RESUMEN
TLR5, which is activated by flagellin, plays an important role in initiating immune response to a broad spectrum of motile bacterial pathogens. TLRs induce intracellular signaling via dimerization of their TIR domains followed by adapter recruitment through multiple interactions of receptor and adapter TIRs. Here, a library of cell-permeable decoy peptides derived from the TLR5 TIR was screened for TLR5 signaling inhibition in the HEK-Blue-mTLR5 reporter cell line. The peptide demonstrating the strongest inhibition, 5R667, corresponded to the second helix of the region between the third and fourth ß-strands (helix Câ³). In addition to the TLR5-induced cytokine expression, 5R667 inhibited cytokine expression elicited by TLR4, TLR2, and TLR9. 5R667 also suppressed the systemic cytokine induction elicited by LPS administration in mice. 5R667 binding specificity was studied by time-resolved fluorescence spectroscopy in a cell-based assay. 5R667 demonstrated a multispecific binding pattern with respect to TIR domains: It bound TIRs of TLR adapters of the MyD88-dependent pathway, Toll/interleukin-1 receptor domain-containing adapter protein/MyD88 adapter-like (TIRAP) and MyD88, and also the TIR of TLR5. TR667, the peptide derived from the TIRAP region, which is structurally homologous to 5R667, demonstrated binding and inhibitory properties similar to that of 5R667. The surface-exposed residues within TIR regions represented by 5R667 and TR667 form motifs, which are nearly 90% conserved in vertebrate evolution and are distinctive of TLR5 and TIRAP TIR domains. Thus, we have identified an evolutionary conserved adapter recruitment motif within TLR5 TIR, the function of which can be inhibited by selective cell-permeable decoy peptides, which can serve as pan-specific TLR inhibitors.
Asunto(s)
Factor 88 de Diferenciación Mieloide , Receptor Toll-Like 5 , Animales , Ratones , Factor 88 de Diferenciación Mieloide/metabolismo , Transducción de Señal , Péptidos/metabolismo , Citocinas/metabolismo , Receptores de Interleucina-1/metabolismoRESUMEN
Interstitial cystitis (IC) is a chronic syndrome that affects the urinary bladder. The etiology of this disease is unclear, and no effective therapies are available at this time. Although inflammation is suspected, no clear evidence for a role of conventional mediators of inflammation, such as cytokines and their downstream molecules, has been obtained to date. Our previous studies indicated that primary cell cultures derived from IC urothelium abnormally express molecules associated with cell adhesion. Here we describe a mechanism by which transcriptional changes in tight junction and adhesion molecules are mediated. Oncosuppressor proteins p53 and cyclin-dependent protein kinase inhibitor p21 directly associate with regulatory sites on the ZO-1 and E-cadherin genes, identifying important roles for p53 and p21 in driving non-oncogenic pathologies. These data also suggest that interference with these factors offers a potential therapeutic opportunity.
Asunto(s)
Inhibidor p21 de las Quinasas Dependientes de la Ciclina/metabolismo , Cistitis Intersticial/metabolismo , Expresión Génica/fisiología , Proteína p53 Supresora de Tumor/metabolismo , Cadherinas/metabolismo , Adhesión Celular/fisiología , Moléculas de Adhesión Celular/metabolismo , Moléculas de Adhesión Celular/fisiología , Línea Celular , Citocinas/metabolismo , Humanos , Inflamación/metabolismo , Uniones Estrechas/metabolismo , Uniones Estrechas/fisiología , Transcripción Genética/fisiología , Vejiga Urinaria/metabolismo , Vejiga Urinaria/fisiología , Urotelio/metabolismo , Proteína de la Zonula Occludens-1/metabolismoRESUMEN
p16INK4A and p53 are two important tumor suppressor proteins that play essential roles during cell proliferation and aging through regulating the expression of several genes. Here, we report that p16INK4A and p53 co-regulate a plethora of transcripts. Furthermore, both proteins colocalize in the nucleus of human primary skin fibroblasts and breast luminal cells, and form a heteromer whose level increases in response to genotoxic stress as well as aging of human fibroblasts and various mouse organs. CDK4 is also present in this heteromeric complex, which is formed only in the presence of DNA both in vitro using pure recombinant proteins and in vivo. We have also shown that p16INK4A enhances the binding efficiency of p53 to its cognate sequence presents in the CDKN1A promoter in vitro, and both proteins are present at the promoters of CDKN1A and BAX in vivo. Importantly, the fourth ankyrin repeat of p16INK4A and the C-terminal domain of p53 were necessary for the physical association between these two proteins. The physiologic importance of this association was revealed by the inability of cancer-associated p16INK4A mutants to interact with p53 and to transactivate the expression of its major targets CDKN1A and BAX in the p16-defective U2OS cells expressing either wild-type or mutated p16INK4A . Furthermore, the association between p16INK4A and p53 was capital for their nuclear colocalization, the X-ray-dependent induction of p21 and Bax proteins as well as the induction of apoptosis in various types of cells. Together, these results show DNA-dependent physical interaction between p16INK4A and p53.
Asunto(s)
Apoptosis , Inhibidor p16 de la Quinasa Dependiente de Ciclina/metabolismo , ADN/metabolismo , Regulación de la Expresión Génica , Proteína p53 Supresora de Tumor/metabolismo , Animales , Proliferación Celular , Células Cultivadas , Inhibidor p16 de la Quinasa Dependiente de Ciclina/genética , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/metabolismo , ADN/genética , Embrión de Mamíferos/citología , Embrión de Mamíferos/metabolismo , Femenino , Fibroblastos/citología , Fibroblastos/metabolismo , Humanos , Ratones , Ratones Endogámicos C57BL , Regiones Promotoras Genéticas , Transcripción Genética , Proteína p53 Supresora de Tumor/genética , Proteína X Asociada a bcl-2/metabolismoRESUMEN
Bacteria act as pro- or anti- tumorigenic agents. Whole bacteria or cytotoxic or immunogenic peptides carried by them exert potent anti-tumor effects in the experimental models of cancer. The use of attenuated microorganism(s) e.g., BCG to treat human urinary bladder cancer was found to be superior compared to standard chemotherapy. Although the phase-I clinical trials with Salmonella enterica serovar Typhimurium, has shown limited benefits in human subjects, a recent pre-clinical trial in pet dogs with tumors reported some subjects benefited from this treatment strain. In addition to the attenuated host strains derived by conventional mutagenesis, recombinant DNA technology has been applied to a few microorganisms that have been evaluated in the context of tumor colonization and eradication using mouse models. There is an enormous surge in publications describing bacterial anti-cancer therapies in the past 15years. Vectors for delivering shRNAs that target oncogenic products, express tumor suppressor genes and immunogenic proteins have been developed. These approaches have showed promising anti-tumor activity in mouse models against various tumors. These can be potential therapeutics for humans in the future. In this review, some conceptual and practical issues on how to improve these agents for human applications are discussed.
Asunto(s)
Microorganismos Modificados Genéticamente/genética , Neoplasias/terapia , Salmonella typhimurium/genética , Animales , Perros , Humanos , Microorganismos Modificados Genéticamente/metabolismo , Neoplasias/genética , Neoplasias/metabolismo , Salmonella typhimurium/metabolismoRESUMEN
Gene-associated with retinoid-interferon induced mortality-19 (GRIM-19), a STAT3-inhibitory protein, was isolated as a growth-suppressive gene product using a genome-wide expression knockdown screen. We and others have shown a loss of expression and occurrence of mutations in the GRIM-19 gene in a variety of primary human cancers, indicating its potential role as tumor suppressor. To help investigate its role in tumor development in vivo, we generated a genetically modified mouse in which Grim-19 can be conditionally inactivated. Deletion of Grim-19 in the skin significantly increased the susceptibility of mice to chemical carcinogenesis, resulting in development of squamous cell carcinomas. These tumors had high Stat3 activity and an increased expression of Stat3-responsive genes. Loss of Grim-19 also caused mitochondrial electron transport dysfunction resulting from failure to assemble electron transport chain complexes and altered the expression of several cellular genes involved in glycolysis. Surprisingly, the deletion of a single copy of the Grim-19 gene was sufficient to promote carcinogenesis and formation of invasive squamous cell carcinomas. These observations highlight the critical role of GRIM-19 as a tumor suppressor.
Asunto(s)
Carcinogénesis/genética , Carcinoma de Células Escamosas/genética , NADH NADPH Oxidorreductasas/genética , Animales , Cartilla de ADN/genética , Componentes del Gen , Perfilación de la Expresión Génica , Técnicas de Silenciamiento del Gen , Vectores Genéticos/genética , Inmunohistoquímica , Ratones , Ratones Noqueados , NADH NADPH Oxidorreductasas/metabolismo , Reacción en Cadena en Tiempo Real de la Polimerasa , Factor de Transcripción STAT3/metabolismo , Análisis de Secuencia de ARNRESUMEN
p16(INK4a) is a tumor suppressor protein involved in several stress-related cellular responses, including apoptosis. Recent lines of evidence indicate that p16(INK4a) is also a modulator of gene expression. However, the molecular mechanisms underlying this novel function are still obscure. Here, we present clear evidence that p16(INK4a) modulates the levels of various microRNAs, with marked positive effect on miR-141 and miR-146b-5p. This effect is mediated through the formation of the p16-CDK4-Sp1 heterocomplex, which binds to Sp1 consensus-binding motifs present in the promoters of miR-141 and miR-146b-5p, and it enables their transcription. In addition, we have shown that p16(INK4a) interacts with Sp1 through the fourth ankyrin repeat, which is crucial for Sp1 binding to the miR-141 and miR-146b-5p promoters and their transcriptional activation. The physiological importance of this association was revealed by the inability of cancer-related p16(INK4a) mutants to interact with Sp1. Moreover, we have shown p16-CDK4-Sp1-dependent up-regulation of miR-141 and miR-146b-5p following UV light-induced DNA damage and the role of these two microRNAs in mediating p16-related induction of apoptosis in response to this genotoxic stress. Together, these results indicate that p16(INK4a) associates with CDK4 not only to inhibit the cell cycle but also to enable the transcription of two important onco-microRNAs, which act as downstream effectors.
Asunto(s)
Quinasa 4 Dependiente de la Ciclina/metabolismo , Inhibidor p16 de la Quinasa Dependiente de Ciclina/metabolismo , MicroARNs/genética , MicroARNs/metabolismo , Factor de Transcripción Sp1/metabolismo , Secuencia de Bases , Ciclo Celular , Línea Celular , Quinasa 4 Dependiente de la Ciclina/química , Inhibidor p16 de la Quinasa Dependiente de Ciclina/química , Daño del ADN , Humanos , Datos de Secuencia Molecular , Complejos Multiproteicos/química , Complejos Multiproteicos/metabolismo , Regiones Promotoras Genéticas , Unión Proteica , Estabilidad del ARN , Factor de Transcripción Sp1/química , Activación Transcripcional/efectos de la radiación , Rayos Ultravioleta/efectos adversosRESUMEN
The signal transducer and activator of transcription 3 (STAT3) protein is critical for multiple cytokine and growth factor-induced biological responses in vivo. Its transcriptional activity is controlled by a transient phosphorylation of a critical tyrosine. Constitutive activation of STAT3 imparts resistance to apoptosis, promotes cell proliferation, and induces de novo micro-angiogenesis, three of the six cardinal hallmarks of a typical cancer cell. Earlier we reported the isolation of GRIM-19 as a growth suppressor using a genome-wide expression knockdown strategy. GRIM-19 binds to STAT3 and suppresses its transcriptional activity. To understand the pathological relevance of GRIM-19, we screened a set of primary head and neck tumors and identified three somatic mutations in GRIM-19. Wild-type GRIM-19 suppressed cellular transformation by a constitutively active form of STAT3, whereas tumor-derived mutants L71P, L91P and A95T significantly lost their ability to associate with STAT3, block gene expression, and suppress cellular transformation and tumor growth in vivo. Additionally, these mutants lost their capacity to prevent metastasis. These mutations define a mechanism by which STAT3 activity is deregulated in certain human head and neck tumors.
Asunto(s)
Proteínas Reguladoras de la Apoptosis/metabolismo , Complejo I de Transporte de Electrón/metabolismo , Regulación Neoplásica de la Expresión Génica , Chaperonas Moleculares/metabolismo , Mutación , NADH NADPH Oxidorreductasas/metabolismo , Factor de Transcripción STAT3/metabolismo , Animales , Carcinoma de Células Escamosas/metabolismo , Línea Celular Tumoral , Proliferación Celular , Perfilación de la Expresión Génica , Regulación de la Expresión Génica , Humanos , Ratones , Ratones Desnudos , Neoplasias de la Boca/metabolismo , Metástasis de la Neoplasia , Ratas , Transcripción GenéticaRESUMEN
Using a genome-wide technical knockout, we isolated a newly identified set of GRIM (genes associated with retinoid-interferon-induced mortality) genes; GRIM genes mediate IFN- and retinoic-acid (RA)-induced cell death. Here, we describe the isolation and characterization of one such gene, GRIM-1. Three proteins, with identical C-termini, were produced from the GRIM-1 open reading frame when this gene was transcribed and translated in vitro. These protein isoforms, designated GRIM-1alpha, GRIM-1beta and GRIM-1gamma, differentially suppressed growth via apoptosis in various cell lines. We also show that a caspase-dependent mechanism generates the proapoptotic GRIM-1 isoforms. Lastly, GRIM-1 isoforms differentially blocked maturation of 18S ribosomal RNA, consistent with their respective growth-suppressive ability. Together, these studies identified a novel protein involved in growth suppression and cell death.
Asunto(s)
Proteínas Reguladoras de la Apoptosis/genética , Muerte Celular/efectos de los fármacos , Muerte Celular/genética , Interferón beta/farmacología , Tretinoina/farmacología , Animales , Apoptosis/efectos de los fármacos , Apoptosis/genética , Proteínas Reguladoras de la Apoptosis/biosíntesis , Caspasa 9/metabolismo , Procesos de Crecimiento Celular/genética , Regulación de la Expresión Génica , Técnicas de Inactivación de Genes , Células HeLa , Humanos , Ratones , Ratones Desnudos , Isoformas de Proteínas , Proteínas/genética , ARN Ribosómico/genética , ARN Ribosómico/metabolismoRESUMEN
GRIM-19 (Gene associated with Retinoid-IFN-induced Mortality-19) was originally isolated as a growth suppressor in a genome-wide knockdown screen with antisense libraries. Like classical tumor suppressors, mutations, and/or loss of GRIM-19 expression occur in primary human tumors; and it is inactivated by viral gene products. Our search for potential GRIM-19-binding proteins, using mass spectrometry, that permit its antitumor actions led to the inhibitor of cyclin-dependent kinase 4, CDKN2A. The GRIM-19/CDKN2A synergistically suppressed cell cycle progression via inhibiting E2F1-driven gene expression. The N terminus of GRIM-19 and the fourth ankyrin repeat of CDKN2A are crucial for their interaction. The biological relevance of these interactions is underscored by observations that GRIM-19 promotes the inhibitory effect of CDKN2A on CDK4; and mutations from primary tumors disrupt its ability to interact with GRIM-19 and suppress E2F1-driven gene expression.
Asunto(s)
Proteínas Reguladoras de la Apoptosis/metabolismo , Ciclo Celular , Inhibidor p16 de la Quinasa Dependiente de Ciclina/metabolismo , Factor de Transcripción E2F1/metabolismo , Regulación Neoplásica de la Expresión Génica , NADH NADPH Oxidorreductasas/metabolismo , Secuencia de Aminoácidos , Animales , Repetición de Anquirina , Proteínas Reguladoras de la Apoptosis/química , Proteínas Reguladoras de la Apoptosis/deficiencia , Proteínas Reguladoras de la Apoptosis/genética , Línea Celular Tumoral , Ciclina D1/metabolismo , Quinasa 4 Dependiente de la Ciclina/metabolismo , Inhibidor p16 de la Quinasa Dependiente de Ciclina/química , Inhibidor p16 de la Quinasa Dependiente de Ciclina/genética , Fase G1 , Técnicas de Silenciamiento del Gen , Humanos , Ratones , Datos de Secuencia Molecular , Mutación , NADH NADPH Oxidorreductasas/química , NADH NADPH Oxidorreductasas/deficiencia , NADH NADPH Oxidorreductasas/genética , Neoplasias/genética , Neoplasias/metabolismo , Neoplasias/patología , Estructura Terciaria de ProteínaRESUMEN
We have previously isolated GRIM-19, a novel growth suppressor, using a genetic method. GRIM-19 ablates cell growth by inhibiting the transcription factor signal transducer and activator of transcription 3 (STAT3). Up-regulation of STAT3 and growth promotion were observed in a number of human tumors. Although the tumor-suppressive actions of GRIM-19 are known, the structural elements required for its antitumor actions are not understood. Mutational and protein sequence analyses identified a motif in the N terminus of GRIM-19 that exhibited similarity to certain RNA viral proteins. We show that disruption of specific amino acids within this motif cripples the antitumor actions of GRIM-19. These mutants fail to interact with STAT3 efficiently and consequently do not inhibit growth-promoting gene expression. More importantly, we show that a clinically observed mutation in the N terminus of GRIM-19 also weakened its interaction with STAT3 and antitumor action. Together, these studies identify a major role for the N terminus of GRIM-19 in mediating its tumor-suppressive actions.
Asunto(s)
Proteínas Reguladoras de la Apoptosis/química , Proteínas Reguladoras de la Apoptosis/metabolismo , NADH NADPH Oxidorreductasas/química , NADH NADPH Oxidorreductasas/metabolismo , Proteínas Supresoras de Tumor/química , Proteínas Supresoras de Tumor/metabolismo , Secuencias de Aminoácidos/genética , Animales , Apoptosis , Proteínas Reguladoras de la Apoptosis/genética , Análisis Mutacional de ADN , Regulación Neoplásica de la Expresión Génica , Humanos , Ratones , Ratones Desnudos , NADH NADPH Oxidorreductasas/genética , Trasplante de Neoplasias , Neoplasias/metabolismo , Neoplasias/patología , Factor de Transcripción STAT3/antagonistas & inhibidores , Factor de Transcripción STAT3/genética , Factor de Transcripción STAT3/metabolismo , Proteínas Supresoras de Tumor/genéticaRESUMEN
Cytokines belonging to the IFN family are potent growth suppressors. In a number of clinical and preclinical studies, vitamin A and its derivatives like retinoic acid (RA) have been shown to exert synergistic growth-suppressive effects on several tumor cells. We have employed a genome-wide expression-knockout approach to identify the genes critical for IFN/RA-induced growth suppression. A number of novel genes associated with Retinoid-Interferon-induced Mortality (GRIM) were isolated. In this review, we will describe the molecular mechanisms of actions of one, GRIM-19, which participates in multiple pathways for exerting growth control and/or cell death. This protein is emerging as a new tumor suppressor. In addition, GRIM-19 appears to participate in innate immune responses as its activity is modulated by several viruses and bacteria. Thus, GRIMs seem to couple with multiple biological responses by acting at critical nodes.
Asunto(s)
Proteínas Reguladoras de la Apoptosis/genética , Proteínas Reguladoras de la Apoptosis/metabolismo , NADH NADPH Oxidorreductasas/genética , NADH NADPH Oxidorreductasas/metabolismo , Proteínas Supresoras de Tumor/genética , Proteínas Supresoras de Tumor/metabolismo , Animales , Antineoplásicos/farmacología , Técnicas de Silenciamiento del Gen , Estudio de Asociación del Genoma Completo , Humanos , Interferones/farmacología , Tretinoina/farmacologíaRESUMEN
Signal transducers and activators of transcription 3 (STAT3) was originally identified as a transcription factor that mediates cytokine-induced responses. In these pathways, Janus-activated kinase (JAK)-induced transient tyrosine phosphorylation of STAT3 promotes gene expression in response to a number of cytokines, which is inhibited by feedback mechanisms. A number of studies have shown that STAT3 is constitutively activated in human cancer cells, leading to cell proliferation. It is unclear, apart from a chronic tyrosyl phosphorylation of STAT3, what mechanisms contribute to the STAT3 deregulation in tumors. Earlier, we have isolated a novel growth inhibitory gene product, gene associated with retinoid-IFN-induced mortality 19 (GRIM-19), using a genetic approach. GRIM-19 is an IFN/retinoic acid-regulated growth suppressor. Subsequent analyses have shown that GRIM-19 binds to STAT3 and prevents interleukin-6-induced transcription of cellular genes. However, its effects on a constitutively active STAT3 and cellular transformation are unknown. In this study, we show that GRIM-19 suppresses constitutive STAT3-induced cellular transformation in vitro and in vivo by down-regulating the expression of a number of cellular genes involved in cell proliferation and apoptosis.
Asunto(s)
Proteínas Reguladoras de la Apoptosis/genética , Proteínas Reguladoras de la Apoptosis/fisiología , Regulación Neoplásica de la Expresión Génica , NADH NADPH Oxidorreductasas/genética , NADH NADPH Oxidorreductasas/fisiología , Factor de Transcripción STAT3/metabolismo , Animales , Apoptosis , Muerte Celular , Proliferación Celular , Transformación Celular Neoplásica , Humanos , Interleucina-6/metabolismo , Ratones , Fosforilación , Ratas , Transcripción Genética , Tretinoina/metabolismoRESUMEN
Cytokines induce cell proliferation or growth suppression depending on the context. It is increasingly becoming clear that success of standard radiotherapy and/or chemotherapeutics to eradicate solid tumors is dependent on IFN signaling. In this review we discuss the molecular mechanisms of tumor growth suppression by a gene product isolated in our laboratory using a genome-wide expression knock-down strategy. Gene associated with retinoid-IFN-induced mortality -19 (GRIM-19) functions as non-canonical tumor suppressor by antagonizing oncoproteins. As a component of mitochondrial respiratory chain, GRIM-19 influences the degree of "Warburg effect" in cancer cells as many advanced and/or aggressive tumors show severely down-regulated GRIM-19 levels. In addition, GRIM-19 appears to regulate innate and acquired immune responses in mouse models. Thus, GRIM-19 is positioned at nodes that favor cell protection and/or prevent aberrant cell growth.
Asunto(s)
Proteínas Reguladoras de la Apoptosis/genética , Proteínas Reguladoras de la Apoptosis/metabolismo , Citocinas/fisiología , Regulación Neoplásica de la Expresión Génica , NADH NADPH Oxidorreductasas/genética , NADH NADPH Oxidorreductasas/metabolismo , Neoplasias/metabolismo , Neoplasias/patología , Animales , Proliferación Celular , Citocinas/genética , Regulación hacia Abajo , Metabolismo Energético , Técnicas de Silenciamiento del Gen , Glucosa/metabolismo , Ratones , Mitocondrias/metabolismo , Neoplasias/genética , Factor de Transcripción STAT3/metabolismo , Transducción de SeñalRESUMEN
The interferon (IFN) family of cytokines participates in the development of innate and acquired immune defenses against various pathogens and pathogenic stimuli. Discovered originally as a proteinaceous substance secreted from virus-infected cells that afforded immunity to neighboring cells from virus infection, these cytokines are now implicated in various human pathologies, including control of tumor development, cell differentiation, and autoimmunity. It is now believed that the IFN system (IFN genes and the genes induced by them, and the factors that regulate these processes) is a generalized alarm of cellular stress, including DNA damage. IFNs exert both beneficial and deleterious effects on the central nervous system (CNS). Our knowledge of the IFN-regulated processes in the CNS is far from being clear. In this article, we reviewed the current understanding of IFN signal transduction pathways and gene products that might have potential relevance to diseases of the CNS.
Asunto(s)
Enfermedades Autoinmunes/inmunología , Enfermedades del Sistema Nervioso Central/inmunología , Sistema Nervioso Central/inmunología , Interferones/metabolismo , Neoplasias/inmunología , Animales , Daño del ADN , Humanos , Interferones/inmunología , Transducción de Señal/inmunologíaRESUMEN
The death-associated protein kinase 1 (DAPK1) is an important regulator of cell death and autophagy. Recently, we have identified that ATF6, an endoplasmic reticulum-resident transcription factor, in association with the transcription factor CEBP-ß, regulates the gamma interferon (IFN-γ)-induced expression of Dapk1 (P. Gade et al., Proc. Natl. Acad. Sci. U. S. A. 109:10316-10321, 2012, doi.org/10.1073/pnas.1119273109). IFN-γ-induced proteolytic processing of ATF6 and phosphorylation of C/EBP-ß were essential for the formation of a novel transcriptional complex that regulates DAPK1. Here, we report that IFN-γ activates the ASK1-MKK3/MKK6-p38 mitogen-activated protein kinase (MAPK) pathway for controlling the activity of ATF6. The terminal enzyme in this pathway, p38 MAPK, phosphorylates a critical threonine residue in ATF6 upstream of its DNA binding domain. ATF6 mutants defective for p38 MAPK phosphorylation fail to undergo proteolytic processing in the Golgi apparatus and drive IFN-γ-induced gene expression and autophagy. We also show that mice lacking Ask1 are highly susceptible to lethal bacterial infection owing to defective autophagy. Together, these results identify a novel host defense pathway controlled by IFN-γ signaling.
Asunto(s)
Factor de Transcripción Activador 6/metabolismo , Autofagia , Proteínas Quinasas Asociadas a Muerte Celular/metabolismo , Interferón gamma/metabolismo , MAP Quinasa Quinasa Quinasa 5/metabolismo , Sistema de Señalización de MAP Quinasas , Factor de Transcripción Activador 6/genética , Animales , Bacillus anthracis/patogenicidad , Sitios de Unión , Línea Celular , Proteínas Quinasas Asociadas a Muerte Celular/genética , Técnicas de Silenciamiento del Gen , Humanos , Hígado/inmunología , Hígado/microbiología , Ratones , Mutación , Fosforilación , Células Sf9 , Bazo/inmunología , Bazo/microbiologíaRESUMEN
The interferon (IFN) family of cytokines regulates many cellular processes, such as transcription, translation, post-translational modifications, and protein degradation. IFNs induce growth inhibition and/or cell death, depending on the cell type, by employing different proteins. This review describes a novel growth-suppressive pathway employed by IFNs that affects rRNA levels. Maturation of rRNA involves numerous noncoding small regulatory RNA-guided processes. These regulatory RNAs, called small nucleolar RNA (snoRNAs), function as a ribonucleoprotein particle (RNP) in the nucleolus. The biogenesis of snoRNPs is dependent on core protein and assembly factors. Our laboratory recently isolated a growth-suppressive protein gene associated with retinoid-IFN-induced mortality (GRIM)-1 using a genetic screen. IFN-inducible GRIM-1 (SHQ1) is an assembly factor that controls one arm of the snoRNP machinery. GRIM-1 inhibits sno/scaRNP formation to induce growth suppression via reduction in mature rRNA levels. Loss of GRIM-1 observed in certain cancers implicates it to be a novel tumor suppressor. Certain snoRNAs have been reported to act as either oncogenes or tumor suppressors in vitro. Recent studies have shown that certain sno/scaRNAs are further processed into micro RNA-like molecules to control translation of protein-coding RNAs. We present a model as to how these small regulatory RNAs influence cell growth and a potential role for GRIM-1 in this process.
Asunto(s)
Interferones/metabolismo , Neoplasias/metabolismo , ARN Nucleolar Pequeño/genética , ARN Nucleolar Pequeño/metabolismo , Proteínas Reguladoras de la Apoptosis/genética , Proteínas Reguladoras de la Apoptosis/metabolismo , Proteínas Portadoras/metabolismo , Humanos , Interferones/genética , Péptidos y Proteínas de Señalización Intracelular , Neoplasias/genética , Región Organizadora del Nucléolo/genética , Región Organizadora del Nucléolo/metabolismo , ARN Ribosómico/biosíntesisRESUMEN
Although senescence in oncogenesis has been widely studied, little is known regarding the role of this process in chemotherapy resistance. Thus, from the standpoint of enhancing and improving cancer therapy, a better understanding of the molecular machinery involved in chemotherapy-related senescence is paramount. We show for the first time that Mcl-1, a Bcl-2 family member, plays an important role in preventing chemotherapy-induced senescence (CIS). Overexpression of Mcl-1 in p53⺠cell lines inhibits CIS. Conversely, downregulation of Mcl-1 makes cells sensitive to CIS. Surprisingly, downregulation of Mcl-1 in p53⻠cells restored CIS to similar levels as p53⺠cells. In all cases where senescence can be induced, we observed increased p21 expression. Moreover, we show that the domain of Mcl-1 responsible for its antisenescent effects is distinct from that known to confer its antiapoptotic qualities. In vivo we observe that downregulation of Mcl-1 can almost retard tumor growth regardless of p53 status, while overexpression of Mcl-1 in p53⺠cells conferred resistance to CIS and promoted tumor outgrowth. In summary, our data reveal that Mcl-1 can inhibit CIS in both a p53-dependent and -independent manner in vitro and in vivo and that this Mcl-1-mediated inhibition can enhance tumor growth in vivo.
Asunto(s)
Senescencia Celular/genética , Proteínas Proto-Oncogénicas c-bcl-2/genética , Animales , Línea Celular Tumoral , Resistencia a Antineoplásicos/genética , Regulación Neoplásica de la Expresión Génica , Genes p53 , Humanos , Ratones , Ratones Desnudos , Proteína 1 de la Secuencia de Leucemia de Células Mieloides , Trasplante de Neoplasias , Neoplasias/tratamiento farmacológico , Neoplasias/genética , Neoplasias/patologíaRESUMEN
We have recently isolated novel IFN-inducible gene, Gene associated with Retinoid-Interferon-induced Mortality-1 (GRIM-1), using a genetic technique. Moderate ectopic expression of GRIM-1 caused growth inhibition and sensitized cells to retinoic acid (RA)/IFN-induced cell death while high expression caused apoptosis. GRIM-1 depletion, using RNAi, conferred a growth advantage. Three protein isoforms (1α, 1ß and 1γ) with identical C-termini are produced from GRIM-1 mRNA. We show that GRIM-1 isoforms interact with NAF1 and DKC1, two essential proteins required for box H/ACA sno/sca RNP biogenesis and suppresses box H/ACA RNA levels in mammalian cells by delocalizing NAF1. Suppression of these small RNAs manifests as inefficient rRNA maturation and growth suppression. Interestingly, yeast Shq1p also caused growth suppression in mammalian cells. Consistent with its growth-suppressive property, GRIM-1 expression is lost in a number of human primary prostate tumors. Our observations support a recent study that GRIM-1 might act as a co-tumor suppressor in the prostate.