RESUMO
Abnormalities of one carbon, glutathione and sulfide metabolisms have recently emerged as novel pathomechanisms in diseases with mitochondrial dysfunction. However, the mechanisms underlying these abnormalities are not clear. Also, we recently showed that sulfide oxidation is impaired in Coenzyme Q10 (CoQ10) deficiency. This finding leads us to hypothesize that the therapeutic effects of CoQ10, frequently administered to patients with primary or secondary mitochondrial dysfunction, might be due to its function as cofactor for sulfide:quinone oxidoreductase (SQOR), the first enzyme in the sulfide oxidation pathway. Here, using biased and unbiased approaches, we show that supraphysiological levels of CoQ10 induces an increase in the expression of SQOR in skin fibroblasts from control subjects and patients with mutations in Complex I subunits genes or CoQ biosynthetic genes. This increase of SQOR induces the downregulation of the cystathionine ß-synthase and cystathionine γ-lyase, two enzymes of the transsulfuration pathway, the subsequent downregulation of serine biosynthesis and the adaptation of other sulfide linked pathways, such as folate cycle, nucleotides metabolism and glutathione system. These metabolic changes are independent of the presence of sulfur aminoacids, are confirmed in mouse models, and are recapitulated by overexpression of SQOR, further proving that the metabolic effects of CoQ10 supplementation are mediated by the overexpression of SQOR. Our results contribute to a better understanding of how sulfide metabolism is integrated in one carbon metabolism and may explain some of the benefits of CoQ10 supplementation observed in mitochondrial diseases.
Assuntos
Ataxia/patologia , Carbono/metabolismo , Complexo I de Transporte de Elétrons/metabolismo , Mitocôndrias/patologia , Doenças Mitocondriais/patologia , Debilidade Muscular/patologia , Oxirredutases atuantes sobre Doadores de Grupo Enxofre/metabolismo , Sulfetos/metabolismo , Ubiquinona/análogos & derivados , Ubiquinona/deficiência , Animais , Ataxia/genética , Ataxia/metabolismo , Transporte de Elétrons , Complexo I de Transporte de Elétrons/genética , Fibroblastos/efeitos dos fármacos , Fibroblastos/metabolismo , Fibroblastos/patologia , Glutationa/metabolismo , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Mitocôndrias/metabolismo , Doenças Mitocondriais/genética , Doenças Mitocondriais/metabolismo , Debilidade Muscular/genética , Debilidade Muscular/metabolismo , Oxirredutases atuantes sobre Doadores de Grupo Enxofre/genética , Pele/efeitos dos fármacos , Pele/metabolismo , Pele/patologia , Transcriptoma , Ubiquinona/genética , Ubiquinona/metabolismo , Ubiquinona/farmacologia , Vitaminas/farmacologiaRESUMO
X-linked scapuloperoneal myopathy (X-SM), one of Four-and-a-half LIM 1 (FHL1) related diseases, is an adult-onset slowly progressive myopathy, often associated with cardiomyopathy. We previously generated a knock-in mouse model that has the same mutation (c.365 G > C, p.W122S) as human X-SM patients. The mutant male mouse developed late-onset slowly progressive myopathy without cardiomyopathy. In this study, we observed that heterozygous (Het) and homozygous (Homo) female mice did not show alterations of skeletal muscle function or histology. In contrast, 20-month-old mutant female mice showed signs of cardiomyopathy on echocardiograms with increased systolic diameter [wild-type (WT): 2.74 ± 0.22 mm, mean ± standard deviation (SD); Het: 3.13 ± 0.11 mm, P < 0.01; Homo: 3.08 ± 0.37 mm, P < 0.05) and lower fractional shortening (WT: 31.1 ± 4.4%, mean ± SD; Het: 22.7 ± 2.5%, P < 0.01; Homo: 22.4 ± 6.9%, P < 0.01]. Histological analysis of cardiac muscle revealed frequent extraordinarily large rectangular nuclei in mutant female mice that were also observed in human cardiac muscle from X-SM patients. Western blot demonstrated decreased Fhl1 protein levels in cardiac muscle, but not in skeletal muscle, of Homo mutant female mice. Proteomic analysis of cardiac muscle from 20-month-old Homo mutant female mice indicated abnormalities of the integrin signaling pathway (ISP) in association with cardiac dysfunction. The ISP dysregulation was further supported by altered levels of a subunit of the ISP downstream effectors Arpc1a in Fhl1 mutant mice and ARPC1A in X-SM patient muscles. This study reveals the first mouse model of FHL1-related cardiomyopathy and implicates ISP dysregulation in the pathogenesis of FHL1 myopathy.
Assuntos
Actinas/metabolismo , Cardiomiopatias/genética , Integrinas/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/genética , Proteínas com Domínio LIM/genética , Proteínas Musculares/genética , Animais , Composição Corporal , Peso Corporal , Cardiomiopatias/patologia , Ecocardiografia , Feminino , Heterozigoto , Homozigoto , Masculino , Camundongos , Músculo Esquelético/patologia , Doenças Musculares/genética , Distrofia Muscular de Emery-Dreifuss/genética , Mutação de Sentido Incorreto , Miocárdio/patologia , Fenótipo , Proteômica , Transdução de SinaisRESUMO
Fragile X syndrome (FXS) is the leading known inherited intellectual disability and the most common genetic cause of autism. The full mutation results in transcriptional silencing of the Fmr1 gene and loss of fragile X mental retardation protein (FMRP) expression. Defects in neuroenergetic capacity are known to cause a variety of neurodevelopmental disorders. Thus, we explored the integrity of forebrain mitochondria in Fmr1 knockout mice during the peak of synaptogenesis. We found inefficient thermogenic respiration due to futile proton leak in Fmr1 KO mitochondria caused by coenzyme Q (CoQ) deficiency and an open cyclosporine-sensitive channel. Repletion of mitochondrial CoQ within the Fmr1 KO forebrain closed the channel, blocked the pathological proton leak, restored rates of protein synthesis during synaptogenesis, and normalized the key phenotypic features later in life. The findings demonstrate that FMRP deficiency results in inefficient oxidative phosphorylation during the neurodevelopment and suggest that dysfunctional mitochondria may contribute to the FXS phenotype.
Assuntos
Respiração Celular/fisiologia , Síndrome do Cromossomo X Frágil/metabolismo , Síndrome do Cromossomo X Frágil/patologia , Mitocôndrias/metabolismo , Mitocôndrias/patologia , Termogênese/fisiologia , Animais , Transtorno Autístico/metabolismo , Transtorno Autístico/patologia , Modelos Animais de Doenças , Feminino , Proteína do X Frágil da Deficiência Intelectual/metabolismo , Deficiência Intelectual/metabolismo , Deficiência Intelectual/patologia , Masculino , Camundongos , Camundongos Knockout , Neurogênese/fisiologia , PrótonsRESUMO
Multiple sclerosis is an autoimmune demyelinating disorder of the CNS, characterized by inflammatory lesions and an underlying neurodegenerative process, which is more prominent in patients with progressive disease course. It has been proposed that mitochondrial dysfunction underlies neuronal damage, the precise mechanism by which this occurs remains uncertain. To investigate potential mechanisms of neurodegeneration, we conducted a functional screening of mitochondria in neurons exposed to the CSF of multiple sclerosis patients with a relapsing remitting (n = 15) or a progressive (secondary, n = 15 or primary, n = 14) disease course. Live-imaging of CSF-treated neurons, using a fluorescent mitochondrial tracer, identified mitochondrial elongation as a unique effect induced by the CSF from progressive patients. These morphological changes were associated with decreased activity of mitochondrial complexes I, III and IV and correlated with axonal damage. The effect of CSF treatment on the morphology of mitochondria was characterized by phosphorylation of serine 637 on the dynamin-related protein DRP1, a post-translational modification responsible for unopposed mitochondrial fusion in response to low glucose conditions. The effect of neuronal treatment with CSF from progressive patients was heat stable, thereby prompting us to conduct an unbiased exploratory lipidomic study that identified specific ceramide species as differentially abundant in the CSF of progressive patients compared to relapsing remitting multiple sclerosis. Treatment of neurons with medium supplemented with ceramides, induced a time-dependent increase of the transcripts levels of specific glucose and lactate transporters, which functionally resulted in progressively increased glucose uptake from the medium. Thus ceramide levels in the CSF of patients with progressive multiple sclerosis not only impaired mitochondrial respiration but also decreased the bioavailability of glucose by increasing its uptake. Importantly the neurotoxic effect of CSF treatment could be rescued by exogenous supplementation with glucose or lactate, presumably to compensate the inefficient fuel utilization. Together these data suggest a condition of 'virtual hypoglycosis' induced by the CSF of progressive patients in cultured neurons and suggest a critical temporal window of intervention for the rescue of the metabolic impairment of neuronal bioenergetics underlying neurodegeneration in multiple sclerosis patients.
Assuntos
Líquido Cefalorraquidiano/química , Metabolismo Energético/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Esclerose Múltipla Crônica Progressiva/líquido cefalorraquidiano , Esclerose Múltipla Recidivante-Remitente/líquido cefalorraquidiano , Neurônios/efeitos dos fármacos , Animais , Ceramidas/líquido cefalorraquidiano , Ceramidas/isolamento & purificação , Ceramidas/toxicidade , Dinaminas/química , Glucose/metabolismo , Glucose/farmacologia , Temperatura Alta , Microscopia Intravital , Lactatos/metabolismo , Lactatos/farmacologia , Lipidômica , Mitocôndrias/metabolismo , Mitocôndrias/patologia , Esclerose Múltipla Crônica Progressiva/patologia , Esclerose Múltipla Recidivante-Remitente/patologia , Degeneração Neural , Fosforilação , Processamento de Proteína Pós-Traducional , RatosRESUMO
Muscle mitochondrial dysfunction is implicated in intensive care unit-acquired weakness, but there is no serum biomarker of muscle mitochondrial function for critical illness survivors. Higher serum growth differentiation factor-15 (GDF-15) is a biomarker of inherited mitochondrial myopathy disease and is associated with mortality in several age-related diseases. Among 142 older (age ≥ 65 years) survivors of acute respiratory failure, we found that higher serum GDF-15 measured during the week prior to hospital discharge was cross-sectionally associated with weaker diaphragm, limb and hand-grip strength, and longitudinally associated with lower rates of functional recovery over 6 months, independent of age, sex, pre-existing disability, comorbidity, frailty, Acute Physiology and Chronic Health Evaluation II scores and concurrent interleukin-6 levels.
Assuntos
Diafragma/fisiopatologia , Fator 15 de Diferenciação de Crescimento/sangue , Força da Mão , Insuficiência Respiratória/sangue , Doença Aguda , Idoso , Idoso de 80 Anos ou mais , Biomarcadores/sangue , Estudos Transversais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Recuperação de Função Fisiológica , Insuficiência Respiratória/fisiopatologia , SobreviventesRESUMO
AMP-activated protein kinase (AMPK) regulates many different metabolic pathways in eukaryote cells including mitochondria biogenesis and energy homeostasis. Here we identify a patient with hypotonia, weakness, delayed milestones and neurological impairment since birth harbouring a novel homozygous mutation in the AMPK catalytic α-subunit 1, encoded by the PRKAA1 gene. The homozygous mutation p.S487L in isoform 1 present in the patient is in a cryptic residue for AMPK activity. In the present study, we performed the characterization of mitochondrial respiratory properties of the patient, in comparison to healthy controls, through the culture of skin fibroblasts in order to understand some of the cellular consequences of the PRKAA1 mutation. In these assays, mitochondrial respiratory complex I showed lower activity, which was followed by a decrement in the mtDNA copy number, which is a probable consequence of the lower expression of PGC-1α and PRKAA1 itself as measured in our quantitative PCRs experiments. Confirming the effect of the patient mutation in respiration, transfection of patient fibroblasts with wild type PRKAA1 partially restore complex I level. The preliminary clinic evaluations of the patient suggested a metabolic defect related to the mitochondrial respiratory function, therefore treatment with CoQ10 supplementation dose started four years ago and a clear improvement in motor skills and strength has been achieved with this treatment.
Assuntos
Proteínas Quinases Ativadas por AMP , Fibroblastos , Homozigoto , Mitocôndrias , Mutação de Sentido Incorreto , Consumo de Oxigênio , Proteínas Quinases Ativadas por AMP/genética , Proteínas Quinases Ativadas por AMP/metabolismo , Substituição de Aminoácidos , Pré-Escolar , Complexo I de Transporte de Elétrons/genética , Complexo I de Transporte de Elétrons/metabolismo , Fibroblastos/metabolismo , Fibroblastos/patologia , Humanos , Masculino , Mitocôndrias/genética , Mitocôndrias/metabolismo , Mitocôndrias/patologia , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo/genética , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo/metabolismoRESUMO
Ataxia oculomotor apraxia type 1 (AOA1) is an autosomal recessive disease caused by mutations in APTX, which encodes the DNA strand-break repair protein aprataxin (APTX). CoQ10 deficiency has been identified in fibroblasts and muscle of AOA1 patients carrying the common W279X mutation, and aprataxin has been localized to mitochondria in neuroblastoma cells, where it enhances preservation of mitochondrial function. In this study, we show that aprataxin deficiency impairs mitochondrial function, independent of its role in mitochondrial DNA repair. The bioenergetics defect in AOA1-mutant fibroblasts and APTX-depleted Hela cells is caused by decreased expression of SDHA and genes encoding CoQ biosynthetic enzymes, in association with reductions of APE1, NRF1 and NRF2. The biochemical and molecular abnormalities in APTX-depleted cells are recapitulated by knockdown of APE1 in Hela cells and are rescued by overexpression of NRF1/2. Importantly, pharmacological upregulation of NRF1 alone by 5-aminoimidazone-4-carboxamide ribonucleotide does not rescue the phenotype, which, in contrast, is reversed by the upregulation of NRF2 by rosiglitazone. Accordingly, we propose that the lack of aprataxin causes reduction of the pathway APE1/NRF1/NRF2 and their target genes. Our findings demonstrate a critical role of APTX in transcription regulation of mitochondrial function and the pathogenesis of AOA1 via a novel pathomechanistic pathway, which may be relevant to other neurodegenerative diseases.
Assuntos
DNA Liase (Sítios Apurínicos ou Apirimidínicos)/biossíntese , Proteínas de Ligação a DNA/deficiência , Regulação para Baixo , Fibroblastos/metabolismo , Mitocôndrias/metabolismo , Fator 2 Relacionado a NF-E2/biossíntese , Proteínas Nucleares/deficiência , Fator 1 Nuclear Respiratório/biossíntese , Transdução de Sinais , Ataxia/genética , Ataxia/metabolismo , Ataxia/patologia , DNA Liase (Sítios Apurínicos ou Apirimidínicos)/genética , Proteínas de Ligação a DNA/genética , Feminino , Fibroblastos/patologia , Doenças Genéticas Inatas/genética , Doenças Genéticas Inatas/metabolismo , Doenças Genéticas Inatas/patologia , Humanos , Masculino , Mitocôndrias/patologia , Fator 2 Relacionado a NF-E2/genética , Proteínas Nucleares/genética , Fator 1 Nuclear Respiratório/genéticaRESUMO
A member of the four-and-a-half-LIM (FHL) domain protein family, FHL1, is highly expressed in human adult skeletal and cardiac muscle. Mutations in FHL1 have been associated with diverse X-linked muscle diseases: scapuloperoneal (SP) myopathy, reducing body myopathy, X-linked myopathy with postural muscle atrophy, rigid spine syndrome (RSS) and Emery-Dreifuss muscular dystrophy. In 2008, we identified a missense mutation in the second LIM domain of FHL1 (c.365 G>C, p.W122S) in a family with SP myopathy. We generated a knock-in mouse model harboring the c.365 G>C Fhl1 mutation and investigated the effects of this mutation at three time points (3-5 months, 7-10 months and 18-20 months) in hemizygous male and heterozygous female mice. Survival was comparable in mutant and wild-type animals. We observed decreased forelimb strength and exercise capacity in adult hemizygous male mice starting from 7 to 10 months of age. Western blot analysis showed absence of Fhl1 in muscle at later stages. Thus, adult hemizygous male, but not heterozygous female, mice showed a slowly progressive phenotype similar to human patients with late-onset muscle weakness. In contrast to SP myopathy patients with the FHL1 W122S mutation, mutant mice did not manifest cytoplasmic inclusions (reducing bodies) in muscle. Because muscle weakness was evident prior to loss of Fhl1 protein and without reducing bodies, our findings indicate that loss of function is responsible for the myopathy in the Fhl1 W122S knock-in mice.
Assuntos
Membro Anterior/patologia , Peptídeos e Proteínas de Sinalização Intracelular/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas com Domínio LIM/genética , Proteínas com Domínio LIM/metabolismo , Proteínas Musculares/genética , Proteínas Musculares/metabolismo , Músculo Esquelético/patologia , Distrofia Muscular de Emery-Dreifuss/patologia , Miocárdio/patologia , Idade de Início , Animais , Modelos Animais de Doenças , Feminino , Técnicas de Introdução de Genes , Hemizigoto , Heterozigoto , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Distrofia Muscular de Emery-Dreifuss/epidemiologia , Distrofia Muscular de Emery-Dreifuss/genética , Distrofia Muscular de Emery-Dreifuss/metabolismo , Mutação de Sentido IncorretoRESUMO
Defects of mitochondrial protein synthesis are clinically and genetically heterogeneous. We previously described a male infant who was born to consanguineous parents and who presented with severe congenital encephalopathy, peripheral neuropathy, myopathy, and lactic acidosis associated with deficiencies of multiple mitochondrial respiratory-chain enzymes and defective mitochondrial translation. In this work, we have characterized four additional affected family members, performed homozygosity mapping, and identified a homozygous splicing mutation in the splice donor site of exon 2 (c.504+1G>A) of RMND1 (required for meiotic nuclear division-1) in the affected individuals. Fibroblasts from affected individuals expressed two aberrant transcripts and had decreased wild-type mRNA and deficiencies of mitochondrial respiratory-chain enzymes. The RMND1 mutation caused haploinsufficiency that was rescued by overexpression of the wild-type transcript in mutant fibroblasts; this overexpression increased the levels and activities of mitochondrial respiratory-chain proteins. Knockdown of RMND1 via shRNA recapitulated the biochemical defect of the mutant fibroblasts, further supporting a loss-of-function pathomechanism in this disease. RMND1 belongs to the sif2 family, an evolutionary conserved group of proteins that share the DUF155 domain, have unknown function, and have never been associated with human disease. We documented that the protein localizes to mitochondria in mammalian and yeast cells. Further studies are necessary for understanding the function of this protein in mitochondrial protein translation.
Assuntos
Proteínas de Ciclo Celular/genética , Mitocôndrias/genética , Encefalomiopatias Mitocondriais/genética , Proteínas Mitocondriais/genética , Mutação , Biossíntese de Proteínas , Consanguinidade , DNA Mitocondrial/genética , Éxons , Fibroblastos/metabolismo , Predisposição Genética para Doença , Homozigoto , Humanos , Recém-Nascido , Masculino , Encefalomiopatias Mitocondriais/metabolismo , Sítios de Splice de RNA/genética , Splicing de RNA/genética , RNA Mensageiro/genéticaRESUMO
Primary human CoQ(10) deficiencies are clinically heterogeneous diseases caused by mutations in PDSS2 and other genes required for CoQ(10) biosynthesis. Our in vitro studies of PDSS2 mutant fibroblasts, with <20% CoQ(10) of control cells, revealed reduced activity of CoQ(10)-dependent complex II+III and ATP synthesis, without amplification of reactive oxygen species (ROS), markers of oxidative damage, or antioxidant defenses. In contrast, COQ2 and ADCK3 mutant fibroblasts, with 30-50% CoQ(10) of controls, showed milder bioenergetic defects but significantly increased ROS and oxidation of lipids and proteins. We hypothesized that absence of oxidative stress markers and cell death in PDSS2 mutant fibroblasts were due to the extreme severity of CoQ(10) deficiency. Here, we have investigated in vivo effects of Pdss2 deficiency in affected and unaffected organs of CBA/Pdss2(kd/kd) mice at presymptomatic, phenotypic-onset, and end-stages of the disease. Although Pdss2 mutant mice manifest widespread CoQ(9) deficiency and mitochondrial respiratory chain abnormalities, only affected organs show increased ROS production, oxidative stress, mitochondrial DNA depletion, and reduced citrate synthase activity, an index of mitochondrial mass. Our data indicate that kidney-specific loss of mitochondria triggered by oxidative stress may be the cause of renal failure in Pdss2(kd/kd) mice.
Assuntos
Alquil e Aril Transferases/deficiência , Alquil e Aril Transferases/genética , Mitocôndrias/metabolismo , Ubiquinona/deficiência , Difosfato de Adenosina/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , DNA Mitocondrial/genética , DNA Mitocondrial/metabolismo , Transporte de Elétrons , Fibroblastos/metabolismo , Humanos , Rim/metabolismo , Rim/patologia , Camundongos , Camundongos Endogâmicos CBA , Camundongos Mutantes , Estresse Oxidativo , Distribuição TecidualRESUMO
Coenzyme Q (CoQ) deficiency syndrome is conventionally treated with limited efficacy using exogenous CoQ10. Poor outcomes result from low absorption and bioavailability of CoQ10 and the clinical heterogenicity of the disease. Here, we demonstrate that supplementation with 4-hydroxybenzoic acid (4HB), the precursor of the benzoquinone ring in the CoQ biosynthetic pathway, completely rescues multisystemic disease and perinatal lethality in a mouse model of CoQ deficiency. 4HB stimulates endogenous CoQ biosynthesis in tissues of Coq2 mutant mice, normalizing mitochondrial function and rescuing cardiac insufficiency, edema, and neurodevelopmental delay. In contrast, exogenous CoQ10 supplementation falls short in fully restoring the phenotype. The treatment is translatable to human use, as proven by in vitro studies in skin fibroblasts from patients with pathogenic variants in COQ2. The therapeutic approach extends to other disorders characterized by deficiencies in the production of 4HB and early steps of CoQ biosynthesis and instances of secondary CoQ deficiency.
Assuntos
Modelos Animais de Doenças , Doenças Mitocondriais , Parabenos , Ubiquinona , Animais , Doenças Mitocondriais/tratamento farmacológico , Doenças Mitocondriais/patologia , Doenças Mitocondriais/metabolismo , Parabenos/farmacologia , Ubiquinona/análogos & derivados , Ubiquinona/farmacologia , Ubiquinona/metabolismo , Ubiquinona/deficiência , Camundongos , Mitocôndrias/metabolismo , Mitocôndrias/efeitos dos fármacos , Humanos , Fibroblastos/metabolismo , Fibroblastos/efeitos dos fármacos , Camundongos Endogâmicos C57BL , Debilidade Muscular/tratamento farmacológico , Debilidade Muscular/metabolismo , Debilidade Muscular/patologia , Ataxia/tratamento farmacológico , Ataxia/patologia , Ataxia/metabolismoRESUMO
BACKGROUND: Although causative mutations have been identified for numerous mitochondrial disorders, few disease-modifying treatments are available. Two examples of treatable mitochondrial disorders are coenzyme Q(10) (CoQ(10) or ubiquinone) deficiency and mitochondrial neurogastrointestinal encephalomyopathy (MNGIE). SCOPE OF REVIEW: Here, we describe clinical and molecular features of CoQ(10) deficiencies and MNGIE and explain how understanding their pathomechanisms have led to rationale therapies. Primary CoQ(10) deficiencies, due to mutations in genes required for ubiquinone biosynthesis, and secondary deficiencies, caused by genetic defects not directly related to CoQ(10) biosynthesis, often improve with CoQ(10) supplementation. In vitro and in vivo studies of CoQ(10) deficiencies have revealed biochemical alterations that may account for phenotypic differences among patients and variable responses to therapy. In contrast to the heterogeneous CoQ(10) deficiencies, MNGIE is a single autosomal recessive disease due to mutations in the TYMP gene encoding thymidine phosphorylase (TP). In MNGIE, loss of TP activity causes toxic accumulations of the nucleosides thymidine and deoxyuridine that are incorporated by the mitochondrial pyrimidine salvage pathway and cause deoxynucleoside triphosphate pool imbalances, which, in turn cause mtDNA instability. Allogeneic hematopoetic stem cell transplantation to restore TP activity and eliminate toxic metabolites is a promising therapy for MNGIE. MAJOR CONCLUSIONS: CoQ(10) deficiencies and MNGIE demonstrate the feasibility of treating specific mitochondrial disorders through replacement of deficient metabolites or via elimination of excessive toxic molecules. GENERAL SIGNIFICANCE: Studies of CoQ(10) deficiencies and MNGIE illustrate how understanding the pathogenic mechanisms of mitochondrial diseases can lead to meaningful therapies. This article is part of a Special Issue entitled: Biochemistry of Mitochondria, Life and Intervention 2010.
Assuntos
Doenças Mitocondriais/terapia , Encefalomiopatias Mitocondriais/terapia , Timidina Fosforilase/deficiência , Ubiquinona/análogos & derivados , Humanos , Doenças Mitocondriais/genética , Doenças Mitocondriais/metabolismo , Encefalomiopatias Mitocondriais/genética , Encefalomiopatias Mitocondriais/metabolismo , Ubiquinona/deficiênciaRESUMO
Coenzyme Q(10) is a mobile lipophilic electron carrier located in the inner mitochondrial membrane. Defects of coenzyme Q(10) biosynthesis represent one of the few treatable mitochondrial diseases. We genotyped a patient with primary coenzyme Q(10) deficiency who presented with neonatal lactic acidosis and later developed multisytem disease including intractable seizures, global developmental delay, hypertrophic cardiomyopathy, and renal tubular dysfunction. Cultured skin fibroblasts from the patient had a coenzyme Q(10) biosynthetic rate of 11% of normal controls and accumulated an abnormal metabolite that we believe to be a biosynthetic intermediate. In view of the rarity of coenzyme Q(10) deficiency, we hypothesized that the disease-causing gene might lie in a region of ancestral homozygosity by descent. Data from an Illumina HumanHap550 array were analyzed with BeadStudio software. Sixteen regions of homozygosity >1.5 Mb were identified in the affected infant. Two of these regions included the loci of two of 16 candidate genes implicated in human coenzyme Q(10) biosynthesis. Sequence analysis demonstrated a homozygous stop mutation affecting a highly conserved residue of COQ9, leading to the truncation of 75 amino acids. Site-directed mutagenesis targeting the equivalent residue in the yeast Saccharomyces cerevisiae abolished respiratory growth.
Assuntos
Códon sem Sentido , Predisposição Genética para Doença , Doenças Mitocondriais/genética , Ubiquinona/deficiência , Ubiquinona/metabolismo , Sequência de Aminoácidos , Células Cultivadas , Fibroblastos/metabolismo , Homozigoto , Humanos , Lactente , Recém-Nascido , Doenças Mitocondriais/metabolismo , Modelos Moleculares , Dados de Sequência Molecular , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/crescimento & desenvolvimento , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Pele/patologia , Ubiquinona/genéticaRESUMO
Coenzyme Q (CoQ) is a conserved polyprenylated lipid composed of a redox-active benzoquinone ring and a long polyisoprenyl tail that serves as a membrane anchor. CoQ biosynthesis involves multiple steps, including multiple modifications of the precursor ring 4-hydroxybenzoic acid. Mutations in the enzymes involved in CoQ biosynthesis pathway result in primary coenzyme Q deficiencies, mitochondrial disorders whose clinical heterogenicity reflects the multiple biological function of CoQ. Patients with these disorders do not always respond to CoQ supplementation, and CoQ analogs have not been successful as alternative approaches. Progress made in understanding the CoQ biosynthesis pathway and studies of supplementation with 4-hydroxybenzoic acid ring analogs have opened a new area in the field of primary CoQ deficiencies treatment. Here, we will review these studies, focusing on efficacy of the different 4-hydroxybenzoic acid ring analogs, models in which they have been tested, and their mechanisms of action. Understanding how these compounds ameliorate biochemical, molecular, and/or clinical phenotypes of CoQ deficiencies is important to develop the most rational treatment for CoQ deficient patients, depending on their molecular defects.
RESUMO
Scapuloperoneal (SP) syndrome encompasses heterogeneous neuromuscular disorders characterized by weakness in the shoulder-girdle and peroneal muscles. In a large Italian-American pedigree with dominant SP myopathy (SPM) previously linked to chromosome 12q, we have mapped the disease to Xq26, and, in all of the affected individuals, we identified a missense change (c.365G-->C) in the FHL1 gene encoding four-and-a-half-LIM protein 1 (FHL1). The mutation substitutes a serine for a conserved trypophan at amino acid 122 in the second LIM domain of the protein. Western blot analyses of muscle extracts revealed FHL1 loss that paralleled disease severity. FHL1 and an isoform, FHL1C, are highly expressed in skeletal muscle and may contribute to stability of sarcomeres and sarcolemma, myofibrillary assembly, and transcriptional regulation. This is the first report, to our knowledge, of X-linked dominant SP myopathy and the first human mutation in FHL1.
Assuntos
Peptídeos e Proteínas de Sinalização Intracelular/genética , Proteínas Musculares/genética , Distrofia Muscular de Emery-Dreifuss/genética , Mutação de Sentido Incorreto , Sequência de Aminoácidos , Substituição de Aminoácidos , Feminino , Genes Dominantes , Genes Ligados ao Cromossomo X , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/química , Proteínas com Domínio LIM , Masculino , Modelos Moleculares , Dados de Sequência Molecular , Proteínas Musculares/química , Linhagem , Estrutura Terciária de ProteínaRESUMO
Muscle coenzyme Q(10) (CoQ(10) or ubiquinone) deficiency has been identified in more than 20 patients with presumed autosomal-recessive ataxia. However, mutations in genes required for CoQ(10) biosynthetic pathway have been identified only in patients with infantile-onset multisystemic diseases or isolated nephropathy. Our SNP-based genome-wide scan in a large consanguineous family revealed a locus for autosomal-recessive ataxia at chromosome 1q41. The causative mutation is a homozygous splice-site mutation in the aarF-domain-containing kinase 3 gene (ADCK3). Five additional mutations in ADCK3 were found in three patients with sporadic ataxia, including one known to have CoQ(10) deficiency in muscle. All of the patients have childhood-onset cerebellar ataxia with slow progression, and three of six have mildly elevated lactate levels. ADCK3 is a mitochondrial protein homologous to the yeast COQ8 and the bacterial UbiB proteins, which are required for CoQ biosynthesis. Three out of four patients tested showed a low endogenous pool of CoQ(10) in their fibroblasts or lymphoblasts, and two out of three patients showed impaired ubiquinone synthesis, strongly suggesting that ADCK3 is also involved in CoQ(10) biosynthesis. The deleterious nature of the three identified missense changes was confirmed by the introduction of them at the corresponding positions of the yeast COQ8 gene. Finally, a phylogenetic analysis shows that ADCK3 belongs to the family of atypical kinases, which includes phosphoinositide and choline kinases, suggesting that ADCK3 plays an indirect regulatory role in ubiquinone biosynthesis possibly as part of a feedback loop that regulates ATP production.
Assuntos
Ataxia Cerebelar/genética , Genes Recessivos , Ubiquinona/análogos & derivados , Sequência de Aminoácidos , Encéfalo/patologia , Ataxia Cerebelar/enzimologia , Coenzimas/deficiência , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Dados de Sequência Molecular , Mutação , Linhagem , Fosfotransferases/genética , Análise de Sequência de DNA , Ubiquinona/deficiência , Ubiquinona/genética , Leveduras/genéticaRESUMO
Coenzyme Q(10) (CoQ(10)) is essential for electron transport in the mitochondrial respiratory chain and antioxidant defense. The relative importance of respiratory chain defects, ROS production, and apoptosis in the pathogenesis of CoQ(10) deficiency is unknown. We determined previously that severe CoQ(10) deficiency in cultured skin fibroblasts harboring COQ2 and PDSS2 mutations produces divergent alterations of bioenergetics and oxidative stress. Here, to better understand the pathogenesis of CoQ(10) deficiency, we have characterized the effects of varying severities of CoQ(10) deficiency on ROS production and mitochondrial bioenergetics in cells harboring genetic defects of CoQ(10) biosynthesis. Levels of CoQ(10) seem to correlate with ROS production; 10-15% and >60% residual CoQ(10) are not associated with significant ROS production, whereas 30-50% residual CoQ(10) is accompanied by increased ROS production and cell death. Our results confirm that varying degrees of CoQ(10) deficiency cause variable defects of ATP synthesis and oxidative stress. These findings may lead to more rational therapeutic strategies for CoQ(10) deficiency.
Assuntos
Morte Celular , Estresse Oxidativo , Espécies Reativas de Oxigênio/metabolismo , Ubiquinona/análogos & derivados , Células Cultivadas , DNA Mitocondrial/metabolismo , Metabolismo Energético , Humanos , Ubiquinona/deficiênciaRESUMO
We studied three patients with mutations in the senataxin gene (SETX). One had juvenile onset of ALS. The second case resembled hereditary motor neuropathy. The third patient had an overlap syndrome of ataxia-tremor and motor neuron disease, phenotypes previously associated with SETX mutations. Our patients were all apparently sporadic, with no other affected relative. Two relatives of patient no. 2 carried the SETX c.4660T > G transversion but did not manifest motor neuron disease, abnormal eye movements, ataxia, or tremor suggesting that genetic or environmental modifiers may influence expression of this SETX polymorphism. Relatives of patients 1 and 3 were not available for examination or SETX mutation screening. Mutations causing ALS4 may be more frequent and heterogeneous than expected. Screening for SETX mutations should be considered in patients with apparently sporadic juvenile-onset ALS, hereditary motor neuropathy, and overlap syndromes with ataxia and motor neuron disease.
Assuntos
Esclerose Lateral Amiotrófica/genética , Mutação , RNA Helicases/genética , Adolescente , Adulto , Sequência de Aminoácidos , Esclerose Lateral Amiotrófica/fisiopatologia , Animais , DNA Helicases , Feminino , Humanos , Masculino , Dados de Sequência Molecular , Enzimas Multifuncionais , Alinhamento de Sequência , Adulto JovemRESUMO
BACKGROUND: Mitochondrial disorders are genetic diseases for which therapy remains woefully inadequate. Therapy of these disorders is particularly challenging partially due to the heterogeneity and tissue-specificity of pathomechanisms involved in these disorders. Abnormalities in hydrogen sulfide (H2S) metabolism are emerging as novel mechanism in mitochondrial dysfunction. However, further studies are necessary to understand the effects, protective or detrimental, of these abnormalities, and their relevance, in mitochondrial diseases. AIM OF REVIEW: To review the recent evidences of derangement of the metabolism of H2S, at biosynthesis or oxidation levels, in mitochondrial dysfunction, focusing specifically on the alterations of H2S oxidation caused by primary Coenzyme Q (CoQ) deficiency. KEY SCIENTIFIC CONCEPTS OF REVIEW: Mitochondria play a key role in the regulation of H2S and GSH metabolism pathways. However, further studies are needed to understand the consequences of abnormalities of H2S and GSH synthesis on the oxidation pathway, and vice versa; and on the levels of H2S and GSH, their tissue-specific detrimental effects, and their role the role in mitochondrial diseases. Beside the known H2S pathways, additional, tissue-specific, enzymatic systems, involved in H2S production and elimination, might exist.