RESUMO
Mitochondrial and peroxisomal anchored protein ligase (MAPL) is a dual ubiquitin and small ubiquitin-like modifier (SUMO) ligase with roles in mitochondrial quality control, cell death and inflammation in cultured cells. Here, we show that MAPL function in the organismal context converges on metabolic control, as knockout mice are viable, insulin-sensitive, and protected from diet-induced obesity. MAPL loss leads to liver-specific activation of the integrated stress response, inducing secretion of stress hormone FGF21. MAPL knockout mice develop fully penetrant spontaneous hepatocellular carcinoma. Mechanistically, the peroxisomal bile acid transporter ABCD3 is a primary MAPL interacting partner and SUMOylated in a MAPL-dependent manner. MAPL knockout leads to increased bile acid production coupled with defective regulatory feedback in liver in vivo and in isolated primary hepatocytes, suggesting cell-autonomous function. Together, our findings establish MAPL function as a regulator of bile acid synthesis whose loss leads to the disruption of bile acid feedback mechanisms. The consequences of MAPL loss in liver, along with evidence of tumor suppression through regulation of cell survival pathways, ultimately lead to hepatocellular carcinogenesis.
Assuntos
Bile , Proteínas Mitocondriais , Ubiquitina-Proteína Ligases , Animais , Camundongos , Bile/metabolismo , Ácidos e Sais Biliares , Fígado/metabolismo , Camundongos Knockout , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismo , Ubiquitina-Proteína Ligases/genética , Ubiquitina-Proteína Ligases/metabolismo , UbiquitinasRESUMO
Peroxisomes play a central role in tuning metabolic and signaling programs in a tissue- and cell-type-specific manner. However, the mechanisms by which the status of peroxisomes is communicated and integrated into cellular signaling pathways are not yet understood. Herein, we report the cellular responses to peroxisomal proteotoxic stress upon silencing the peroxisomal protease/chaperone LONP2. Depletion of LONP2 triggered the accumulation of its substrate TYSND1 protease, while the overall expression of peroxisomal proteins, as well as TYSND1-dependent ACOX1 processing appeared normal, reflecting early stages of peroxisomal proteotoxic stress. Consequently, the alteration of peroxisome size and numbers, and luminal protein import failure was coupled with induction of cell-specific cellular stress responses. Specific to COS-7 cells was a strong activation of the integrated stress response (ISR) and upregulation of ribosomal biogenesis gene expression levels. Common changes between COS-7 and U2OS cell lines included repression of the retinoic acid signaling pathway and upregulation of sphingolipids. Cholesterol accumulated in the endomembrane compartments in both cell lines, consistent with evidence that peroxisomes are required for cholesterol flux out of late endosomes. These unexpected consequences of peroxisomal stress provide an important insight into our understanding of the tissue-specific responses seen in peroxisomal disorders.
Assuntos
Endossomos , Transdução de Sinais , Ribossomos , Peptídeo Hidrolases , Regulação para CimaRESUMO
Astrocytes, often considered as secondary responders to neurodegeneration, are emerging as primary drivers of brain disease. Here we show that mitochondrial DNA depletion in astrocytes affects their primary cilium, the signaling organelle of a cell. The progressive oxidative phosphorylation deficiency in astrocytes induces FOXJ1 and RFX transcription factors, known as master regulators of motile ciliogenesis. Consequently, a robust gene expression program involving motile cilia components and multiciliated cell differentiation factors are induced. While the affected astrocytes still retain a single cilium, these organelles elongate and become remarkably distorted. The data suggest that chronic activation of the mitochondrial integrated stress response (ISRmt) in astrocytes drives anabolic metabolism and promotes ciliary elongation. Collectively, our evidence indicates that an active signaling axis involving mitochondria and primary cilia exists and that ciliary signaling is part of ISRmt in astrocytes. We propose that metabolic ciliopathy is a novel pathomechanism for mitochondria-related neurodegenerative diseases.
Assuntos
Astrócitos , Cílios , Mitocôndrias , Astrócitos/metabolismo , Cílios/metabolismo , Cílios/patologia , Fatores de Transcrição Forkhead/genética , Fatores de Transcrição Forkhead/metabolismo , Homeostase , Mitocôndrias/metabolismo , Mitocôndrias/patologia , Camundongos , Animais , Fatores de Transcrição de Fator Regulador X/genética , Fatores de Transcrição de Fator Regulador X/metabolismo , DNA MitocondrialRESUMO
Mitochondrial DNA (mtDNA) depletion syndrome (MDS) is a group of severe, tissue-specific diseases of childhood with unknown pathogenesis. Brain-specific MDS manifests as devastating spongiotic encephalopathy with no curative therapy. Here, we report cell type-specific stress responses and effects of rapamycin treatment and ketogenic diet (KD) in mice with spongiotic encephalopathy mimicking human MDS, as these interventions were reported to improve some mitochondrial disease signs or symptoms. These mice with astrocyte-specific knockout of Twnk gene encoding replicative mtDNA helicase Twinkle (TwKOastro) show wide-spread cell-autonomous astrocyte activation and mitochondrial integrated stress response (ISRmt) induction with major metabolic remodeling of the brain. Mice with neuronal-specific TwKO show no ISRmt Both KD and rapamycin lead to rapid deterioration and weight loss of TwKOastro and premature trial termination. Although rapamycin had no robust effects on TwKOastro brain pathology, KD exacerbated spongiosis, gliosis, and ISRmt Our evidence emphasizes that mitochondrial disease treatments and stress responses are tissue- and disease specific. Furthermore, rapamycin and KD are deleterious in MDS-linked spongiotic encephalopathy, pointing to a crucial role of diet and metabolism for mitochondrial disease progression.
Assuntos
Encefalopatias/fisiopatologia , Doenças Mitocondriais/fisiopatologia , Estresse Fisiológico/fisiologia , Animais , Astrócitos/metabolismo , Encefalopatias/metabolismo , DNA Helicases/genética , Replicação do DNA/genética , DNA Mitocondrial/genética , Dieta Cetogênica/métodos , Modelos Animais de Doenças , Feminino , Cetose/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Mitocôndrias/genética , Doenças Mitocondriais/genética , Proteínas Mitocondriais/genética , Mutação , Neurônios/metabolismo , Sirolimo/farmacologiaRESUMO
Mitochondrial dysfunction manifests as different neurological diseases, but the mechanisms underlying the clinical variability remain poorly understood. To clarify whether different brain cells have differential sensitivity to mitochondrial dysfunction, we induced mitochondrial DNA (mtDNA) depletion in either neurons or astrocytes of mice, by inactivating Twinkle (TwKO), the replicative mtDNA helicase. Here we show that astrocytes, the most abundant cerebral cell type, are chronically activated upon mtDNA loss, leading to early-onset spongiotic degeneration of brain parenchyma, microgliosis and secondary neurodegeneration. Neuronal mtDNA loss does not, however, cause symptoms until 8 months of age. Findings in astrocyte-TwKO mimic neuropathology of Alpers syndrome, infantile-onset mitochondrial spongiotic encephalopathy caused by mtDNA maintenance defects. Our evidence indicates that (1) astrocytes are dependent on mtDNA integrity; (2) mitochondrial metabolism contributes to their activation; (3) chronic astrocyte activation has devastating consequences, underlying spongiotic encephalopathy; and that (4) astrocytes are a potential target for interventions.
Assuntos
Astrócitos/metabolismo , Encefalopatias/genética , DNA Mitocondrial/genética , Doenças Mitocondriais/genética , Animais , Encéfalo/metabolismo , Encéfalo/ultraestrutura , DNA Helicases/genética , DNA Helicases/metabolismo , DNA Mitocondrial/metabolismo , Camundongos Knockout , Microscopia Eletrônica , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismo , Mutação , Neurônios/metabolismoRESUMO
Intraspecific hybrid dysgenesis (HD) appears after some strains of D. melanogaster are crossed. The predominant idea is that the movement of transposable P elements causes HD. It is believed that P elements appeared in the D. melanogaster genome in the middle of the last century by horizontal transfer, simultaneously with the appearance of HD determinants. A subsequent simultaneous expansion of HD determinants and P elements occurred. We analyzed the current distribution of HD determinants in natural populations of D. melanogaster and found no evidence of their further spread. However, full-sized P elements were identified in the genomes of all analyzed natural D. melanogaster strains independent of their cytotypes. Thus, the expansion of P elements does not correlate with the expansion of HD determinants. We found that the ovaries of dysgenic females did not contain germ cells despite the equal number of primordial germ cells in early stages in dysgenic and non-dysgenic embryos. We propose that HD does not result from DNA damage caused by P element transposition, but it would be the disruption in the regulation of dysgenic ovarian formation that causes the dysgenic phenotypes.