RESUMO
Mutations in isocitrate dehydrogenase 1 and 2 (IDH1/2) have been discovered in several cancer types and cause the neurometabolic syndrome D2-hydroxyglutaric aciduria (D2HGA). The mutant enzymes exhibit neomorphic activity resulting in production of D2-hydroxyglutaric acid (D-2HG). To study the pathophysiological consequences of the accumulation of D-2HG, we generated transgenic mice with conditionally activated IDH2(R140Q) and IDH2(R172K) alleles. Global induction of mutant IDH2 expression in adults resulted in dilated cardiomyopathy, white matter abnormalities throughout the central nervous system (CNS), and muscular dystrophy. Embryonic activation of mutant IDH2 resulted in more pronounced phenotypes, including runting, hydrocephalus, and shortened life span, recapitulating the abnormalities observed in D2HGA patients. The diseased hearts exhibited mitochondrial damage and glycogen accumulation with a concordant up-regulation of genes involved in glycogen biosynthesis. Notably, mild cardiac hypertrophy was also observed in nude mice implanted with IDH2(R140Q)-expressing xenografts, suggesting that 2HG may potentially act in a paracrine fashion. Finally, we show that silencing of IDH2(R140Q) in mice with an inducible transgene restores heart function by lowering 2HG levels. Together, these findings indicate that inhibitors of mutant IDH2 may be beneficial in the treatment of D2HGA and suggest that 2HG produced by IDH mutant tumors has the potential to provoke a paraneoplastic condition.
Assuntos
Cardiomiopatias/genética , Glutaratos/metabolismo , Isocitrato Desidrogenase/genética , Mutação , Doenças Neurodegenerativas/genética , Animais , Cardiomiopatias/enzimologia , Cardiomiopatias/patologia , Linhagem Celular , Perfilação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Coração/fisiopatologia , Humanos , Isocitrato Desidrogenase/metabolismo , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Doenças Neurodegenerativas/enzimologia , Doenças Neurodegenerativas/patologiaRESUMO
The identification of succinate dehydrogenase (SDH), fumarate hydratase (FH) and isocitrate dehydrogenase (IDH) mutations in human cancers has rekindled the idea that altered cellular metabolism can transform cells. Inactivating SDH and FH mutations cause the accumulation of succinate and fumarate, respectively, which can inhibit 2-oxoglutarate (2-OG)-dependent enzymes, including the EGLN prolyl 4-hydroxylases that mark the hypoxia inducible factor (HIF) transcription factor for polyubiquitylation and proteasomal degradation. Inappropriate HIF activation is suspected of contributing to the pathogenesis of SDH-defective and FH-defective tumours but can suppress tumour growth in some other contexts. IDH1 and IDH2, which catalyse the interconversion of isocitrate and 2-OG, are frequently mutated in human brain tumours and leukaemias. The resulting mutants have the neomorphic ability to convert 2-OG to the (R)-enantiomer of 2-hydroxyglutarate ((R)-2HG). Here we show that (R)-2HG, but not (S)-2HG, stimulates EGLN activity, leading to diminished HIF levels, which enhances the proliferation and soft agar growth of human astrocytes. These findings define an enantiomer-specific mechanism by which the (R)-2HG that accumulates in IDH mutant brain tumours promotes transformation and provide a justification for exploring EGLN inhibition as a potential treatment strategy.
Assuntos
Transformação Celular Neoplásica/efeitos dos fármacos , Transformação Celular Neoplásica/metabolismo , Dioxigenases/metabolismo , Glutaratos/química , Glutaratos/farmacologia , Proteínas Nucleares/metabolismo , Pró-Colágeno-Prolina Dioxigenase/metabolismo , Astrócitos/citologia , Astrócitos/efeitos dos fármacos , Astrócitos/metabolismo , Linhagem Celular , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Transformação Celular Neoplásica/genética , Dioxigenases/genética , Ativação Enzimática/efeitos dos fármacos , Glioma/enzimologia , Glioma/genética , Glioma/metabolismo , Glioma/patologia , Glutaratos/metabolismo , Humanos , Fator 1 Induzível por Hipóxia/metabolismo , Prolina Dioxigenases do Fator Induzível por Hipóxia , Isocitrato Desidrogenase/genética , Isocitrato Desidrogenase/metabolismo , Proteínas Nucleares/genética , Oncogenes , Pró-Colágeno-Prolina Dioxigenase/genéticaRESUMO
The pim family of proto-oncogenes encodes three serine-threonine kinases that have been implicated in the development of malignancies in mice and in humans. Expression of the Pim protein kinases is tightly regulated at the transcriptional, post-transcriptional, and translational levels. Dysregulation of pim transcription and pim mRNA stability have been implicated in Pim-mediated transformation. The data presented herein demonstrate that expression of the Pim kinases is additionally regulated at the post-translational level, by the serine-threonine phosphatase protein phosphatase 2A (PP2A). The catalytic subunit of PP2A associates with the Pim kinases in vivo, and the Pim kinases are substrates of PP2A phosphatase activity in vitro. Furthermore, overexpression of PP2A reduces the levels of the Pim proteins, whereas inhibition of PP2A activity by the protein phosphatase inhibitor okadaic acid stabilizes the Pim proteins. Finally, the effects of PP2A on the expression of the Pim proteins can affect Pim function. Taken together, these data suggest that PP2A activity is important for the regulation of the stability and function of the Pim kinases.
Assuntos
Fosfoproteínas Fosfatases/metabolismo , Proteínas Proto-Oncogênicas/metabolismo , Domínio Catalítico/fisiologia , Linhagem Celular , Estabilidade Enzimática , Humanos , Proteína Fosfatase 2 , Processamento de Proteína Pós-Traducional , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Proto-Oncogênicas c-pim-1RESUMO
Studies of SOCS-1-deficient mice have implicated Socs-1 in the suppression of JAK-STAT (Janus tyrosine kinase-signal transducers and activators of transcription) signaling and T cell development. It has been suggested that the levels of Socs-1 protein may be regulated through the proteasome pathway. Here we show that Socs-1 interacts with members of the Pim family of serine/threonine kinases in thymocytes. Coexpression of the Pim kinases with Socs-1 results in phosphorylation and stabilization of the Socs-1 protein. The protein levels of Socs-1 are significantly reduced in the Pim-1(-/-), Pim-2(-/-) mice as compared with wild-type mice. Similar to Socs-1(-/-) mice, thymocytes from Pim-1(-/-), Pim-2(-/-) mice showed prolonged Stat6 phosphorylation upon IL-4 stimulation. These data suggest that the Pim kinases may regulate cytokine-induced JAK-STAT signaling through modulation of Socs-1 protein levels.