phosphorylation and is effectively blocked by siRNA-mediated STAT3 silencing, overexpression of SOCS3 (suppressor of cytokine signaling 3), and antioxidants such as N-acetylcysteine. Glycoprotein 130 (gp130) is required for H2O2 responsiveness, and Janus kinase 1 (JAK1) is required for adequate basal signaling, whereas Janus kinase 2 (JAK2) is dispensable upstream of STAT3. Importantly, hepcidin levels are also increased by intracellular H2O2 released from the respiratory chain in the presence of rotenone or antimycin A. Our results suggest a novel mechanism of hepcidin regulation by nanomolar levels of sustained H2O2. Thus, similar to cytokines, H2O2 provides an important regulatory link between inflammation and iron metabolism. PMID:22932892

Mitotic phosphorylation of VCIP135 blocks p97ATPase-mediated Golgi membrane fusion

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Totsukawa, Go; Matsuo, Ayaka; Kubota, Ayano; Taguchi, Yuya; Kondo, Hisao, E-mail: hk228@med.kyushu-u.ac.jp

2013-04-05

Highlights: •VCIP135 is mitotically phosphorylated on Threonine-760 and Serine-767 by Cdc2. •Phosphorylated VCIP135 does not bind to p97ATPase. •The phosphorylation of VCIP135 inhibits p97ATPase-mediated Golgi membrane fusion. -- Abstract: In mammals, the Golgi apparatus is disassembled early mitosis and reassembled at the end of mitosis. For Golgi disassembly, membrane fusion needs to be blocked. Golgi biogenesis requires two distinct p97ATPase-mediated membrane fusion, the p97/p47 and p97/p37 pathways. We previously reported that p47 phosphorylation on Serine-140 and p37 phosphorylation on Serine-56 and Threonine-59 result in mitotic inhibition of the p97/p47 and the p97/p37 pathways, respectively [11,14]. In this study, we show another mechanism of mitotic inhibition of p97-mediated Golgi membrane fusion. We clarified that VCIP135, an essential factor in both p97 membrane fusion pathways, is phosphorylated on Threonine-760 and Serine-767 by Cdc2 at mitosis and that this phosphorylated VCIP135 does not bind to p97. An in vitro Golgi reassembly assay revealed that VCIP135(T760E, S767E), which mimics mitotic phosphorylation, caused no cisternal regrowth. Our results indicate that the phosphorylation of VCIP135 on Threonine-760 and Serine-767 inhibits p97-mediated Golgi membrane fusion at mitosis.

Avicin D: a protein reactive plant isoprenoid dephosphorylates Stat 3 by regulating both kinase and phosphatase activities.

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Valsala Haridas

Full Text Available Avicins, a class of electrophilic triterpenoids with pro-apoptotic, anti-inflammatory and antioxidant properties, have been shown to induce redox-dependant post-translational modification of cysteine residues to regulate protein function. Based on (a the cross-talk that occurs between redox and phosphorylation processes, and (b the role of Stat3 in the process of apoptosis and carcinogenesis, we chose to study the effects of avicins on the processes of phosphorylation/dephosphorylation in Stat3. Avicins dephosphorylate Stat3 in a variety of human tumor cell lines, leading to a decrease in the transcriptional activity of Stat3. The expression of Stat3-regulated proteins such as c-myc, cyclin D1, Bcl2, survivin and VEGF were reduced in response to avicin treatment. Underlying avicin-induced dephosphorylation of Stat3 was dephosphorylation of JAKs, as well as activation of protein phosphatase-1. Downregulation of both Stat3 activity and expression of Stat 3-controlled pro-survival proteins, contributes to the induction of apoptosis in avicin treated tumor cells. Based on the role of Stat3 in inflammation and wounding, and the in vivo inhibition of VEGF by avicins in a mouse skin carcinogenesis model, it is likely that avicin-induced inhibition of Stat3 activity results in the suppression of the pro-inflammatory and pro-oxidant stromal environment of tumors. Activation of PP-1, which also acts as a cellular economizer, combined with the redox regulation by avicins, can aid in redirecting metabolism from growth promoting anabolic to energy sparing pathways.

Ginkgolide B Suppresses TLR4-Mediated Inflammatory Response by Inhibiting the Phosphorylation of JAK2/STAT3 and p38 MAPK in High Glucose-Treated HUVECs

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Kun Chen

2017-01-01

Full Text Available Aim. Ginkgolide B is a Ginkgo biloba leaf extract that has been identified as a natural platelet-activating factor receptor (PAFR antagonist. We investigated the effect of ginkgolide B on high glucose-induced TLR4 activation in human umbilical vein endothelial cells (HUVECs. Methods. Protein expression was analyzed by immunoblotting. Small-interfering RNA (siRNA was used to knock down PAFR and TLR4 expression. Results. Ginkgolide B suppressed the expression of TLR4 and MyD88 that was induced by high glucose. Ginkgolide B also reduced the levels of platelet endothelial cell adhesion molecule-1, interleukin-6, and monocyte chemotactic protein 1. Further, we examined the association between PAFR and TLR4 by coimmunoprecipitation. The result showed that high glucose treatment caused the binding of PAFR and TLR4, whereas ginkgolide B abolished this binding. The functional analysis indicated that PAFR siRNA treatment reduced TLR4 expression, and TLR4 siRNA treatment decreased PAFR expression in high glucose-treated HUVECs, further supporting the coimmunoprecipitation data. Ginkgolide B inhibited the phosphorylation of Janus kinase 2 (JAK2/signal transducer and activator of transcription 3 (STAT3 and p38 mitogen-activated protein kinase (MAPK. Conclusion. Ginkgolide B exerted protective effects by inhibiting the TLR4-mediated inflammatory response in high glucose-treated endothelial cells. The mechanism of action of ginkgolide B might be associated with inhibition of the JAK2/STAT3 and p38 MAPK phosphorylation.

Ionization of amphiphilic acidic block copolymers.

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Colombani, Olivier; Lejeune, Elise; Charbonneau, Céline; Chassenieux, Christophe; Nicolai, Taco

2012-06-28

The ionization behavior of an amphiphilic diblock copolymer poly(n-butyl acrylate(50%)-stat-acrylic acid(50%))(100)-block-poly(acrylic acid)(100) (P(nBA(50%)-stat-AA(50%))(100)-b-PAA(100), DH50) and of its equivalent triblock copolymer P(nBA(50%)-stat-AA(50%))(100)-b-PAA(200)-b-P(nBA(50%)-stat-AA(50%))(100) (TH50) were studied by potentiometric titration either in pure water or in 0.5 M NaCl. These polymers consist of a hydrophilic acidic block (PAA) connected to a hydrophobic block, P(nBA(50%)-stat-AA(50%))(100), whose hydrophobic character has been mitigated by copolymerization with hydrophilic units. We show that all AA units, even those in the hydrophobic block could be ionized. However, the AA units within the hydrophobic block were less acidic than those in the hydrophilic block, resulting in the preferential ionization of the latter block. The preferential ionization of PAA over that of P(nBA(50%)-stat-AA(50%))(100) was stronger at higher ionic strength. Remarkably, the covalent bonds between the PAA and P(nBA(50%)-stat-AA(50%))(100) blocks in the diblock or the triblock did not affect the ionization of each block, although the self-association of the block copolymers into spherical aggregates modified the environment of the PAA blocks compared to when PAA was molecularly dispersed.

STAT6 Mediates Interleukin-4 Growth Inhibition in Human Breast Cancer Cells

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Jennifer L. Gooch

2002-01-01

Full Text Available In addition to acting as a hematopoietic growth factor, interleukin-4 (IL-4 inhibits growth of some transformed cells in vitro and in vivo. In this study, we show that insulin receptor substrate (IRS-1, IRS-2, and signal transducer and activator of transcription 6 (STAT6 are phosphorylated following IL-4 treatment in MCF-7 breast cancer cells. STAT6 DNA binding is enhanced by IL-4 treatment. STAT6 activation occurs even after IRS-1 depletion, suggesting the two pathways are independent. To examine the role of STAT6 in IL-4-mediated growth inhibition and apoptosis, a fulllength STAT6 cDNA was transfected into MCF-7 cells. Transient overexpression of STAT6 resulted in both cytoplasmic and nuclear expression of the protein, increased DNA binding in response to IL-4, and increased transactivation of an IL-4 responsive promoter. In STAT6-transfected cells, basal proliferation was reduced whereas apoptosis was increased. Finally, stable expression of STAT6 resulted in reduced foci formation compared to vector-transfected cells alone. These results suggest STAT6 is required for IL-4mediated growth inhibition and induction of apoptosis in human breast cancer cells.

Fludarabine inhibits STAT1-mediated up-regulation of caspase-3 expression in dexamethasone-induced osteoblasts apoptosis and slows the progression of steroid-induced avascular necrosis of the femoral head in rats.

Science.gov (United States)

Feng, Zhenhua; Zheng, Wenhao; Tang, Qian; Cheng, Liang; Li, Hang; Ni, Wenfei; Pan, Xiaoyun

2017-08-01

Steroid-induced avascular necrosis of the femoral head (SANFH) is a major limitation of long-term or excessive clinical administration of glucocorticoids. Fludarabine, which is a compound used to treat various hematological malignancies, such as chronic lymphocytic leukemia, acts by down-regulating signal transducer and activator of transcription 1 (STAT1) by inhibiting STAT1 phosphorylation in both normal and cancer cells. This study assessed the effects of fludarabine in vitro (primary murine osteoblasts) and in vivo (rat SANFH model). In vitro, pretreatment with fludarabine significantly inhibited Dexamethasone (Dex)-induced apoptosis in osteoblasts, which was examined by TUNEL staining. Treatment with Dex caused a remarkable decrease in the expression of Bcl-2; an increase in cytochrome c release; activation of BAX, caspase-9, and caspase-3; and an obvious enhancement in STAT1 phosphorylation. However, treatment resulted in the up-regulation of caspase-3 expression. Enhanced P-STAT1 activity and up-regulation of caspase-3 expression were also observed in osteoblasts. In vivo, the subchondral trabeculae in fludarabine-treated rats exhibited less bone loss and a lower ratio of empty lacunae. Taken together, our results suggest that STAT1-mediated up-regulation of caspase-3 is involved in osteoblast apoptosis induced by Dex and indicates that fludarabine may serve as a potential agent for the treatment of SANFH.

Involvement of PKA and HO-1 signaling in anti-inflammatory effects of surfactin in BV-2 microglial cells

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Park, Sun Young; Kim, Ji-Hee [Department of Molecular Biology, College of Natural Sciences, Pusan National University, Jangjeon-dong, Keumjeong-gu, Busan 609-735 (Korea, Republic of); Lee, Sang Joon [Department of Microbiology, College of Natural Sciences, Pusan National University, Jangjeon-dong, Keumjeong-gu, Busan 609-735 (Korea, Republic of); Kim, YoungHee, E-mail: yheekim@pusan.ac.kr [Department of Molecular Biology, College of Natural Sciences, Pusan National University, Jangjeon-dong, Keumjeong-gu, Busan 609-735 (Korea, Republic of)

2013-04-01

Surfactin, one of the most powerful biosurfactants, is a bacterial cyclic lipopeptide. Here, we investigated the anti-neuroinflammatory properties of surfactin in lipoteichoic acid (LTA)-stimulated BV-2 microglial cells. Surfactin significantly inhibited excessive production of the pro-inflammatory mediators TNF-α, IL-1β, IL-6, monocyte chemoattractant protein-1 (MCP-1), prostaglandin E{sub 2} (PGE{sub 2}), nitric oxide (NO) and reactive oxygen species (ROS), and suppressed the expression of matrix metalloproteinase-9 (MMP-9), inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2). Subsequent mechanistic studies revealed that surfactin inhibited LTA-induced nuclear factor-kappaB (NF-κB) and signal transducer and activator of transcription-1 (STAT-1) activation. However, surfactin increases the phosphorylation of the STAT-3, a component of the homeostatic mechanism causing anti-inflammatory events. We also demonstrated that surfactin induces heme oxygenase-1 (HO-1) expression and nuclear factor-regulated factor-2 (Nrf-2) activation, and that the anti-inflammatory effects of surfactin are abrogated by small interfering RNA-mediated knock-down of HO-1 or Nrf-2. Interestingly, we found that surfactin increased the level of cAMP and induced phosphorylation of cAMP responsive element binding protein (CREB) in microglial cells. Furthermore, treatment with the protein kinase A (PKA) inhibitor, H-89, blocked HO-1 induction by surfactin and abolished surfactin's suppressive effects on ROS and NO production. These results indicate that HO-1 and its upstream effector, PKA, play a pivotal role in the anti-neuroinflammatory response of surfactin in LTA-stimulated microglia. Therefore, surfactin might have therapeutic potential for neuroprotective agents to treat inflammatory and neurodegenerative diseases. - Highlights: ► Surfactin inhibits proinflammatory mediator synthesis in LTA-activated BV-2 cells. ► Surfactin suppresses NF-κB and STAT-1, but potentiates

Involvement of PKA and HO-1 signaling in anti-inflammatory effects of surfactin in BV-2 microglial cells

International Nuclear Information System (INIS)

Park, Sun Young; Kim, Ji-Hee; Lee, Sang Joon; Kim, YoungHee

2013-01-01

Surfactin, one of the most powerful biosurfactants, is a bacterial cyclic lipopeptide. Here, we investigated the anti-neuroinflammatory properties of surfactin in lipoteichoic acid (LTA)-stimulated BV-2 microglial cells. Surfactin significantly inhibited excessive production of the pro-inflammatory mediators TNF-α, IL-1β, IL-6, monocyte chemoattractant protein-1 (MCP-1), prostaglandin E 2 (PGE 2 ), nitric oxide (NO) and reactive oxygen species (ROS), and suppressed the expression of matrix metalloproteinase-9 (MMP-9), inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2). Subsequent mechanistic studies revealed that surfactin inhibited LTA-induced nuclear factor-kappaB (NF-κB) and signal transducer and activator of transcription-1 (STAT-1) activation. However, surfactin increases the phosphorylation of the STAT-3, a component of the homeostatic mechanism causing anti-inflammatory events. We also demonstrated that surfactin induces heme oxygenase-1 (HO-1) expression and nuclear factor-regulated factor-2 (Nrf-2) activation, and that the anti-inflammatory effects of surfactin are abrogated by small interfering RNA-mediated knock-down of HO-1 or Nrf-2. Interestingly, we found that surfactin increased the level of cAMP and induced phosphorylation of cAMP responsive element binding protein (CREB) in microglial cells. Furthermore, treatment with the protein kinase A (PKA) inhibitor, H-89, blocked HO-1 induction by surfactin and abolished surfactin's suppressive effects on ROS and NO production. These results indicate that HO-1 and its upstream effector, PKA, play a pivotal role in the anti-neuroinflammatory response of surfactin in LTA-stimulated microglia. Therefore, surfactin might have therapeutic potential for neuroprotective agents to treat inflammatory and neurodegenerative diseases. - Highlights: ► Surfactin inhibits proinflammatory mediator synthesis in LTA-activated BV-2 cells. ► Surfactin suppresses NF-κB and STAT-1, but potentiates phosphorylation

Identification of a growth hormone-responsive STAT5-binding element in the rat insulin 1 gene

DEFF Research Database (Denmark)

Galsgaard, E D; Gouilleux, F; Groner, B

1996-01-01

promoter activity 2-fold, and this stimulation was abolished by introduction of a block mutation in a gamma-interferon-activated sequence (GAS)-like element (GLE) with the sequence 5'-TTCTGGGAA-3' located in the rat insulin 1 enhancer at position -330 to -322. This element, termed Ins-GLE, was able...... transfected with STAT5 and GH receptor cDNAs, it was found that expression of STAT5 was necessary for GH induction of these two DNA-binding complexes. These results suggest that GH stimulates insulin 1 promoter activity by inducing the binding of STAT5 to Ins-GLE.......GH and PRL stimulate both proliferation and insulin production in pancreatic beta-cells as well as in the rat insulinoma cell line RIN-5AH, We report here that human GH increases insulin mRNA levels in RIN-5AH cells via both somatogenic and lactogenic receptors. GH stimulated the rat insulin 1...

Adenosine A1 Receptor Protects Against Cisplatin Ototoxicity by Suppressing the NOX3/STAT1 Inflammatory Pathway in the Cochlea

Science.gov (United States)

Kaur, Tejbeer; Borse, Vikrant; Sheth, Sandeep; Sheehan, Kelly; Ghosh, Sumana; Tupal, Srinivasan; Jajoo, Sarvesh; Mukherjea, Debashree; Rybak, Leonard P.

2016-01-01

Cisplatin is a commonly used antineoplastic agent that produces ototoxicity that is mediated in part by increasing levels of reactive oxygen species (ROS) via the NOX3 NADPH oxidase pathway in the cochlea. Recent studies implicate ROS generation in mediating inflammatory and apoptotic processes and hearing loss by activating signal transducer and activator of transcription (STAT1). In this study, we show that the adenosine A1 receptor (A1AR) protects against cisplatin ototoxicity by suppressing an inflammatory response initiated by ROS generation via NOX3 NADPH oxidase, leading to inhibition of STAT1. Trans-tympanic administration of the A1AR agonist R-phenylisopropyladenosine (R-PIA) inhibited cisplatin-induced ototoxicity, as measured by auditory brainstem responses and scanning electron microscopy in male Wistar rats. This was associated with reduced NOX3 expression, STAT1 activation, tumor necrosis factor-α (TNF-α) levels, and apoptosis in the cochlea. In vitro studies in UB/OC-1 cells, an organ of Corti immortalized cell line, showed that R-PIA reduced cisplatin-induced phosphorylation of STAT1 Ser727 (but not Tyr701) and STAT1 luciferase activity by suppressing the ERK1/2, p38, and JNK mitogen-activated protein kinase (MAPK) pathways. R-PIA also decreased the expression of STAT1 target genes, such as TNF-α, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) and reduced cisplatin-mediated apoptosis. These data suggest that the A1AR provides otoprotection by suppressing NOX3 and inflammation in the cochlea and could serve as an ideal target for otoprotective drug therapy. SIGNIFICANCE STATEMENT Cisplatin is a widely used chemotherapeutic agent for the treatment of solid tumors. Its use results in significant and permanent hearing loss, for which no US Food and Drug Administration-approved treatment is currently available. In this study, we targeted the cochlear adenosine A1 receptor (A1AR) by trans-tympanic injections of the agonist R

STAT proteins: from normal control of cellular events to tumorigenesis.

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Calò, Valentina; Migliavacca, Manuela; Bazan, Viviana; Macaluso, Marcella; Buscemi, Maria; Gebbia, Nicola; Russo, Antonio

2003-11-01

Signal transducers and activators of transcription (STAT) proteins comprise a family of transcription factors latent in the cytoplasm that participate in normal cellular events, such as differentiation, proliferation, cell survival, apoptosis, and angiogenesis following cytokine, growth factor, and hormone signaling. STATs are activated by tyrosine phosphorylation, which is normally a transient and tightly regulates process. Nevertheless, several constitutively activated STATs have been observed in a wide number of human cancer cell lines and primary tumors, including blood malignancies and solid neoplasias. STATs can be divided into two groups according to their specific functions. One is made up of STAT2, STAT4, and STAT6, which are activated by a small number of cytokines and play a distinct role in the development of T-cells and in IFNgamma signaling. The other group includes STAT1, STAT3, and STAT5, activated in different tissues by means of a series of ligands and involved in IFN signaling, development of the mammary gland, response to GH, and embriogenesis. This latter group of STATS plays an important role in controlling cell-cycle progression and apoptosis and thus contributes to oncogenesis. Although an increased expression of STAT1 has been observed in many human neoplasias, this molecule can be considered a potential tumor suppressor, since it plays an important role in growth arrest and in promoting apoptosis. On the other hand, STAT3 and 5 are considered as oncogenes, since they bring about the activation of cyclin D1, c-Myc, and bcl-xl expression, and are involved in promoting cell-cycle progression, cellular transformation, and in preventing apoptosis.

ERK, Akt, and STAT5 are differentially activated by the two growth hormone receptors subtypes of a teleost fish (Oncorhynchus mykiss

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Jeffrey eKittilson

2011-09-01

Full Text Available Previously, we found that the teleost fish, rainbow trout, possesses two growth hormone receptor (GHR subtypes that display distinct ligand binding and agonist-induced regulation features. In this study, we used Chinese hamster ovary-K1 cells stably transfected individually with the two trout GHR subtypes, GHR1 and GHR2, to elucidate receptor-effector pathway linkages. Growth hormone (GH stimulated rapid (5-10 min phosphorylation of ERK, Akt, JAk2, and STAT5 in both GHR1- and GHR2-expressing cells; however; STAT5 was activated to a greater extent through GHR1 than through GHR2, whereas ERK and Akt were activated to a greater through GHR2 than through GHR1. Although blockade of the ERK pathway had no effect on the activation of Akt, inhibition of PI3k-Akt partially prevented activation of ERK, suggesting cross-talk between the ERK and PI3K-Akt pathways. JAK2 inhibition completely blocked activation of ERK, Akt, and STAT5, suggesting that all of these pathways link to GHR1 and GHR2 via JAK2. These findings establish important receptor-effector pathway linkages and suggest that the GHR subtypes of teleost fish may be functionally distinct.

Quercetin inhibits epithelial–mesenchymal transition, decreases invasiveness and metastasis, and reverses IL-6 induced epithelial–mesenchymal transition, expression of MMP by inhibiting STAT3 signaling in pancreatic cancer cells

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Yu D

2017-09-01

Full Text Available Dinglai Yu,1 Tingting Ye,1 Yukai Xiang,1 Zhehao Shi,1 Jie Zhang,1 Bin Lou,1 Fan Zhang,1 Bicheng Chen,1,2 Mengtao Zhou1 1Department of Surgery, The First Affiliated Hospital, Wenzhou Medical University, Wenzhou, Zhejiang Province, People’s Republic of China; 2Zhejiang Provincial Top Key Discipline in Surgery, Wenzhou Key Laboratory of Surgery, Wenzhou, Zhejiang Province, People’s Republic of China Abstract: Quercetin, a flavone, is multifaceted, having anti-oxidative, anti-inflammatory, and anticancer properties. In the present study, we explored the effects of quercetin on the epithelial–mesenchymal transition (EMT and invasion of pancreatic cancer cells and the underlying mechanisms. We noted that quercetin exerted pronounced inhibitory effects in PANC-1 and PATU-8988 cells. Moreover, quercetin inhibited EMT and decreased the secretion of matrix metalloproteinase (MMP. Meanwhile, we determined the activity of STAT3 after quercetin treatment. STAT3 phosphorylation decreased following treatment with quercetin. We also used activating agent of STAT3, IL-6, to induce an increase in cell malignancy and to observe the effects of treatment with quercetin. As expected, the EMT and MMP secretion increased with activation of the STAT3 signaling pathway, and quercetin reversed IL-6-induced EMT, invasion, and migration. Therefore, our results demonstrate that quercetin triggers inhibition of EMT, invasion, and metastasis by blocking the STAT3 signaling pathway, and thus, quercetin merits further investigation. Keywords: quercetin, EMT, MMPs, STAT3, pancreatic cancer

5-hydroxy-2-methyl-1,4-naphthoquinone, a vitamin K3 analogue, suppresses STAT3 activation pathway through induction of protein tyrosine phosphatase, SHP-1: potential role in chemosensitization.

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Sandur, Santosh K; Pandey, Manoj K; Sung, Bokyung; Aggarwal, Bharat B

2010-01-01

The activation of signal transducers and activators of transcription 3 (STAT3) has been linked with carcinogenesis through survival, proliferation, and angiogenesis of tumor cells. Agents that can suppress STAT3 activation have potential not only for prevention but also for treatment of cancer. In the present report, we investigated whether 5-hydroxy-2-methyl-1,4-naphthoquinone (plumbagin), an analogue of vitamin K, and isolated from chitrak (Plumbago zeylanica), an Ayurvedic medicinal plant, can modulate the STAT3 pathway. We found that plumbagin inhibited both constitutive and interleukin 6-inducible STAT3 phosphorylation in multiple myeloma (MM) cells and this correlated with the inhibition of c-Src, Janus-activated kinase (JAK)1, and JAK2 activation. Vanadate, however, reversed the plumbagin-induced downregulation of STAT3 activation, suggesting the involvement of a protein tyrosine phosphatase. Indeed, we found that plumbagin induced the expression of the protein tyrosine phosphatase, SHP-1, and silencing of the SHP-1 abolished the effect of plumbagin. This agent also downregulated the expression of STAT3-regulated cyclin D1, Bcl-xL, and vascular endothelial growth factor; activated caspase-3; induced poly (ADP ribose) polymerase cleavage; and increased the sub-G(1) population of MM cells. Consistent with these results, overexpression of constitutive active STAT3 significantly reduced the plumbagin-induced apoptosis. When compared with AG490, a rationally designed STAT3/JAK2 inhibitor, plumbagin was found more potent in suppressing the proliferation of cells. Plumbagin also significantly potentiated the apoptotic effects of thalidomide and bortezomib in MM cells. Overall, these results suggest that the plumbagin inhibits STAT3 activation pathway through the induction of SHP-1 and this may mediate the sensitization of STAT3 overexpressing cancers to chemotherapeutic agents.

Inhibition of STAT3 activity delays obesity-induced thyroid carcinogenesis in a mouse model

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Park, Jeong Won; Han, Cho Rong; Zhao, Li; Willingham, Mark C.; Cheng, Sheue-yann

2015-01-01

Compelling epidemiologic studies indicate that obesity is a risk factor for many human cancers, including thyroid cancer. In recent decades, the incidence of thyroid cancer has dramatically increased along with a marked rise in obesity prevalence. We previously demonstrated that a high fat diet (HFD) effectively induced the obese phenotype in a mouse model of thyroid cancer (ThrbPV/PVPten+/− mice). Moreover, HFD activates the STAT3 signal pathway to promote more aggressive tumor phenotypes. The aim of the present study was to evaluate the effect of S3I-201, a specific inhibitor of STAT3 activity, on HFD-induced aggressive cancer progression in the mouse model of thyroid cancer. Wild type and ThrbPV/PVPten+/− mice were treated with HFD together with S3I-201 or vehicle-only as controls. We assessed the effects of S3I-201 on HFD-induced thyroid cancer progression, the leptin-JAK2-STAT3 signaling pathway, and key regulators of epithelial-mesenchymal transition. S3I-201 effectively inhibited HFD-induced aberrant activation of STAT3 and its downstream targets to markedly inhibit thyroid tumor growth and to prolong survival. Decreased protein levels of cyclins D1 and B1, cyclin dependent kinase (CDK) 4, CDK 6, and phosphorylated retinoblastoma protein led to the inhibition of tumor cell proliferation in S3I-201-treated ThrbPV/PVPten+/− mice. Reduced occurrence of vascular invasion and blocking of anaplasia and lung metastasis in thyroid tumors of S3I-201-treated ThrbPV/PVPten+/− mice were mediated via decreased expression of vimentin and matrix metalloproteinases, two key effectors of epithelial-mesenchymal transition. The present findings suggest that inhibition of the STAT3 activity would be a novel treatment strategy for obesity-induced thyroid cancer. PMID:26552408

Reversal of DDK-Mediated MCM Phosphorylation by Rif1-PP1 Regulates Replication Initiation and Replisome Stability Independently of ATR/Chk1.

Science.gov (United States)

Alver, Robert C; Chadha, Gaganmeet Singh; Gillespie, Peter J; Blow, J Julian

2017-03-07

Dbf4-dependent kinases (DDKs) are required for the initiation of DNA replication, their essential targets being the MCM2-7 proteins. We show that, in Xenopus laevis egg extracts and human cells, hyper-phosphorylation of DNA-bound Mcm4, but not phosphorylation of Mcm2, correlates with DNA replication. These phosphorylations are differentially affected by the DDK inhibitors PHA-767491 and XL413. We show that DDK-dependent MCM phosphorylation is reversed by protein phosphatase 1 (PP1) targeted to chromatin by Rif1. Loss of Rif1 increased MCM phosphorylation and the rate of replication initiation and also compromised the ability of cells to block initiation when challenged with replication inhibitors. We also provide evidence that Rif1 can mediate MCM dephosphorylation at replication forks and that the stability of dephosphorylated replisomes strongly depends on Chk1 activity. We propose that both replication initiation and replisome stability depend on MCM phosphorylation, which is maintained by a balance of DDK-dependent phosphorylation and Rif1-mediated dephosphorylation. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Curcumin induces growth-arrest and apoptosis in association with the inhibition of constitutively active JAK-STAT pathway in T cell leukemia

International Nuclear Information System (INIS)

Rajasingh, Johnson; Raikwar, Himanshu P.; Muthian, Gladson; Johnson, Caroline; Bright, John J.

2006-01-01

Adult T cell leukemia is an aggressive and frequently fatal malignancy that expressess constitutively activated growth-signaling pathways in association with deregulated growth and resistance to apoptosis. Curcumin (diferuloylmethane) is a naturally occurring yellow pigment, isolated from the rhizomes of the plant Curcuma longa that has traditionally been used in the treatment of injury and inflammation. But the effect and mechanism of action of curcumin on T cell leukemia is not known. To investigate the antitumor activity of curcumin in T cell leukemia, we examined its effect on constitutive phosphorylation of JAK and STAT proteins, proliferation, and apoptosis in HTLV-I-transformed T cell lines. HTLV-I-transformed T cell leukemia lines, MT-2, HuT-102, and SLB-1, express constitutively phosphorylated JAK3, TYK2, STAT3, and STAT5 signaling proteins. In vitro treatment with curcumin induced a dose-dependent decrease in JAK and STAT phosphorylation resulting in the induction of growth-arrest and apoptosis in T cell leukemia. The induction of growth-arrest and apoptosis in association with the blockade of constitutively active JAK-STAT pathway suggests this be a mechanism by which curcumin induces antitumor activity in T cell leukemia

Dynamic trafficking of STAT5 depends on an unconventional nuclear localization signal

Science.gov (United States)

Shin, Ha Youn; Reich, Nancy C.

2013-01-01

Summary Signal transducer and activator of transcription 5 (STAT5) is crucial for physiological processes that include hematopoiesis, liver metabolism and mammary gland development. However, aberrant continual activity of STAT5 has been causally linked to human leukemias and solid tumor formation. As a regulated transcription factor, precise cellular localization of STAT5 is essential. Conventional nuclear localization signals consist of short stretches of basic amino acids. In this study, we provide evidence that STAT5 nuclear import is dependent on an unconventional nuclear localization signal that functions within the conformation of an extensive coiled-coil domain. Both in vitro binding and in vivo functional assays reveal that STAT5 nuclear import is mediated by the importin-α3/β1 system independently of STAT5 activation by tyrosine phosphorylation. The integrity of the coiled-coil domain is essential for STAT5 transcriptional induction of the β-casein gene following prolactin stimulation as well as its ability to synergize with the glucocorticoid receptor. The glucocorticoid receptor accumulates in the nucleus in response to prolactin and this nuclear import is dependent on STAT5 nuclear import. STAT5 continually shuttles in and out of the nucleus and live cell imaging demonstrates that STAT5 nuclear export is mediated by both chromosome region maintenance 1 (Crm1)-dependent and Crm1-independent pathways. A Crm1-dependent nuclear export signal was identified within the STAT5 N-terminus. These findings provide insight into the fundamental mechanisms that regulate STAT5 nuclear trafficking and cooperation with the glucocorticoid receptor and provide a basis for clinical intervention of STAT5 function in disease. PMID:23704351

Lloviu virus VP24 and VP35 proteins function as innate immune antagonists in human and bat cells

International Nuclear Information System (INIS)

Feagins, Alicia R.; Basler, Christopher F.

2015-01-01

Lloviu virus (LLOV) is a new member of the filovirus family that also includes Ebola virus (EBOV) and Marburg virus (MARV). LLOV has not been cultured; however, its genomic RNA sequence indicates the coding capacity to produce homologs of the EBOV and MARV VP24, VP35, and VP40 proteins. EBOV and MARV VP35 proteins inhibit interferon (IFN)-alpha/beta production and EBOV VP35 blocks activation of the antiviral kinase PKR. The EBOV VP24 and MARV VP40 proteins inhibit IFN signaling, albeit by different mechanisms. Here we demonstrate that LLOV VP35 suppresses Sendai virus induced IFN regulatory factor 3 (IRF3) phosphorylation, IFN-α/β production, and PKR phosphorylation. Additionally, LLOV VP24 blocks tyrosine phosphorylated STAT1 binding to karyopherin alpha 5 (KPNA5), STAT1 nuclear accumulation, and IFN-induced gene expression. LLOV VP40 lacks detectable IFN antagonist function. These activities parallel EBOV IFN inhibitory functions. EBOV and LLOV VP35 and VP24 proteins also inhibit IFN responses in bat cells. These data suggest that LLOV infection will block innate immune responses in a manner similar to EBOV. - Highlights: • Lloviu virus (LLOV) is a new member of the filovirus family. • LLOV VP35 blocks IRF3 phosphorylation, IFN-α/β production and PKR phosphorylation. • LLOV VP24 inhibits IFN responses by targeting phospho-STAT1 KPNA interaction. • Infection by LLOV may block innate immune responses in a manner similar to EBOV.

Lloviu virus VP24 and VP35 proteins function as innate immune antagonists in human and bat cells

Energy Technology Data Exchange (ETDEWEB)

Feagins, Alicia R.; Basler, Christopher F., E-mail: chris.basler@mssm.edu

2015-11-15

Lloviu virus (LLOV) is a new member of the filovirus family that also includes Ebola virus (EBOV) and Marburg virus (MARV). LLOV has not been cultured; however, its genomic RNA sequence indicates the coding capacity to produce homologs of the EBOV and MARV VP24, VP35, and VP40 proteins. EBOV and MARV VP35 proteins inhibit interferon (IFN)-alpha/beta production and EBOV VP35 blocks activation of the antiviral kinase PKR. The EBOV VP24 and MARV VP40 proteins inhibit IFN signaling, albeit by different mechanisms. Here we demonstrate that LLOV VP35 suppresses Sendai virus induced IFN regulatory factor 3 (IRF3) phosphorylation, IFN-α/β production, and PKR phosphorylation. Additionally, LLOV VP24 blocks tyrosine phosphorylated STAT1 binding to karyopherin alpha 5 (KPNA5), STAT1 nuclear accumulation, and IFN-induced gene expression. LLOV VP40 lacks detectable IFN antagonist function. These activities parallel EBOV IFN inhibitory functions. EBOV and LLOV VP35 and VP24 proteins also inhibit IFN responses in bat cells. These data suggest that LLOV infection will block innate immune responses in a manner similar to EBOV. - Highlights: • Lloviu virus (LLOV) is a new member of the filovirus family. • LLOV VP35 blocks IRF3 phosphorylation, IFN-α/β production and PKR phosphorylation. • LLOV VP24 inhibits IFN responses by targeting phospho-STAT1 KPNA interaction. • Infection by LLOV may block innate immune responses in a manner similar to EBOV.

The STAT4 SLE risk allele rs7574865[T] is associated with increased IL-12-induced IFN-γ production in T cells from patients with SLE.

Science.gov (United States)

Hagberg, Niklas; Joelsson, Martin; Leonard, Dag; Reid, Sarah; Eloranta, Maija-Leena; Mo, John; Nilsson, Magnus K; Syvänen, Ann-Christine; Bryceson, Yenan T; Rönnblom, Lars

2018-02-23

Genetic variants in the transcription factor STAT4 are associated with increased susceptibility to systemic lupus erythematosus (SLE) and a more severe disease phenotype. This study aimed to clarify how the SLE-associated intronic STAT4 risk allele rs7574865[T] affects the function of immune cells in SLE. Peripheral blood mononuclear cells (PBMCs) were isolated from 52 genotyped patients with SLE. Phosphorylation of STAT4 (pSTAT4) and STAT1 (pSTAT1) in response to interferon (IFN)-α, IFN-γ or interleukin (IL)-12, total levels of STAT4, STAT1 and T-bet, and frequency of IFN-γ + cells on IL-12 stimulation were determined by flow cytometry in subsets of immune cells before and after preactivation of cells with phytohaemagglutinin (PHA) and IL-2. Cellular responses and phenotypes were correlated to STAT4 risk allele carriership. Janus kinase inhibitors (JAKi) selective for TYK2 (TYK2i) or JAK2 (JAK2i) were evaluated for inhibition of IL-12 or IFN-γ-induced activation of SLE PBMCs. In resting PBMCs, the STAT4 risk allele was neither associated with total levels of STAT4 or STAT1, nor cytokine-induced pSTAT4 or pSTAT1. Following PHA/IL-2 activation, CD8 + T cells from STAT4 risk allele carriers displayed increased levels of STAT4 resulting in increased pSTAT4 in response to IL-12 and IFN-α, and an augmented IL-12-induced IFN-γ production in CD8 + and CD4 + T cells. The TYK2i and the JAK2i efficiently blocked IL-12 and IFN-γ-induced activation of PBMCs from STAT4 risk patients, respectively. T cells from patients with SLE carrying the STAT4 risk allele rs7574865[T] display an augmented response to IL-12 and IFN-α. This subset of patients may benefit from JAKi treatment. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Roles of STATs signaling in cardiovascular diseases.

Science.gov (United States)

Kishore, Raj; Verma, Suresh K

2012-04-01

In cardiac and many other systems, chronic stress activates avfamily of structurally and functionally conserved receptors and their downstream signaling molecules that entail tyrosine, serine or threonine phosphorylation to transfer the messages to the genetic machinery. However, the activation of the Janus kinases (JAKs) and their downstream signal transducer and activator of transcription (STATs) proteins is both characteristic of and unique to cytokine and growth factor signaling which plays a central role in heart physiology. Dysregulation of JAK-STAT signaling is associated with various cardiovascular diseases. The molecular signaling and specificity of the JAK-STAT pathway are modulated at many levels by distinct regulatory proteins. Here, we review recent studies on the regulation of the STAT signaling pathway that will enhance our ability to design rational therapeutic strategies for stress-induced heart failure.

Marburg virus evades interferon responses by a mechanism distinct from ebola virus.

Directory of Open Access Journals (Sweden)

Charalampos Valmas

2010-01-01

Full Text Available Previous studies have demonstrated that Marburg viruses (MARV and Ebola viruses (EBOV inhibit interferon (IFN-alpha/beta signaling but utilize different mechanisms. EBOV inhibits IFN signaling via its VP24 protein which blocks the nuclear accumulation of tyrosine phosphorylated STAT1. In contrast, MARV infection inhibits IFNalpha/beta induced tyrosine phosphorylation of STAT1 and STAT2. MARV infection is now demonstrated to inhibit not only IFNalpha/beta but also IFNgamma-induced STAT phosphorylation and to inhibit the IFNalpha/beta and IFNgamma-induced tyrosine phosphorylation of upstream Janus (Jak family kinases. Surprisingly, the MARV matrix protein VP40, not the MARV VP24 protein, has been identified to antagonize Jak and STAT tyrosine phosphorylation, to inhibit IFNalpha/beta or IFNgamma-induced gene expression and to inhibit the induction of an antiviral state by IFNalpha/beta. Global loss of STAT and Jak tyrosine phosphorylation in response to both IFNalpha/beta and IFNgamma is reminiscent of the phenotype seen in Jak1-null cells. Consistent with this model, MARV infection and MARV VP40 expression also inhibit the Jak1-dependent, IL-6-induced tyrosine phosphorylation of STAT1 and STAT3. Finally, expression of MARV VP40 is able to prevent the tyrosine phosphorylation of Jak1, STAT1, STAT2 or STAT3 which occurs following over-expression of the Jak1 kinase. In contrast, MARV VP40 does not detectably inhibit the tyrosine phosphorylation of STAT2 or Tyk2 when Tyk2 is over-expressed. Mutation of the VP40 late domain, essential for efficient VP40 budding, has no detectable impact on inhibition of IFN signaling. This study shows that MARV inhibits IFN signaling by a mechanism different from that employed by the related EBOV. It identifies a novel function for the MARV VP40 protein and suggests that MARV may globally inhibit Jak1-dependent cytokine signaling.

Adenosine A1 Receptor Protects Against Cisplatin Ototoxicity by Suppressing the NOX3/STAT1 Inflammatory Pathway in the Cochlea.

Science.gov (United States)

Kaur, Tejbeer; Borse, Vikrant; Sheth, Sandeep; Sheehan, Kelly; Ghosh, Sumana; Tupal, Srinivasan; Jajoo, Sarvesh; Mukherjea, Debashree; Rybak, Leonard P; Ramkumar, Vickram

2016-04-06

Cisplatin is a commonly used antineoplastic agent that produces ototoxicity that is mediated in part by increasing levels of reactive oxygen species (ROS) via the NOX3 NADPH oxidase pathway in the cochlea. Recent studies implicate ROS generation in mediating inflammatory and apoptotic processes and hearing loss by activating signal transducer and activator of transcription (STAT1). In this study, we show that the adenosine A1 receptor (A1AR) protects against cisplatin ototoxicity by suppressing an inflammatory response initiated by ROS generation via NOX3 NADPH oxidase, leading to inhibition of STAT1. Trans-tympanic administration of the A1AR agonist R-phenylisopropyladenosine (R-PIA) inhibited cisplatin-induced ototoxicity, as measured by auditory brainstem responses and scanning electron microscopy in male Wistar rats. This was associated with reduced NOX3 expression, STAT1 activation, tumor necrosis factor-α (TNF-α) levels, and apoptosis in the cochlea. In vitro studies in UB/OC-1 cells, an organ of Corti immortalized cell line, showed that R-PIA reduced cisplatin-induced phosphorylation of STAT1 Ser(727) (but not Tyr(701)) and STAT1 luciferase activity by suppressing the ERK1/2, p38, and JNK mitogen-activated protein kinase (MAPK) pathways.R-PIA also decreased the expression of STAT1 target genes, such as TNF-α, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) and reduced cisplatin-mediated apoptosis. These data suggest that the A1AR provides otoprotection by suppressing NOX3 and inflammation in the cochlea and could serve as an ideal target for otoprotective drug therapy. Cisplatin is a widely used chemotherapeutic agent for the treatment of solid tumors. Its use results in significant and permanent hearing loss, for which no US Food and Drug Administration-approved treatment is currently available. In this study, we targeted the cochlear adenosine A1 receptor (A1AR) by trans-tympanic injections of the agonist R

Synergistic Effect of Radiation and Interleukin-6 on Hepatitis B Virus Reactivation in Liver Through STAT3 Signaling Pathway

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Chou, C.H.; Chen, P.-J.; Jeng, Y.-M.; Cheng, A.-L.; Huang, L.-R.; Cheng, J.C.-H.

2009-01-01

Purpose: Hepatitis B virus (HBV) reactivation can occur after radiotherapy (RT) for hepatobiliary malignancies. Our previous in vitro culture study identified interleukin-6 (IL-6) as the main bystander mediator of RT-induced HBV replication. We attempted to examine the molecular mechanism in HBV-transgenic mice. Methods and materials: HBV transgenic mice were treated with whole liver RT (4 Gy daily for 5 days) with or without administration of IL-6 (400 ng twice daily for 15 days). The serum level of HBV DNA was measured using real-time polymerase chain reaction, and the IL-6 concentration was measured using enzyme-linked immunosorbent assay. The intensity of immunostaining with antibodies to HBV core protein and phosphorylated signal transducer and activator of transcription (STAT)3 in the mouse liver was qualitatively analyzed. HepG2.2.15 cells (a human hepatoblastoma cell line that persistently produces HBV DNA) were used to investigate the molecular role of IL-6 plus RT in HBV reactivation. Results: HBV reactivation was induced in vivo with IL-6 plus RT (5.58-fold) compared with RT alone (1.31-fold, p = .005), IL-6 alone (1.31-fold, p = .005), or sham treatment (1.22-fold, p = .004). HBV core protein staining confirmed augmentation of intrahepatic HBV replication. IL-6 plus RT-induced HBV DNA replication in HepG2.2.15 cells was suppressed by the STAT3 inhibitor AG490 and by transfection with dominant-negative STAT3 plasmid. Phosphorylated STAT3 staining was strongest in liver tissue from mice treated with IL-6 plus RT. The mobility shift assay demonstrated that reactivation was mediated through the interaction of phosphorylated STAT3/hepatocyte nuclear factor-3 complex with HBV enhancer 1. Conclusion: RT to the liver and longer sustained IL-6 induced HBV reactivation through the STAT3 signal transduction pathway.

Role of STAT4 polymorphisms in systemic lupus erythematosus in a Japanese population: a case-control association study of the STAT1-STAT4 region

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Kawasaki, Aya; Ito, Ikue; Hikami, Koki; Ohashi, Jun; Hayashi, Taichi; Goto, Daisuke; Matsumoto, Isao; Ito, Satoshi; Tsutsumi, Akito; Koga, Minori; Arinami, Tadao; Graham, Robert R; Hom, Geoffrey; Takasaki, Yoshinari; Hashimoto, Hiroshi; Behrens, Timothy W; Sumida, Takayuki; Tsuchiya, Naoyuki

2008-01-01

Introduction Recent studies identified STAT4 (signal transducers and activators of transcription-4) as a susceptibility gene for systemic lupus erythematosus (SLE). STAT1 is encoded adjacently to STAT4 on 2q32.2-q32.3, upregulated in peripheral blood mononuclear cells from SLE patients, and functionally relevant to SLE. This study was conducted to test whether STAT4 is associated with SLE in a Japanese population also, to identify the risk haplotype, and to examine the potential genetic contribution of STAT1. To accomplish these aims, we carried out a comprehensive association analysis of 52 tag single nucleotide polymorphisms (SNPs) encompassing the STAT1-STAT4 region. Methods In the first screening, 52 tag SNPs were selected based on HapMap Phase II JPT (Japanese in Tokyo, Japan) data, and case-control association analysis was carried out on 105 Japanese female patients with SLE and 102 female controls. For associated SNPs, additional cases and controls were genotyped and association was analyzed using 308 SLE patients and 306 controls. Estimation of haplotype frequencies and an association study using the permutation test were performed with Haploview version 4.0 software. Population attributable risk percentage was estimated to compare the epidemiological significance of the risk genotype among populations. Results In the first screening, rs7574865, rs11889341, and rs10168266 in STAT4 were most significantly associated (P rs7574865) (P = 1.5 × 10-6). The association was stronger in subgroups of SLE with nephritis and anti-double-stranded DNA antibodies. Population attributable risk percentage was estimated to be higher in the Japanese population (40.2%) than in Americans of European descent (19.5%). Conclusions The same STAT4 risk allele is associated with SLE in Caucasian and Japanese populations. Evidence for a role of STAT1 in genetic susceptibility to SLE was not detected. The contribution of STAT4 for the genetic background of SLE may be greater in the

The ebola virus interferon antagonist VP24 directly binds STAT1 and has a novel, pyramidal fold.

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Zhang, Adrianna P P; Bornholdt, Zachary A; Liu, Tong; Abelson, Dafna M; Lee, David E; Li, Sheng; Woods, Virgil L; Saphire, Erica Ollmann

2012-02-01

Ebolaviruses cause hemorrhagic fever with up to 90% lethality and in fatal cases, are characterized by early suppression of the host innate immune system. One of the proteins likely responsible for this effect is VP24. VP24 is known to antagonize interferon signaling by binding host karyopherin α proteins, thereby preventing them from transporting the tyrosine-phosphorylated transcription factor STAT1 to the nucleus. Here, we report that VP24 binds STAT1 directly, suggesting that VP24 can suppress at least two distinct branches of the interferon pathway. Here, we also report the first crystal structures of VP24, derived from different species of ebolavirus that are pathogenic (Sudan) and nonpathogenic to humans (Reston). These structures reveal that VP24 has a novel, pyramidal fold. A site on a particular face of the pyramid exhibits reduced solvent exchange when in complex with STAT1. This site is above two highly conserved pockets in VP24 that contain key residues previously implicated in virulence. These crystal structures and accompanying biochemical analysis map differences between pathogenic and nonpathogenic viruses, offer templates for drug design, and provide the three-dimensional framework necessary for biological dissection of the many functions of VP24 in the virus life cycle.

The ebola virus interferon antagonist VP24 directly binds STAT1 and has a novel, pyramidal fold.

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Adrianna P P Zhang

2012-02-01

Full Text Available Ebolaviruses cause hemorrhagic fever with up to 90% lethality and in fatal cases, are characterized by early suppression of the host innate immune system. One of the proteins likely responsible for this effect is VP24. VP24 is known to antagonize interferon signaling by binding host karyopherin α proteins, thereby preventing them from transporting the tyrosine-phosphorylated transcription factor STAT1 to the nucleus. Here, we report that VP24 binds STAT1 directly, suggesting that VP24 can suppress at least two distinct branches of the interferon pathway. Here, we also report the first crystal structures of VP24, derived from different species of ebolavirus that are pathogenic (Sudan and nonpathogenic to humans (Reston. These structures reveal that VP24 has a novel, pyramidal fold. A site on a particular face of the pyramid exhibits reduced solvent exchange when in complex with STAT1. This site is above two highly conserved pockets in VP24 that contain key residues previously implicated in virulence. These crystal structures and accompanying biochemical analysis map differences between pathogenic and nonpathogenic viruses, offer templates for drug design, and provide the three-dimensional framework necessary for biological dissection of the many functions of VP24 in the virus life cycle.

d,l-Sulforaphane Induces ROS-Dependent Apoptosis in Human Gliomablastoma Cells by Inactivating STAT3 Signaling Pathway

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Ziwei Miao

2017-01-01

Full Text Available d,l-Sulforaphane (SFN, a synthetic analogue of broccoli-derived isomer l-SFN, exerts cytotoxic effects on multiple tumor cell types through different mechanisms and is more potent than the l-isomer at inhibiting cancer growth. However, the means by which SFN impairs glioblastoma (GBM cells remains poorly understood. In this study, we investigated the anti-cancer effect of SFN in GBM cells and determined the underlying molecular mechanisms. Cell viability assays, flow cytometry, immunofluorescence, and Western blot results revealed that SFN could induced apoptosis of GBM cells in a dose- and time-dependent manner, via up-regulation of caspase-3 and Bax, and down-regulation of Bcl-2. Mechanistically, SFN treatment led to increase the intracellular reactive oxygen species (ROS level in GBM cells. Meanwhile, SFN also suppressed both constitutive and IL-6-induced phosphorylation of STAT3, and the activation of upstream JAK2 and Src tyrosine kinases, dose- and time-dependently. Moreover, blockage of ROS production by using the ROS inhibitor N-acetyl-l-cysteine totally reversed SFN-mediated down-regulation of JAK2/Src-STAT3 signaling activation and the subsequent effects on apoptosis by blocking the induction of apoptosis-related genes in GBM cells. Taken together, our data suggests that SFN induces apoptosis in GBM cells via ROS-dependent inactivation of STAT3 phosphorylation. These findings motivate further evaluation of SFN as a cancer chemopreventive agent in GBM treatment.

A novel STAT inhibitor, OPB-31121, has a significant antitumor effect on leukemia with STAT-addictive oncokinases

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Hayakawa, F; Sugimoto, K; Harada, Y; Hashimoto, N; Ohi, N; Kurahashi, S; Naoe, T

2013-01-01

Signal transduction and activator of transcription (STAT) proteins are extracellular ligand-responsive transcription factors that mediate cell proliferation, apoptosis, differentiation, development and the immune response. Aberrant signals of STAT induce uncontrolled cell proliferation and apoptosis resistance and are strongly involved in cancer. STAT has been identified as a promising target for antitumor drugs, but to date most trials have not been successful. Here, we demonstrated that a novel STAT inhibitor, OPB-31121, strongly inhibited STAT3 and STAT5 phosphorylation without upstream kinase inhibition, and induced significant growth inhibition in various hematopoietic malignant cells. Investigation of various cell lines suggested that OPB-31121 is particularly effective against multiple myeloma, Burkitt lymphoma and leukemia harboring BCR–ABL, FLT3/ITD and JAK2 V617F, oncokinases with their oncogenicities dependent on STAT3/5. Using an immunodeficient mouse transplantation system, we showed the significant antitumor effect of OPB-31121 against primary human leukemia cells harboring these aberrant kinases and its safety for normal human cord blood cells. Finally, we demonstrated a model to overcome drug resistance to upstream kinase inhibitors with a STAT inhibitor. These results suggested that OPB-31121 is a promising antitumor drug. Phase I trials have been performed in Korea and Hong Kong, and a phase I/II trial is underway in Japan

Benzoxathiol derivative BOT-4-one suppresses L540 lymphoma cell survival and proliferation via inhibition of JAK3/STAT3 signaling.

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Kim, Byung Hak; Min, Yun Sook; Choi, Jung Sook; Baeg, Gyeong Hun; Kim, Young Soo; Shin, Jong Wook; Kim, Tae Yoon; Ye, Sang Kyu

2011-05-31

Persistently activated JAK/STAT3 signaling pathway plays a pivotal role in various human cancers including major carcinomas and hematologic tumors, and is implicated in cancer cell survival and proliferation. Therefore, inhibition of JAK/STAT3 signaling may be a clinical application in cancer therapy. Here, we report that 2-cyclohexylimino-6-methyl-6,7-dihydro-5H-benzo [1,3]oxathiol-4-one (BOT-4-one), a small molecule inhibitor of JAK/STAT3 signaling, induces apoptosis through inhibition of STAT3 activation. BOT-4-one suppressed cytokine (upd)-induced tyrosine phosphorylation and transcriptional activity of STAT92E, the sole Drosophila STAT homolog. Consequently, BOT-4-one significantly inhibited STAT3 tyrosine phosphorylation and expression of STAT3 downstream target gene SOCS3 in various human cancer cell lines, and its effect was more potent in JAK3-activated Hodgkin's lymphoma cell line than in JAK2-activated breast cancer and prostate cancer cell lines. In addition, BOT-4-one-treated Hodgkin's lymphoma cells showed decreased cell survival and proliferation by inducing apoptosis through down-regulation of STAT3 downstream target anti-apoptotic gene expression. These results suggest that BOT-4-one is a novel small molecule inhibitor of JAK3/STAT3 signaling and may have therapeutic potential in the treatment of human cancers harboring aberrant JAK3/STAT3 signaling, specifically Hodgkin's lymphoma.

Kobuvirus VP3 protein restricts the IFN-β-triggered signaling pathway by inhibiting STAT2-IRF9 and STAT2-STAT2 complex formation

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Peng, Qianqian; Lan, Xi; Wang, Chen [State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou 730046 (China); Ren, Yujie; Yue, Ningning [College of Life Sciences, Wuhan University, Wuhan 430072 (China); Wang, Junyong [State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou 730046 (China); Zhong, Bo [College of Life Sciences, Wuhan University, Wuhan 430072 (China); Medical Research Institute, School of Medicine, Wuhan University, Wuhan 430071 (China); Zhu, Qiyun, E-mail: zhuqiyun@caas.cn [State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou 730046 (China)

2017-07-15

Emerged porcine kobuvirus (PKV) has adversely affected the global swine industry since 2008, but the etiological biology of PKV is unclear. Screening PKV-encoded structural and non-structural proteins with a type I IFN-responsive luciferase reporter showed that PKV VP3 protein inhibited the IFN-β-triggered signaling pathway, resulting in the decrease of VSV-GFP replication. QPCR data showed that IFN-β downstream cytokine genes were suppressed without cell-type specificity as well. The results from biochemical experiments indicated that PKV VP3 associated with STAT2 and IRF9, and interfered with the formation of the STAT2-IRF9 and STAT2-STAT2 complex, impairing nuclear translocation of STAT2 and IRF9. Taken together, these data reveal a new mechanism for immune evasion of PKV. - Highlights: •PKV VP3 inhibits the IFN-β-triggered signaling pathway. •VP3 associates with STAT2 and IRF9. •VP3 blocks the STAT2-IRF9 nuclear translocation. •VP3 utilizes a novel strategy for innate immune evasion.

Active Components with Inhibitory Activities on IFN-γ/STAT1 and IL-6/STAT3 Signaling Pathways from Caulis Trachelospermi

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Xiao-Ting Liu

2014-08-01

Full Text Available Initial investigation for new active herbal extract with inhibiting activity on JAK/STAT signaling pathway revealed that the extract of Caulis Trachelospermi, which was separated by 80% alcohol extraction and subsequent HP-20 macroporous resin column chromatography, was founded to strongly inhibit IFN-γ-induced STAT1-responsive luciferase activity (IFN-γ/STAT1 with IC50 value of 2.43 μg/mL as well as inhibiting IL-6-induced STAT3-responsive luciferase activity (IL-6/STAT3 with IC50 value of 1.38 μg/mL. Subsequent study on its active components led to the isolation and identification of two new dibenzylbutyrolactone lignans named 4-demethyltraxillaside (1 and nortrachelogenin 4-O-β-d-glucopyranoside (2, together with six known compounds. The lignan compounds 1–4 together with other lignan compounds isolated in previous study were tested the activities on IFN-γ/STAT1 and IL-6/STAT3 pathways. The following result showed that the main components trachelogenin and arctigenin had corresponding activities on IFN-γ/STAT1 pathway with IC50 values of 3.14 μM and 9.46 μM as well as trachelogenin, arctigenin and matairesinol strongly inhibiting IL-6/STAT3 pathway with IC50 values of 3.63 μM, 6.47 μM and 2.92 μM, respectively.

Stabilization, not polymerization, of microtubules inhibits the nuclear translocation of STATs in adipocytes

International Nuclear Information System (INIS)

Gleason, Evanna L.; Hogan, Jessica C.; Stephens, Jacqueline M.

2004-01-01

Signal transducers and activators of transcriptions (STATs) are a family of latent transcription factors which are activated by a variety of growth factors and cytokines in many cell types. However, the mechanism by which these transcription factors translocate to the nucleus is poorly understood. The goal of this study was to determine the requirement of microfilaments and microtubules for cytokine induced STAT activation in cultured adipocytes. We used seven different actin-specific and microtubule-specific agents that are well-established effectors of these cytoskeletal networks. Our results clearly demonstrate that inhibition of microfilaments or the prevention of microtubule polymerization has no effect on the ability of STATs to be tyrosine phosphorylated or to translocate to the nucleus. However, we observed that paclitaxel, a microtubule stabilizer, resulted in a significant decrease in the nuclear translocation of STATs without affecting the cytosolic tyrosine phosphorylation of these transcription factors. In summary, our results demonstrate that the dynamic instability, but not the polymerization, of microtubules contributes to nuclear translocation of STAT proteins in adipocytes

STAT3 activation is associated with cerebrospinal fluid interleukin-10 (IL-10) in primary central nervous system diffuse large B cell lymphoma.

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Mizowaki, Takashi; Sasayama, Takashi; Tanaka, Kazuhiro; Mizukawa, Katsu; Takata, Kumi; Nakamizo, Satoshi; Tanaka, Hirotomo; Nagashima, Hiroaki; Nishihara, Masamitsu; Hirose, Takanori; Itoh, Tomoo; Kohmura, Eiji

2015-09-01

Signal transducers and activators of transcription 3 (STAT3) are activated by various cytokines and oncogenes; however, the activity and pathogenesis of STAT3 in diffuse large B cell lymphoma of the central nervous system have not been thoroughly elucidated. We investigated the phosphorylation levels of STAT3 in 40 specimens of primary central nervous system diffuse large B-cell lymphoma (PCNS DLBCL) and analyzed the association between phsopho-STAT3 (pSTAT3) expression and cerebrospinal fluid (CSF) concentration of interleukin-10 (IL-10) or IL-6. Immunohistochemistry and Western blot analysis revealed that most of the specimens in PCNS DLBCL expressed pSTST3 protein, and a strong phosphorylation levels of STAT3 was statistically associated with high CSF IL-10 levels, but not with CSF IL-6 levels. Next, we demonstrated that recombinant IL-10 and CSF containing IL-10 induced the phosphorylation of STAT3 in PCNS DLBCL cells. Furthermore, molecular subtype classified by Hans' algorithm was correlated with pSTAT3 expression levels and CSF IL-10 levels. These results suggest that the STAT3 activity is correlated with CSF IL-10 level, which is a useful marker for STAT3 activity in PCNS DLBCLs.

Inhibition of Stat3 signaling ameliorates atrophy of the soleus muscles in mice lacking the vitamin D receptor.

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Gopinath, Suchitra D

2017-01-25

Although skeletal muscle wasting has long been observed as a clinical outcome of impaired vitamin D signaling, precise molecular mechanisms that mediate the loss of muscle mass in the absence of vitamin D signaling are less clear. To determine the molecular consequences of vitamin D signaling, we analyzed the role of signal transducer and activator of transcription 3 (Stat3) signaling, a known contributor to various muscle wasting pathologies, in skeletal muscles. We isolated soleus (slow) and tibialis anterior (fast) muscles from mice lacking the vitamin D receptor (VDR -/- ) and used western blot analysis, quantitative RTPCR, and pharmacological intervention to analyze muscle atrophy in VDR -/- mice. We found that slow and fast subsets of muscles of the VDR -/- mice displayed elevated levels of phosphorylated Stat3 accompanied by an increase in Myostatin expression and signaling. Consequently, we observed reduced activity of mammalian target of rapamycin (mTOR) signaling components, ribosomal S6 kinase (p70S6K) and ribosomal S6 protein (rpS6), that regulate protein synthesis and cell size, respectively. Concomitantly, we observed an increase in atrophy regulators and a block in autophagic gene expression. An examination of the upstream regulation of Stat3 levels in VDR -/- muscles revealed an increase in IL-6 protein expression in the soleus, but not in the tibialis anterior muscles. To investigate the involvement of satellite cells (SCs) in atrophy in VDR -/- mice, we found that there was no significant deficit in SC numbers in VDR -/- muscles compared to the wild type. Unlike its expression within VDR -/- fibers, Myostatin levels in VDR -/- SCs from bulk muscles were similar to those of wild type. However, VDR -/- SCs induced to differentiate in culture displayed increased p-Stat3 signaling and Myostatin expression. Finally, VDR -/- mice injected with a Stat3 inhibitor displayed reduced Myostatin expression and function and restored active p70S6K and rpS6

Pantoprazole blocks the JAK2/STAT3 pathway to alleviate skeletal muscle wasting in cancer cachexia by inhibiting inflammatory response.

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Guo, Dunwei; Wang, Chaoyi; Wang, Qiang; Qiao, Zhongpeng; Tang, Hua

2017-06-13

Cancer cachexia is often present in patients with advanced malignant tumors, and the subsequent body weight reduction results in poor quality of life. However, there has been no progress in developing effective clinical therapeutic strategies for skeletal muscle wasting in cancer cachexia. Herein, we explored the functions of pantoprazole on cancer cachexia skeletal muscle wasting. The mouse colon adenocarcinoma cell line C26 was inoculated in the right forelimb of male BALB/C mice to establish a cancer cachexia model. The animals were treated with or without different concentrations of pantoprazole orally, and the body weight, tumor growth, spontaneous activity, and muscle functions were determined at various time points. Two weeks later, the levels of serum IL-6 and TNF-α, the mRNA levels of gastrocnemius JAK2 and STAT3, and the expression levels of p-JAK2, p-STAT3, Fbx32, and MuRF1 were examined with ELISA assay, qRT-PCR assay, and Western blotting, respectively. Further studies were performed to assess the levels of Fbx32 and MuRF1 expression and morphological changes. Pantoprazole can alleviate cancer cachexia-induced body weight reduction and inhibit skeletal muscle wasting in a dose-dependent manner. Our results indicated that pantoprazole treatment can decrease the levels of serum IL-6 and TNF-α (56.3% and 67.6%, respectively), and inhibit the activation of the JAK2/STAT3 signaling pathway. Moreover, the expression levels of MuRF1 and Fbx32 were also suppressed after pantoprazole treatment. Our findings suggested that pantoprazole can alleviate cancer cachexia skeletal muscle wasting by inhibiting the inflammatory response and blocking the JAK2/STAT3 or ubiquitin proteasome pathway.

The JAK inhibitor tofacitinib suppresses synovial JAK1-STAT signalling in rheumatoid arthritis

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Boyle, D L; Soma, K; Hodge, J; Kavanaugh, A; Mandel, D; Mease, P; Shurmur, R; Singhal, A K; Wei, N; Rosengren, S; Kaplan, I; Krishnaswami, S; Luo, Z; Bradley, J; Firestein, G S

2015-01-01

Objective Tofacitinib is an oral Janus kinase (JAK) inhibitor for the treatment of rheumatoid arthritis (RA). The pathways affected by tofacitinib and the effects on gene expression in situ are unknown. Therefore, tofacitinib effects on synovial pathobiology were investigated. Methods A randomised, double-blind, phase II serial synovial biopsy study (A3921073; NCT00976599) in patients with RA with an inadequate methotrexate response. Patients on background methotrexate received tofacitinib 10 mg twice daily or placebo for 28 days. Synovial biopsies were performed on Days -7 and 28 and analysed by immunoassay or quantitative PCR. Clinical response was determined by disease activity score and European League Against Rheumatism (EULAR) response on Day 28 in A3921073, and at Month 3 in a long-term extension study (A3921024; NCT00413699). Results Tofacitinib exposure led to EULAR moderate to good responses (11/14 patients), while placebo was ineffective (1/14 patients) on Day 28. Tofacitinib treatment significantly reduced synovial mRNA expression of matrix metalloproteinase (MMP)-1 and MMP-3 (pTofacitinib significantly decreased plasma CXCL10 (pTofacitinib reduces metalloproteinase and interferon-regulated gene expression in rheumatoid synovium, and clinical improvement correlates with reductions in STAT1 and STAT3 phosphorylation. JAK1-mediated interferon and interleukin-6 signalling likely play a key role in the synovial response. Trial registration number NCT00976599. PMID:25398374

Towards an easy access to Annexin-A5 protein binding block copolymer micelles

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Schmidt, Vanessa; Giacomelli, Cristiano; Brisson, Alain R.; Borsali, Redouane

2008-01-01

The formation of Annexin-A5 decorated (bio-functionalized) nanoparticles is of particular interest in micelle-mediated target drug delivery, in vivo magnetic resonance imaging, and controlled fabrication of biochips. This work describes an easy access to the synthesis and manipulation of block copolymer nano-objects exhibiting Annexin-A5 protein binding ability. Well-defined spherical micelles containing negatively charged phosphonic diacid groups - which are potential binding sites for Annexin-A5 proteins - at their hydrophilic periphery originate from the self-assembly of polystyrene-b-poly(2-phosphatethyl methacrylate-stat-2-hydroxyethyl methacrylate) (PS-b-P(PEMA-stat-HEMA)) amphiphilic macromolecules in aqueous media. PS-b-P(PEMA-stat-HEMA) can be prepared in a three-step phosphorylation/silylation/methanolysis procedure applied to PS-b-PHEMA precursors synthesized via Atom Transfer Radical Polymerization (ATRP). The herein discussed approach allows precise control over micellar dimensions and properties such as core radius (i.e., loading capacity), corona width, and density of phosphate groups at the micelle periphery

Novel multiplexed assay for identifying SH2 domain antagonists of STAT family proteins.

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Takakuma, Kazuyuki; Ogo, Naohisa; Uehara, Yutaka; Takahashi, Susumu; Miyoshi, Nao; Asai, Akira

2013-01-01

Some of the signal transducer and activator of transcription (STAT) family members are constitutively activated in a wide variety of human tumors. The activity of STAT depends on their Src homology 2 (SH2) domain-mediated binding to sequences containing phosphorylated tyrosine. Thus, antagonizing this binding is a feasible approach to inhibiting STAT activation. We have developed a novel multiplexed assay for STAT3- and STAT5b-SH2 binding, based on amplified luminescent proximity homogeneous assay (Alpha) technology. AlphaLISA and AlphaScreen beads were combined in a single-well assay, which allowed the binding of STAT3- and STAT5b-SH2 to phosphotyrosine peptides to be simultaneously monitored. Biotin-labeled recombinant human STAT proteins were obtained as N- and C-terminal deletion mutants. The spacer length of the DIG-labeled peptide, the reaction time, and the concentration of sodium chloride were optimized to establish a HTS system with Z' values of greater than 0.6 for both STAT3- and STAT5b-SH2 binding. We performed a HTS campaign for chemical libraries using this multiplexed assay and identified hit compounds. A 2-chloro-1,4-naphthalenedione derivative, Compound 1, preferentially inhibited STAT3-SH2 binding in vitro, and the nuclear translocation of STAT3 in HeLa cells. Initial structure activity relationship (SAR) studies using the multiplexed assay showed the 3-substituent effect on both the activity and selectivity of STAT3 and STAT5b inhibition. Therefore, this multiplexed assay is useful for not only searching for potential lead compounds but also obtaining SAR data for developing new STAT3/STAT5b inhibitors.

The dipeptide Pro-Asp promotes IGF-1 secretion and expression in hepatocytes by enhancing JAK2/STAT5 signaling pathway.

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Wang, Songbo; Wang, Guoqing; Zhang, Mengyuan; Zhuang, Lu; Wan, Xiaojuan; Xu, Jingren; Wang, Lina; Zhu, Xiaotong; Gao, Ping; Xi, Qianyun; Zhang, Yongliang; Shu, Gang; Jiang, Qingyan

2016-11-15

It has been implicated that IGF-1 secretion can be regulated by dietary protein. However, whether the dipeptides, one of digested products of dietary protein, have influence on IGF-1 secretion remain largely unknown. Our study aimed to investigate the effects of the dipeptide Pro-Asp on IGF-1 secretion and expression in hepatocytes and to explore the possible underlying mechanisms. Our findings demonstrated that Pro-Asp promoted the secretion and gene expression of IGF-1 in HepG2 cells and primary porcine hepatocytes. Meanwhile, Pro-Asp activated the ERK and Akt signaling pathways, downstream of IGF-1. In addition, Pro-Asp enhanced GH-mediated JAK2/STAT5 signaling pathway, while inhibition of JAK2/STAT5 blocked the promotive effect of Pro-Asp on IGF-1 secretion and expression. Moreover, acute injection of Pro-Asp stimulated IGF-1 expression and activated JAK2/STAT5 signaling pathway in mice liver. Together, these results suggested that the dipeptide Pro-Asp promoted IGF-1 secretion and expression in hepatocytes by enhancing GH-mediated JAK2/STAT5 signaling pathway. Copyright © 2016. Published by Elsevier Ireland Ltd.

STAT1 pathway mediates amplification of metastatic potential and resistance to therapy.

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Nikolai N Khodarev

Full Text Available BACKGROUND: Traditionally IFN/STAT1 signaling is connected with an anti-viral response and pro-apoptotic tumor-suppressor functions. Emerging functions of a constitutively activated IFN/STAT1 pathway suggest an association with an aggressive tumor phenotype. We hypothesized that tumor clones that constitutively overexpress this pathway are preferentially selected by the host microenvironment due to a resistance to STAT1-dependent cytotoxicity and demonstrate increased metastatic ability combined with increased resistance to genotoxic stress. METHODOLOGY/PRINCIPAL FINDINGS: Here we report that clones of B16F1 tumors grown in the lungs of syngeneic C57BL/6 mice demonstrate variable transcriptional levels of IFN/STAT1 pathway expression. Tumor cells that constitutively overexpress the IFN/STAT1 pathway (STAT1(H genotype are selected by the lung microenvironment. STAT1(H tumor cells also demonstrate resistance to IFN-gamma (IFNgamma, ionizing radiation (IR, and doxorubicin relative to parental B16F1 and low expressors of the IFN/STAT1 pathway (STAT1(L genotype. Stable knockdown of STAT1 reversed the aggressive phenotype and decreased both lung colonization and resistance to genotoxic stress. CONCLUSIONS: Our results identify a pathway activated by tumor-stromal interactions thereby selecting for pro-metastatic and therapy-resistant tumor clones. New therapies targeted against the IFN/STAT1 signaling pathway may provide an effective strategy to treat or sensitize aggressive tumor clones to conventional cancer therapies and potentially prevent distant organ colonization.

Bcl6 promotes osteoblastogenesis through Stat1 inhibition

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Fujie, Atsuhiro; Funayama, Atsushi; Miyauchi, Yoshiteru [Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582 (Japan); Sato, Yuiko [Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582 (Japan); Department of Musculoskeletal Reconstruction and Regeneration Surgery, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582 (Japan); Kobayashi, Tami [Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582 (Japan); Department of Integrated Bone Metabolism and Immunology, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582 (Japan); Kanagawa, Hiroya; Katsuyama, Eri; Hao, Wu; Tando, Toshimi; Watanabe, Ryuichi [Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582 (Japan); Morita, Mayu [Department of Dentistry and Oral Surgery, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582 (Japan); Miyamoto, Kana; Kanaji, Arihiko; Morioka, Hideo; Matsumoto, Morio; Toyama, Yoshiaki [Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582 (Japan); Miyamoto, Takeshi, E-mail: miyamoto@z5.keio.jp [Department of Orthopedic Surgery, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582 (Japan); Department of Integrated Bone Metabolism and Immunology, Keio University School of Medicine, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582 (Japan)

2015-02-13

Bone mass is tightly controlled by a balance between osteoclast and osteoblast activities. Although these cell types mature via different pathways, some factors reportedly regulate differentiation of both. Here, in a search for factors governing osteoblastogenesis but also expressed in osteoclasts to control both cell types by one molecule, we identified B cell lymphoma 6 (Bcl6) as one of those factors and show that it promotes osteoblast differentiation. Bcl6 was previously shown to negatively regulate osteoclastogenesis. We report that lack of Bcl6 results in significant inhibition of osteoblastogensis in vivo and in vitro and in defects in secondary ossification center formation in vivo. Signal transducer and activator of transcription 1 (Stat1) reportedly attenuates osteoblast differentiation by inhibiting nuclear translocation of runt-related transcription factor 2 (Runx2), which is essential for osteoblast differentiation. We found that lack of Bcl6 resulted in significant elevation of Stat1 mRNA and protein expression in osteoblasts and showed that Stat1 is a direct target of Bcl6 using a chromatin immune-precipitation assay. Mice lacking both Bcl6 and Stat1 (DKO) exhibited significant rescue of bone mass and osteoblastic parameters as well as partial rescue of secondary ossification center formation compared with Bcl6-deficient mice in vivo. Altered osteoblastogenesis in Bcl6-deficient cells was also restored in DKO in vitro. Thus, Bcl6 plays crucial roles in regulating both osteoblast activation and osteoclast inhibition. - Highlights: • Bcl6 is required for osteoblast differentiation. • Bcl6{sup −/−} mice exhibited altered osteoblastogenesis and reduced bone mass in vivo and in vitro. • We identified Stat1 as a direct target of Bcl6 in osteoblasts. • Bcl6 and Stat1 doubly deficient mice exhibited rescued bone phenotypes compared with Bcl6{sup −/−} mice.

RANKL downregulates cell surface CXCR6 expression through JAK2/STAT3 signaling pathway during osteoclastogenesis

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Li, Changhong; Zhao, Jinxia; Sun, Lin; Yao, Zhongqiang; Liu, Rui [Department of Rheumatology and Immunology, Peking University Third Hospital, Beijing 100191 (China); Huang, Jiansheng [Department of Pediatrics, Washington University School of Medicine, St. Louis, MO (United States); Liu, Xiangyuan, E-mail: liu-xiangyuan@263.net [Department of Rheumatology and Immunology, Peking University Third Hospital, Beijing 100191 (China)

2012-12-14

Highlights: Black-Right-Pointing-Pointer CXCR6 is down-regulated during RANKL-induced osteoclastogenesis in RAW264.7 cells. Black-Right-Pointing-Pointer CXCR6 reduction was nearly reversed by inhibition of JAK2/STAT3 signaling pathway. Black-Right-Pointing-Pointer CXCL16 alone does not positively regulate osteoclastogenesis. -- Abstract: The receptor activator of nuclear factor-{kappa}B ligand (RANKL), as a member of the tumor necrosis factor (TNF) family, plays an essential role in osteoclast differentiation and function. Chemokines and their receptors have recently been shown to play critical roles in osteoclastogenesis, however, whether CXCL16-CXCR6 plays role in RANKL-mediated osteoclastogenesis is unknown. In this study, we first reported that RANKL decreased CXCR6 in a dose-dependent manner, which may be through deactivation of Akt and STAT3 signaling induced by CXCL16. Interestingly, RANKL-mediated CXCR6 reduction may be associated to the activation of STAT3 by phosphorylation. When STAT3 activation was blocked by JAK2/STAT3 inhibitor AG490, RANKL failed to shut down CXCR6 expression during osteoclastogenesis. However, CXCL16 alone did not augment RANKL-mediated osteoclast differentiation and did not alter RANKL-receptor RANK mRNA expression. These results demonstrate that reduction of CXCL16-CXCR6 is critical in RANKL-mediated osteoclastogenesis, which is mainly through the activation of JAK2/STAT3 signaling. CXCL16-CXCR6 axis may become a novel target for the therapeutic intervention of bone resorbing diseases such as rheumatoid arthritis and osteoporosis.

Inhibition of STAT-3 results in radiosensitization of human squamous cell carcinoma

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Bonner, James A.; Trummell, Hoa Q.; Willey, Christopher D.; Plants, Brian A.; Raisch, Kevin P.

2009-01-01

Background: Signal transducer and activator of transcription-3 (STAT-3) is a downstream component of the Epidermal Growth Factor Receptor (EGFr) signaling process that may facilitate the resistance of tumor cells to conventional cancer treatments. Studies were performed to determine if inhibition of this downstream protein produces radiosensitization. Methods/Results: A431 cells (human squamous cell carcinoma cells with EGFr overexpression) were found to be sensitized to radiation after treatment with STAT-3 small interfering RNA (siRNA). Therefore, a short hairpin RNA (shRNA) against STAT-3 was designed and cloned into a pBABE vector system modified for shRNA expression. Following transfection, clone 2.1 was selected for further study as it showed a dramatic reduction of STAT-3 protein (and mRNA) when compared to A431 parental cells or a negative control shRNA cell line (transfected with STAT-3 shRNA with 2 base pairs mutated). A431 2.1 showed doubling times of 25-31 h as compared to 18-24 h for the parental cell line. The A431 shRNA knockdown STAT-3 cells A431 were more sensitive to radiation than A431 parental or negative STAT-3 control cells. Conclusion: A431 cells stably transfected with shRNA against STAT-3 resulted in enhanced radiosensitivity. Further work will be necessary to determine whether the inhibition of STAT-3 phosphorylation is a necessary step for the radiosensitization that is induced by the inhibition of EGFr.

Signal Transducer and Activator of Transcription 1 (STAT1) Knock-down Induces Apoptosis in Malignant Pleural Mesothelioma.

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Arzt, Lisa; Halbwedl, Iris; Gogg-Kamerer, Margit; Popper, Helmut H

2017-07-01

Malignant pleural mesothelioma (MPM) is the most common primary tumor of the pleura. Its incidence is still increasing in Europe and the prognosis remains poor. We investigated the oncogenic function of signal transducer and activator of transcription 1 (STAT1) in MPM in more detail. A miRNA profiling was performed on 52 MPM tissue samples. Upregulated miRNAs (targeting SOCS1/3) were knocked-down using miRNA inhibitors. mRNA expression levels of STAT1/3, SOCS1/3 were detected in MPM cell lines. STAT1 has been knocked-down using siRNA and qPCR was used to detect mRNA expression levels of all JAK/STAT family members and genes that regulate them. An immunohistochemical staining was performed to detect the expression of caspases. STAT1 was upregulated and STAT3 was downregulated, SOCS1/3 protein was not detected but it was possible to detect SOCS1/3 mRNA in MPM cell lines. The upregulated miRNAs were successfully knocked-down, however the expected effect on SOCS1 expression was not detected. STAT1 knock-down had different effects on STAT3/5 expression. Caspase 3a and 8 expression was found to be increased after STAT1 knock-down. The physiologic regulation of STAT1 via SOCS1 is completely lost in MPM and it does not seem that the miRNAs identified by now, do inhibit the expression of SOCS1. MPM cell lines compensate STAT1 knock-down by increasing the expression of STAT3 or STAT5a, two genes which are generally considered to be oncogenes. And much more important, STAT1 knock-down induces apoptosis in MPM cell lines and STAT1 might therefore be a target for therapeutic intervention.

Stabilization of Microtubule-Unbound Tau via Tau Phosphorylation at Ser262/356 by Par-1/MARK Contributes to Augmentation of AD-Related Phosphorylation and Aβ42-Induced Tau Toxicity.

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Kanae Ando

2016-03-01

Full Text Available Abnormal accumulation of the microtubule-interacting protein tau is associated with neurodegenerative diseases including Alzheimer's disease (AD. β-amyloid (Aβ lies upstream of abnormal tau behavior, including detachment from microtubules, phosphorylation at several disease-specific sites, and self-aggregation into toxic tau species in AD brains. To prevent the cascade of events leading to neurodegeneration in AD, it is essential to elucidate the mechanisms underlying the initial events of tau mismetabolism. Currently, however, these mechanisms remain unclear. In this study, using transgenic Drosophila co-expressing human tau and Aβ, we found that tau phosphorylation at AD-related Ser262/356 stabilized microtubule-unbound tau in the early phase of tau mismetabolism, leading to neurodegeneration. Aβ increased the level of tau detached from microtubules, independent of the phosphorylation status at GSK3-targeted SP/TP sites. Such mislocalized tau proteins, especially the less phosphorylated species, were stabilized by phosphorylation at Ser262/356 via PAR-1/MARK. Levels of Ser262 phosphorylation were increased by Aβ42, and blocking this stabilization of tau suppressed Aβ42-mediated augmentation of tau toxicity and an increase in the levels of tau phosphorylation at the SP/TP site Thr231, suggesting that this process may be involved in AD pathogenesis. In contrast to PAR-1/MARK, blocking tau phosphorylation at SP/TP sites by knockdown of Sgg/GSK3 did not reduce tau levels, suppress tau mislocalization to the cytosol, or diminish Aβ-mediated augmentation of tau toxicity. These results suggest that stabilization of microtubule-unbound tau by phosphorylation at Ser262/356 via the PAR-1/MARK may act in the initial steps of tau mismetabolism in AD pathogenesis, and that such tau species may represent a potential therapeutic target for AD.

Porcine bocavirus NP1 negatively regulates interferon signaling pathway by targeting the DNA-binding domain of IRF9

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Zhang, Ruoxi; Fang, Liurong; Wang, Dang; Cai, Kaimei; Zhang, Huan; Xie, Lilan; Li, Yi; Chen, Huanchun; Xiao, Shaobo

2015-01-01

To subvert host antiviral immune responses, many viruses have evolved countermeasures to inhibit IFN signaling pathway. Porcine bocavirus (PBoV), a newly identified porcine parvovirus, has received attention because it shows clinically high co-infection prevalence with other pathogens in post-weaning multisystemic wasting syndrome (PWMS) and diarrheic piglets. In this study, we screened the structural and non-structural proteins encoded by PBoV and found that the non-structural protein NP1 significantly suppressed IFN-stimulated response element (ISRE) activity and subsequent IFN-stimulated gene (ISG) expression. However, NP1 affected neither the activation and translocation of STAT1/STAT2, nor the formation of the heterotrimeric transcription factor complex ISGF3 (STAT1/STAT2/IRF9). Detailed analysis demonstrated that PBoV NP1 blocked the ISGF3 DNA-binding activity by combining with the DNA-binding domain (DBD) of IRF9. In summary, these results indicate that PBoV NP1 interferes with type I IFN signaling pathway by blocking DNA binding of ISGF3 to attenuate innate immune responses. - Highlights: • Porcine bocavirus (PBoV) NP1 interferes with the IFN α/β signaling pathway. • PBoV NP1 does not prevent STAT1/STAT2 phosphorylation and nuclear translocation. • PBoV NP1 inhibits the DNA-binding activity of ISGF3. • PBoV NP1 interacts with the DNA-binding domain of IRF9.

Porcine bocavirus NP1 negatively regulates interferon signaling pathway by targeting the DNA-binding domain of IRF9

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Zhang, Ruoxi [State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070 (China); The Cooperative Innovation Center for Sustainable Pig Production, Wuhan 430070 (China); Fang, Liurong, E-mail: fanglr@mail.hzau.edu.cn [State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070 (China); The Cooperative Innovation Center for Sustainable Pig Production, Wuhan 430070 (China); Wang, Dang; Cai, Kaimei; Zhang, Huan [State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070 (China); The Cooperative Innovation Center for Sustainable Pig Production, Wuhan 430070 (China); Xie, Lilan; Li, Yi [College of Life Science and Technology, Wuhan Institute of Bioengineering, Wuhan 430415 (China); Chen, Huanchun; Xiao, Shaobo [State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070 (China); The Cooperative Innovation Center for Sustainable Pig Production, Wuhan 430070 (China)

2015-11-15

To subvert host antiviral immune responses, many viruses have evolved countermeasures to inhibit IFN signaling pathway. Porcine bocavirus (PBoV), a newly identified porcine parvovirus, has received attention because it shows clinically high co-infection prevalence with other pathogens in post-weaning multisystemic wasting syndrome (PWMS) and diarrheic piglets. In this study, we screened the structural and non-structural proteins encoded by PBoV and found that the non-structural protein NP1 significantly suppressed IFN-stimulated response element (ISRE) activity and subsequent IFN-stimulated gene (ISG) expression. However, NP1 affected neither the activation and translocation of STAT1/STAT2, nor the formation of the heterotrimeric transcription factor complex ISGF3 (STAT1/STAT2/IRF9). Detailed analysis demonstrated that PBoV NP1 blocked the ISGF3 DNA-binding activity by combining with the DNA-binding domain (DBD) of IRF9. In summary, these results indicate that PBoV NP1 interferes with type I IFN signaling pathway by blocking DNA binding of ISGF3 to attenuate innate immune responses. - Highlights: • Porcine bocavirus (PBoV) NP1 interferes with the IFN α/β signaling pathway. • PBoV NP1 does not prevent STAT1/STAT2 phosphorylation and nuclear translocation. • PBoV NP1 inhibits the DNA-binding activity of ISGF3. • PBoV NP1 interacts with the DNA-binding domain of IRF9.

Hypoxia Downregulates MAPK/ERK but Not STAT3 Signaling in ROS-Dependent and HIF-1-Independent Manners in Mouse Embryonic Stem Cells

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Jan Kučera

2017-01-01

Full Text Available Hypoxia is involved in the regulation of stem cell fate, and hypoxia-inducible factor 1 (HIF-1 is the master regulator of hypoxic response. Here, we focus on the effect of hypoxia on intracellular signaling pathways responsible for mouse embryonic stem (ES cell maintenance. We employed wild-type and HIF-1α-deficient ES cells to investigate hypoxic response in the ERK, Akt, and STAT3 pathways. Cultivation in 1% O2 for 24 h resulted in the strong dephosphorylation of ERK and its upstream kinases and to a lesser extent of Akt in an HIF-1-independent manner, while STAT3 phosphorylation remained unaffected. Downregulation of ERK could not be mimicked either by pharmacologically induced hypoxia or by the overexpression. Dual-specificity phosphatases (DUSP 1, 5, and 6 are hypoxia-sensitive MAPK-specific phosphatases involved in ERK downregulation, and protein phosphatase 2A (PP2A regulates both ERK and Akt. However, combining multiple approaches, we revealed the limited significance of DUSPs and PP2A in the hypoxia-mediated attenuation of ERK signaling. Interestingly, we observed a decreased reactive oxygen species (ROS level in hypoxia and a similar phosphorylation pattern for ERK when the cells were supplemented with glutathione. Therefore, we suggest a potential role for the ROS-dependent attenuation of ERK signaling in hypoxia, without the involvement of HIF-1.

HARP preferentially co-purifies with RPA bound to DNA-PK and blocks RPA phosphorylation.

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Quan, Jinhua; Yusufzai, Timur

2014-05-01

The HepA-related protein (HARP/SMARCAL1) is an ATP-dependent annealing helicase that is capable of rewinding DNA structures that are stably unwound due to binding of the single-stranded DNA (ssDNA)-binding protein Replication Protein A (RPA). HARP has been implicated in maintaining genome integrity through its role in DNA replication and repair, two processes that generate RPA-coated ssDNA. In addition, mutations in HARP cause a rare disease known as Schimke immuno-osseous dysplasia. In this study, we purified HARP containing complexes with the goal of identifying the predominant factors that stably associate with HARP. We found that HARP preferentially interacts with RPA molecules that are bound to the DNA-dependent protein kinase (DNA-PK). We also found that RPA is phosphorylated by DNA-PK in vitro, while the RPA-HARP complexes are not. Our results suggest that, in addition to its annealing helicase activity, which eliminates the natural binding substrate for RPA, HARP blocks the phosphorylation of RPA by DNA-PK.

Antagonizing STAT3 dimerization with a rhodium(III) complex.

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Ma, Dik-Lung; Liu, Li-Juan; Leung, Ka-Ho; Chen, Yen-Ting; Zhong, Hai-Jing; Chan, Daniel Shiu-Hin; Wang, Hui-Min David; Leung, Chung-Hang

2014-08-25

Kinetically inert metal complexes have arisen as promising alternatives to existing platinum and ruthenium chemotherapeutics. Reported herein, to our knowledge, is the first example of a substitutionally inert, Group 9 organometallic compound as a direct inhibitor of signal transducer and activator of transcription 3 (STAT3) dimerization. From a series of cyclometalated rhodium(III) and iridium(III) complexes, a rhodium(III) complex emerged as a potent inhibitor of STAT3 that targeted the SH2 domain and inhibited STAT3 phosphorylation and dimerization. Significantly, the complex exhibited potent anti-tumor activities in an in vivo mouse xenograft model of melanoma. This study demonstrates that rhodium complexes may be developed as effective STAT3 inhibitors with potent anti-tumor activity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Up-regulation of intestinal epithelial cell derived IL-7 expression by keratinocyte growth factor through STAT1/IRF-1, IRF-2 pathway.

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Yu-Jiao Cai

Full Text Available BACKGROUND: Epithelial cells(EC-derived interleukin-7 (IL-7 plays a crucial role in control of development and homeostasis of neighboring intraepithelial lymphocytes (IEL, and keratinocyte growth factor (KGF exerts protective effects on intestinal epithelial cells and up-regulates EC-derived IL-7 expression through KGFR pathway. This study was to further investigate the molecular mechanism involved in the regulation of IL-7 expression by KGF in the intestine. METHODS: Intestinal epithelial cells (LoVo cells and adult C57BL/6J mice were treated with KGF. Epithelial cell proliferation was studied by flow cytometry for BrdU-incorporation and by immunohistochemistry for PCNA staining. Western blot was used to detect the changes of expression of P-Tyr-STAT1, STAT1, and IL-7 by inhibiting STAT1. Alterations of nuclear extracts and total proteins of IRF-1, IRF-2 and IL-7 following IRF-1 and IRF-2 RNA interference with KGF treatment were also measured with western blot. Moreover, IL-7 mRNA expressions were also detected by Real-time PCR and IL-7 protein level in culture supernatants was measured by enzyme linked immunosorbent assay(ELISA. RESULTS: KGF administration significantly increased LoVo cell proliferation and also increased intestinal wet weight, villus height, crypt depth and crypt cell proliferation in mice. KGF treatment led to increased levels of P-Tyr-STAT1, RAPA and AG490 both blocked P-Tyr-STAT1 and IL-7 expression in LoVo cells. IRF-1 and IRF-2 expression in vivo and in vitro were also up-regulated by KGF, and IL-7 expression was decreased after IRF-1 and IRF-2 expression was silenced by interfering RNA, respectively. CONCLUSION: KGF could up-regulate IL-7 expression through the STAT1/IRF-1, IRF-2 signaling pathway, which is a new insight in potential effects of KGF on the intestinal mucosal immune system.

Detection and Cellular Localization of Phospho-STAT2 in the Central Nervous System by Immunohistochemical Staining

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Khorooshi, Reza; Owens, Trevor

2013-01-01

Phosphorylation of signal transducers and activators of transcription (STATs) indicates their involvement in active signaling. Here we describe immunohistochemical staining procedures for detection and identification of the cellular localization of phospho-STAT2 in the central nervous system (CNS...

Essential role of Stat6 in IL-4 signalling.

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Takeda, K; Tanaka, T; Shi, W; Matsumoto, M; Minami, M; Kashiwamura, S; Nakanishi, K; Yoshida, N; Kishimoto, T; Akira, S

1996-04-18

Interleukin-4 (IL-4) is a pleiotropic lymphokine which plays an important role in the immune system. IL-4 activates two distinct signalling pathways through tyrosine phosphorylation of Stat6, a signal transducer and activator of transcription, and of a 170K protein called 4PS. To investigate the functional role of Stat6 in IL-4 signalling, we generated mice deficient in Stat6 by gene targeting. We report here that in the mutant mice, expression of CD23 and major histocompatibility complex (MHC) class II in resting B cells was not enhanced in response to IL-4. IL-4 induced B-cell proliferation costimulated by anti-IgM antibody was abolished. The T-cell proliferative response was also notably reduced. Furthermore, production of Th2 cytokines from T cells as well as IgE and IgG1 responses after nematode infection were profoundly reduced. These findings agreed with those obtained in IL-4 deficient mice or using antibodies to IL-4 and the IL-4 receptor. We conclude that Stat6 plays a central role in exerting IL-4 mediated biological responses.

A single tyrosine of the interleukin-9 (IL-9) receptor is required for STAT activation, antiapoptotic activity, and growth regulation by IL-9.

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Demoulin, J B; Uyttenhove, C; Van Roost, E; DeLestré, B; Donckers, D; Van Snick, J; Renauld, J C

1996-09-01

Interleukin-9 (IL-9), a T-cell-derived cytokine, interacts with a specific receptor associated with the IL-2 receptor gamma chain. In this report, we analyze the functional domains of the human IL-9 receptor transfected into mouse lymphoid cell lines. Three different functions were examined: growth stimulation in factor-dependent pro-B Ba/F3 cells, protection against dexamethasone-induced apoptosis, and Ly-6A2 induction in BW5147 lymphoma cells. The results indicated that a single tyrosine, at position 116 in the cytoplasmic domain, was required for all three activities. In addition, we observed that human IL-9 reduced the proliferation rate of transfected BW5147 cells, an effect also dependent on the same tyrosine. This amino acid was necessary for IL-9-mediated tyrosine phosphorylation of the receptor and for STAT activation but not for IRS-2/4PS activation or for JAK1 phosphorylation, which depended on a domain closer to the plasma membrane. We also showed that JAK1 was constitutively associated with the IL-9 receptor. Activated STAT complexes induced by IL-9 were found to contain STAT1, STAT3, and STAT5 transcription factors. Moreover, sequence homologies between human IL-9 receptor tyrosine 116 and tyrosines (of other receptors activating STAT3 and STAT5 were observed. Taken together, these data indicate that a single tyrosine of the IL-9 receptor, required for activation of three different STAT proteins, is necessary for distinct activities of this cytokine, including proliferative responses.

Arctigenin inhibits lipopolysaccharide-induced iNOS expression in RAW264.7 cells through suppressing JAK-STAT signal pathway.

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Kou, Xianjuan; Qi, Shimei; Dai, Wuxing; Luo, Lan; Yin, Zhimin

2011-08-01

Arctigenin has been demonstrated to have an anti-inflammatory function, but the precise mechanisms of its action remain to be fully defined. In the present study, we determined the effects of arctigenin on lipopolysaccharide (LPS)-induced production of proinflammatory mediators and the underlying mechanisms involved in RAW264.7 cells. Our results indicated that arctigenin exerted its anti-inflammatory effect by inhibiting ROS-dependent STAT signaling through its antioxidant activity. Arctigenin also significantly reduced the phosphorylation of STAT1 and STAT 3 as well as JAK2 in LPS-stimulated RAW264.7 cells. The inhibitions of STAT1 and STAT 3 by arctigenin prevented their translocation to the nucleus and consequently inhibited expression of iNOS, thereby suppressing the expression of inflammation-associated genes, such as IL-1β, IL-6 and MCP-1, whose promoters contain STAT-binding elements. However, COX-2 expression was slightly inhibited at higher drug concentrations (50 μM). Our data demonstrate that arctigenin inhibits iNOS expression via suppressing JAK-STAT signaling pathway in macrophages. Crown Copyright © 2011. Published by Elsevier B.V. All rights reserved.

Cofilin phosphorylation is elevated after F-actin disassembly induced by Rac1 depletion.

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Liu, Linna; Li, Jing; Zhang, Liwang; Zhang, Feng; Zhang, Rong; Chen, Xiang; Brakebusch, Cord; Wang, Zhipeng; Liu, Xinyou

2015-01-01

Cytoskeletal reorganization is essential to keratinocyte function. Rac1 regulates cytoskeletal reorganization through signaling pathways such as the cofilin cascade. Cofilin severs actin filaments after activation by dephosphorylation. Rac1 was knocked out in mouse keratinocytes and it was found that actin filaments disassembled. In the epidermis of mice in which Rac1 was knocked out only in keratinocytes, cofilin phosphorylation was aberrantly elevated, corresponding to repression of the phosphatase slingshot1 (SSH1). These effects were independent of the signaling pathways for p21-activated kinase/LIM kinase (Pak/LIMK), protein kinase C, or protein kinase D or generation of reactive oxygen species. Similarly, when actin polymerization was specifically inhibited or Rac1 was knocked down, cofilin phosphorylation was enhanced and SSH1 was repressed. Repression of SSH1 partially blocked actin depolymerization induced by Rac1 depletion. Therefore, aberrant cofilin phosphorylation that induces actin polymerization might be a consequence of actin disassembly induced by the absence of Rac1. © 2015 International Union of Biochemistry and Molecular Biology.

The Inflammatory Transcription Factors NFκB, STAT1 and STAT3 Drive Age-Associated Transcriptional Changes in the Human Kidney

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O’Brown, Zach K.; Van Nostrand, Eric L.; Higgins, John P.; Kim, Stuart K.

2015-01-01

Human kidney function declines with age, accompanied by stereotyped changes in gene expression and histopathology, but the mechanisms underlying these changes are largely unknown. To identify potential regulators of kidney aging, we compared age-associated transcriptional changes in the human kidney with genome-wide maps of transcription factor occupancy from ChIP-seq datasets in human cells. The strongest candidates were the inflammation-associated transcription factors NFκB, STAT1 and STAT3, the activities of which increase with age in epithelial compartments of the renal cortex. Stimulation of renal tubular epithelial cells with the inflammatory cytokines IL-6 (a STAT3 activator), IFNγ (a STAT1 activator), or TNFα (an NFκB activator) recapitulated age-associated gene expression changes. We show that common DNA variants in RELA and NFKB1, the two genes encoding subunits of the NFκB transcription factor, associate with kidney function and chronic kidney disease in gene association studies, providing the first evidence that genetic variation in NFκB contributes to renal aging phenotypes. Our results suggest that NFκB, STAT1 and STAT3 underlie transcriptional changes and chronic inflammation in the aging human kidney. PMID:26678048

Novel high-throughput screening system for identifying STAT3-SH2 antagonists

International Nuclear Information System (INIS)

Uehara, Yutaka; Mochizuki, Masato; Matsuno, Kenji; Haino, Takeharu; Asai, Akira

2009-01-01

Constitutive activation of the oncogenic transcription factor STAT3 frequently occurs in various human malignancies. STAT3 activation involves dimerization via intermolecular pTyr-SH2 interaction. Thus, antagonizing this interaction is a feasible approach to inhibit STAT3 activation for cancer therapy. In order to identify selective STAT3 inhibitors, we developed a biochemical HTS system based on AlphaScreen technology, which measures the abilities of test compounds to antagonize pTyr-SH2 interactions. We screened our chemical libraries using this system and identified 5,15-diphenylporphyrin (5,15-DPP) as a selective STAT3-SH2 antagonist. Selective inhibition of STAT3 nuclear translocation and DNA biding activity was observed in cells treated with 5,15-DPP. IL-6-dependent dimerization of STAT3, c-myc promoter binding and c-myc protein expression were all suppressed by 5,15-DPP, whereas no decrement in either expression or phosphorylation level of STAT3 was observed. Thus, the HTS assay system represented herein may be useful for identifying novel STAT3-SH2 antagonists.

CXCL12 suppresses cisplatin-induced apoptosis through activation of JAK2/STAT3 signaling in human non-small-cell lung cancer cells

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Wang M

2017-06-01

Full Text Available Meng Wang,1 Tie Lin,2 Yicun Wang,3 Song Gao,4 Zhaoyang Yang,1 Xuan Hong,1 Gongyan Chen1 1Department of Respiratory Medicine, Harbin Medical University Cancer Hospital, 2Department of Surgery, The First Affiliated Hospital of Harbin Medical University, Harbin, 3Jilin Provincial Key Laboratory on Molecular and Chemical Genetics, The Second Hospital of Jilin University, Changchun, 4Department of Clinical Oncology, Shengjing Hospital, China Medical University, Shenyang, People’s Republic of China Aims: Poor efficacy of chemotherapy drugs in non-small-cell lung cancer (NSCLC is the key reason for the failure of treatment, but the mechanism of this remains largely unknown. Stromal cell-derived factor 1-alpha (SDF-1α/CXCL12 is a small chemotactic cytokine protein that plays an important role in tumor progression. In this study, we investigated the anti-apoptotic mechanism of the CXCL12/CXCR4 axis in response to cisplatin, a commonly used chemotherapeutic drug, in human lung adenocarcinoma A549 cells.Methods: CXCL12 blocks cisplatin-induced apoptosis in A549, and the results were shown by propidium iodide/annexin V staining in vitro. The mechanism of CXCL12 stimulating phosphorylation of STAT3 through CXCR4/JAK2 was demonstrated by immunofluorescence and Western blotting. The expression of CXCL12 and p-STAT3 in clinical specimens was examined by immunohistochemistry.Results: CXCL12 significantly decreased the ratio of apoptotic cells and stimulation of phospho-signal transducer and activator of transcription (p-STAT-3 in a time-dependent manner through interaction with CXCR4. Among the signaling molecules downstream of CXCR4, the JAK2/STAT3 pathway plays a predominant role in the anti-apoptotic effect of CXCL12. Analysis of clinical specimens revealed that increased CXCL12 and p-STAT3 expression correlates with enhanced lung cancer progression.Conclusion: These data suggest that CXCR4 contributes to CXCL12-mediated anti-apoptosis by activating JAK2

Regulation of apoptosis by resveratrol through JAK/STAT and mitochondria mediated pathway in human epidermoid carcinoma A431 cells

International Nuclear Information System (INIS)

Madan, Esha; Prasad, Sahdeo; Roy, Preeti; George, Jasmine; Shukla, Yogeshwer

2008-01-01

Resveratrol (trans-3,4',5-trihydroxystilbene), a polyphenolic phytoalexin present mainly in grapes, red wine and berries, is known to possess strong chemopreventive and anticancer properties. Here, we demonstrated the anti-proliferative and apoptosis-inducing activities of resveratrol in human epidermoid carcinoma A431 cells. Resveratrol has cytotoxic effects through inhibiting cellular proliferation of A431 cells, which leads to the induction of apoptosis, as evident by an increase in the fraction of cells in the sub-G 1 phase of the cell cycle and Annexin-V binding of externalized phosphatidylserine. Results revealed that inhibition of proliferation is associated with regulation of the JAK/STAT pathway, where resveratrol prevents phosphorylation of JAK, thereby inhibiting STAT1 phosphorylation. Furthermore, resveratrol treatment actively stimulated reactive oxygen species (ROS) and mitochondrial membrane depolarization. Consequently, an imbalance in the Bax/Bcl-2 ratio triggered the caspase cascade and subsequent cleavage of PARP, thereby shifting the balance in favor of apoptosis. These observations indicate that resveratrol treatment inhibits JAK/STAT-mediated gene transcription and induce the mitochondrial cell death pathway.

Cofilin phosphorylation is elevated after F-actin disassembly induced by Rac1 depletion

DEFF Research Database (Denmark)

Liu, Linna; Li, Jing; Zhang, Liwang

2015-01-01

Cytoskeletal reorganization is essential to keratinocyte function. Rac1 regulates cytoskeletal reorganization through signaling pathways such as the cofilin cascade. Cofilin severs actin filaments after activation by dephosphorylation. Rac1 was knocked out in mouse keratinocytes and it was found...... that actin filaments disassembled. In the epidermis of mice in which Rac1 was knocked out only in keratinocytes, cofilin phosphorylation was aberrantly elevated, corresponding to repression of the phosphatase slingshot1 (SSH1). These effects were independent of the signaling pathways for p21-activated kinase....../LIM kinase (Pak/LIMK), protein kinase C, or protein kinase D or generation of reactive oxygen species. Similarly, when actin polymerization was specifically inhibited or Rac1 was knocked down, cofilin phosphorylation was enhanced and SSH1 was repressed. Repression of SSH1 partially blocked actin...

Reactive oxygen species contribute to arsenic-induced EZH2 phosphorylation in human bronchial epithelial cells and lung cancer cells

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Li, Lingzhi; Qiu, Ping; Chen, Bailing; Lu, Yongju; Wu, Kai; Thakur, Chitra; Chang, Qingshan; Sun, Jiaying; Chen, Fei, E-mail: fchen@wayne.edu

2014-05-01

Our previous studies suggested that arsenic is able to induce serine 21 phosphorylation of the EZH2 protein through activation of JNK, STAT3, and Akt signaling pathways in the bronchial epithelial cell line, BEAS-2B. In the present report, we further demonstrated that reactive oxygen species (ROS) were involved in the arsenic-induced protein kinase activation that leads to EZH2 phosphorylation. Several lines of evidence supported this notion. First, the pretreatment of the cells with N-acetyl-L-cysteine (NAC), a potent antioxidant, abolishes arsenic-induced EZH2 phosphorylation along with the inhibition of JNK, STAT3, and Akt. Second, H{sub 2}O{sub 2}, the most important form of ROS in the cells in response to extracellular stress signals, can induce phosphorylation of the EZH2 protein and the activation of JNK, STAT3, and Akt. By ectopic expression of the myc-tagged EZH2, we additionally identified direct interaction and phosphorylation of the EZH2 protein by Akt in response to arsenic and H{sub 2}O{sub 2}. Furthermore, both arsenic and H{sub 2}O{sub 2} were able to induce the translocation of ectopically expressed or endogenous EZH2 from nucleus to cytoplasm. In summary, the data presented in this report indicate that oxidative stress due to ROS generation plays an important role in the arsenic-induced EZH2 phosphorylation. - Highlights:: • Arsenic (As{sup 3+}) induces EZH phosphorylation. • JNK, STAT3, and Akt contribute to EZH2 phosphorylation. • Oxidative stress is involved in As{sup 3+}-induced EZH2 phosphorylation. • As{sup 3+} induces direct interaction of Akt and EZH2. • Phosphorylated EZH2 localized in cytoplasm.

Identification of amino-acid residues in the V protein of peste des petits ruminants essential for interference and suppression of STAT-mediated interferon signaling

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Ma, Xusheng, E-mail: maxushengtt@163.com [State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences (CAAS), Lanzhou 730030 (China); Yang, Xing [State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences (CAAS), Lanzhou 730030 (China); Nian, Xiaofeng [Institute of Pathogen Biology and Immunology, Hebei North University, Zhangjiakou 07500 (China); Zhang, Zhidong; Dou, Yongxi [State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences (CAAS), Lanzhou 730030 (China); Zhang, Xuehu [Gansu Agricultural University, Lanzhou (China); Luo, Xuenong; Su, Junhong; Zhu, Qiyun [State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences (CAAS), Lanzhou 730030 (China); Cai, Xuepeng, E-mail: caixp@vip.163.com [State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences (CAAS), Lanzhou 730030 (China)

2015-09-15

Peste des petits ruminants virus (PPRV) causes a fatal disease in small ruminants. V protein of PPRV plays a pivotal role in interfering with host innate immunity by blocking IFNs signaling through interacting with STAT1 and STAT2. In the present study, the results demonstrated that PPRV V protein blocks IFN actions in a dose dependent manner and restrains the translocation of STAT1/2 proteins. We speculate that the translocation inhibition might be caused by the interfering of the downstream of STAT protein. Mutagenesis defines that Cys cluster and Trp motif of PPRV V protein are essential for STAT-mediated IFN signaling. These findings give a new sight for the further studies to understand the delicate mechanism of PPRV to escape the IFN signaling. - Highlights: • PPRV V protein inhibits type I IFN production and blocks its activation. • PPRV V protein negatively regulates activation of ISRE and GAS promoter. • PPRV V protein inhibits nuclear translocation of STAT protein by non-degradation. • PNT and VCT domain of PPRV V protein inhibit IFN transduction. • PPRV V protein binds with STAT protein via some conserved motifs.

Upregulated STAT3 and RhoA signaling in colorectal cancer (CRC) regulate the invasion and migration of CRC cells.

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Zhang, G-Y; Yang, W-H; Chen, Z

2016-05-01

We aimed to reveal the expression and activation of signal transducers and activators of transcription 3 (STAT3) and RhoA/Rho-associated coiled-coil forming kinase 1 (ROCK1) signaling in CRC tissues, and to investigate the regulatory role of STAT3 and RhoA signaling in the invasion and migration of colorectal cancer cells. We examined the expression of STAT3, RhoA and ROCK1 in CRC tissues with real-time PCR and Western blotting methods. And then we examined the interaction between STAT3 and RhoA/ROCK1 signaling in CRC HT-29 cells with gain-of-function and loss-of-function strategies. In addition, we determined the regulation by STAT3 and RhoA/ROCK1 on the invasion and migration of CRC HT-29 cells. Our study demonstrated a significant upregulation of RhoA and ROCK1 expression and STAT3-Y705 phosphorylation in 32 CRC specimens, compared to the 17 normal CRC tissues. Further study demonstrated there was a coordination between STAT3 and RhoA/Rock signaling in the HT-29 cells. Moreover, STAT3 knockdown or RhoA knockdown significantly repressed the migration and invasion in HT-29 cells and vice versa. STAT3 and RhoA signaling regulate the invasion and migration of CRC cells, implying the orchestrated and oncogenic roles of STAT3 and RhoA/ROCK1 signaling in CRC.

Γ-Ionizing radiation activated EGFR-p38/ERK-STAT3/CREB-1-EMT pathway for promotion of the migration/invasion of lung cancer cell and its inhibition by podophyllotoxin acetate

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Cho, Jeong Hyun; Um, Hong Duck; Park, Jong Kuk [Korea Institute of Radiological and Medical Sciences, Seoul (Korea, Republic of)

2016-05-15

In this study, we sought to identify the intracellular machinery responsible for IR induced cancer invasion/migration. We report that IR activates the EGFR - p38/ERK - CREB-1/STAT3 pathway, which triggers EMT and increases invasion/migration of lung cancer. Moreover, we show that podophyllotoxin acetate (PA) inhibits IR-induced invasion/migration at least partly by blocking EGFR - p38/ERK - STAT3/ CREB-1signaling and thereby suppressing EMT. Our results revealed that IR increased the invasion/migration of A549 cells, and this effect was decreased by 10 nM PA treatment. PA also inhibited the expressions/activities of matrix metalloprotase (MMP) -2, MMP-9, and vimentin, suggesting that PA could block the IR-induced epithelial-mesenchymal transition (EMT). The IR induced increases in invasion/migration were associated with the activation of EGFR-AKT, and PA inhibited this effect. P38 and p44/42 ERK were also involved in IR induced invasion/migration, and combined treatments with PA plus inhibitors of each MAPK synergistically blocked this invasion/migration. In terms of transcription factors (TFs), IR-induced increases in cyclic AMP response element-binding protein-1 (CREB-1) and signal transducer and activator of transcription 3 (STAT3) increased invasion/migration and EMT. PA also inhibited these transcription factors and then blocked IR-induced invasion/migration.

Γ-Ionizing radiation activated EGFR-p38/ERK-STAT3/CREB-1-EMT pathway for promotion of the migration/invasion of lung cancer cell and its inhibition by podophyllotoxin acetate

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Cho, Jeong Hyun; Um, Hong Duck; Park, Jong Kuk

2016-01-01

In this study, we sought to identify the intracellular machinery responsible for IR induced cancer invasion/migration. We report that IR activates the EGFR - p38/ERK - CREB-1/STAT3 pathway, which triggers EMT and increases invasion/migration of lung cancer. Moreover, we show that podophyllotoxin acetate (PA) inhibits IR-induced invasion/migration at least partly by blocking EGFR - p38/ERK - STAT3/ CREB-1signaling and thereby suppressing EMT. Our results revealed that IR increased the invasion/migration of A549 cells, and this effect was decreased by 10 nM PA treatment. PA also inhibited the expressions/activities of matrix metalloprotase (MMP) -2, MMP-9, and vimentin, suggesting that PA could block the IR-induced epithelial-mesenchymal transition (EMT). The IR induced increases in invasion/migration were associated with the activation of EGFR-AKT, and PA inhibited this effect. P38 and p44/42 ERK were also involved in IR induced invasion/migration, and combined treatments with PA plus inhibitors of each MAPK synergistically blocked this invasion/migration. In terms of transcription factors (TFs), IR-induced increases in cyclic AMP response element-binding protein-1 (CREB-1) and signal transducer and activator of transcription 3 (STAT3) increased invasion/migration and EMT. PA also inhibited these transcription factors and then blocked IR-induced invasion/migration

Oncostatin M promotes STAT3 activation, VEGF production, and invasion in osteosarcoma cell lines

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Fossey, Stacey L; Bear, Misty D; Kisseberth, William C; Pennell, Michael; London, Cheryl A

2011-01-01

We have previously demonstrated that both canine and human OSA cell lines, as well as 8 fresh canine OSA tumor samples, exhibit constitutive phosphorylation of STAT3, and that this correlates with enhanced expression of matrix metalloproteinase-2 (MMP2). While multiple signal transduction pathways can result in phosphorylation of STAT3, stimulation of the cytokine receptor gp130 through either IL-6 or Oncostatin M (OSM) is the most common mechanism through which STAT3 is activated. The purpose of this study was to evaluate the role of IL-6 and OSM stimulation on both canine and human OSA cell lines to begin to determine the role of these cytokines in the biology of OSA. RT-PCR and Western blotting were used to interrogate the consequences of OSM and IL-6 stimulation of OSA cell lines. OSA cells were stimulated with OSM and/or hepatocyte growth factor (HGF) and the effects on MMP2 activity (gel zymography), proliferation (CyQUANT), invasion (Matrigel transwell assay), and VEGF production (Western blotting, ELISA) were assessed. The small molecule STAT3 inhibitor LLL3 was used to investigate the impact of STAT3 inhibition following OSM stimulation of OSA cells. Our data demonstrate that the OSM receptor (OSMR), but not IL-6 or its receptor, is expressed by all human and canine OSA cell lines and canine OSA tumor samples; additionally, OSM expression was noted in all tumor samples. Treatment of OSA cell lines with OSM induced phosphorylation of STAT3, Src, and JAK2. OSM stimulation also resulted in a dose dependent increase in MMP2 activity and VEGF expression that was markedly reduced following treatment with the small molecule STAT3 inhibitor LLL3. Lastly, OSM stimulation of OSA cell lines enhanced invasion through Matrigel, particularly in the presence of rhHGF. In contrast, both OSM and HGF stimulation of OSA cell lines did not alter their proliferative capacity. These data indicate OSM stimulation of human and canine OSA cells induces STAT3 activation, thereby

Oncostatin M promotes STAT3 activation, VEGF production, and invasion in osteosarcoma cell lines

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Kisseberth William C

2011-04-01

Full Text Available Abstract Background We have previously demonstrated that both canine and human OSA cell lines, as well as 8 fresh canine OSA tumor samples, exhibit constitutive phosphorylation of STAT3, and that this correlates with enhanced expression of matrix metalloproteinase-2 (MMP2. While multiple signal transduction pathways can result in phosphorylation of STAT3, stimulation of the cytokine receptor gp130 through either IL-6 or Oncostatin M (OSM is the most common mechanism through which STAT3 is activated. The purpose of this study was to evaluate the role of IL-6 and OSM stimulation on both canine and human OSA cell lines to begin to determine the role of these cytokines in the biology of OSA. Methods RT-PCR and Western blotting were used to interrogate the consequences of OSM and IL-6 stimulation of OSA cell lines. OSA cells were stimulated with OSM and/or hepatocyte growth factor (HGF and the effects on MMP2 activity (gel zymography, proliferation (CyQUANT, invasion (Matrigel transwell assay, and VEGF production (Western blotting, ELISA were assessed. The small molecule STAT3 inhibitor LLL3 was used to investigate the impact of STAT3 inhibition following OSM stimulation of OSA cells. Results Our data demonstrate that the OSM receptor (OSMR, but not IL-6 or its receptor, is expressed by all human and canine OSA cell lines and canine OSA tumor samples; additionally, OSM expression was noted in all tumor samples. Treatment of OSA cell lines with OSM induced phosphorylation of STAT3, Src, and JAK2. OSM stimulation also resulted in a dose dependent increase in MMP2 activity and VEGF expression that was markedly reduced following treatment with the small molecule STAT3 inhibitor LLL3. Lastly, OSM stimulation of OSA cell lines enhanced invasion through Matrigel, particularly in the presence of rhHGF. In contrast, both OSM and HGF stimulation of OSA cell lines did not alter their proliferative capacity. Conclusions These data indicate OSM stimulation of

The Chemopreventive Phytochemical Moringin Isolated from Moringa oleifera Seeds Inhibits JAK/STAT Signaling.

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Carina Michl

Full Text Available Sulforaphane (SFN and moringin (GMG-ITC are edible isothiocyanates present as glucosinolate precursors in cruciferous vegetables and in the plant Moringa oleifera respectively, and recognized for their chemopreventive and medicinal properties. In contrast to the well-studied SFN, little is known about the molecular pathways targeted by GMG-ITC. We investigated the ability of GMG-ITC to inhibit essential signaling pathways that are frequently upregulated in cancer and immune disorders, such as JAK/STAT and NF-κB. We report for the first time that, similarly to SFN, GMG-ITC in the nanomolar range suppresses IL-3-induced expression of STAT5 target genes. GMG-ITC, like SFN, does not inhibit STAT5 phosphorylation, suggesting a downstream inhibitory event. Interestingly, treatment with GMG-ITC or SFN had a limited inhibitory effect on IFNα-induced STAT1 and STAT2 activity, indicating that both isothiocyanates differentially target JAK/STAT signaling pathways. Furthermore, we showed that GMG-ITC in the micromolar range is a more potent inhibitor of TNF-induced NF-κB activity than SFN. Finally, using a cellular system mimicking constitutive active STAT5-induced cell transformation, we demonstrated that SFN can reverse the survival and growth advantage mediated by oncogenic STAT5 and triggers cell death, therefore providing experimental evidence of a cancer chemopreventive activity of SFN. This work thus identified STAT5, and to a lesser extent STAT1/STAT2, as novel targets of moringin. It also contributes to a better understanding of the biological activities of the dietary isothiocyanates GMG-ITC and SFN and further supports their apparent beneficial role in the prevention of chronic illnesses such as cancer, inflammatory diseases and immune disorders.

Interactions between Th1 cells and Tregs affect regulation of hepatic fibrosis in biliary atresia through the IFN-γ/STAT1 pathway.

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Wen, Jie; Zhou, Ying; Wang, Jun; Chen, Jie; Yan, Wenbo; Wu, Jin; Yan, Junkai; Zhou, Kejun; Xiao, Yongtao; Wang, Yang; Xia, Qiang; Cai, Wei

2017-06-01

Regulatory T cells (Tregs) and CD4 + T helper (Th) cells have important roles in bile duct injury of biliary atresia (BA). However, their impacts on liver fibrosis are undefined. Between 2013 and 2016, 146 patients with various stages of BA were enrolled in this study. Peripheral blood, liver biopsy and lymph node samples were collected. Flow cytometry, magnetic cell sorting and immunostaining were used to characterize lymphocytes from BA patients. Deficiency of Tregs was observed along with increased Th1, Th2 and Th17 frequencies in the peripheral blood and livers of BA patients. The levels of peripheral and intrahepatic Th1 cells positively correlated with the stage of liver fibrosis. Furthermore, Th1 cells were located in close proximity to activated hepatic stellate cells (HSCs) and areas of fibrosis in BA livers. In culture, Th1 cells accelerated the proliferation and secretion of profibrogenic markers of HSCs through the IFN-γ/STAT1 pathway. Of note, Tregs blocked the Th1-stimulated effects on HSCs by inhibiting Th1-induced activation of STAT1. Consistent with the results of in vitro study, intrahepatic IFN-γ/STAT1 levels increased in relation to the severity of liver fibrosis in BA patients, and the altered balance between MMP2 and TIMP1 expressions in livers may contribute to increased deposition of extracellular matrix and fibrosis. Finally, to identify the effects of Th1 cells on Tregs, we demonstrated that Th1 cells upregulated the proportion of aTreg cells by secreting IFN-γ cytokine. Thus, aberrant Th1 immune responses in BA promote the proliferation and secretion of HSCs through the IFN-γ/STAT1 pathway. The regulation of HSCs by the interactions between Tregs and Th1 cells might be part of the mechanism underlying progressive liver fibrosis and may be a suitable target for therapy.

Novel Serine 176 Phosphorylation of YBX1 Activates NF-κB in Colon Cancer.

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Martin, Matthew; Hua, Laiqing; Wang, Benlian; Wei, Han; Prabhu, Lakshmi; Hartley, Antja-Voy; Jiang, Guanglong; Liu, Yunlong; Lu, Tao

2017-02-24

Y box protein 1 (YBX1) is a well known oncoprotein that has tumor-promoting functions. YBX1 is widely considered to be an attractive therapeutic target in cancer. To develop novel therapeutics to target YBX1, it is of great importance to understand how YBX1 is finely regulated in cancer. Previously, we have shown that YBX1 could function as a tumor promoter through phosphorylation of its Ser-165 residue, leading to the activation of the NF-κB signaling pathway (1). In this study, using mass spectrometry analysis, we discovered a distinct phosphorylation site, Ser-176, on YBX1. Overexpression of the YBX1-S176A (serine-to-alanine) mutant in either HEK293 cells or colon cancer HT29 cells showed dramatically reduced NF-κB-activating ability compared with that of WT-YBX1, confirming that Ser-176 phosphorylation is critical for the activation of NF-κB by YBX1. Importantly, the mutant of Ser-176 and the previously reported Ser-165 sites regulate distinct groups of NF-κB target genes, suggesting the unique and irreplaceable function of each of these two phosphorylated serine residues. Our important findings could provide a novel cancer therapy strategy by blocking either Ser-176 or Ser-165 phosphorylation or both of YBX1 in colon cancer. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

CD45-mediated signaling pathway is involved in Rhizoctonia bataticola lectin (RBL)-induced proliferation and Th1/Th2 cytokine secretion in human PBMC

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Pujari, Radha; Eligar, Sachin M.; Kumar, Natesh; Nagre, Nagaraja N.; Inamdar, Shashikala R.; Swamy, Bale M.; Shastry, Padma

2012-01-01

Highlights: ► RBL, a potent mitogenic and complex N-glycan specific lectin binds to CD45 on PBMC. ► RBL triggers CD45-mediated signaling involved in activation of p38MAPK and STAT-5. ► Inhibition of CD45 PTPase signaling blocks RBL-induced ZAP70 phosphorylation. ► RBL-CD45 mediated signaling is crucial for RBL-induced immunodulatory activities. -- Abstract: We earlier reported the mitogenic and immunostimulatory activities of Rhizoctonia bataticola lectin (RBL), purified from phytopathogenic fungus R. bataticola in human PBMC. The lectin demonstrates specificity towards glycoproteins containing complex N-glycans. Since CD45-protein tyrosine phosphatase that abundantly expresses N-glycans is important in T-cell signaling, the study aimed to investigate the involvement of CD45 in the immunomodulatory activities of RBL. Flowcytometry and confocal microscopy studies revealed that RBL exhibited binding to PBMC and colocalized with CD45. The binding was comparable in cells expressing different CD45 isoforms-RA, -RB and -RO. CD45 blocking antibody reduced the binding and proliferation of PBMC induced by RBL. CD45-PTPase inhibitor dephostatin inhibited RBL–induced proliferation, expression of CD25 and pZAP-70. RBL-induced secretion of Th1/Th2 cytokines were significantly inhibited in presence of dephostatin. Also, dephostatin blocked phosphorylation of p38MAPK and STAT-5 that was crucial for the biological functions of RBL. The study demonstrates the involvement of CD45-mediated signaling in RBL-induced PBMC proliferation and Th1/Th2 cytokine secretion through activation of p38MAPK and STAT-5.

Hierarchy of protein tyrosine kinases in interleukin-2 (IL-2) signaling: activation of syk depends on Jak3; however, neither Syk nor Lck is required for IL-2-mediated STAT activation.

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Zhou, Y J; Magnuson, K S; Cheng, T P; Gadina, M; Frucht, D M; Galon, J; Candotti, F; Geahlen, R L; Changelian, P S; O'Shea, J J

2000-06-01

Interleukin-2 (IL-2) activates several different families of tyrosine kinases, but precisely how these kinases interact is not completely understood. We therefore investigated the functional relationships among Jak3, Lck, and Syk in IL-2 signaling. We first observed that in the absence of Jak3, both Lck and Syk had the capacity to phosphorylate Stat3 and Stat5a. However, neither supported IL-2-induced STAT activation, nor did dominant negative alleles of these kinases inhibit. Moreover, pharmacological abrogation of Lck activity did not inhibit IL-2-mediated phosphorylation of Jak3 and Stat5a. Importantly, ligand-dependent Syk activation was dependent on the presence of catalytically active Jak3, whereas Lck activation was not. Interestingly, Syk functioned as a direct substrate of Jak1 but not Jak3. Additionally, Jak3 phosphorylated Jak1, whereas the reverse was not the case. Taken together, our data support a model in which Lck functions in parallel with Jak3, while Syk functions as a downstream element of Jaks in IL-2 signaling. Jak3 may regulate Syk catalytic activity indirectly via Jak1. However, IL-2-mediated Jak3/Stat activation is not dependent on Lck or Syk. While the essential roles of Jak1 and Jak3 in signaling by gammac-utilizing cytokines are clear, it will be important to dissect the exact contributions of Lck and Syk in mediating the effects of IL-2 and related cytokines.

Molecular cloning and expression analysis of the STAT1 gene from olive flounder, Paralichthys olivaceus

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Chung Jongkyeong

2008-06-01

Full Text Available Abstract Background Signal transducer and activator of transcription 1 (STAT1 is a critical component of interferon (IFN-alpha/beta and IFN-gamma signaling. Although seven isoforms of STAT proteins have been reported from mammals, limited information is available for the STAT genes in fish. We isolated complementary DNA with high similarity to mammalian STAT1 from the olive flounder, Paralichthys olivaceus. Results A DNA fragment containing the conserved SH2 domain was amplified by RT-PCR using degenerate primers designed based on the highly conserved sequences in the SH2 domains of the zebrafish and mammalian STAT1. The complete cDNA sequence was obtained by 5' and 3' RACE. The flounder STAT1 transcript consisted of 2,909 bp that encoded a polypeptide of 749 amino acids. The overall similarity between flounder STAT1 and other STATs was very high, with the highest amino acid sequence identity to snakehead (89%. Phylogenetic analyses reveal that flounder STAT1 is in the same monophyletic group with snakehead STAT1. Quantitative real time RT-PCR and in situ hybridization revealed that STAT1 was expressed in almost all examined organs and tissues, with high expression in gill, spleen, kidney, and heart. The accumulation of STAT1 mRNA in different developmental stages, as determined by real time RT-PCR, increased with development. Conclusion Recent cloning of various cytokine genes and the STAT1 gene of olive flounder here suggest that fish also use the highly specialized JAK-STAT pathway for cytokine signaling. Identification of other STAT genes will elucidate in detail the signal transduction system in this fish.

Stat5 signaling specifies basal versus stress erythropoietic responses through distinct binary and graded dynamic modalities.

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Ermelinda Porpiglia

2012-08-01

Full Text Available Erythropoietin (Epo-induced Stat5 phosphorylation (p-Stat5 is essential for both basal erythropoiesis and for its acceleration during hypoxic stress. A key challenge lies in understanding how Stat5 signaling elicits distinct functions during basal and stress erythropoiesis. Here we asked whether these distinct functions might be specified by the dynamic behavior of the Stat5 signal. We used flow cytometry to analyze Stat5 phosphorylation dynamics in primary erythropoietic tissue in vivo and in vitro, identifying two signaling modalities. In later (basophilic erythroblasts, Epo stimulation triggers a low intensity but decisive, binary (digital p-Stat5 signal. In early erythroblasts the binary signal is superseded by a high-intensity graded (analog p-Stat5 response. We elucidated the biological functions of binary and graded Stat5 signaling using the EpoR-HM mice, which express a "knocked-in" EpoR mutant lacking cytoplasmic phosphotyrosines. Strikingly, EpoR-HM mice are restricted to the binary signaling mode, which rescues these mice from fatal perinatal anemia by promoting binary survival decisions in erythroblasts. However, the absence of the graded p-Stat5 response in the EpoR-HM mice prevents them from accelerating red cell production in response to stress, including a failure to upregulate the transferrin receptor, which we show is a novel stress target. We found that Stat5 protein levels decline with erythroblast differentiation, governing the transition from high-intensity graded signaling in early erythroblasts to low-intensity binary signaling in later erythroblasts. Thus, using exogenous Stat5, we converted later erythroblasts into high-intensity graded signal transducers capable of eliciting a downstream stress response. Unlike the Stat5 protein, EpoR expression in erythroblasts does not limit the Stat5 signaling response, a non-Michaelian paradigm with therapeutic implications in myeloproliferative disease. Our findings show how the

HSP90 is essential for Jak-STAT signaling in classical Hodgkin lymphoma cells

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Kube Dieter

2009-07-01

Full Text Available Abstract In classical Hodgkin lymphoma (cHL chemotherapeutic regimens are associated with stagnant rates of secondary malignancies requiring the development of new therapeutic strategies. We and others have shown that permanently activated Signal Transducer and Activator of Transcription (STAT molecules are essential for cHL cells. Recently an overexpression of heat-shock protein 90 (HSP90 in cHL cells has been shown and inhibition of HSP90 seems to affect cHL cell survival. Here we analysed the effects of HSP90 inhibition by geldanamycin derivative 17-AAG or RNA interference (RNAi on aberrant Jak-STAT signaling in cHL cells. Treatment of cHL cell lines with 17-AAG led to reduced cell proliferation and a complete inhibition of STAT1, -3, -5 and -6 tyrosine phosphorylation probably as a result of reduced protein expression of Janus kinases (Jaks. RNAi-mediated inhibition of HSP90 showed similar effects on Jak-STAT signaling in L428 cHL cells. These results suggest a central role of HSP90 in permanently activated Jak-STAT signaling in cHL cells. Therapeutics targeting HSP90 may be a promising strategy in cHL and other cancer entities associated with deregulated Jak-STAT pathway activation.

Arctigenin promotes apoptosis in ovarian cancer cells via the iNOS/NO/STAT3/survivin signalling.

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Huang, Ke; Li, Li-an; Meng, Yuan-guang; You, Yan-qin; Fu, Xiao-yu; Song, Lei

2014-12-01

Arctigenin is a biologically active lignan extracted from the seeds of Arctium lappa and shows anticancer activity against a variety of human cancers. The aim of this study was to determine the effects of arctigenin on ovarian cancer cell proliferation and survival and associated molecular mechanisms. Human ovarian cancer OVCAR3 and SKOV3 cells were treated with arctigenin, and cell proliferation and apoptosis were assessed. Western blot analysis was used to examine signal transducer and activator of transcription-3 (STAT3) phosphorylation and survivin and inducible nitric oxide synthase (iNOS) expression. The involvement of STAT3/survivin/iNOS/NO signalling in arctigenin action was checked. Arctigenin treatment resulted in a significant and dose-dependent inhibition of cell proliferation. Arctigenin-treated cells showed a 4-6 times increase in the percentage of apoptosis, compared with control cells. Pre-treatment with Ac-DEVD-CHO, a specific inhibitor of caspase-3, counteracted the induction of apoptosis by arctigenin. Arctigenin treatment significantly inhibited STAT3 phosphorylation and survivin and iNOS expression. Arctigenin-induced apoptosis was impaired by pre-transfection with survivin-expressing plasmid or addition of chemical nitric oxide (NO) donors. Additionally, exogenous NO prevented the suppression of STAT3 phosphorylation and survivin expression by arctigenin. Arctigenin treatment inhibits the proliferation and induces caspase-3-dependent apoptosis of ovarian cancer cells. Suppression of iNOS/NO/STAT3/survivin signalling is causally linked to the anticancer activity of arctigenin. Therefore, arctigenin may be applicable to anticancer therapy for ovarian cancer. © 2014 Nordic Association for the Publication of BCPT (former Nordic Pharmacological Society).

Novel compounds TAD-1822-7-F2 and F5 inhibited HeLa cells growth through the JAK/Stat signaling pathway.

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Yang, Tianfeng; Shi, Xianpeng; Kang, Yuan; Zhu, Man; Fan, Mengying; Zhang, Dongdong; Zhang, Yanmin

2018-07-01

Cervical carcinoma remains the second most common malignancy with a high mortality rate among women worldwide. TAD-1822-7-F2 (F2) and TAD-1822-7-F5 (F5) are novel compounds synthesized on the chemical structure of taspine derivatives, and show an effective suppression for HeLa cells. Our study aims to confirm the potential targets of F2 and F5, and investigate the underlying mechanism of the inhibitory effect on HeLa cells. In this study, Real Time Cell Analysis and crystal violet staining assay were conducted to investigate the effect of F2 and F5 on HeLa cells proliferation. And the analytical methods of surface plasmon resonance and quartz crystal microbalance were established and employed to study the interaction between F2 and F5 and potential target protein JAK2, suggesting that both compounds have strong interaction with the JAK2 protein. Western blot analysis, immunofluorescence staining study and PCR was conducted to investigate the molecules of JAK/Stat signaling pathway. Interestingly, F2 and F5 showed diverse regulation for signaling molecules because of their different chemical structure. F2 increased the expression of JAK2 and downregulated the level of P-JAK1 and P-JAK2, and decreased P-Stat3 (Ser727). While F5 could increase the expression of JAK2 and naturally decrease the phosphorylation of JAK1 and Tyk2, and decreased the expression of P-Stat6. Moreover, F2 and F5 showed the same downregulation on the P-Stat3 (Tyr705). Therefore, F2 and F5 could target the JAK2 protein and prevent the phosphorylation of JAKs to suppress the phosphorylation of the downstream effector Stats, which suggested that F2 and F5 have great potential to be the inhibitors of the JAK/Stat signaling pathway. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Hepatic Stellate Cell Coculture Enables Sorafenib Resistance in Huh7 Cells through HGF/c-Met/Akt and Jak2/Stat3 Pathways

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Weibo Chen

2014-01-01

Full Text Available Purpose. Tumor microenvironment confers drug resistance to kinase inhibitors by increasing RKT ligand levels that result in the activation of cell-survival signaling including PI3K and MAPK signals. We assessed whether HSC-LX2 coculture conferred sorafenib resistance in Huh7 and revealed the mechanism underlying the drug resistance. Experimental Design. The effect of LX2 on sorafenib resistance was determined by coculture system with Huh7 cells. The rescue function of LX2 supernatants was assessed by MTT assay and fluorescence microscopy. The underlying mechanism was tested by administration of pathway inhibitors and manifested by Western blotting. Results. LX2 coculture significantly induced sorafenib resistance in Huh7 by activating p-Akt that led to reactivation of p-ERK. LX2 secreted HGF into the culture medium that triggered drug resistance, and exogenous HGF could also induce sorafenib resistance. The inhibition of p-Akt blocked sorafenib resistance caused by LX2 coculture. Increased phosphorylation of Jak2 and Stat3 was also detected in LX2 cocultured Huh7 cells. The Jak inhibitor tofacitinib reversed sorafenib resistance by blocking Jak2 and Stat3 activation. The combined administration of sorafenib and p-Stat3 inhibitor S3I-201 augmented induced apoptosis even in the presence of sorafenib resistance. Conclusions. HSC-LX2 coculture induced sorafenib resistance in Huh7 through multiple pathways: HGF/c-Met/Akt pathway and Jak2/Stat3 pathway. A combined administration of sorafenib and S3I-201 was able to augment sorafenib-induced apoptosis even in the presence of LX2 coculture.

Opposing roles of STAT4 and Dnmt3a in Th1 gene regulation

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Pham, Duy; Yu, Qing; Walline, Crystal C.; Muthukrishnan, Rajarajeswari; Blum, Janice S.; Kaplan, Mark H.

2013-01-01

The Signal Transducer and Activator of Transcription factor STAT4 is a critical regulator of Th1 differentiation and inflammatory disease. Yet, how STAT4 regulates gene expression is still unclear. In this report, we define a STAT4-dependent sequence of events including H3K4 methylation, Jmjd3 association with STAT4 target loci, and a Jmjd3-dependent decrease in H3K27 trimethylation and DNA methyltransferase (Dnmt) 3a association with STAT4 target loci. Dnmt3a has an obligate role in repressing Th1 gene expression, and in Th1 cultures deficient in both STAT4 and Dnmt3a, there is recovery in the expression of a subset of Th1 genes that is sufficient to increase IFNγ production. Moreover, although STAT4-deficient mice are protected from the development of EAE, mice deficient in STAT4 and conditionally-deficient in Dnmt3a in T cells develop paralysis. Th1 genes that are de-repressed in the absence of Dnmt3a have greater induction following the ectopic expression of the Th1-associated transcription factors T-bet and Hlx1. Together, these data demonstrate that STAT4 and Dnmt3a play opposing roles in regulating Th1 gene expression, and that one mechanism for STAT4-dependent gene programming is in establishing a de-repressed genetic state susceptible to transactivation by additional fate-determining transcription factors. PMID:23772023

miR-204 inhibits angiogenesis and promotes sensitivity to cetuximab in head and neck squamous cell carcinoma cells by blocking JAK2-STAT3 signaling.

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Wu, Qingwei; Zhao, Yingying; Wang, Peihua

2018-03-01

This study aims to investigate the roles of miR-204 in tumor angiogenesis of head and neck squamous cell carcinoma (HNSCC). Here, we found that miR-204 level was reduced in HNSCC tissues relative to that in normal adjacent tissues. Overexpression of miR-204 promoted tumor angiogenesis in HNSCC cells. Mechanistically, JAK2 was identified as a direct target of miR-204, and miR-204 overexpression blocked JAK2/STAT3 pathway. Moreover, overexpression of JAK2 attenuated the inhibition of miR-204 on tumor angiogenesis of HNSCC. Furthermore, overexpression of miR-204 enhanced sensitivity of cetuximab in HNSCC cells, this effect was attenuated by JAK2 overexpression too. Importantly, JAK2 expression was negatively correlated with miR-204 level in HNSCC tissues. Therefore, miR-204 acts as a tumor suppressor by blocking JAK2/STAT3 pathway in HNSCC cells. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

IL-6 Promotes FSH-Induced VEGF Expression Through JAK/STAT3 Signaling Pathway in Bovine Granulosa Cells

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Meng Yang

2017-11-01

Full Text Available Background/Aims: Vascular endothelial growth factor (VEGF has been demonstrated to play a pivotal role in the regulation of angiogenesis in ovarian follicular development, particularly during the preovulatory period. Although numerous studies have shown that interleukin-6 (IL-6 is one of the major inducing factors that regulate the expression of VEGF in non-ovarian cells, whether it involved in regulating the expression of VEGF in normal ovarian granulosa cells is still unknown. The aim of this study was to elucidate the mechanisms underlying the effect of IL-6 on FSH-induced VEGF expression in bovine granulosa cells derived from large follicles. Methods: VEGF mRNA expression in granulosa cells after IL-6 with/without inhibitors treatment was analyzed by RT-qPCR. Phosphorylation levels of ERK1/2 and STAT3 proteins induced by IL-6 were analyzed by western blotting. The protein levels produced by granulosa cells were detected by ELISA. Results: High concentration of IL-6 (10ng/ml can significantly up-regulate FSH-induced VEGF gene and protein expression levels in granulosa cells, and also promote the VEGF upstream regulators HIF-1α and COX2 mRNA expression. VEGF expression levels were significantly decreased after specifically blocking HIF-1α and COX2 by using inhibitors. The up-regulation effect of IL-6 on FSH-induced VEGF expression in granulosa cells mainly through activating the JAK/STAT3 signaling pathway, which can be impaired by JAK inhibitors. Conclusion: IL-6 can promote FSH-induced VEGF expression in granulosa cells, which is mainly achieved by increasing the expression of HIF-1α and COX2.This promoting effect is mediated by activating the JAK/STAT3 pathway. Moreover, there may be a synergistic relationship between FSH and IL-6 in the regulation of VEGF expression.

Secoisolariciresinol diglucoside prevents the oxidative stress-induced apoptosis of myocardial cells through activation of the JAK2/STAT3 signaling pathway.

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Huang, Guiqiong; Huang, Xiaofang; Liu, Min; Hua, Yue; Deng, Bo; Jin, Wen; Yan, Wen; Tan, Zhangbin; Wu, Yifen; Liu, Bin; Zhou, Yingchun

2018-06-01

Myocardial cell apoptosis mediated by oxidative stress has previously been identified as a key process in ischemic heart disease. Secoisolariciresinol diglucoside (SDG), a polyphenolic plant lignan primarily found in flaxseed, has been demonstrated to effectively protect myocardial cells from apoptosis. In the present study, the role of the Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) was investigated in mediating the protective effect of SDG. Findings of the present study revealed that treatment with H2O2 reduced cell viability and induced apoptosis in H9C2 rat cardiomyocytes. However, SDG was able to reduce the effect of H2O2 in a dose‑dependent manner. H2O2 reduced the expression level of phosphorylated STAT3 and inhibited the levels of B‑cell lymphoma‑extra‑large and induced myeloid leukemia cell differentiation protein, which are the STAT3 target genes. Conversely, SDG rescued phosphorylation of STAT3 and increased the levels of STAT3 target genes. Treatment with SDG alone led to a dose‑dependent increased phosphorylation of JAK2 and STAT3, without activating Src. Furthermore, the anti‑apoptotic effects of SDG were partially abolished by a JAK2/STAT3 inhibitor. In addition, molecular docking revealed that SDG may bind to the protein kinase domain of JAK2, at a binding energy of ‑8.258 kcal/mol. Molecular dynamics simulations revealed that JAK2‑SDG binding was stable. In conclusion, activation of the JAK2/STAT3 signaling pathway contributed to the anti‑apoptotic activity of SDG, which may be a potential JAK2 activator.

1,4-benzoquinone-induced STAT-3 hypomethylation in AHH-1 cells: Role of oxidative stress

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Jing Yang

2015-01-01

Full Text Available Benzene, a known occupational and environmental contaminant, is associated with increased risk of leukemia. The objectives of this study were to elucidate the regulatory mechanism of the hypomethylated STAT3 involved in benzene toxicity in vitro. As 1,4-benzoquinone (1,4-BQ is one of benzene’s major toxic metabolites, AHH-1 cells were treated by 1,4-BQ for 24 h with or without pretreatment of the antioxidant a-LA or the methyltransferase inhibitor, 5-aza-2′ deoxycytidine (5-aza. The cell viability was investigated using the 3-(4, 5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT assay. ROS was determined via 2′,7′-dichlorodihydrofluorescein diacetate (DCFDA flow cytometric assays. The level of oxidative stress marker 8-OHdG was measured by enzyme-linked immunosorbent assay. Methylation-specific PCR was used to detect the methylation status of STAT3. Results indicated the significantly increasing expression of ROS and 8-OHdG which accompanied with STAT3 hypomethylation in 1,4-BQ-treated AHH-1 cells. α-LA suppressed the expression of both ROS and 8-OHdG, simultaneously reversed 1,4-BQ-induced STAT3 hypomethylation. However, although the methylation inhibitor, 5-aza reduced the expression level of ROS and 8-OHdG, but had no obvious inhibiting effect on STAT3 methylation level. Taken together, oxidative stress are involved 1,4-BQ-induced STAT3 methylation expression.

Euglycemia Restoration by Central Leptin in Type 1 Diabetes Requires STAT3 Signaling but Not Fast-Acting Neurotransmitter Release.

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Xu, Yuanzhong; Chang, Jeffrey T; Myers, Martin G; Xu, Yong; Tong, Qingchun

2016-04-01

Central leptin action is sufficient to restore euglycemia in insulinopenic type 1 diabetes (T1D); however, the underlying mechanism remains poorly understood. To examine the role of intracellular signal transducer and activator of transcription 3 (STAT3) pathways, we used LepRs/s mice with disrupted leptin-phosphorylated STAT3 signaling to test the effect of central leptin on euglycemia restoration. These mice developed streptozocin-induced T1D, which was surprisingly not associated with hyperglucagonemia, a typical manifestation in T1D. Further, leptin action on euglycemia restoration was abrogated in these mice, which was associated with refractory hypercorticosteronemia. To examine the role of fast-acting neurotransmitters glutamate and γ-aminobutyric acid (GABA), two major neurotransmitters in the brain, from leptin receptor (LepR) neurons, we used mice with disrupted release of glutamate, GABA, or both from LepR neurons. Surprisingly, all mice responded normally to leptin-mediated euglycemia restoration, which was associated with expected correction from hyperglucagonemia and hyperphagia. In contrast, mice with loss of glutamate and GABA appeared to develop an additive obesity effect over those with loss of single neurotransmitter release. Thus, our study reveals that STAT3 signaling, but not fast-acting neurotransmitter release, is required for leptin action on euglycemia restoration and that hyperglucagonemia is not required for T1D. © 2016 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.

Phosphorylation sites of Arabidopsis MAP Kinase Substrate 1 (MKS1)

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Caspersen, M.B.; Qiu, J.-L.; Zhang, X.

2007-01-01

The Arabidopsis MAP kinase 4 (MPK4) substrate MKS1 was expressed in Escherichia coli and purified, full-length, 6x histidine (His)-tagged MKS1 was phosphorylated in vitro by hemagglutinin (HA)-tagged MPK4 immuno-precipitated from plants. MKS1 phosphorylation was initially verified by electrophore......The Arabidopsis MAP kinase 4 (MPK4) substrate MKS1 was expressed in Escherichia coli and purified, full-length, 6x histidine (His)-tagged MKS1 was phosphorylated in vitro by hemagglutinin (HA)-tagged MPK4 immuno-precipitated from plants. MKS1 phosphorylation was initially verified...... phosphopeptide detection. As MAP kinases generally phosphorylate serine or threonine followed by proline (Ser/Thr-Pro), theoretical masses of potentially phosphorylated peptides were calculated and mass spectrometric peaks matching these masses were fragmented and searched for a neutral-loss signal...... at approximately 98 Da indicative of phosphorylation. Additionally, mass spectrometric peaks present in the MPK4-treated MKS1, but not in the control peptide map of untreated MKS1, were fragmented. Fragmentation spectra were subjected to a MASCOT database search which identified three of the twelve Ser-Pro serine...

IL-6 signaling by STAT3 participates in the change from hyperplasia to neoplasia in NRP-152 and NRP-154 rat prostatic epithelial cells

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Barton, Beverly E; Murphy, Thomas F; Adem, Patricia; Watson, Richard A; Irwin, Robert J; Huang, Hosea F

2001-01-01

STAT3 phosphorylation is associated with the neoplastic state in many types of cancer, including prostate cancer. We investigated the role of IL-6 signaling and phosphorylation of STAT3 in 2 rat prostatic epithelial lines. NRP-152 and NRP-154 cells were derived from the same rat prostate, yet the NRP-152 cells are not tumorigenic while the NRP-154 cells are tumorigenic. These lines are believed to represent 2 of the stages in the development of prostate cancer, hyperplasia and neoplasia. Differences in signaling pathways should play a role in the 2 phenotypes, hyperplastic and neoplastic. We looked at the phosphorylation state of STAT3 by intracellular flow cytometry, using phospho-specific antibodies to STAT3. We used the same method to examine IL-6 production by the cell lines. We also measured apoptosis by binding of fluorescent annexin V to the cells. Although both cells lines made IL-6 constitutively, phosphorylated-STAT3 was present in untreated NRP-154 cells, but not in NRP-152 cells. Treatment with dexamethasone inhibited the IL-6 production of NRP-152 cells, but enhanced that of NRP-154 cells. Treatment with the JAK2 inhibitor AG490 induced apoptosis in NRP-152, but not NRP-154 cells. We conclude from these experiments that STAT3 activity plays a role in the phenotype of NRP-154 cell, but not NRP-152 cells. The significance of alternative IL-6 signaling pathways in the different phenotypes of the 2 cell lines is discussed

Morbillivirus control of the interferon response: relevance of STAT2 and mda5 but not STAT1 for canine distemper virus virulence in ferrets.

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Svitek, Nicholas; Gerhauser, Ingo; Goncalves, Christophe; Grabski, Elena; Döring, Marius; Kalinke, Ulrich; Anderson, Danielle E; Cattaneo, Roberto; von Messling, Veronika

2014-03-01

The V proteins of paramyxoviruses control the innate immune response. In particular, the V protein of the genus Morbillivirus interferes with the signal transducer and activator of transcription 1 (STAT1), STAT2, and melanoma differentiation-associated protein 5 (mda5) signaling pathways. To characterize the contributions of these pathways to canine distemper virus (CDV) pathogenesis, we took advantage of the knowledge about the mechanisms of interaction between the measles virus V protein with these key regulators of innate immunity. We generated recombinant CDVs with V proteins unable to properly interact with STAT1, STAT2, or mda5. A virus with combined STAT2 and mda5 deficiencies was also generated, and available wild-type and V-protein-knockout viruses were used as controls. Ferrets infected with wild-type and STAT1-blind viruses developed severe leukopenia and loss of lymphocyte proliferation activity and succumbed to the disease within 14 days. In contrast, animals infected with viruses with STAT2 or mda5 defect or both STAT2 and mda5 defects developed a mild self-limiting disease similar to that associated with the V-knockout virus. This study demonstrates the importance of interference with STAT2 and mda5 signaling for CDV immune evasion and provides a starting point for the development of morbillivirus vectors with reduced immunosuppressive properties. The V proteins of paramyxoviruses interfere with the recognition of the virus by the immune system of the host. For morbilliviruses, the V protein is known to interact with the signal transducer and activator of transcription 1 (STAT1) and STAT2 and the melanoma differentiation-associated protein 5 (mda5), which are involved in interferon signaling. Here, we examined the contribution of each of these signaling pathways to the pathogenesis of the carnivore morbillivirus canine distemper virus. Using viruses selectively unable to interfere with the respective signaling pathway to infect ferrets, we found that

IL-8 induces miR-424-5p expression and modulates SOCS2/STAT5 signaling pathway in oral squamous cell carcinoma.

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Peng, Hsuan-Yu; Jiang, Shih-Sheng; Hsiao, Jenn-Ren; Hsiao, Michael; Hsu, Yuan-Ming; Wu, Guan-Hsun; Chang, Wei-Min; Chang, Jang-Yang; Jin, Shiow-Lian Catherine; Shiah, Shine-Gwo

2016-06-01

Suppressor of cytokine signaling (SOCS) proteins are negative feedback regulators of the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway. Dysregulation of SOCS protein expression in cancers can be one of the mechanisms that maintain STAT activation, but this mechanism is still poorly understood in oral squamous cell carcinoma (OSCC). Here, we report that SOCS2 protein is significantly downregulated in OSCC patients and its levels are inversely correlated with miR-424-5p expression. We identified the SOCS2 protein, which modulates STAT5 activity, as a direct target of miR-424-5p. The miR-424-5p-induced STAT5 phosphorylation, matrix metalloproteinases (MMPs) expression, and cell migration and invasion were blocked by SOCS2 restoration, suggesting that miR-424-5p exhibits its oncogenic activity through negatively regulating SOCS2 levels. Furthermore, miR-424-5p expression could be induced by the cytokine IL-8 primarily through enhancing STAT5 transcriptional activity rather than NF-κB signaling. Antagomir-mediated inactivation of miR-424-5p prevented the IL-8-induced cell migration and invasion, indicating that miR-424-5p is required for IL-8-induced cellular invasiveness. Taken together, these data indicate that STAT5-dependent expression of miR-424-5p plays an important role in mediating IL-8/STAT5/SOCS2 feedback loop, and scavenging miR-424-5p function using antagomir may have therapeutic potential for the treatment of OSCC. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

PKA regulates calcineurin function through the phosphorylation of RCAN1: Identification of a novel phosphorylation site

International Nuclear Information System (INIS)

Kim, Seon Sook; Lee, Eun Hye; Lee, Kooyeon; Jo, Su-Hyun; Seo, Su Ryeon

2015-01-01

Calcineurin is a calcium/calmodulin-dependent phosphatase that has been implicated in T cell activation through the induction of nuclear factors of activated T cells (NFAT). We have previously suggested that endogenous regulator of calcineurin (RCAN1, also known as DSCR1) is targeted by protein kinase A (PKA) for the control of calcineurin activity. In the present study, we characterized the PKA-mediated phosphorylation site in RCAN1 by mass spectrometric analysis and revealed that PKA directly phosphorylated RCAN1 at the Ser 93. PKA-induced phosphorylation and the increase in the half-life of the RCAN1 protein were prevented by the substitution of Ser 93 with Ala (S93A). Furthermore, the PKA-mediated phosphorylation of RCAN1 at Ser 93 potentiated the inhibition of calcineurin-dependent pro-inflammatory cytokine gene expression by RCAN1. Our results suggest the presence of a novel phosphorylation site in RCAN1 and that its phosphorylation influences calcineurin-dependent inflammatory target gene expression. - Highlights: • We identify novel phosphorylation sites in RCAN1 by LC-MS/MS analysis. • PKA-dependent phosphorylation of RCAN1 at Ser 93 inhibits calcineurin-mediated intracellular signaling. • We show the immunosuppressive function of RCAN1 phosphorylation at Ser 93 in suppressing cytokine expression

Novel 1,3,4-thiadiazoles inhibit colorectal cancer via blockade of IL-6/COX-2 mediated JAK2/STAT3 signals as evidenced through data-based mathematical modeling.

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Raj, Vinit; Bhadauria, Archana S; Singh, Ashok K; Kumar, Umesh; Rai, Amit; Keshari, Amit K; Kumar, Pranesh; Kumar, Dinesh; Maity, Biswanath; Nath, Sneha; Prakash, Anand; Ansari, Kausar M; Jat, Jawahar L; Saha, Sudipta

2018-03-23

We attempted a preclinical study using DMH-induced CRC rat model to evaluate the antitumor potential of our recently synthesized 1,3,4-thiadiazoles. The molecular insights were confirmed through ELISA, qRT-PCR and western blot analyses. The CRC condition was produced in response to COX-2 and IL-6 induced activation of JAK2/STAT3 which, in turn, was due to the enhanced phosphorylation of JAK2 and STAT3. The treatment with 1,3,4-thiadiazole derivatives (VR24 and VR27) caused the significant blockade of this signaling pathway. The behavior of STAT3 populations in response to IL-6 and COX-2 stimulations was further confirmed through data-based mathematical modeling using the quantitative western blot data. Finally, VR24 and VR27 restored the perturbed metabolites associated to DMH-induced CRC as evidenced through 1 H NMR based serum metabolomics. The tumor protecting ability of VR24 and VR27 was found comparable or to some degree better than the marketed chemotherapeutics, 5-flurouracil. Copyright © 2018 Elsevier Ltd. All rights reserved.

Active Stat3 is required for survival of human squamous cell carcinoma cells in serum-free conditions

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DiGiovanni John

2006-04-01

Full Text Available Abstract Background Squamous cell carcinoma (SCC of the skin is the most aggressive form of non-melanoma skin cancer (NMSC, and is the single most commonly diagnosed cancer in the U.S., with over one million new cases reported each year. Recent studies have revealed an oncogenic role of activated signal transducer and activator of transcription 3 (Stat3 in many human tumors, especially in those of epithelial origin, including skin SCC. Stat3 is a mediator of numerous growth factor and cytokine signaling pathways, all of which activate it through phosphorylation of tyrosine 705. Results To further address the role of Stat3 in skin SCC tumorigenesis, we have analyzed a panel of human skin-derived cell lines ranging from normal human epidermal keratinocytes (NHEK, to non-tumorigenic transformed skin cells (HaCaT, to highly tumorigenic cells (SRB1-m7 and SRB12-p9 and observed a positive correlation between Stat3 phosphorylation and SCC malignancy. We next determined the role of Stat3 activity in cell proliferation and viability under serum-free culture conditions. This was accomplished by suppressing Stat3 activity in the SRB12-p9 cells through stable expression of a dominant negative acting form of Stat3β, which contains a tyrosine 705 to phenylalanine mutation (S3DN. The S3DN cells behaved similar to parental SRB12-p9 cells when cultured in optimal growth conditions, in the presence of 10% fetal calf serum. However, unlike the SRB12-p9 cells, S3DN cells underwent apoptotic cell death when cultured in serum-free medium (SFM. This was evidenced by multiple criteria, including accumulation of sub-G1 particles, induced PARP cleavage, and acquisition of the characteristic morphological changes associated with apoptosis. Conclusion This study provides direct evidence for a role for Stat3 in maintaining cell survival in the conditions of exogenous growth factor deprivation produced by culture in SFM. We also propose that delivery of the S3DN gene or

GDNF facilitates differentiation of the adult dentate gyrus-derived neural precursor cells into astrocytes via STAT3

International Nuclear Information System (INIS)

Boku, Shuken; Nakagawa, Shin; Takamura, Naoki; Kato, Akiko; Takebayashi, Minoru; Hisaoka-Nakashima, Kazue; Omiya, Yuki; Inoue, Takeshi; Kusumi, Ichiro

2013-01-01

Highlights: •GDNF has no effect on ADP proliferation and apoptosis. •GDNF increases ADP differentiation into astrocyte. •A specific inhibitor of STAT3 decreases the astrogliogenic effect of GDNF. •STAT3 knockdown by lentiviral shRNA vector also decreases the astrogliogenic effect of GDNF. •GDNF increases the phosphorylation of STAT3. -- Abstract: While the pro-neurogenic actions of antidepressants in the adult hippocampal dentate gyrus (DG) are thought to be one of the mechanisms through which antidepressants exert their therapeutic actions, antidepressants do not increase proliferation of neural precursor cells derived from the adult DG. Because previous studies showed that antidepressants increase the expression and secretion of glial cell line-derived neurotrophic factor (GDNF) in C6 glioma cells derived from rat astrocytes and GDNF increases neurogenesis in adult DG in vivo, we investigated the effects of GDNF on the proliferation, differentiation and apoptosis of cultured neural precursor cells derived from the adult DG. Data showed that GDNF facilitated the differentiation of neural precursor cells into astrocytes but had no effect on their proliferation or apoptosis. Moreover, GDNF increased the phosphorylation of STAT3, and both a specific inhibitor of STAT3 and lentiviral shRNA for STAT3 decreased their differentiation into astrocytes. Taken together, our findings suggest that GDNF facilitates astrogliogenesis from neural precursor cells in adult DG through activating STAT3 and that this action might indirectly affect neurogenesis

GDNF facilitates differentiation of the adult dentate gyrus-derived neural precursor cells into astrocytes via STAT3

Energy Technology Data Exchange (ETDEWEB)

Boku, Shuken, E-mail: shuboku@med.hokudai.ac.jp [Department of Psychiatry, Hokkaido University Graduate School of Medicine, Sapporo (Japan); Nakagawa, Shin [Department of Psychiatry, Hokkaido University Graduate School of Medicine, Sapporo (Japan); Takamura, Naoki [Pharmaceutical Laboratories, Dainippon Sumitomo Pharma Co. Ltd., Osaka (Japan); Kato, Akiko [Department of Psychiatry, Hokkaido University Graduate School of Medicine, Sapporo (Japan); Takebayashi, Minoru [Department of Psychiatry, National Hospital Organization Kure Medical Center, Kure (Japan); Hisaoka-Nakashima, Kazue [Department of Pharmacology, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima (Japan); Omiya, Yuki; Inoue, Takeshi; Kusumi, Ichiro [Department of Psychiatry, Hokkaido University Graduate School of Medicine, Sapporo (Japan)

2013-05-17

Highlights: •GDNF has no effect on ADP proliferation and apoptosis. •GDNF increases ADP differentiation into astrocyte. •A specific inhibitor of STAT3 decreases the astrogliogenic effect of GDNF. •STAT3 knockdown by lentiviral shRNA vector also decreases the astrogliogenic effect of GDNF. •GDNF increases the phosphorylation of STAT3. -- Abstract: While the pro-neurogenic actions of antidepressants in the adult hippocampal dentate gyrus (DG) are thought to be one of the mechanisms through which antidepressants exert their therapeutic actions, antidepressants do not increase proliferation of neural precursor cells derived from the adult DG. Because previous studies showed that antidepressants increase the expression and secretion of glial cell line-derived neurotrophic factor (GDNF) in C6 glioma cells derived from rat astrocytes and GDNF increases neurogenesis in adult DG in vivo, we investigated the effects of GDNF on the proliferation, differentiation and apoptosis of cultured neural precursor cells derived from the adult DG. Data showed that GDNF facilitated the differentiation of neural precursor cells into astrocytes but had no effect on their proliferation or apoptosis. Moreover, GDNF increased the phosphorylation of STAT3, and both a specific inhibitor of STAT3 and lentiviral shRNA for STAT3 decreased their differentiation into astrocytes. Taken together, our findings suggest that GDNF facilitates astrogliogenesis from neural precursor cells in adult DG through activating STAT3 and that this action might indirectly affect neurogenesis.

Chemokine CCL2–CCR2 Signaling Induces Neuronal Cell Death via STAT3 Activation and IL-1β Production after Status Epilepticus

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Tian, Dai-Shi; Feng, Li-Jie; Liu, Jun-Li

2017-01-01

Elevated levels of chemokine C-C motif ligand 2 (CCL2) and its receptor CCR2 have been reported in patients with temporal lobe epilepsy and in experimental seizures. However, the functional significance and molecular mechanism underlying CCL2–CCR2 signaling in epileptic brain remains largely unknown. In this study, we found that the upregulated CCL2 was mainly expressed in hippocampal neurons and activated microglia from mice 1 d after kainic acid (KA)-induced seizures. Taking advantage of CX3CR1GFP/+:CCR2RFP/+ double-transgenic mice, we demonstrated that CCL2–CCR2 signaling has a role in resident microglial activation and blood-derived monocyte infiltration. Moreover, seizure-induced degeneration of neurons in the hippocampal CA3 region was attenuated in mice lacking CCL2 or CCR2. We further showed that CCR2 activation induced STAT3 (signal transducer and activator of transcription 3) phosphorylation and IL-1β production, which are critical for promoting neuronal cell death after status epilepticus. Consistently, pharmacological inhibition of STAT3 by WP1066 reduced seizure-induced IL-1β production and subsequent neuronal death. Two weeks after KA-induced seizures, CCR2 deficiency not only reduced neuronal loss, but also attenuated seizure-induced behavioral impairments, including anxiety, memory decline, and recurrent seizure severity. Together, we demonstrated that CCL2–CCR2 signaling contributes to neurodegeneration via STAT3 activation and IL-1β production after status epilepticus, providing potential therapeutic targets for the treatment of epilepsy. SIGNIFICANCE STATEMENT Epilepsy is a global concern and epileptic seizures occur in many neurological conditions. Neuroinflammation associated with microglial activation and monocyte infiltration are characteristic of epileptic brains. However, molecular mechanisms underlying neuroinflammation in neuronal death following epilepsy remain to be elucidated. Here we demonstrate that CCL2–CCR2 signaling is

The Signal Transducer and Activator of Transcription 1 (STAT1 Inhibits Mitochondrial Biogenesis in Liver and Fatty Acid Oxidation in Adipocytes.

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Jennifer D Sisler

Full Text Available The transcription factor STAT1 plays a central role in orchestrating responses to various pathogens by activating the transcription of nuclear-encoded genes that mediate the antiviral, the antigrowth, and immune surveillance effects of interferons and other cytokines. In addition to regulating gene expression, we report that STAT1-/- mice display increased energy expenditure and paradoxically decreased release of triglycerides from white adipose tissue (WAT. Liver mitochondria from STAT1-/- mice show both defects in coupling of the electron transport chain (ETC and increased numbers of mitochondria. Consistent with elevated numbers of mitochondria, STAT1-/- mice expressed increased amounts of PGC1α, a master regulator of mitochondrial biogenesis. STAT1 binds to the PGC1α promoter in fed mice but not in fasted animals, suggesting that STAT1 inhibited transcription of PGC1α. Since STAT1-/- mice utilized more lipids we examined white adipose tissue (WAT stores. Contrary to expectations, fasted STAT1-/- mice did not lose lipid from WAT. β-adrenergic stimulation of glycerol release from isolated STAT1-/- WAT was decreased, while activation of hormone sensitive lipase was not changed. These findings suggest that STAT1-/- adipose tissue does not release glycerol and that free fatty acids (FFA re-esterify back to triglycerides, thus maintaining fat mass in fasted STAT1-/- mice.

SHP-1 is a target of regorafenib in colorectal cancer

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Lin, Hang; Hung, Man-Hsin; Chen, Yen-Lin; Huang, Jui-Wen; Tai, Wei-Tien; Yu, Hui-Chuan; Chen, Kuen-Feng

2014-01-01

Regorafenib is an inhibitor of multiple protein kinases which exerts antitumor and antimetastatic activities in metastatic colorectal cancer (CRC). SH2 domain-containing phosphatase 1 (SHP-1) is reported to have tumor suppressive potential because it acts as a negative regulator of p-STAT3Tyr705 signaling. However, little is known about the mechanism regarding regorafenib affects SHP-1 tyrosine phosphatase activity and leads to apoptosis and tumor suppression in CRC. Here, we found that regorafenib triggered apoptotic cell death and significantly enhanced SHP-1 activity, which dramatically decreased the phosphorylated form of STAT3 at Tyr705 (p-STAT3Tyr705). Importantly, regorafenib augmented SHP-1 activity by direct disruption of the association between N-SH2 and catalytic PTP domain of SHP-1. Deletion of the N-SH2 domain (dN1) or point mutation (D61A) of SHP-1 blocked the effect of regorafenib-induced SHP-1 activity, growth inhibition and a decrease of p-STAT3Tyr705 expression, suggesting that regorafenib triggers a conformational change in SHP-1 by relieving its autoinhibition. In vivo assay showed that regorafenib significantly inhibited xenograft growth and decreased p-STAT3Tyr705 expression but induced higher SHP-1 activity. Collectively, regorafenib is a novel SHP-1 agonist exerts superior anti-tumor effects by enhancing SHP-1 activity that directly targets p-STAT3Tyr705. Small molecule-enhancement of SHP-1 activity may be a promising therapeutic approach for CRC treatment. PMID:25071018

Epstein-Barr Virus Latent Membrane Protein 2A (LMP2A) enhances IL-10 production through the activation of Bruton's tyrosine kinase and STAT3.

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Incrocci, Ryan; Barse, Levi; Stone, Amanda; Vagvala, Sai; Montesano, Michael; Subramaniam, Vijay; Swanson-Mungerson, Michelle

2017-01-01

Previous data demonstrate that Epstein-Barr Virus Latent Membrane Protein 2A (LMP2A) enhances IL-10 to promote the survival of LMP2A-expressing B cell lymphomas. Since STAT3 is an important regulator of IL-10 production, we hypothesized that LMP2A activates a signal transduction cascade that increases STAT3 phosphorylation to enhance IL-10. Using LMP2A-negative and -positive B cell lines, the data indicate that LMP2A requires the early signaling molecules of the Syk/RAS/PI3K pathway to increase IL-10. Additional studies indicate that the PI3K-regulated kinase, BTK, is responsible for phosphorylating STAT3, which ultimately mediates the LMP2A-dependent increase in IL-10. These data are the first to show that LMP2A signaling results in STAT3 phosphorylation in B cells through a PI3K/BTK-dependent pathway. With the use of BTK and STAT3 inhibitors to treat B cell lymphomas in clinical trials, these findings highlight the possibility of using new pharmaceutical approaches to treat EBV-associated lymphomas that express LMP2A. Copyright © 2016 Elsevier Inc. All rights reserved.

Contraction regulates site-specific phosphorylation of TBC1D1 in skeletal muscle.

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Vichaiwong, Kanokwan; Purohit, Suneet; An, Ding; Toyoda, Taro; Jessen, Niels; Hirshman, Michael F; Goodyear, Laurie J

2010-10-15

TBC1D1 (tre-2/USP6, BUB2, cdc16 domain family member 1) is a Rab-GAP (GTPase-activating protein) that is highly expressed in skeletal muscle, but little is known about TBC1D1 regulation and function. We studied TBC1D1 phosphorylation on three predicted AMPK (AMP-activated protein kinase) phosphorylation sites (Ser231, Ser660 and Ser700) and one predicted Akt phosphorylation site (Thr590) in control mice, AMPKα2 inactive transgenic mice (AMPKα2i TG) and Akt2-knockout mice (Akt2 KO). Muscle contraction significantly increased TBC1D1 phosphorylation on Ser231 and Ser660, tended to increase Ser700 phosphorylation, but had no effect on Thr590. AICAR (5-aminoimidazole-4-carboxyamide ribonucleoside) also increased phosphorylation on Ser231, Ser660 and Ser700, but not Thr590, whereas insulin only increased Thr590 phosphorylation. Basal and contraction-stimulated TBC1D1 Ser231, Ser660 and Ser700 phosphorylation were greatly reduced in AMPKα2i TG mice, although contraction still elicited a small increase in phosphorylation. Akt2 KO mice had blunted insulin-stimulated TBC1D1 Thr590 phosphorylation. Contraction-stimulated TBC1D1 Ser231 and Ser660 phosphorylation were normal in high-fat-fed mice. Glucose uptake in vivo was significantly decreased in tibialis anterior muscles overexpressing TBC1D1 mutated on four predicted AMPK phosphorylation sites. In conclusion, contraction causes site-specific phosphorylation of TBC1D1 in skeletal muscle, and TBC1D1 phosphorylation on AMPK sites regulates contraction-stimulated glucose uptake. AMPK and Akt regulate TBC1D1 phosphorylation, but there must be additional upstream kinases that mediate TBC1D1 phosphorylation in skeletal muscle.

Leptin differentially regulate STAT3 activation in ob/ob mouse adipose mesenchymal stem cells

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Zhou Zhou

2012-12-01

Full Text Available Abstract Background Leptin-deficient ob/ob mice exhibit adipocyte hypertrophy and hyperplasia as well as elevated adipose tissue and systemic inflammation. Multipotent stem cells isolated from adult adipose tissue can differentiate into adipocytes ex vivo and thereby contribute toward increased adipocyte cell numbers, obesity, and inflamm ation. Currently, information is lacking regarding regulation of adipose stem cell numbers as well as leptin-induced inflammation and its signaling pathway in ob/ob mice. Methods Using leptin deficient ob/ob mice, we investigated whether leptin injection into ob/ob mice increases adipose stem cell numbers and adipose tissue inflammatory marker MCP-1 mRNA and secretion levels. We also determined leptin mediated signaling pathways in the adipose stem cells. Results We report here that adipose stem cell number is significantly increased following leptin injection in ob/ob mice and with treatment of isolated stem cells with leptin in vitro. Leptin also up-regulated MCP-1 secretion in a dose- and time-dependent manner. We further showed that increased MCP-1 mRNA levels were due to increased phosphorylation of Signal Transducer and Activator of Transcription 3 (STAT3 Ser727 but not STAT3 Tyr705 phosphorylation, suggesting differential regulation of MCP-1 gene expression under basal and leptin-stimulated conditions in adipose stem cells. Conclusions Taken together, these studies demonstrate that leptin increases adipose stem cell number and differentially activates STAT3 protein resulting in up-regulation of MCP-1 gene expression. Further studies of mechanisms mediating adipose stem cell hyperplasia and leptin signaling in obesity are warranted and may help identify novel anti-obesity target strategies.

The synthetic α-bromo-2',3,4,4'-tetramethoxychalcone (α-Br-TMC) inhibits the JAK/STAT signaling pathway.

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Pinz, Sophia; Unser, Samy; Brueggemann, Susanne; Besl, Elisabeth; Al-Rifai, Nafisah; Petkes, Hermina; Amslinger, Sabine; Rascle, Anne

2014-01-01

Signal transducer and activator of transcription STAT5 and its upstream activating kinase JAK2 are essential mediators of cytokine signaling. Their activity is normally tightly regulated and transient. However, constitutive activation of STAT5 is found in numerous cancers and a driving force for malignant transformation. We describe here the identification of the synthetic chalcone α-Br-2',3,4,4'-tetramethoxychalcone (α-Br-TMC) as a novel JAK/STAT inhibitor. Using the non-transformed IL-3-dependent B cell line Ba/F3 and its oncogenic derivative Ba/F3-1*6 expressing constitutively activated STAT5, we show that α-Br-TMC targets the JAK/STAT pathway at multiple levels, inhibiting both JAK2 and STAT5 phosphorylation. Moreover, α-Br-TMC alters the mobility of STAT5A/B proteins in SDS-PAGE, indicating a change in their post-translational modification state. These alterations correlate with a decreased association of STAT5 and RNA polymerase II with STAT5 target genes in chromatin immunoprecipitation assays. Interestingly, expression of STAT5 target genes such as Cis and c-Myc was differentially regulated by α-Br-TMC in normal and cancer cells. While both genes were inhibited in IL-3-stimulated Ba/F3 cells, expression of the oncogene c-Myc was down-regulated and that of the tumor suppressor gene Cis was up-regulated in transformed Ba/F3-1*6 cells. The synthetic chalcone α-Br-TMC might therefore represent a promising novel anticancer agent for therapeutic intervention in STAT5-associated malignancies.

Serotonin suppresses β-casein expression via PTP1B activation in human mammary epithelial cells.

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Chiba, Takeshi; Maeda, Tomoji; Sanbe, Atsushi; Kudo, Kenzo

2016-04-22

Serotonin (5-hydroxytriptamine, 5-HT) has an important role in milk volume homeostasis within the mammary gland during lactation. We have previously shown that the expression of β-casein, a differentiation marker in mammary epithelial cells, is suppressed via 5-HT-mediated inhibition of signal transduction and activator of transcription 5 (STAT5) phosphorylation in the human mammary epithelial MCF-12A cell line. In addition, the reduction of β-casein in turn was associated with 5-HT7 receptor expression in the cells. The objective of this study was to determine the mechanisms underlying the 5-HT-mediated suppression of β-casein and STAT5 phosphorylation. The β-casein level and phosphorylated STAT5 (pSTAT5)/STAT5 ratio in the cells co-treated with 5-HT and a protein kinase A (PKA) inhibitor (KT5720) were significantly higher than those of cells treated with 5-HT alone. Exposure to 100 μM db-cAMP for 6 h significantly decreased the protein levels of β-casein and pSTAT5 and the pSTAT5/STAT5 ratio, and significantly increased PTP1B protein levels. In the cells co-treated with 5-HT and an extracellular signal-regulated kinase1/2 (ERK) inhibitor (FR180294) or Akt inhibitor (124005), the β-casein level and pSTAT5/STAT5 ratio were equal to those of cells treated with 5-HT alone. Treatment with 5-HT significantly induced PTP1B protein levels, whereas its increase was inhibited by KT5720. In addition, the PTP1B inhibitor sc-222227 increased the expression levels of β-casein and the pSTAT5/STAT5 ratio. Our observations indicate that PTP1B directly regulates STAT5 phosphorylation and that its activation via the cAMP/PKA pathway downstream of the 5-HT7 receptor is involved in the suppression of β-casein expression in MCF-12A cells. Copyright © 2016 Elsevier Inc. All rights reserved.

STAT3 Regulates Proliferation and Immunogenicity of the Ewing Family of Tumors In Vitro

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Sam Behjati

2012-01-01

Full Text Available The Ewing sarcoma family of tumors (ESFT represents an aggressive spectrum of malignant tumour types with common defining histological and cytogenetic features. To evaluate the functional activation of signal transducer and activator of transcription 3 (STAT3 in ESFT, we evaluated its activation in primary tissue sections and observed the functional consequences of its inhibition in ESFT cell lines. STAT3 was activated (tyrosine 705-phosphorylated in 18 out of 31 primary tumours (58%, either diffusely (35% or focally (23%. STAT3 was constitutively activated in 3 out of 3 ESFT cell lines tested, and its specific chemical inhibition resulted in complete loss of cell viability. STAT3 inhibition in ESFT cell lines was associated with several consistent changes in chemokine profile suggesting a role of STAT3 in ESFT in both cell survival and modification of the cellular immune environment. Together these data support the investigation of STAT3 inhibitors for the Ewing family of tumors.

Inborn errors of human STAT1: allelic heterogeneity governs the diversity of immunological and infectious phenotypes

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Boisson-Dupuis, Stephanie; Kong, Xiao-Fei; Okada, Satoshi; Cypowyj, Sophie; Puel, Anne; Abel, Laurent; Casanova, Jean-Laurent

2012-01-01

The genetic dissection of various human infectious diseases has led to the definition of inborn errors of human STAT1 immunity of four types, including (i) autosomal recessive (AR) complete STAT1 deficiency, (ii) AR partial STAT1 deficiency, (iii) autosomal dominant (AD) STAT1 deficiency, and (iv) AD gain of STAT1 activity. The two types of AR STAT1 defect give rise to a broad infectious phenotype with susceptibility to intramacrophagic bacteria (mostly mycobacteria) and viruses (herpes viruses at least), due principally to the impairment of IFN-γ-mediated and IFN-α/β-mediated immunity, respectively. Clinical outcome depends on the extent to which the STAT1 defect decreases responsiveness to these cytokines. AD STAT1 deficiency selectively predisposes individuals to mycobacterial disease, owing to the impairment of IFN-γ-mediated immunity, as IFN-α/β-mediated immunity is maintained. Finally, AD gain of STAT1 activity is associated with autoimmunity, probably owing to an enhancement of IFN-α/β-mediated immunity. More surprisingly, it is also associated with chronic mucocutaneous candidiasis, through as yet undetermined mechanisms involving an inhibition of the development of IL-17-producing T cells. Thus, germline mutations in human STAT1 define four distinct clinical disorders. Various combinations of viral, mycobacterial and fungal infections are therefore allelic at the human STAT1 locus. These experiments of Nature neatly highlight the clinical and immunological impact of the human genetic dissection of infectious phenotypes. PMID:22651901

PKCδ phosphorylation is an upstream event of GSK3 inactivation-mediated ROS generation in TGF-β1-induced senescence.

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Byun, H-O; Jung, H-J; Kim, M-J; Yoon, G

2014-09-01

Transforming growth factor β1 (TGF-β1) induces Mv1Lu cell senescence through inactivating glycogen synthase kinase 3 (GSK3), thereby inactivating complex IV and increasing intracellular ROS. In the present study, we identified protein kinase C delta (PKCδ) as an upstream regulator of GSK3 inactivation in this mechanism of TGF-β1-induced senescence. When Mv1Lu cells were exposed to TGF-β1, PKCδ phosphorylation simultaneously increased with GSK3 phosphorylation, and then AKT and ERK were phosphorylated. AKT phosphorylation and Smad signaling were independent of GSK3 phosphorylation, but ERK phosphorylation was downstream of GSK3 inactivation. TGF-β1-triggered GSK3 phosphorylation was blocked by inhibition of PKCδ, using its pharmacological inhibitor, Rottlerin, or overexpression of a dominant negative PKCδ mutant, but GSK3 inhibition with SB415286 did not alter PKCδ phosphorylation. Activation of PKCδ by PMA delayed cell growth and increased intracellular ROS level, but did not induce senescent phenotypes. In addition, overexpression of wild type or a constitutively active PKCδ mutant was enough to delay cell growth and decrease the mitochondrial oxygen consumption rate and complex IV activity, but weakly induce senescence. However, PMA treatment on Mv1Lu cells, which overexpress wild type and constitutively active PKCδ mutants, effectively induced senescence. These results indicate that PKCδ plays a key role in TGF-β1-induced senescence of Mv1Lu cells through the phosphorylation of GSK3, thereby triggering mitochondrial complex IV dysfunction and intracellular ROS generation.

The phosphorylation-dependent regulation of nuclear SREBP1 during mitosis links lipid metabolism and cell growth

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Bengoechea-Alonso, Maria Teresa; Ericsson, Johan

2016-01-01

ABSTRACT The SREBP transcription factors are major regulators of lipid metabolism. Disturbances in lipid metabolism are at the core of several health issues facing modern society, including cardiovascular disease, obesity and diabetes. In addition, the role of lipid metabolism in cancer cell growth is receiving increased attention. Transcriptionally active SREBP molecules are unstable and rapidly degraded in a phosphorylation-dependent manner by Fbw7, a ubiquitin ligase that targets several cell cycle regulatory proteins for degradation. We have previously demonstrated that active SREBP1 is stabilized during mitosis. We have now delineated the mechanisms involved in the stabilization of SREBP1 in mitotic cells. This process is initiated by the phosphorylation of a specific serine residue in nuclear SREBP1 by the mitotic kinase Cdk1. The phosphorylation of this residue creates a docking site for a separate mitotic kinase, Plk1. Plk1 interacts with nuclear SREBP1 in mitotic cells and phosphorylates a number of residues in the C-terminal domain of the protein, including a threonine residue in close proximity of the Fbw7 docking site in SREBP1. The phosphorylation of these residues by Plk1 blocks the interaction between SREBP1 and Fbw7 and attenuates the Fbw7-dependent degradation of nuclear SREBP1 during cell division. Inactivation of SREBP1 results in a mitotic defect, suggesting that SREBP1 could regulate cell division. We propose that the mitotic phosphorylation and stabilization of nuclear SREBP1 during cell division provides a link between lipid metabolism and cell proliferation. Thus, the current study provides additional support for the emerging hypothesis that SREBP-dependent lipid metabolism may be important for cell growth. PMID:27579997

Common γ-chain blocking peptide reduces in vitro immune activation markers in HTLV-1-associated myelopathy/tropical spastic paraparesis.

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Massoud, Raya; Enose-Akahata, Yoshimi; Tagaya, Yutaka; Azimi, Nazli; Basheer, Asjad; Jacobson, Steven

2015-09-01

Human T-cell lymphotropic virus type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a progressive inflammatory myelopathy occurring in a subset of HTLV-1-infected individuals. Despite advances in understanding its immunopathogenesis, an effective treatment remains to be found. IL-2 and IL-15, members of the gamma chain (γc) family of cytokines, are prominently deregulated in HAM/TSP and underlie many of the characteristic immune abnormalities, such as spontaneous lymphocyte proliferation (SP), increased STAT5 phosphorylation in the lymphocytes, and increased frequency and cytotoxicity of virus-specific cytotoxic CD8(+) T lymphocytes (CTLs). In this study, we describe a novel immunomodulatory strategy consisting of selective blockade of certain γc family cytokines, including IL-2 and IL-15, with a γc antagonistic peptide. In vitro, a PEGylated form of the peptide, named BNZ132-1-40, reduced multiple immune activation markers such as SP, STAT5 phosphorylation, spontaneous degranulation of CD8(+) T cells, and the frequency of transactivator protein (Tax)-specific CD8(+) CTLs, thought to be major players in the immunopathogenesis of the disease. This strategy is thus a promising therapeutic approach to HAM/TSP with the potential of being more effective than single monoclonal antibodies targeting either IL-2 or IL-15 receptors and safer than inhibitors of downstream signaling molecules such as JAK1 inhibitors. Finally, selective cytokine blockade with antagonistic peptides might be applicable to multiple other conditions in which cytokines are pathogenic.

Activation of Stat-3 is involved in the induction of apoptosis after ligation of major histocompatibility complex class I molecules on human Jurkat T cells

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Skov, S; Nielsen, M; Bregenholt, S

1998-01-01

Activation of Janus tyrosine kinases (Jak) and Signal transducers and activators of transcription (Stat) after ligation of major histocompatibility complex class I (MHC-I) was explored in Jurkat T cells. Cross-linking of MHC-I mediated tyrosine phosphorylation of Tyk2, but not Jak1, Jak2, and Jak3......-probe derived from the interferon-gamma activated site (GAS) in the c-fos promoter, a common DNA sequence for Stat protein binding. An association between hSIE and Stat-3 after MHC-I ligation was directly demonstrated by precipitating Stat-3 from nuclear extracts with biotinylated hSIE probe and avidin......-coupled agarose. To investigate the function of the activated Stat-3, Jurkat T cells were transiently transfected with a Stat-3 isoform lacking the transactivating domain. This dominant-negative acting Stat-3 isoform significantly inhibited apoptosis induced by ligation of MHC-I. In conclusion, our data suggest...

Quercetin inhibits the poly(dA:dT)-induced secretion of IL-18 via down-regulation of the expressions of AIM2 and pro-caspase-1 by inhibiting the JAK2/STAT1 pathway in IFN-γ-primed human keratinocytes.

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Lee, Kyung-Mi; Kang, Jung Hoon; Yun, Mihee; Lee, Seong-Beom

2018-06-05

Quercetin, a polyphenol, belongs to a class of flavonoids that exerts anti-inflammatory effects. Interleukin (IL)-18 is a member of the IL-1 family cytokine that regulates immune responses and is implicated in various inflammatory skin diseases. Absent in melanoma 2 (AIM2) is a cytosolic double-stranded (ds) DNA sensor that recognizes the dsDNA of a microbial or host origin. Binding of dsDNA to AIM2 simulates caspase-1-dependent inflammasome activity, which leads to the production of IL-1β and IL-18. Increased levels of AIM2 have been observed in patients with inflammatory skin diseases. In the current study, we investigated the issue of whether or how Quercetin attenuates poly (dA:dT), a synthetic analog of microbial dsDNA, -induced IL-18 secretion in IFN-γ-primed human keratinocytes. Treatment with 5 and 10 μM of Quercetin inhibited the poly (dA:dT)-induced secretion of IL-18 after IFN-γ priming and before poly (dA:dT)-induced AIM2 activation. In addition, treatment with Quercetin at 10 μM, significantly inhibited the phosphorylation of JAK2 and STAT1, and the nuclear translocation of phosphorylated STAT1 in poly (dA:dT)-treated and IFN-γ-primed keratinocytes. These results suggest that treatment with Quercetin inhibits the poly (dA:dT)-induced secretion of IL-18 via down-regulation of the expressions of AIM2 and pro-caspase-1 by inhibiting the JAK2/STAT1 pathway in IFN-γ-primed keratinocytes. Copyright © 2018 Elsevier Inc. All rights reserved.

Excess thyroid hormone inhibits embryonic neural stem/progenitor cells proliferation and maintenance through STAT3 signalling pathway.

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Chen, Chunhai; Zhou, Zhou; Zhong, Min; Li, Maoquan; Yang, Xuesen; Zhang, Yanwen; Wang, Yuan; Wei, Aimin; Qu, Mingyue; Zhang, Lei; Xu, Shangcheng; Chen, Shude; Yu, Zhengping

2011-07-01

Hyperthyroidism is prevalent during pregnancy, but little is known about the effects of excess thyroid hormone on the development of embryonic neural stem/progenitor cells (NSCs), and the mechanisms underlying these effects. Previous studies indicate that STAT3 plays a crucial role in determining NSC fate during neurodevelopment. In this study, we investigated the effects of a supraphysiological dose of 3,5,3'-L-triiodothyronine (T3) on the proliferation and maintenance of NSCs derived from embryonic day 13.5 mouse neocortex, and the involvement of STAT3 in this process. Our results suggest that excess T3 treatment inhibits NSC proliferation and maintenance. T3 decreased tyrosine phosphorylation of JAK1, JAK2 and STAT3, and subsequently inhibited STAT3-DNA binding activity. Furthermore, proliferation and maintenance of NSCs were decreased by inhibitors of JAKs and STAT3, indicating that the STAT3 signalling pathway is involved in the process of NSC proliferation and maintenance. Taken together, these results suggest that the STAT3 signalling pathway is involved in the process of T3-induced inhibition of embryonic NSC proliferation and maintenance. These findings provide data for understanding the effects of hyperthyroidism during pregnancy on fetal brain development, and the mechanisms underlying these effects.

Interleukin-1β-induced iNOS expression in human lung carcinoma A549 cells: involvement of STAT and MAPK pathways

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Ravichandran, Kameswaran; Tyagi, Alpna; Deep, Gagan; Agarwal, Chapla; Agarwal, Rajesh

2011-01-01

For understanding of signaling molecules important in lung cancer growth and progression, IL-1β effect was analyzed on iNOS expression and key signaling molecules in human lung carcinoma A549 cells and established the role of specific signaling molecules by using specific chemical inhibitors. IL-1β exposure (10 ng/ml) induced strong iNOS expression in serum starved A549 cells. Detailed molecular analyses showed that IL-1β increased expression of phosphorylated STAT1 (Tyr701 and Ser727) and STAT3 (Tyr705 and Ser727) both in total cell lysates and nuclear lysates. Further, IL-1β exposure strongly activated MAPKs (ERK1/2, JNK1/2 and p38) and Akt as well as increased nuclear levels of NF-κB and HIF-1α in A549 cells. Use of specific chemical inhibitors for JAK1 kinase (piceatannol), JAK2 kinase (AG-490), MEK1/2 (PD98059) and JNK1/2 (SP600125) revealed that IL-1β-induced iNOS expression involved signaling pathways in addition to JAKSTAT and ERK1/2-JNK1/2 activation. Overall, these results suggested that instead of specific pharmacological inhibitors, use of chemopreventive agents with broad spectrum efficacy to inhibit IL-1β-induced signaling cascades and iNOS expression would be a better strategy towards lung cancer prevention and/or treatment. (author)

CK2 phosphorylation of Schistosoma mansoni HMGB1 protein regulates its cellular traffic and secretion but not its DNA transactions.

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de Abreu da Silva, Isabel Caetano; Carneiro, Vitor Coutinho; Maciel, Renata de Moraes; da Costa, Rodrigo Furtado Madeiro; Furtado, Daniel Rodrigues; de Oliveira, Francisco Meirelles Bastos; da Silva-Neto, Mário Alberto Cardoso; Rumjanek, Franklin David; Fantappié, Marcelo Rosado

2011-01-01

The helminth Schistosoma mansoni parasite resides in mesenteric veins where fecundated female worms lay hundred of eggs daily. Some of the egg antigens are trapped in the liver and induce a vigorous granulomatous response. High Mobility Group Box 1 (HMGB1), a nuclear factor, can also be secreted and act as a cytokine. Schistosome HMGB1 (SmHMGB1) is secreted by the eggs and stimulate the production of key cytokines involved in the pathology of schistosomiasis. Thus, understanding the mechanism of SmHMGB1 release becomes mandatory. Here, we addressed the question of how the nuclear SmHMGB1 can reach the extracellular space. We showed in vitro and in vivo that CK2 phosphorylation was involved in the nucleocytoplasmic shuttling of SmHMGB1. By site-directed mutagenesis we mapped the two serine residues of SmHMGB1 that were phosphorylated by CK2. By DNA bending and supercoiling assays we showed that CK2 phosphorylation of SmHMGB1 had no effect in the DNA binding activities of the protein. We showed by electron microscopy, as well as by cell transfection and fluorescence microscopy that SmHMGB1 was present in the nucleus and cytoplasm of adult schistosomes and mammalian cells. In addition, we showed that treatments of the cells with either a phosphatase or a CK2 inhibitor were able to enhance or block, respectively, the cellular traffic of SmHMGB1. Importantly, we showed by confocal microscopy and biochemically that SmHMGB1 is significantly secreted by S. mansoni eggs of infected animals and that SmHMGB1 that were localized in the periovular schistosomotic granuloma were phosphorylated. We showed that secretion of SmHMGB1 is regulated by phosphorylation. Moreover, our results suggest that egg-secreted SmHMGB1 may represent a new egg antigen. Therefore, the identification of drugs that specifically target phosphorylation of SmHMGB1 might block its secretion and interfere with the pathogenesis of schistosomiasis.

CK2 phosphorylation of Schistosoma mansoni HMGB1 protein regulates its cellular traffic and secretion but not its DNA transactions.

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Isabel Caetano de Abreu da Silva

Full Text Available BACKGROUND: The helminth Schistosoma mansoni parasite resides in mesenteric veins where fecundated female worms lay hundred of eggs daily. Some of the egg antigens are trapped in the liver and induce a vigorous granulomatous response. High Mobility Group Box 1 (HMGB1, a nuclear factor, can also be secreted and act as a cytokine. Schistosome HMGB1 (SmHMGB1 is secreted by the eggs and stimulate the production of key cytokines involved in the pathology of schistosomiasis. Thus, understanding the mechanism of SmHMGB1 release becomes mandatory. Here, we addressed the question of how the nuclear SmHMGB1 can reach the extracellular space. PRINCIPAL FINDINGS: We showed in vitro and in vivo that CK2 phosphorylation was involved in the nucleocytoplasmic shuttling of SmHMGB1. By site-directed mutagenesis we mapped the two serine residues of SmHMGB1 that were phosphorylated by CK2. By DNA bending and supercoiling assays we showed that CK2 phosphorylation of SmHMGB1 had no effect in the DNA binding activities of the protein. We showed by electron microscopy, as well as by cell transfection and fluorescence microscopy that SmHMGB1 was present in the nucleus and cytoplasm of adult schistosomes and mammalian cells. In addition, we showed that treatments of the cells with either a phosphatase or a CK2 inhibitor were able to enhance or block, respectively, the cellular traffic of SmHMGB1. Importantly, we showed by confocal microscopy and biochemically that SmHMGB1 is significantly secreted by S. mansoni eggs of infected animals and that SmHMGB1 that were localized in the periovular schistosomotic granuloma were phosphorylated. CONCLUSIONS: We showed that secretion of SmHMGB1 is regulated by phosphorylation. Moreover, our results suggest that egg-secreted SmHMGB1 may represent a new egg antigen. Therefore, the identification of drugs that specifically target phosphorylation of SmHMGB1 might block its secretion and interfere with the pathogenesis of schistosomiasis.

Characterization of STAT3 activation and expression in canine and human osteosarcoma

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Li Pui-Kai

2009-03-01

Full Text Available Abstract Background Dysregulation of signal transducer and activator of transcription 3 (STAT3 has been implicated as a key participant in tumor cell survival, proliferation, and metastasis and is often correlated with a more malignant tumor phenotype. STAT3 phosphorylation has been demonstrated in a subset of human osteosarcoma (OSA tissues and cell lines. OSA in the canine population is known to exhibit a similar clinical behavior and molecular biology when compared to its human counterpart, and is often used as a model for preclinical testing of novel therapeutics. The purpose of this study was to investigate the potential role of STAT3 in canine and human OSA, and to evaluate the biologic activity of a novel small molecule STAT3 inhibitor. Methods To examine STAT3 and Src expression in OSA, we performed Western blotting and RT-PCR. OSA cells were treated with either STAT3 siRNA or small molecule Src (SU6656 or STAT3 (LLL3 inhibitors and cell proliferation (CyQUANT, caspase 3/7 activity (ELISA, apoptosis (Western blotting for PARP cleavage and/or viability (Wst-1 were determined. Additionally, STAT3 DNA binding after treatment was determined using EMSA. Expression of STAT3 targets after treatment was demonstrated with Western blotting, RT-PCR, or gel zymography. Results Our data demonstrate that constitutive activation of STAT3 is present in a subset of canine OSA tumors and human and canine cell lines, but not normal canine osteoblasts. In both canine and human OSA cell lines, downregulation of STAT3 activity through inhibition of upstream Src family kinases using SU6656, inhibition of STAT3 DNA binding and transcriptional activities using LLL3, or modulation of STAT3 expression using siRNA, all resulted in decreased cell proliferation and viability, ultimately inducing caspase-3/7 mediated apoptosis in treated cells. Furthermore, inhibition of either Src or STAT3 activity downregulated the expression of survivin, VEGF, and MMP2, all known

Characterization of STAT3 activation and expression in canine and human osteosarcoma

International Nuclear Information System (INIS)

Fossey, Stacey L; Liao, Albert T; McCleese, Jennifer K; Bear, Misty D; Lin, Jiayuh; Li, Pui-Kai; Kisseberth, William C; London, Cheryl A

2009-01-01

Dysregulation of signal transducer and activator of transcription 3 (STAT3) has been implicated as a key participant in tumor cell survival, proliferation, and metastasis and is often correlated with a more malignant tumor phenotype. STAT3 phosphorylation has been demonstrated in a subset of human osteosarcoma (OSA) tissues and cell lines. OSA in the canine population is known to exhibit a similar clinical behavior and molecular biology when compared to its human counterpart, and is often used as a model for preclinical testing of novel therapeutics. The purpose of this study was to investigate the potential role of STAT3 in canine and human OSA, and to evaluate the biologic activity of a novel small molecule STAT3 inhibitor. To examine STAT3 and Src expression in OSA, we performed Western blotting and RT-PCR. OSA cells were treated with either STAT3 siRNA or small molecule Src (SU6656) or STAT3 (LLL3) inhibitors and cell proliferation (CyQUANT), caspase 3/7 activity (ELISA), apoptosis (Western blotting for PARP cleavage) and/or viability (Wst-1) were determined. Additionally, STAT3 DNA binding after treatment was determined using EMSA. Expression of STAT3 targets after treatment was demonstrated with Western blotting, RT-PCR, or gel zymography. Our data demonstrate that constitutive activation of STAT3 is present in a subset of canine OSA tumors and human and canine cell lines, but not normal canine osteoblasts. In both canine and human OSA cell lines, downregulation of STAT3 activity through inhibition of upstream Src family kinases using SU6656, inhibition of STAT3 DNA binding and transcriptional activities using LLL3, or modulation of STAT3 expression using siRNA, all resulted in decreased cell proliferation and viability, ultimately inducing caspase-3/7 mediated apoptosis in treated cells. Furthermore, inhibition of either Src or STAT3 activity downregulated the expression of survivin, VEGF, and MMP2, all known transcriptional targets of STAT3. These data

Defective interleukin-4/Stat6 activity correlates with increased constitutive expression of negative regulators SOCS-3, SOCS-7, and CISH in colon cancer cells.

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Liu, Xiao Hong; Xu, Shuang Bing; Yuan, Jia; Li, Ben Hui; Zhang, Yan; Yuan, Qin; Li, Pin Dong; Li, Feng; Zhang, Wen Jie

2009-12-01

Interleukin-4 (IL-4)-induced Stat6 activities (phenotypes) vary among human cancer cells, of which the HT-29 cell line carries an active Stat6(high) phenotype, while Caco-2 carries a defective Stat6(null) phenotype, respectively. Cancer cells with Stat6(high) show resistance to apoptosis and exaggerated metastasis, suggesting the clinical significance of Stat6 phenotypes. We previously showed that Stat6(high) HT-29 cells exhibited low constitutive expression of Stat6-negative regulators SOCS-1 and SHP-1 because of gene hypermethylation. This study further examined the constitutive expression of other closely related SOCS family numbers including SOCS-3, SOCS-5, SOCS-7, and CISH using RT-PCR. Similar to SOCS-1 and SHP-1, Stat6(high) HT-29 cells expressed low constitutive mRNA of SOCS-3, SOCS-7, and CISH than Stat6(null) Caco-2 cells. Interestingly, DNA demethylation using 5-aza-2'-deoxycytidine in HT-29 cells up-regulated mRNA expression of the above genes, indicating a hypermethylation status, which was confirmed by methylation-specific sequencing in selected SOCS-3 gene. Furthermore, defective Stat6(null) Caco-2 exhibited impaired phosphorylation of Stat6 after IL-4 stimulation by flow cytometry, in keeping with the notion of an over-performed negative regulation. The findings that IL-4/Stat6 phenotypes show differential expression of multiple negative regulators suggest a model that a collective force of powerful negative regulators, directly and indirectly, acts on Stat6 activation, which may result in differential Stat6 phenotypes.

Inactivation of STAT3 Signaling Impairs Hair Cell Differentiation in the Developing Mouse Cochlea.

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Chen, Qianqian; Quan, Yizhou; Wang, Naitao; Xie, Chengying; Ji, Zhongzhong; He, Hao; Chai, Renjie; Li, Huawei; Yin, Shankai; Chin, Y Eugene; Wei, Xunbin; Gao, Wei-Qiang

2017-07-11

Although STAT3 signaling is demonstrated to regulate sensory cell differentiation and regeneration in the zebrafish, its exact role is still unclear in mammalian cochleae. Here, we report that STAT3 and its activated form are specifically expressed in hair cells during mouse cochlear development. Importantly, conditional cochlear deletion of Stat3 leads to an inhibition on hair cell differentiation in mice in vivo and in vitro. By cell fate analysis, inactivation of STAT3 signaling shifts the cell division modes from asymmetric to symmetric divisions from supporting cells. Moreover, inhibition of Notch signaling stimulates STAT3 phosphorylation, and inactivation of STAT3 signaling attenuates production of supernumerary hair cells induced by a Notch pathway inhibitor. Our findings highlight an important role of the STAT3 signaling during mouse cochlear hair cell differentiation and may have clinical implications for the recovery of hair cell loss-induced hearing impairment. Copyright © 2017 International Society for Stem Cell Research. Published by Elsevier Inc. All rights reserved.

Inactivation of STAT3 Signaling Impairs Hair Cell Differentiation in the Developing Mouse Cochlea

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Qianqian Chen

2017-07-01

Full Text Available Although STAT3 signaling is demonstrated to regulate sensory cell differentiation and regeneration in the zebrafish, its exact role is still unclear in mammalian cochleae. Here, we report that STAT3 and its activated form are specifically expressed in hair cells during mouse cochlear development. Importantly, conditional cochlear deletion of Stat3 leads to an inhibition on hair cell differentiation in mice in vivo and in vitro. By cell fate analysis, inactivation of STAT3 signaling shifts the cell division modes from asymmetric to symmetric divisions from supporting cells. Moreover, inhibition of Notch signaling stimulates STAT3 phosphorylation, and inactivation of STAT3 signaling attenuates production of supernumerary hair cells induced by a Notch pathway inhibitor. Our findings highlight an important role of the STAT3 signaling during mouse cochlear hair cell differentiation and may have clinical implications for the recovery of hair cell loss-induced hearing impairment.

Exercise increases TBC1D1 phosphorylation in human skeletal muscle

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Jessen, Niels; An, Ding; Lihn, Aina S.; Nygren, Jonas; Hirshman, Michael F.; Thorell, Anders

2011-01-01

Exercise and weight loss are cornerstones in the treatment and prevention of type 2 diabetes, and both interventions function to increase insulin sensitivity and glucose uptake into skeletal muscle. Studies in rodents demonstrate that the underlying mechanism for glucose uptake in muscle involves site-specific phosphorylation of the Rab-GTPase-activating proteins AS160 (TBC1D4) and TBC1D1. Multiple kinases, including Akt and AMPK, phosphorylate TBC1D1 and AS160 on distinct residues, regulating their activity and allowing for GLUT4 translocation. In contrast to extensive rodent-based studies, the regulation of AS160 and TBC1D1 in human skeletal muscle is not well understood. In this study, we determined the effects of dietary intervention and a single bout of exercise on TBC1D1 and AS160 site-specific phosphorylation in human skeletal muscle. Ten obese (BMI 33.4 ± 2.4, M-value 4.3 ± 0.5) subjects were studied at baseline and after a 2-wk dietary intervention. Muscle biopsies were obtained from the subjects in the resting (basal) state and immediately following a 30-min exercise bout (70% V̇o2 max). Muscle lysates were analyzed for AMPK activity and Akt phosphorylation and for TBC1D1 and AS160 phosphorylation on known or putative AMPK and Akt sites as follows: AS160 Ser711 (AMPK), TBC1D1 Ser231 (AMPK), TBC1D1 Ser660 (AMPK), TBC1D1 Ser700 (AMPK), and TBC1D1 Thr590 (Akt). The diet intervention that consisted of a major shift in the macronutrient composition resulted in a 4.2 ± 0.4 kg weight loss (P < 0.001) and a significant increase in insulin sensitivity (M value 5.6 ± 0.6), but surprisingly, there was no effect on expression or phosphorylation of any of the muscle-signaling proteins. Exercise increased muscle AMPKα2 activity but did not increase Akt phosphorylation. Exercise increased phosphorylation on AS160 Ser711, TBC1D1 Ser231, and TBC1D1 Ser660 but had no effect on TBC1D1 Ser700. Exercise did not increase TBC1D1 Thr590 phosphorylation or TBC1D1/AS160 PAS

ROS mediates interferon gamma induced phosphorylation of Src, through the Raf/ERK pathway, in MCF-7 human breast cancer cell line.

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Zibara, Kazem; Zeidan, Asad; Bjeije, Hassan; Kassem, Nouhad; Badran, Bassam; El-Zein, Nabil

2017-03-01

Interferon gamma (IFN-ɣ) is a pleiotropic cytokine which plays dual contrasting roles in cancer. Although IFN-ɣ has been clinically used to treat various malignancies, it was recently shown to have protumorigenic activities. Reactive oxygen species (ROS) are overproduced in cancer cells, mainly due to NADPH oxidase activity, which results into several changes in signaling pathways. In this study, we examined IFN-ɣ effect on the phosphorylation levels of key signaling proteins, through ROS production, in the human breast cancer cell line MCF-7. After treatment by IFN-ɣ, results showed a significant increase in the phosphorylation of STAT1, Src, raf, AKT, ERK1/2 and p38 signaling molecules, in a time specific manner. Src and Raf were found to be involved in early stages of IFN-ɣ signaling since their phosphorylation increased very rapidly. Selective inhibition of Src-family kinases resulted in an immediate significant decrease in the phosphorylation status of Raf and ERK1/2, but not p38 and AKT. On the other hand, IFN-ɣ resulted in ROS generation, through H 2 O 2 production, whereas pre-treatment with the ROS inhibitor NAC caused ROS inhibition and a significant decrease in the phosphorylation levels of AKT, ERK1/2, p38 and STAT1. Moreover, pretreatment with a selective NOX1 inhibitor resulted in a significant decrease of AKT phosphorylation. Finally, no direct relationship was found between ROS production and calcium mobilization. In summary, IFN-ɣ signaling in MCF-7 cell line is ROS-dependent and follows the Src/Raf/ERK pathway whereas its signaling through the AKT pathway is highly dependent on NOX1.

2-Methoxy-4-vinylphenol can induce cell cycle arrest by blocking the hyper-phosphorylation of retinoblastoma protein in benzo[a]pyrene-treated NIH3T3 cells

International Nuclear Information System (INIS)

Jeong, Jin Boo; Jeong, Hyung Jin

2010-01-01

Research highlights: → 2M4VP activated the expression of p21 and p15 protein, and down-regulated the expression of cyclin D1 and cyclin E. → 2M4VP inhibited hyper-phosphorylation of Rb protein. → 2M4VP induced cell cycle arrest from G1 to S. → 2M4VP inhibited hyper-proliferation of the cells in BaP-treated cells. → 2M4VP induces growth arrest of BaP-treated cells by blocking hyper-phosphorylation of Rb via regulating the expression of cell cycle-related proteins. -- Abstract: Benzo[a]pyrene (BaP) is an environment carcinogen that can enhance cell proliferation by disturbing the signal transduction pathways in cell cycle regulation. In this study, the effects of 2M4VP on cell proliferation, cell cycle and cell cycle regulatory proteins were studied in BaP-treated NIH 3T3 cells to establish the molecular mechanisms of 2M4VP as anti-proliferative agents. 2M4VP exerted a dose-dependent inhibitory effect on cell growth correlated with a G1 arrest. Analysis of G1 cell cycle regulators expression revealed 2M4VP increased expression of CDK inhibitor, p21Waf1/Cip1 and p15 INK4b, decreased expression of cyclin D1 and cyclin E, and inhibited kinase activities of CDK4 and CDK2. However, 2M4VP did not affect the expression of CDK4 and CDK2. Also, 2M4VP inhibited the hyper-phosphorylation of Rb induced by BaP. Our results suggest that 2M4VP induce growth arrest of BaP-treated NIH 3T3 cells by blocking the hyper-phosphorylation of Rb via regulating the expression of cell cycle-related proteins.

2-Methoxy-4-vinylphenol can induce cell cycle arrest by blocking the hyper-phosphorylation of retinoblastoma protein in benzo[a]pyrene-treated NIH3T3 cells

Energy Technology Data Exchange (ETDEWEB)

Jeong, Jin Boo [Bioresource Sciences, Andong National University, Andong 760749 (Korea, Republic of); Jeong, Hyung Jin, E-mail: jhj@andong.ac.kr [Bioresource Sciences, Andong National University, Andong 760749 (Korea, Republic of)

2010-10-01

Research highlights: {yields} 2M4VP activated the expression of p21 and p15 protein, and down-regulated the expression of cyclin D1 and cyclin E. {yields} 2M4VP inhibited hyper-phosphorylation of Rb protein. {yields} 2M4VP induced cell cycle arrest from G1 to S. {yields} 2M4VP inhibited hyper-proliferation of the cells in BaP-treated cells. {yields} 2M4VP induces growth arrest of BaP-treated cells by blocking hyper-phosphorylation of Rb via regulating the expression of cell cycle-related proteins. -- Abstract: Benzo[a]pyrene (BaP) is an environment carcinogen that can enhance cell proliferation by disturbing the signal transduction pathways in cell cycle regulation. In this study, the effects of 2M4VP on cell proliferation, cell cycle and cell cycle regulatory proteins were studied in BaP-treated NIH 3T3 cells to establish the molecular mechanisms of 2M4VP as anti-proliferative agents. 2M4VP exerted a dose-dependent inhibitory effect on cell growth correlated with a G1 arrest. Analysis of G1 cell cycle regulators expression revealed 2M4VP increased expression of CDK inhibitor, p21Waf1/Cip1 and p15 INK4b, decreased expression of cyclin D1 and cyclin E, and inhibited kinase activities of CDK4 and CDK2. However, 2M4VP did not affect the expression of CDK4 and CDK2. Also, 2M4VP inhibited the hyper-phosphorylation of Rb induced by BaP. Our results suggest that 2M4VP induce growth arrest of BaP-treated NIH 3T3 cells by blocking the hyper-phosphorylation of Rb via regulating the expression of cell cycle-related proteins.

A STAT-1 knockout mouse model for Machupo virus pathogenesis

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Shurtleff Amy C

2011-06-01

Full Text Available Abstract Background Machupo virus (MACV, a member of the Arenaviridae, causes Bolivian hemorrhagic fever, with ~20% lethality in humans. The pathogenesis of MACV infection is poorly understood, and there are no clinically proven treatments for disease. This is due, in part, to a paucity of small animal models for MACV infection in which to discover and explore candidate therapeutics. Methods Mice lacking signal transducer and activator of transcription 1 (STAT-1 were infected with MACV. Lethality, viral replication, metabolic changes, hematology, histopathology, and systemic cytokine expression were analyzed throughout the course of infection. Results We report here that STAT-1 knockout mice succumbed to MACV infection within 7-8 days, and presented some relevant clinical and histopathological manifestations of disease. Furthermore, the model was used to validate the efficacy of ribavirin in protection against infection. Conclusions The STAT-1 knockout mouse model can be a useful small animal model for drug testing and preliminary immunological analysis of lethal MACV infection.

Scutellarin suppresses migration and invasion of human hepatocellular carcinoma by inhibiting the STAT3/Girdin/Akt activity.

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Ke, Yang; Bao, Tianhao; Wu, Xuesong; Tang, Haoran; Wang, Yan; Ge, Jiayun; Fu, Bimang; Meng, Xu; Chen, Li; Zhang, Cheng; Tan, Yuqi; Chen, Haotian; Guo, Zhitang; Ni, Fan; Lei, Xuefen; Shi, Zhitian; Wei, Dong; Wang, Lin

2017-01-29

Scutellarin is an active flavone from Erigeron breviscapine (vant) Hand Mass. This study aimed to investigate the potential role of scutellarin in migration and invasion of human hepatocellular carcinoma (HCC) cells and its possible mechanism. In comparison with the vehicle-treated controls, treatment with scutellarin (50 mg/kg/day) for 35 days significantly mitigated the lung and intrahepatic metastasis of HCC tumors in vivo. Scutellarin treatment significantly reduced HepG2 cell viability in a dose-dependent manner, and inhibited migration and invasion of HCC cells in vitro. Scutellarin treatment significantly reduced STAT3 and Girders of actin filaments (Girdin) expression, STAT3 and Akt phosphorylation in HCC cells. Introduction of STAT3 overexpression restored the scutellarin-downregulated Girdin expression, Akt activation, migration and invasion of HCC cells. Furthermore, induction of Girdin overexpression completely abrogated the inhibition of scutellarin on the Akt phosphorylation, migration and invasion of HCC cells. Scutellarin can inhibit HCC cell metastasis in vivo, and migration and invasion in vitro by down-regulating the STAT3/Girdin/Akt signaling. Copyright © 2016 Elsevier Inc. All rights reserved.

STAT3 signaling pathway is necessary for cell survival and tumorsphere forming capacity in ALDH+/CD133+ stem cell-like human colon cancer cells

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Lin, Li; Fuchs, James; Li, Chenglong; Olson, Veronica; Bekaii-Saab, Tanios; Lin, Jiayuh

2011-01-01

Highlights: ► The phosphorylated or activated form of STAT3 was expressed in colon cancer stem-like cells. ► STAT3 inhibitor, FLLL32 inhibits P-STAT3 and STAT3 target genes in colon cancer stem-like cells. ► Inhibition of STAT3 resulted in decreased cell viability and reduced numbers of tumorspheres. ► STAT3 is required for survival and tumorsphere forming capacity in colon cancer stem-like cells. ► Targeting STAT3 in cancer stem-like cells may offer a novel treatment approach for colon cancer. -- Abstract: Persistent activation of Signal Transducers and Activators of Transcription 3 (STAT3) is frequently detected in colon cancer. Increasing evidence suggests the existence of a small population of colon cancer stem or cancer-initiating cells may be responsible for tumor initiation, metastasis, and resistance to chemotherapy and radiation. Whether STAT3 plays a role in colon cancer-initiating cells and the effect of STAT3 inhibition is still unknown. Flow cytometry was used to isolate colon cancer stem-like cells from three independent human colon cancer cell lines characterized by both aldehyde dehydrogenase (ALDH)-positive and CD133-positive subpopulation (ALDH + /CD133 + ). The effects of STAT3 inhibition in colon cancer stem-like cells were examined. The phosphorylated or activated form of STAT3 was expressed in colon cancer stem-like cells and was reduced by a STAT3-selective small molecular inhibitor, FLLL32. FLLL32 also inhibited the expression of potential STAT3 downstream target genes in colon cancer stem-like cells including survivin, Bcl-XL, as well as Notch-1, -3, and -4, which may be involved in stem cell function. Furthermore, FLLL32 inhibited cell viability and tumorsphere formation as well as induced cleaved caspase-3 in colon cancer stem-like cells. FLLL32 is more potent than curcumin as evidenced with lower IC50 in colon cancer stem-like cells. In summary, our results indicate that STAT3 is a novel therapeutic target in colon cancer stem

Novel mechanism for Fc epsilon RI-mediated signal transducer and activator of transcription 5 (STAT5) tyrosine phosphorylation and the selective influence of STAT5B over mast cell cytokine production

Czech Academy of Sciences Publication Activity Database

Pullen, N.A.; Barnstein, B.O.; Falanga, Y.T.; Wang, Z.Q.; Suzuki, R.; Tamang, T.D.L.; Khurana, M.C.; Harry, E.A.; Dráber, Petr; Bunting, K.D.; Mizuno, K.; Wilson, B.S.; Ryan, J.J.

2012-01-01

Roč. 287, č. 3 (2012), s. 2045-2054 ISSN 0021-9258 R&D Projects: GA MŠk 1M0506; GA ČR GAP302/10/1759; GA ČR GA301/09/1826 Grant - others:NIH(US) 1R01AI59638; NIH(US) R01DK059380; NIH(US) AI051575; NIH(US) GM065794; VCU(US) U19A1077435 Institutional support: RVO:68378050 Keywords : cytokine induction * STAT transcription factor * mast cell * Fyn kinase * STAT5 Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 4.651, year: 2012

STAT3 inhibitor WP1066 as a novel therapeutic agent for bCCI neuropathic pain rats.

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Xue, Zhao-Jing; Shen, Le; Wang, Zhi-Yao; Hui, Shang-Yi; Huang, Yu-Guang; Ma, Chao

2014-10-02

Activation of signal transducer and activator of transcription-3 (STAT3) is suggested to be critically involved in the development of chronic pain, but the complex regulation of STAT3-dependent pathway and the functional significance of inhibiting this pathway during the development of neuropathic pain remain elusive. To evaluate the contribution of the JAK2/STAT3 pathway to neuropathic pain and the potentiality of this pathway as a novel therapeutic target, we examined the effects of the STAT3 inhibitor WP1066 by intrathecal administration in a rat model of bilateral chronic constriction injury (bCCI). The pain behavior tests were performed before the surgery and on postoperative day 3, 7, 14 and 21. L4-L6 dorsal spinal cord were harvested at each time point. Both RT-PCR and Western blot were performed to evaluate the activation of JAK2/STAT3 pathway. To observe the influence of WP1066 on neuropathic pain and its molecular mechanism, WP1066 (10 μl, 10 mmol/L in DMSO) or the same capacity of DMSO as the control were applied through the intrathecal tube on the day before bCCI surgery, and on the postoperative day 3 and 5. Behavioral tests were performed to observe the therapeutic effect on mechanical, thermal and cold hyperalgesia. L4-L6 dorsal spinal cord was harvested on postoperative day fourteen, followed by RT-PCR and Western blot evaluation of the JAK2/STAT3 pathway activation. The mechanical, thermal and cold hyperalgesia of the bCCI rats were significantly decreased when compared with the Sham or the Naïve group at each postoperative time point (PbCCI rats, accompanied by SOCS3 mRNA with a similar tendency. Western blot analysis showed that JAK2 and phosphorylated STAT3 increased significantly since 3 days after bCCI. JAK2 peaked on postoperative day 14 while phosphorylated STAT3 peaked on postoperative day 7 and gradually decreased thereafter and SOCS3׳s peak level on postoperative day 3. When WP1066 were administered intrathecally, the pain behaviors of

Activation of the HMGB1-RAGE axis upregulates TH expression in dopaminergic neurons via JNK phosphorylation.

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Kim, Soo Jeong; Ryu, Min Jeong; Han, Jeongsu; Jang, Yunseon; Kim, Jungim; Lee, Min Joung; Ryu, Ilhwan; Ju, Xianshu; Oh, Eungseok; Chung, Woosuk; Kweon, Gi Ryang; Heo, Jun Young

2017-11-04

The derangement of tyrosine hydroxylase (TH) activity reduces dopamine synthesis and is implicated in the pathogenesis of Parkinson's disease. However, the extracellular modulator and intracellular regulatory mechanisms of TH have yet to be identified. Recently, high-mobility group box 1 (HMGB1) was reported to be actively secreted from glial cells and is regarded as a mediator of dopaminergic neuronal loss. However, the mechanism for how HMGB1 affects TH expression, particularly through the receptor for advanced glycation endproducts (RAGE), has not yet been investigated. We found that recombinant HMGB1 (rHMGB1) upregulates TH mRNA expression via simultaneous activation of JNK phosphorylation, and this induction of TH expression is blocked by inhibitors of RAGE and JNK. To investigate how TH expression levels change through the HMGB1-RAGE axis as a result of MPP + toxicity, we co-treated SN4741 dopaminergic cells with MPP + and rHMGB1. rHMGB1 blocked the reduction of TH mRNA following MPP + treatment without altering cell survival rates. Our results suggest that HMGB1 upregulates TH expression to maintain dopaminergic neuronal function via activating RAGE, which is dependent on JNK phosphorylation. Copyright © 2017 Elsevier Inc. All rights reserved.

Cdk1 Phosphorylates Drosophila Sas-4 to Recruit Polo to Daughter Centrioles and Convert Them to Centrosomes.

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Novak, Zsofia A; Wainman, Alan; Gartenmann, Lisa; Raff, Jordan W

2016-06-20

Centrosomes and cilia are organized by a centriole pair comprising an older mother and a younger daughter. Centriole numbers are tightly regulated, and daughter centrioles (which assemble in S phase) cannot themselves duplicate or organize centrosomes until they have passed through mitosis. It is unclear how this mitotic "centriole conversion" is regulated, but it requires Plk1/Polo kinase. Here we show that in flies, Cdk1 phosphorylates the conserved centriole protein Sas-4 during mitosis. This creates a Polo-docking site that helps recruit Polo to daughter centrioles and is required for the subsequent recruitment of Asterless (Asl), a protein essential for centriole duplication and mitotic centrosome assembly. Point mutations in Sas-4 that prevent Cdk1 phosphorylation or Polo docking do not block centriole disengagement during mitosis, but block efficient centriole conversion and lead to embryonic lethality. These observations can explain why daughter centrioles have to pass through mitosis before they can duplicate and organize a centrosome. Copyright © 2016 The Author(s). Published by Elsevier Inc. All rights reserved.

A natural product-like JAK2/STAT3 inhibitor induces apoptosis of malignant melanoma cells.

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Ke-Jia Wu

Full Text Available The JAK2/STAT3 signaling pathway plays a critical role in tumorigenesis, and has been suggested as a potential molecular target for anti-melanoma therapeutics. However, few JAK2 inhibitors were being tested for melanoma therapy. In this study, eight amentoflavone analogues were evaluated for their activity against human malignant melanoma cells. The most potent analogue, compound 1, inhibited the phosphorylation of JAK2 and STAT3 in human melanoma cells, but had no discernible effect on total JAK2 and STAT3 levels. A cellular thermal shift assay was performed to identify that JAK2 is engaged by 1 in cell lysates. Moreover, compound 1 showed higher antiproliferative activity against human melanoma A375 cells compared to a panel of cancer and normal cell lines. Compound 1 also activated caspase-3 and cleaved PARP, which are markers of apoptosis, and suppressed the anti-apoptotic Bcl-2 level. Finally, compound 1 induced apoptosis in 80% of treated melanoma cells. To our knowledge, compound 1 is the first amentoflavone-based JAK2 inhibitor to be investigated for use as an anti-melanoma agent.

IL4I1 Is a Novel Regulator of M2 Macrophage Polarization That Can Inhibit T Cell Activation via L-Tryptophan and Arginine Depletion and IL-10 Production.

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Yinpu Yue

Full Text Available Interleukin 4-induced gene-1 (IL4I1 was initially described as an early IL-4-inducible gene in B cells. IL4I1 protein can inhibit T cell proliferation by releasing its enzymatic catabolite, H2O2, and this effect is associated with transient down-regulation of T cell CD3 receptor-zeta (TCRζ expression. Herein, we show that IL4I1 contributes to the regulation of macrophage programming. We found that expression of IL4I1 increased during bone marrow-derived macrophage (BMDM differentiation, expression of IL4I1 is much higher in primary macrophages than monocytes, and IL4I1 expression in BMDMs could be induced by Th1 and Th2 cytokines in two different patterns. Gene expression analysis revealed that overexpression of IL4I1 drove the expression of M2 markers (Fizz1, Arg1, YM-1, MR and inhibited the expression of M1-associated cytokines. Conversely, knockdown of IL4I1 by siRNA resulted in opposite effects, and also attenuated STAT-3 and STAT-6 phosphorylation. Furthermore, IL4I1 produced by macrophages catalyzed L-tryptophan degradation, while levo-1-methyl-tryptophan (L-1-MT, but not dextro-1-methyl-tryptophan, partially rescued IL4I1-dependent inhibition of T cell activation. Other inhibitors, such as diphenylene iodonium (DPI, an anti-IL-10Rα blocking antibody, and a nitric oxide synthase inhibitor, NG-monomethyl-L-arginine, also had this effect. Overall, our findings indicate that IL4I1 promotes an enhanced M2 functional phenotype, which is most likely associated with the phosphorylation of STAT-6 and STAT-3. Moreover, DPI, L-1-MT, NG-monomethyl-L-arginine, and anti-IL-10Rα blocking antibody were all found to be effective IL4I1 inhibitors in vitro.

Identifying mechanisms by which Escherichia coli O157:H7 subverts interferon-γ mediated signal transducer and activator of transcription-1 activation.

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Nathan K Ho

Full Text Available Enterohemorrhagic Escherichia coli serotype O157:H7 is a food borne enteric bacterial pathogen that causes significant morbidity and mortality in both developing and industrialized nations. E. coli O157:H7 infection of host epithelial cells inhibits the interferon gamma pro-inflammatory signaling pathway, which is important for host defense against microbial pathogens, through the inhibition of Stat-1 tyrosine phosphorylation. The aim of this study was to determine which bacterial factors are involved in the inhibition of Stat-1 tyrosine phosphorylation. Human epithelial cells were challenged with either live bacteria or bacterial-derived culture supernatants, stimulated with interferon-gamma, and epithelial cell protein extracts were then analyzed by immunoblotting. The results show that Stat-1 tyrosine phosphorylation was inhibited by E. coli O157:H7 secreted proteins. Using sequential anion exchange and size exclusion chromatography, YodA was identified, but not confirmed to mediate subversion of the Stat-1 signaling pathway using isogenic mutants. We conclude that E. coli O157:H7 subverts Stat-1 tyrosine phosphorylation in response to interferon-gamma through a still as yet unidentified secreted bacterial protein.

The Synthetic α-Bromo-2′,3,4,4′-Tetramethoxychalcone (α-Br-TMC) Inhibits the JAK/STAT Signaling Pathway

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Brueggemann, Susanne; Besl, Elisabeth; Al-Rifai, Nafisah; Petkes, Hermina; Amslinger, Sabine; Rascle, Anne

2014-01-01

Signal transducer and activator of transcription STAT5 and its upstream activating kinase JAK2 are essential mediators of cytokine signaling. Their activity is normally tightly regulated and transient. However, constitutive activation of STAT5 is found in numerous cancers and a driving force for malignant transformation. We describe here the identification of the synthetic chalcone α-Br-2′,3,4,4′-tetramethoxychalcone (α-Br-TMC) as a novel JAK/STAT inhibitor. Using the non-transformed IL-3-dependent B cell line Ba/F3 and its oncogenic derivative Ba/F3-1*6 expressing constitutively activated STAT5, we show that α-Br-TMC targets the JAK/STAT pathway at multiple levels, inhibiting both JAK2 and STAT5 phosphorylation. Moreover, α-Br-TMC alters the mobility of STAT5A/B proteins in SDS-PAGE, indicating a change in their post-translational modification state. These alterations correlate with a decreased association of STAT5 and RNA polymerase II with STAT5 target genes in chromatin immunoprecipitation assays. Interestingly, expression of STAT5 target genes such as Cis and c-Myc was differentially regulated by α-Br-TMC in normal and cancer cells. While both genes were inhibited in IL-3-stimulated Ba/F3 cells, expression of the oncogene c-Myc was down-regulated and that of the tumor suppressor gene Cis was up-regulated in transformed Ba/F3-1*6 cells. The synthetic chalcone α-Br-TMC might therefore represent a promising novel anticancer agent for therapeutic intervention in STAT5-associated malignancies. PMID:24595334

Autophagy Facilitates IFN-γ-induced Jak2-STAT1 Activation and Cellular Inflammation*

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Chang, Yu-Ping; Tsai, Cheng-Chieh; Huang, Wei-Ching; Wang, Chi-Yun; Chen, Chia-Ling; Lin, Yee-Shin; Kai, Jui-In; Hsieh, Chia-Yuan; Cheng, Yi-Lin; Choi, Pui-Ching; Chen, Shun-Hua; Chang, Shih-Ping; Liu, Hsiao-Sheng; Lin, Chiou-Feng

2010-01-01

Autophagy is regulated for IFN-γ-mediated antimicrobial efficacy; however, its molecular effects for IFN-γ signaling are largely unknown. Here, we show that autophagy facilitates IFN-γ-activated Jak2-STAT1. IFN-γ induces autophagy in wild-type but not in autophagy protein 5 (Atg5−/−)-deficient mouse embryonic fibroblasts (MEFs), and, autophagy-dependently, IFN-γ induces IFN regulatory factor 1 and cellular inflammatory responses. Pharmacologically inhibiting autophagy using 3-methyladenine, a known inhibitor of class III phosphatidylinositol 3-kinase, confirms these effects. Either Atg5−/− or Atg7−/− MEFs are, independent of changes in IFN-γ receptor expression, resistant to IFN-γ-activated Jak2-STAT1, which suggests that autophagy is important for IFN-γ signal transduction. Lentivirus-based short hairpin RNA for Atg5 knockdown confirmed the importance of autophagy for IFN-γ-activated STAT1. Without autophagy, reactive oxygen species increase and cause SHP2 (Src homology-2 domain-containing phosphatase 2)-regulated STAT1 inactivation. Inhibiting SHP2 reversed both cellular inflammation and the IFN-γ-induced activation of STAT1 in Atg5−/− MEFs. Our study provides evidence that there is a link between autophagy and both IFN-γ signaling and cellular inflammation and that autophagy, because it inhibits the expression of reactive oxygen species and SHP2, is pivotal for Jak2-STAT1 activation. PMID:20592027

Egr2 enhances insulin resistance via JAK2/STAT3/SOCS-1 pathway in HepG2 cells treated with palmitate.

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Lu, Lin; Ye, Xinhua; Yao, Qing; Lu, Aijiao; Zhao, Zhen; Ding, Yang; Meng, Chuchen; Yu, Wenlong; Du, Yunfeng; Cheng, JinLuo

2018-05-01

Insulin resistance is generally responsible for the pathogenesis of type 2 diabetes mellitus (T2DM). Early growth response proteins-2 (Egr2) has been reported to be able to increase the expression of the suppressors of cytokine signaling-1 (SOCS-1), and impair insulin signaling pathway through suppression of insulin receptor substrates (IRS), including IRS-1 and IRS-2. However, whether Egr2 is directly involved in the development of insulin resistance, and how its potential contributions to insulin resistance still remain unknown. Here, our present investigation found that the expression levels of Egr2 were up-regulated when insulin resistance occurs, and knockdown of Egr2 abolished the effect of insulin resistance in HepG2 cells induced with palmitate (PA). Importantly, inhibition of Egr2 decreased the expression of SOCS-1 as well as reduced phosphorylation of JAK2 and STAT3. And, our data indicated that silencing of Egr2 accelerated hepatic glucose uptake and reversed the impaired lipid metabolism upon insulin resistance. In summary, the present study confirms that Egr2 could deteriorate insulin resistance via the pathway of JAK2/STAT3/SOCS-1 and may shed light on resolving insulin resistance and further the pathogenesis of T2DM. Copyright © 2017 Elsevier Inc. All rights reserved.

Exercise Inhibits the Effects of Smoke-Induced COPD Involving Modulation of STAT3

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Maysa Alves Rodrigues Brandao-Rangel

2017-01-01

Full Text Available Purpose. Evaluate the participation of STAT3 in the effects of aerobic exercise (AE in a model of smoke-induced COPD. Methods. C57Bl/6 male mice were divided into control, Exe, COPD, and COPD+Exe groups. Smoke were administered during 90 days. Treadmill aerobic training begun on day 61 until day 90. Pulmonary inflammation, systemic inflammation, the level of lung emphysema, and the airway remodeling were evaluated. Analysis of integral and phosphorylated expression of STAT3 by airway epithelial cells, peribronchial leukocytes, and parenchymal leukocytes was performed. Results. AE inhibited smoke-induced accumulation of total cells (p<0.001, lymphocytes (p<0.001, and neutrophils (p<0.001 in BAL, as well as BAL levels of IL-1β (p<0.001, CXCL1 (p<0.001, IL-17 (p<0.001, and TNF-α (p<0.05, while increased the levels of IL-10 (p<0.001. AE also inhibited smoke-induced increases in total leukocytes (p<0.001, neutrophils (p<0.05, lymphocytes (p<0.001, and monocytes (p<0.01 in blood, as well as serum levels of IL-1β (p<0.01, CXCL1 (p<0.01, IL-17 (p<0.05, and TNF-α (p<0.01, while increased the levels of IL-10 (p<0.001. AE reduced smoke-induced emphysema (p<0.001 and collagen fiber accumulation in the airways (p<0.001. AE reduced smoke-induced STAT3 and phospho-STAT3 expression in airway epithelial cells (p<0.001, peribronchial leukocytes (p<0.001, and parenchymal leukocytes (p<0.001. Conclusions. AE reduces smoke-induced COPD phenotype involving STAT3.

Identification of novel small molecules that inhibit STAT3-dependent transcription and function.

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Iryna Kolosenko

Full Text Available Activation of Signal Transducer and Activator of Transcription 3 (STAT3 has been linked to several processes that are critical for oncogenic transformation, cancer progression, cancer cell proliferation, survival, drug resistance and metastasis. Inhibition of STAT3 signaling has shown a striking ability to inhibit cancer cell growth and therefore, STAT3 has become a promising target for anti-cancer drug development. The aim of this study was to identify novel inhibitors of STAT-dependent gene transcription. A cellular reporter-based system for monitoring STAT3 transcriptional activity was developed which was suitable for high-throughput screening (Z' = 0,8. This system was used to screen a library of 28,000 compounds (the ENAMINE Drug-Like Diversity Set. Following counter-screenings and toxicity studies, we identified four hit compounds that were subjected to detailed biological characterization. Of the four hits, KI16 stood out as the most promising compound, inhibiting STAT3 phosphorylation and transcriptional activity in response to IL6 stimulation. In silico docking studies showed that KI16 had favorable interactions with the STAT3 SH2 domain, however, no inhibitory activity could be observed in the STAT3 fluorescence polarization assay. KI16 inhibited cell viability preferentially in STAT3-dependent cell lines. Taken together, using a targeted, cell-based approach, novel inhibitors of STAT-driven transcriptional activity were discovered which are interesting leads to pursue further for the development of anti-cancer therapeutic agents.

Sonic Hedgehog dependent phosphorylation by CK1α and GRK2 is required for ciliary accumulation and activation of smoothened.

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Yongbin Chen

2011-06-01

Full Text Available Hedgehog (Hh signaling regulates embryonic development and adult tissue homeostasis through the GPCR-like protein Smoothened (Smo, but how vertebrate Smo is activated remains poorly understood. In Drosophila, Hh dependent phosphorylation activates Smo. Whether this is also the case in vertebrates is unclear, owing to the marked sequence divergence between vertebrate and Drosophila Smo (dSmo and the involvement of primary cilia in vertebrate Hh signaling. Here we demonstrate that mammalian Smo (mSmo is activated through multi-site phosphorylation of its carboxyl-terminal tail by CK1α and GRK2. Phosphorylation of mSmo induces its active conformation and simultaneously promotes its ciliary accumulation. We demonstrate that graded Hh signals induce increasing levels of mSmo phosphorylation that fine-tune its ciliary localization, conformation, and activity. We show that mSmo phosphorylation is induced by its agonists and oncogenic mutations but is blocked by its antagonist cyclopamine, and efficient mSmo phosphorylation depends on the kinesin-II ciliary motor. Furthermore, we provide evidence that Hh signaling recruits CK1α to initiate mSmo phosphorylation, and phosphorylation further increases the binding of CK1α and GRK2 to mSmo, forming a positive feedback loop that amplifies and/or sustains mSmo phosphorylation. Hence, despite divergence in their primary sequences and their subcellular trafficking, mSmo and dSmo employ analogous mechanisms for their activation.

IGF-1 induces the epithelial-mesenchymal transition via Stat5 in hepatocellular carcinoma.

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Zhao, Chuanzong; Wang, Qian; Wang, Ben; Sun, Qi; He, Zhaobin; Hong, Jianguo; Kuehn, Florian; Liu, Enyu; Zhang, Zongli

2017-12-19

It has been reported that the epithelial-mesenchymal transition (EMT) plays an important role in hepatocellular carcinoma (HCC). However, the relationship between the insulin-like growth factor-1 (IGF-1) and EMT of HCC was not fully elucidated. In the present work, we found that the expression of N-cadherin, Vimentin, Snail1, Snail2, and Twist1 was positively associated with IGF-1R expression, while E-cadherin expression was negatively associated with IGF-1 expression in human HCC samples. Furthermore, we observed that IGF-1 up-regulated the expression of N-cadherin, Vimentin, Snail1, Snail2 and Twist1, and down-regulated the expression of E-cadherin. In addition, Stat5 was induced in IGF-1-treated HepG2 and Hep3B cells, and Stat5 inhibition or siRNA significantly affected IGF-1-induced EMT in HepG2 and Hep3B cells. In conclusion, IGF-1 induces EMT of HCC via Stat5 signaling pathway. Thus, IGF-1/Stat5 can be recommended as a potential and novel therapeutic strategy for HCC patients.

Correlation of STATs family expression in oral lichen planus tissue with peripheral blood PD-1 and PD-L1 expression as well as immune function

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Hong Zhang

2016-12-01

Full Text Available Objective: To study the correlation of STATs family expression in oral lichen planus tissue with peripheral blood PD-1 and PD-L1 expression as well as immune function. Methods: A total of 47 patients diagnosed with oral lichen planus in our hospital between May 2015 and March 2016 were selected as the oral lichen planus group (OLP group of the study, and healthy volunteers receiving physical examination during the same period were selected as the control group of the study. Peripheral blood mononuclear cells were collected to detect the expression of PD-1, PD-L1 and immune cell surface marker molecules, serum was collected to detect the content of Th1 and Th2 cytokines as well as immunoglobulin, and oral lichen planus lesion tissue and adjacent normal tissue were collected to determine STATs family expression. Results: p-STAT1, p-STAT3 and p-STAT5a expression in lesion tissue were significantly higher than those in normal tissue while p-STAT2, p-STAT4 and p-STAT5b expression were not significantly different from those in normal tissue; PD-1 and PD-L1 mRNA expression as well as the mean fluorescence intensity of CD19+ in peripheral blood mononuclear cells of OLP group were significantly higher than those of control group and positively correlated with p-STAT1, p-STAT3 and p-STAT5a expression while the mean fluorescence intensity of CD3+, CD4+, CD8+ and CD16+CD56+ were significantly lower than those of control group and negatively correlated with p-STAT1, p-STAT3 and p-STAT5a expression; serum IFN-γ and IL-2 content of OLP group were significantly lower than those of control group and negatively correlated with p-STAT1, p-STAT3 and p-STAT5a expression while IL-4, IL-10, IgG, IgM and IgA content were significantly higher than those of control group and positively correlated with p-STAT1, p-STAT3 and p-STAT5a expression. Conclusion: p-STAT1, p-STAT3 and p-STAT5a expression abnormally increase in oral lichen planus tissues, and the Th1/Th2 cellular

STAT3 signaling pathway is necessary for cell survival and tumorsphere forming capacity in ALDH{sup +}/CD133{sup +} stem cell-like human colon cancer cells

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Lin, Li, E-mail: lin.796@osu.edu [Center for Childhood Cancer, The Research Institute at Nationwide Children' s Hospital, Department of Pediatrics, Internal Medicine, College of Medicine, The Ohio State University, Columbus, OH 43205 (United States); Division of Cardiology, Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030 (China); Fuchs, James; Li, Chenglong [Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, The Ohio State University, Columbus, OH 43210 (United States); Olson, Veronica [Center for Childhood Cancer, The Research Institute at Nationwide Children' s Hospital, Department of Pediatrics, Internal Medicine, College of Medicine, The Ohio State University, Columbus, OH 43205 (United States); Bekaii-Saab, Tanios [Internal Medicine, College of Medicine, The Ohio State University, Columbus, OH 43210 (United States); Lin, Jiayuh, E-mail: lin.674@osu.edu [Center for Childhood Cancer, The Research Institute at Nationwide Children' s Hospital, Department of Pediatrics, Internal Medicine, College of Medicine, The Ohio State University, Columbus, OH 43205 (United States)

2011-12-16

Highlights: Black-Right-Pointing-Pointer The phosphorylated or activated form of STAT3 was expressed in colon cancer stem-like cells. Black-Right-Pointing-Pointer STAT3 inhibitor, FLLL32 inhibits P-STAT3 and STAT3 target genes in colon cancer stem-like cells. Black-Right-Pointing-Pointer Inhibition of STAT3 resulted in decreased cell viability and reduced numbers of tumorspheres. Black-Right-Pointing-Pointer STAT3 is required for survival and tumorsphere forming capacity in colon cancer stem-like cells. Black-Right-Pointing-Pointer Targeting STAT3 in cancer stem-like cells may offer a novel treatment approach for colon cancer. -- Abstract: Persistent activation of Signal Transducers and Activators of Transcription 3 (STAT3) is frequently detected in colon cancer. Increasing evidence suggests the existence of a small population of colon cancer stem or cancer-initiating cells may be responsible for tumor initiation, metastasis, and resistance to chemotherapy and radiation. Whether STAT3 plays a role in colon cancer-initiating cells and the effect of STAT3 inhibition is still unknown. Flow cytometry was used to isolate colon cancer stem-like cells from three independent human colon cancer cell lines characterized by both aldehyde dehydrogenase (ALDH)-positive and CD133-positive subpopulation (ALDH{sup +}/CD133{sup +}). The effects of STAT3 inhibition in colon cancer stem-like cells were examined. The phosphorylated or activated form of STAT3 was expressed in colon cancer stem-like cells and was reduced by a STAT3-selective small molecular inhibitor, FLLL32. FLLL32 also inhibited the expression of potential STAT3 downstream target genes in colon cancer stem-like cells including survivin, Bcl-XL, as well as Notch-1, -3, and -4, which may be involved in stem cell function. Furthermore, FLLL32 inhibited cell viability and tumorsphere formation as well as induced cleaved caspase-3 in colon cancer stem-like cells. FLLL32 is more potent than curcumin as evidenced with lower

JAK/STAT-1 Signaling Is Required for Reserve Intestinal Stem Cell Activation during Intestinal Regeneration Following Acute Inflammation

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Camilla A. Richmond

2018-01-01

Full Text Available The intestinal epithelium serves as an essential barrier to the outside world and is maintained by functionally distinct populations of rapidly cycling intestinal stem cells (CBC ISCs and slowly cycling, reserve ISCs (r-ISCs. Because disruptions in the epithelial barrier can result from pathological activation of the immune system, we sought to investigate the impact of inflammation on ISC behavior during the regenerative response. In a murine model of αCD3 antibody-induced small-intestinal inflammation, r-ISCs proved highly resistant to injury, while CBC ISCs underwent apoptosis. Moreover, r-ISCs were induced to proliferate and functionally contribute to intestinal regeneration. Further analysis revealed that the inflammatory cytokines interferon gamma and tumor necrosis factor alpha led to r-ISC activation in enteroid culture, which could be blocked by the JAK/STAT inhibitor, tofacitinib. These results highlight an important role for r-ISCs in response to acute intestinal inflammation and show that JAK/STAT-1 signaling is required for the r-ISC regenerative response.

Acetylation within the N- and C-Terminal Domains of Src Regulates Distinct Roles of STAT3-Mediated Tumorigenesis.

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Huang, Chao; Zhang, Zhe; Chen, Lihan; Lee, Hank W; Ayrapetov, Marina K; Zhao, Ting C; Hao, Yimei; Gao, Jinsong; Yang, Chunzhang; Mehta, Gautam U; Zhuang, Zhengping; Zhang, Xiaoren; Hu, Guohong; Chin, Y Eugene

2018-06-01

Posttranslational modifications of mammalian c-Src N-terminal and C-terminal domains regulate distinct functions. Myristoylation of G 2 controls its cell membrane association and phosphorylation of Y419/Y527 controls its activation or inactivation, respectively. We provide evidence that Src-cell membrane association-dissociation and catalytic activation-inactivation are both regulated by acetylation. In EGF-treated cells, CREB binding protein (CBP) acetylates an N-terminal lysine cluster (K5, K7, and K9) of c-Src to promote dissociation from the cell membrane. CBP also acetylates the C-terminal K401, K423, and K427 of c-Src to activate intrinsic kinase activity for STAT3 recruitment and activation. N-terminal domain phosphorylation (Y14, Y45, and Y68) of STAT3 by c-Src activates transcriptionally active dimers of STAT3. Moreover, acetyl-Src translocates into nuclei, where it forms the Src-STAT3 enhanceosome for gene regulation and cancer cell proliferation. Thus, c-Src acetylation in the N-terminal and C-terminal domains play distinct roles in Src activity and regulation. Significance: CBP-mediated acetylation of lysine clusters in both the N-terminal and C-terminal regions of c-Src provides additional levels of control over STAT3 transcriptional activity. Cancer Res; 78(11); 2825-38. ©2018 AACR . ©2018 American Association for Cancer Research.

Activation of the protein tyrosine phosphatase SHP2 via the interleukin-6 signal transducing receptor protein gp130 requires tyrosine kinase Jak1 and limits acute-phase protein expression.

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Schaper, F; Gendo, C; Eck, M; Schmitz, J; Grimm, C; Anhuf, D; Kerr, I M; Heinrich, P C

1998-11-01

Stimulation of the interleukin-6 (IL-6) signalling pathway occurs via the IL-6 receptor-glycoprotein 130 (IL-6R-gp130) receptor complex and results in the regulation of acute-phase protein genes in liver cells. Ligand binding to the receptor complex leads to tyrosine phosphorylation and activation of Janus kinases (Jak), phosphorylation of the signal transducing subunit gp130, followed by recruitment and phosphorylation of the signal transducer and activator of transcription factors STAT3 and STAT1 and the src homology domain (SH2)-containing protein tyrosine phosphatase (SHP2). The tyrosine phosphorylated STAT factors dissociate from the receptor, dimerize and translocate to the nucleus where they bind to enhancer sequences of IL-6 target genes. Phosphorylated SHP2 is able to bind growth factor receptor bound protein (grb2) and thus might link the Jak/STAT pathway to the ras/raf/mitogen-activated protein kinase pathway. Here we present data on the dose-dependence, kinetics and kinase requirements for SHP2 phosphorylation after the activation of the signal transducer, gp130, of the IL-6-type family receptor complex. When human fibrosarcoma cell lines deficient in Jak1, Jak2 or tyrosine kinase 2 (Tyk2) were stimulated with IL-6-soluble IL-6R complexes it was found that only in Jak1-, but not in Jak 2- or Tyk2-deficient cells, SHP2 activation was greatly impaired. It is concluded that Jak1 is required for the tyrosine phosphorylation of SHP2. This phosphorylation depends on Tyr-759 in the cytoplasmatic domain of gp130, since a Tyr-759-->Phe exchange abrogates SHP2 activation and in turn leads to elevated and prolonged STAT3 and STAT1 activation as well as enhanced acute-phase protein gene induction. Therefore, SHP2 plays an important role in acute-phase gene regulation.