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
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
Osteoporosis affects over 20 million patients in the United States. Among those, disuse osteoporosis is serious as it is induced by bed-ridden conditions in patients suffering from aging-associated diseases including cardiovascular, neurological, and malignant neoplastic diseases. Although the phenomenon that loss of mechanical stress such as bed-ridden condition reduces bone mass is clear, molecular bases for the disuse osteoporosis are still incompletely understood. In disuse osteoporosis model, bone loss is interfered by inhibitors of sympathetic tone and adrenergic receptors that suppress bone formation. However, how beta adrenergic stimulation affects osteoblastic migration and associated proliferation is not known. Here we introduced a live imaging system, fluorescent ubiquitination-based cell cycle indicator (FUCCI), in osteoblast biology and examined isoproterenol regulation of cell cycle transition and cell migration in osteoblasts. Isoproterenol treatment suppresses the levels of first entry peak of quiescent osteoblastic cells into cell cycle phase by shifting from G1 /G0 to S/G2 /M and also suppresses the levels of second major peak population that enters into S/G2 /M. The isoproterenol regulation of osteoblastic cell cycle transition is associated with isoproterenol suppression on the velocity of migration. This isoproterenol regulation of migration velocity is cell cycle phase specific as it suppresses migration velocity of osteoblasts in G1 phase but not in G1 /S nor in G2 /M phase. Finally, these observations on isoproterenol regulation of osteoblastic migration and cell cycle transition are opposite to the PTH actions in osteoblasts. In summary, we discovered that sympathetic tone regulates osteoblastic migration in association with cell cycle transition by using FUCCI system.