RESUMO
Mutations of the reelin gene cause severe defects in cerebral cortex development and profound intellectual impairment. While many aspects of the reelin signaling pathway have been identified, the molecular and ultimate cellular consequences of reelin signaling remain unknown. Specifically, it is unclear if termination of reelin signaling is as important for normal cortical neuron migration as activation of reelin signaling. Using mice that are single or double deficient, we discovered that combined loss of the suppressors of cytokine signaling, SOCS6 and SOCS7, recapitulated the cortical layer inversion seen in mice lacking reelin and led to a dramatic increase in the reelin signaling molecule disabled (DAB1) in the cortex. The SRC homology domains of SOCS6 and SOCS7 bound DAB1 ex vivo. Mutation of DAB1 greatly diminished binding and protected from degradation by SOCS6. Phosphorylated DAB1 was elevated in cortical neurons in the absence of SOCS6 and SOCS7. Thus, constitutive activation of reelin signaling was observed to be equally detrimental as lack of activation. We hypothesize that, by terminating reelin signaling, SOCS6 and SOCS7 may allow new cycles of reelin signaling to occur and that these may be essential for cortical neuron migration.
Assuntos
Moléculas de Adesão Celular Neuronais/metabolismo , Córtex Cerebral/embriologia , Córtex Cerebral/metabolismo , Proteínas da Matriz Extracelular/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Serina Endopeptidases/metabolismo , Proteínas Supressoras da Sinalização de Citocina/deficiência , Animais , Moléculas de Adesão Celular Neuronais/genética , Movimento Celular/fisiologia , Córtex Cerebral/patologia , Proteínas da Matriz Extracelular/genética , Células HEK293 , Humanos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteínas do Tecido Nervoso/genética , Neurônios/metabolismo , Fosforilação , Proteína Reelina , Serina Endopeptidases/genética , Proteínas Supressoras da Sinalização de Citocina/genéticaRESUMO
The Lyn tyrosine kinase governs the development and function of various immune cells, and its dysregulation has been linked to malignancy and autoimmunity. Using models of chemically induced colitis and enteric infection, we show that Lyn plays a critical role in regulating the intestinal microbiota and inflammatory responses as well as protection from enteric pathogens. Lyn(-/-) mice were highly susceptible to dextran sulfate sodium (DSS) colitis, characterized by significant wasting, rectal bleeding, colonic pathology, and enhanced barrier permeability. Increased DSS susceptibility in Lyn(-/-) mice required the presence of T but not B cells and correlated with dysbiosis and increased IFN-γ(+) and/or IL-17(+) colonic T cells. This dysbiosis was characterized by an expansion of segmented filamentous bacteria, associated with altered intestinal production of IL-22 and IgA, and was transmissible to wild-type mice, resulting in increased susceptibility to DSS. Lyn deficiency also resulted in an inability to control infection by the enteric pathogens Salmonella enterica serovar Typhimurium and Citrobacter rodentium. Lyn(-/-) mice exhibited profound cecal inflammation, bacterial dissemination, and morbidity following S. Typhimurium challenge and greater colonic inflammation throughout the course of C. rodentium infection. These results identify Lyn as a key regulator of the mucosal immune system, governing pathophysiology in multiple models of intestinal disease.
Assuntos
Colite/imunologia , Disbiose/imunologia , Infecções por Enterobacteriaceae/imunologia , Infecções por Salmonella/imunologia , Quinases da Família src/imunologia , Animais , Linfócitos B/imunologia , Linfócitos B/microbiologia , Citrobacter rodentium/imunologia , Citrobacter rodentium/patogenicidade , Colite/induzido quimicamente , Colite/microbiologia , Colite/patologia , Sulfato de Dextrana , Suscetibilidade a Doenças , Disbiose/genética , Disbiose/microbiologia , Disbiose/patologia , Infecções por Enterobacteriaceae/genética , Infecções por Enterobacteriaceae/microbiologia , Infecções por Enterobacteriaceae/patologia , Feminino , Expressão Gênica , Imunoglobulina A/genética , Imunoglobulina A/metabolismo , Interferon gama/genética , Interferon gama/imunologia , Interleucina-17/genética , Interleucina-17/imunologia , Interleucinas/genética , Interleucinas/imunologia , Mucosa Intestinal/imunologia , Mucosa Intestinal/microbiologia , Camundongos , Camundongos Knockout , Microbiota/imunologia , Infecções por Salmonella/genética , Infecções por Salmonella/microbiologia , Infecções por Salmonella/patologia , Salmonella typhimurium/imunologia , Salmonella typhimurium/patogenicidade , Índice de Gravidade de Doença , Linfócitos T/imunologia , Linfócitos T/microbiologia , Quinases da Família src/deficiência , Quinases da Família src/genética , Interleucina 22RESUMO
The innate immune response is a first line of defense against invading pathogens; however, the magnitude of this response must be tightly regulated, as hyper- or suboptimal responses can be detrimental to the host. Systemic inflammation resulting from bacterial infection can lead to sepsis, which remains a serious problem with high mortality rates. Lyn tyrosine kinase plays a key role in adaptive immunity, although its role in innate immunity remains unclear. In this study, we show that Lyn gain-of-function (Lyn(up/up)) mice display enhanced sensitivity to endotoxin and succumb to upregulated proinflammatory cytokine production at a dose well tolerated by control animals. Endotoxin sensitivity in Lyn(up/up) mice depends on dendritic cells (DCs) and NK cells and occurs though a mechanism involving increased maturation and activation of the DC compartment, leading to elevated production of IFN-γ by NK cells. We further show that modulation of endotoxin-induced signal transduction in DCs by Lyn involves the phosphatases Src homology 2 domain-containing phosphatase-1 and SHIP-1. Collectively, we demonstrate that Lyn regulates DC physiology such that alterations in Lyn-dependent signaling have profound effects on the nature and magnitude of inflammatory responses. Our studies highlight how perturbations in signaling pathways controlling DC/NK cell-regulated responses to microbial products can profoundly affect the magnitude of innate immune responses.
Assuntos
Células Dendríticas/imunologia , Imunidade Inata , Células Matadoras Naturais/imunologia , Ativação Linfocitária/imunologia , Transdução de Sinais/imunologia , Quinases da Família src/fisiologia , Animais , Células Cultivadas , Técnicas de Cocultura , Células Dendríticas/citologia , Células Dendríticas/metabolismo , Regulação da Expressão Gênica/imunologia , Imunidade Inata/genética , Interferon gama/biossíntese , Interferon gama/genética , Células Matadoras Naturais/citologia , Células Matadoras Naturais/metabolismo , Ativação Linfocitária/genética , Camundongos , Camundongos da Linhagem 129 , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Mutantes , Transdução de Sinais/genética , Quinases da Família src/deficiênciaRESUMO
While immunotherapies such as immune checkpoint blockade and adoptive T-cell therapy improve survival for a subset of human malignancies, many patients fail to respond. Phagocytes including dendritic cells (DC), monocytes, and macrophages (MF) orchestrate innate and adaptive immune responses against tumors. However, tumor-derived factors may limit immunotherapy effectiveness by altering phagocyte signal transduction, development, and activity. Using Cytometry by Time-of-Flight, we found that tumor-derived GCSF altered myeloid cell distribution both locally and systemically. We distinguished a large number of GCSF-induced immune cell subset and signal transduction pathway perturbations in tumor-bearing mice, including a prominent increase in immature neutrophil/myeloid-derived suppressor cell (Neut/MDSC) subsets and tumor-resident PD-L1+ Neut/MDSCs. GCSF expression was also linked to distinct tumor-associated MF populations, decreased conventional DCs, and splenomegaly characterized by increased splenic progenitors with diminished DC differentiation potential. GCSF-dependent dysregulation of DC development was recapitulated in bone marrow cultures in vitro, using medium derived from GCSF-expressing tumor cell cultures. Importantly, tumor-derived GCSF impaired T-cell adoptive cell therapy effectiveness and was associated with increased tumor volume and diminished survival of mice with mammary cancer. Treatment with neutralizing anti-GCSF antibodies reduced colonic and circulatory Neut/MDSCs, normalized colonic immune cell composition and diminished tumor burden in a spontaneous model of mouse colon cancer. Analysis of human colorectal cancer patient gene expression data revealed a significant correlation between survival and low GCSF and Neut/MDSC gene expression. Our data suggest that normalizing GCSF bioactivity may improve immunotherapy in cancers associated with GCSF overexpression. Significance: Tumor-derived GCSF leads to systemic immune population changes. GCSF blockade restores immune populations, improves immunotherapy, and reduces tumor size, paralleling human colorectal cancer data. GCSF inhibition may synergize with current immunotherapies to treat GCSF-secreting tumors.
Assuntos
Neoplasias do Colo , Células Supressoras Mieloides , Humanos , Camundongos , Animais , Células Mieloides , Transdução de Sinais , Linfócitos do Interstício Tumoral , Neoplasias do Colo/metabolismoRESUMO
Carbohydrate modification of proteins includes N-linked and O-linked glycosylation, proteoglycan formation, glycosylphosphatidylinositol anchor synthesis, and O-GlcNAc modification. Each of these modifications requires the sugar nucleotide UDP-GlcNAc, which is produced via the hexosamine biosynthesis pathway. A key step in this pathway is the interconversion of GlcNAc-6-phosphate (GlcNAc-6-P) and GlcNAc-1-P, catalyzed by phosphoglucomutase 3 (Pgm3). In this paper, we describe two hypomorphic alleles of mouse Pgm3 and show there are specific physiological consequences of a graded reduction in Pgm3 activity and global UDP-GlcNAc levels. Whereas mice lacking Pgm3 die prior to implantation, animals with less severe reductions in enzyme activity are sterile, exhibit changes in pancreatic architecture, and are anemic, leukopenic, and thrombocytopenic. These phenotypes are accompanied by specific rather than wholesale changes in protein glycosylation, suggesting that while universally required, the functions of certain proteins and, as a consequence, certain cell types are especially sensitive to reductions in Pgm3 activity.
Assuntos
Desenvolvimento Embrionário , Hematopoese , Fosfoglucomutase/metabolismo , Uridina Difosfato N-Acetilglicosamina/biossíntese , Alelos , Animais , Sequência de Bases , Feminino , Glicosilação , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Dados de Sequência Molecular , Mutação/genética , Pâncreas/anormalidades , Fosfoglucomutase/genética , Splicing de RNA/genética , Glândulas Salivares/anormalidades , EspermatogêneseRESUMO
SOCS-6 is a member of the suppressor of cytokine signaling (SOCS) family of proteins (SOCS-1 to SOCS-7 and CIS) which each contain a central SH2 domain and a carboxyl-terminal SOCS box. SOCS-1, SOCS-2, SOCS-3, and CIS act to negatively regulate cytokine-induced signaling pathways; however, the actions of SOCS-4, SOCS-5, SOCS-6, and SOCS-7 remain less clear. Here we have used both biochemical and genetic approaches to examine the action of SOCS-6. We found that SOCS-6 and SOCS-7 are expressed ubiquitously in murine tissues. Like other SOCS family members, SOCS-6 binds to elongins B and C through its SOCS box, suggesting that it might act as an E3 ubiquitin ligase that targets proteins bound to its SH2 domain for ubiquitination and proteasomal degradation. We investigated the binding specificity of the SOCS-6 and SOCS-7 SH2 domains and found that they preferentially bound to phosphopeptides containing a valine in the phosphotyrosine (pY) +1 position and a hydrophobic residue in the pY +2 and pY +3 positions. In addition, these SH2 domains interacted with a protein complex consisting of insulin receptor substrate 4 (IRS-4), IRS-2, and the p85 regulatory subunit of phosphatidylinositol 3-kinase. To investigate the physiological role of SOCS-6, we generated mice lacking the SOCS-6 gene. SOCS-6(-/-) mice were born in a normal Mendelian ratio, were fertile, developed normally, and did not exhibit defects in hematopoiesis or glucose homeostasis. However, both male and female SOCS-6(-/-) mice weighed approximately 10% less than wild-type littermates.
Assuntos
Crescimento/genética , Fosfoproteínas/metabolismo , Proteínas/genética , Proteínas/metabolismo , Animais , Sítios de Ligação , Glicemia/análise , Constituição Corporal/genética , Elonguina , Feminino , Sistema Hematopoético/metabolismo , Insulina/sangue , Proteínas Substratos do Receptor de Insulina , Peptídeos e Proteínas de Sinalização Intracelular , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Fosfatidilinositol 3-Quinases/metabolismo , Fatores de Transcrição/metabolismo , Domínios de Homologia de srcRESUMO
Suppressor of cytokine signaling (SOCS) family proteins were initially identified as inhibiting cytokine signaling pathways through a negative feedback loop involving the inhibition of Janus kinase activity. More recent data suggest that SOCS proteins may also modulate signaling mediated through receptor tyrosine kinases. Krebs and Hilton discuss research implicating SOCS-1 and SOCS-3 as inhibitors of insulin receptor-mediated and insulin-like growth factor-1 receptor-mediated signaling pathways, as well as the increasing evidence that SOCS proteins may act in part by participating in a ubiquitin ligase complex to promote the degradation of target proteins.
Assuntos
Proteínas de Transporte/fisiologia , Citocinas/antagonistas & inibidores , Proteínas de Ligação a DNA , Proteínas de Drosophila/fisiologia , Peptídeos e Proteínas de Sinalização Intracelular , Proteínas Nucleares/fisiologia , Proteínas/fisiologia , Proteínas Repressoras/fisiologia , Transdução de Sinais/fisiologia , Transativadores , Fatores de Transcrição , Animais , Citocinas/fisiologia , Humanos , Proteína 1 Supressora da Sinalização de Citocina , Proteína 3 Supressora da Sinalização de Citocinas , Proteínas Supressoras da Sinalização de Citocina , Domínios de Homologia de src/fisiologiaRESUMO
Cancer is associated with immune dysfunction characterized by the presence of proinflammatory and immunosuppressive cells and factors that contribute to tumor growth and progression. Here we show that mammary tumor growth is associated with defects in hematopoiesis, leading to myeloproliferative-like disease (leukemoid reaction), anemia, and disruption of the bone marrow stem/progenitor compartment. The defects we characterized included impaired erythropoiesis, leukocytosis, loss of early progenitor cells in the bone marrow, and splenic extramedullary hematopoiesis. We established an in vitro model to dissect interactions between mammary cancers and the hematopoietic system. Investigations in this model revealed that granulocyte colony-stimulating factor (G-CSF) produced by mammary tumors can synergize with FLT3L and granulocyte macrophage CSF (GM-CSF) to expand myeloid progenitors and their progeny in culture. Mammary tumor growth was associated with histone methylation changes within lineage-negative c-Kit-positive hematopoietic cells within the bone marrow of tumor-bearing mice. Similarly, parallel histone methylation patterns occurred in cultured bone marrow cells exposed to mammary tumor-conditioned cell culture media. Notably, changes in histone methylation in these cell populations correlated with dysregulated expression of genes controlling hematopoietic lineage commitment and differentiation, including Hox family genes and members of the Polycomb repressive complex 2 (PRC2) chromatin-remodeling complex. Together, our results show that mammary tumor-secreted factors induce profound perturbations in hematopoiesis and expression of key hematopoietic regulatory genes.
Assuntos
Epigenômica , Genes Homeobox/fisiologia , Hematopoese/genética , Células-Tronco Hematopoéticas/metabolismo , Neoplasias Mamárias Experimentais/patologia , Proteínas de Membrana/metabolismo , Anemia/etiologia , Anemia/patologia , Animais , Western Blotting , Medula Óssea/metabolismo , Medula Óssea/patologia , Diferenciação Celular , Proliferação de Células , Imunoprecipitação da Cromatina , Metilação de DNA , Feminino , Citometria de Fluxo , Fator Estimulador de Colônias de Granulócitos , Fator Estimulador de Colônias de Granulócitos e Macrófagos , Células-Tronco Hematopoéticas/citologia , Histonas/metabolismo , Leucocitose/etiologia , Leucocitose/patologia , Masculino , Neoplasias Mamárias Experimentais/complicações , Neoplasias Mamárias Experimentais/genética , Proteínas de Membrana/genética , Camundongos , Camundongos Endogâmicos C57BL , RNA Mensageiro/genética , Reação em Cadeia da Polimerase em Tempo Real , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
To identify new potential substrates for the MAP kinase signal-integrating kinases (Mnks), we employed a proteomic approach. The Mnks are targeted to the translational machinery through their interaction with the cap-binding initiation factor complex. We tested whether proteins retained on cap resin were substrates for the Mnks in vitro, and identified one such protein as PSF (the PTB (polypyrimidine tract-binding protein)-associated splicing factor). Mnks phosphorylate PSF at two sites in vitro, and our data show that PSF is an Mnk substrate in vivo. We also demonstrate that PSF, together with its partner, p54(nrb), binds RNAs that contain AU-rich elements (AREs), such as those for proinflammatory cytokines (e.g. tumor necrosis factor alpha (TNFalpha)). Indeed, PSF associates specifically with the TNFalpha mRNA in living cells. PSF is phosphorylated at two sites by the Mnks. Our data show that Mnk-mediated phosphorylation increases the binding of PSF to the TNFalpha mRNA in living cells. These findings identify a novel Mnk substrate. They also suggest that the Mnk-catalyzed phosphorylation of PSF may regulate the fate of specific mRNAs by modulating their binding to PSF.p54(nrb).
Assuntos
Proteínas Associadas à Matriz Nuclear/metabolismo , Fatores de Transcrição de Octâmero/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA/metabolismo , Fator de Necrose Tumoral alfa/genética , Regiões 3' não Traduzidas/metabolismo , Linhagem Celular , Cromatografia de Afinidade , Proteínas de Ligação a DNA , Eletroforese em Gel de Poliacrilamida , Humanos , Immunoblotting , Imunoprecipitação , Células Jurkat , Proteínas Associadas à Matriz Nuclear/genética , Fatores de Transcrição de Octâmero/genética , Fator de Processamento Associado a PTB , Fosforilação , Ligação Proteica , Proteínas de Ligação a RNA/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Especificidade por Substrato , TransfecçãoRESUMO
The mechanisms regulating the size of the cerebral cortex are poorly understood. Here, we demonstrate that the Rap1 guanine nucleotide exchange factor, C3G (Grf2, Rapgef1), controls the size of the cerebral precursor population. Mice lacking C3G show overproliferation of the cortical neuroepithelium. C3G-deficient neuroepithelial cells accumulate nuclear beta-catenin and fail to exit the cell cycle in vivo. C3G mutant neural precursor cells fail to activate Rap1, exhibit activation of Akt/PKB, inhibition of the beta-catenin-degrading enzyme, Gsk3beta and accumulation of cytosolic and nuclear beta-catenin when exposed to growth factors, in vitro. Our results show that the size of the cortical neural precursor population is controlled by C3G-mediated inhibition of the Ras signalling pathway.
Assuntos
Córtex Cerebral/embriologia , Fator 2 de Liberação do Nucleotídeo Guanina/fisiologia , Neurônios/citologia , Animais , Núcleo Celular/metabolismo , Proliferação de Células , Córtex Cerebral/citologia , Córtex Cerebral/crescimento & desenvolvimento , Citosol/metabolismo , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Fator 2 de Crescimento de Fibroblastos/metabolismo , Quinase 3 da Glicogênio Sintase/metabolismo , Glicogênio Sintase Quinase 3 beta , Fator 2 de Liberação do Nucleotídeo Guanina/genética , Camundongos , Mitógenos/metabolismo , Proteína Oncogênica v-akt/metabolismo , Fosforilação , Transdução de Sinais , beta Catenina/metabolismo , Proteínas rap1 de Ligação ao GTP/metabolismoRESUMO
Negative feedback is a mechanism commonly employed in biological processes as a means of maintaining homeostasis. We have investigated the roles of suppressor of cytokine signaling (SOCS) proteins in regulating the kinetics of negative feedback in response to cytokine signaling. In mouse livers and bone marrow-derived macrophages, both interferon-gamma (IFNgamma) and interleukin-6 (IL-6) rapidly induced the tyrosine phosphorylation of signal transducer and activator of transcription-1 (STAT1) and STAT3. STAT3 tyrosine phosphorylation was bi-phasic in response to continuous IL-6 signaling. In macrophages lacking Socs3, however, continuous IL-6 signaling induced uniformly high levels of STAT3 tyrosine phosphorylation, and early IL-6-inducible genes were inappropriately expressed at intermediate time points. SOCS3 therefore imposes bi-phasic kinetics upon IL-6 signaling. Compared with Socs3 mRNA, Socs1 mRNA was induced relatively slowly, and SOCS1 simply attenuated the duration of IFNgamma signaling. Surprisingly, heightened Socs1 mRNA expression but minimal STAT1 tyrosine phosphorylation was observed after prolonged stimulation with IFNgamma, indicating that STAT1 may not play a large role in inducing Socs1 mRNA during steady-state IFNgamma signaling. We also demonstrate that both SOCS1 and SOCS3 can desensitize primary bone marrow-derived macrophages to IFNgamma and IL-6 signaling, respectively. Consistent with the kinetics with which Socs1 and Socs3 mRNAs were induced, SOCS3 desensitized cells to IL-6 rapidly, whereas SOCS1-mediated desensitization to IFNgamma occurred at later time points. The kinetics with which SOCS proteins are induced by cytokine may therefore be a parameter that is "hard-wired" into specific cytokine signaling pathways as a means of tailoring the kinetics with which cells become desensitized.
Assuntos
Proteínas de Transporte/metabolismo , Proteínas Repressoras/metabolismo , Proteínas Supressoras da Sinalização de Citocina/metabolismo , Animais , Western Blotting , Células da Medula Óssea/metabolismo , Análise por Conglomerados , Citocinas/metabolismo , DNA Complementar/metabolismo , Imunoprecipitação , Interferon gama/metabolismo , Interleucina-6/metabolismo , Cinética , Macrófagos/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Análise de Sequência com Séries de Oligonucleotídeos , Fosforilação , Reação em Cadeia da Polimerase , RNA/metabolismo , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transdução de Sinais , Proteína 1 Supressora da Sinalização de Citocina , Proteína 3 Supressora da Sinalização de Citocinas , Fatores de Tempo , Tirosina/químicaRESUMO
We have generated mice from a N-ethyl-N-nitrosourea mutagenesis screen that carry a mutation in the translation initiation codon of Gata-1, termed Plt13, which is equivalent to mutations found in patients with acute megakaryoblastic leukemia and Down syndrome. The Gata-1 locus is present on the X chromosome in humans and in mice. Male mice hemizygous for the mutation (Gata-1Plt13/Y) failed to produce red blood cells and died during embryogenesis at a similar stage to Gata-1-null animals. Female mice that carry the Plt13 mutation are mosaic because of random inactivation of the X chromosome. Adult Gata-1Plt13/+ females were not anemic, but they were thrombocytopenic and accumulated abnormal megakaryocytes without a concomitant increase in megakaryocyte progenitor cells. Gata-1Plt13/+ mice contained large numbers of blast-like colony-forming cells, particularly in the fetal liver, but also in adult spleen and bone marrow, from which continuous mast cells lines were readily derived. Although the equivalent mutation to Gata-1Plt13 in humans results in production of GATA-1s, a short protein isoform initiated from a start codon downstream of the mutated initiation codon, Gata-1s was not detected in Gata-1Plt13/+ mice.
Assuntos
Diferenciação Celular/fisiologia , Códon , Fator de Transcrição GATA1/genética , Megacariócitos/fisiologia , Mutação , Trombocitopenia/genética , Sítio de Iniciação de Transcrição , Alquilantes/metabolismo , Animais , Células da Medula Óssea/citologia , Células da Medula Óssea/fisiologia , Etilnitrosoureia/metabolismo , Feminino , Fator de Transcrição GATA1/metabolismo , Células-Tronco Hematopoéticas/citologia , Células-Tronco Hematopoéticas/fisiologia , Humanos , Masculino , Megacariócitos/citologia , Camundongos , Camundongos Endogâmicos , Biossíntese de Proteínas , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Baço/citologia , Trombocitopenia/metabolismoRESUMO
SOCS7 is a member of the suppressor of cytokine signaling (SOCS) family of proteins (SOCS1-SOCS7 and CIS). SOCS proteins are composed of an N-terminal domain of variable length, a central Src homology 2 domain, and a C-terminal SOCS box. Biochemical and genetic studies have revealed that SOCS1, SOCS2, SOCS3, and CIS play an important role in the termination of cytokine and growth factor signaling. However, the biological actions of other SOCS proteins are less well defined. To investigate the physiological role of SOCS7, we have used gene targeting to generate mice that lack expression of the Socs7 gene. Socs7-/- mice were born in expected numbers, were fertile, and did not exhibit defects in hematopoiesis or circulating glucose or insulin concentrations. However, Socs7-/- mice were 7-10% smaller than their wild-type littermates, and within 15 weeks of age approximately 50% of the Socs7-/- mice died as a result of hydrocephalus that was characterized by cranial distortion, dilation of the ventricular system, reduced thickness of the cerebral cortex, and disorganization of the subcommissural organ. In situ hybridization studies revealed prominent expression of Socs7 in the brain, suggestive of an important functional role of SOCS7 in this organ.
Assuntos
Hidrocefalia/genética , Proteínas Nucleares/genética , Animais , Citometria de Fluxo , Expressão Gênica , Glucose/metabolismo , Crescimento , Homeostase , Hidrocefalia/líquido cefalorraquidiano , Hidrocefalia/fisiopatologia , Camundongos , Camundongos Knockout , Proteínas Supressoras da Sinalização de CitocinaRESUMO
Members of the suppressor of cytokine signaling (SOCS) family are potentially key physiological negative regulators of interleukin-6 (IL-6) signaling. To examine whether SOCS3 is involved in regulating this signaling, we have used conditional gene targeting to generate mice lacking Socs3 in the liver or in macrophages. We show that Socs3 deficiency results in prolonged activation of signal transducer and activator of transcription 1 (STAT1) and STAT3 after IL-6 stimulation but normal activation of STAT1 after stimulation with interferon-gamma (IFN-gamma). Conversely, IL-6-induced STAT activation is normal in Socs1-deficient cells, whereas STAT1 activation induced by IFN-gamma is prolonged. Microarray analysis shows that the pattern of gene expression induced by IL-6 in Socs3-deficient livers mimics that induced by IFN-gamma. Our data indicate that SOCS3 and SOCS1 have reciprocal functions in IL-6 and IFN-gamma regulation and imply that SOCS3 has a role in preventing IFN-gamma-like responses in cells stimulated by IL-6.