RESUMO
Little is known about how mammalian cells maintain cell size homeostasis. We conducted a novel genetic screen to identify cell-size-controlling genes and isolated Largen, the product of a gene (PRR16) that increased cell size upon overexpression in human cells. In vitro evidence indicated that Largen preferentially stimulates the translation of specific subsets of mRNAs, including those encoding proteins affecting mitochondrial functions. The involvement of Largen in mitochondrial respiration was consistent with the increased mitochondrial mass and greater ATP production in Largen-overexpressing cells. Furthermore, Largen overexpression led to increased cell size in vivo, as revealed by analyses of conditional Largen transgenic mice. Our results establish Largen as an important link between mRNA translation, mitochondrial functions, and the control of mammalian cell size.
Assuntos
Tamanho Celular/efeitos dos fármacos , Regulação da Expressão Gênica , Biossíntese de Proteínas , Proteínas/genética , RNA Mensageiro/genética , Animais , Linhagem Celular Tumoral , Escherichia coli/genética , Escherichia coli/metabolismo , Vetores Genéticos , Ensaios de Triagem em Larga Escala , Humanos , Células Jurkat , Camundongos , Camundongos Transgênicos , Mitocôndrias/genética , Mitocôndrias/metabolismo , Proteínas/metabolismo , RNA Mensageiro/metabolismo , Retroviridae/genética , Retroviridae/metabolismo , Transdução de Sinais/efeitos dos fármacos , Sirolimo/farmacologiaRESUMO
The primary forms of cell death seen in ischemic stroke are of two major types: a necrotic/necroptotic form, and an apoptotic form that is frequently seen in penumbral regions of injury. Typically apoptotic versus necroptotic programmed cell death is described as competitive in nature, where necroptosis is often described as playing a backup role to apoptosis. In the present study, we examined the relationship between these two forms of cell death in a murine endothelin-1 model of ischemia-reperfusion injury in wildtype and caspase-3 null mice with and without addition of the pharmacologic RIPK1 phosphorylation inhibitor necrostatin-1. Analyses of ischemic brain injury were performed via both cellular and volumetric assessments, electron microscopy, TUNEL staining, activated caspase-3 and caspase-7 staining, as well as CD11b and F4/80 staining. Inhibition of caspase-3 or RIPK1 phosphorylation demonstrates significant neural protective effects which are non-additive and exhibit significant overlap in protected regions. Interestingly, morphologic analysis of the cortex demonstrates reduced apoptosis following RIPK1 inhibition. Consistent with this, RIPK1 inhibition reduces the levels of both caspase-3 and caspase-7 activation. Additionally, this protection appears independent of secondary inflammatory mediators. Together, these observations demonstrate that the necroptotic protein RIPK1 modifies caspase-3/-7 activity, ultimately resulting in decreased neuronal apoptosis. These findings thus modify the traditional exclusionary view of apoptotic/necroptotic signaling, revealing a new form of interaction between these dominant forms of cell death.
Assuntos
Apoptose/efeitos dos fármacos , Isquemia Encefálica/induzido quimicamente , Isquemia Encefálica/patologia , Endotelina-1/toxicidade , Animais , Apoptose/fisiologia , Isquemia Encefálica/metabolismo , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Necrose/induzido quimicamente , Necrose/metabolismo , Necrose/patologia , Proteína Serina-Treonina Quinases de Interação com Receptores/metabolismoRESUMO
Tumorigenesis results from dysregulation of oncogenes and tumor suppressors that influence cellular proliferation, differentiation, apoptosis, and/or senescence. Many gene products involved in these processes are substrates of the E3 ubiquitin ligase Mule/Huwe1/Arf-BP1 (Mule), but whether Mule acts as an oncogene or tumor suppressor in vivo remains controversial. We generated K14Cre;Mule(flox/flox(y)) (Mule kKO) mice and subjected them to DMBA/PMA-induced skin carcinogenesis, which depends on oncogenic Ras signaling. Mule deficiency resulted in increased penetrance, number, and severity of skin tumors, which could be reversed by concomitant genetic knockout of c-Myc but not by knockout of p53 or p19Arf. Notably, in the absence of Mule, c-Myc/Miz1 transcriptional complexes accumulated, and levels of p21CDKN1A (p21) and p15INK4B (p15) were down-regulated. In vitro, Mule-deficient primary keratinocytes exhibited increased proliferation that could be reversed by Miz1 knockdown. Transfer of Mule-deficient transformed cells to nude mice resulted in enhanced tumor growth that again could be abrogated by Miz1 knockdown. Our data demonstrate in vivo that Mule suppresses Ras-mediated tumorigenesis by preventing an accumulation of c-Myc/Miz1 complexes that mediates p21 and p15 down-regulation.
Assuntos
Transformação Celular Neoplásica , Inibidor de Quinase Dependente de Ciclina p15/metabolismo , Inibidor de Quinase Dependente de Ciclina p21/metabolismo , Regulação para Baixo , Proteínas Nucleares/antagonistas & inibidores , Proteína Oncogênica p21(ras)/metabolismo , Proteínas Inibidoras de STAT Ativados/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-myc/antagonistas & inibidores , Ubiquitina-Proteína Ligases/metabolismo , 9,10-Dimetil-1,2-benzantraceno/farmacologia , Animais , Transformação Celular Neoplásica/genética , Células Cultivadas , Inibidor de Quinase Dependente de Ciclina p15/biossíntese , Inibidor de Quinase Dependente de Ciclina p15/genética , Inibidor p16 de Quinase Dependente de Ciclina , Inibidor de Quinase Dependente de Ciclina p21/biossíntese , Inibidor de Quinase Dependente de Ciclina p21/genética , Feminino , Genes ras , Queratinócitos/efeitos dos fármacos , Queratinócitos/metabolismo , Queratinócitos/patologia , Masculino , Camundongos , Camundongos Knockout , Proteínas Nucleares/deficiência , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Proteína Oncogênica p21(ras)/antagonistas & inibidores , Proteína Oncogênica p21(ras)/genética , Proteínas Inibidoras de STAT Ativados/deficiência , Proteínas Inibidoras de STAT Ativados/genética , Proteínas Inibidoras de STAT Ativados/metabolismo , Proteínas Proto-Oncogênicas c-myc/deficiência , Proteínas Proto-Oncogênicas c-myc/genética , Proteínas Proto-Oncogênicas c-myc/metabolismo , Transdução de Sinais , Neoplasias Cutâneas/induzido quimicamente , Neoplasias Cutâneas/genética , Neoplasias Cutâneas/metabolismo , Neoplasias Cutâneas/patologia , Acetato de Tetradecanoilforbol/farmacologia , Proteína Supressora de Tumor p53 , Proteínas Supressoras de Tumor , Ubiquitina-Proteína Ligases/deficiência , Ubiquitina-Proteína Ligases/genéticaRESUMO
Wnt signaling, named after the secreted proteins that bind to cell surface receptors to activate the pathway, plays critical roles both in embryonic development and the maintenance of homeostasis in many adult tissues. Two particularly important cellular programs orchestrated by Wnt signaling are proliferation and stem cell self-renewal. Constitutive activation of the Wnt pathway resulting from mutation or improper modulation of pathway components contributes to cancer development in various tissues. Colon cancers frequently bear inactivating mutations of the adenomatous polyposis coli (APC) gene, whose product is an important component of the destruction complex that regulates ß-catenin levels. Stabilization and nuclear localization of ß-catenin result in the expression of a panel of Wnt target genes. We previously showed that Mule/Huwe1/Arf-BP1 (Mule) controls murine intestinal stem and progenitor cell proliferation by modulating the Wnt pathway via c-Myc. Here we extend our investigation of Mule's influence on oncogenesis by showing that Mule interacts directly with ß-catenin and targets it for degradation under conditions of hyperactive Wnt signaling. Our findings suggest that Mule uses various mechanisms to fine-tune the Wnt pathway and provides multiple safeguards against tumorigenesis.
Assuntos
Proteínas Supressoras de Tumor/fisiologia , Ubiquitina-Proteína Ligases/fisiologia , Via de Sinalização Wnt , beta Catenina/antagonistas & inibidores , Proteína da Polipose Adenomatosa do Colo/deficiência , Animais , Proteína Axina/biossíntese , Proteína Axina/genética , Núcleo Celular/metabolismo , Núcleo Celular/ultraestrutura , Neoplasias do Colo/metabolismo , Ciclina D1/biossíntese , Ciclina D1/genética , Regulação para Baixo , Genes APC , Genes Supressores de Tumor , Células HEK293 , Humanos , Camundongos , Camundongos Knockout , Proteínas de Neoplasias/fisiologia , Organoides/metabolismo , Organoides/ultraestrutura , Ligação Proteica , Processamento de Proteína Pós-Traducional , Proteólise , Interferência de RNA , RNA Interferente Pequeno/genética , Proteínas Recombinantes/metabolismo , Proteínas Supressoras de Tumor/antagonistas & inibidores , Proteínas Supressoras de Tumor/deficiência , Proteínas Supressoras de Tumor/genética , Ubiquitina-Proteína Ligases/antagonistas & inibidores , Ubiquitina-Proteína Ligases/deficiência , Ubiquitina-Proteína Ligases/genética , UbiquitinaçãoRESUMO
Isocitrate dehydrogenase-1 (IDH1) R132 mutations occur in glioma, but their physiological significance is unknown. Here we describe the generation and characterization of brain-specific Idh1 R132H conditional knock-in (KI) mice. Idh1 mutation results in hemorrhage and perinatal lethality. Surprisingly, intracellular reactive oxygen species (ROS) are attenuated in Idh1-KI brain cells despite an apparent increase in the NADP(+)/NADPH ratio. Idh1-KI cells also show high levels of D-2-hydroxyglutarate (D2HG) that are associated with inhibited prolyl-hydroxylation of hypoxia-inducible transcription factor-1α (Hif1α) and up-regulated Hif1α target gene transcription. Intriguingly, D2HG also blocks prolyl-hydroxylation of collagen, causing a defect in collagen protein maturation. An endoplasmic reticulum (ER) stress response induced by the accumulation of immature collagens may account for the embryonic lethality of these mutants. Importantly, D2HG-mediated impairment of collagen maturation also led to basement membrane (BM) aberrations that could play a part in glioma progression. Our study presents strong in vivo evidence that the D2HG produced by the mutant Idh1 enzyme is responsible for the above effects.
Assuntos
Membrana Basal/patologia , Colágeno/metabolismo , Glutaratos/metabolismo , Isocitrato Desidrogenase/genética , Isocitrato Desidrogenase/metabolismo , Animais , Membrana Basal/metabolismo , Encéfalo/citologia , Encéfalo/patologia , Técnicas de Introdução de Genes , Genótipo , Glioma/patologia , Camundongos , Mutação , Estabilidade Proteica , Espécies Reativas de Oxigênio/metabolismo , Estresse FisiológicoRESUMO
Over the past 30 years a number of animal models of cerebral ischemic injury have been developed. Middle cerebral artery occlusion (MCAO) in particular reproduces both ischemic and reperfusion elements and is widely utilized as a model of ischemic stroke in rodents. However substantial variability exists in this model even in clonal inbred mice due to stochastic elements of the cerebral vasculature. Models such as MCAO thus exhibit significant irreducible variabilities with respect to their zone of injury as well as inducing a sizable volume of injury to the cerebrum with damage to sub-cortical structures, conditions not typically seen for the majority of human clinical strokes. An alternative model utilizes endothelin-1 application focally to cerebral vasculature, resulting in an ischemic reperfusion injury which more closely mimics that seen in human clinical stroke. In order to further define this model we demonstrate that intra-cortical administration of ET-1 results in a highly reproducible pattern of tissue injury which is limited to the cerebral cortex, characterizing the early cellular and molecular events which occur during the first 24 h post-injury. In addition we demonstrate that caspase-3 is both necessary and sufficient to regulate a majority of cortical cell death observed during this period. The enhanced survival effects seen upon genetic deletion of caspase-3 appear to arise as a result of direct modification of cell autonomous PCD signaling as opposed to secondary effectors such as granulocyte infiltration or microglia activation. Taken together these findings detail the early mechanistic features regulating endothelin-1-mediated ischemic injury.
Assuntos
Isquemia Encefálica/induzido quimicamente , Caspase 3/metabolismo , Córtex Cerebral/efeitos dos fármacos , Endotelina-1/toxicidade , Animais , Isquemia Encefálica/patologia , Caspase 3/genética , Morte Celular/efeitos dos fármacos , Córtex Cerebral/lesões , Córtex Cerebral/patologia , Modelos Animais de Doenças , Endotelina-1/administração & dosagem , Técnicas de Inativação de Genes , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neurônios/efeitos dos fármacos , Neurônios/enzimologia , Neurônios/patologiaRESUMO
The generation of viable sperm proceeds through a series of coordinated steps, including germ cell self-renewal, meiotic recombination, and terminal differentiation into functional spermatozoa. The p53 family of transcription factors, including p53, p63, and p73, are critical for many physiological processes, including female fertility, but little is known about their functions in spermatogenesis. Here, we report that deficiency of the TAp73 isoform, but not p53 or ΔNp73, results in male infertility because of severe impairment of spermatogenesis. Mice lacking TAp73 exhibited increased DNA damage and cell death in spermatogonia, disorganized apical ectoplasmic specialization, malformed spermatids, and marked hyperspermia. We demonstrated that TAp73 regulates the mRNA levels of crucial genes involved in germ stem/progenitor cells (CDKN2B), spermatid maturation/spermiogenesis (metalloproteinase and serine proteinase inhibitors), and steroidogenesis (CYP21A2 and progesterone receptor). These alterations of testicular histology and gene expression patterns were specific to TAp73 null mice and not features of mice lacking p53. Our work provides previously unidentified in vivo evidence that TAp73 has a unique role in spermatogenesis that ensures the maintenance of mitotic cells and normal spermiogenesis. These results may have implications for the diagnosis and management of human male infertility.
Assuntos
Proteínas de Ligação a DNA/metabolismo , Fertilidade , Proteínas Nucleares/metabolismo , Espermatogênese , Proteínas Supressoras de Tumor/metabolismo , Proteínas ADAM/genética , Proteínas ADAM/metabolismo , Proteína ADAM17 , Envelhecimento/patologia , Animais , Apoptose/genética , Contagem de Células , Proliferação de Células , Dano ao DNA/genética , Proteínas de Ligação a DNA/deficiência , Feminino , Fertilidade/genética , Regulação da Expressão Gênica , Humanos , Infertilidade Masculina/sangue , Infertilidade Masculina/genética , Infertilidade Masculina/patologia , Masculino , Metaloproteinase 13 da Matriz/genética , Metaloproteinase 13 da Matriz/metabolismo , Camundongos , Camundongos Knockout , Proteínas Nucleares/deficiência , Estresse Oxidativo/genética , Progesterona/sangue , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Espermatogênese/genética , Espermatozoides/metabolismo , Espermatozoides/patologia , Testículo/metabolismo , Testículo/patologia , Proteína Tumoral p73 , Proteínas Supressoras de Tumor/deficiênciaRESUMO
Pancreatic endocrine cells expand rapidly during embryogenesis by neogenesis and proliferation, but during adulthood, islet cells have a very slow turnover. Disruption of murine retinoblastoma tumor suppressor protein (Rb) in mature pancreatic ß-cells has a limited effect on cell proliferation. Here we show that deletion of Rb during embryogenesis in islet progenitors leads to an increase in the neurogenin 3-expressing precursor cell population, which persists in the postnatal period and is associated with increased ß-cell mass in adults. In contrast, Rb-deficient islet precursors, through repression of the cell fate factor aristaless related homeobox, result in decreased α-cell mass. The opposing effect on survival of Rb-deficient α- and ß-cells was a result of opposing effects on p53 in these cell types. As a consequence, loss of Rb in islet precursors led to a reduced α- to ß-cell ratio, leading to improved glucose homeostasis and protection against diabetes.
Assuntos
Células Secretoras de Glucagon/metabolismo , Células Secretoras de Insulina/metabolismo , Ilhotas Pancreáticas/metabolismo , Proteína do Retinoblastoma/metabolismo , Células-Tronco/metabolismo , Animais , Animais Recém-Nascidos , Sequência de Bases , Diferenciação Celular/genética , Linhagem Celular Tumoral , Sobrevivência Celular/genética , Diabetes Mellitus Experimental/genética , Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Experimental/patologia , Fator de Transcrição E2F1/genética , Fator de Transcrição E2F1/metabolismo , Feminino , Células Secretoras de Glucagon/citologia , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Imuno-Histoquímica , Células Secretoras de Insulina/citologia , Ilhotas Pancreáticas/citologia , Masculino , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Interferência de RNA , Proteína do Retinoblastoma/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Homologia de Sequência do Ácido Nucleico , Células-Tronco/citologia , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Proteína Supressora de Tumor p53/genética , Proteína Supressora de Tumor p53/metabolismoRESUMO
The endogenous metabolite of estradiol, 2-Methoxyestradiol (2ME2), is an antimitotic and antiangiogenic cancer drug candidate that also exhibits disease-modifying activity in animal models of rheumatoid arthritis (RA). We found that 2ME2 dramatically suppresses development of mouse experimental autoimmune encephalomyelitis (EAE), a rodent model of multiple sclerosis (MS). 2ME2 inhibits in vitro lymphocyte activation, cytokine production, and proliferation in a dose-dependent fashion. 2ME2 treatment of lymphocytes specifically reduced the nuclear translocation and transcriptional activity of nuclear factor of activated T-cells (NFAT) c1, whereas NF-κB and activator protein 1 (AP-1) activation were not adversely affected. We therefore propose that 2ME2 attenuates EAE through disruption of the NFAT pathway and subsequent lymphocyte activation. By extension, our findings provide a molecular rationale for the use of 2ME2 as a tolerable oral immunomodulatory agent for the treatment of autoimmune disorders such as MS in humans.
Assuntos
Encefalomielite Autoimune Experimental/tratamento farmacológico , Estradiol/análogos & derivados , 2-Metoxiestradiol , Animais , Autoimunidade , Linfócitos T CD4-Positivos/citologia , Citocinas/biossíntese , Estradiol/farmacologia , Humanos , Ativação Linfocitária , Linfócitos/citologia , Camundongos , Camundongos Endogâmicos C57BL , Esclerose Múltipla/imunologia , NF-kappa B/metabolismo , Fatores de Transcrição NFATC/metabolismo , Transdução de Sinais , Fator de Transcrição AP-1/metabolismo , Moduladores de Tubulina/farmacologiaRESUMO
The highly conserved ANP32 proteins are proposed to function in a broad array of physiological activities through molecular mechanisms as diverse as phosphatase inhibition, chromatin regulation, caspase activation, and intracellular transport. On the basis of previous analyses of mice bearing targeted mutations of Anp32a or Anp32e, there has been speculation that all ANP32 proteins play redundant roles and are dispensable for normal development. However, more recent work has suggested that ANP32B may in fact have functions that are not shared by other ANP32 family members. Here we report that ANP32B expression is associated with a poor prognosis in human breast cancer, consistent with the increased levels of Anp32b mRNA present in proliferating wild-type (WT) murine embryonic fibroblasts and stimulated WT B and T lymphocytes. Moreover, we show that, contrary to previous assumptions, Anp32b is very important for murine embryogenesis. In a mixed genetic background, ANP32B-deficient mice displayed a partially penetrant perinatal lethality that became fully penetrant in a pure C57BL/6 background. Surviving ANP32B-deficient mice showed reduced viability due to variable defects in various organ systems. Study of compound mutants lacking ANP32A, ANP32B, and/or ANP32E revealed previously hidden roles for ANP32A in mouse development that became apparent only in the complete absence of ANP32B. Our data demonstrate a hierarchy of importance for the mammalian Anp32 genes, with Anp32b being the most critical for normal development.
Assuntos
Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Embrião de Mamíferos/fisiologia , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Animais , Apoptose , Biomarcadores Tumorais/metabolismo , Neoplasias da Mama/metabolismo , Neoplasias da Mama/patologia , Proliferação de Células , Células Cultivadas , Embrião de Mamíferos/anatomia & histologia , Feminino , Fibroblastos/citologia , Fibroblastos/fisiologia , Marcação de Genes , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mutação , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Taxa de SobrevidaRESUMO
Based largely on studies in xenograft models, lipocalin-2 (Lcn2) has been implicated in the progression of multiple types of human tumors, including breast cancer. Here we examine the role of Lcn2 in mammary tumorigenesis and lung metastasis using an in vivo molecular genetics approach. We crossed a well-characterized transgenic mouse model of breast cancer, the MMTV-PyMT (mouse mammary tumor virus-polyoma middle T antigen) mouse, with two independent gene-targeted Lcn2(-/-) mouse strains of the 129/Ola or C57BL/6 genetic background. The onset and progression of mammary tumor development and lung metastasis in the female progeny of these crosses were monitored over a 20-week period. Female Lcn2(-/-)MMTV-PyMT mice of the 129/Ola background (Lcn2(-/-)PyMT(129)) showed delayed onset of mammary tumors, and both Lcn2(-/-)PyMT(129) mice and Lcn2(-/-)MMTV-PyMT mice of the C57BL/6 background (Lcn2(-/-)PyMT(B6)) exhibited significant decreases in multiplicity and tumor burden (approximately 2- to 3-fold), as measured by total tumor weight and volume. At the molecular level, mammary tumors derived from Lcn2(-/-)PyMT(B6) females showed reduced matrix metalloproteinase-9 (MMP-9) activity and a lack of high molecular weight MMP activity. However, although increased MMP-9 activity has been linked to tumor progression, neither Lcn2(-/-)PyMT(B6) nor Lcn2(-/-)PyMT(129) female mice showed a reduction in lung metastases compared to Lcn2(+/+)PyMT controls. Our results demonstrate, using an in vivo animal model approach, that Lcn2 is a potent inducer of mammary tumor growth but not a significant promoter of lung metastasis.
Assuntos
Proteínas de Fase Aguda/genética , Lipocalinas/genética , Neoplasias Pulmonares/genética , Neoplasias Mamárias Animais/genética , Metástase Neoplásica/genética , Proteínas Oncogênicas/genética , Animais , Western Blotting , Cruzamentos Genéticos , Eletroforese em Gel de Poliacrilamida , Feminino , Técnicas Histológicas , Lipocalina-2 , Neoplasias Pulmonares/secundário , Metaloproteinase 9 da Matriz/metabolismo , Camundongos , Camundongos TransgênicosRESUMO
MAP kinase-interacting kinase 1 and 2 (Mnk1 and Mnk2) are protein-serine/threonine kinases that are activated by ERK or p38 and phosphorylate eIF4E, which is involved in cap-dependent translation initiation. However, Mnk1/2 double knockout (Mnk-DKO) mice show normal cell growth and development despite an absence of eIF4E phosphorylation. Here we show that the tumorigenesis occurring in the Lck-Pten mouse model (referred to here as tPten(-/-) mice) can be suppressed by the loss of Mnk1/2. Phosphorylation of eIF4E was greatly enhanced in lymphomas of parental tPten(-/-) mice compared with lymphoid tissues of wild-type mice, but was totally absent in lymphomas of tPten(-/-); Mnk-DKO mice. Notably, stable knockdown of Mnk1 in the human glioma cell line U87MG resulted in dramatically decreased tumor formation when these cells were injected into athymic nude mice. Our data demonstrate an oncogenic role for Mnk1/2 in tumor development, and highlight these molecules as potential anticancer drug targets that could be inactivated with minimal side effects.
Assuntos
Neoplasias/etiologia , Proteínas Serina-Treonina Quinases/deficiência , Animais , Linhagem Celular Tumoral , Fator de Iniciação 4E em Eucariotos/metabolismo , Glioma/patologia , Linfoma/etiologia , Camundongos , Camundongos Knockout , Camundongos Nus , Transplante de Neoplasias , PTEN Fosfo-Hidrolase/deficiência , Fosforilação , Proteínas Serina-Treonina Quinases/fisiologia , Transplante HeterólogoRESUMO
Smg1 is a PI3K-related kinase (PIKK) associated with multiple cellular functions, including DNA damage responses, telomere maintenance, and nonsense-mediated mRNA decay (NMD). NMD degrades transcripts that harbor premature termination codons (PTCs) as a result of events such as mutation or alternative splicing (AS). Recognition of PTCs during NMD requires the action of the Upstream frameshift protein Upf1, which must first be phosphorylated by Smg1. However, the physiological function of mammalian Smg1 is not known. By using a gene-trap model of Smg1 deficiency, we show that this kinase is essential for mouse embryogenesis such that Smg1 loss is lethal at embryonic day 8.5. High-throughput RNA sequencing (RNA-Seq) of RNA from cells of Smg1-deficient embryos revealed that Smg1 depletion led to pronounced accumulation of PTC-containing splice variant transcripts from approximately 9% of genes predicted to contain AS events capable of eliciting NMD. Among these genes are those involved in splicing itself, as well as genes not previously known to be subject to AS-coupled NMD, including several involved in transcription, intracellular signaling, membrane dynamics, cell death, and metabolism. Our results demonstrate a critical role for Smg1 in early mouse development and link the loss of this NMD factor to major and widespread changes in the mammalian transcriptome.
Assuntos
Processamento Alternativo , Embrião de Mamíferos/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Estabilidade de RNA , Animais , Células Cultivadas , Embrião de Mamíferos/citologia , Embrião de Mamíferos/embriologia , Células-Tronco Embrionárias/citologia , Células-Tronco Embrionárias/metabolismo , Feminino , Perfilação da Expressão Gênica , Genes Letais , Immunoblotting , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos , Camundongos Knockout , Fosfatidilinositol 3-Quinases/genética , Fosforilação , Proteínas Serina-Treonina Quinases/genética , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
p53 is a central player in responses to cellular stresses and a major tumor suppressor. The identification of unique molecules within the p53 signaling network can reveal functions of this important transcription factor. Here, we show that brain-expressed RING finger protein (BERP) is a gene whose expression is up-regulated in a p53-dependent manner in human cells and in mice. We generated BERP-deficient mice by gene targeting and demonstrated that they exhibit increased resistance to pentylenetetrazol-induced seizures. Electrophysiological and biochemical studies of cultured cortical neurons of BERP-deficient mice showed a decrease in the amplitude of GABA(A) receptor (GABA(A)R)-mediated miniature inhibitory postsynaptic currents as well as reduced surface protein expression of GABA(A)Rs containing the gamma2-subunit. However, BERP deficiency did not decrease GABA(A)Rgamma2 mRNA levels, raising the possibility that BERP may act at a posttranscriptional level to regulate the intracellular trafficking of GABA(A)Rs. Our results indicate that BERP is a unique p53-regulated gene and suggest a role for p53 within the central nervous system.
Assuntos
Proteínas de Transporte/genética , Proteínas do Tecido Nervoso/genética , Receptores de GABA-A/metabolismo , Convulsões/genética , Convulsões/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Animais , Sequência de Bases , Células Cultivadas , Convulsivantes/toxicidade , Primers do DNA/genética , Genes p53 , Humanos , Masculino , Camundongos , Camundongos Knockout , Proteínas do Tecido Nervoso/deficiência , Neurônios/metabolismo , Pentilenotetrazol/toxicidade , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Receptores de GABA-A/genética , Convulsões/induzido quimicamente , Regulação para CimaRESUMO
Angioimmunoblastic T cell lymphoma (AITL) is a peripheral T cell lymphoma that originates from T follicular helper (Tfh) cells and exhibits a prominent tumor microenvironment (TME). IDH2 and TET2 mutations co-occur frequently in AITL, but their contribution to tumorigenesis is poorly understood. We developed an AITL mouse model that is driven by Idh2 and Tet2 mutations. Malignant Tfh cells display aberrant transcriptomic and epigenetic programs that impair TCR signaling. Neoplastic Tfh cells bearing combined Idh2 and Tet2 mutations show altered cross-talk with germinal center B cells that promotes B cell clonal expansion while decreasing Fas-FasL interaction and reducing B cell apoptosis. The plasma cell count and angiogenesis are also increased in the Idh2-mutated tumors, implying a major relationship between Idh2 mutation and the characteristic AITL TME. Our mouse model recapitulates several features of human IDH2-mutated AITL and provides a rationale for exploring therapeutic targeting of Tfh-TME cross-talk for AITL patients.
Assuntos
Dioxigenases , Linfadenopatia Imunoblástica , Linfoma de Células T , Animais , Humanos , Camundongos , Dioxigenases/genética , Proteínas de Ligação a DNA/genética , Linfadenopatia Imunoblástica/genética , Isocitrato Desidrogenase/genética , Linfoma de Células T/genética , Mutação , Células T Auxiliares Foliculares/patologia , Linfócitos T Auxiliares-Indutores , Microambiente Tumoral/genéticaRESUMO
Cholinergic nerves are involved in tumor progression and dissemination. In contrast to other visceral tissues, cholinergic innervation in the hepatic parenchyma is poorly detected. It remains unclear whether there is any form of cholinergic regulation of liver cancer. Here, we show that cholinergic T cells curtail the development of liver cancer by supporting antitumor immune responses. In a mouse multihit model of hepatocellular carcinoma (HCC), we observed activation of the adaptive immune response and induction of two populations of CD4+ T cells expressing choline acetyltransferase (ChAT), including regulatory T cells and dysfunctional PD-1+ T cells. Tumor antigens drove the clonal expansion of these cholinergic T cells in HCC. Genetic ablation of Chat in T cells led to an increased prevalence of preneoplastic cells and exacerbated liver cancer due to compromised antitumor immunity. Mechanistically, the cholinergic activity intrinsic in T cells constrained Ca2+-NFAT signaling induced by T cell antigen receptor engagement. Without this cholinergic modulation, hyperactivated CD25+ T regulatory cells and dysregulated PD-1+ T cells impaired HCC immunosurveillance. Our results unveil a previously unappreciated role for cholinergic T cells in liver cancer immunobiology.
Assuntos
Carcinoma Hepatocelular , Neoplasias Hepáticas , Animais , Camundongos , Carcinoma Hepatocelular/genética , Neoplasias Hepáticas/genética , Receptor de Morte Celular Programada 1/genética , Monitorização Imunológica , Linfócitos T Reguladores/patologiaRESUMO
Cisplatin is a member of a widely utilized class of chemotherapeutic agent that initiates DNA damage response, cell cycle arrest, and p53-dependent apoptotic cell death in concert with DNAplatinum adduct formation. While normal programmed cell death (PCD) can occur in the developing neuroepithelium in the absence of caspase-3 within certain genetic backgrounds, we observed an absolute dependency upon this executioner caspase with respect to cisplatin-induced PCD in the developing central nervous system (CNS). We therefore examined the nature of this genotoxic injury in the CNS in vivo, in which cisplatin treatment causes widespread cellular injury consistent with hallmarks of apoptosis which are averted upon caspase-3 inhibition. Examination of cisplatin-mediated injury as a function of time revealed the presence of an alternative, delayed form of necroptosis-like cell death which manifests in Casp3-/- neuroepithelia for several days following the normal pattern of apoptosis. Together, these findings suggest a coordinated regulation of these disparate PCD pathways in response to genotoxic stress in vivo and highlight the unique and critical role which caspase-3 plays among executioner caspases in coordinating apoptotic versus necroptotic responsiveness of the developing CNS to genotoxic injury.
Assuntos
Caspases , Cisplatino , Apoptose/fisiologia , Encéfalo/metabolismo , Caspase 3/metabolismo , Caspases/metabolismo , Cisplatino/toxicidadeRESUMO
Dendritic cells are sentinels of the immune system and represent a key cell in the activation of the adaptive immune response. Hypoxia-inducible factor 1 alpha (HIF-1α)-a crucial oxygen sensor stabilized during hypoxic conditions-has been shown to have both activating and inhibitory effects in immune cells in a context- and cell-dependent manner. Previous studies have demonstrated that in some immune cell types, HIF-1α serves a pro-inflammatory role. Genetic deletion of HIF-1α in macrophages has been reported to reduce their pro-inflammatory function. In contrast, loss of HIF-1α enhanced the pro-inflammatory activity of dendritic cells in a bacterial infection model. In this study, we aimed to further clarify the effects of HIF-1α in dendritic cells. Constitutive expression of HIF-1α resulted in diminished immunostimulatory capacity of dendritic cells in vivo, while conditional deletion of HIF-1α in dendritic cells enhanced their ability to induce a cytotoxic T cell response. HIF-1α-expressing dendritic cells demonstrated increased production of inhibitory mediators including IL-10, iNOS and VEGF, which correlated with their reduced capacity to drive effector CD8+ T cell function. Altogether, these data reveal that HIF-1α can promote the anti-inflammatory functions of dendritic cells and provides insight into dysfunctional immune responses in the context of HIF-1α activation.
Assuntos
Biomarcadores/metabolismo , Linfócitos T CD8-Positivos/imunologia , Células Dendríticas/citologia , Subunidade alfa do Fator 1 Induzível por Hipóxia/genética , Animais , Células Cultivadas , Células Dendríticas/metabolismo , Técnicas de Inativação de Genes , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Interleucina-10/metabolismo , Camundongos , Óxido Nítrico Sintase Tipo II/metabolismo , Fator A de Crescimento do Endotélio Vascular/metabolismoRESUMO
Although widely studied as a neurotransmitter, T cell-derived acetylcholine (ACh) has recently been reported to play an important role in regulating immunity. However, the role of lymphocyte-derived ACh in viral infection is unknown. Here, we show that the enzyme choline acetyltransferase (ChAT), which catalyzes the rate-limiting step of ACh production, is robustly induced in both CD4+ and CD8+ T cells during lymphocytic choriomeningitis virus (LCMV) infection in an IL-21-dependent manner. Deletion of Chat within the T cell compartment in mice ablated vasodilation in response to infection, impaired the migration of antiviral T cells into infected tissues, and ultimately compromised the control of chronic LCMV clone 13 infection. Our results reveal a genetic proof of function for ChAT in T cells during viral infection and identify a pathway of T cell migration that sustains antiviral immunity.
Assuntos
Linfócitos T CD8-Positivos/imunologia , Colina O-Acetiltransferase/imunologia , Interleucinas/imunologia , Coriomeningite Linfocítica/imunologia , Animais , Linfócitos T CD4-Positivos/enzimologia , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD8-Positivos/enzimologia , Movimento Celular , Colina O-Acetiltransferase/genética , Feminino , Ativação Linfocitária , Vírus da Coriomeningite Linfocítica , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , VasodilataçãoRESUMO
In response to ionizing radiation (IR), the tumor suppressor p53 is stabilized and promotes either cell cycle arrest or apoptosis. Chk2 activated by IR contributes to this stabilization, possibly by direct phosphorylation. Like p53, Chk2 is mutated in patients with Li-Fraumeni syndrome. Since the ataxia telangiectasia mutated (ATM) gene is required for IR-induced activation of Chk2, it has been assumed that ATM and Chk2 act in a linear pathway leading to p53 activation. To clarify the role of Chk2 in tumorigenesis, we generated gene-targeted Chk2-deficient mice. Unlike ATM(-/-) and p53(-/-) mice, Chk2(-/-) mice do not spontaneously develop tumors, although Chk2 does suppress 7,12-dimethylbenzanthracene-induced skin tumors. Tissues from Chk2(-/-) mice, including those from the thymus, central nervous system, fibroblasts, epidermis, and hair follicles, show significant defects in IR-induced apoptosis or impaired G(1)/S arrest. Quantitative comparison of the G(1)/S checkpoint, apoptosis, and expression of p53 proteins in Chk2(-/-) versus ATM(-/-) thymocytes suggested that Chk2 can regulate p53-dependent apoptosis in an ATM-independent manner. IR-induced apoptosis was restored in Chk2(-/-) thymocytes by reintroduction of the wild-type Chk2 gene but not by a Chk2 gene in which the sites phosphorylated by ATM and ataxia telangiectasia and rad3(+) related (ATR) were mutated to alanine. ATR may thus selectively contribute to p53-mediated apoptosis. These data indicate that distinct pathways regulate the activation of p53 leading to cell cycle arrest or apoptosis.