Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 86
Filtrar
Más filtros












Base de datos
Intervalo de año de publicación
1.
Commun Biol ; 7(1): 1045, 2024 Aug 24.
Artículo en Inglés | MEDLINE | ID: mdl-39181993

RESUMEN

The astrocyte-to-neuron lactate shuttle model entails that, upon glutamatergic neurotransmission, glycolytically derived pyruvate in astrocytes is mainly converted to lactate instead of being entirely catabolized in mitochondria. The mechanism of this metabolic rewiring and its occurrence in human brain are unclear. Here by using immunohistochemistry (4 brains) and imaging mass cytometry (8 brains) we show that astrocytes of the adult human neocortex and hippocampal formation express barely detectable amounts of mitochondrial proteins critical for performing oxidative phosphorylation (OXPHOS). These data are corroborated by queries of transcriptomes (107 brains) of neuronal versus non-neuronal cells fetched from the Allen Institute for Brain Science for genes coding for a much larger repertoire of entities contributing to OXPHOS, showing that human non-neuronal elements barely expressed mRNAs coding for such proteins. With less OXPHOS, human brain astrocytes are thus bound to produce more lactate to avoid interruption of glycolysis.


Asunto(s)
Astrocitos , Hipocampo , Mitocondrias , Neocórtex , Fosforilación Oxidativa , Humanos , Astrocitos/metabolismo , Hipocampo/metabolismo , Hipocampo/citología , Neocórtex/metabolismo , Neocórtex/citología , Mitocondrias/metabolismo , Adulto , Masculino , Femenino , Neuronas/metabolismo
2.
Biochem Soc Trans ; 52(2): 529-538, 2024 04 24.
Artículo en Inglés | MEDLINE | ID: mdl-38526218

RESUMEN

Certain cancer cells within solid tumors experience hypoxia, rendering them incapable of oxidative phosphorylation (OXPHOS). Despite this oxygen deficiency, these cells exhibit biochemical pathway activity that relies on NAD+. This mini-review scrutinizes the persistent, residual Complex I activity that oxidizes NADH in the absence of oxygen as the electron acceptor. The resulting NAD+ assumes a pivotal role in fueling the α-ketoglutarate dehydrogenase complex, a critical component in the oxidative decarboxylation branch of glutaminolysis - a hallmark oncometabolic pathway. The proposition is that through glutamine catabolism, high-energy phosphate intermediates are produced via substrate-level phosphorylation in the mitochondrial matrix substantiated by succinyl-CoA ligase, partially compensating for an OXPHOS deficiency. These insights provide a rationale for exploring Complex I inhibitors in cancer treatment, even when OXPHOS functionality is already compromised.


Asunto(s)
Complejo I de Transporte de Electrón , Neoplasias , Animales , Humanos , Complejo I de Transporte de Electrón/metabolismo , Glutamina/metabolismo , Hipoxia/metabolismo , Mitocondrias/metabolismo , NAD/metabolismo , Neoplasias/metabolismo , Fosforilación Oxidativa
3.
Sci Rep ; 14(1): 1729, 2024 01 19.
Artículo en Inglés | MEDLINE | ID: mdl-38242919

RESUMEN

Anoxia halts oxidative phosphorylation (OXPHOS) causing an accumulation of reduced compounds in the mitochondrial matrix which impedes dehydrogenases. By simultaneously measuring oxygen concentration, NADH autofluorescence, mitochondrial membrane potential and ubiquinone reduction extent in isolated mitochondria in real-time, we demonstrate that Complex I utilized endogenous quinones to oxidize NADH under acute anoxia. 13C metabolic tracing or untargeted analysis of metabolites extracted during anoxia in the presence or absence of site-specific inhibitors of the electron transfer system showed that NAD+ regenerated by Complex I is reduced by the 2-oxoglutarate dehydrogenase Complex yielding succinyl-CoA supporting mitochondrial substrate-level phosphorylation (mtSLP), releasing succinate. Complex II operated amphidirectionally during the anoxic event, providing quinones to Complex I and reducing fumarate to succinate. Our results highlight the importance of quinone provision to Complex I oxidizing NADH maintaining glutamate catabolism and mtSLP in the absence of OXPHOS.


Asunto(s)
Mitocondrias , NAD , Humanos , NAD/metabolismo , Mitocondrias/metabolismo , Complejo I de Transporte de Electrón/metabolismo , Quinonas/metabolismo , Fosforilación Oxidativa , Succinatos/metabolismo , Hipoxia/metabolismo , Oxidación-Reducción
4.
Sci Rep ; 13(1): 10822, 2023 07 04.
Artículo en Inglés | MEDLINE | ID: mdl-37402778

RESUMEN

Alterations in metabolism are a hallmark of cancer. It is unclear if oxidative phosphorylation (OXPHOS) is necessary for tumour cell survival. In this study, we investigated the effects of severe hypoxia, site-specific inhibition of respiratory chain (RC) components, and uncouplers on necrotic and apoptotic markers in 2D-cultured HepG2 and MCF-7 tumour cells. Comparable respiratory complex activities were observed in both cell lines. However, HepG2 cells exhibited significantly higher oxygen consumption rates (OCR) and respiratory capacity than MCF-7 cells. Significant non-mitochondrial OCR was observed in MCF-7 cells, which was insensitive to acute combined inhibition of complexes I and III. Pre-treatment of either cell line with RC inhibitors for 24-72 h resulted in the complete abolition of respective complex activities and OCRs. This was accompanied by a time-dependent decrease in citrate synthase activity, suggesting mitophagy. High-content automated microscopy recordings revealed that the viability of HepG2 cells was mostly unaffected by any pharmacological treatment or severe hypoxia. In contrast, the viability of MCF-7 cells was strongly affected by inhibition of complex IV (CIV) or complex V (CV), severe hypoxia, and uncoupling. However, it was only moderately affected by inhibition of complexes I, II, and III. Cell death in MCF-7 cells induced by inhibition of complexes II, III, and IV was partially abrogated by aspartate. These findings indicate that OXPHOS activity and viability are not correlated in these cell lines, suggesting that the connection between OXPHOS and cancer cell survival is dependent on the specific cell type and conditions.


Asunto(s)
Metabolismo Energético , Mitocondrias , Humanos , Células MCF-7 , Mitocondrias/metabolismo , Fosforilación Oxidativa , Complejo I de Transporte de Electrón/metabolismo , Hipoxia/metabolismo
5.
Front Oncol ; 12: 968351, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-36059707

RESUMEN

Glioblastoma (GBM), similar to most cancers, is dependent on fermentation metabolism for the synthesis of biomass and energy (ATP) regardless of the cellular or genetic heterogeneity seen within the tumor. The transition from respiration to fermentation arises from the documented defects in the number, the structure, and the function of mitochondria and mitochondrial-associated membranes in GBM tissue. Glucose and glutamine are the major fermentable fuels that drive GBM growth. The major waste products of GBM cell fermentation (lactic acid, glutamic acid, and succinic acid) will acidify the microenvironment and are largely responsible for drug resistance, enhanced invasion, immunosuppression, and metastasis. Besides surgical debulking, therapies used for GBM management (radiation, chemotherapy, and steroids) enhance microenvironment acidification and, although often providing a time-limited disease control, will thus favor tumor recurrence and complications. The simultaneous restriction of glucose and glutamine, while elevating non-fermentable, anti-inflammatory ketone bodies, can help restore the pH balance of the microenvironment while, at the same time, providing a non-toxic therapeutic strategy for killing most of the neoplastic cells.

6.
Antioxidants (Basel) ; 11(8)2022 Jul 29.
Artículo en Inglés | MEDLINE | ID: mdl-36009207

RESUMEN

α-ketoglutarate dehydrogenase complex (KGDHc), or 2-oxoglutarate dehydrogenase complex (OGDHc) is a rate-limiting enzyme in the tricarboxylic acid cycle, that has been identified in neurodegenerative diseases such as in Alzheimer's disease. The aim of the present study was to establish the role of the KGDHc and its subunits in the bioenergetics and reactive oxygen species (ROS) homeostasis of brain mitochondria. To study the bioenergetic profile of KGDHc, genetically modified mouse strains were used having a heterozygous knock out (KO) either in the dihydrolipoyl succinyltransferase (DLST+/-) or in the dihydrolipoyl dehydrogenase (DLD+/-) subunit. Mitochondrial oxygen consumption, hydrogen peroxide (H2O2) production, and expression of antioxidant enzymes were measured in isolated mouse brain mitochondria. Here, we demonstrate that the ADP-stimulated respiration of mitochondria was partially arrested in the transgenic animals when utilizing α-ketoglutarate (α-KG or 2-OG) as a fuel substrate. Succinate and α-glycerophosphate (α-GP), however, did not show this effect. The H2O2 production in mitochondria energized with α-KG was decreased after inhibiting the adenine nucleotide translocase and Complex I (CI) in the transgenic strains compared to the controls. Similarly, the reverse electron transfer (RET)-evoked H2O2 formation supported by succinate or α-GP were inhibited in mitochondria isolated from the transgenic animals. The decrease of RET-evoked ROS production by DLST+/- or DLD+/- KO-s puts the emphasis of the KGDHc in the pathomechanism of ischemia-reperfusion evoked oxidative stress. Supporting this notion, expression of the antioxidant enzyme glutathione peroxidase was also decreased in the KGDHc transgenic animals suggesting the attenuation of ROS-producing characteristics of KGDHc. These findings confirm the contribution of the KGDHc to the mitochondrial ROS production and in the pathomechanism of ischemia-reperfusion injury.

7.
Int J Mol Sci ; 23(9)2022 May 04.
Artículo en Inglés | MEDLINE | ID: mdl-35563503

RESUMEN

The oxidation of proline to pyrroline-5-carboxylate (P5C) leads to the transfer of electrons to ubiquinone in mitochondria that express proline dehydrogenase (ProDH). This electron transfer supports Complexes CIII and CIV, thus generating the protonmotive force. Further catabolism of P5C forms glutamate, which fuels the citric acid cycle that yields the reducing equivalents that sustain oxidative phosphorylation. However, P5C and glutamate catabolism depend on CI activity due to NAD+ requirements. NextGen-O2k (Oroboros Instruments) was used to measure proline oxidation in isolated mitochondria of various mouse tissues. Simultaneous measurements of oxygen consumption, membrane potential, NADH, and the ubiquinone redox state were correlated to ProDH activity and F1FO-ATPase directionality. Proline catabolism generated a sufficiently high membrane potential that was able to maintain the F1FO-ATPase operation in the forward mode. This was observed in CI-inhibited mouse liver and kidney mitochondria that exhibited high levels of proline oxidation and ProDH activity. This action was not observed under anoxia or when either CIII or CIV were inhibited. The duroquinone fueling of CIII and CIV partially reproduced the effects of proline. Excess glutamate, however, could not reproduce the proline effect, suggesting that processes upstream of the glutamate conversion from proline were involved. The ProDH inhibitors tetrahydro-2-furoic acid and, to a lesser extent, S-5-oxo-2-tetrahydrofurancarboxylic acid abolished all proline effects. The data show that ProDH-directed proline catabolism could generate sufficient CIII and CIV proton pumping, thus supporting ATP production by the F1FO-ATPase even under CI inhibition.


Asunto(s)
Prolina Oxidasa , Ubiquinona , Adenosina Trifosfatasas/metabolismo , Adenosina Trifosfato/metabolismo , Animales , Complejo I de Transporte de Electrón/metabolismo , Ácido Glutámico/metabolismo , Ratones , Mitocondrias/metabolismo , Prolina/metabolismo , Prolina Oxidasa/metabolismo , Ubiquinona/metabolismo
8.
Metabolites ; 11(9)2021 Aug 25.
Artículo en Inglés | MEDLINE | ID: mdl-34564387

RESUMEN

A theory that can best explain the facts of a phenomenon is more likely to advance knowledge than a theory that is less able to explain the facts. Cancer is generally considered a genetic disease based on the somatic mutation theory (SMT) where mutations in proto-oncogenes and tumor suppressor genes cause dysregulated cell growth. Evidence is reviewed showing that the mitochondrial metabolic theory (MMT) can better account for the hallmarks of cancer than can the SMT. Proliferating cancer cells cannot survive or grow without carbons and nitrogen for the synthesis of metabolites and ATP (Adenosine Triphosphate). Glucose carbons are essential for metabolite synthesis through the glycolysis and pentose phosphate pathways while glutamine nitrogen and carbons are essential for the synthesis of nitrogen-containing metabolites and ATP through the glutaminolysis pathway. Glutamine-dependent mitochondrial substrate level phosphorylation becomes essential for ATP synthesis in cancer cells that over-express the glycolytic pyruvate kinase M2 isoform (PKM2), that have deficient OxPhos, and that can grow in either hypoxia (0.1% oxygen) or in cyanide. The simultaneous targeting of glucose and glutamine, while elevating levels of non-fermentable ketone bodies, offers a simple and parsimonious therapeutic strategy for managing most cancers.

9.
Int J Mol Sci ; 22(11)2021 Jun 04.
Artículo en Inglés | MEDLINE | ID: mdl-34199982

RESUMEN

Lysine succinylation is a post-translational modification which alters protein function in both physiological and pathological processes. Mindful that it requires succinyl-CoA, a metabolite formed within the mitochondrial matrix that cannot permeate the inner mitochondrial membrane, the question arises as to how there can be succinylation of proteins outside mitochondria. The present mini-review examines pathways participating in peroxisomal fatty acid oxidation that lead to succinyl-CoA production, potentially supporting succinylation of extramitochondrial proteins. Furthermore, the influence of the mitochondrial status on cytosolic NAD+ availability affecting the activity of cytosolic SIRT5 iso1 and iso4-in turn regulating cytosolic protein lysine succinylations-is presented. Finally, the discovery that glia in the adult human brain lack subunits of both alpha-ketoglutarate dehydrogenase complex and succinate-CoA ligase-thus being unable to produce succinyl-CoA in the matrix-and yet exhibit robust pancellular lysine succinylation, is highlighted.


Asunto(s)
Lisina/química , Lisina/metabolismo , Procesamiento Proteico-Postraduccional , Proteínas/química , Proteínas/metabolismo , Humanos , Complejo Cetoglutarato Deshidrogenasa/metabolismo , Neuroglía/metabolismo , Sirtuinas/metabolismo , Succinato Deshidrogenasa/metabolismo
10.
Biol Lett ; 17(2): 20200759, 2021 02.
Artículo en Inglés | MEDLINE | ID: mdl-33563134

RESUMEN

Aerobic metabolism of aquatic ectotherms is highly sensitive to fluctuating climates. Many mitochondrial traits exhibit phenotypic plasticity in response to acute variations in temperature and oxygen availability. These responses are critical for understanding the effects of environmental variations on aquatic ectotherms' performance. Using the European seabass, Dicentrarchus labrax, we determined the effects of acute warming and deoxygenation in vitro on mitochondrial respiratory capacities and mitochondrial efficiency to produce ATP (ATP/O ratio). We show that acute warming reduced ATP/O ratio but deoxygenation marginally raised ATP/O ratio, leading to a compensatory effect of low oxygen availability on mitochondrial ATP/O ratio at high temperature. The acute effect of warming and deoxygenation on mitochondrial efficiency might be related to the leak of protons across the mitochondrial inner membrane, as the mitochondrial respiration required to counteract the proton leak increased with warming and decreased with deoxygenation. Our study underlines the importance of integrating the combined effects of temperature and oxygen availability on mitochondrial metabolism. Predictions on decline in performance of aquatic ectotherms owing to climate change may not be accurate, since these predictions typically look at respiratory capacity and ignore efficiency of ATP production.


Asunto(s)
Lubina , Oxígeno , Animales , Mitocondrias , Consumo de Oxígeno , Temperatura
11.
J Biol Chem ; 296: 100357, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33539923

RESUMEN

Mitochondrial ATP synthase is a reversible nanomotor synthesizing or hydrolyzing ATP depending on the potential across the membrane in which it is embedded. In the unicellular parasite Trypanosoma brucei, the direction of the complex depends on the life cycle stage of this digenetic parasite: in the midgut of the tsetse fly vector (procyclic form), the FoF1-ATP synthase generates ATP by oxidative phosphorylation, whereas in the mammalian bloodstream form, this complex hydrolyzes ATP and maintains mitochondrial membrane potential (ΔΨm). The trypanosome FoF1-ATP synthase contains numerous lineage-specific subunits whose roles remain unknown. Here, we seek to elucidate the function of the lineage-specific protein Tb1, the largest membrane-bound subunit. In procyclic form cells, Tb1 silencing resulted in a decrease of FoF1-ATP synthase monomers and dimers, rerouting of mitochondrial electron transfer to the alternative oxidase, reduced growth rate and cellular ATP levels, and elevated ΔΨm and total cellular reactive oxygen species levels. In bloodstream form parasites, RNAi silencing of Tb1 by ∼90% resulted in decreased FoF1-ATPase monomers and dimers, but it had no apparent effect on growth. The same findings were obtained by silencing of the oligomycin sensitivity-conferring protein, a conserved subunit in T. brucei FoF1-ATP synthase. However, as expected, nearly complete Tb1 or oligomycin sensitivity-conferring protein suppression was lethal because of the inability to sustain ΔΨm. The diminishment of FoF1-ATPase complexes was further accompanied by a decreased ADP/ATP ratio and reduced oxygen consumption via the alternative oxidase. Our data illuminate the often diametrically opposed bioenergetic consequences of FoF1-ATP synthase loss in insect versus mammalian forms of the parasite.


Asunto(s)
Adenosina Trifosfato/metabolismo , Ciclo Celular , Metabolismo Energético , Mitocondrias/metabolismo , ATPasas de Translocación de Protón/deficiencia , Proteínas Protozoarias/genética , Trypanosoma brucei brucei/metabolismo , Adenosina Trifosfato/genética , Potencial de la Membrana Mitocondrial , Mitocondrias/genética , ATPasas de Translocación de Protón/metabolismo , Proteínas Protozoarias/metabolismo , Trypanosoma brucei brucei/genética
12.
Front Physiol ; 11: 543564, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-33335484

RESUMEN

A metabolic hallmark of many cancers is the increase in glucose consumption coupled to excessive lactate production. Mindful that L-lactate originates only from pyruvate, the question arises as to how can this be sustained in those tissues where pyruvate kinase activity is reduced due to dimerization of PKM2 isoform or inhibited by oxidative/nitrosative stress, posttranslational modifications or mutations, all widely reported findings in the very same cells. Hereby 17 pathways connecting glucose to lactate bypassing pyruvate kinase are reviewed, some of which transit through the mitochondrial matrix. An additional 69 converging pathways leading to pyruvate and lactate, but not commencing from glucose, are also examined. The minor production of pyruvate and lactate by glutaminolysis is scrutinized separately. The present review aims to highlight the ways through which L-lactate can still be produced from pyruvate using carbon atoms originating from glucose or other substrates in cells with kinetically impaired pyruvate kinase and underscore the importance of mitochondria in cancer metabolism irrespective of oxidative phosphorylation.

13.
iScience ; 23(11): 101761, 2020 Nov 20.
Artículo en Inglés | MEDLINE | ID: mdl-33251492

RESUMEN

ATP is required for mammalian cells to remain viable and to perform genetically programmed functions. Maintenance of the ΔG'ATP hydrolysis of -56 kJ/mole is the endpoint of both genetic and metabolic processes required for life. Various anomalies in mitochondrial structure and function prevent maximal ATP synthesis through OxPhos in cancer cells. Little ATP synthesis would occur through glycolysis in cancer cells that express the dimeric form of pyruvate kinase M2. Mitochondrial substrate level phosphorylation (mSLP) in the glutamine-driven glutaminolysis pathway, substantiated by the succinate-CoA ligase reaction in the TCA cycle, can partially compensate for reduced ATP synthesis through both OxPhos and glycolysis. A protracted insufficiency of OxPhos coupled with elevated glycolysis and an auxiliary, fully operational mSLP, would cause a cell to enter its default state of unbridled proliferation with consequent dedifferentiation and apoptotic resistance, i.e., cancer. The simultaneous restriction of glucose and glutamine offers a therapeutic strategy for managing cancer.

14.
Front Nutr ; 7: 21, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32219096

RESUMEN

Breast cancer remains as a significant cause of morbidity and mortality in women. Ultrastructural and biochemical evidence from breast biopsy tissue and cancer cells shows mitochondrial abnormalities that are incompatible with energy production through oxidative phosphorylation (OxPhos). Consequently, breast cancer, like most cancers, will become more reliant on substrate level phosphorylation (fermentation) than on oxidative phosphorylation (OxPhos) for growth consistent with the mitochondrial metabolic theory of cancer. Glucose and glutamine are the prime fermentable fuels that underlie therapy resistance and drive breast cancer growth through substrate level phosphorylation (SLP) in both the cytoplasm (Warburg effect) and the mitochondria (Q-effect), respectively. Emerging evidence indicates that ketogenic metabolic therapy (KMT) can reduce glucose availability to tumor cells while simultaneously elevating ketone bodies, a non-fermentable metabolic fuel. It is suggested that KMT would be most effective when used together with glutamine targeting. Information is reviewed for suggesting how KMT could reduce systemic inflammation and target tumor cells without causing damage to normal cells. Implementation of KMT in the clinic could improve progression free and overall survival for patients with breast cancer.

15.
Cancers (Basel) ; 12(3)2020 Mar 05.
Artículo en Inglés | MEDLINE | ID: mdl-32150977

RESUMEN

Pheochromocytoma/paragangliomas (Pheo/PGL) are rare endocrine cancers with strong genetic background. Mutations in the SDHB subunit of succinate dehydrogenase (SDH) predispose patients to malignant disease with limited therapeutic options and poor prognosis. Using a host of cellular and molecular biology techniques in 2D and 3D cell culture formats we show that SDH inhibition had cell line specific biological and biochemical consequences. Based on our studies performed on PC12 (rat chromaffin cell line), Hela (human cervix epithelial cell line), and H295R (human adrenocortical cell line) cells, we demonstrated that chromaffin cells were not affected negatively by the inhibition of SDH either by siRNA directed against SDHB or treatment with SDH inhibitors (itaconate and atpenin A5). Cell viability and intracellular metabolite measurements pointed to the cell line specific consequences of SDH impairment and to the importance of glutamate metabolism in chromaffin cells. A significant increase in glutaminase-1 (GLS-1) expression after SDH impairment was observed in PC12 cells. GLS-1 inhibitor BPTES was capable of significantly decreasing proliferation of SDH impaired PC12 cells. Glutaminase-1 and SDHB expressions were tested in 35 Pheo/PGL tumor tissues. Expression of GLS1 was higher in the SDHB low expressed group compared to SDHB high expressed tumors. Our data suggest that the SDH-associated malignant potential of Pheo/PGL is strongly dependent on GLS-1 expression and glutaminases may be novel targets for therapy.

16.
Exp Neurol ; 327: 113218, 2020 05.
Artículo en Inglés | MEDLINE | ID: mdl-32035071

RESUMEN

It is a textbook definition that in the absence of oxygen or inhibition of the mitochondrial respiratory chain by pharmacologic or genetic means, hyper-reduction of the matrix pyridine nucleotide pool ensues due to impairment of complex I oxidizing NADH, leading to reductive stress. However, even under these conditions, the ketoglutarate dehydrogenase complex (KGDHC) is known to provide succinyl-CoA to succinyl-CoA ligase, thus supporting mitochondrial substrate-level phosphorylation (mSLP). Mindful that KGDHC is dependent on provision of NAD+, hereby sources of acute NADH oxidation are reviewed, namely i) mitochondrial diaphorases, ii) reversal of mitochondrial malate dehydrogenase, iii) reversal of the mitochondrial isocitrate dehydrogenase as it occurs under acidic conditions, iv) residual complex I activity and v) reverse operation of the malate-aspartate shuttle. The concept of NAD+ import through the inner mitochondrial membrane as well as artificial means of manipulating matrix NAD+/NADH are also discussed. Understanding the above mechanisms providing NAD+ to KGDHC thus supporting mSLP may assist in dampening mitochondrial dysfunction underlying neurological disorders encompassing impairment of the electron transport chain.


Asunto(s)
Transporte de Electrón/fisiología , Mitocondrias/metabolismo , NAD/metabolismo , Estrés Oxidativo/fisiología , Consumo de Oxígeno/fisiología , Animales , Respiración de la Célula , Oxidación-Reducción
17.
Brain Struct Funct ; 225(2): 639-667, 2020 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-31982949

RESUMEN

The ketoglutarate dehydrogenase complex (KGDHC) consists of three different subunits encoded by OGDH (or OGDHL), DLST, and DLD, combined in different stoichiometries. DLD subunit is shared between KGDHC and pyruvate dehydrogenase complex, branched-chain alpha-keto acid dehydrogenase complex, and the glycine cleavage system. Despite KGDHC's implication in neurodegenerative diseases, cell-specific localization of its subunits in the adult human brain has never been investigated. Here, we show that immunoreactivity of all known isoforms of OGDHL, OGDH, and DLST was detected exclusively in neurons of surgical human cortical tissue samples identified by their morphology and visualized by double labeling with fluorescent Nissl, while being absent from glia expressing GFAP, Aldhl1, myelin basic protein, Olig2, or IBA1. In contrast, DLD immunoreactivity was evident in both neurons and glia. Specificity of anti-KGDHC subunits antisera was verified by a decrease in staining of siRNA-treated human cancer cell lines directed against the respective coding gene products; furthermore, immunoreactivity of KGDHC subunits in human fibroblasts co-localized > 99% with mitotracker orange, while western blotting of 63 post-mortem brain samples and purified recombinant proteins afforded further assurance regarding antisera monospecificity. KGDHC subunit immunoreactivity correlated with data from the Human Protein Atlas as well as RNA-Seq data from the Allen Brain Atlas corresponding to genes coding for KGDHC components. Protein lysine succinylation, however, was immunohistochemically evident in all cortical cells; this was unexpected, because this posttranslational modification requires succinyl-CoA, the product of KGDHC. In view of the fact that glia of the human brain cortex lack succinate-CoA ligase, an enzyme producing succinyl-CoA when operating in reverse, protein lysine succinylation in these cells must exclusively rely on propionate and/or ketone body metabolism or some other yet to be discovered pathway encompassing succinyl-CoA.


Asunto(s)
Acilcoenzima A/análisis , Corteza Cerebral/química , Complejo Cetoglutarato Deshidrogenasa/análisis , Lisina/análisis , Neuronas/química , Células Cultivadas , Femenino , Humanos , Masculino , Neuroglía/metabolismo , Isoformas de Proteínas/análisis , Subunidades de Proteína/análisis
19.
Mol Aspects Med ; 71: 100834, 2020 02.
Artículo en Inglés | MEDLINE | ID: mdl-31740079

RESUMEN

Neurometabolic disorders stem from errors in metabolic processes yielding a neurological phenotype. A subset of those disorders encompasses mitochondrial abnormalities partially due to mitochondrial DNA (mtDNA) depletion. mtDNA depletion can be attributed to inheritance, spontaneous mutations or acquired from drug-related toxicities. In the armamentarium of diagnostic procedures, mtDNA quantification is a standard for disease classification. However, alterations in mtDNA obtained from peripheral tissues such as skin fibroblasts and blood cells do not often reflect the severity of the affected organ, in this case, the brain. The purpose of this review is to highlight the pitfalls of quantitating mtDNA from peripheral -and not limited to-tissues for diagnosing patients suffering from a variety of mtDNA depletion syndromes exhibiting neurologic abnormalities. In lieu, a qualitative test of mitochondrial substrate-level phosphorylation -even from peripheral tissues-reflecting the ability of mitochondria to rely on glutaminolysis in the presence of respiratory chain defects is proposed as a novel diagnostic assessment of mitochondrial functionality.


Asunto(s)
Encefalopatías Metabólicas/diagnóstico , ADN Mitocondrial/análisis , Mitocondrias/genética , Encefalopatías Metabólicas/genética , Pruebas Diagnósticas de Rutina , Femenino , Humanos , Masculino , Mutación , Fosforilación , Índice de Severidad de la Enfermedad
20.
Neuron ; 105(5): 867-881.e9, 2020 03 04.
Artículo en Inglés | MEDLINE | ID: mdl-31883789

RESUMEN

The human-specific gene ARHGAP11B is preferentially expressed in neural progenitors of fetal human neocortex and increases abundance and proliferation of basal progenitors (BPs), which have a key role in neocortex expansion. ARHGAP11B has therefore been implicated in the evolutionary expansion of the human neocortex, but its mode of action has been unknown. Here, we show that ARHGAP11B is imported into mitochondria, where it interacts with the adenine nucleotide translocase (ANT) and inhibits the mitochondrial permeability transition pore (mPTP). BP expansion by ARHGAP11B requires its presence in mitochondria, and pharmacological inhibition of ANT function or mPTP opening mimic BP expansion by ARHGAP11B. Searching for the underlying metabolic basis, we find that BP expansion by ARHGAP11B requires glutaminolysis, the conversion of glutamine to glutamate for the tricarboxylic acid (TCA) cycle. Hence, an ARHGAP11B-induced, mitochondria-based effect on BP metabolism that is a hallmark of highly mitotically active cells appears to underlie its role in neocortex expansion.


Asunto(s)
Proteínas Activadoras de GTPasa/metabolismo , Glutamina/metabolismo , Mitocondrias/metabolismo , Neocórtex/metabolismo , Células-Madre Neurales/metabolismo , Células 3T3 , Animales , Evolución Biológica , Proliferación Celular/genética , Ciclo del Ácido Cítrico , Proteínas Activadoras de GTPasa/genética , Regulación del Desarrollo de la Expresión Génica/genética , Ácido Glutámico/metabolismo , Humanos , Ratones , Translocasas Mitocondriales de ADP y ATP/metabolismo , Proteínas de Transporte de Membrana Mitocondrial/metabolismo , Poro de Transición de la Permeabilidad Mitocondrial , Neocórtex/embriología , Neurogénesis/genética
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA
...