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Pandey R, Bakay M, Hakonarson H. SOCS-JAK-STAT inhibitors and SOCS mimetics as treatment options for autoimmune uveitis, psoriasis, lupus, and autoimmune encephalitis. Front Immunol 2023; 14:1271102. [PMID: 38022642 PMCID: PMC10643230 DOI: 10.3389/fimmu.2023.1271102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Accepted: 10/02/2023] [Indexed: 12/01/2023] Open
Abstract
Autoimmune diseases arise from atypical immune responses that attack self-tissue epitopes, and their development is intricately connected to the disruption of the JAK-STAT signaling pathway, where SOCS proteins play crucial roles. Conditions such as autoimmune uveitis, psoriasis, lupus, and autoimmune encephalitis exhibit immune system dysfunctions associated with JAK-STAT signaling dysregulation. Emerging therapeutic strategies utilize JAK-STAT inhibitors and SOCS mimetics to modulate immune responses and alleviate autoimmune manifestations. Although more research and clinical studies are required to assess their effectiveness, safety profiles, and potential for personalized therapeutic approaches in autoimmune conditions, JAK-STAT inhibitors and SOCS mimetics show promise as potential treatment options. This review explores the action, effectiveness, safety profiles, and future prospects of JAK inhibitors and SOCS mimetics as therapeutic agents for psoriasis, autoimmune uveitis, systemic lupus erythematosus, and autoimmune encephalitis. The findings underscore the importance of investigating these targeted therapies to advance treatment options for individuals suffering from autoimmune diseases.
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Affiliation(s)
- Rahul Pandey
- Center for Applied Genomics, Children's Hospital of Philadelphia, Philadelphia, PA, United States
| | - Marina Bakay
- Center for Applied Genomics, Children's Hospital of Philadelphia, Philadelphia, PA, United States
| | - Hakon Hakonarson
- Center for Applied Genomics, Children's Hospital of Philadelphia, Philadelphia, PA, United States
- Department of Pediatrics, The University of Pennsylvania School of Medicine, Philadelphia, PA, United States
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Chen X, Li P, Huang R, Zhang J, Ouyang X, Tan D. Ulinastatin affects focal cerebral ischemia-reperfusion injury via SOCS1-mediated JAK2/STAT3 signalling pathway. Clin Exp Pharmacol Physiol 2023; 50:107-116. [PMID: 36222378 DOI: 10.1111/1440-1681.13731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 09/28/2022] [Accepted: 10/07/2022] [Indexed: 12/14/2022]
Abstract
Cerebral ischemia results in loss of cerebral blood flow, which contributes to neuronal damage, neurocognitive impairment, as well as learning and memory difficulties. Although reperfusion is necessary to restore the blood supply to the brain, it also leads to several detrimental effects on the brain. The purpose of this study was to assess the effects of ulinastatin (UTI) on preventing focal cerebral ischemia/reperfusion-induced injury (FCIRI). First, a rat model of FCIRI was established and treated with UTI. The effects of UTI on FCIRI in rats were evaluated using Morris water maze assay, triphenyl tetrazolium chloride staining, TUNEL, western blot assay, and enzyme-linked immunosorbent assay analysis. UTI was found to improve the learning memory ability, reduce infarction area, inhibit apoptosis and decrease inflammation in FCIRI rats. Messenger RNA microarray analysis of hippocampal tissues revealed that suppressor of cytokine signalling-1 (SOCS1) was the downstream target of UTI in FCIRI. SOCS1 depletion impaired the protective effect of UTI on FCIRI in rats. SOCS1 blocked the activation of the JAK2/STAT3 pathway. JAK2 inhibitor caused the JAK2/STAT3 pathway deficit, hence reversing the effect of sh-SOCS1 on FCIRI in rats. Taken together, our results demonstrate that UTI alleviated FCIRI in rats, which was, to some extent, related to SOCS1-mediated JAK2/STAT3 pathway.
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Affiliation(s)
- Xiaoxi Chen
- Department of Anesthesiology, Hengyang City Central Hospital, Hengyang, China
| | - Peng Li
- Department of Anesthesiology, Hengyang City Central Hospital, Hengyang, China
| | - Renming Huang
- Department of Anesthesiology, Hengyang City Central Hospital, Hengyang, China
| | - Juan Zhang
- Department of Anesthesiology, Hengyang City Central Hospital, Hengyang, China
| | - Xingzhi Ouyang
- Department of Anesthesiology, Hengyang City Central Hospital, Hengyang, China
| | - Dianxiang Tan
- Department of Anesthesiology, Hengyang City Central Hospital, Hengyang, China
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Sharma J, Larkin J. Therapeutic Implication of SOCS1 Modulation in the Treatment of Autoimmunity and Cancer. Front Pharmacol 2019; 10:324. [PMID: 31105556 PMCID: PMC6499178 DOI: 10.3389/fphar.2019.00324] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 03/18/2019] [Indexed: 12/14/2022] Open
Abstract
The suppressor of cytokine signaling (SOCS) family of intracellular proteins has a vital role in the regulation of the immune system and resolution of inflammatory cascades. SOCS1, also called STAT-induced STAT inhibitor (SSI) or JAK-binding protein (JAB), is a member of the SOCS family with actions ranging from immune modulation to cell cycle regulation. Knockout of SOCS1 leads to perinatal lethality in mice and increased vulnerability to cancer, while several SNPs associated with the SOCS1 gene have been implicated in human inflammation-mediated diseases. In this review, we describe the mechanism of action of SOCS1 and its potential therapeutic role in the prevention and treatment of autoimmunity and cancer. We also provide a brief outline of the other JAK inhibitors, both FDA-approved and under investigation.
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Affiliation(s)
- Jatin Sharma
- Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL, United States
| | - Joseph Larkin
- Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL, United States
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Duncan SA, Baganizi DR, Sahu R, Singh SR, Dennis VA. SOCS Proteins as Regulators of Inflammatory Responses Induced by Bacterial Infections: A Review. Front Microbiol 2017; 8:2431. [PMID: 29312162 PMCID: PMC5733031 DOI: 10.3389/fmicb.2017.02431] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2017] [Accepted: 11/23/2017] [Indexed: 12/31/2022] Open
Abstract
Severe bacterial infections can lead to both acute and chronic inflammatory conditions. Innate immunity is the first defense mechanism employed against invading bacterial pathogens through the recognition of conserved molecular patterns on bacteria by pattern recognition receptors (PRRs), especially the toll-like receptors (TLRs). TLRs recognize distinct pathogen-associated molecular patterns (PAMPs) that play a critical role in innate immune responses by inducing the expression of several inflammatory genes. Thus, activation of immune cells is regulated by cytokines that use the Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway and microbial recognition by TLRs. This system is tightly controlled by various endogenous molecules to allow for an appropriately regulated and safe host immune response to infections. Suppressor of cytokine signaling (SOCS) family of proteins is one of the central regulators of microbial pathogen-induced signaling of cytokines, principally through the inhibition of the activation of JAK/STAT signaling cascades. This review provides recent knowledge regarding the role of SOCS proteins during bacterial infections, with an emphasis on the mechanisms involved in their induction and regulation of antibacterial immune responses. Furthermore, the implication of SOCS proteins in diverse processes of bacteria to escape host defenses and in the outcome of bacterial infections are discussed, as well as the possibilities offered by these proteins for future targeted antimicrobial therapies.
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Affiliation(s)
- Skyla A Duncan
- Center for NanoBiotechnology Research, Alabama State University, Montgomery, AL, United States
| | - Dieudonné R Baganizi
- Center for NanoBiotechnology Research, Alabama State University, Montgomery, AL, United States
| | - Rajnish Sahu
- Center for NanoBiotechnology Research, Alabama State University, Montgomery, AL, United States
| | - Shree R Singh
- Center for NanoBiotechnology Research, Alabama State University, Montgomery, AL, United States
| | - Vida A Dennis
- Center for NanoBiotechnology Research, Alabama State University, Montgomery, AL, United States
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Cheng C, Huang C, Ma TT, Xu T, Wang YR, Zhang L, Jun L. New surprises of suppressor of cytokine signalling in liver fibrosis. Expert Opin Ther Targets 2014; 18:415-26. [DOI: 10.1517/14728222.2014.885953] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Chhabra JK, Chattopadhyay B, Paul BN. SOCS3 dictates the transition of divergent time-phased events in granulocyte TNF-α signaling. Cell Mol Immunol 2013; 11:105-6. [PMID: 24037182 DOI: 10.1038/cmi.2013.36] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Revised: 07/02/2013] [Accepted: 07/04/2013] [Indexed: 11/09/2022] Open
Abstract
Tumor-necrosis factor-α (TNF-α)-driven nuclear factor-κB (NF-κB) activation and apoptosis are opposing pathways; the growing recognition of these conflicting roles of TNF-α is perplexing. Here, we show that inflammation and apoptosis are time-phased events following TNF-α signaling and that emergence of suppressor of cytokine signaling 3 (SOCS3) expression limits the ongoing NF-κB activation and promotes apoptosis; further, we suggest an altered view of how inflammatory diseases are initiated and sustained. In vitro, TNF-α (50 ng/ml) induced granulocyte SOCS3 protein, inhibited nuclear accumulation of the p65NF-κB subunit and enhanced apoptosis, as shown by DNA laddering, annexin V positivity, and overexpression of caspase-3 and Bax in the late phase, whereas the early phase was marked by NF-κB activation. Conversely, SOCS3 knockdown by small interfering RNA (siRNA) inhibited granulocyte apoptosis and enhanced nuclear accumulation of p65 and 5' lipooxygenase expression in the late phase of TNF-α signaling. As apoptosis is associated with SOCS3 abundance, we suggest that these divergent TNF-α-driven events are time-phased, interconnected, opposing control mechanisms and one of the central features through which the immune system resolves pulmonary inflammation. Dysregulation may initiate mucosal inflammation, thus changing the landscape of asthma therapy.
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Affiliation(s)
- Jasmeet Kaur Chhabra
- Immunobiology Division, CSIR-Indian Institute of Toxicology Research, Lucknow, India
| | | | - Bhola Nath Paul
- Immunobiology Division, CSIR-Indian Institute of Toxicology Research, Lucknow, India
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Lan F, Zhang N, Zhang J, Krysko O, Zhang Q, Xian J, Derycke L, Qi Y, Li K, Liu S, Lin P, Bachert C. Forkhead box protein 3 in human nasal polyp regulatory T cells is regulated by the protein suppressor of cytokine signaling 3. J Allergy Clin Immunol 2013; 132:1314-21. [PMID: 23910692 DOI: 10.1016/j.jaci.2013.06.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 06/07/2013] [Accepted: 06/07/2013] [Indexed: 02/05/2023]
Abstract
BACKGROUND In patients with persistent upper airway inflammation, the number of forkhead box protein 3 (Foxp3)(+) regulatory T (Treg) cells is reduced, but the regulation of Foxp3 expression in Treg cells is poorly understood. OBJECTIVE We investigated the interaction between suppressor of cytokine signaling 3 (SOCS3) and Foxp3 expression in the airway mucosa. METHODS Expression of SOCS3 and Foxp3 was measured in tissue from patients with chronic rhinosinusitis with nasal polyps (CRSwNP) and control tissue. Coexpression of SOCS3 and Foxp3 was evaluated in PBMCs and in tissue from patients with CRSwNP. We also switched off and overexpressed SOCS3 in tissue from patients with CRSwNP and in pancreatic carcinoma epithelial-like cell line (PANC-1) cells and examined the effect on Foxp3 expression. RESULTS SOCS3 gene and protein expression was upregulated in inflammatory cells in airway mucosa, whereas Foxp3 gene and protein expression was downregulated. Mucosal Treg cells coexpressed both proteins. Switching off the expression of SOCS3 in human airway mucosa resulted in Foxp3 upregulation, whereas inducing it in PANC-1 cells led to Foxp3 downregulation. We also found that phosphorylation of signal transducer and activator of transcription (STAT) 3 was decreased in inflamed mucosa, and we hypothesized that SOCS3 was responsible. Phosphorylation of STAT3 increased on silencing SOCS3 expression in inflamed mucosa and decreased on SOCS3 plasmid transfection in PANC-1 cells. CONCLUSION For the first time, we demonstrate that SOCS3 and Foxp3 are coexpressed in Treg cells in human nasal mucosa and that SOCS3 negatively regulates Foxp3 expression in human airway mucosa, possibly through phosphorylation of STAT3. Hence SOCS3 could be a potential target for restoring Foxp3 expression in Treg cells in patients with persistent mucosal inflammation.
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Affiliation(s)
- Feng Lan
- Division of Geriatrics, Center for Medical Stem Cell Biology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China; Upper Airways Research Laboratory, ENT Department, Ghent University, Ghent, Belgium
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White CA, Nicola NA. SOCS3: An essential physiological inhibitor of signaling by interleukin-6 and G-CSF family cytokines. JAKSTAT 2013; 2:e25045. [PMID: 24416642 PMCID: PMC3876435 DOI: 10.4161/jkst.25045] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Accepted: 05/15/2013] [Indexed: 12/21/2022] Open
Abstract
SOCS3 is an inducible negative feedback inhibitor of cytokine signaling. Conditional deletion of SOCS3 in mice using the Cre-lox system has now been applied to a range of cell types in the steady-state and under inflammatory, pathogenic, or tumorigenic stress, with the resulting phenotypes demonstrating the effects of SOCS3 in physiological and disease contexts. Together with recent structural and biochemical studies on the mechanisms of SOCS3 binding to cytokine receptors and associated kinases, we now have a better understanding of the non-redundant roles of SOCS3 in the inhibition of cytokine signaling via the receptors gp130, G-CSFR, leptinR, and IL-12Rβ. This review discusses the known functional activities of SOCS3 in fertility and development, inflammation, innate and adaptive immunity, and malignancy as determined by genetic studies in mice.
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Affiliation(s)
- Christine A White
- Walter and Eliza Hall Institute of Medical Research; Parkville, VIC Australia ; Department of Medical Biology; University of Melbourne; Parkville, VIC Australia
| | - Nicos A Nicola
- Walter and Eliza Hall Institute of Medical Research; Parkville, VIC Australia ; Department of Medical Biology; University of Melbourne; Parkville, VIC Australia
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Touw IP, Palande K, Beekman R. Granulocyte colony-stimulating factor receptor signaling: implications for G-CSF responses and leukemic progression in severe congenital neutropenia. Hematol Oncol Clin North Am 2012; 27:61-73, viii. [PMID: 23351988 DOI: 10.1016/j.hoc.2012.10.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Following activation by their cognate ligands, cytokine receptors undergo intracellular routing toward lysosomes, where they are degraded. This review focuses on the signaling function of the G-CSFR in relation to the dynamics of endosomal routing of the G-CSFR. Mechanisms involving receptor lysine ubiquitination and redox-controlled phosphatase activities are discussed. Specific attention is paid to the consequences of G-CSFR mutations, acquired in patients with severe congenital neutropenias who receive G-CSF therapy, particularly in the context of leukemic transformation, a major clinical complication of the disease.
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Affiliation(s)
- Ivo P Touw
- Department of Hematology, Erasmus University Medical Center, Dr Molewaterplein 50 3015 GE, Rotterdam, The Netherlands.
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SOCS1 cooperates with FLT3-ITD in the development of myeloproliferative disease by promoting the escape from external cytokine control. Blood 2012; 120:1691-702. [DOI: 10.1182/blood-2010-08-301416] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Abstract
Activating mutations in the receptor tyrosine kinase FLT3 are frequently found in acute myelogenous leukemia patients and confer poor clinical prognosis. It is unclear how leukemic blasts escape cytokine control that regulates normal hematopoiesis. We have recently demonstrated that FLT3-internal tandem duplication (ITD), when localized to the biosynthetic compartment, aberrantly activates STAT5. Here, we show that one of the target genes induced by STAT5 is suppressor of cytokine signaling (SOCS)1—a surprising finding for a known tumor suppressor. Although SOCS1 expression in murine bone marrow severely impaired cytokine-induced colony growth, it failed to inhibit FLT3-ITD–supported colony growth, indicating resistance of FLT3-ITD to SOCS1. In addition, SOCS1 coexpression did not affect FLT3-ITD–mediated signaling or proliferation. Importantly, SOCS1 coexpression inhibited interferon-α and interferon-γ signaling and protected FLT3-ITD hematopoietic cells from interferon-mediated growth inhibitory effects. In a murine bone marrow transplantation model, the coexpression of SOCS1 and FLT3-ITD significantly shortened the latency of a myeloproliferative disease compared with FLT3-ITD alone (P < .01). Mechanistically, SOCS proteins shield FLT3-ITD from external cytokine control, thereby promoting leukemogenesis. The data demonstrate that SOCS1 acts as a conditional oncogene, providing novel molecular insights into cytokine resistance in oncogenic transformation. Restoring cytokine control may provide a new way of therapeutic intervention.
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Abstract
Because of their genetically determined capacity to respond to pro-inflammatory stimuli, keratinocytes have a crucial role in the pathogenesis of psoriasis. Upon IFN-γ and TNF-α exposure, psoriatic keratinocytes express exaggerated levels of inflammatory mediators, and show aberrant hyperproliferation and terminal differentiation. The thickening of psoriasic skin also results from a peculiar resistance of keratinocytes to cytokine-induced apoptosis. In this study, we investigated on the molecular mechanisms concurring to the resistance of psoriatic keratinocytes to cell death, focusing on the role having suppressor of cytokine signaling (SOCS)1 and SOCS3, two molecules abundantly expressed in IFN-γ/TNF-α-activated psoriatic keratinocytes, in sustaining anti-apoptotic pathways. We found that SOCS1 and SOCS3 suppress cytokine-induced apoptosis by sustaining the activation of the PI3K/AKT pathway in keratinocytes. The latter determines the activation of the anti-apoptotic NF-κB cascade and, in parallel, the inhibition of the pro-apoptotic BAD function in keratinocytes. For the first time, we report that phosphorylated AKT and phosphorylated BAD are strongly expressed in lesional psoriatic skin, compared with healthy or not lesional skin, and they strictly correlate to the high expression of SOCS1 and SOCS3 molecules in the psoriatic epidermis. Finally, the depletion of SOCS1 and SOCS3, as well as the chemical inactivation of PI3K activity in psoriatic keratinocytes, definitively unveils the role of PI3K/AKT cascade on the resistance of diseased keratinocytes to apoptosis.
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Liu Q, Dong F. Gfi-1 inhibits the expression of eosinophil major basic protein (MBP) during G-CSF-induced neutrophilic differentiation. Int J Hematol 2012; 95:640-7. [PMID: 22552881 DOI: 10.1007/s12185-012-1078-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Revised: 03/30/2012] [Accepted: 04/05/2012] [Indexed: 10/28/2022]
Abstract
The zinc finger transcriptional repressor Gfi-1 has been shown to play a critical role in early granulopoiesis; however, its role in late neutrophilic development is poorly understood. We report here that forced expression of a dominant negative Gfi-1 mutant, N382S, resulted in augmented mRNA levels of eosinophil major basic protein (MBP) in myeloid cells induced with G-CSF to undergo terminal neutrophilic differentiation. MBP is a cytotoxic protein that is abundantly expressed in eosinophils, but not in neutrophils. Ectopic expression of MBP inhibited the proliferation and survival of differentiating myeloid cells in response to G-CSF. Significantly, while GFI-1 is upregulated during neutrophilic differentiation, it is rapidly downregulated upon induction of eosinophilic differentiation, which was associated with increased MBP expression. Knockdown of GFI-1 in eosinophilic cells also led to increased level of MBP mRNA. These results indicate that Gfi-1 functions to inhibit the expression of MBP and aberrant expression of MBP as a result of loss of Gfi-1 function may cause premature apoptosis of differentiating neutrophils. In contrast, the rapid downregulation of Gfi-1 during eosinophilic development may allow for abundant expression of MBP, a hallmark of eosinophilic differentiation.
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Affiliation(s)
- Qingquan Liu
- Department of Biological Sciences, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606, USA
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Abstract
The hematopoietic growth factor GM-CSF has long been known for its colony-formation properties in the generation of neutrophils, macrophages and DCs. However, a study by Miah et al. in this issue of the European Journal of Immunology [Eur. J. Immunol. 2012. 42: 58-68] reports that GM-CSF also terminates its own proliferation-inducing STAT5-signaling via induction of the SOCS family member cytokine-inducible SH2-domain protein (CISH, also known as CIS). CISH levels were continuously increased during murine GM-CSF-dependent DC development in vitro and CISH, in turn, suppressed STAT5 phosphorylation to inhibit further GM-CSF signals. In addition, CISH activity promoted MHC class I- but not MHC class II-dependent antigen presentation after DC maturation, selectively supporting the priming of CTLs but not Th1 responses. This is the first demonstration of a molecular switch turning proliferating DC precursors into the differentiated immature DC stage and beyond, thereby paving the way for DC maturation. Since CISH polymorphisms critically affect human susceptibility to infectious diseases, further studies with this interesting molecule and its mutants will allow further insights into the induction of immune responses by DCs in humans.
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Affiliation(s)
- Manfred B Lutz
- Institute of Virology and Immunobiology, University of Würzburg, Würzburg, Germany.
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The deubiquitinating enzyme DUB2A enhances CSF3 signalling by attenuating lysosomal routing of the CSF3 receptor. Biochem J 2011; 434:343-51. [PMID: 21155715 DOI: 10.1042/bj20101628] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Ubiquitination of the CSF3R [CSF3 (colony-stimulating factor 3) receptor] occurs after activated CSF3Rs are internalized and reside in early endosomes. CSF3R ubiquitination is crucial for lysosomal routing and degradation. The E3 ligase SOCS3 (suppressor of cytokine signalling 3) has been shown to play a major role in this process. Deubiquitinating enzymes remove ubiquitin moieties from target proteins by proteolytic cleavage. Two of these enzymes, AMSH [associated molecule with the SH3 domain of STAM (signal transducing adaptor molecule)] and UBPY (ubiquitin isopeptidase Y), interact with the general endosomal sorting machinery. Whether deubiquitinating enzymes control CSF3R trafficking from early towards late endosomes is unknown. In the present study, we asked whether AMSH, UBPY or a murine family of deubiquitinating enzymes could fulfil such a role. This DUB family (deubiquitin enzyme family) comprises four members (DUB1, DUB1A, DUB2 and DUB2A), which were originally described as being haematopoietic-specific and cytokine-inducible, but their function in cytokine receptor routing and signalling has remained largely unknown. We show that DUB2A expression is induced by CSF3 in myeloid 32D cells and that DUB2 decreases ubiquitination and lysosomal degradation of the CSF3R, leading to prolonged signalling. These results support a model in which CSF3R ubiquitination is dynamically controlled at the early endosome by feedback mechanisms involving CSF3-induced E3 ligase (SOCS3) and deubiquitinase (DUB2A) activities.
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Siggins RW, Melvan JN, Welsh DA, Bagby GJ, Nelson S, Zhang P. Alcohol suppresses the granulopoietic response to pulmonary Streptococcus pneumoniae infection with enhancement of STAT3 signaling. THE JOURNAL OF IMMUNOLOGY 2011; 186:4306-13. [PMID: 21357267 DOI: 10.4049/jimmunol.1002885] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Enhanced granulopoietic activity is crucial for host defense against bacterial pneumonia. Alcohol impairs this response. The underlying mechanisms remain obscure. G-CSF produced by infected lung tissue plays a key role in stimulating bone marrow granulopoiesis. This study investigated the effects of alcohol on G-CSF signaling in the regulation of marrow myeloid progenitor cell proliferation in mice with Streptococcus pneumoniae pneumonia. Chronic alcohol consumption plus acute alcohol intoxication suppressed the increase in blood granulocyte counts following intrapulmonary challenge with S. pneumoniae. This suppression was associated with a significant decrease in bone marrow granulopoietic progenitor cell proliferation. Alcohol treatment significantly enhanced STAT3 phosphorylation in bone marrow cells of animals challenged with S. pneumoniae. In vitro experiments showed that G-CSF-induced activation of STAT3-p27(Kip1) pathway in murine myeloid progenitor cell line 32D-G-CSFR cells was markedly enhanced by alcohol exposure. Alcohol dose dependently inhibited G-CSF-stimulated 32D-G-CSFR cell proliferation. This impairment of myeloid progenitor cell proliferation was not attenuated by inhibition of alcohol metabolism through either the alcohol dehydrogenase pathway or the cytochrome P450 system. These data suggest that alcohol enhances G-CSF-associated STAT3-p27(Kip1) signaling, which impairs granulopoietic progenitor cell proliferation by inducing cell cycling arrest and facilitating their terminal differentiation during the granulopoietic response to pulmonary infection.
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Affiliation(s)
- Robert W Siggins
- Department of Physiology, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
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Piccaluga PP, Malagola M, Rondoni M, Ottaviani E, Testoni N, Laterza C, Visani G, Pileri SA, Martinelli G, Baccarani M. Poor outcome of adult acute lymphoblastic leukemia patients carrying the (1;19)(q23;p13) translocation. Leuk Lymphoma 2009; 47:469-72. [PMID: 16396770 DOI: 10.1080/10428190500331261] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The (1;19)(q23;p13) translocation, leading to the production of the E2A/PBX1 fusion transcript, is one of the most common translocations in pediatric B-lineage acute lymphoblastic leukemia (ALL). It was assumed to be associated with a poor clinical outcome, although intensive therapy and bone marrow transplantation have been shown to be able to overcome the negative prognostic impact. Only few data are available concerning t(1;19)(q23;p13) in adult ALL. In particular, the prognostic significance of this genetic aberration is not yet clear. We describe three cases of adult ALL carrying the t(1;19)(q23;p13), who were all characterized by an aggressive clinical course and short survival, and discuss the molecular features of the disease as recently identified by gene expression profiling.
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Affiliation(s)
- Pier Paolo Piccaluga
- Institute of Haematology and Medical Oncology 'L. and A. Serànoli', S. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy.
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Babon JJ, Sabo JK, Zhang JG, Nicola NA, Norton RS. The SOCS box encodes a hierarchy of affinities for Cullin5: implications for ubiquitin ligase formation and cytokine signalling suppression. J Mol Biol 2009; 387:162-74. [PMID: 19385048 DOI: 10.1016/j.jmb.2009.01.024] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The SOCS (suppressors of cytokine signalling) family of proteins inhibits the cytokine-induced signalling cascade in part by promoting the ubiquitination of signalling intermediates that are then targeted for proteasomal degradation. This activity relies upon an interaction between the SOCS box domain, the adapter complex elonginBC and a member of the Cullin family, the scaffold protein of an E3 ubiquitin ligase. In this study, we dissected this interaction in vitro using purified components.We found that all eight SOCS proteins bound Cullin5 but required prior recruitment of elonginBC. Neither SOCS nor elonginBC bound Cullin5 when in isolation. Interestingly, the affinity of each SOCS-elonginBC complex for Cullin5 varied by 2 orders of magnitude across the SOCS family. Unexpectedly, the most potent suppressors of signalling, SOCS-1 and SOCS-3, bound most weakly to the E3 ligase scaffold, with affinities 100- and 10-fold lower, respectively, than the rest of the family. The remaining six SOCS proteins all bound Cullin5 with high affinity (K(d) of ~10 nM) due to a slower off-rate and hence a longer halflife of the complex. This difference in affinity may reflect a difference in mode of action as only SOCS-1 and SOCS-3 have been shown to suppress signalling using both SOCS box-dependent and SOCS box-independent mechanisms. This is not the case with the other six SOCS proteins, and our data imply the existence of two distinct subclasses of SOCS proteins with a high affinity for Cullin5, the E3 ligase scaffold, possibly reflecting complete dependence upon ubiquitination for suppression of cytokine signalling.
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Affiliation(s)
- Jeffrey J Babon
- Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria, Australia.
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Zebrafish granulocyte colony-stimulating factor receptor signaling promotes myelopoiesis and myeloid cell migration. Blood 2009; 113:2535-46. [PMID: 19139076 DOI: 10.1182/blood-2008-07-171967] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Granulocyte colony-stimulating factor receptor (GCSFR) signaling participates in the production of neutrophilic granulocytes during normal hematopoietic development, with a particularly important role during emergency hematopoiesis. This study describes the characterization of the zebrafish gcsf and gcsfr genes, which showed broad conservation and similar regulation to their mammalian counterparts. Morpholino-mediated knockdown of gcsfr and overexpression of gcsf revealed the presence of an anterior population of myeloid cells during primitive hematopoiesis that was dependent on GCSF/GCSFR for development and migration. This contrasted with a posterior domain that was largely independent of this pathway. Definitive myelopoiesis was also partially dependent on a functional GCSF/GCSFR pathway. Injection of bacterial lipopolysaccharide elicited significant induction of gcsf expression and emergency production of myeloid cells, which was abrogated by gcsfr knockdown. Collectively, these data demonstrate GCSF/GCSFR to be a conserved signaling system for facilitating the production of multiple myeloid cell lineages in both homeostatic and emergency conditions, as well as for early myeloid cell migration, establishing a useful experimental platform for further dissection of this pathway.
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19
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Babon JJ, Sabo JK, Soetopo A, Yao S, Bailey MF, Zhang JG, Nicola NA, Norton RS. The SOCS box domain of SOCS3: structure and interaction with the elonginBC-cullin5 ubiquitin ligase. J Mol Biol 2008; 381:928-40. [PMID: 18590740 DOI: 10.1016/j.jmb.2008.06.038] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2008] [Revised: 06/11/2008] [Accepted: 06/12/2008] [Indexed: 11/27/2022]
Abstract
Suppressor of cytokine signalling 3 (SOCS3) is responsible for regulating the cellular response to a variety of cytokines, including interleukin 6 and leukaemia inhibitory factor. Identification of the SOCS box domain led to the hypothesis that SOCS3 can associate with functional E3 ubiquitin ligases and thereby induce the degradation of bound signalling proteins. This model relies upon an interaction between the SOCS box, elonginBC and a cullin protein that forms the E3 ligase scaffold. We have investigated this interaction in vitro using purified components and show that SOCS3 binds to elonginBC and cullin5 with high affinity. The SOCS3-elonginBC interaction was further characterised by determining the solution structure of the SOCS box-elonginBC ternary complex and by deletion and alanine scanning mutagenesis of the SOCS box. These studies revealed that conformational flexibility is a key feature of the SOCS-elonginBC interaction. In particular, the SOCS box is disordered in isolation and only becomes structured upon elonginBC association. The interaction depends upon the first 12 residues of the SOCS box domain and particularly on a deeply buried, conserved leucine. The SOCS box, when bound to elonginBC, binds tightly to cullin5 with 100 nM affinity. Domains upstream of the SOCS box are not required for elonginBC or cullin5 association, indicating that the SOCS box acts as an independent binding domain capable of recruiting elonginBC and cullin5 to promote E3 ligase formation.
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Affiliation(s)
- Jeffrey J Babon
- Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3050, Australia.
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20
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Xiao BG, Lu CZ, Link H. Cell biology and clinical promise of G-CSF: immunomodulation and neuroprotection. J Cell Mol Med 2008; 11:1272-90. [PMID: 18205701 PMCID: PMC4401293 DOI: 10.1111/j.1582-4934.2007.00101.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
In the light of the enthusiasm to use of recombinant human granulocyte colony-stimulating factor (G-CSF) for immunomodulation and neuroprotection, it should be remembered that the current knowledge is based on a century of laborious research. G-CSF is a pleiotropic cytokine playing a major role as regulator of haematopoiesis. Although the precise mechanisms of G-CSF are not known, there is growing evidence supporting the notion that G-CSF also exerts profound immunoregulatory effect in adaptive immunity and has a neuroprotective role in both cerebral ischemia and neurodegeneration. Here, we describe the immunomodulation and the neuroprotection that can be achieved with G-CSF, and summarize possible mechanisms of G-CSF as a potential therapeutic agent in autoimmune diseases and neurological disorders. Our understanding of these novel sites of action of G-CSF has opened therapeutic avenues for the treatment of autoimmune diseases and neurological disorders, and has translated the beneficial effects of G-CSF from basic experiments to clinical patients.
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Affiliation(s)
- Bao-Guo Xiao
- Institute of Neurology, Huashan Hospital, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, China.
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21
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Irandoust MI, Aarts LHJ, Roovers O, Gits J, Erkeland SJ, Touw IP. Suppressor of cytokine signaling 3 controls lysosomal routing of G-CSF receptor. EMBO J 2007; 26:1782-93. [PMID: 17363902 PMCID: PMC1847666 DOI: 10.1038/sj.emboj.7601640] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2006] [Accepted: 01/31/2007] [Indexed: 01/03/2023] Open
Abstract
The hematopoietic system provides an attractive model for studying growth factor-controlled expansion and differentiation of cells in relation to receptor routing and its consequences for signal transduction. Suppressor of cytokine signaling (SOCS) proteins regulate receptor signaling partly via their ubiquitin ligase (E3)-recruiting SOCS box domain. Whether SOCS proteins affect signaling through modulating intracellular trafficking of receptors is unknown. Here, we show that a juxtamembrane lysine residue (K632) of the granulocyte colony-stimulating factor receptor (G-CSFR) plays a key role in receptor routing and demonstrate that the effects of SOCS3 on G-CSF signaling to a major extent depend on this lysine. Mutation of K632 causes accumulation of G-CSFR in early endosomes and leads to sustained activation of signal transducer and activator of transcription 5 and ERK, but not protein kinase B. Myeloid progenitors expressing G-CSFR mutants lacking K632 show a perturbed proliferation/differentiation balance in response to G-CSF. This is the first demonstration of SOCS-mediated ubiquitination and routing of a cytokine receptor and its impact on maintaining an appropriate signaling output.
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Affiliation(s)
- Mahban I Irandoust
- Department of Hematology, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Lambertus H J Aarts
- Department of Hematology, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Onno Roovers
- Department of Hematology, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Judith Gits
- Department of Hematology, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Stefan J Erkeland
- Department of Hematology, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Ivo P Touw
- Department of Hematology, Erasmus University Medical Center, Rotterdam, The Netherlands
- Department of Hematology, Erasmus University Medical Center, PO Box 2040, 3000 CA Rotterdam, The Netherlands. Tel.: +31 1040 87837; Fax: +31 1040 89470; E-mail:
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22
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Lavens D, Ulrichts P, Catteeuw D, Gevaert K, Vandekerckhove J, Peelman F, Eyckerman S, Tavernier J. The C-terminus of CIS defines its interaction pattern. Biochem J 2007; 401:257-67. [PMID: 16961462 PMCID: PMC1698688 DOI: 10.1042/bj20060242] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Proteins of the SOCS (suppressors of cytokine signalling) family are characterized by a conserved modular structure with pre-SH2 (Src homology 2), SH2 and SOCS-box domains. Several members, including CIS (cytokine-inducible SH2 protein), SOCS1 and SOCS3, are induced rapidly upon cytokine receptor activation and function in a negative-feedback loop, attenuating signalling at the receptor level. We used a recently developed mammalian two-hybrid system [MAPPIT (mammalian protein-protein interaction trap)] to analyse SOCS protein-interaction patterns in intact cells, allowing direct comparison with biological function. We find that, besides the SH2 domain, the C-terminal part of the CIS SOCS-box is required for functional interaction with the cytokine receptor motifs examined, but not with the N-terminal death domain of the TLR (Toll-like receptor) adaptor MyD88. Mutagenesis revealed that one single tyrosine residue at position 253 is a critical binding determinant. In contrast, substrate binding by the highly related SOCS2 protein, and also by SOCS1 and SOCS3, does not require their SOCS-box.
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Affiliation(s)
- Delphine Lavens
- Flanders Interuniversity Institute for Biotechnology, Department of Medical Protein Research (VIB09), Faculty of Medicine and Health Sciences, Ghent University, Baertsoenkaai 3, 9000 Ghent, Belgium
| | - Peter Ulrichts
- Flanders Interuniversity Institute for Biotechnology, Department of Medical Protein Research (VIB09), Faculty of Medicine and Health Sciences, Ghent University, Baertsoenkaai 3, 9000 Ghent, Belgium
| | - Dominiek Catteeuw
- Flanders Interuniversity Institute for Biotechnology, Department of Medical Protein Research (VIB09), Faculty of Medicine and Health Sciences, Ghent University, Baertsoenkaai 3, 9000 Ghent, Belgium
| | - Kris Gevaert
- Flanders Interuniversity Institute for Biotechnology, Department of Medical Protein Research (VIB09), Faculty of Medicine and Health Sciences, Ghent University, Baertsoenkaai 3, 9000 Ghent, Belgium
| | - Joël Vandekerckhove
- Flanders Interuniversity Institute for Biotechnology, Department of Medical Protein Research (VIB09), Faculty of Medicine and Health Sciences, Ghent University, Baertsoenkaai 3, 9000 Ghent, Belgium
| | - Frank Peelman
- Flanders Interuniversity Institute for Biotechnology, Department of Medical Protein Research (VIB09), Faculty of Medicine and Health Sciences, Ghent University, Baertsoenkaai 3, 9000 Ghent, Belgium
| | - Sven Eyckerman
- Flanders Interuniversity Institute for Biotechnology, Department of Medical Protein Research (VIB09), Faculty of Medicine and Health Sciences, Ghent University, Baertsoenkaai 3, 9000 Ghent, Belgium
| | - Jan Tavernier
- Flanders Interuniversity Institute for Biotechnology, Department of Medical Protein Research (VIB09), Faculty of Medicine and Health Sciences, Ghent University, Baertsoenkaai 3, 9000 Ghent, Belgium
- To whom correspondence should be addressed (email )
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23
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Horwitz MS, Duan Z, Korkmaz B, Lee HH, Mealiffe ME, Salipante SJ. Neutrophil elastase in cyclic and severe congenital neutropenia. Blood 2006; 109:1817-24. [PMID: 17053055 PMCID: PMC1801070 DOI: 10.1182/blood-2006-08-019166] [Citation(s) in RCA: 197] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Mutations in ELA2 encoding the neutrophil granule protease, neutrophil elastase (NE), are the major cause of the 2 main forms of hereditary neutropenia, cyclic neutropenia and severe congenital neutropenia (SCN). Genetic evaluation of other forms of neutropenia in humans and model organisms has helped to illuminate the role of NE. A canine form of cyclic neutropenia corresponds to human Hermansky-Pudlak syndrome type 2 (HPS2) and results from mutations in AP3B1 encoding a subunit of a complex involved in the subcellular trafficking of vesicular cargo proteins (among which NE appears to be one). Rare cases of SCN are attributable to mutations in the transcriptional repressor Gfi1 (among whose regulatory targets also include ELA2). The ultimate biochemical consequences of the mutations are not yet known, however. Gene targeting of ELA2 has thus far failed to recapitulate neutropenia in mice. The cycling phenomenon and origins of leukemic transformation in SCN remain puzzling. Nevertheless, mutations in all 3 genes are capable of causing the mislocalization of NE and may also induce the unfolded protein response, suggesting that there might a convergent pathogenic mechanism focusing on NE.
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Affiliation(s)
- Marshall S Horwitz
- Division of Medical Genetics, Department of Medicine, University of Washington School of Medicine, Seattle, WA 98195, USA.
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24
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Shao H, Xu X, Jing N, Tweardy DJ. Unique structural determinants for Stat3 recruitment and activation by the granulocyte colony-stimulating factor receptor at phosphotyrosine ligands 704 and 744. THE JOURNAL OF IMMUNOLOGY 2006; 176:2933-41. [PMID: 16493051 DOI: 10.4049/jimmunol.176.5.2933] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
G-CSFR cytoplasmic tyrosine (Y) residues (Y704, Y729, Y744, and Y764) become phosphorylated upon ligand binding and recruit specific Src homology 2 domain-containing proteins that link to distinct yet overlapping programs for myeloid cell survival, differentiation, proliferation, and activation. The structural basis for recruitment specificity is poorly understood but could be exploited to selectively target deleterious G-CSFR-mediated signaling events such as aberrant Stat3 activation demonstrated in a subset of acute myeloid leukemia patients with poor prognosis. Recombinant Stat3 bound to G-CSFR phosphotyrosine peptide ligands pY704VLQ and pY744LRC with similar kinetics. Testing of three models for Stat3 Src homology 2-pY ligand binding in vitro and in vivo revealed unique determinants for Stat3 recruitment and activation by the G-CSFR, the side chain of Stat3 R609, which interacts with the pY ligand phosphate group, and the peptide amide hydrogen of E638, which bonds with oxygen/sulfur within the + 3 Q/C side chain of the pY ligand when it assumes a beta turn. Thus, our findings identify for the first time the structural basis for recruitment and activation of Stat3 by the G-CSFR and reveal unique features of this interaction that can be exploited to target Stat3 activation for the treatment of a subset of acute myeloid leukemia patients.
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Affiliation(s)
- Huang Shao
- Section of Infectious Diseases, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
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25
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SOCS2 can enhance interleukin-2 (IL-2) and IL-3 signaling by accelerating SOCS3 degradation. Mol Cell Biol 2005. [PMID: 16199887 DOI: 10.1128/mcb.25.20.9115‐9126.2005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Cytokine responses can be regulated by a family of proteins termed suppressors of cytokine signaling (SOCS) which can inhibit the JAK/STAT pathway in a classical negative-feedback manner. While the SOCS are thought to target signaling intermediates for degradation, relatively little is known about how their turnover is regulated. Unlike other SOCS family members, we find that SOCS2 can enhance interleukin-2 (IL-2)- and IL-3-induced STAT phosphorylation following and potentiate proliferation in response to cytokine stimulation. As a clear mechanism for these effects, we demonstrate that expression of SOCS2 results in marked proteasome-dependent reduction of SOCS3 and SOCS1 protein expression. Furthermore, we provide evidence that this degradation is dependent on the presence of an intact SOCS box and that the loss of SOCS3 is enhanced by coexpression of elongin B/C. This suggests that SOCS2 can bind to SOCS3 and elongin B/C to form an E3 ligase complex resulting in the degradation of SOCS3. Therefore, SOCS2 can enhance cytokine responses by accelerating proteasome-dependent turnover of SOCS3, suggesting a mechanism for the gigantism observed in SOCS2 transgenic mice.
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26
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Tannahill GM, Elliott J, Barry AC, Hibbert L, Cacalano NA, Johnston JA. SOCS2 can enhance interleukin-2 (IL-2) and IL-3 signaling by accelerating SOCS3 degradation. Mol Cell Biol 2005; 25:9115-26. [PMID: 16199887 PMCID: PMC1265772 DOI: 10.1128/mcb.25.20.9115-9126.2005] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2005] [Revised: 04/13/2005] [Accepted: 07/18/2005] [Indexed: 01/27/2023] Open
Abstract
Cytokine responses can be regulated by a family of proteins termed suppressors of cytokine signaling (SOCS) which can inhibit the JAK/STAT pathway in a classical negative-feedback manner. While the SOCS are thought to target signaling intermediates for degradation, relatively little is known about how their turnover is regulated. Unlike other SOCS family members, we find that SOCS2 can enhance interleukin-2 (IL-2)- and IL-3-induced STAT phosphorylation following and potentiate proliferation in response to cytokine stimulation. As a clear mechanism for these effects, we demonstrate that expression of SOCS2 results in marked proteasome-dependent reduction of SOCS3 and SOCS1 protein expression. Furthermore, we provide evidence that this degradation is dependent on the presence of an intact SOCS box and that the loss of SOCS3 is enhanced by coexpression of elongin B/C. This suggests that SOCS2 can bind to SOCS3 and elongin B/C to form an E3 ligase complex resulting in the degradation of SOCS3. Therefore, SOCS2 can enhance cytokine responses by accelerating proteasome-dependent turnover of SOCS3, suggesting a mechanism for the gigantism observed in SOCS2 transgenic mice.
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Affiliation(s)
- Gillian M Tannahill
- Infection and Immunity Group, Centre for Cancer Research and Cell Biology, Queens University, Belfast, UK
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27
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Zhuang D, Qiu Y, Haque SJ, Dong F. Tyrosine 729 of the G-CSF receptor controls the duration of receptor signaling: involvement of SOCS3 and SOCS1. J Leukoc Biol 2005; 78:1008-15. [PMID: 16033816 DOI: 10.1189/jlb.0105032] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Mutations in the granulocyte-colony stimulating factor receptor (G-CSF-R) gene resulting in carboxy terminal truncation have been associated with acute myeloid leukemia (AML). The truncated G-CSF-R from AML patients mediate enhanced and prolonged activation of signal transducer and activator of transcription 5 (Stat5). It has been shown that Src homology-2 (SH2)-containing tyrosine phosphatase-1 attenuates the intensity of G-CSF-induced Stat5 activation through interacting with the carboxy terminus of the G-CSF-R. Using a series of tyrosine-to-phenylalanine substitution mutants, we show here that tyrosine (Tyr) 729, located in the carboxy terminus of the G-CSF-R, controls the duration of G-CSF-stimulated activation of Stat5, Akt, and extracellular signal-regulated kinase 1/2. It is interesting that activation of these signaling molecules by G-CSF was prolonged by pretreating cells with actinomycin D or cyclohexamide, suggesting that de novo protein synthesis is required for appropriate termination of G-CSF-R signaling. The transcripts for suppressor of cytokine signaling 3 (SOCS3) and SOCS1 were up-regulated rapidly upon G-CSF stimulation. Expression of SOCS3 or SOCS1, but not SOCS2 and cytokine-inducible SH2 domain-containing protein, completely suppressed G-CSF-induced Stat5 activation but had only a weak effect on Stat5 activation mediated by the receptor mutant lacking Tyr 729. SOCS1 and SOCS3 also inhibited G-CSF-dependent cell proliferation, but the inhibitory effect of the two SOCS proteins on cell proliferation was diminished when Tyr 729 of the G-CSF-R was mutated. These data indicate that Tyr 729 of the G-CSF-R is required for SOCS1- and SOCS3-mediated negative regulation of G-CSF-R signaling and that the duration and intensity of G-CSF-induced Stat5 activation are regulated by two distinct mechanisms.
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Affiliation(s)
- Dazhong Zhuang
- Department of Biological Sciences, University of Toledo, Toledo, OH 43606, USA
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