scholarly journals Salicylate-enhanced activation of transcription factors induced by interferon-γ

1999 ◽  
Vol 342 (3) ◽  
pp. 503-507 ◽  
Author(s):  
Li-Chun CHEN ◽  
Diane KEPKA-LENHART ◽  
Timothy M. WRIGHT ◽  
Sidney M. MORRIS
Keyword(s):  
Transcription Factors ◽  
Protein Tyrosine Phosphatase ◽  
Tyrosine Phosphatase ◽  
Interferon Γ ◽  
Janus Kinase ◽  
Macrophage Cell ◽  
Cellular Targets ◽  
Nuclear Extracts ◽  
Interferon Regulatory Factor 1 ◽  
Activation Of Transcription

Salicylate enhanced the interferon-γ-dependent activation of two transcription factors in a murine macrophage cell line: signal transducer and activator of transcription (STAT)1 and interferon-γ-responsive factor 1. Salicylate alone did not activate these transcription factors. This enhancement was reflected by increased DNA-binding activities and was the consequence of prolonged tyrosine phosphorylation of these transcription factors following interferon-γ treatment. However, salicylate did not directly inhibit protein-tyrosine phosphatase activity in nuclear extracts of interferon-γ-treated cells. The enhanced activation of STAT1 resulted in increased induction of mRNA encoding interferon regulatory factor-1. These results not only demonstrate that aspirin and its metabolite salicylate may have pro-inflammatory as well as anti-inflammatory effects but also raise the possibility that new cellular targets may be identified for modulating the Janus kinase-STAT signalling pathway.

New mimetic peptides of the kinase-inhibitory region (KIR) of SOCS1 through focused peptide libraries

2012 ◽  
Vol 443 (1) ◽  
pp. 231-240 ◽  
Author(s):  
Nunzianna Doti ◽  
Pasqualina L. Scognamiglio ◽  
Stefania Madonna ◽  
Claudia Scarponi ◽  
Menotti Ruvo ◽  
...  
Keyword(s):  
Interferon Γ ◽  
Catalytic Site ◽  
Janus Kinase ◽  
Scanning Method ◽  
Expression Levels ◽  
Interferon Regulatory Factor 1 ◽  
Inhibitory Region ◽  
Inflammatory Processes ◽  
Cytokine Stimulation ◽  
Kinase Inhibitory Region

SOCS (suppressor of cytokine signalling) proteins are negative-feedback regulators of the JAK (Janus kinase)/STAT (signal transducer and activator of transcription) pathway. Their expression levels are low under physiological conditions, but they are up-regulated in response to cytokine stimulation in many immune and inflammatory processes. Overexpression of SOCS1 in keratinocyte clones abrogates the IFNγ (interferon γ)-induced expression of many pro-inflammatory genes and the release of related chemokines by blocking the JAK/STAT pathway. SOCS1 inhibits JAK2 kinase activity by binding the catalytic site of JAK2, with its KIR (kinase-inhibitory region) acting as a pseudo-substrate of the enzyme. In the present study, we screened a focused combinatorial peptide library of KIR to identify new peptides able to mimic its function with an improved affinity towards the JAK2 catalytic site. Using an alanine-scanning method, KIR residues that are crucial for the interaction with JAK2 were unveiled. In this way, the KIR sequence was restricted to a shorter segment and ‘non-essential’ residues were replaced by different amino acids following a simplified combinatorial approach. We selected a new unnatural sequence able to bind to JAK2 with Kd values in the nanomolar range. This peptide was tested in human keratinocyte cultures and reduced the phosphorylation of STAT1 and the expression levels of IRF-1 (interferon regulatory factor-1).

Deletion of the Protein Tyrosine Phosphatase Gene PTPN2 in T-Cell Acute Lymphoblastic Leukemia.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 141-141
Author(s):  
Maria Kleppe ◽  
Idoya Lahortiga ◽  
Tiama El Chaar ◽  
Kim De Keersmaecker ◽  
Nicole Mentens ◽  
...  
Keyword(s):  
T Cell ◽  
Cell Lines ◽  
Protein Tyrosine Phosphatase ◽  
Lymphoblastic Leukemia ◽  
Tyrosine Phosphatase ◽  
Janus Kinase ◽  
Negative Regulator ◽  
Aberrant Expression ◽  
Protein Tyrosine ◽  
Knock Down

Abstract Abstract 141 Introduction: T-cell lymphoblastic leukemia (T-ALL) arises from clonal expansion of a lymphoid progenitor that has undergone stepwise alteration at distinct stages of differentiation. It is suggested that a set of cooperative mutations that affect different pathways are required before thymocytes become fully malignant. Despite major improvements in our understanding of the molecular genetics of T-ALL, the underlying mechanisms that lead to the abnormal proliferation and enhanced survival of the leukemic cells remain largely unknown. Results: Array CGH analysis revealed an acquired homozygous microdeletion at chromosome 18p11 in 6 % of T-ALL cases. The deleted region was only 125 kb in size and restricted to the PTPN2 (protein tyrosine phosphatase, non-receptor type 2) locus. PTPN2 encodes an intracellular non-transmembrane tyrosine-specific phosphatase that functions as a negative regulator of a variety of signaling proteins including several members of the janus kinase (JAK) and of signal transducer and activator of transcription (STAT) families, growth factor receptors and SRC family kinases. Homozygous deletion of PTPN2 was specifically found in cases with aberrant expression of the TLX1 transcription factor, with two cases also harboring the NUP214-ABL1 fusion. Analysis of additional TLX1 positive cases by quantitative PCR identified loss of one copy of PTPN2 in 5 out of 20 cases. No mutations were detected in the coding region of PTPN2. To determine the effect of loss of PTPN2 in T-cells, we downregulated the expression of PTPN2 using RNAi technology. siRNA mediated knock-down of PTPN2 affected activation of JAK1 associated cytokine receptors implicated in T-cell development. Ligand stimulation of IL7 and interferon gamma receptor resulted in an augmented and prolonged phosphorylation of JAK1 as well as downstream targets STAT1 and STAT5 in T-ALL cell lines with knock-down of PTPN2. In addition, knock- down of Ptpn2 sensitized the pro B-cell line Ba/F3 to transformation by wild type JAK1 confirming a clear relationship between loss of PTPN2 and JAK1 activation. Knock-down of PTPN2 expression also provided a proliferative advantage and reduced sensitivity to kinase inhibitors in lymphoblastic leukemia cell lines HSB-2 and ALL-SIL. Conclusion: In conclusion, our data provide genetic and functional evidence for a tumor suppressor role of PTPN2 in T-ALL and warrant testing of JAK inhibitors for the treatment of this specific subset of T-ALLs as well as further analysis of a potential negative impact of loss of PTPN2 on responsiveness to anti-cancer treatments. Disclosures: Ferrando: Merck, Pfizer: Research Funding.

scholarly journals Identification of a Nuclear Stat1 Protein Tyrosine Phosphatase

2002 ◽  
Vol 22 (16) ◽  
pp. 5662-5668 ◽  
Author(s):  
Johanna ten Hoeve ◽  
Maria de Jesus Ibarra-Sanchez ◽  
Yubin Fu ◽  
Wei Zhu ◽  
Michel Tremblay ◽  
...  
Keyword(s):  
Protein Tyrosine Phosphatase ◽  
Tyrosine Phosphatase ◽  
Nuclear Extract ◽  
Null Mouse ◽  
Protein Tyrosine ◽  
Nuclear Extracts ◽  
Unknown Protein ◽  
Stat1 Protein

ABSTRACT Upon interferon (IFN) stimulation, Stat1 becomes tyrosine phosphorylated and translocates into the nucleus, where it binds to DNA to activate transcription. The activity of Stat1 is dependent on tyrosine phosphorylation, and its inactivation in the nucleus is accomplished by a previously unknown protein tyrosine phosphatase (PTP). We have now purified a Stat1 PTP activity from HeLa cell nuclear extract and identified it as TC45, the nuclear isoform of the T-cell PTP (TC-PTP). TC45 can dephosphorylate Stat1 both in vitro and in vivo. Nuclear extracts lacking TC45 fail to dephosphorylate Stat1. Furthermore, the dephosphorylation of IFN-induced tyrosine-phosphorylated Stat1 is defective in TC-PTP-null mouse embryonic fibroblasts (MEFs) and primary thymocytes. Reconstitution of TC-PTP-null MEFs with TC45, but not the endoplasmic reticulum (ER)-associated isoform TC48, rescues the defect in Stat1 dephosphorylation. The dephosphorylation of Stat3, but not Stat5 or Stat6, is also affected in TC-PTP-null cells. Our results identify TC45 as a PTP responsible for the dephosphorylation of Stat1 in the nucleus.

scholarly journals IGF-1R Modulation of Acute GH-Induced STAT5 Signaling: Role of Protein Tyrosine Phosphatase Activity

2013 ◽  
Vol 27 (11) ◽  
pp. 1969-1979 ◽  
Author(s):  
Yujun Gan ◽  
Yue Zhang ◽  
Ashiya Buckels ◽  
Andrew J. Paterson ◽  
Jing Jiang ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Phosphatase Activity ◽  
Protein Tyrosine Phosphatase ◽  
Tyrosine Phosphatase ◽  
Janus Kinase ◽  
Janus Kinase 2 ◽  
Protein Tyrosine ◽  
Primary Osteoblasts ◽  
Ptp 1B ◽  
In Cells

GH is a potent anabolic and metabolic factor that binds its cell surface receptor (GHR), activating the GHR-associated tyrosine kinase, Janus kinase 2, which phosphorylates and activates the latent transcription factor, signal transducer and activator of transcription 5 (STAT5). Some GH actions are mediated by the elaboration of IGF-1, which exerts effects by binding and activating the heterotetrameric tyrosine kinase growth factor receptor, IGF-1R. In addition to this GH-GHR-IGF-1-IGF-1R scheme, we have demonstrated in primary osteoblasts and in islet β-cells that then deletion or silencing of IGF-1R results in diminished GH-induced STAT5 phosphorylation, suggesting that the presence of IGF-1R may facilitate GH signaling. In this study, we explore potential roles for protein tyrosine phosphatase activity in modulating GH-induced signaling, comparing conditions in which IGF-1R is present or diminished. We confirm that in mouse primary osteoblasts harboring loxP sites flanking the IGF-1R gene, infection with an adenovirus that expresses the Cre recombinase results in IGF-1R deletion and diminished acute GH-induced STAT5 phosphorylation. Furthermore, we present a new model of IGF-1R silencing, in which expression of short hairpin RNA directed at IGF-1R greatly reduces IGF-1R abundance in LNCaP human prostate cancer cells. In both models, treatment with a chemical inhibitor of protein tyrosine phosphatase-1B (PTP-1B), but not one of src homology region 2 domain-containing phosphotase-1 (SHP-1) and SHP-2, reverses the loss of GH-induced STAT5 phosphorylation in cells lacking IGF-1R but has no effect in cells with intact IGF-1R. Furthermore, expression of either a dominant-negative PTP-1B or the PTP-1B-interacting inhibitory protein, constitutive photomorphogenesis 1, also rescues acute GH-induced STAT5 signaling in IGF-1R-deficient cells but has no effect in IGF-1R replete cells. By expressing a substrate-trapping mutant PTP-1B, we demonstrate that tyrosine phosphorylated Janus kinase-2 is a PTP-1B substrate only in cells lacking IGF-1R. Collectively, our data suggest that IGF-1R positively regulates acute GH signaling by preventing access of PTP-1B activity to Janus kinase 2 and thereby preventing PTP-1B-mediated suppression of GH-induced STAT5 activation.

scholarly journals Microtubule and Cell Contact Dependency of ER-bound PTP1B Localization in Growth Cones

2009 ◽  
Vol 20 (6) ◽  
pp. 1878-1889 ◽  
Author(s):  
Federico Fuentes ◽  
Carlos O. Arregui
Keyword(s):  
Growth Cone ◽  
Protein Tyrosine Phosphatase ◽  
Tyrosine Phosphatase ◽  
Growth Cones ◽  
Peripheral Region ◽  
Cell Contact ◽  
Positive Role ◽  
Cellular Targets ◽  
Axon Elongation

PTP1B is an ER-bound protein tyrosine phosphatase implied in the regulation of cell adhesion. Here we investigated mechanisms involved in the positioning and dynamics of PTP1B in axonal growth cones and evaluated the role of this enzyme in axons. In growth cones, PTP1B consistently localizes in the central domain, and occasionally at the peripheral region and filopodia. Live imaging of GFP-PTP1B reveals dynamic excursions of fingerlike processes within the peripheral region and filopodia. PTP1B and GFP-PTP1B colocalize with ER markers and coalign with microtubules at the peripheral region and redistribute to the base of the growth cone after treatment with nocodazole, a condition that is reversible. Growth cone contact with cellular targets is accompanied by invasion of PTP1B and stable microtubules in the peripheral region aligned with the contact axis. Functional impairment of PTP1B causes retardation of axon elongation, as well as reduction of growth cone filopodia lifetime and Src activity. Our results highlight the role of microtubules and cell contacts in the positioning of ER-bound PTP1B to the peripheral region of growth cones, which may be required for the positive role of PTP1B in axon elongation, filopodia stabilization, and Src activity.

scholarly journals The PTP1B mutant PTP1B2-4 is a positive regulator of the JAK/STAT signalling pathway in Hodgkin lymphoma

2020 ◽  
Author(s):  
Malena Zahn ◽  
Bianca Kaluszniak ◽  
Peter Möller ◽  
Ralf Marienfeld
Keyword(s):  
Hodgkin Lymphoma ◽  
Protein Tyrosine Phosphatase ◽  
Molecular Mechanisms ◽  
Tyrosine Phosphatase ◽  
Janus Kinase ◽  
Protein Tyrosine Phosphatase 1B ◽  
Oncogenic Potential ◽  
Protein Levels ◽  
Mrna Variants ◽  
Chronic Activation

Abstract The neoplastic Hodgkin/Reed-Sternberg (HRS) cells of classical Hodgkin lymphoma (cHL) depend on chronic activation of the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signalling pathways to maintain survival and proliferation. Accumulating reports highlight the importance of the inactivation or reduced expression of negative JAK/STAT regulators such as the protein-tyrosine phosphatase 1B (PTP1B/PTPN1) in this process. Various PTPN1 mRNA variants as well as truncated PTP1B proteins were identified in cHL cell lines and primary cHL tumour samples. These PTPN1 mRNA variants lack either one or several exon sequences and therefore render these PTP1B variants catalytically inactive. Here we show that one of these mutants, PTP1B▵2-4, is not only a catalytically inactive variant, but also augmented the IL-4-induced JAK/STAT activity similar to the recently reported PTP1B▵6 splice variant. Moreover, while PTP1B▵6 diminished the activity and protein levels of PTP1BWT, PTP1BWT remained unaffected by PTP1B▵2-4, arguing for different molecular mechanisms of JAK/STAT modulation by PTP1B▵6 and PTP1B▵2-4. Collectively, these data indicate that PTPN1 variants missing one or more exon sequences originated either from alternative splicing or from gene mutation, create PTP1B gain-of-function variants with oncogenic potential by augmenting JAK/STAT signalling in cHL.

scholarly journals Salicylate-enhanced activation of transcription factors induced by interferon-γ

1999 ◽  
Vol 342 (3) ◽  
pp. 503 ◽  
Author(s):  
Li-Chun CHEN ◽  
Diane KEPKA-LENHART ◽  
Timothy M. WRIGHT ◽  
Sidney M. MORRIS, JR
Keyword(s):  
Transcription Factors ◽  
Interferon Γ ◽  
Activation Of Transcription
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