ABSTRACT
Uncontrolled interferon γ (IFNγ)-mediated T-cell responses to commensal microbiota are a driver of inflammatory bowel disease (IBD). Interleukin-10 (IL-10) is crucial for controlling these T-cell responses, but the precise mechanism of inhibition remains unclear. A better understanding of how IL-10 exerts its suppressive function may allow identification of individuals with suboptimal IL-10 function among the heterogeneous population of IBD patients. Using cells from patients with an IL10RA deficiency or STAT3 mutations, we demonstrate that IL-10 signaling in monocyte-derived dendritic cells (moDCs), but not T cells, is essential for controlling IFNγ-secreting CD4+ T cells. Deficiency in IL-10 signaling dramatically increased IL-1ß release by moDCs. IL-1ß boosted IFNγ secretion by CD4+ T cells either directly or indirectly by stimulating moDCs to secrete IL-12. As predicted a signature of IL-10 dysfunction was observed in a subgroup of pediatric IBD patients having higher IL-1ß expression in activated immune cells and macroscopically affected intestinal tissue. In agreement, reduced IL10RA expression was detected in peripheral blood mononuclear cells and a subgroup of pediatric IBD patients exhibited diminished IL-10 responsiveness. Our data unveil an important mechanism by which IL-10 controls IFNγ-secreting CD4+ T cells in humans and identifies IL-1ß as a potential classifier for a subgroup of IBD patients.
Subject(s)
CD4-Positive T-Lymphocytes/immunology , CD4-Positive T-Lymphocytes/metabolism , Dendritic Cells/immunology , Dendritic Cells/metabolism , Interferon-gamma/metabolism , Interleukin-10/metabolism , Interleukin-1beta/metabolism , Signal Transduction , Adolescent , Cell Communication , Child , Disease Susceptibility , Humans , Inflammatory Bowel Diseases/etiology , Inflammatory Bowel Diseases/metabolism , Inflammatory Bowel Diseases/pathology , Inflammatory Bowel Diseases/therapyABSTRACT
The 4T1 mammary carcinoma cell line produces TSLP. We had hypothesized that TSLP promotes the development of a permissive environment for the growth and metastasis of primary tumour and that this is associated with a Th2-polarized antitumour immune response. We found that, in Tslpr(-/-) mice, the mean tumour diameters were smaller from days 27 to 40, and relatively fewer tumour cells were present in the lung, compared with wild-type mice. Polarization of the Th2 cytokine profile was also diminished in Tslpr(-/-) mice. These findings confirmed those reported previously by others. Here, we further show that primary tumours are established less often in Tslpr(-/-) mice and that, unexpectedly, the relative number of tumour cells in the brain is greater in Tslpr(-/-) mice compared with wild-type mice. Findings from our cytotoxicity assays show that 4T1-directed lysis is undetectable in both WT and Tslpr(-/-) mice, ruling out the possibility that altered cytotoxic responses in Tslpr(-/-) mice are responsible for the differences we observed. In a human tissue microarray, positive staining for TSLP was seen in tumour cells from breast cancer tissue, but it was also seen in normal glandular epithelial cells from normal breast tissue, which has not been shown before. Thus, our findings provide new insight into the effects of TSLP in metastatic breast cancer.
Subject(s)
Brain Neoplasms/metabolism , Breast Neoplasms/metabolism , Immunoglobulins/genetics , Lung Neoplasms/metabolism , Receptors, Cytokine/genetics , Th2 Cells/immunology , Animals , Cell Line, Tumor , Cell Proliferation , Cytokines/metabolism , Female , Humans , Immunoglobulins/deficiency , Mice , Mice, Inbred BALB C , Mice, Knockout , Receptors, Cytokine/deficiency , Th2 Cells/metabolism , Tissue Array AnalysisABSTRACT
Previously, we have shown that IL-21R(-/-) splenocytes ameliorate GVHD as compared with wild-type splenocytes. Here, we investigated whether or not IL-21R(-/-) splenocytes diminish the graft-versus-leukemia (GVL) effect. Surprisingly, IL-21R(-/-) splenocytes efficiently eliminate leukemic cells as well as wild-type splenocytes, suggesting the retention of GVL effects in the absence of IL-21 signaling. To compare the GVL effect between IL-21R(-/-) and wild-type cells, we titrated the number of splenocytes required for the elimination of leukemic cells and found that the threshold of GVL effect was obtained between 5 × 10(5) and 5 × 10(6) with both types of splenocytes. Cotransplantation with CD8-depleted splenocytes but not with purified CD8 T-cells resulted in a significant reduction in anti-leukemic effect of IL-21R(-/-) cells compared with wild-type cells, suggesting that the lack of IL-21 signaling primarily impairs CD4 T-cell rather than CD8 T-cell function and the comparable GVL effect with IL-21R(-/-) bulk splenocytes results from cooperative compensation by CD8 T-cells.
Subject(s)
CD4-Positive T-Lymphocytes/immunology , CD8-Positive T-Lymphocytes/immunology , Graft vs Leukemia Effect/immunology , Interleukins/immunology , Leukemia/immunology , Signal Transduction/immunology , Animals , Graft vs Leukemia Effect/genetics , Humans , Interleukin-21 Receptor alpha Subunit/genetics , Interleukin-21 Receptor alpha Subunit/immunology , Interleukins/genetics , Interleukins/metabolism , Leukemia/genetics , Leukemia/therapy , Mice , Mice, Knockout , Signal Transduction/geneticsABSTRACT
Immunological effects of IL-21 on T, B and natural killer (NK) cells have been reported, but the role of IL-21 in GVHD remains obscure. Here, we demonstrate that morbidity and mortality of GVHD was significantly reduced after BMT with splenocytes from IL-21R(-/-) mice compared with those from wild type mice. To further confirm our observation, we generated a decoy receptor for IL-21. GVHD was again less severe in mice receiving BM cells transduced with the IL-21 decoy receptor than control mice These results suggest that IL-21 critically regulates GVHD, and that blockade of the IL-21 signal may represent a novel strategy for the prophylaxis for GVHD.
Subject(s)
Bone Marrow Transplantation/adverse effects , Disease Models, Animal , Graft vs Host Disease/immunology , Interleukins/immunology , Animals , CD4-CD8 Ratio , Kaplan-Meier Estimate , Mice , Mice, Inbred BALB C , Mice, KnockoutABSTRACT
The interleukin-2 receptor alpha (IL-2Ralpha) chain is an essential component of high-affinity IL-2 receptors. Accordingly, IL-2Ralpha expression helps to regulate T cell growth and other lymphoid functions. Lineage-restricted and activation-dependent IL-2Ralpha transcription is controlled by three upstream positive regulatory regions (PRRs). We now describe an additional IL-2 response element, PRRIV, within intron 1, in humans and mice. PRRIV activity requires GAS motifs that bind Stat5 proteins and additional upstream HMG-I(Y) binding sites. Moreover, IL-2 induces the binding of HMG-I(Y), Stat5a, and Stat5b in vivo to PRRIV and PRRIII, which also functions as an IL-2 response element. Thus, the IL-2 inducibility of the IL-2Ralpha gene is unexpectedly mediated by two widely separated regulatory Stat5-dependent elements, located both upstream and downstream of the transcription initiation sites.
Subject(s)
Gene Expression Regulation/drug effects , Interleukin-2/pharmacology , Milk Proteins , Receptors, Interleukin-2/genetics , Response Elements , Amino Acid Motifs , Animals , Base Sequence , DNA-Binding Proteins/metabolism , Deoxyribonuclease I/pharmacology , HMGA1a Protein , High Mobility Group Proteins/metabolism , Humans , Mice , Mice, Knockout , Molecular Sequence Data , Promoter Regions, Genetic , STAT5 Transcription Factor , Trans-Activators/metabolism , Transcription Factors/metabolism , Tumor Suppressor ProteinsABSTRACT
The p12(I) protein, encoded by the pX open reading frame I of the human T-lymphotropic virus type 1 (HTLV-1), is a hydrophobic protein that localizes to the endoplasmic reticulum and the Golgi. Although p12(I) contains 4 minimal proline-rich, src homology 3-binding motifs (PXXP), a characteristic commonly found in proteins involved in signaling pathways, it has not been known whether p12(I) has a role in modulating intracellular signaling pathways. This study demonstrated that p12(I) binds to the cytoplasmic domain of the interleukin-2 receptor (IL-2R) beta chain that is involved in the recruitment of the Jak1 and Jak3 kinases. As a result of this interaction, p12(I) increases signal transducers and activators of transcription 5 (STAT5) DNA binding and transcriptional activity and this effect depends on the presence of both IL-2R beta and gamma(c) chains and Jak3. Transduction of primary human peripheral blood mononuclear cells (PBMCs) with a human immunodeficiency virus type 1-based retroviral vector expressing p12(I) also resulted in increased STAT5 phosphorylation and DNA binding. However, p12(I) could increase proliferation of human PBMCs only after stimulation of T-cell receptors by treatment of cells with low concentrations of alphaCD3 and alphaCD28 antibodies. In addition, the proliferative advantage of p12(I)-transduced PBMCs was evident mainly at low concentrations of IL-2. Together, these data indicate that p12(I) may confer a proliferative advantage on HTLV-1-infected cells in the presence of suboptimal antigen stimulation and that this event may account for the clonal proliferation of infected T cells in vivo. (Blood. 2001;98:823-829)
Subject(s)
DNA-Binding Proteins/drug effects , Interleukin-2/pharmacology , Milk Proteins , Oncogene Proteins, Viral/pharmacology , T-Lymphocytes/virology , Trans-Activators/drug effects , Transcription Factors , Cell Culture Techniques , Cell Division/drug effects , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Drug Synergism , HTLV-I Infections/metabolism , HTLV-I Infections/pathology , Humans , Protein Binding , Receptors, Interleukin-2/metabolism , STAT5 Transcription Factor , Signal Transduction/drug effects , T-Lymphocytes/cytology , T-Lymphocytes/drug effects , Trans-Activators/genetics , Trans-Activators/metabolism , Transcriptional Activation/drug effects , Viral Regulatory and Accessory ProteinsABSTRACT
The Janus family tyrosine kinase-signal transducer and activator of transcription (Jak-STAT) signaling pathway is broadly used by interferons and type I cytokines. These cytokines and interferons activate Janus family tyrosine kinases (Jak kinases), which in turn phosphorylate and thereby activate STAT proteins. Before activation, STAT proteins are cytosolic proteins; after activation, however, they are translocated to the nucleus where they function as transcription factors. This review summarizes salient features of the Jak-STAT pathway and focuses on the functional role of the different Jak kinases and STATs in vivo.
Subject(s)
Cytokines/physiology , Milk Proteins , Protein-Tyrosine Kinases/physiology , Proto-Oncogene Proteins , Signal Transduction/physiology , Transcription Factors/physiology , Active Transport, Cell Nucleus , Animals , Cell Transformation, Neoplastic , Cytosol/metabolism , DNA-Binding Proteins/physiology , Dimerization , Enzyme Activation , Gene Expression Regulation/physiology , Humans , Interferons/physiology , Janus Kinase 1 , Janus Kinase 2 , Janus Kinase 3 , Phosphorylation , Protein Conformation , Protein Processing, Post-Translational , Receptors, Cytokine/physiology , STAT1 Transcription Factor , STAT2 Transcription Factor , STAT3 Transcription Factor , STAT4 Transcription Factor , STAT5 Transcription Factor , STAT6 Transcription Factor , Trans-Activators/physiologyABSTRACT
JAB/suppressor of cytokine signaling 1 (SOCS1) STAT-induced STAT inhibitor-1 (SSI-1) (JAB/SOCS1/SSI-1) is an SH2-domain-containing protein that is induced by and negatively regulates signaling by a number of cytokines including interleukin-4 (IL-4), IL-6, interferon (IFN)-gamma, prolactin, growth hormone, and erythropoietin. The role of JAB/SOCS1/SSI-1 in IL-2 signaling has been analyzed. JAB/SOCS1/SSI-1 is strongly induced by IL-2 in peripheral blood T cells, and JAB/SOCS1/SSI-1 overexpression strongly inhibits IL-2-induced signal transducer and activator of transcription-5 (Stat5) phosphorylation and transcriptional activity. In cotransfection experiments, JAB/SOCS1/SSI-1 associates with both Jak1 and Jak3; however, JAB/SOCS1/SSI-1 had a greater effect on Jak1 tyrosine phosphorylation and kinase activity. JAB/SOCS1/SSI-1 also interacts with IL-2Rbeta, and this interaction requires the A region (residues 313-382) of IL-2Rbeta. However, this interaction was not essential for the inhibitory action of JAB. Thus, JAB/SOCS1/SSI-1 is an IL-2-induced inhibitor of IL-2 signaling that functions by inhibiting Jak kinase activity. This suggests an important role for JAB/SOCS1/SSI-1 in regulating T-cell responses.
Subject(s)
Carrier Proteins/pharmacology , Interleukin-2/physiology , Intracellular Signaling Peptides and Proteins , Milk Proteins , Signal Transduction/drug effects , Blotting, Western , Carrier Proteins/genetics , Carrier Proteins/physiology , Cell Line , DNA-Binding Proteins/antagonists & inhibitors , Enzyme Activation/drug effects , Gene Expression/drug effects , Humans , Janus Kinase 1 , Phosphorylation/drug effects , Precipitin Tests , Protein-Tyrosine Kinases/drug effects , RNA, Messenger/drug effects , RNA, Messenger/metabolism , Receptors, Interleukin-2/metabolism , Repressor Proteins/genetics , Repressor Proteins/pharmacology , Repressor Proteins/physiology , STAT5 Transcription Factor , Suppressor of Cytokine Signaling 1 Protein , Suppressor of Cytokine Signaling Proteins , T-Lymphocytes/drug effects , T-Lymphocytes/physiology , Trans-Activators/antagonists & inhibitors , Transcription, Genetic/drug effects , TransfectionABSTRACT
Severe combined immunodeficiency disease (SCID) refers to a spectrum of inherited immunodeficiencies that together represent the most severe forms of primary immunodeficiency in humans. Recent work has shown that many of these diseases, as well as other forms of immunodeficiency, result from defects in cytokine signalling pathways. Such defects can prevent normal development of lymphoid lineages and/or compromise cytokine signalling by these cells. These natural 'experiments' in human genetics have shown the non-redundant role for several cytokines or cytokine signalling molecules. Moreover, a comparison of the phenotypes of humans with SCID to analogous mouse-knockout models has shown not only expected similarities, but also unexpected differences in cytokine signalling between humans and mice.
Subject(s)
Cytokines/immunology , Severe Combined Immunodeficiency/immunology , Animals , Cytokines/chemistry , Cytokines/genetics , Genetic Linkage , Humans , Janus Kinase 3 , Killer Cells, Natural/immunology , Mice , Mice, Knockout , Mice, SCID , Models, Immunological , Mycobacterium Infections/genetics , Mycobacterium Infections/immunology , Protein-Tyrosine Kinases/genetics , Protein-Tyrosine Kinases/immunology , Receptors, Interleukin-2/immunology , Severe Combined Immunodeficiency/genetics , Signal Transduction , T-Lymphocytes/immunology , X Chromosome/geneticsABSTRACT
We have identified a type I cytokine receptor, which we have termed novel interleukin receptor (NILR), that is most related to the IL-2 receptor beta chain (IL-2Rbeta) and physically adjacent to the IL-4 receptor alpha chain gene on chromosome 16. NILR mRNA is most highly expressed in thymus and spleen, and is induced by phytohemagglutinin in human peripheral blood mononuclear cells. NILR protein was detected on human T cell lymphotropic virus type I-transformed T cell lines, Raji B cells, and YT natural killer-like cells. Artificial homodimerization of the NILR cytoplasmic domain confers proliferation to Ba/F3 murine pro-B cells but not to 32D myeloid progenitor cells or CTLL-2 murine helper T cells. In these latter cells, heterodimerization of IL-2Rbeta and the common cytokine receptor gamma chain (gamma(c)) cytoplasmic domains allows potent proliferation, whereas such heterodimerization of NILR with gamma(c) does not. This finding suggests that NILR has signaling potential but that a full understanding of its signaling partner(s) is not yet clear. Like IL-2Rbeta, NILR associates with Jak1 and mediates Stat5 activation.
Subject(s)
Receptors, Interleukin-2/genetics , Amino Acid Sequence , Animals , Base Sequence , Blotting, Western , Cell Line , Chromosomes, Artificial, Bacterial , Cloning, Molecular , DNA, Complementary , Humans , Interleukin-21 Receptor alpha Subunit , Mice , Molecular Sequence Data , Open Reading Frames , Precipitin Tests , Receptors, Interleukin-2/metabolism , Receptors, Interleukin-21 , Sequence Homology, Amino AcidSubject(s)
Biochemistry/methods , Recombinant Fusion Proteins/chemistry , Recombinant Fusion Proteins/metabolism , Signal Transduction , Animals , Cell Division , Cell Line , Cell Membrane/metabolism , Interleukin-4/metabolism , Mice , Models, Biological , Protein Structure, Tertiary , Receptor Protein-Tyrosine Kinases/chemistry , Receptor Protein-Tyrosine Kinases/metabolism , Receptors, Interleukin-2/chemistryABSTRACT
X-linked severe combined immunodeficiency (XSCID) is the most common form of SCID. The discovery of the genetic defect in this disease, namely mutations in the gene encoding the common cytokine receptor gamma chain, gammac, was reported just over seven years ago. In the subsequent period, a tremendous amount of knowledge about the biology and function of this protein has been generated. Moreover, gammac-knockout mice have been generated and their immune systems successfully reconstituted by gene therapy. Furthermore, initial attempts at using gene therapy to treat patients with XSCID have been successful for more than ten months, making this disease perhaps the most promising to date for treatment with such a strategy.
Subject(s)
Genetic Therapy , Receptors, Cytokine/genetics , Severe Combined Immunodeficiency/genetics , Severe Combined Immunodeficiency/therapy , X Chromosome , Animals , Humans , Killer Cells, Natural/immunology , Mice , Mice, Knockout , Mutation , Receptors, Cytokine/deficiency , Receptors, Cytokine/physiology , Severe Combined Immunodeficiency/immunology , T-Lymphocytes/immunologyABSTRACT
The receptor tyrosine kinase Flt3 plays an important role in proliferation and survival of hematopoietic stem and progenitor cells. Although some post-receptor signaling events of Flt3 have been characterized, the involvement of the Janus kinase/signal transducer and activator of transcription (Jak/Stat) pathway in Flt3 signaling has not been thoroughly evaluated. To this aim, we examined whether Flt3 activates the Jak/Stat pathway in Baf3/Flt3 cells, a line stably expressing human Flt3 receptor. Stat5a, but not Stats 1-4, 5b, or 6, was potently activated by Flt3 ligand (FL) stimulation. Interestingly, FL did not activate any Jaks. Activation of Stat5a required the kinase activity of Flt3. A selective role for Stat5a in the proliferative response of primary hematopoietic progenitor cells to FL was documented, as FL did not act on progenitors from marrows of Stat5a(-/-) mice, but did stimulate/costimulate proliferation of these cells from Stat5a(+/+), Stat5b(-/-), and Stat5b(+/+) mice. Thus, Stat5a is essential for at least certain effects of FL. Moreover, our data confirm that Stat5a and Stat5b are not redundant, but rather are at least partially distinctive in their function.
Subject(s)
DNA-Binding Proteins/physiology , Milk Proteins , Proto-Oncogene Proteins/physiology , Receptor Protein-Tyrosine Kinases/physiology , Signal Transduction , Trans-Activators/physiology , Animals , COS Cells , Cell Division , Cell Line , Colony-Stimulating Factors/pharmacology , Humans , Janus Kinase 1 , Janus Kinase 2 , Mice , Mice, Inbred C57BL , Mice, Knockout , Protein-Tyrosine Kinases/physiology , STAT5 Transcription Factor , Tumor Suppressor Proteins , fms-Like Tyrosine Kinase 3ABSTRACT
Recently, two SCID (severe combined immunodeficiency disease) patients with greatly diminished T cells but normal or increased numbers of B and NK cells (T(-)B(+)NK(+) SCID) were found to have mutations in the gene for the IL-7 receptor. This has established a major role for IL-7-receptor-dependent signaling in T cell development in humans and probably explains the diminished T cell numbers seen in patients with X-linked SCID or SCID that results from Jak3-deficiency.
Subject(s)
Receptors, Interleukin-7/immunology , Severe Combined Immunodeficiency/immunology , Animals , B-Lymphocytes/immunology , Genes, T-Cell Receptor gamma/immunology , Humans , Janus Kinase 3 , Killer Cells, Natural/immunology , Mutation , Protein-Tyrosine Kinases/deficiency , Protein-Tyrosine Kinases/immunology , Receptors, Interleukin-7/genetics , Severe Combined Immunodeficiency/genetics , Signal Transduction/immunology , T-Lymphocytes/immunologyABSTRACT
The activation of Stat5 proteins (Stat5a and Stat5b) is one of the earliest signaling events mediated by IL-2 family cytokines, allowing the rapid delivery of signals from the membrane to the nucleus. Among STAT family proteins, Stat5a and Stat5b are the two most closely related STAT proteins. Together with other transcription factors and co-factors, they regulate the expression of the target genes in a cytokine-specific fashion. In addition to their activation by cytokines, activities of Stat5a and Stat5b, as well as other STAT proteins, are negatively controlled by CIS/SOCS/SSI family proteins. The outcome of Stat5 activation in regulating expression of target genes varies, depending upon the complexity of the promoter region of target genes and the other signaling pathways that are activated by each cytokine as well. Here, we mainly focus on the IL2-/IL-2 receptor system, as it is one of the best-studied systems that depend on Stat5-mediated signals. We will summarize what we have learned about the molecular mechanisms of how Stat5 is activated by IL-2 family cytokines from in vitro biochemical studies as well as the role that is played by Stat5 in each of the cytokine signaling pathways from in vivo gene-targeting analyses. Oncogene (2000).
Subject(s)
DNA-Binding Proteins/metabolism , Interleukin-2/metabolism , Milk Proteins , Receptors, Interleukin-2/metabolism , Signal Transduction , Trans-Activators/metabolism , Amino Acid Sequence , Animals , Cell Transformation, Neoplastic , DNA-Binding Proteins/genetics , Gene Expression Regulation , Humans , Immune Tolerance , Immunologic Surveillance , Interleukin-2/immunology , Janus Kinase 3 , Protein-Tyrosine Kinases/metabolism , Receptors, Interleukin-2/chemistry , Receptors, Interleukin-2/genetics , Receptors, Interleukin-2/immunology , Response Elements/genetics , STAT5 Transcription Factor , Trans-Activators/genetics , Tumor Suppressor ProteinsABSTRACT
Transcriptional induction of the interleukin-2 receptor alpha-chain (IL-2Ralpha) gene is a key event regulating T-cell-mediated immunity in mammals. In vivo, the T-cell-restricted protein Elf-1 and the general architectural transcription factor HMG-I(Y) cooperate in transcriptional regulation of the human IL-2Ralpha gene by binding to a specific positive regulatory region (PRRII) in its proximal promoter. Employing chromatin reconstitution analyses, we demonstrate that the binding sites for both HMG-I(Y) and Elf-1 in the PRRII element are incorporated into a strongly positioned nucleosome in vitro. A variety of analytical techniques was used to determine that a stable core particle is positioned over most of the PRRII element and that this nucleosome exhibits only a limited amount of lateral translational mobility. Regardless of its translational setting, the in vitro position of the nucleosome is such that DNA recognition sequences for both HMG-I(Y) and Elf-1 are located on the surface of the core particle. Restriction nuclease accessibility analyses indicate that a similarly positioned nucleosome also exists on the PRRII element in unstimulated lymphocytes when the IL-2Ralpha gene is silent and suggest that this core particle is remodeled following transcriptional activation of the gene in vivo. In vitro experiments employing the chemical cleavage reagent 1,10-phenanthroline copper (II) covalently attached to its C-terminal end demonstrate that HMG-I(Y) protein binds to the positioned PRRII nucleosome in a direction-specific manner, thus imparting a distinct architectural configuration to the core particle. Together, these findings suggest a role for the HMG-I(Y) protein in assisting the remodeling of a critically positioned nucleosome on the PRRII promoter element during IL-2Ralpha transcriptional activation in lymphocytes in vivo.
Subject(s)
High Mobility Group Proteins/metabolism , Nucleosomes/metabolism , Receptors, Interleukin-2/genetics , Transcription Factors/metabolism , Base Sequence , Binding Sites , Chromatin/ultrastructure , DNA-Binding Proteins/metabolism , Enhancer Elements, Genetic , HMGA1a Protein , High Mobility Group Proteins/genetics , Humans , Molecular Sequence Data , Nucleosomes/genetics , Nucleosomes/ultrastructure , Promoter Regions, Genetic , Protein Biosynthesis , Regulatory Sequences, Nucleic Acid , Transcription Factors/genetics , Transcriptional ActivationABSTRACT
Cytokines represent a diverse group of molecules that transmit intercellular signals. These signals may either be autocrine (where the same cell both produces the cytokine and responds to it) or paracrine (where the cytokine is made by one cell and acts on another). Both these situations can occur simultaneously. Cytokines use multiple signaling pathways. This review will focus on signaling by type I cytokines and in particular on signaling by the IL-2 family of cytokines, as an illustrative example. The major signaling pathway that will be discussed is the Jak-STAT pathway, although other pathways will also be reviewed. The Jak-STAT pathway is a very rapid cytosol-to-nuclear signaling pathway that underscores how quickly extracellular signals can be transmitted to the nucleus. Aspects related to cytokine redundancy, pleiotropy, and specificity will be discussed.
Subject(s)
Receptors, Cytokine/physiology , Signal Transduction , Humans , Interleukin-2/physiology , Signal Transduction/physiology , Th1 Cells/chemistry , Th2 Cells/chemistryABSTRACT
A variety of important cellular functions are regulated by cytokines. The Jak-STAT pathway is one of the important signaling pathways downstream of cytokine receptors. Following binding of a ligand to its cognate receptor, receptor-associated Jaks are activated. STAT proteins are then in turn activated by tyrosine phosphorylation by Jak kinases, allowing their dimerization and subsequent translocation into the nucleus, where they modulate expression of target genes. Indispensable functions of Jaks and STATs in cytokine signaling in vivo have been revealed through knockout mouse studies. Moreover, the recent discovery of the CIS/SOCS/JAB/SSI family of inhibitors has contributed to understanding how this pathway is negatively regulated.
Subject(s)
DNA-Binding Proteins/physiology , Milk Proteins , Protein-Tyrosine Kinases/physiology , Proto-Oncogene Proteins , Trans-Activators/physiology , Animals , Cell Transformation, Neoplastic , Humans , Interleukin-2/pharmacology , Janus Kinase 1 , Janus Kinase 2 , Janus Kinase 3 , Killer Cells, Natural/physiology , Mice , STAT1 Transcription Factor , STAT3 Transcription Factor , STAT4 Transcription Factor , STAT5 Transcription Factor , STAT6 Transcription FactorABSTRACT
The common cytokine receptor gamma chain (gamma(c)) is an essential receptor component for IL-2, IL-4, IL-7, IL-9 and IL-15, and thereby gamma(c)-deficient mice exhibit impaired T cell and B cell development. The Janus family tyrosine kinase 3 (Jak3) is known to be associated with gamma(c), and the reported phenotypes of gamma(c)-deficient (gamma(c)(-)) and Jak3-deficient (Jak3(-)) mice are similar, indicating that Jak3 is an essential transducer of gamma(c)-dependent signals. Nevertheless, certain differences have been suggested related to the range of actions of gamma(c) and Jak3. To clarify whether gamma(c)-dependent cytokines can partially transduce their signals without Jak3, we compared lymphocyte development in gamma(c)(-), Jak3(-), and gamma(c) and Jak3 double-deficient (gamma(c)(-)Jak3(-)) mice in the same genetic background. With the exception that T and B cells in Jak3(-) mice express high levels of gamma(c), the defects in thymocyte and peripheral T cell and B cell development are indistinguishable among gamma(c)(-), Jak3(-) and gamma(c)(-)Jak3(-) mice. Interestingly, although Bcl-2 induction was previously suggested to be Jak3-independent, IL-7 cannot induce Bcl-2 expression in CD4 single-positive (SP) thymocytes in either gamma(c)(-) or Jak3(-) mice nor can IL-7 rescue CD4 SP thymocytes from dexamethasone-induced cell death in gamma(c)(-) or Jak3(-) mice. These results indicate that Jak3 is absolutely essential for gamma(c)-dependent T cell and B cell development, and for gamma(c)-dependent prevention of thymocyte apoptosis.
Subject(s)
Protein-Tyrosine Kinases/metabolism , Receptors, Antigen, T-Cell, gamma-delta/genetics , Receptors, Cytokine/metabolism , Signal Transduction , T-Lymphocytes/physiology , Animals , Apoptosis , B-Lymphocytes/physiology , CD4-Positive T-Lymphocytes/physiology , Cell Differentiation , Flow Cytometry , Gene Expression Regulation , Genes, bcl-2 , Intercellular Adhesion Molecule-1/metabolism , Janus Kinase 3 , Mice , Mice, Inbred BALB C , Mice, Knockout , Protein-Tyrosine Kinases/deficiency , Receptors, Cytokine/deficiency , Receptors, Interleukin-2/metabolism , TransgenesABSTRACT
During thymocyte development, T-cell receptor (TCR) alphabeta-mediated intracellular signals can elicit two entirely different cellular responses: positive selection (resulting in rescue from death and maturation or differentiation) and negative selection (induction of apoptosis). Here, Hiroshi Nakajima and colleagues discuss how survival signals that are dependent on the common cytokine receptor gamma chain (gammac) might affect the TCR-driven selection process in thymocytes, underscoring the potential role of cytokines in this process.