RESUMO
SLC25A42 gene encodes an inner mitochondrial membrane protein that imports Coenzyme A into the mitochondrial matrix. A mutation in this gene was recently reported in a subject born to consanguineous parents who presented with mitochondrial myopathy with muscle weakness and lactic acidosis. In this report, we present 12 additional individuals with the same founder mutation who presented with variable manifestations ranging from asymptomatic lactic acidosis to a severe phenotype characterized by developmental regression and epilepsy. Our report confirms the link between SLC25A42 and mitochondrial disease in humans, and suggests that pathogenic variants in SLC25A42 should be interpreted with the understanding that the associated phenotype may be highly variable.
Assuntos
Acidose Láctica/genética , Encefalomiopatias Mitocondriais/genética , Miopatias Mitocondriais/genética , Proteínas de Transporte de Nucleotídeos/genética , Acidose Láctica/patologia , Adolescente , Adulto , Criança , Pré-Escolar , DNA Mitocondrial , Feminino , Humanos , Lactente , Masculino , Mitocôndrias/genética , Mitocôndrias/patologia , Encefalomiopatias Mitocondriais/complicações , Encefalomiopatias Mitocondriais/patologia , Miopatias Mitocondriais/patologia , Linhagem , Fenótipo , Mutação Puntual , Adulto JovemRESUMO
Mutations in FBXL4 have recently been recognized to cause a mitochondrial disorder, with clinical features including early onset lactic acidosis, hypotonia, and developmental delay. FBXL4 sequence analysis was performed in 808 subjects suspected to have a mitochondrial disorder. In addition, 28 samples from patients with early onset of lactic acidosis, but without identifiable mutations in 192 genes known to cause mitochondrial diseases, were examined for FBXL4 mutations. Definitive diagnosis was made in 10 new subjects with a total of 7 novel deleterious variants; 5 null and 2 missense substitutions. All patients exhibited congenital lactic acidemia, most of them with severe encephalopathic presentation, and global developmental delay. Overall, FBXL4 defects account for at least 0.7% (6 out of 808) of subjects suspected to have a mitochondrial disorder, and as high as 14.3% (4 out of 28) in young children with congenital lactic acidosis and clinical features of mitochondrial disease. Including FBLX4 in the mitochondrial diseases panel should be particularly important for patients with congenital lactic acidosis.
Assuntos
Acidose Láctica/genética , Proteínas F-Box/genética , Erros Inatos do Metabolismo/genética , Doenças Mitocondriais/genética , Ubiquitina-Proteína Ligases/genética , Acidose Láctica/diagnóstico , Acidose Láctica/fisiopatologia , Criança , DNA Mitocondrial/genética , Feminino , Humanos , Lactente , Masculino , Erros Inatos do Metabolismo/diagnóstico , Erros Inatos do Metabolismo/fisiopatologia , Doenças Mitocondriais/classificação , Doenças Mitocondriais/diagnóstico , Doenças Mitocondriais/fisiopatologia , MutaçãoRESUMO
Mitochondrial membrane permeabilization is central to apoptotic signaling and is directly regulated by the Bcl-2 family of proteins, consisting of anti-apoptotic members and pro-apoptotic members, although the precise mechanisms involved remain elusive. When cells are deficient in both pro-apoptotic multidomain members of this family (Bax and Bak), mitochondrial membrane permeabilization does not occur in response to various apoptotic stimuli. We have previously reported that the voltage-dependent anion channel (VDAC or porin) plays a role in apoptotic mitochondrial membrane permeabilization by interacting with Bcl-2 family members. Here, we have provided additional evidence that VDAC2 is required for pro-apoptotic activity of Bax in the absence of Bak. In the absence of Bak, VDAC2-deficient cells showed strong resistance to various apoptotic stimuli, whereas re-introduction of the Vdac2 gene restored their apoptotic response. Consistently, silencing of VDAC2 in Bak-deficient cells, but not Bax-deficient cells, also conferred resistance to various apoptotic stimuli. In the absence of VDAC2 and Bak, the activation of Bax (assessed by mitochondrial membrane integration, conformational changes and oligomerization) was markedly impaired. Taken together, these findings indicate that VDAC2 is required for pro-apoptotic activity of Bax in the absence of Bak.
Assuntos
Apoptose , Canal de Ânion 2 Dependente de Voltagem/fisiologia , Proteína X Associada a bcl-2/fisiologia , Animais , Células Cultivadas , Camundongos , Tunicamicina/farmacologia , Proteína Killer-Antagonista Homóloga a bcl-2/fisiologiaRESUMO
BACKGROUND: Infantile cardiomyopathy is a genetically heterogeneous disorder with significant morbidity and mortality. METHODS: This study aimed to identify the mutation present in four unrelated patients who presented as infants with isolated hypertrophic cardiomyopathy. RESULTS: In all four, a novel mitochondrial m.8528T-->C mutation was identified. This results in a change of the initiation codon in ATPase 6 to threonine and a concurrent change from a highly conserved hydrophobic amino acid, tryptophan, at position 55 of ATPase 8 to a highly basic arginine. To our knowledge, this is the first report of a mutation affecting both mitochondrial genome-encoded complex V subunit proteins. Testing of the relatives of one patient indicated that the mutation is heteroplasmic and correlated with disease. CONCLUSION: Mitochondrial genome sequencing should be considered in patients with infantile hypertrophic cardiomyopathy.
Assuntos
Cardiomiopatia Hipertrófica/genética , ATPases Mitocondriais Próton-Translocadoras/genética , Mutação , Sequência de Bases , Cardiomiopatia Hipertrófica/enzimologia , Cardiomiopatia Hipertrófica/patologia , Criança , Pré-Escolar , Análise Mutacional de DNA , Feminino , Humanos , Lactente , Recém-Nascido , MasculinoRESUMO
Published mutations in deoxyguanosine kinase (DGUOK) cause mitochondrial DNA depletion and a clinical phenotype that consists of neonatal liver failure, nystagmus and hypotonia. In this series, we have identified 15 different mutations in the DGUOK gene from 9 kindreds. Among them, 12 have not previously been reported. Nonsense, splice site, or frame-shift mutations that produce truncated proteins predominate over missense mutations. All patients who harbor null mutations had early onset liver failure and significant neurological disease. These patients have all died before 2-years of age. Conversely, two patients carrying missense mutations had isolated liver disease and are alive in their 4th year of life without liver transplant. Five subjects were detected by newborn screening, with elevated tyrosine or phenylalanine. Consequently, this disease should be considered if elevated tyrosine is identified by newborn screening. Mitochondrial DNA content was below 10% of controls in liver in all but one case and modestly reduced in blood cells. With this paper a total of 39 different mutations in DGUOK have been identified. The most frequent mutation, c.763_c.766dupGATT, occurs in 8 unrelated kindreds. 70% of mutations occur in only one kindred, suggesting full sequencing of this gene is required for diagnosis. The presentation of one case with apparent viral hepatitis, without neurological disease, suggests that this disease should be considered in patients with infantile liver failure regardless of the presence of neurological features or apparent infectious etiology.
Assuntos
DNA Mitocondrial/genética , Mutação/genética , Fosfotransferases (Aceptor do Grupo Álcool)/genética , Adolescente , Pré-Escolar , Feminino , Humanos , Lactente , Recém-Nascido , Masculino , Especificidade de ÓrgãosRESUMO
High-resolution array-comparative genome hybridization (CGH) is a powerful tool for detection of submicroscopic chromosome deletions and duplications. We describe two patients with mild mental retardation (MR) and de novo microdeletions of 17q11.2q12. Although the deletions did not involve the neurofibromatosis type 1 (NF1) gene, they overlap with long-range deletions of the NF1 region which have been encountered in a small group of NF1 patients with more severe MR. Given the overlap of the deletions in our two patients with the large-sized NF1 microdeletions but not with the more frequent and smaller NF1 deletions, we hypothesize that more than one gene in the 17q11.2q12 region may be involved in MR. We discuss candidate genes for MR within this interval that was precisely defined through array-CGH analysis.
Assuntos
Deleção Cromossômica , Cromossomos Humanos Par 17 , Deficiências do Desenvolvimento/genética , Hibridização de Ácido Nucleico , Criança , Pré-Escolar , Análise Citogenética/métodos , Feminino , Humanos , MasculinoRESUMO
We report a severe case of Dentatorubro-pallidoluysian atrophy (DRPLA) presenting with microcephaly, developmental delay, severe epilepsy, and progressive mental deterioration with a very early onset of disease. The case is notable for the early detection of white matter changes by brain MRI. Neuroradiological findings from the case were compared to those of previously reported patients with disease onset before 10 years of age.
Assuntos
Doenças do Recém-Nascido , Microcefalia/complicações , Epilepsias Mioclônicas Progressivas/complicações , Convulsões/etiologia , Criança , Humanos , Recém-Nascido , Estudos Longitudinais , Imageamento por Ressonância Magnética/métodos , Masculino , Microcefalia/patologia , Epilepsias Mioclônicas Progressivas/patologia , Literatura de Revisão como AssuntoRESUMO
We present molecular genetic investigations of a 4-year-old boy with craniofacial dysmorphism and developmental delay. Trivial mitral and tricuspid regurgitation without gross structural abnormality was diagnosed by echocardiography. High-resolution chromosome analysis revealed an interstitial deletion, del(10)(p12.1p12.32). To characterize the deletion size and breakpoints, we performed fluorescence in situ hybridization analysis using 27 BAC clones. Our data demonstrate an approximately 5.5 Mb deletion del(10)(p12.1p12.31). Surprisingly, the BAC clone RP11-56H7 that contains NEBL, an apparent downstream gene of the cardiogenic transcription factor HAND2 previously shown to be deleted in the patients with DiGeorge 2 syndrome and 10p13 deletion, was deleted in our patient with 10p12.1-p12.31 deletion. In addition, we provide clinical data and results of molecular analysis for a patient with multiple congenital anomalies including Ebstein's anomaly, kidney malformations, and 10p13-p14 deletion. We also reviewed 19 patients with congenital heart defects and deletions involving 10p and propose that atrial septal defect (ASD) is a common cardiac anomaly associated with DiGeorge 2 syndrome. Based on genotype-phenotype analysis of published patients and those reported herein, we propose an approximately 1.0 Mb critical region between loci D10S547 and D10S2176 in 10p14 to be associated with ASD. Considering that septal defects are the most frequent congenital heart anomaly, we suggest that further investigations in the 10p critical region are important to identify gene(s) responsible for this common birth defect.
Assuntos
Deleção Cromossômica , Cromossomos Humanos Par 10/genética , Síndrome de DiGeorge/genética , Cardiopatias Congênitas/patologia , Infecções por Klebsiella/fisiopatologia , Pré-Escolar , Análise Citogenética , Ecocardiografia , Feminino , Humanos , Hibridização in Situ Fluorescente , Lactente , MasculinoRESUMO
Leptin is a powerful inhibitor of bone formation in vivo. This antiosteogenic function involves leptin binding to its receptors on ventromedial hypothalamic neurons, the autonomous nervous system and beta-adrenergic receptors on osteoblasts. However, the mechanisms whereby leptin controls the function of ventromedial hypothalamic antiosteogenic neurons remain unclear. In this study, we compared the ability of leptin to regulate body weight and bone mass and show that leptin antiosteogenic and anorexigenic functions are affected by similar amounts of leptin. Using a knock-in of LacZ in the leptin locus, we failed to detect any leptin synthesis in the central nervous system. However, increasing serum leptin level, even dramatically, reduced bone mass. Conversely, reducing serum-free leptin level by overexpressing a soluble receptor for leptin increased bone mass. Congruent with these results, the high bone mass of lipodystrophic mice could be corrected by restoring serum leptin level, suggesting that leptin is an adipocyte product both necessary and sufficient to control bone mass. Consistent with the high bone mass phenotype of lipodystrophic mice, we observed an advanced bone age, an indirect reflection of premature bone formation, in lipodystrophic patients. Taken together, these results indicate that adipocyte-derived circulating leptin is a determinant of bone formation and suggests that leptin antiosteogenic function is conserved in vertebrates.
Assuntos
Densidade Óssea/fisiologia , Encéfalo/fisiologia , Leptina/sangue , Animais , Densidade Óssea/efeitos dos fármacos , Ventrículos Cerebrais , Homeostase , Humanos , Infusões Parenterais , Leptina/administração & dosagem , Leptina/farmacologia , Lipodistrofia/fisiopatologia , Camundongos , Camundongos Obesos , Camundongos TransgênicosRESUMO
We surveyed 16 subjects with the clinical diagnosis of Noonan Syndrome (NS1) from 12 families and their relevant family members for mutations in PTPN11/SHP2 using direct DNA sequencing. We found three different mutations among five families. Two unrelated subjects shared the same de novo missense substitution in exon 13 (S502T); an additional two unrelated families had a mutation in exon 3 (Y63C); and one subject had the amino acid substitution Y62D, also in exon 3. None of the three mutations were present in ethnically matched controls. In the mature protein model, the exon 3 mutants and the exon 13 mutant amino acids cluster at the interface between the N' SH2 domain and the phosphatase catalytic domain. Six of eight subjects with PTPN11/SHP2 mutations had pulmonary valve stenosis while no mutations were identified in those subjects (N = 4) with hypertrophic cardiomyopathy. An additional four subjects with possible Noonan syndrome were evaluated, but no mutations in PTPN11/SHP2 were identified. These results confirm that mutations in PTPN11/SHP2 underlie a common form of Noonan syndrome, and that the disease exhibits both allelic and locus heterogeneity. The observation of recurrent mutations supports the hypothesis that a special class of gain-of-function mutations in SHP2 give rise to Noonan syndrome.
Assuntos
Análise Mutacional de DNA/métodos , Éxons/genética , Mutação/genética , Síndrome de Noonan/enzimologia , Síndrome de Noonan/genética , Proteínas Tirosina Fosfatases/genética , Domínio Catalítico/genética , Feminino , Humanos , Peptídeos e Proteínas de Sinalização Intracelular , Isoenzimas/genética , Masculino , Fenótipo , Estrutura Quaternária de Proteína/genética , Proteína Tirosina Fosfatase não Receptora Tipo 11 , Proteínas Tirosina Fosfatases/química , Recidiva , Proteínas Tirosina Fosfatases Contendo o Domínio SH2 , Domínios de Homologia de src/genéticaRESUMO
Voltage-dependent anion channels (VDACs), also known as mitochondrial porins, are small channel proteins involved in the translocation of metabolites across the mitochondrial outer membrane. A single channel-forming protein is found in yeast, whereas higher eukaryotes express multiple VDACs, with humans and mice each harboring three distinct channels (VDAC1-3) encoded by separate genes. To begin to assess the functions of each of the three isoforms, the VDAC3 gene was inactivated by targeted disruption in embryonic stem cells. Here we show that mice lacking VDAC3 are healthy, but males are infertile. Although there are normal sperm numbers, the sperm exhibit markedly reduced motility. Structural defects were found in two-thirds of epididymal axonemes, with the most common abnormality being loss of a single microtubule doublet at a conserved position within the axoneme. In testicular sperm, the defect was only rarely observed, suggesting that instability of a normally formed axoneme occurs with sperm maturation. In contrast, tracheal epithelial cilia showed no structural abnormalities. In addition, skeletal muscle mitochondria were abnormally shaped, and activities of the respiratory chain complexes were reduced. These results demonstrate that axonemal defects may be caused by associated nonaxonemal components such as mitochondrial channels and illustrate that normal mitochondrial function is required for stability of the axoneme.
Assuntos
Infertilidade Masculina/genética , Porinas/genética , Porinas/fisiologia , Motilidade dos Espermatozoides/genética , Motilidade dos Espermatozoides/fisiologia , Animais , Northern Blotting , Western Blotting , Transporte de Elétrons , Imuno-Histoquímica , Masculino , Camundongos , Microscopia Eletrônica , Mitocôndrias/metabolismo , Modelos Genéticos , Músculo Esquelético/metabolismo , Músculo Esquelético/ultraestrutura , Porinas/biossíntese , Isoformas de Proteínas , Contagem de Espermatozoides , Distribuição Tecidual , Canal de Ânion 1 Dependente de Voltagem , Canais de Ânion Dependentes de VoltagemRESUMO
Voltage-dependent anion channels (VDACs) form the main pathway for metabolites across the mitochondrial outer membrane. The mouse vdac1 gene has been disrupted by gene targeting, and the resulting mutant mice have been examined for defects in muscle physiology. To test the hypothesis that VDAC1 constitutes a pathway for ADP translocation into mitochondria, the apparent mitochondrial sensitivity for ADP (Km(ADP)) and the calculated rate of respiration in the presence of the maximal ADP concentration (Vmax) have been assessed using skinned fibers prepared from two oxidative muscles (ventricle and soleus) and a glycolytic muscle (gastrocnemius) in control and vdac1(-/-) mice. We observed a significant increase in the apparent Km((ADP)) in heart and gastrocnemius, whereas the V(max) remained unchanged in both muscles. In contrast, a significant decrease in both the apparent Km((ADP)) and V(max) was observed in soleus. To test whether VDAC1 is required for creatine stimulation of mitochondrial respiration in oxidative muscles, the apparent Km((ADP)) and Vmax were determined in the presence of 25 mm creatine. The creatine effect on mitochondrial respiration was unchanged in both heart and soleus. These data, together with the significant increase in citrate synthase activity in heart, but not in soleus and gastrocnemius, suggest that distinct metabolic responses to altered mitochondrial outer membrane permeability occur in these different striated muscle types.
Assuntos
Difosfato de Adenosina/metabolismo , Mitocôndrias Musculares/metabolismo , Músculo Esquelético/metabolismo , Porinas/fisiologia , Animais , Western Blotting , Citrato (si)-Sintase/metabolismo , Ventrículos do Coração/enzimologia , Camundongos , Camundongos Knockout , Microscopia Eletrônica , Mitocôndrias Musculares/ultraestrutura , Oxirredução , Porinas/genética , Canal de Ânion 1 Dependente de Voltagem , Canais de Ânion Dependentes de VoltagemRESUMO
A diagnosis of severe infantile, autosomal recessive osteopetrosis (I-ARO) was made in a 3-month-old female based on characteristic radiological and histological findings. The finding of multiple fractures at presentation in this infant is highly unusual. Deficiency of carbonic-anhydrase type II was excluded.
Assuntos
Fraturas Espontâneas/etiologia , Osteopetrose/complicações , Osteopetrose/diagnóstico , Biópsia , Diagnóstico Diferencial , Evolução Fatal , Feminino , Fraturas Espontâneas/diagnóstico , Humanos , Ílio/patologia , Lactente , Osteopetrose/patologia , Índice de Gravidade de DoençaRESUMO
Type I collagen is the most abundant structural protein in the mammalian body. It exists as a heterotrimer of two subunits in the form [alpha1(I)]2alpha2(I). Pathogenic mutations in COL1A1 and COL1A2, the genes that encode the two subunits, cause a range of phenotypes including mild to lethal forms of osteogenesis imperfecta and a restricted set of Ehlers-Danlos syndrome phenotypes. Lethal mutations usually result from missense mutations that disrupt the normal triple helical structure of the molecule. Multi-exon duplication or deletion in type I collagen genes has rarely been observed and has generally resulted in a lethal or severe phenotype. We report a partial duplication in the COLIA2 gene that causes a relatively mild phenotype, despite the addition of 477 amino acids to the triple helical domain of the proalpha2(I) chain. The abnormal molecule is synthesized and secreted by cultured dermal fibroblasts in a normal fashion. Electron microscopy of dermal tissue reveals small but otherwise near normal collagen fibrils. The gene duplication occurred by mitotic sister chromatid exchange in the mother who is mosaic for the duplication allele. Examination of the abnormal sequence suggests a means by which the duplicated molecule could be processed and properly incorporated into mature collagen fibrils.
Assuntos
Colágeno/genética , Síndrome de Ehlers-Danlos/genética , Duplicação Gênica , Osteogênese Imperfeita/genética , Sequência de Bases , Biópsia , Células Cultivadas , Colágeno/biossíntese , Pai , Fibroblastos , Humanos , Lactente , Masculino , Dados de Sequência Molecular , Mães , Fenótipo , Polimorfismo Genético , Pró-Colágeno/biossíntese , Homologia de Sequência do Ácido Nucleico , Pele/metabolismo , Pele/ultraestruturaRESUMO
As part of a systematic screen for novel imprinted genes of human chromosome 7 we have investigated GRB10, which belongs to a small family of adapter proteins, known to interact with a number of receptor tyrosine kinases and signalling molecules. Upon allele-specific transcription analysis involving multiple distinct splice variants in various fetal tissues, we found that human GRB10 is imprinted in a highly isoform- and tissue-specific manner. In fetal brains, most variants are transcribed exclusively from the paternal allele. Imprinted expression in this tissue is not accompanied by allele-specific methylation of the most 5' CpG island. In skeletal muscle, one GRB10 isoform, gamma1, is expressed from the maternal allele alone, whereas in numerous other fetal tissues, all GRB10 splice variants are transcribed from both parental alleles. A remarkable finding is paternal-specific expression of GRB10 in the human fetal brain, since, in the mouse, this gene is transcribed exclusively from the maternal allele. To our knowledge, this is the first example of a gene that is oppositely imprinted in mouse and human.
Assuntos
Alelos , Impressão Genômica , Proteínas/genética , Anormalidades Múltiplas/genética , Processamento Alternativo , Sequência de Bases , Metilação de DNA , DNA Complementar/química , DNA Complementar/genética , Feminino , Retardo do Crescimento Fetal/genética , Feto/metabolismo , Proteína Adaptadora GRB10 , Regulação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Humanos , Masculino , Dados de Sequência Molecular , Mutação , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Proteínas/metabolismo , Análise de Sequência de DNA , Síndrome , Distribuição TecidualRESUMO
Voltage-dependent anion channels (VDACs) are small, integral membrane proteins that traverse the outer mitochondrial membrane and conduct ATP and other small metabolites. They are known to bind several kinases of intermediary metabolism in a tissue-specific fashion, have been found in close association with the adenine nucleotide translocator of the inner mitochondrial membrane, and are hypothesized to form part of the mitochondrial permeability transition pore, which results in the release of cytochrome c at the onset of apoptotic cell death. VDACs are found throughout all strata of eukaryotic evolution and exhibit biophysical characteristics that are well conserved from yeast to mammals. The mammalian VDAC gene family consists of three isoforms, each of which shares approximately 70% sequence identity with the other two family members. Recently, we reported that a single codon (ATG) exon is alternatively spliced into the transcript of the type 3 voltage-dependent anion channel (VDAC3) in a tissue-specific fashion. This unusual splicing event was shown to be conserved between mouse and human, and we theorized that the spliced exon could lead to the creation of an alternative translational initiation site. Here we report that a highly specific polyclonal VDAC3 antibody was unable to detect the truncated protein isoform indicative of this putative downstream start site. From these in vivo studies, we conclude that the alternatively spliced exon results in the insertion of a single methionine residue at amino acid position 39 of the mature VDAC3 protein. Additionally, we have used a cross-species genomic sequence comparison to identify conserved regions that may be involved in the regulation of small exon splicing.
Assuntos
Processamento Alternativo , Éxons/genética , Mitocôndrias Musculares/metabolismo , Porinas/genética , Animais , Especificidade de Anticorpos/imunologia , Sequência de Bases , Encéfalo/metabolismo , Sequência Conservada , DNA/química , DNA/genética , Regulação da Expressão Gênica , Humanos , Masculino , Camundongos , Proteínas de Transporte da Membrana Mitocondrial , Dados de Sequência Molecular , Músculo Esquelético/metabolismo , Porinas/imunologia , Isoformas de Proteínas/genética , RNA Mensageiro/genética , Alinhamento de Sequência , Análise de Sequência de DNA , Homologia de Sequência do Ácido Nucleico , Canais de Ânion Dependentes de VoltagemRESUMO
There is little information on d-isomer-specific dehydrogenases in humans. Identification of d-2-hydroxyglutaric aciduria, an inherited metabolic disorder associated with severe neurological dysfunction, highlights the role of d-isomers in human metabolism. The possibility of a defect in d-2-hydroxyglutarate dehydrogenation prompted us to employ E. coli d-2-hydroxyacid dehydrogenase cDNA to search the human expressed sequence tags database. Two human EST homologues were retrieved and sequenced. Analysis showed the two clones were identical with 1258 nucleotides encoding 248 amino acids of the putative human d-2-hydroxyacid dehydrogenase. It was highly homologous to bacterial d-2-hydroxyacid dehydrogenases (46%), d-phosphoglycerate dehydrogenase (38%), and formate dehydrogenase (36%) at the amino acid level. The gene is expressed ubiquitously in tissue, most abundantly in liver, and was mapped to chromosome 9q between markers WI-3028 and WI-93330. To our knowledge this is the first cloning and characterization of the cDNA for a human d-isomer specific NAD(+)-dependent 2-hydroxyacid dehydrogenase.
Assuntos
Oxirredutases do Álcool/genética , Cromossomos Humanos Par 9 , L-Lactato Desidrogenase , Lactato Desidrogenases , Oxirredutases do Álcool/metabolismo , Sequência de Aminoácidos , Sequência de Bases , Mapeamento Cromossômico , Clonagem Molecular , Humanos , Dados de Sequência Molecular , Homologia de Sequência de AminoácidosAssuntos
Processamento Alternativo , Impressão Genômica , Proteínas/genética , Animais , Etiquetas de Sequências Expressas , Humanos , Linfócitos/metabolismo , Camundongos , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Proteínas/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Voltage-dependent anion channels (VDACs, also known as mitochondrial porins) are small pore-forming proteins of the mitochondrial outer membrane found in all eukaryotes. Mammals harbor three distinct VDAC isoforms, with each protein sharing 65-70% sequence identity. Deletion of the yeast VDAC1 gene leads to conditional lethality that can be partially or completely complemented by the mammalian VDAC genes. In vitro, VDACs conduct a variety of small metabolites and in vivo they serve as a binding site for several cytosolic kinases involved in intermediary metabolism, yet the specific physiologic role of each isoform is unknown. Here we show that mouse embryonic stem cells lacking each isoform are viable but exhibit a 30% reduction in oxygen consumption. VDAC1 and VDAC2 deficient cells exhibit reduced cytochrome c oxidase activity, whereas VDAC3 deficient cells have normal activity. These results indicate that VDACs are not essential for cell viability and we speculate that reduced respiration in part reflects decreased outer membrane permeability for small metabolites necessary for oxidative phosphorylation.