RESUMO
The present work delves into the enigmatic world of mitochondrial alpha-keto acid dehydrogenase complexes discussing their metabolic significance, enzymatic operation, moonlighting activities, and pathological relevance with links to underlying structural features. This ubiquitous family of related but diverse multienzyme complexes is involved in carbohydrate metabolism (pyruvate dehydrogenase complex), the citric acid cycle (α-ketoglutarate dehydrogenase complex), and amino acid catabolism (branched-chain α-keto acid dehydrogenase complex, α-ketoadipate dehydrogenase complex); the complexes all function at strategic points and also participate in regulation in these metabolic pathways. These systems are among the largest multienzyme complexes with at times more than 100 protein chains and weights ranging up to ~10 million Daltons. Our chapter offers a wealth of up-to-date information on these multienzyme complexes for a comprehensive understanding of their significance in health and disease.
Assuntos
Mitocôndrias , Humanos , Mitocôndrias/metabolismo , Mitocôndrias/enzimologia , Animais , Ciclo do Ácido Cítrico/fisiologia , Complexo Cetoglutarato Desidrogenase/metabolismo , Complexo Cetoglutarato Desidrogenase/químicaRESUMO
Increasing evidence has shown that homologous recombination (HR) and metabolic reprogramming are essential for cellular homeostasis. These two processes are independent as well as closely intertwined. Nevertheless, they have rarely been reported in lung adenocarcinoma (LUAD). We analysed the genomic, immune microenvironment and metabolic microenvironment features under different HR activity states. Using cell cycle, EDU and cell invasion assays, we determined the impacts of si-SHFM1 on the LUAD cell cycle, proliferation and invasion. The levels of isocitrate dehydrogenase (IDH) and α-ketoglutarate dehydrogenase (α-KGDH) were determined by ELISA in the NC and si-SHFM1 groups of A549 cells. Finally, cell samples were used to extract metabolites for HPIC-MS/MS to analyse central carbon metabolism. We found that high HR activity was associated with a poor prognosis in LUAD, and HR was an independent prognostic factor for TCGA-LUAD patients. Moreover, LUAD samples with a high HR activity presented low immune infiltration levels, a high degree of genomic instability, a good response status to immune checkpoint blockade therapy and a high degree of drug sensitivity. The si-SHFM1 group presented a significantly higher proportion of cells in the G0/G1 phase, lower levels of DNA replication, and significantly lower levels of cell migration and both TCA enzymes. Our current results indicated that there is a strong correlation between HR and the TCA cycle in LUAD. The TCA cycle can promote SHFM1-mediated HR in LUAD, raising their activities, which can finally result in a poor prognosis and impair immunotherapeutic efficacy.
Assuntos
Adenocarcinoma de Pulmão , Ciclo do Ácido Cítrico , Recombinação Homóloga , Neoplasias Pulmonares , Feminino , Humanos , Masculino , Células A549 , Adenocarcinoma de Pulmão/genética , Adenocarcinoma de Pulmão/patologia , Adenocarcinoma de Pulmão/metabolismo , Ciclo Celular/genética , Linhagem Celular Tumoral , Movimento Celular , Proliferação de Células , Reprogramação Celular/genética , Regulação Neoplásica da Expressão Gênica , Isocitrato Desidrogenase/genética , Isocitrato Desidrogenase/metabolismo , Complexo Cetoglutarato Desidrogenase/metabolismo , Complexo Cetoglutarato Desidrogenase/genética , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/patologia , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/mortalidade , Reprogramação Metabólica , Prognóstico , Microambiente Tumoral , Pessoa de Meia-Idade , IdosoRESUMO
BACKGROUND: The MRPS36 gene encodes a recently identified component of the 2-oxoglutarate dehydrogenase complex (OGDHC), a key enzyme of the Krebs cycle catalyzing the oxidative decarboxylation of 2-oxoglutarate to succinyl-CoA. Defective OGDHC activity causes a clinically variable metabolic disorder characterized by global developmental delay, severe neurological impairment, liver failure, and early-onset lactic acidosis. METHODS: We investigated the molecular cause underlying Leigh syndrome with bilateral striatal necrosis in two siblings through exome sequencing. Functional studies included measurement of the OGDHC enzymatic activity and MRPS36 mRNA levels in fibroblasts, assessment of protein stability in transfected cells, and structural analysis. A literature review was performed to define the etiological and phenotypic spectrum of OGDHC deficiency. RESULTS: In the two affected brothers, exome sequencing identified a homozygous nonsense variant (c.283G>T, p.Glu95*) of MRPS36. The variant did not affect transcript processing and stability, nor protein levels, but resulted in a shorter protein lacking nine residues that contribute to the structural and functional organization of the OGDHC complex. OGDHC enzymatic activity was significantly reduced. The review of previously reported cases of OGDHC deficiency supports the association of this enzymatic defect with Leigh phenotypic spectrum and early-onset movement disorder. Slightly elevated plasma levels of glutamate and glutamine were observed in our and literature patients with OGDHC defect. CONCLUSIONS: Our findings point to MRPS36 as a new disease gene implicated in Leigh syndrome. The slight elevation of plasma levels of glutamate and glutamine observed in patients with OGDHC deficiency represents a candidate metabolic signature of this neurometabolic disorder. © 2024 International Parkinson and Movement Disorder Society.
Assuntos
Complexo Cetoglutarato Desidrogenase , Doença de Leigh , Doença de Leigh/genética , Humanos , Masculino , Complexo Cetoglutarato Desidrogenase/genética , Complexo Cetoglutarato Desidrogenase/deficiência , Proteínas Mitocondriais/genética , Pré-Escolar , LactenteRESUMO
In the present study, we examined the mitochondrial hydrogen peroxide (mH2O2) generating capacity of α-ketoglutarate dehydrogenase (KGDH) and compared it to components of the electron transport chain using liver mitochondria isolated from male and female C57BL6N mice. We show for the first time there are some sex dimorphisms in the production of mH2O2 by electron transport chain complexes I and III when mitochondria are fueled with different substrates. However, in our investigations into these sex effects, we made the unexpected and compelling discovery that 1) KGDH serves as a major mH2O2 supplier in male and female liver mitochondria and 2) KGDH can form mH2O2 when liver mitochondria are energized with fatty acids but only when malate is used to prime the Krebs cycle. Surprisingly, 2-keto-3-methylvaleric acid (KMV), a site-specific inhibitor for KGDH, nearly abolished mH2O2 generation in both male and female liver mitochondria oxidizing palmitoyl-carnitine. KMV inhibited mH2O2 production in liver mitochondria from male and female mice oxidizing myristoyl-, octanoyl-, or butyryl-carnitine as well. S1QEL 1.1 (S1) and S3QEL 2 (S3), compounds that inhibit reactive oxygen species generation by complexes I and III, respectively, without interfering with OxPhos and respiration, had a negligible effect on the rate of mH2O2 production when pyruvate or acyl-carnitines were used as fuels. However, inclusion of KMV in reaction mixtures containing S1 and/or S3 almost abolished mH2O2 generation. Together, our findings suggest KGDH is the main mH2O2 generator in liver mitochondria, even when fatty acids are used as fuel.
Assuntos
Ácidos Graxos , Peróxido de Hidrogênio , Complexo Cetoglutarato Desidrogenase , Mitocôndrias Hepáticas , Animais , Feminino , Masculino , Camundongos , Complexo I de Transporte de Elétrons/metabolismo , Complexo III da Cadeia de Transporte de Elétrons/metabolismo , Ácidos Graxos/metabolismo , Peróxido de Hidrogênio/metabolismo , Complexo Cetoglutarato Desidrogenase/metabolismo , Camundongos Endogâmicos C57BL , Mitocôndrias Hepáticas/metabolismo , OxirreduçãoRESUMO
Glioblastoma (GBM) remains an incurable disease, requiring more effective therapies. Through interrogation of publicly available CRISPR and RNAi library screens, we identified the α-ketoglutarate dehydrogenase (OGDH) gene, which encodes an enzyme that is part of the tricarboxylic acid (TCA) cycle, as essential for GBM growth. Moreover, by combining transcriptome and metabolite screening analyses, we discovered that loss of function of OGDH by the clinically validated drug compound CPI-613 was synthetically lethal with Bcl-xL inhibition (genetically and through the clinically validated BH3 mimetic, ABT263) in patient-derived xenografts as well neurosphere GBM cultures. CPI-613-mediated energy deprivation drove an integrated stress response with an upregulation of the BH3-only domain protein, Noxa, in an ATF4-dependent manner, as demonstrated by genetic loss-of-function experiments. Consistently, silencing of Noxa attenuated cell death induced by CPI-613 in model systems of GBM. In patient-derived xenograft models of GBM in mice, the combination treatment of ABT263 and CPI-613 suppressed tumor growth and extended animal survival more potently than each compound on its own. Therefore, combined inhibition of Bcl-xL along with disruption of the TCA cycle might be a treatment strategy for GBM.
Assuntos
Compostos de Anilina , Caprilatos , Glioblastoma , Complexo Cetoglutarato Desidrogenase , Sulfetos , Sulfonamidas , Mutações Sintéticas Letais , Ensaios Antitumorais Modelo de Xenoenxerto , Proteína bcl-X , Animais , Humanos , Camundongos , Fator 4 Ativador da Transcrição/metabolismo , Fator 4 Ativador da Transcrição/genética , Compostos de Anilina/farmacologia , Proteína bcl-X/metabolismo , Proteína bcl-X/genética , Neoplasias Encefálicas/patologia , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/genética , Neoplasias Encefálicas/tratamento farmacológico , Linhagem Celular Tumoral , Ciclo do Ácido Cítrico/efeitos dos fármacos , Glioblastoma/patologia , Glioblastoma/genética , Glioblastoma/metabolismo , Glioblastoma/tratamento farmacológico , Complexo Cetoglutarato Desidrogenase/metabolismo , Complexo Cetoglutarato Desidrogenase/genética , Complexo Cetoglutarato Desidrogenase/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/genética , Sulfonamidas/farmacologiaRESUMO
In the present study, cryo-electron tomography was used to investigate the localization of 2-oxoacid dehydrogenase complexes (OADCs) in cardiac mitochondria and mitochondrial inner membrane samples. Two classes of ordered OADC inner cores with different symmetries were distinguished and their quaternary structures modeled. One class corresponds to pyruvate dehydrogenase complexes and the other to dehydrogenase complexes of α-ketoglutarate and branched-chain α-ketoacids. OADCs were shown to be localized in close proximity to membrane-embedded respirasomes, as observed both in densely packed lamellar cristae of cardiac mitochondria and in ruptured mitochondrial samples where the dense packing is absent. This suggests the specificity of the OADC-respirasome interaction, which allows localized NADH/NAD+ exchange between OADCs and complex I of the respiratory chain. The importance of this local coupling is based on OADCs being the link between respiration, glycolysis and amino acid metabolism. The coupling of these basic metabolic processes can vary in different tissues and conditions and may be involved in the development of various pathologies. The present study shows that this important and previously missing parameter of mitochondrial complex coupling can be successfully assessed using cryo-electron tomography.
Assuntos
Cetoácidos , Complexo Piruvato Desidrogenase , 3-Metil-2-Oxobutanoato Desidrogenase (Lipoamida) , Complexo Piruvato Desidrogenase/metabolismo , Mitocôndrias Cardíacas/metabolismo , Ácidos Cetoglutáricos , Complexo Cetoglutarato Desidrogenase/metabolismoRESUMO
DHTKD1 is a nuclear gene that encodes "dehydrogenase E1 and transketolase domain-containing 1", essential in mitochondrial metabolism. First identified in the patients of 2-amino-apidic and 2 oxoapidic aciduria, mutation in this gene has recently been implicated in CMT2Q and ALS. Here we report the case of a septuagenarian who presented with a 2 years progressive history of respiratory and neck muscle weakness without significant bulbar and limb involvement. Clinical and electrophysiological examination revealed lower motor neuron involvement with widespread chronic denervation and reinnervation. Clinical exome sequencing revealed a heterozygous nonsense variant in exon 8 of the DHTKD1 gene, which was previously described in CMT2Q. This report highlights the pleotropic phenotypic presentation of DHTKD1 mutation and the need for genetic testing even in sporadic cases of ALS presenting at a later age.
Assuntos
Esclerose Lateral Amiotrófica , Cetona Oxirredutases , Humanos , Cetona Oxirredutases/genética , Cetona Oxirredutases/metabolismo , Complexo Cetoglutarato Desidrogenase/genética , Complexo Cetoglutarato Desidrogenase/metabolismo , Esclerose Lateral Amiotrófica/diagnóstico , Esclerose Lateral Amiotrófica/genética , Esclerose Lateral Amiotrófica/metabolismo , Mutação/genética , MitocôndriasRESUMO
BACKGROUND: Biallelic variants in OGDHL, encoding part of the α-ketoglutarate dehydrogenase complex, have been associated with highly heterogeneous neurological and neurodevelopmental disorders. However, the validity of this association remains to be confirmed. A second OGDHL patient cohort was recruited to carefully assess the gene-disease relationship. METHODS: Using an unbiased genotype-first approach, we screened large, multiethnic aggregated sequencing datasets worldwide for biallelic OGDHL variants. We used CRISPR/Cas9 to generate zebrafish knockouts of ogdhl, ogdh paralogs, and dhtkd1 to investigate functional relationships and impact during development. Functional complementation with patient variant transcripts was conducted to systematically assess protein functionality as a readout for pathogenicity. RESULTS: A cohort of 14 individuals from 12 unrelated families exhibited highly variable clinical phenotypes, with the majority of them presenting at least one additional variant, potentially accounting for a blended phenotype and complicating phenotypic understanding. We also uncovered extreme clinical heterogeneity and high allele frequencies, occasionally incompatible with a fully penetrant recessive disorder. Human cDNA of previously described and new variants were tested in an ogdhl zebrafish knockout model, adding functional evidence for variant reclassification. We disclosed evidence of hypomorphic alleles as well as a loss-of-function variant without deleterious effects in zebrafish variant testing also showing discordant familial segregation, challenging the relationship of OGDHL as a conventional Mendelian gene. Going further, we uncovered evidence for a complex compensatory relationship among OGDH, OGDHL, and DHTKD1 isoenzymes that are associated with neurodevelopmental disorders and exhibit complex transcriptional compensation patterns with partial functional redundancy. CONCLUSIONS: Based on the results of genetic, clinical, and functional studies, we formed three hypotheses in which to frame observations: biallelic OGDHL variants lead to a highly variable monogenic disorder, variants in OGDHL are following a complex pattern of inheritance, or they may not be causative at all. Our study further highlights the continuing challenges of assessing the validity of reported disease-gene associations and effects of variants identified in these genes. This is particularly more complicated in making genetic diagnoses based on identification of variants in genes presenting a highly heterogenous phenotype such as "OGDHL-related disorders".
Assuntos
Proteínas , Peixe-Zebra , Animais , Humanos , Frequência do Gene , Complexo Cetoglutarato Desidrogenase/genética , Complexo Cetoglutarato Desidrogenase/metabolismo , Fenótipo , Proteínas/genética , Peixe-Zebra/genéticaRESUMO
Pyruvate dehydrogenase (PDH) and α-ketoglutarate dehydrogenase (KGDH) are vital entry points for monosaccharides and amino acids into the Krebs cycle and thus integral for mitochondrial bioenergetics. Both complexes produce mitochondrial hydrogen peroxide (mH2O2) and are deactivated by electrophiles. Here, we provide an update on the role of PDH and KGDH in mitochondrial redox balance and their function in facilitating metabolic reprogramming for the propagation of oxidative eustress signals in hepatocytes and how defects in these pathways can cause liver diseases. PDH and KGDH are known to account for â¼45% of the total mH2O2 formed by mitochondria and display rates of production several-fold higher than the canonical source complex I. This mH2O2 can also be formed by reverse electron transfer (RET) in vivo, which has been linked to metabolic dysfunctions that occur in pathogenesis. However, the controlled emission of mH2O2 from PDH and KGDH has been proposed to be fundamental for oxidative eustress signal propagation in several cellular contexts. Modification of PDH and KGDH with protein S-glutathionylation (PSSG) and S-nitrosylation (PSNO) adducts serves as a feedback inhibitor for mH2O2 production in response to glutathione (GSH) pool oxidation. PSSG and PSNO adduct formation also reprogram the Krebs cycle to generate metabolites vital for interorganelle and intercellular signaling. Defects in the redox modification of PDH and KGDH cause the over generation of mH2O2, resulting in oxidative distress and metabolic dysfunction-associated fatty liver disease (MAFLD). In aggregate, PDH and KGDH are essential platforms for emitting and receiving oxidative eustress signals.
Assuntos
Hepatócitos , Peróxido de Hidrogênio , Complexo Cetoglutarato Desidrogenase , Mitocôndrias Hepáticas , Complexo Piruvato Desidrogenase , Peróxido de Hidrogênio/metabolismo , Complexo Cetoglutarato Desidrogenase/química , Complexo Cetoglutarato Desidrogenase/metabolismo , Oxirredução , Estresse Oxidativo , Complexo Piruvato Desidrogenase/química , Complexo Piruvato Desidrogenase/metabolismo , Humanos , Hepatócitos/enzimologia , Mitocôndrias Hepáticas/metabolismo , Hepatopatia Gordurosa não Alcoólica/enzimologia , Animais , CamundongosRESUMO
The NDUFS4 knockout (KO) mouse phenotype resembles the human Complex I deficiency Leigh Syndrome. The irreversible succination of protein thiols by fumarate is increased in select regions of the NDUFS4 KO brain affected by neurodegeneration. We report that dihydrolipoyllysine-residue succinyltransferase (DLST), a component of the α-ketoglutarate dehydrogenase complex (KGDHC) of the tricarboxylic acid (TCA) cycle, is succinated in the affected regions of the NDUFS4 KO brain. Succination of DLST reduced KGDHC activity in the brainstem (BS) and olfactory bulb (OB) of KO mice. The defective production of KGDHC derived succinyl-CoA resulted in decreased mitochondrial substrate level phosphorylation (SLP), further aggravating the existing oxidative phosphorylation (OXPHOS) ATP deficit. Protein succinylation, an acylation modification that requires succinyl-CoA, was reduced in the KO mice. Modeling succination of a cysteine in the spatial vicinity of the DLST active site or introduction of succinomimetic mutations recapitulates these metabolic deficits. Our data demonstrate that the biochemical deficit extends beyond impaired Complex I assembly and OXPHOS deficiency, functionally impairing select components of the TCA cycle to drive metabolic perturbations in affected neurons.
Assuntos
Ciclo do Ácido Cítrico , Complexo Cetoglutarato Desidrogenase , Camundongos , Animais , Humanos , Complexo Cetoglutarato Desidrogenase/genética , Complexo Cetoglutarato Desidrogenase/metabolismo , Mitocôndrias/genética , Mitocôndrias/metabolismo , Camundongos Knockout , Fosforilação Oxidativa , Trifosfato de Adenosina/metabolismoRESUMO
Branched chain α-ketoacid dehydrogenase complex (BCKDC) is the rate-limiting enzyme in branched chain amino acid (BCAA) catabolism, a metabolic pathway with great importance for human health. BCKDC belongs to the mitochondrial α-ketoacid dehydrogenase complex family, which also includes pyruvate dehydrogenase complex and oxoglutarate dehydrogenase complex. Here, we revealed that BCKDC can be substantially inhibited by reactive nitrogen species (RNS) via a mechanism similar to what we recently discovered with pyruvate dehydrogenase complex and oxoglutarate dehydrogenase complex-RNS can cause inactivating covalent modifications of the lipoic arm on its E2 subunit. In addition, we showed that such reaction between RNS and the lipoic arm of the E2 subunit can further promote inhibition of the E3 subunits of α-ketoacid dehydrogenase complexes. We examined the impacts of this RNS-mediated BCKDC inhibition in muscle cells, an important site of BCAA metabolism, and demonstrated that the nitric oxide production induced by cytokine stimulation leads to a strong inhibition of BCKDC activity and BCAA oxidation in myotubes and myoblasts. More broadly, nitric oxide production reduced the level of functional lipoic arms across the multiple α-ketoacid dehydrogenases and led to intracellular accumulation of their substrates (α-ketoacids), decrease of their products (acyl-CoAs), and a lower cellular energy charge. In sum, this work revealed a new mechanism for BCKDC regulation, demonstrated that RNS can generally inhibit all α-ketoacid dehydrogenases, which has broad physiological implications across multiple cell types, and elucidated the mechanistic connection between RNS-driven inhibitory modifications on the E2 and E3 subunits of α-ketoacid dehydrogenases.
Assuntos
3-Metil-2-Oxobutanoato Desidrogenase (Lipoamida) , Células Musculares , Óxido Nítrico , Espécies Reativas de Nitrogênio , Humanos , 3-Metil-2-Oxobutanoato Desidrogenase (Lipoamida)/metabolismo , Aminoácidos de Cadeia Ramificada/metabolismo , Complexo Cetoglutarato Desidrogenase , Células Musculares/metabolismo , Complexo Piruvato Desidrogenase , Espécies Reativas de Nitrogênio/metabolismoRESUMO
Actinobacteria possess unique ways to regulate the oxoglutarate metabolic node. Contrary to most organisms in which three enzymes compose the 2-oxoglutarate dehydrogenase complex (ODH), actinobacteria rely on a two-in-one protein (OdhA) in which both the oxidative decarboxylation and succinyl transferase steps are carried out by the same polypeptide. Here we describe high-resolution cryo-EM and crystallographic snapshots of representative enzymes from Mycobacterium smegmatis and Corynebacterium glutamicum, showing that OdhA is an 800-kDa homohexamer that assembles into a three-blade propeller shape. The obligate trimeric and dimeric states of the acyltransferase and dehydrogenase domains, respectively, are critical for maintaining the overall assembly, where both domains interact via subtle readjustments of their interfaces. Complexes obtained with substrate analogues, reaction products and allosteric regulators illustrate how these domains operate. Furthermore, we provide additional insights into the phosphorylation-dependent regulation of this enzymatic machinery by the signalling protein OdhI.
Assuntos
Corynebacterium glutamicum , Complexo Cetoglutarato Desidrogenase , Complexo Cetoglutarato Desidrogenase/metabolismo , Microscopia Crioeletrônica , Fosforilação , Corynebacterium glutamicum/metabolismoRESUMO
Methylations on nucleosomal histones play fundamental roles in regulating eukaryotic transcription. Jumonji C domain-containing histone demethylases (JMJs) dynamically control the level of histone methylations. However, how JMJ activity is generally regulated is unknown. We found that the tricarboxylic acid cycle-associated enzyme α-ketoglutarate (α-KG) dehydrogenase (KGDH) entered the nucleus, where it interacted with various JMJs to regulate α-KG-dependent histone demethylations by JMJs, and thus controlled genome-wide gene expression in plants. We show that nuclear targeting is regulated by environmental signals and that KGDH is enriched at thousands of loci in Arabidopsis thaliana. Chromatin-bound KGDH catalyzes α-KG decarboxylation and thus may limit its local availability to KGDH-coupled JMJs, inhibiting histone demethylation. Thus, our results uncover a regulatory mechanism for histone demethylations by JMJs.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Histonas , Histona Desmetilases com o Domínio Jumonji , Complexo Cetoglutarato Desidrogenase , Arabidopsis/enzimologia , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Núcleo Celular/enzimologia , Cromatina/metabolismo , Desmetilação , Histona Desmetilases/genética , Histonas/metabolismo , Histona Desmetilases com o Domínio Jumonji/genética , Complexo Cetoglutarato Desidrogenase/genética , Complexo Cetoglutarato Desidrogenase/metabolismo , Regulação da Expressão Gênica de PlantasRESUMO
Light alters histone methylation in plants via nuclear α-ketoglutarate dehydrogenase.
Assuntos
Arabidopsis , Regulação da Expressão Gênica de Plantas , Complexo Cetoglutarato Desidrogenase , Processamento de Proteína Pós-Traducional , Transcrição Gênica , Complexo Cetoglutarato Desidrogenase/genética , Metilação , Arabidopsis/enzimologia , Arabidopsis/genéticaRESUMO
In eukaryotes, pyruvate, a key metabolite produced by glycolysis, is converted by a tripartite mitochondrial pyruvate dehydrogenase (PDH) complex to acetyl-coenzyme A, which is fed into the tricarboxylic acid cycle. Two additional enzyme complexes with analogous composition catalyze similar oxidative decarboxylation reactions albeit using different substrates, the branched-chain ketoacid dehydrogenase (BCKDH) complex and the 2-oxoglutarate dehydrogenase (OGDH) complex. Comparative transcriptome analyses of diplonemids, one of the most abundant and diverse groups of oceanic protists, indicate that the conventional E1, E2, and E3 subunits of the PDH complex are lacking. E1 was apparently replaced in the euglenozoan ancestor of diplonemids by an AceE protein of archaeal type, a substitution that we also document in dinoflagellates. Here, we demonstrate that the mitochondrion of the model diplonemid Paradiplonema papillatum displays pyruvate and 2-oxoglutarate dehydrogenase activities. Protein mass spectrometry of mitochondria reveal that the AceE protein is as abundant as the E1 subunit of BCKDH. This corroborates the view that the AceE subunit is a functional component of the PDH complex. We hypothesize that by acquiring AceE, the diplonemid ancestor not only lost the eukaryotic-type E1, but also the E2 and E3 subunits of the PDH complex, which are present in other euglenozoans. We posit that the PDH activity in diplonemids seems to be carried out by a complex, in which the AceE protein partners with the E2 and E3 subunits from BCKDH and/or OGDH.
Assuntos
Mitocôndrias , Complexo Piruvato Desidrogenase , Mitocôndrias/metabolismo , Complexo Piruvato Desidrogenase/metabolismo , Complexos Multienzimáticos/metabolismo , Complexo Cetoglutarato Desidrogenase/metabolismo , Piruvatos/metabolismoRESUMO
Oxoglutarate dehydrogenase-like (OGDHL) is considered to be the isoenzyme of oxyglutarate dehydrogenase (OGDH) in the OGDH complex, which degrades glucose and glutamate. OGDHL was reported to reprogram glutamine metabolism to suppress HCC progression in an enzyme-activity-dependent manner. However, the potential subcellular localization and non-canonical function of OGDHL is poorly understood. We investigated the expression of OGDHL and its effect on HCC progression. By employing a variety of molecular biology techniques, we revealed the underlying mechanism of OGDHL-induced DNA damage in HCC cells in vitro and in vivo. AAV loaded with OGDHL exerts therapeutic effect on mouse HCC and prolongs survival time. OGDHL induces DNA damage in HCC cells in vitro and in vivo. We also observed that OGDHL possesses nuclear localization in HCC cells and OGDHL-induced DNA damage was independent of its enzymatic activity. Mechanistically, it was demonstrated that OGDHL binds to CDK4 in the nucleus to inhibit the phosphorylation of CDK4 by CAK, which in turn attenuates E2F1 signaling. Inhibition of E2F1 signaling downregulates pyrimidine and purine synthesis, thereby inducing DNA damage through dNTP depletion. We clarified the nuclear localization of OGDHL and its non-canonical function to induce DNA damage, which demonstrated that OGDHL may serve as a select potential therapeutic target for HCC.
Assuntos
Carcinoma Hepatocelular , Neoplasias Hepáticas , Camundongos , Animais , Carcinoma Hepatocelular/patologia , Neoplasias Hepáticas/patologia , Complexo Cetoglutarato Desidrogenase/metabolismo , Transdução de Sinais , Dano ao DNA , Linhagem Celular Tumoral , Proliferação de CélulasRESUMO
Myofibrils are long intracellular cables specific to muscles, composed mainly of actin and myosin filaments. The actin and myosin filaments are organized into repeated units called sarcomeres, which form the myofibrils. Muscle contraction is achieved by the simultaneous shortening of sarcomeres, which requires all sarcomeres to be the same size. Muscles have a variety of ways to ensure sarcomere homogeneity. We have previously shown that the controlled oligomerization of Zasp proteins sets the diameter of the myofibril. Here, we looked for Zasp-binding proteins at the Z-disc to identify additional proteins coordinating myofibril growth and assembly. We found that the E1 subunit of the oxoglutarate dehydrogenase complex localizes to both the Z-disc and the mitochondria, and is recruited to the Z-disc by Zasp52. The three subunits of the oxoglutarate dehydrogenase complex are required for myofibril formation. Using super-resolution microscopy, we revealed the overall organization of the complex at the Z-disc. Metabolomics identified an amino acid imbalance affecting protein synthesis as a possible cause of myofibril defects, which is supported by OGDH-dependent localization of ribosomes at the Z-disc.
Assuntos
Miofibrilas , Sarcômeros , Animais , Miofibrilas/metabolismo , Sarcômeros/metabolismo , Drosophila/metabolismo , Actinas/metabolismo , Miosinas/metabolismo , Complexo Cetoglutarato Desidrogenase/metabolismoRESUMO
The oxoglutarate dehydrogenase complex (OGDHc) participates in the tricarboxylic acid cycle and, in a multi-step reaction, decarboxylates α-ketoglutarate, transfers succinyl to CoA, and reduces NAD+. Due to its pivotal role in metabolism, OGDHc enzymatic components have been studied in isolation; however, their interactions within the endogenous OGDHc remain elusive. Here, we discern the organization of a thermophilic, eukaryotic, native OGDHc in its active state. By combining biochemical, biophysical, and bioinformatic methods, we resolve its composition, 3D architecture, and molecular function at 3.35 Å resolution. We further report the high-resolution cryo-EM structure of the OGDHc core (E2o), which displays various structural adaptations. These include hydrogen bonding patterns confining interactions of OGDHc participating enzymes (E1o-E2o-E3), electrostatic tunneling that drives inter-subunit communication, and the presence of a flexible subunit (E3BPo), connecting E2o and E3. This multi-scale analysis of a succinyl-CoA-producing native cell extract provides a blueprint for structure-function studies of complex mixtures of medical and biotechnological value.