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1.
Cell ; 187(3): 659-675.e18, 2024 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-38215760

RESUMEN

The electron transport chain (ETC) of mitochondria, bacteria, and archaea couples electron flow to proton pumping and is adapted to diverse oxygen environments. Remarkably, in mice, neurological disease due to ETC complex I dysfunction is rescued by hypoxia through unknown mechanisms. Here, we show that hypoxia rescue and hyperoxia sensitivity of complex I deficiency are evolutionarily conserved to C. elegans and are specific to mutants that compromise the electron-conducting matrix arm. We show that hypoxia rescue does not involve the hypoxia-inducible factor pathway or attenuation of reactive oxygen species. To discover the mechanism, we use C. elegans genetic screens to identify suppressor mutations in the complex I accessory subunit NDUFA6/nuo-3 that phenocopy hypoxia rescue. We show that NDUFA6/nuo-3(G60D) or hypoxia directly restores complex I forward activity, with downstream rescue of ETC flux and, in some cases, complex I levels. Additional screens identify residues within the ubiquinone binding pocket as being required for the rescue by NDUFA6/nuo-3(G60D) or hypoxia. This reveals oxygen-sensitive coupling between an accessory subunit and the quinone binding pocket of complex I that can restore forward activity in the same manner as hypoxia.


Asunto(s)
Caenorhabditis elegans , Complejo I de Transporte de Electrón , Hipoxia , Animales , Ratones , Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Complejo I de Transporte de Electrón/metabolismo , Hipoxia/genética , Hipoxia/metabolismo , Mitocondrias/genética , Mitocondrias/metabolismo , Oxígeno/metabolismo
2.
Cell ; 181(3): 716-727.e11, 2020 04 30.
Artículo en Inglés | MEDLINE | ID: mdl-32259488

RESUMEN

Human cells are able to sense and adapt to variations in oxygen levels. Historically, much research in this field has focused on hypoxia-inducible factor (HIF) signaling and reactive oxygen species (ROS). Here, we perform genome-wide CRISPR growth screens at 21%, 5%, and 1% oxygen to systematically identify gene knockouts with relative fitness defects in high oxygen (213 genes) or low oxygen (109 genes), most without known connection to HIF or ROS. Knockouts of many mitochondrial pathways thought to be essential, including complex I and enzymes in Fe-S biosynthesis, grow relatively well at low oxygen and thus are buffered by hypoxia. In contrast, in certain cell types, knockout of lipid biosynthetic and peroxisomal genes causes fitness defects only in low oxygen. Our resource nominates genetic diseases whose severity may be modulated by oxygen and links hundreds of genes to oxygen homeostasis.


Asunto(s)
Metabolismo de los Lípidos/genética , Mitocondrias/genética , Oxígeno/metabolismo , Transcriptoma/genética , Hipoxia de la Célula , Pruebas Genéticas/métodos , Estudio de Asociación del Genoma Completo/métodos , Células HEK293 , Humanos , Hipoxia/metabolismo , Células K562 , Metabolismo de los Lípidos/fisiología , Lípidos/genética , Lípidos/fisiología , Mitocondrias/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Transducción de Señal/fisiología
3.
Cell ; 177(6): 1507-1521.e16, 2019 05 30.
Artículo en Inglés | MEDLINE | ID: mdl-31031004

RESUMEN

Friedreich's ataxia (FRDA) is a devastating, multisystemic disorder caused by recessive mutations in the mitochondrial protein frataxin (FXN). FXN participates in the biosynthesis of Fe-S clusters and is considered to be essential for viability. Here we report that when grown in 1% ambient O2, FXN null yeast, human cells, and nematodes are fully viable. In human cells, hypoxia restores steady-state levels of Fe-S clusters and normalizes ATF4, NRF2, and IRP2 signaling events associated with FRDA. Cellular studies and in vitro reconstitution indicate that hypoxia acts through HIF-independent mechanisms that increase bioavailable iron as well as directly activate Fe-S synthesis. In a mouse model of FRDA, breathing 11% O2 attenuates the progression of ataxia, whereas breathing 55% O2 hastens it. Our work identifies oxygen as a key environmental variable in the pathogenesis associated with FXN depletion, with important mechanistic and therapeutic implications.


Asunto(s)
Hipoxia/metabolismo , Proteínas de Unión a Hierro/metabolismo , Proteínas Hierro-Azufre/metabolismo , Factor de Transcripción Activador 4/metabolismo , Animales , Caenorhabditis elegans/metabolismo , Femenino , Ataxia de Friedreich/metabolismo , Células HEK293 , Humanos , Hipoxia/fisiopatología , Hierro/metabolismo , Proteína 2 Reguladora de Hierro/metabolismo , Proteínas de Unión a Hierro/fisiología , Proteínas Hierro-Azufre/fisiología , Células K562 , Masculino , Ratones , Ratones Noqueados , Mitocondrias/metabolismo , Proteínas Mitocondriales/metabolismo , Factor 2 Relacionado con NF-E2/metabolismo , Estrés Oxidativo , Saccharomyces cerevisiae/metabolismo , Azufre/metabolismo , Frataxina
4.
Cell ; 179(5): 1222-1238.e17, 2019 11 14.
Artículo en Inglés | MEDLINE | ID: mdl-31730859

RESUMEN

Mitochondrial dysfunction is associated with a spectrum of human conditions, ranging from rare, inborn errors of metabolism to the aging process. To identify pathways that modify mitochondrial dysfunction, we performed genome-wide CRISPR screens in the presence of small-molecule mitochondrial inhibitors. We report a compendium of chemical-genetic interactions involving 191 distinct genetic modifiers, including 38 that are synthetic sick/lethal and 63 that are suppressors. Genes involved in glycolysis (PFKP), pentose phosphate pathway (G6PD), and defense against lipid peroxidation (GPX4) scored high as synthetic sick/lethal. A surprisingly large fraction of suppressors are pathway intrinsic and encode mitochondrial proteins. A striking example of such "intra-organelle" buffering is the alleviation of a chemical defect in complex V by simultaneous inhibition of complex I, which benefits cells by rebalancing redox cofactors, increasing reductive carboxylation, and promoting glycolysis. Perhaps paradoxically, certain forms of mitochondrial dysfunction may best be buffered with "second site" inhibitors to the organelle.


Asunto(s)
Genes Modificadores , Mitocondrias/genética , Mitocondrias/patología , Autoantígenos/metabolismo , Muerte Celular/efectos de los fármacos , Citosol/efectos de los fármacos , Citosol/metabolismo , Complejo I de Transporte de Electrón/metabolismo , Epistasis Genética/efectos de los fármacos , Ferroptosis/efectos de los fármacos , Ferroptosis/genética , Genoma , Glutatión Peroxidasa/metabolismo , Glucólisis/efectos de los fármacos , Glucólisis/genética , Humanos , Células K562 , Mitocondrias/efectos de los fármacos , Oligomicinas/toxicidad , Oxidación-Reducción , Fosforilación Oxidativa/efectos de los fármacos , Vía de Pentosa Fosfato/efectos de los fármacos , Vía de Pentosa Fosfato/genética , Especies Reactivas de Oxígeno/metabolismo , Ribonucleoproteínas/metabolismo , Antígeno SS-B
5.
Cell ; 171(4): 771-782.e11, 2017 Nov 02.
Artículo en Inglés | MEDLINE | ID: mdl-29056341

RESUMEN

CLYBL encodes a ubiquitously expressed mitochondrial enzyme, conserved across all vertebrates, whose cellular activity and pathway assignment are unknown. Its homozygous loss is tolerated in seemingly healthy individuals, with reduced circulating B12 levels being the only and consistent phenotype reported to date. Here, by combining enzymology, structural biology, and activity-based metabolomics, we report that CLYBL operates as a citramalyl-CoA lyase in mammalian cells. Cells lacking CLYBL accumulate citramalyl-CoA, an intermediate in the C5-dicarboxylate metabolic pathway that includes itaconate, a recently identified human anti-microbial metabolite and immunomodulator. We report that CLYBL loss leads to a cell-autonomous defect in the mitochondrial B12 metabolism and that itaconyl-CoA is a cofactor-inactivating, substrate-analog inhibitor of the mitochondrial B12-dependent methylmalonyl-CoA mutase (MUT). Our work de-orphans the function of human CLYBL and reveals that a consequence of exposure to the immunomodulatory metabolite itaconate is B12 inactivation.


Asunto(s)
Liasas de Carbono-Carbono/metabolismo , Succinatos/metabolismo , Vitamina B 12/metabolismo , Liasas de Carbono-Carbono/química , Liasas de Carbono-Carbono/genética , Técnicas de Inactivación de Genes , Humanos , Redes y Vías Metabólicas , Mitocondrias/metabolismo , Modelos Moleculares
6.
Mol Cell ; 84(2): 359-374.e8, 2024 Jan 18.
Artículo en Inglés | MEDLINE | ID: mdl-38199006

RESUMEN

Friedreich's ataxia (FA) is a debilitating, multisystemic disease caused by the depletion of frataxin (FXN), a mitochondrial iron-sulfur (Fe-S) cluster biogenesis factor. To understand the cellular pathogenesis of FA, we performed quantitative proteomics in FXN-deficient human cells. Nearly every annotated Fe-S cluster-containing protein was depleted, indicating that as a rule, cluster binding confers stability to Fe-S proteins. We also observed depletion of a small mitoribosomal assembly factor METTL17 and evidence of impaired mitochondrial translation. Using comparative sequence analysis, mutagenesis, biochemistry, and cryoelectron microscopy, we show that METTL17 binds to the mitoribosomal small subunit during late assembly and harbors a previously unrecognized [Fe4S4]2+ cluster required for its stability. METTL17 overexpression rescued the mitochondrial translation and bioenergetic defects, but not the cellular growth, of FXN-depleted cells. These findings suggest that METTL17 acts as an Fe-S cluster checkpoint, promoting translation of Fe-S cluster-rich oxidative phosphorylation (OXPHOS) proteins only when Fe-S cofactors are replete.


Asunto(s)
Ataxia de Friedreich , Proteínas Hierro-Azufre , Humanos , Proteínas Hierro-Azufre/genética , Proteínas Hierro-Azufre/metabolismo , Microscopía por Crioelectrón , Frataxina , Biosíntesis de Proteínas , Mitocondrias/genética , Mitocondrias/metabolismo , Ataxia de Friedreich/metabolismo , Metiltransferasas/genética , Metiltransferasas/metabolismo
7.
Nature ; 629(8011): 458-466, 2024 May.
Artículo en Inglés | MEDLINE | ID: mdl-38658765

RESUMEN

Heteroplasmy occurs when wild-type and mutant mitochondrial DNA (mtDNA) molecules co-exist in single cells1. Heteroplasmy levels change dynamically in development, disease and ageing2,3, but it is unclear whether these shifts are caused by selection or drift, and whether they occur at the level of cells or intracellularly. Here we investigate heteroplasmy dynamics in dividing cells by combining precise mtDNA base editing (DdCBE)4 with a new method, SCI-LITE (single-cell combinatorial indexing leveraged to interrogate targeted expression), which tracks single-cell heteroplasmy with ultra-high throughput. We engineered cells to have synonymous or nonsynonymous complex I mtDNA mutations and found that cell populations in standard culture conditions purge nonsynonymous mtDNA variants, whereas synonymous variants are maintained. This suggests that selection dominates over simple drift in shaping population heteroplasmy. We simultaneously tracked single-cell mtDNA heteroplasmy and ancestry, and found that, although the population heteroplasmy shifts, the heteroplasmy of individual cell lineages remains stable, arguing that selection acts at the level of cell fitness in dividing cells. Using these insights, we show that we can force cells to accumulate high levels of truncating complex I mtDNA heteroplasmy by placing them in environments where loss of biochemical complex I activity has been reported to benefit cell fitness. We conclude that in dividing cells, a given nonsynonymous mtDNA heteroplasmy can be harmful, neutral or even beneficial to cell fitness, but that the 'sign' of the effect is wholly dependent on the environment.


Asunto(s)
División Celular , Linaje de la Célula , ADN Mitocondrial , Aptitud Genética , Heteroplasmia , Selección Genética , Análisis de la Célula Individual , Animales , Femenino , Humanos , Ratones , División Celular/genética , Línea Celular , Linaje de la Célula/genética , ADN Mitocondrial/genética , Edición Génica , Heteroplasmia/genética , Mitocondrias/genética , Mutación , Análisis de la Célula Individual/métodos
8.
Cell ; 158(1): 213-25, 2014 Jul 03.
Artículo en Inglés | MEDLINE | ID: mdl-24995987

RESUMEN

The availability of diverse genomes makes it possible to predict gene function based on shared evolutionary history. This approach can be challenging, however, for pathways whose components do not exhibit a shared history but rather consist of distinct "evolutionary modules." We introduce a computational algorithm, clustering by inferred models of evolution (CLIME), which inputs a eukaryotic species tree, homology matrix, and pathway (gene set) of interest. CLIME partitions the gene set into disjoint evolutionary modules, simultaneously learning the number of modules and a tree-based evolutionary history that defines each module. CLIME then expands each module by scanning the genome for new components that likely arose under the inferred evolutionary model. Application of CLIME to ∼1,000 annotated human pathways and to the proteomes of yeast, red algae, and malaria reveals unanticipated evolutionary modularity and coevolving components. CLIME is freely available and should become increasingly powerful with the growing wealth of eukaryotic genomes.


Asunto(s)
Algoritmos , Análisis por Conglomerados , Filogenia , Humanos , Mitocondrias/metabolismo , Plasmodium falciparum/genética , Plasmodium falciparum/metabolismo , Proteoma/análisis , Rhodophyta/genética , Rhodophyta/metabolismo , Transducción de Señal , Levaduras/genética , Levaduras/metabolismo
9.
Nature ; 620(7975): 839-848, 2023 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-37587338

RESUMEN

Mitochondrial DNA (mtDNA) is a maternally inherited, high-copy-number genome required for oxidative phosphorylation1. Heteroplasmy refers to the presence of a mixture of mtDNA alleles in an individual and has been associated with disease and ageing. Mechanisms underlying common variation in human heteroplasmy, and the influence of the nuclear genome on this variation, remain insufficiently explored. Here we quantify mtDNA copy number (mtCN) and heteroplasmy using blood-derived whole-genome sequences from 274,832 individuals and perform genome-wide association studies to identify associated nuclear loci. Following blood cell composition correction, we find that mtCN declines linearly with age and is associated with variants at 92 nuclear loci. We observe that nearly everyone harbours heteroplasmic mtDNA variants obeying two principles: (1) heteroplasmic single nucleotide variants tend to arise somatically and accumulate sharply after the age of 70 years, whereas (2) heteroplasmic indels are maternally inherited as mixtures with relative levels associated with 42 nuclear loci involved in mtDNA replication, maintenance and novel pathways. These loci may act by conferring a replicative advantage to certain mtDNA alleles. As an illustrative example, we identify a length variant carried by more than 50% of humans at position chrM:302 within a G-quadruplex previously proposed to mediate mtDNA transcription/replication switching2,3. We find that this variant exerts cis-acting genetic control over mtDNA abundance and is itself associated in-trans with nuclear loci encoding machinery for this regulatory switch. Our study suggests that common variation in the nuclear genome can shape variation in mtCN and heteroplasmy dynamics across the human population.


Asunto(s)
Núcleo Celular , Variaciones en el Número de Copia de ADN , ADN Mitocondrial , Heteroplasmia , Mitocondrias , Anciano , Humanos , Variaciones en el Número de Copia de ADN/genética , ADN Mitocondrial/genética , Estudio de Asociación del Genoma Completo , Heteroplasmia/genética , Mitocondrias/genética , Núcleo Celular/genética , Alelos , Polimorfismo de Nucleótido Simple , Mutación INDEL , G-Cuádruplex
10.
Mol Cell ; 81(9): 1905-1919.e12, 2021 05 06.
Artículo en Inglés | MEDLINE | ID: mdl-33852893

RESUMEN

Oxidative phosphorylation (OXPHOS) and glycolysis are the two major pathways for ATP production. The reliance on each varies across tissues and cell states, and can influence susceptibility to disease. At present, the full set of molecular mechanisms governing the relative expression and balance of these two pathways is unknown. Here, we focus on genes whose loss leads to an increase in OXPHOS activity. Unexpectedly, this class of genes is enriched for components of the pre-mRNA splicing machinery, in particular for subunits of the U1 snRNP. Among them, we show that LUC7L2 represses OXPHOS and promotes glycolysis by multiple mechanisms, including (1) splicing of the glycolytic enzyme PFKM to suppress glycogen synthesis, (2) splicing of the cystine/glutamate antiporter SLC7A11 (xCT) to suppress glutamate oxidation, and (3) secondary repression of mitochondrial respiratory supercomplex formation. Our results connect LUC7L2 expression and, more generally, the U1 snRNP to cellular energy metabolism.


Asunto(s)
Glucólisis , Fosforilación Oxidativa , Precursores del ARN/metabolismo , Empalme del ARN , ARN Mensajero/metabolismo , Proteínas de Unión al ARN/metabolismo , Ribonucleoproteína Nuclear Pequeña U1/metabolismo , Sistema de Transporte de Aminoácidos y+/genética , Sistema de Transporte de Aminoácidos y+/metabolismo , Proteínas del Complejo de Cadena de Transporte de Electrón/genética , Proteínas del Complejo de Cadena de Transporte de Electrón/metabolismo , Regulación de la Expresión Génica , Estudio de Asociación del Genoma Completo , Ácido Glutámico/metabolismo , Glucógeno/metabolismo , Glucólisis/genética , Células HEK293 , Células HeLa , Humanos , Células K562 , Mitocondrias/genética , Mitocondrias/metabolismo , Oxidación-Reducción , Fosfofructoquinasa-1 Tipo Muscular/genética , Fosfofructoquinasa-1 Tipo Muscular/metabolismo , Precursores del ARN/genética , ARN Mensajero/genética , Proteínas de Unión al ARN/genética , Ribonucleoproteína Nuclear Pequeña U1/genética
11.
Cell ; 155(1): 21-6, 2013 Sep 26.
Artículo en Inglés | MEDLINE | ID: mdl-24074858

RESUMEN

Technologies for genome-wide sequence interrogation have dramatically improved our ability to identify loci associated with complex human disease. However, a chasm remains between correlations and causality that stems, in part, from a limiting theoretical framework derived from Mendelian genetics and an incomplete understanding of disease physiology. Here we propose a set of criteria, akin to Koch's postulates for infectious disease, for assigning causality between genetic variants and human disease phenotypes.


Asunto(s)
Enfermedad/genética , Genómica/métodos , Fenotipo , Esclerosis Amiotrófica Lateral/genética , Esclerosis Amiotrófica Lateral/fisiopatología , Animales , Causalidad , Variación Genética , Humanos , Herencia Multifactorial
12.
Nat Rev Mol Cell Biol ; 16(9): 545-53, 2015 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-26285678

RESUMEN

The mitochondrial calcium uniporter is an evolutionarily conserved calcium channel, and its biophysical properties and relevance to cell death, bioenergetics and signalling have been investigated for decades. However, the genes encoding this channel have only recently been discovered, opening up a new 'molecular era' in the study of its biology. We now know that the uniporter is not a single protein but rather a macromolecular complex consisting of pore-forming and regulatory subunits. We review recent studies that harnessed the power of molecular biology and genetics to characterize the mechanism of action of the uniporter, its evolution and its contribution to physiology and human disease.


Asunto(s)
Canales de Calcio/fisiología , Animales , Canales de Calcio/química , Señalización del Calcio , Retroalimentación Fisiológica , Humanos , Modelos Moleculares
13.
Cell ; 151(1): 96-110, 2012 Sep 28.
Artículo en Inglés | MEDLINE | ID: mdl-23021218

RESUMEN

PGC1α is a key transcriptional coregulator of oxidative metabolism and thermogenesis. Through a high-throughput chemical screen, we found that molecules antagonizing the TRPVs (transient receptor potential vanilloid), a family of ion channels, induced PGC1α expression in adipocytes. In particular, TRPV4 negatively regulated the expression of PGC1α, UCP1, and cellular respiration. Additionally, it potently controlled the expression of multiple proinflammatory genes involved in the development of insulin resistance. Mice with a null mutation for TRPV4 or wild-type mice treated with a TRPV4 antagonist showed elevated thermogenesis in adipose tissues and were protected from diet-induced obesity, adipose inflammation, and insulin resistance. This role of TRPV4 as a cell-autonomous mediator for both the thermogenic and proinflammatory programs in adipocytes could offer a target for treating obesity and related metabolic diseases.


Asunto(s)
Metabolismo Energético , Canales Catiónicos TRPV/metabolismo , Termogénesis , Adipocitos/metabolismo , Tejido Adiposo Pardo/metabolismo , Tejido Adiposo Blanco/metabolismo , Animales , Femenino , Técnicas de Silenciamiento del Gen , Canales Iónicos/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Proteínas Mitocondriales/metabolismo , Obesidad/metabolismo , Coactivador 1-alfa del Receptor Activado por Proliferadores de Peroxisomas gamma , Canales Catiónicos TRPV/antagonistas & inhibidores , Canales Catiónicos TRPV/genética , Transactivadores/metabolismo , Factores de Transcripción , Proteína Desacopladora 1
14.
PLoS Biol ; 21(5): e3002117, 2023 05.
Artículo en Inglés | MEDLINE | ID: mdl-37220109

RESUMEN

There is widespread interest in identifying interventions that extend healthy lifespan. Chronic continuous hypoxia delays the onset of replicative senescence in cultured cells and extends lifespan in yeast, nematodes, and fruit flies. Here, we asked whether chronic continuous hypoxia is beneficial in mammalian aging. We utilized the Ercc1 Δ/- mouse model of accelerated aging given that these mice are born developmentally normal but exhibit anatomic, physiological, and biochemical features of aging across multiple organs. Importantly, they exhibit a shortened lifespan that is extended by dietary restriction, the most potent aging intervention across many organisms. We report that chronic continuous 11% oxygen commenced at 4 weeks of age extends lifespan by 50% and delays the onset of neurological debility in Ercc1 Δ/- mice. Chronic continuous hypoxia did not impact food intake and did not significantly affect markers of DNA damage or senescence, suggesting that hypoxia did not simply alleviate the proximal effects of the Ercc1 mutation, but rather acted downstream via unknown mechanisms. To the best of our knowledge, this is the first study to demonstrate that "oxygen restriction" can extend lifespan in a mammalian model of aging.


Asunto(s)
Longevidad , Fenómenos Fisiológicos del Sistema Nervioso , Animales , Ratones , Envejecimiento , Hipoxia , Oxígeno , Modelos Animales de Enfermedad , Drosophila , Saccharomyces cerevisiae , Mamíferos
15.
Nature ; 583(7817): 631-637, 2020 07.
Artículo en Inglés | MEDLINE | ID: mdl-32641830

RESUMEN

Bacterial toxins represent a vast reservoir of biochemical diversity that can be repurposed for biomedical applications. Such proteins include a group of predicted interbacterial toxins of the deaminase superfamily, members of which have found application in gene-editing techniques1,2. Because previously described cytidine deaminases operate on single-stranded nucleic acids3, their use in base editing requires the unwinding of double-stranded DNA (dsDNA)-for example by a CRISPR-Cas9 system. Base editing within mitochondrial DNA (mtDNA), however, has thus far been hindered by challenges associated with the delivery of guide RNA into the mitochondria4. As a consequence, manipulation of mtDNA to date has been limited to the targeted destruction of the mitochondrial genome by designer nucleases9,10.Here we describe an interbacterial toxin, which we name DddA, that catalyses the deamination of cytidines within dsDNA. We engineered split-DddA halves that are non-toxic and inactive until brought together on target DNA by adjacently bound programmable DNA-binding proteins. Fusions of the split-DddA halves, transcription activator-like effector array proteins, and a uracil glycosylase inhibitor resulted in RNA-free DddA-derived cytosine base editors (DdCBEs) that catalyse C•G-to-T•A conversions in human mtDNA with high target specificity and product purity. We used DdCBEs to model a disease-associated mtDNA mutation in human cells, resulting in changes in respiration rates and oxidative phosphorylation. CRISPR-free DdCBEs enable the precise manipulation of mtDNA, rather than the elimination of mtDNA copies that results from its cleavage by targeted nucleases, with broad implications for the study and potential treatment of mitochondrial disorders.


Asunto(s)
Toxinas Bacterianas/metabolismo , Citidina Desaminasa/metabolismo , ADN Mitocondrial/genética , Edición Génica/métodos , Genes Mitocondriales/genética , Mitocondrias/genética , Toxinas Bacterianas/química , Toxinas Bacterianas/genética , Secuencia de Bases , Burkholderia cenocepacia/enzimología , Burkholderia cenocepacia/genética , Respiración de la Célula/genética , Citidina/metabolismo , Citidina Desaminasa/química , Citidina Desaminasa/genética , Genoma Mitocondrial/genética , Células HEK293 , Humanos , Enfermedades Mitocondriales/genética , Enfermedades Mitocondriales/terapia , Mutación , Fosforilación Oxidativa , Ingeniería de Proteínas , ARN Guía de Kinetoplastida/genética , Especificidad por Sustrato , Sistemas de Secreción Tipo VI/metabolismo
16.
Nature ; 583(7814): 122-126, 2020 07.
Artículo en Inglés | MEDLINE | ID: mdl-32461692

RESUMEN

The cellular NADH/NAD+ ratio is fundamental to biochemistry, but the extent to which it reflects versus drives metabolic physiology in vivo is poorly understood. Here we report the in vivo application of Lactobacillus brevis (Lb)NOX1, a bacterial water-forming NADH oxidase, to assess the metabolic consequences of directly lowering the hepatic cytosolic NADH/NAD+ ratio in mice. By combining this genetic tool with metabolomics, we identify circulating α-hydroxybutyrate levels as a robust marker of an elevated hepatic cytosolic NADH/NAD+ ratio, also known as reductive stress. In humans, elevations in circulating α-hydroxybutyrate levels have previously been associated with impaired glucose tolerance2, insulin resistance3 and mitochondrial disease4, and are associated with a common genetic variant in GCKR5, which has previously been associated with many seemingly disparate metabolic traits. Using LbNOX, we demonstrate that NADH reductive stress mediates the effects of GCKR variation on many metabolic traits, including circulating triglyceride levels, glucose tolerance and FGF21 levels. Our work identifies an elevated hepatic NADH/NAD+ ratio as a latent metabolic parameter that is shaped by human genetic variation and contributes causally to key metabolic traits and diseases. Moreover, it underscores the utility of genetic tools such as LbNOX to empower studies of 'causal metabolism'.


Asunto(s)
Hígado/metabolismo , NAD/metabolismo , Estrés Fisiológico , Proteínas Adaptadoras Transductoras de Señales/genética , Animales , Citosol/metabolismo , Modelos Animales de Enfermedad , Factores de Crecimiento de Fibroblastos/sangre , Variación Genética , Prueba de Tolerancia a la Glucosa , Humanos , Resistencia a la Insulina , Levilactobacillus brevis/enzimología , Levilactobacillus brevis/genética , Masculino , Ratones , Complejos Multienzimáticos/genética , Complejos Multienzimáticos/metabolismo , NADH NADPH Oxidorreductasas/genética , NADH NADPH Oxidorreductasas/metabolismo , Oxidación-Reducción , Triglicéridos/sangre
17.
J Biol Chem ; 300(9): 107662, 2024 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-39128713

RESUMEN

Propionic acid links the oxidation of branched-chain amino acids and odd-chain fatty acids to the TCA cycle. Gut microbes ferment complex fiber remnants, generating high concentrations of short chain fatty acids, acetate, propionate and butyrate, which are shared with the host as fuel sources. Analysis of vitamin B12-dependent propionate utilization in skin biopsy samples has been used to characterize and diagnose underlying inborn errors of cobalamin (or B12) metabolism. In these cells, the B12-dependent enzyme, methylmalonyl-CoA mutase (MMUT), plays a central role in funneling propionate to the TCA cycle intermediate, succinate. Our understanding of the fate of propionate in other cell types, specifically, the involvement of the ß-oxidation-like and methylcitrate pathways, is limited. In this study, we have used [14C]-propionate tracing in combination with genetic ablation or inhibition of MMUT, to reveal the differential utilization of the B12-dependent and independent pathways for propionate metabolism in fibroblast versus colon cell lines. We demonstrate that itaconate can be used as a tool to investigate MMUT-dependent propionate metabolism in cultured cell lines. While MMUT gates the entry of propionate carbons into the TCA cycle in fibroblasts, colon-derived cell lines exhibit a quantitatively significant or exclusive reliance on the ß-oxidation-like pathway. Lipidomics and metabolomics analyses reveal that propionate elicits pleiotropic changes, including an increase in odd-chain glycerophospholipids, and perturbations in the purine nucleotide cycle and arginine/nitric oxide metabolism. The metabolic rationale and the regulatory mechanisms underlying the differential reliance on propionate utilization pathways at a cellular, and possibly tissue level, warrant further elucidation.


Asunto(s)
Metilmalonil-CoA Mutasa , Propionatos , Vitamina B 12 , Humanos , Propionatos/metabolismo , Propionatos/farmacología , Vitamina B 12/metabolismo , Metilmalonil-CoA Mutasa/metabolismo , Metilmalonil-CoA Mutasa/genética , Ciclo del Ácido Cítrico , Fibroblastos/metabolismo , Colon/metabolismo
18.
Hum Mol Genet ; 32(16): 2600-2610, 2023 08 07.
Artículo en Inglés | MEDLINE | ID: mdl-37260376

RESUMEN

Friedreich's ataxia (FA) is a devastating, multi-systemic neurodegenerative disease affecting thousands of people worldwide. We previously reported that oxygen is a key environmental variable that can modify FA pathogenesis. In particular, we showed that chronic, continuous normobaric hypoxia (11% FIO2) prevents ataxia and neurological disease in a murine model of FA, although it did not improve cardiovascular pathology or lifespan. Here, we report the pre-clinical evaluation of seven 'hypoxia-inspired' regimens in the shFxn mouse model of FA, with the long-term goal of designing a safe, practical and effective regimen for clinical translation. We report three chief results. First, a daily, intermittent hypoxia regimen (16 h 11% O2/8 h 21% O2) conferred no benefit and was in fact harmful, resulting in elevated cardiac stress and accelerated mortality. The detrimental effect of this regimen is likely owing to transient tissue hyperoxia that results when daily exposure to 21% O2 combines with chronic polycythemia, as we could blunt this toxicity by pharmacologically inhibiting polycythemia. Second, we report that more mild regimens of chronic hypoxia (17% O2) confer a modest benefit by delaying the onset of ataxia. Third, excitingly, we show that initiating chronic, continuous 11% O2 breathing once advanced neurological disease has already started can rapidly reverse ataxia. Our studies showcase both the promise and limitations of candidate hypoxia-inspired regimens for FA and underscore the need for additional pre-clinical optimization before future translation into humans.


Asunto(s)
Ataxia de Friedreich , Enfermedades Neurodegenerativas , Policitemia , Humanos , Ratones , Animales , Ataxia de Friedreich/genética , Modelos Animales de Enfermedad , Hipoxia , Oxígeno , Ataxia
19.
Hum Mol Genet ; 32(15): 2441-2454, 2023 07 20.
Artículo en Inglés | MEDLINE | ID: mdl-37133451

RESUMEN

MRPL39 encodes one of 52 proteins comprising the large subunit of the mitochondrial ribosome (mitoribosome). In conjunction with 30 proteins in the small subunit, the mitoribosome synthesizes the 13 subunits of the mitochondrial oxidative phosphorylation (OXPHOS) system encoded by mitochondrial Deoxyribonucleic acid (DNA). We used multi-omics and gene matching to identify three unrelated individuals with biallelic variants in MRPL39 presenting with multisystem diseases with severity ranging from lethal, infantile-onset (Leigh syndrome spectrum) to milder with survival into adulthood. Clinical exome sequencing of known disease genes failed to diagnose these patients; however quantitative proteomics identified a specific decrease in the abundance of large but not small mitoribosomal subunits in fibroblasts from the two patients with severe phenotype. Re-analysis of exome sequencing led to the identification of candidate single heterozygous variants in mitoribosomal genes MRPL39 (both patients) and MRPL15. Genome sequencing identified a shared deep intronic MRPL39 variant predicted to generate a cryptic exon, with transcriptomics and targeted studies providing further functional evidence for causation. The patient with the milder disease was homozygous for a missense variant identified through trio exome sequencing. Our study highlights the utility of quantitative proteomics in detecting protein signatures and in characterizing gene-disease associations in exome-unsolved patients. We describe Relative Complex Abundance analysis of proteomics data, a sensitive method that can identify defects in OXPHOS disorders to a similar or greater sensitivity to the traditional enzymology. Relative Complex Abundance has potential utility for functional validation or prioritization in many hundreds of inherited rare diseases where protein complex assembly is disrupted.


Asunto(s)
Enfermedad de Leigh , Enfermedades Mitocondriales , Humanos , ADN Mitocondrial/genética , Enfermedad de Leigh/genética , Enfermedad de Leigh/patología , Mitocondrias/genética , Mitocondrias/patología , Enfermedades Mitocondriales/patología , Proteínas Mitocondriales/genética , Multiómica , Mutación , Proteínas Ribosómicas/genética
20.
N Engl J Med ; 387(15): 1395-1403, 2022 10 13.
Artículo en Inglés | MEDLINE | ID: mdl-36239646

RESUMEN

We describe the case of identical twin boys who presented with low body weight despite excessive caloric intake. An evaluation of their fibroblasts showed elevated oxygen consumption and decreased mitochondrial membrane potential. Exome analysis revealed a de novo heterozygous variant in ATP5F1B, which encodes the ß subunit of mitochondrial ATP synthase (also called complex V). In yeast, mutations affecting the same region loosen coupling between the proton motive force and ATP synthesis, resulting in high rates of mitochondrial respiration. Expression of the mutant allele in human cell lines recapitulates this phenotype. These data support an autosomal dominant mitochondrial uncoupling syndrome with hypermetabolism. (Funded by the National Institutes of Health.).


Asunto(s)
Enfermedades Mitocondriales , ATPasas de Translocación de Protón Mitocondriales , Fosforilación Oxidativa , Consumo de Oxígeno , Humanos , Masculino , Adenosina Trifosfato/metabolismo , Enfermedades en Gemelos/genética , Enfermedades en Gemelos/metabolismo , Fibroblastos/metabolismo , Mitocondrias/metabolismo , Enfermedades Mitocondriales/congénito , Enfermedades Mitocondriales/genética , Enfermedades Mitocondriales/metabolismo , ATPasas de Translocación de Protón Mitocondriales/genética , ATPasas de Translocación de Protón Mitocondriales/metabolismo , Mutación , Consumo de Oxígeno/genética , Consumo de Oxígeno/fisiología , Gemelos Monocigóticos/genética
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