RESUMO
Type 2 diabetes (T2D) is a worldwide epidemic with a medical need for additional targeted therapies. Suppression of hepatic glucose production (HGP) effectively ameliorates diabetes and can be exploited for its treatment. We hypothesized that targeting PGC-1α acetylation in the liver, a chemical modification known to inhibit hepatic gluconeogenesis, could be potentially used for treatment of T2D. Thus, we designed a high-throughput chemical screen platform to quantify PGC-1α acetylation in cells and identified small molecules that increase PGC-1α acetylation, suppress gluconeogenic gene expression, and reduce glucose production in hepatocytes. On the basis of potency and bioavailability, we selected a small molecule, SR-18292, that reduces blood glucose, strongly increases hepatic insulin sensitivity, and improves glucose homeostasis in dietary and genetic mouse models of T2D. These studies have important implications for understanding the regulatory mechanisms of glucose metabolism and treatment of T2D.
Assuntos
Diabetes Mellitus Tipo 2/tratamento farmacológico , Gluconeogênese/efeitos dos fármacos , Hipoglicemiantes/administração & dosagem , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo/antagonistas & inibidores , Acetilação , Animais , Glicemia/metabolismo , Células Cultivadas , Glucose/metabolismo , Fator 4 Nuclear de Hepatócito/metabolismo , Hepatócitos/metabolismo , Ensaios de Triagem em Larga Escala , Resistência à Insulina , Camundongos , Fatores de Transcrição de p300-CBP/metabolismoRESUMO
Insulin constitutes a principal evolutionarily conserved hormonal axis for maintaining glucose homeostasis; dysregulation of this axis causes diabetes. PGC-1α (peroxisome-proliferator-activated receptor-γ coactivator-1α) links insulin signalling to the expression of glucose and lipid metabolic genes. The histone acetyltransferase GCN5 (general control non-repressed protein 5) acetylates PGC-1α and suppresses its transcriptional activity, whereas sirtuin 1 deacetylates and activates PGC-1α. Although insulin is a mitogenic signal in proliferative cells, whether components of the cell cycle machinery contribute to its metabolic action is poorly understood. Here we report that in mice insulin activates cyclin D1-cyclin-dependent kinase 4 (Cdk4), which, in turn, increases GCN5 acetyltransferase activity and suppresses hepatic glucose production independently of cell cycle progression. Through a cell-based high-throughput chemical screen, we identify a Cdk4 inhibitor that potently decreases PGC-1α acetylation. Insulin/GSK-3ß (glycogen synthase kinase 3-beta) signalling induces cyclin D1 protein stability by sequestering cyclin D1 in the nucleus. In parallel, dietary amino acids increase hepatic cyclin D1 messenger RNA transcripts. Activated cyclin D1-Cdk4 kinase phosphorylates and activates GCN5, which then acetylates and inhibits PGC-1α activity on gluconeogenic genes. Loss of hepatic cyclin D1 results in increased gluconeogenesis and hyperglycaemia. In diabetic models, cyclin D1-Cdk4 is chronically elevated and refractory to fasting/feeding transitions; nevertheless further activation of this kinase normalizes glycaemia. Our findings show that insulin uses components of the cell cycle machinery in post-mitotic cells to control glucose homeostasis independently of cell division.
Assuntos
Ciclo Celular , Ciclina D1/metabolismo , Quinase 4 Dependente de Ciclina/metabolismo , Glucose/metabolismo , Insulina/metabolismo , Transdução de Sinais , Acetilação , Aminoácidos/farmacologia , Animais , Linhagem Celular Tumoral , Núcleo Celular/metabolismo , Células Cultivadas , Ciclina D1/deficiência , Ciclina D1/genética , Quinase 4 Dependente de Ciclina/antagonistas & inibidores , Diabetes Mellitus/metabolismo , Ativação Enzimática , Jejum , Deleção de Genes , Gluconeogênese/genética , Quinase 3 da Glicogênio Sintase/metabolismo , Glicogênio Sintase Quinase 3 beta , Hepatócitos/citologia , Hepatócitos/efeitos dos fármacos , Hepatócitos/metabolismo , Histona Acetiltransferases/metabolismo , Homeostase , Humanos , Hiperglicemia/metabolismo , Hiperinsulinismo/metabolismo , Masculino , Camundongos , Fosforilação , RNA Mensageiro/análise , RNA Mensageiro/genética , Fatores de Transcrição/metabolismo , Transcrição Gênica/efeitos dos fármacosRESUMO
Hepatic glucose production (HGP) maintains blood glucose levels during fasting but can also exacerbate diabetic hyperglycemia. HGP is dynamically controlled by a signaling/transcriptional network that regulates the expression/activity of gluconeogenic enzymes. A key mediator of gluconeogenic gene transcription is PGC-1α. PGC-1α's activation of gluconeogenic gene expression is dependent upon its acetylation state, which is controlled by the acetyltransferase GCN5 and the deacetylase Sirt1. Nevertheless, whether other chromatin modifiers-particularly other sirtuins-can modulate PGC-1α acetylation is currently unknown. Herein, we report that Sirt6 strongly controls PGC-1α acetylation. Surprisingly, Sirt6 induces PGC-1α acetylation and suppresses HGP. Sirt6 depletion decreases PGC-1α acetylation and promotes HGP. These acetylation effects are GCN5 dependent: Sirt6 interacts with and modifies GCN5, enhancing GCN5's activity. Lepr(db/db) mice, an obese/diabetic animal model, exhibit reduced Sirt6 levels; ectopic re-expression suppresses gluconeogenic genes and normalizes glycemia. Activation of hepatic Sirt6 may therefore be therapeutically useful for treating insulin-resistant diabetes.
Assuntos
Gluconeogênese , Hepatócitos/metabolismo , Sirtuínas/fisiologia , Transativadores/metabolismo , Fatores de Transcrição de p300-CBP/metabolismo , Acetilação , Animais , Glicemia , Linhagem Celular , Ativação Enzimática , Expressão Gênica , Gluconeogênese/genética , Hepatócitos/enzimologia , Humanos , Fígado/enzimologia , Fígado/metabolismo , Fígado/patologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Obesos , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo , Fosforilação , Processamento de Proteína Pós-Traducional , Sirtuína 1/metabolismo , Sirtuínas/genética , Sirtuínas/metabolismo , Fatores de TranscriçãoRESUMO
The NAD(+)-dependent deacetylase SIRT1 is an evolutionarily conserved metabolic sensor of the Sirtuin family that mediates homeostatic responses to certain physiological stresses such as nutrient restriction. Previous reports have implicated fluctuations in intracellular NAD(+) concentrations as the principal regulator of SIRT1 activity. However, here we have identified a cAMP-induced phosphorylation of a highly conserved serine (S434) located in the SIRT1 catalytic domain that rapidly enhanced intrinsic deacetylase activity independently of changes in NAD(+) levels. Attenuation of SIRT1 expression or the use of a nonphosphorylatable SIRT1 mutant prevented cAMP-mediated stimulation of fatty acid oxidation and gene expression linked to this pathway. Overexpression of SIRT1 in mice significantly potentiated the increases in fatty acid oxidation and energy expenditure caused by either pharmacological ß-adrenergic agonism or cold exposure. These studies support a mechanism of Sirtuin enzymatic control through the cAMP/PKA pathway with important implications for stress responses and maintenance of energy homeostasis.
Assuntos
Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , AMP Cíclico/metabolismo , Ácidos Graxos/metabolismo , NAD/metabolismo , Transdução de Sinais , Sirtuína 1/metabolismo , Acetilação , Sequência de Aminoácidos , Animais , Células Cultivadas , Humanos , Masculino , Camundongos , Camundongos Transgênicos , Dados de Sequência Molecular , Oxirredução , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo , Fosforilação , Fosfosserina/metabolismo , Transativadores/metabolismo , Fatores de TranscriçãoRESUMO
Methionine is an essential sulfur amino acid that is engaged in key cellular functions such as protein synthesis and is a precursor for critical metabolites involved in maintaining cellular homeostasis. In mammals, in response to nutrient conditions, the liver plays a significant role in regulating methionine concentrations by altering its flux through the transmethylation, transsulfuration, and transamination metabolic pathways. A comprehensive understanding of how hepatic methionine metabolism intersects with other regulatory nutrient signaling and transcriptional events is, however, lacking. Here, we show that methionine and derived-sulfur metabolites in the transamination pathway activate the GCN5 acetyltransferase promoting acetylation of the transcriptional coactivator PGC-1α to control hepatic gluconeogenesis. Methionine was the only essential amino acid that rapidly induced PGC-1α acetylation through activating the GCN5 acetyltransferase. Experiments employing metabolic pathway intermediates revealed that methionine transamination, and not the transmethylation or transsulfuration pathways, contributed to methionine-induced PGC-1α acetylation. Moreover, aminooxyacetic acid, a transaminase inhibitor, was able to potently suppress PGC-1α acetylation stimulated by methionine, which was accompanied by predicted alterations in PGC-1α-mediated gluconeogenic gene expression and glucose production in primary murine hepatocytes. Methionine administration in mice likewise induced hepatic PGC-1α acetylation, suppressed the gluconeogenic gene program, and lowered glycemia, indicating that a similar phenomenon occurs in vivo These results highlight a communication between methionine metabolism and PGC-1α-mediated hepatic gluconeogenesis, suggesting that influencing methionine metabolic flux has the potential to be therapeutically exploited for diabetes treatment.
Assuntos
Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Gluconeogênese/efeitos dos fármacos , Histona Acetiltransferases/biossíntese , Fígado/metabolismo , Metionina/farmacologia , Fatores de Transcrição/metabolismo , Fatores de Transcrição de p300-CBP/biossíntese , Acetilação/efeitos dos fármacos , Animais , Gluconeogênese/genética , Células Hep G2 , Histona Acetiltransferases/genética , Humanos , Camundongos , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo , Fatores de Transcrição/genética , Fatores de Transcrição de p300-CBP/genéticaRESUMO
Fatty acids are essential components of the dynamic lipid metabolism in cells. Fatty acids can also signal to intracellular pathways to trigger a broad range of cellular responses. Oleic acid is an abundant monounsaturated omega-9 fatty acid that impinges on different biological processes, but the mechanisms of action are not completely understood. Here, we report that oleic acid stimulates the cAMP/protein kinase A pathway and activates the SIRT1-PGC1α transcriptional complex to modulate rates of fatty acid oxidation. In skeletal muscle cells, oleic acid treatment increased intracellular levels of cyclic adenosine monophosphate (cAMP) that turned on protein kinase A activity. This resulted in SIRT1 phosphorylation at Ser-434 and elevation of its catalytic deacetylase activity. A direct SIRT1 substrate is the transcriptional coactivator peroxisome proliferator-activated receptor γ coactivator 1-α (PGC1α), which became deacetylated and hyperactive after oleic acid treatment. Importantly, oleic acid, but not other long chain fatty acids such as palmitate, increased the expression of genes linked to fatty acid oxidation pathway in a SIRT1-PGC1α-dependent mechanism. As a result, oleic acid potently accelerated rates of complete fatty acid oxidation in skeletal muscle cells. These results illustrate how a single long chain fatty acid specifically controls lipid oxidation through a signaling/transcriptional pathway. Pharmacological manipulation of this lipid signaling pathway might provide therapeutic possibilities to treat metabolic diseases associated with lipid dysregulation.
Assuntos
Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Ácidos Graxos/metabolismo , Ácido Oleico/farmacologia , Sirtuína 1/metabolismo , Transativadores/metabolismo , Acetilação/efeitos dos fármacos , Animais , Western Blotting , Linhagem Celular , Células Cultivadas , Transferência Ressonante de Energia de Fluorescência , Camundongos , Camundongos Endogâmicos C57BL , Complexos Multiproteicos/metabolismo , Músculo Esquelético/citologia , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/metabolismo , Mutação , Oxirredução/efeitos dos fármacos , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo , Fosforilação/efeitos dos fármacos , Interferência de RNA , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Serina/genética , Serina/metabolismo , Sirtuína 1/genética , Transativadores/genética , Fatores de Transcrição , Ativação Transcricional/efeitos dos fármacosRESUMO
Mammals possess an intricate regulatory system for controlling flux through fuel utilization pathways in response to the dietary availability of particular macronutrients. Under fasting conditions, for instance, mammals initiate a whole body metabolic response that limits glucose utilization and favors fatty acid oxidation. Understanding the underlying mechanisms by which this process occurs will facilitate the development of new treatments for metabolic disorders such as type II diabetes and obesity. One of the recently identified components of the signal transduction pathway involved in metabolic reprogramming is PGC-1alpha. This transcriptional coactivator is able to coordinate the expression of a wide array of genes involved in glucose and fatty acid metabolism. The nutrient-mediated control of PGC-1alpha activity is tightly correlated with its acetylation state. In this review, we evaluate how the nutrient regulation of PGC-1alpha activity squares with the regulation of its acetylation state by the deacetylase Sirt1 and the acetyltransferase GCN5. We also propose an outline of additional experimental directives that will help to shed additional light on this very powerful transcriptional coactivator.
Assuntos
Histona Acetiltransferases/metabolismo , Sirtuína 1/metabolismo , Fatores de Transcrição/metabolismo , Acetilação , Animais , Jejum/metabolismo , Humanos , Fígado/metabolismo , Modelos Biológicos , Músculo Esquelético/metabolismo , Transdução de Sinais , Fatores de Transcrição/químicaRESUMO
Proteins in the cupin superfamily have a wide range of biological functions in archaea, bacteria and eukaryotes. Although proteins in the cupin superfamily show very low overall sequence similarity, they all contain two short but partially conserved cupin sequence motifs separated by a less conserved intermotif region that varies both in length and amino acid sequence. Furthermore, these proteins all share a common architecture described as a six-stranded ß-barrel core, and this canonical cupin or "jelly roll" ß-barrel is formed with cupin motif 1, the intermotif region, and cupin motif 2 each forming two of the core six ß-strands in the folded protein structure. The recently obtained crystal structures of cysteine dioxygenase (CDO), with contains conserved cupin motifs, show that it has the predicted canonical cupin ß-barrel fold. Although there had been no reports of CDO activity in prokaryotes, we identified a number of bacterial cupin proteins of unknown function that share low similarity with mammalian CDO and that conserve many residues in the active-site pocket of CDO. Putative bacterial CDOs predicted to have CDO activity were shown to have similar substrate specificity and kinetic parameters as eukaryotic CDOs. Information gleaned from crystal structures of mammalian CDO along with sequence information for homologs shown to have CDO activity facilitated the identification of a CDO family fingerprint motif. One key feature of the CDO fingerprint motif is that the canonical metal-binding glutamate residue in cupin motif 1 is replaced by a cysteine (in mammalian CDOs) or by a glycine (bacterial CDOs). The recent report that some putative bacterial CDO homologs are actually 3-mercaptopropionate dioxygenases suggests that the CDO family may include proteins with specificities for other thiol substrates. A paralog of CDO in mammals was also identified and shown to be the other mammalian thiol dioxygenase, cysteamine dioxygenase (ADO). A tentative fingerprint motif for ADOs, or DUF1637 family members, is proposed. In ADOs, the conserved glutamate residue in cupin motif 1 is replaced by either glycine or valine. Both ADOs and CDOs appear to represent unique clades within the cupin superfamily.
Assuntos
Cisteína Dioxigenase/metabolismo , Dioxigenases/metabolismo , Animais , Biocatálise , Cisteína Dioxigenase/química , Dioxigenases/química , Humanos , Modelos Moleculares , Estrutura Molecular , Conformação ProteicaRESUMO
The common reactions of dioxygen, superoxide, and hydroperoxides with thiolates are thought to proceed via persulfenate intermediates, yet these have never been visualized. Here we report a 1.4 A resolution crystal structure of the Fe(2+)-dependent enzyme cysteine dioxygenase (CDO) containing this putative intermediate trapped in its active site pocket. The complex raises the possibility that, distinct from known dioxygenases and proposed CDO mechanisms, the Fe-proximal oxygen atom may be involved in the primary oxidation event yielding a unique three-membered Fe-S-O cyclic intermediate. A nonpolar environment of the distal oxygen would facilitate isomerization of the persulfenate to the sulfinate product.
Assuntos
Cisteína Dioxigenase/química , Cisteína Dioxigenase/metabolismo , Animais , Domínio Catalítico , Cristalografia por Raios X , Cisteína/análogos & derivados , Cisteína/química , Cisteína/metabolismo , Técnicas In Vitro , Ferro/metabolismo , Fígado/enzimologia , Modelos Moleculares , Oxirredução , Conformação Proteica , Ratos , Ácidos Sulfênicos/química , Ácidos Sulfênicos/metabolismoRESUMO
To further define genes that are differentially expressed during cysteine deprivation and to evaluate the roles of amino acid deprivation vs. oxidative stress in the response to cysteine deprivation, we assessed gene expression in human hepatoma cells cultured in complete or cysteine-deficient medium. Overall, C3A cells responded to cysteine deprivation by activation of the eukaryotic initiation factor (eIF)2alpha kinase-mediated integrated stress response to inhibit global protein synthesis; increased expression of genes containing amino acid response elements (ASNS, ATF3, CEBPB, SLC7A11, and TRIB3); increased expression of genes for amino acid transporters (SLC7A11, SLC1A4, and SLC3A2), aminoacyl-tRNA synthetases (CARS), and, to a limited extent, amino acid metabolism (ASNS and CTH); increased expression of genes that act to suppress growth (STC2, FOXO3A, GADD45A, LNK, and INHBE); and increased expression of several enzymes that favor glutathione synthesis and maintenance of protein thiol groups (GCLC, GCLM, SLC7A11, and TXNRD1). Although GCLC, GCLM, SLC7A11, HMOX, and TXNRD1 were upregulated, most genes known to be upregulated via oxidative stress were not affected by cysteine deprivation. Because most genes known to be upregulated in response to eIF2alpha phosphorylation and activating transcription factor 4 (ATF4) synthesis were differentially expressed in response to cysteine deprivation, it is likely that many responses to cysteine deprivation are mediated, at least in part, by the general control nondepressible 2 (GCN2)/ATF4-dependent integrated stress response. This conclusion was supported by the observation of similar differential expression of a subset of genes in response to leucine deprivation. A consequence of sulfur amino acid restriction appears to be the upregulation of the cellular capacity to cope with oxidative and chemical stresses via the integrated stress response.
Assuntos
Aminoácidos/metabolismo , Cisteína/deficiência , Fator 4 Ativador da Transcrição/metabolismo , Linhagem Celular Tumoral , Meios de Cultura , Doença , Perfilação da Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Glutationa/metabolismo , Humanos , Espaço Intracelular/metabolismo , Leucina/deficiência , Fator 2 Relacionado a NF-E2/metabolismo , Análise de Sequência com Séries de Oligonucleotídeos , Estresse Oxidativo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Reprodutibilidade dos Testes , Elementos de Resposta/genética , Transdução de SinaisRESUMO
Mammalian metabolism of ingested cysteine is conducted principally within the liver. The liver tightly regulates its intracellular cysteine pool to keep levels high enough to meet the many catabolic and anabolic pathways for which cysteine is needed, but low enough to prevent toxicity. One of the enzymes the liver uses to regulate cysteine levels is CDO (cysteine dioxygenase). Catalysing the irreversible oxidation of cysteine, CDO protein is up-regulated in the liver in response to the dietary intake of cysteine. In the present study, we have evaluated the contribution of the ubiquitin-26 S proteasome pathway to the diet-induced changes in CDO half-life. In the living rat, inhibition of the proteasome with PS1 (proteasome inhibitor 1) dramatically stabilized CDO in the liver under dietary conditions that normally favour its degradation. Ubiquitinated CDO intermediates were also seen to accumulate in the liver. Metabolic analyses showed that PS1 had a significant effect on sulphoxidation flux secondary to the stabilization of CDO but no significant effect on the intracellular cysteine pool. Finally, by a combination of in vitro hepatocyte culture and in vivo whole animal studies, we were able to attribute the changes in CDO stability specifically to cysteine rather than the metabolite 2-mercaptoethylamine (cysteamine). The present study represents the first demonstration of regulated ubiquitination and degradation of a protein in a living mammal, inhibition of which had dramatic effects on cysteine catabolism.
Assuntos
Cisteína Dioxigenase/metabolismo , Cisteína/metabolismo , Complexo de Endopeptidases do Proteassoma/metabolismo , Ubiquitina/metabolismo , Animais , Células Cultivadas , Cisteamina/farmacologia , Hepatócitos/metabolismo , Fígado/enzimologia , Masculino , Oligopeptídeos/farmacologia , Inibidores de Proteassoma , Ratos , Ratos Sprague-DawleyRESUMO
The enzymes of the transsulfuration pathway also have the capacity to catalyze the desulfhydration of cysteine. Recent studies demonstrate a role of the transsulfuration enzymes, cystathionine gamma-lyase and cystathionine beta-synthase, in catalyzing the desulfhydration of cysteine in brain and smooth muscle. The H2S produced from cysteine functions as a neuromodulator and smooth muscle relaxant. In glutamatergic neurons, the production of H2S by cystathionine beta-synthase enhances N-methyl-D-aspartate (NMDA) receptor-mediated currents. In smooth muscle cells, H2S produced by cystathionine gamma-lyase enhances the outward flux of potassium by opening potassium channels, leading to hyperpolarization of membrane potential and smooth muscle relaxation.
Assuntos
Cisteína/metabolismo , Sulfeto de Hidrogênio/metabolismo , Relaxamento Muscular/fisiologia , Músculo Liso/fisiologia , Animais , Encéfalo/metabolismo , Cistationina beta-Sintase/metabolismo , Cistationina gama-Liase/metabolismo , HumanosRESUMO
Lipid deposition in the liver is associated with metabolic disorders including fatty liver disease, type II diabetes, and hepatocellular cancer. The enzymes acetyl-CoA carboxylase 1 (ACC1) and ACC2 are powerful regulators of hepatic fat storage; therefore, their inhibition is expected to prevent the development of fatty liver. In this study we generated liver-specific ACC1 and ACC2 double knockout (LDKO) mice to determine how the loss of ACC activity affects liver fat metabolism and whole-body physiology. Characterization of LDKO mice revealed unexpected phenotypes of increased hepatic triglyceride and decreased fat oxidation. We also observed that chronic ACC inhibition led to hyper-acetylation of proteins in the extra-mitochondrial space. In sum, these data reveal the existence of a compensatory pathway that protects hepatic fat stores when ACC enzymes are inhibited. Furthermore, we identified an important role for ACC enzymes in the regulation of protein acetylation in the extra-mitochondrial space.
RESUMO
The dynamics of mitochondrial biogenesis and function is a complex interplay of cellular and molecular processes that ultimately shape bioenergetics capacity. Mitochondrial mass, by itself, represents the net balance between rates of biogenesis and degradation. Mitochondrial biogenesis is dependent on different signaling cascades and transcriptional complexes that promote the formation and assembly of mitochondria--a process that is heavily dependent on timely and coordinated transcriptional control of genes encoding for mitochondrial proteins. In this article, we discuss the major signals and transcriptional complexes, programming mitochondrial biogenesis, and bioenergetic activity. This regulatory network represents a new therapeutic window into the treatment of the wide spectrum of mitochondrial and neurodegenerative diseases characterized by dysregulation of mitochondrial dynamics and bioenergetic deficiencies.
Assuntos
Mitocôndrias/metabolismo , Renovação Mitocondrial , Proteínas Nucleares/metabolismo , Transdução de Sinais , Metabolismo Energético , Regulação da Expressão Gênica , Humanos , Mitocôndrias/fisiologia , Doenças Mitocondriais/genética , Doenças Mitocondriais/terapia , Proteínas Mitocondriais/metabolismo , Modelos BiológicosRESUMO
The 7 mammalian sirtuin proteins compose a protective cavalry of enzymes that can be invoked by cells to aid in the defense against a vast array of stressors. The pathologies associated with aging, such as metabolic syndrome, neurodegeneration, and cancer, are either caused by or exacerbated by a lifetime of chronic stress. As such, the activation of sirtuin proteins could provide a therapeutic approach to buffer against chronic stress and ameliorate age-related decline. Here we review experimental evidence both for and against this proposal, as well as the implications that isoform-specific sirtuin activation may have for healthy aging in humans.
Assuntos
Envelhecimento/metabolismo , Sirtuínas/fisiologia , Envelhecimento/patologia , Animais , Restrição Calórica , Doenças Cardiovasculares/metabolismo , Doenças Cardiovasculares/fisiopatologia , Humanos , Doenças Metabólicas/metabolismo , Doenças Metabólicas/fisiopatologia , Neoplasias/metabolismo , Neoplasias/fisiopatologia , Doenças Neurodegenerativas/metabolismo , Doenças Neurodegenerativas/fisiopatologia , Sirtuínas/metabolismoRESUMO
Tumor-initiating cells (TICs) are thought to be critical for promoting tumorigenesis. In a recent Cell article, Zhang and colleagues found that non-small cell lung cancer TICs overexpress the metabolic enzyme glycine decarboxylase, which leads to increases in pyrimidine synthesis and is critical for proliferation and tumor initiation.
Assuntos
Cisteína Dioxigenase/metabolismo , Complexo de Endopeptidases do Proteassoma/metabolismo , Ubiquitina/metabolismo , Animais , Cromatografia Líquida de Alta Pressão , Dieta , Proteínas Alimentares , Masculino , Inibidores de Proteassoma , Distribuição Aleatória , Ratos , Ratos Sprague-Dawley , Taurina/análogos & derivados , Taurina/metabolismo , Distribuição TecidualAssuntos
Cisteamina/metabolismo , Dioxigenases/metabolismo , Taurina/análogos & derivados , Amidoidrolases , Animais , Moléculas de Adesão Celular/genética , Moléculas de Adesão Celular/metabolismo , Cromatografia Líquida de Alta Pressão , Dieta , Proteínas Alimentares , Proteínas Ligadas por GPI , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Distribuição Aleatória , Ratos , Ratos Sprague-Dawley , Taurina/metabolismo , Distribuição TecidualRESUMO
Cysteine dioxygenase is an iron (Fe(2+))-dependent thiol dioxygenase that uses molecular oxygen to oxidize the sulfhydryl group of cysteine to generate 3-sulfinoalanine (commonly called cysteinesulfinic acid). Cysteine dioxygenase activity is routinely assayed by measuring cysteinesulfinate formation from substrate L-cysteine at pH 6.1 in the presence of ferrous ions to saturate the enzyme with metal cofactor, a copper chelator to diminish substrate oxidation, and hydroxylamine to inhibit pyridoxal 5'-phosphate-dependent degradation of product. The amount of cysteine dioxygenase may be measured by immunoblotting. Upon SDS-PAGE, cysteine dioxygenase can be separated into two major bands, with the upper band representing the 23-kDa protein and the lower band representing the mature enzyme that has undergone formation of an internal thioether cross link in the active site. Formation of this cross link is dependent upon the catalytic turnover of substrate and produces an enzyme with a higher catalytic efficiency and catalytic half-life.