RESUMO
Deregulation of mRNA translation engenders many human disorders, including obesity, neurodegenerative diseases, and cancer, and is associated with pathogen infections. The role of eIF4E-dependent translational control in macrophage inflammatory responses in vivo is largely unexplored. In this study, we investigated the involvement of the translation inhibitors eIF4E-binding proteins (4E-BPs) in the regulation of macrophage inflammatory responses in vitro and in vivo. We show that the lack of 4E-BPs exacerbates inflammatory polarization of bone marrow-derived macrophages and that 4E-BP-null adipose tissue macrophages display enhanced inflammatory gene expression following exposure to a high-fat diet (HFD). The exaggerated inflammatory response in HFD-fed 4E-BP-null mice coincides with significantly higher weight gain, higher Irf8 mRNA translation, and increased expression of IRF8 in adipose tissue compared with wild-type mice. Thus, 4E-BP-dependent translational control limits, in part, the proinflammatory response during HFD. These data underscore the activity of the 4E-BP-IRF8 axis as a paramount regulatory mechanism of proinflammatory responses in adipose tissue macrophages.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Tecido Adiposo/metabolismo , Inflamação/genética , Fatores Reguladores de Interferon/genética , Macrófagos/metabolismo , Biossíntese de Proteínas/genética , Animais , Medula Óssea/metabolismo , Dieta Hiperlipídica/métodos , Fator de Iniciação 4E em Eucariotos/genética , Expressão Gênica/genética , Inflamação/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos KnockoutRESUMO
Herpes Simplex Virus 1 (HSV1) is amongst the most clinically advanced oncolytic virus platforms. However, efficient and sustained viral replication within tumours is limiting. Rapamycin can stimulate HSV1 replication in cancer cells, but active-site dual mTORC1 and mTORC2 (mammalian target of rapamycin complex 1 and 2) inhibitors (asTORi) were shown to suppress the virus in normal cells. Surprisingly, using the infected cell protein 0 (ICP0)-deleted HSV1 (HSV1-dICP0), we found that asTORi markedly augment infection in cancer cells and a mouse mammary cancer xenograft. Mechanistically, asTORi repressed mRNA translation in normal cells, resulting in defective antiviral response but also inhibition of HSV1-dICP0 replication. asTORi also reduced antiviral response in cancer cells, however in contrast to normal cells, transformed cells and cells transduced to elevate the expression of eukaryotic initiation factor 4E (eIF4E) or to silence the repressors eIF4E binding proteins (4E-BPs), selectively maintained HSV1-dICP0 protein synthesis during asTORi treatment, ultimately supporting increased viral replication. Our data show that altered eIF4E/4E-BPs expression can act to promote HSV1-dICP0 infection under prolonged mTOR inhibition. Thus, pharmacoviral combination of asTORi and HSV1 can target cancer cells displaying dysregulated eIF4E/4E-BPs axis.
Assuntos
Herpes Simples/patologia , Herpesvirus Humano 1/efeitos dos fármacos , Herpesvirus Humano 1/genética , Proteínas Imediatamente Precoces/genética , Neoplasias/virologia , Inibidores de Proteínas Quinases/farmacologia , Serina-Treonina Quinases TOR/antagonistas & inibidores , Ubiquitina-Proteína Ligases/genética , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Domínio Catalítico/efeitos dos fármacos , Proteínas de Ciclo Celular , Células Cultivadas , Chlorocebus aethiops , Fator de Iniciação 4E em Eucariotos/genética , Fator de Iniciação 4E em Eucariotos/metabolismo , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Células HEK293 , Herpes Simples/complicações , Herpes Simples/genética , Humanos , Proteínas Imediatamente Precoces/deficiência , Camundongos , Neoplasias/complicações , Neoplasias/genética , Neoplasias/patologia , Organismos Geneticamente Modificados , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Transdução de Sinais/genética , Serina-Treonina Quinases TOR/química , Ubiquitina-Proteína Ligases/deficiência , Células VeroRESUMO
The mechanisms that link environmental and intracellular stimuli to mitochondrial functions, including fission/fusion, ATP production, metabolite biogenesis, and apoptosis, are not well understood. Here, we demonstrate that the nutrient-sensing mechanistic/mammalian target of rapamycin complex 1 (mTORC1) stimulates translation of mitochondrial fission process 1 (MTFP1) to control mitochondrial fission and apoptosis. Expression of MTFP1 is coupled to pro-fission phosphorylation and mitochondrial recruitment of the fission GTPase dynamin-related protein 1 (DRP1). Potent active-site mTOR inhibitors engender mitochondrial hyperfusion due to the diminished translation of MTFP1, which is mediated by translation initiation factor 4E (eIF4E)-binding proteins (4E-BPs). Uncoupling MTFP1 levels from the mTORC1/4E-BP pathway upon mTOR inhibition blocks the hyperfusion response and leads to apoptosis by converting mTOR inhibitor action from cytostatic to cytotoxic. These data provide direct evidence for cell survival upon mTOR inhibition through mitochondrial hyperfusion employing MTFP1 as a critical effector of mTORC1 to govern cell fate decisions.
Assuntos
Proteínas de Membrana/metabolismo , Mitocôndrias/enzimologia , Dinâmica Mitocondrial , Serina-Treonina Quinases TOR/metabolismo , Proteínas Adaptadoras de Transdução de Sinal , Apoptose , Sistemas CRISPR-Cas , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Proteínas de Ciclo Celular , Linhagem Celular Tumoral , Sobrevivência Celular , Dinaminas/genética , Dinaminas/metabolismo , Fatores de Iniciação em Eucariotos/genética , Fatores de Iniciação em Eucariotos/metabolismo , Humanos , Alvo Mecanístico do Complexo 1 de Rapamicina , Proteínas de Membrana/genética , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/ultraestrutura , Dinâmica Mitocondrial/efeitos dos fármacos , Complexos Multiproteicos/genética , Complexos Multiproteicos/metabolismo , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Fosforilação , Inibidores de Proteínas Quinases/farmacologia , Interferência de RNA , Transdução de Sinais , Serina-Treonina Quinases TOR/antagonistas & inibidores , Serina-Treonina Quinases TOR/genética , TransfecçãoRESUMO
Translational control of gene expression plays a key role during the early phases of embryonic development. Here we describe a transcriptional regulator of mouse embryonic stem cells (mESCs), Yin-yang 2 (YY2), that is controlled by the translation inhibitors, Eukaryotic initiation factor 4E-binding proteins (4E-BPs). YY2 plays a critical role in regulating mESC functions through control of key pluripotency factors, including Octamer-binding protein 4 (Oct4) and Estrogen-related receptor-ß (Esrrb). Importantly, overexpression of YY2 directs the differentiation of mESCs into cardiovascular lineages. We show that the splicing regulator Polypyrimidine tract-binding protein 1 (PTBP1) promotes the retention of an intron in the 5'-UTR of Yy2 mRNA that confers sensitivity to 4E-BP-mediated translational suppression. Thus, we conclude that YY2 is a major regulator of mESC self-renewal and lineage commitment and document a multilayer regulatory mechanism that controls its expression.