RESUMO
The adenosine monophosphate (AMP)-activated protein kinase (Ampk) is a central regulator of metabolic pathways, and increasing Ampk activity has been considered to be an attractive therapeutic target. Here, we have identified an orphan ubiquitin E3 ligase subunit protein, Fbxo48, that targets the active, phosphorylated Ampkα (pAmpkα) for polyubiquitylation and proteasomal degradation. We have generated a novel Fbxo48 inhibitory compound, BC1618, whose potency in stimulating Ampk-dependent signaling greatly exceeds 5-aminoimidazole-4-carboxamide-1-ß-ribofuranoside (AICAR) or metformin. This compound increases the biological activity of Ampk not by stimulating the activation of Ampk, but rather by preventing activated pAmpkα from Fbxo48-mediated degradation. We demonstrate that, consistent with augmenting Ampk activity, BC1618 promotes mitochondrial fission, facilitates autophagy and improves hepatic insulin sensitivity in high-fat-diet-induced obese mice. Hence, we provide a unique bioactive compound that inhibits pAmpkα disposal. Together, these results define a new pathway regulating Ampk biological activity and demonstrate the potential utility of modulating this pathway for therapeutic benefit.
Assuntos
Proteínas Quinases Ativadas por AMP/genética , Hipoglicemiantes/farmacologia , Obesidade/tratamento farmacológico , Complexo de Endopeptidases do Proteassoma/efeitos dos fármacos , Processamento de Proteína Pós-Traducional/efeitos dos fármacos , Ubiquitina-Proteína Ligases/genética , Proteínas Quinases Ativadas por AMP/metabolismo , Aminoimidazol Carboxamida/análogos & derivados , Aminoimidazol Carboxamida/farmacologia , Animais , Linhagem Celular Transformada , Dieta Hiperlipídica , Células Epiteliais/citologia , Células Epiteliais/efeitos dos fármacos , Células Epiteliais/metabolismo , Proteínas F-Box , Humanos , Hipoglicemiantes/síntese química , Resistência à Insulina , Metformina/farmacologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Obesos , Dinâmica Mitocondrial/efeitos dos fármacos , Obesidade/etiologia , Obesidade/genética , Obesidade/metabolismo , Fosforilação , Poliubiquitina/genética , Poliubiquitina/metabolismo , Complexo de Endopeptidases do Proteassoma/metabolismo , Estabilidade Proteica/efeitos dos fármacos , Proteólise/efeitos dos fármacos , Ribonucleotídeos/farmacologia , Ubiquitina-Proteína Ligases/antagonistas & inibidores , Ubiquitina-Proteína Ligases/metabolismo , UbiquitinaçãoRESUMO
Aging is a prominent risk factor for neurodegenerative disease. Defining gene expression mechanisms affecting healthy brain aging should lead to insight into genes that modulate susceptibility to disease. To define such mechanisms, we have pursued analysis of miR-34 mutants in Drosophila. The miR-34 mutant brain displays a gene expression profile of accelerated aging, and miR-34 upregulation is a potent suppressor of polyglutamine-induced neurodegeneration. We demonstrate that Pcl and Su(z)12, two components of polycomb repressive complex 2, (PRC2), are targets of miR-34, with implications for age-associated processes. Because PRC2 confers the repressive H3K27me3 mark, we hypothesize that miR-34 modulates PRC2 activity to relieve silencing of genes promoting healthful aging. Gene expression profiling of the brains of hypomorphic mutants in Enhancer of zeste (E(z)), the enzymatic methyltransferase component of PRC2, revealed a younger brain transcriptome profile and identified the small heat shock proteins as key genes reduced in expression with age.
Assuntos
Envelhecimento/metabolismo , Encéfalo/metabolismo , Drosophila melanogaster/genética , MicroRNAs/metabolismo , Chaperonas Moleculares/metabolismo , Complexo Repressor Polycomb 2/metabolismo , Regiões 3' não Traduzidas/genética , Animais , Sequência de Bases , Proteínas de Drosophila/metabolismo , Perfilação da Expressão Gênica , Histonas/metabolismo , Lisina/metabolismo , Metilação , MicroRNAs/genética , Modelos Biológicos , Mutação/genética , Degeneração Neural/metabolismo , Degeneração Neural/patologia , Peptídeos/toxicidade , Complexo Repressor Polycomb 2/genética , Agregados Proteicos , Transcriptoma/genéticaRESUMO
Gene silencing by double-stranded RNA is a widespread phenomenon called RNAi, involving homology-dependent degradation of mRNAs. Here we show that RNAi is established in the Drosophila female germ line. mRNA transcripts are translationally quiescent at the arrested oocyte stage and are insensitive to RNAi. Upon oocyte maturation, transcripts that are translated become sensitive to degradation while untranslated transcripts remain resistant. Mutations in aubergine and spindle-E, members of the PIWI/PAZ and DE-H helicase gene families, respectively, block RNAi activation during egg maturation and perturb translation control during oogenesis, supporting a connection between gene silencing and translation in the oocyte.