RESUMO
The autophagy cargo receptor p62 facilitates the condensation of misfolded, ubiquitin-positive proteins and their degradation by autophagy, but the molecular mechanism of p62 signaling to the core autophagy machinery is unclear. Here, we show that disordered residues 326-380 of p62 directly interact with the C-terminal region (CTR) of FIP200. Crystal structure determination shows that the FIP200 CTR contains a dimeric globular domain that we designated the "Claw" for its shape. The interaction of p62 with FIP200 is mediated by a positively charged pocket in the Claw, enhanced by p62 phosphorylation, mutually exclusive with the binding of p62 to LC3B, and it promotes degradation of ubiquitinated cargo by autophagy. Furthermore, the recruitment of the FIP200 CTR slows the phase separation of ubiquitinated proteins by p62 in a reconstituted system. Our data provide the molecular basis for a crosstalk between cargo condensation and autophagosome formation.
Assuntos
Autofagossomos/metabolismo , Conformação Proteica , Proteínas Tirosina Quinases/química , Proteína Sequestossoma-1/química , Autofagossomos/química , Autofagia/genética , Proteínas Relacionadas à Autofagia , Cristalografia por Raios X , Humanos , Proteínas Associadas aos Microtúbulos/química , Proteínas Associadas aos Microtúbulos/genética , Mapas de Interação de Proteínas/genética , Proteínas Tirosina Quinases/genética , Proteólise , Proteína Sequestossoma-1/genética , Transdução de Sinais/genética , Ubiquitina/química , Ubiquitina/genéticaRESUMO
Mutation of C9orf72 is the most prevalent defect associated with amyotrophic lateral sclerosis and frontotemporal degeneration1. Together with hexanucleotide-repeat expansion2,3, haploinsufficiency of C9orf72 contributes to neuronal dysfunction4-6. Here we determine the structure of the C9orf72-SMCR8-WDR41 complex by cryo-electron microscopy. C9orf72 and SMCR8 both contain longin and DENN (differentially expressed in normal and neoplastic cells) domains7, and WDR41 is a ß-propeller protein that binds to SMCR8 such that the whole structure resembles an eye slip hook. Contacts between WDR41 and the DENN domain of SMCR8 drive the lysosomal localization of the complex in conditions of amino acid starvation. The structure suggested that C9orf72-SMCR8 is a GTPase-activating protein (GAP), and we found that C9orf72-SMCR8-WDR41 acts as a GAP for the ARF family of small GTPases. These data shed light on the function of C9orf72 in normal physiology, and in amyotrophic lateral sclerosis and frontotemporal degeneration.
Assuntos
Esclerose Lateral Amiotrófica/genética , Proteínas Relacionadas à Autofagia/química , Proteína C9orf72/química , Proteína C9orf72/genética , Proteínas de Transporte/química , Microscopia Crioeletrônica , Demência Frontotemporal/genética , Haploinsuficiência , Complexos Multiproteicos/química , Proteínas Adaptadoras de Transdução de Sinal/química , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Esclerose Lateral Amiotrófica/metabolismo , Proteínas Relacionadas à Autofagia/deficiência , Proteínas Relacionadas à Autofagia/metabolismo , Proteínas Relacionadas à Autofagia/ultraestrutura , Proteína C9orf72/metabolismo , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Proteínas de Transporte/ultraestrutura , Demência Frontotemporal/metabolismo , Humanos , Lisossomos/metabolismo , Modelos Moleculares , Complexos Multiproteicos/genética , Complexos Multiproteicos/metabolismo , Complexos Multiproteicos/ultraestrutura , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Mutação , Domínios ProteicosRESUMO
The lysosomal membrane is the locus for sensing cellular nutrient levels, which are transduced to mTORC1 via the Rag GTPases and the Ragulator complex. The crystal structure of the five-subunit human Ragulator at 1.4 Å resolution was determined. Lamtor1 wraps around the other four subunits to stabilize the assembly. The Lamtor2:Lamtor3 dimer stacks upon Lamtor4:Lamtor5 to create a platform for Rag binding. Hydrogen-deuterium exchange was used to map the Rag binding site to the outer face of the Lamtor2:Lamtor3 dimer and to the N-terminal intrinsically disordered region of Lamtor1. EM was used to reconstruct the assembly of the full-length RagAGTP:RagCGDP dimer bound to Ragulator at 16 Å resolution, revealing that the G-domains of the Rags project away from the Ragulator core. The combined structural model shows how Ragulator functions as a platform for the presentation of active Rags for mTORC1 recruitment, and might suggest an unconventional mechanism for Rag GEF activity.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/química , Alvo Mecanístico do Complexo 1 de Rapamicina/química , Proteínas Monoméricas de Ligação ao GTP/química , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Sítios de Ligação , Proteínas de Transporte/química , Proteínas de Transporte/metabolismo , Fatores de Troca do Nucleotídeo Guanina/química , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Humanos , Peptídeos e Proteínas de Sinalização Intracelular , Alvo Mecanístico do Complexo 1 de Rapamicina/genética , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Microscopia Eletrônica , Simulação de Acoplamento Molecular , Proteínas Monoméricas de Ligação ao GTP/genética , Proteínas Monoméricas de Ligação ao GTP/metabolismo , Ligação Proteica , Domínios e Motivos de Interação entre Proteínas , Multimerização Proteica , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Relação Estrutura-AtividadeRESUMO
A new method is applied to synthesize hispidulin, a natural flavone with a broad spectrum of biological activities. Hispidulin exhibits inhibitory activity against the oncogenic protein kinase Pim-1. Crystallographic analysis of Pim-1 bound to hispidulin reveals a binding mode distinct from that of quercetin, suggesting that the binding potency of flavonoids is determined by their hydrogen-bonding interactions with the hinge region of the kinase. Overall, this work may facilitate construction of a library of hispidulin-derived compounds for investigating the structure-activity relationship of flavone-based Pim-1 inhibitors.
Assuntos
Flavonas/síntese química , Flavonas/farmacologia , Proteínas Proto-Oncogênicas c-pim-1/antagonistas & inibidores , Flavonas/química , Estrutura Molecular , Proteínas Proto-Oncogênicas c-pim-1/metabolismo , Quercetina/química , Relação Estrutura-AtividadeRESUMO
We have asked young scientists who spoke at our recent Cell Symposium "Structural biology from the nanoscale to cellular mesoscale" in Huangshan, China to tell us more about themselves and their exciting research in this collection of Voices.
Assuntos
Biologia Molecular , ChinaRESUMO
Proteolysis-targeting chimeras (PROTACs) selectively eliminate detrimental proteins by exploiting the ubiquitin-proteasome system (UPS), representing a promising therapeutic strategy against various diseases. Effective adaptations of degradation signal sequences and E3 ligases for PROTACs remain limited. Here, we employed three amino acidsâGly, Pro, and Lysâas the ligand to recruit the corresponding E3 ligases: CRL2ZYG11B/ZER1, GID4, and UBRs, to degrade EML4-ALK and mutant EGFR, two oncogenic drivers in NSCLC. We found that the extent of EML4-ALK and EGFR reduction can be easily fine-tuned by using different degradation signals. These amino acid-based PROTACs, termed AATacs, hindered proliferation and induced cell cycle arrest and apoptosis of NSCLC cells in vitro. Compared to other PROTACs, AATacs are small, interchangeable but with different degradation efficiency. Our study further expands the repertoire of E3 ligases and their ligands for PROTAC application, improving the versatility and utility of targeted protein degradation for therapeutic purposes.
Assuntos
Aminoácidos , Carcinoma Pulmonar de Células não Pequenas , Neoplasias Pulmonares , Proteólise , Ubiquitina-Proteína Ligases , Humanos , Carcinoma Pulmonar de Células não Pequenas/tratamento farmacológico , Carcinoma Pulmonar de Células não Pequenas/patologia , Carcinoma Pulmonar de Células não Pequenas/metabolismo , Proteólise/efeitos dos fármacos , Neoplasias Pulmonares/tratamento farmacológico , Neoplasias Pulmonares/patologia , Neoplasias Pulmonares/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Aminoácidos/farmacologia , Aminoácidos/metabolismo , Aminoácidos/química , Antineoplásicos/farmacologia , Antineoplásicos/química , Antineoplásicos/síntese química , Proliferação de Células/efeitos dos fármacos , Linhagem Celular Tumoral , Receptores ErbB/metabolismo , Receptores ErbB/antagonistas & inibidores , Apoptose/efeitos dos fármacos , Quimera de Direcionamento de ProteóliseRESUMO
CULLIN-RING ligases constitute the largest group of E3 ubiquitin ligases. While some CULLIN family members recruit adapters before engaging further with different substrate receptors, homo-dimeric BTB-Kelch family proteins combine adapter and substrate receptor into a single polypeptide for the CULLIN3 family. However, the entire structural assembly and molecular details have not been elucidated to date. Here, we present a cryo-EM structure of the CULLIN3RBX1 in complex with Kelch-like protein 22 (KLHL22) and a mitochondrial glutamate dehydrogenase complex I (GDH1) at 3.06 Å resolution. The structure adopts a W-shaped architecture formed by E3 ligase dimers. Three CULLIN3KLHL22-RBX1 dimers were found to be dynamically associated with a single GDH1 hexamer. CULLIN3KLHL22-RBX1 ligase mediated the polyubiquitination of GDH1 in vitro. Together, these results enabled the establishment of a structural model for understanding the complete assembly of BTB-Kelch proteins with CULLIN3 and how together they recognize oligomeric substrates and target them for ubiquitination.
Assuntos
Proteínas Culina , Ubiquitina-Proteína Ligases , Ubiquitina-Proteína Ligases/metabolismo , Proteínas Culina/metabolismo , Ligação Proteica , Microscopia Crioeletrônica , Estrutura Terciária de Proteína , Proteínas de Transporte/metabolismo , UbiquitinaçãoRESUMO
AMBRA1 is a tumor suppressor protein that functions as a substrate receptor of the ubiquitin conjugation system with roles in autophagy and the cell cycle regulatory network. The intrinsic disorder of AMBRA1 has thus far precluded its structural determination. To solve this problem, we analyzed the dynamics of AMBRA1 using hydrogen deuterium exchange mass spectrometry (HDX-MS). The HDX results indicated that AMBRA1 is a highly flexible protein and can be stabilized upon interaction with DDB1, the adaptor of the Cullin4A/B E3 ligase. Here, we present the cryo-EM structure of AMBRA1 in complex with DDB1 at 3.08 Å resolution. The structure shows that parts of the N- and C-terminal structural regions in AMBRA1 fold together into the highly dynamic WD40 domain and reveals how DDB1 engages with AMBRA1 to create a binding scaffold for substrate recruitment. The N-terminal helix-loop-helix motif and WD40 domain of AMBRA1 associate with the double-propeller fold of DDB1. We also demonstrate that DDB1 binding-defective AMBRA1 mutants prevent ubiquitination of the substrate Cyclin D1 in vitro and increase cell cycle progression. Together, these results provide structural insights into the AMBRA1-ubiquitin ligase complex and suggest a mechanism by which AMBRA1 acts as a hub involved in various physiological processes.
Assuntos
Proteínas de Transporte , Proteínas de Ligação a DNA , Proteínas de Ligação a DNA/metabolismo , Proteínas de Transporte/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Pontos de Checagem do Ciclo Celular , Ubiquitina/metabolismoRESUMO
Mutation of C9ORF72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontal temporal degeneration (FTD), which is attributed to both a gain and loss of function. C9orf72 forms a complex with SMCR8 and WDR41, which was reported to have GTPase activating protein activity toward ARF proteins, RAB8A, and RAB11A. We determined the cryo-EM structure of ARF1-GDP-BeF3- bound to C9orf72:SMCR8:WDR41. The SMCR8longin and C9orf72longin domains form the binding pocket for ARF1. One face of the C9orf72longin domain holds ARF1 in place, while the SMCR8longin positions the catalytic finger Arg147 in the ARF1 active site. Mutations in interfacial residues of ARF1 and C9orf72 reduced or eliminated GAP activity. RAB8A GAP required ~10-fold higher concentrations of the C9orf72 complex than for ARF1. These data support a specific function for the C9orf72 complex as an ARF GAP. The structure also provides a model for the active forms of the longin domain GAPs of FLCN and NPRL2 that regulate the Rag GTPases of the mTORC1 pathway.
Assuntos
Esclerose Lateral Amiotrófica/genética , Proteínas Relacionadas à Autofagia/metabolismo , Proteína C9orf72/metabolismo , Proteínas de Transporte/metabolismo , Demência Frontotemporal/genética , Proteínas rab de Ligação ao GTP/metabolismo , Fator 1 de Ribosilação do ADP/metabolismo , Proteínas Relacionadas à Autofagia/genética , Proteína C9orf72/genética , Proteínas de Transporte/genética , Microscopia Crioeletrônica , Humanos , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Complexos Multiproteicos/genética , Estrutura Terciária de Proteína/genéticaRESUMO
Macroautophagy/autophagy mediates the degradation of ubiquitinated aggregated proteins within lysosomes in a process known as aggrephagy. The cargo receptor SQSTM1/p62 condenses aggregated proteins into larger structures and links them to the nascent autophagosomal membrane (phagophore). How the condensation reaction and autophagosome formation are coupled is unclear. We recently discovered that a region of SQSTM1 containing its LIR motif directly interacts with RB1CC1/FIP200, a protein acting at early stages of autophagosome formation. Determination of the structure of the C-terminal region of RB1CC1 revealed a claw-shaped domain. Using a structure-function approach, we show that the interaction of SQSTM1 with the RB1CC1 claw domain is crucial for the productive recruitment of the autophagy machinery to ubiquitin-positive condensates and their subsequent degradation by autophagy. We also found that concentrated Atg8-family proteins on the phagophore displace RB1CC1 from SQSTM1, suggesting an intrinsic directionality in the process of autophagosome formation. Ultimately, our study reveals how the interplay of SQSTM1 and RB1CC1 couples cargo condensation to autophagosome formation.
Assuntos
Proteínas Relacionadas à Autofagia/metabolismo , Autofagia , Proteína Sequestossoma-1/metabolismo , Ubiquitina/metabolismo , Animais , Autofagossomos/metabolismo , Humanos , Modelos Biológicos , Ligação ProteicaRESUMO
Peptidoglycan (PG) is a highly cross-linked, protective mesh-like sacculus that surrounds the bacterial cytoplasmic membrane. Expansion of PG is tightly coupled to growth of a bacterial cell and requires hydrolases to cleave the cross-links for insertion of nascent PG material. In Escherichia coli, a proteolytic system comprising the periplasmic PDZ-protease Prc and the lipoprotein adaptor NlpI contributes to PG enlargement by regulating cellular levels of MepS, a cross-link-specific hydrolase. Here, we demonstrate how NlpI binds Prc to facilitate the degradation of its substrate MepS by structural and mutational analyses. An NlpI homodimer binds two molecules of Prc and forms three-sided MepS-docking cradles using its tetratricopeptide repeats. Prc forms a monomeric bowl-shaped structure with a lid-like PDZ domain connected by a substrate-sensing hinge that recognizes the bound C terminus of the substrate. In summary, our study reveals mechanistic details of protein degradation by the PDZ-protease Prc bound to its cognate adaptor protein.
Assuntos
Endopeptidases/metabolismo , Proteínas de Escherichia coli/metabolismo , Escherichia coli/metabolismo , Lipoproteínas/metabolismo , Sequência de Aminoácidos , Cristalografia por Raios X , Cisteína Endopeptidases/química , Cisteína Endopeptidases/genética , Cisteína Endopeptidases/metabolismo , Endopeptidases/química , Endopeptidases/genética , Escherichia coli/genética , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/genética , Lipoproteínas/química , Lipoproteínas/genética , Simulação de Acoplamento Molecular , Mutação , Domínios PDZ , Peptidoglicano/química , Peptidoglicano/metabolismo , Periplasma/metabolismo , Ligação Proteica , Estrutura Secundária de Proteína , Proteólise , Homologia de Sequência de AminoácidosRESUMO
The Lon AAA+ protease (LonA) is an evolutionarily conserved protease that couples the ATPase cycle into motion to drive substrate translocation and degradation. A hallmark feature shared by AAA+ proteases is the stimulation of ATPase activity by substrates. Here we report the structure of LonA bound to three ADPs, revealing the first AAA+ protease assembly where the six protomers are arranged alternately in nucleotide-free and bound states. Nucleotide binding induces large coordinated movements of conserved pore loops from two pairs of three non-adjacent protomers and shuttling of the proteolytic groove between the ATPase site and a previously unknown Arg paddle. Structural and biochemical evidence supports the roles of the substrate-bound proteolytic groove in allosteric stimulation of ATPase activity and the conserved Arg paddle in driving substrate degradation. Altogether, this work provides a molecular framework for understanding how ATP-dependent chemomechanical movements drive allosteric processes for substrate degradation in a major protein-destruction machine.
Assuntos
Proteases Dependentes de ATP/química , Sítio Alostérico , Proteínas Mitocondriais/química , Proteases Dependentes de ATP/metabolismo , Difosfato de Adenosina/metabolismo , Trifosfato de Adenosina/metabolismo , Regulação Alostérica , Proteínas Mitocondriais/metabolismo , Simulação de Acoplamento Molecular , Simulação de Dinâmica MolecularRESUMO
In Saccharomyces cerevisiae, a constitutive biosynthetic transport pathway, termed the cytoplasm-to-vacuole targeting (Cvt) pathway, sequesters precursor aminopeptidase I (prApe1) dodecamers in the form of a large complex into a Cvt vesicle using autophagic machinery, targeting it into the vacuole (the yeast lysosome) where it is proteolytically processed into its mature form, Ape1, by removal of an amino-terminal 45-amino acid propeptide. prApe1 is thought to serve as a scaffolding cargo critical for the assembly of the Cvt vesicle by presenting the propeptide to mediate higher-ordered complex formation and autophagic receptor recognition. Here we report the X-ray crystal structure of Ape1 at 2.5 Å resolution and reveal its dodecameric architecture consisting of dimeric and trimeric units, which associate to form a large tetrahedron. The propeptide of prApe1 exhibits concentration-dependent oligomerization and forms a stable tetramer. Structure-based mutagenesis demonstrates that disruption of the inter-subunit interface prevents dodecameric assembly and vacuolar targeting in vivo despite the presence of the propeptide. Furthermore, by examining the vacuolar import of propeptide-fused exogenous protein assemblies with different quaternary structures, we found that 3-dimensional spatial distribution of propeptides presented by a scaffolding cargo is essential for the assembly of the Cvt vesicle for vacuolar delivery. This study describes a molecular framework for understanding the mechanism of Cvt or autophagosomal biogenesis in selective macroautophagy.
Assuntos
Aminopeptidases/metabolismo , Autofagia , Vesículas Citoplasmáticas/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/citologia , Aminopeptidases/química , Cristalografia por Raios X , Vesículas Citoplasmáticas/ultraestrutura , Modelos Moleculares , Mutação , Peptídeos/química , Multimerização Proteica , Proteínas Recombinantes de Fusão/metabolismo , Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/ultraestrutura , Proteínas de Saccharomyces cerevisiae/química , Frações Subcelulares/metabolismo , Vacúolos/metabolismoRESUMO
PYNOD is a novel protein belonging to a large family of proteins containing the nucleotide-binding and oligomerization domain (NOD) involved in inflammation and apoptosis. Human PYNOD inhibits inflammatory response mediated by caspase-1 and apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC). Here we report the (1)H, (13)C and (15)N resonance assignments and secondary structure identification of the pyrin domain (PYD) of human PYNOD as the first step towards elucidating the structural basis of the anti-inflammatory activity of PYNOD.
Assuntos
Proteínas de Transporte/química , Ressonância Magnética Nuclear Biomolecular , Prótons , Proteínas Adaptadoras de Transdução de Sinal , Proteínas Reguladoras de Apoptose , Isótopos de Carbono , Humanos , Isótopos de Nitrogênio , Estrutura Terciária de ProteínaRESUMO
NLRPs (Nucleotide-binding domain, leucine-rich repeat and pyrin domain containing proteins) are a family of pattern-recognition receptors (PRRs) that sense intracellular microbial components and endogenous stress signals. NLRP10 (also known as PYNOD) is a unique NLRP member characterized by a lack of the putative ligand-binding leucine-rich repeat domain. Recently, human NLRP10 has been shown to inhibit the self-association of ASC into aggregates and ASC-mediated procaspase-1 processing. However, such activities are not found in mouse NLRP10. Here we report the solution structure and dynamics of human NLRP10 pyrin domain (PYD), whose helix H3 and loop H2-H3 adopt a conformation distinct from those of mouse NLRP10. Docking studies show that human and mouse NLRP10 PYDs may interact differently with ASC PYD. These results provide a possible structural explanation for the contrasting effect of NLRP10 on ASC aggregation in human cells versus mouse models. Finally, we also provide evidence that in human NLRP10 the PYD domain may not interact with the NOD domain to regulate its intrinsic nucleotide hydrolysis activity.
Assuntos
Trifosfato de Adenosina/química , Proteínas de Transporte/química , Proteínas do Citoesqueleto/química , Guanosina Trifosfato/química , Proteínas Adaptadoras de Transdução de Sinal , Sequência de Aminoácidos , Animais , Proteínas Reguladoras de Apoptose , Proteínas Adaptadoras de Sinalização CARD , Proteínas de Transporte/genética , Escherichia coli/genética , Escherichia coli/metabolismo , Humanos , Hidrólise , Camundongos , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , Dados de Sequência Molecular , Domínios e Motivos de Interação entre Proteínas , Estrutura Secundária de Proteína , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Especificidade da EspécieRESUMO
Oxidative stress has been considered as a major cause of cellular injuries in various clinical abnormalities. One of the possible ways to prevent reactive oxygen species (ROS)-mediated cellular injury is dietary or pharmaceutical therapies to augment the endogenous antioxidant defense capacity. The present study found that 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone (DMC), a chalcone isolated from the buds of Cleistocalyx operculatus, possessed cytoprotective activity in PC12 cells treated with H(2)O(2). The results showed that DMC could effectively increase cell viability [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) reduction], decrease the cell apoptotic percentage [annexin V/propidium iodide (AV/PI) assay], prevent the membrane from damage [lactate dehydrogenase (LDH) release], scavenge ROS formation, reduce caspase-3 activity, and attenuate the decrease of mitochondrial membrane potential (MMP) in PC12 cells treated with H(2)O(2). Meanwhile, DMC increased the catalytic activity of superoxide dismutase (SOD) and the cellular amount of glutathione (GSH), decreased the cellular amount of malondialdehyde (MDA), and decreased the production of lipid peroxidation in PC12 cells treated with H(2)O(2).
Assuntos
Chalconas/farmacologia , Peróxido de Hidrogênio/toxicidade , Myrtaceae/química , Extratos Vegetais/farmacologia , Substâncias Protetoras/farmacologia , Animais , Malondialdeído/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Células PC12 , RatosRESUMO
Oxidative stress has been considered as a major cause of cellular injuries in a variety of clinical abnormalities. One of the plausible ways to prevent the reactive oxygen species (ROS)-mediated cellular injury is dietary or pharmaceutical augmentation of endogenous antioxidant defense capacity. In this study, we investigated the protective actions of citrus flavanones naringin and nobiletin against the cytotoxicity induced by exposure to hydrogen peroxide (H(2)O(2)) (150µM, 3h) in PC12 cells. The results showed that naringin and nobiletin inhibited the decrease of cell viability (MTT reduction), prevented membrane damage (LDH release), scavenged ROS formation, reduced caspase-3 activity, and attenuated the decrease of mitochondrial membrane potential (MMP), respectively, in H(2)O(2)-induced PC12 cells. Meanwhile, naringin and nobiletin increased superoxide dismutase (SOD) and glutathione (GSH) activity, while decreased malondialdehyde (MDA), the production of lipid peroxidation, in H(2)O(2)-induced PC12 cells. In addition, the percentage of cells undergoing H(2)O(2)-induced apoptosis was decreased in the presence of naringin and nobiletin. These results first demonstrate that naringin and nobiletin, even at physiological concentrations, have neuroprotective effects against H(2)O(2)-induced cytotoxicity in PC12 cells. All the above results suggest that these dietary antioxidants are potential candidates for use in the intervention for neurodegenerative diseases.
Assuntos
Citoproteção/efeitos dos fármacos , Flavanonas/farmacologia , Flavonas/farmacologia , Peróxido de Hidrogênio/farmacologia , Estresse Oxidativo/efeitos dos fármacos , Animais , Apoptose/efeitos dos fármacos , Caspase 3/metabolismo , Células PC12 , Ratos , Espécies Reativas de Oxigênio/metabolismoRESUMO
Wogonin from Scutellaria baicalensis, was demonstrated to increase nitric oxide (NO) in the murine macrophage cell line RAW 264.7. It is our aim to investigate the modulatory effect of wogonin on tumor necrosis factor-alpha (TNF-alpha) gene expression. By using RAW 264.7 as an in vitro model, the effects of wogonin on inducible nitric oxide synthase (NOS2) and TNF-alpha gene expression were evaluated by ELISA and reverse transcribed polymerase chain reaction (RT-PCR). Aspirin and H7 were used to determine the possible signal transduction pathways. The results showed that wogonin at the concentration of 10 (-5) M and 10 (-6) M up-regulated NOS2 gene expression in RAW 264.7 cells. Besides, wogonin up-regulated the gene expression of TNF-alpha, in terms of TNF-alpha secretion and transcription, in a dose dependent manner. The fact that aspirin but not H7 blocks the enhancing effect suggests that NF-kappaB might be involved in wogonin-enhanced TNF-alpha gene expression. We conclude that a low concentration of wogonin up-regulates NOS2 and TNF-alpha gene expression through NF-kappaB pathway.