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1.
Mol Cell ; 80(1): 127-139.e6, 2020 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-33007253

RESUMO

Human spliceosomes contain numerous proteins absent in yeast, whose functions remain largely unknown. Here we report a 3D cryo-EM structure of the human spliceosomal C complex at 3.4 Å core resolution and 4.5-5.7 Å at its periphery, and aided by protein crosslinking we determine its molecular architecture. Our structure provides additional insights into the spliceosome's architecture between the catalytic steps of splicing, and how proteins aid formation of the spliceosome's catalytically active RNP (ribonucleoprotein) conformation. It reveals the spatial organization of the metazoan-specific proteins PPWD1, WDR70, FRG1, and CIR1 in human C complexes, indicating they stabilize functionally important protein domains and RNA structures rearranged/repositioned during the Bact to C transition. Structural comparisons with human Bact, C∗, and P complexes reveal an intricate cascade of RNP rearrangements during splicing catalysis, with intermediate RNP conformations not found in yeast, and additionally elucidate the structural basis for the sequential recruitment of metazoan-specific spliceosomal proteins.


Assuntos
Fatores de Processamento de RNA/química , Fatores de Processamento de RNA/metabolismo , Spliceossomos/metabolismo , Animais , Catálise , Células HeLa , Humanos , Íntrons/genética , Modelos Moleculares , Complexos Multiproteicos/metabolismo , Complexos Multiproteicos/ultraestrutura , Ligação Proteica , Estabilidade Proteica , RNA/química , RNA/metabolismo , Ribonucleoproteínas/metabolismo , Saccharomyces cerevisiae/metabolismo , Especificidade da Espécie , Fatores de Tempo
2.
Int Heart J ; 61(5): 1034-1040, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32999190

RESUMO

Low-density lipoprotein (LDL) particles are known to be atherogenic agents in coronary artery diseases. They adjust to other electronegative forms and can be the subject for the enhancement of inflammatory events in vessel subendothelial spaces. The LDL uptake is related to the membrane scavenger receptors, including LDL receptor (LDLR). The LDLR expression is closely associated with LDL uptake and occurrence of diseases, such as atherosclerotic cardiovascular diseases. Our findings identified USP16 as a novel regulator of LDLR due to its ability to prevent ubiquitylation-dependent LDLR degradation, further promoting the uptake of LDL. The enhancement of USP16-mediated deubiquitination andthe suppressive degradation of the LDLR cause the presentation of a potential strategy to increase LDL cholesterol clearance.


Assuntos
Receptores de LDL/metabolismo , Ubiquitina Tiolesterase/metabolismo , Ubiquitinação , Células HeLa , Humanos , Lipoproteínas LDL/metabolismo , Processamento de Proteína Pós-Traducional
3.
Nat Commun ; 11(1): 4940, 2020 10 02.
Artigo em Inglês | MEDLINE | ID: mdl-33009411

RESUMO

The HUSH complex represses retroviruses, transposons and genes to maintain the integrity of vertebrate genomes. HUSH regulates deposition of the epigenetic mark H3K9me3, but how its three core subunits - TASOR, MPP8 and Periphilin - contribute to assembly and targeting of the complex remains unknown. Here, we define the biochemical basis of HUSH assembly and find that its modular architecture resembles the yeast RNA-induced transcriptional silencing complex. TASOR, the central HUSH subunit, associates with RNA processing components. TASOR is required for H3K9me3 deposition over LINE-1 repeats and repetitive exons in transcribed genes. In the context of previous studies, this suggests that an RNA intermediate is important for HUSH activity. We dissect the TASOR and MPP8 domains necessary for transgene repression. Structure-function analyses reveal TASOR bears a catalytically-inactive PARP domain necessary for targeted H3K9me3 deposition. We conclude that TASOR is a multifunctional pseudo-PARP that directs HUSH assembly and epigenetic regulation of repetitive genomic targets.


Assuntos
Elementos de DNA Transponíveis/genética , Epigênese Genética , Complexos Multiproteicos/metabolismo , Proteínas Nucleares/metabolismo , Poli(ADP-Ribose) Polimerases/metabolismo , Sequência de Aminoácidos , Antígenos de Neoplasias/metabolismo , Sítios de Ligação , Éxons/genética , Genoma , Células HEK293 , Células HeLa , Histonas/metabolismo , Humanos , Lisina/metabolismo , Espectroscopia de Ressonância Magnética , Metilação , NAD/metabolismo , Proteínas Nucleares/química , Fosfoproteínas/metabolismo , Ligação Proteica , Domínios Proteicos , RNA/metabolismo , Processamento Pós-Transcricional do RNA , Transcrição Genética
4.
J Hematol Oncol ; 13(1): 120, 2020 09 04.
Artigo em Inglês | MEDLINE | ID: mdl-32887634

RESUMO

BACKGROUND: Critically ill patients diagnosed with COVID-19 may develop a pro-thrombotic state that places them at a dramatically increased lethal risk. Although platelet activation is critical for thrombosis and is responsible for the thrombotic events and cardiovascular complications, the role of platelets in the pathogenesis of COVID-19 remains unclear. METHODS: Using platelets from healthy volunteers, non-COVID-19 and COVID-19 patients, as well as wild-type and hACE2 transgenic mice, we evaluated the changes in platelet and coagulation parameters in COVID-19 patients. We investigated ACE2 expression and direct effect of SARS-CoV-2 virus on platelets by RT-PCR, flow cytometry, Western blot, immunofluorescence, and platelet functional studies in vitro, FeCl3-induced thrombus formation in vivo, and thrombus formation under flow conditions ex vivo. RESULTS: We demonstrated that COVID-19 patients present with increased mean platelet volume (MPV) and platelet hyperactivity, which correlated with a decrease in overall platelet count. Detectable SARS-CoV-2 RNA in the blood stream was associated with platelet hyperactivity in critically ill patients. Platelets expressed ACE2, a host cell receptor for SARS-CoV-2, and TMPRSS2, a serine protease for Spike protein priming. SARS-CoV-2 and its Spike protein directly enhanced platelet activation such as platelet aggregation, PAC-1 binding, CD62P expression, α granule secretion, dense granule release, platelet spreading, and clot retraction in vitro, and thereby Spike protein enhanced thrombosis formation in wild-type mice transfused with hACE2 transgenic platelets, but this was not observed in animals transfused with wild-type platelets in vivo. Further, we provided evidence suggesting that the MAPK pathway, downstream of ACE2, mediates the potentiating role of SARS-CoV-2 on platelet activation, and that platelet ACE2 expression decreases following SARS-COV-2 stimulation. SARS-CoV-2 and its Spike protein directly stimulated platelets to facilitate the release of coagulation factors, the secretion of inflammatory factors, and the formation of leukocyte-platelet aggregates. Recombinant human ACE2 protein and anti-Spike monoclonal antibody could inhibit SARS-CoV-2 Spike protein-induced platelet activation. CONCLUSIONS: Our findings uncovered a novel function of SARS-CoV-2 on platelet activation via binding of Spike to ACE2. SARS-CoV-2-induced platelet activation may participate in thrombus formation and inflammatory responses in COVID-19 patients.


Assuntos
Betacoronavirus/metabolismo , Plaquetas/metabolismo , Infecções por Coronavirus/metabolismo , Peptidil Dipeptidase A/metabolismo , Pneumonia Viral/metabolismo , Trombose/metabolismo , Adulto , Idoso , Animais , Betacoronavirus/genética , Células CACO-2 , Infecções por Coronavirus/virologia , Feminino , Células HeLa , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Pessoa de Meia-Idade , Células PC-3 , Pandemias , Peptidil Dipeptidase A/genética , Agregação Plaquetária/imunologia , Contagem de Plaquetas , Pneumonia Viral/virologia , RNA Viral/sangue , Serina Endopeptidases/metabolismo , Glicoproteína da Espícula de Coronavírus/metabolismo , Trombose/virologia
5.
Nat Commun ; 11(1): 4676, 2020 09 16.
Artigo em Inglês | MEDLINE | ID: mdl-32938922

RESUMO

Translation efficiency varies considerably between different mRNAs, thereby impacting protein expression. Translation of the stress response master-regulator ATF4 increases upon stress, but the molecular mechanisms are not well understood. We discover here that translation factors DENR, MCTS1 and eIF2D are required to induce ATF4 translation upon stress by promoting translation reinitiation in the ATF4 5'UTR. We find DENR and MCTS1 are only needed for reinitiation after upstream Open Reading Frames (uORFs) containing certain penultimate codons, perhaps because DENR•MCTS1 are needed to evict only certain tRNAs from post-termination 40S ribosomes. This provides a model for how DENR and MCTS1 promote translation reinitiation. Cancer cells, which are exposed to many stresses, require ATF4 for survival and proliferation. We find a strong correlation between DENR•MCTS1 expression and ATF4 activity across cancers. Furthermore, additional oncogenes including a-Raf, c-Raf and Cdk4 have long uORFs and are translated in a DENR•MCTS1 dependent manner.


Assuntos
Fator 4 Ativador da Transcrição/genética , Fatores de Iniciação em Eucariotos/metabolismo , Biossíntese de Proteínas , Ribossomos/metabolismo , Regiões 5' não Traduzidas , Fator 4 Ativador da Transcrição/metabolismo , Proteínas de Ciclo Celular/genética , Códon , Fator de Iniciação 2 em Eucariotos/genética , Fator de Iniciação 2 em Eucariotos/metabolismo , Fatores de Iniciação em Eucariotos/genética , Regulação da Expressão Gênica , Células HeLa , Humanos , Neoplasias/genética , Proteínas Oncogênicas/genética , Oncogenes , Fases de Leitura Aberta , RNA Mensageiro , RNA de Transferência/genética , RNA de Transferência/metabolismo , Subunidades Ribossômicas Menores de Eucariotos/genética , Subunidades Ribossômicas Menores de Eucariotos/metabolismo , Ribossomos/genética
6.
Nat Commun ; 11(1): 4515, 2020 09 09.
Artigo em Inglês | MEDLINE | ID: mdl-32908127

RESUMO

The discovery of ancestral RAG transposons in early deuterostomia reveals the origin of vertebrate V(D)J recombination. Here, we analyze the functional regulation of a RAG transposon, ProtoRAG, in lancelet. We find that a specific interaction between the cis-acting element within the TIR sequences of ProtoRAG and a trans-acting factor, lancelet YY1-like (bbYY1), is important for the transcriptional regulation of lancelet RAG-like genes (bbRAG1L and bbRAG2L). Mechanistically, bbYY1 suppresses the transposition of ProtoRAG; meanwhile, bbYY1 promotes host DNA rejoins (HDJ) and TIR-TIR joints (TTJ) after TIR-dependent excision by facilitating the binding of bbRAG1L/2 L to TIR-containing DNA, and by interacting with the bbRAG1L/2 L complex. Our data thus suggest that bbYY1 has dual functions in fine-tuning the activity of ProtoRAG and maintaining the genome stability of the host.


Assuntos
Elementos de DNA Transponíveis/genética , Proteínas de Ligação a DNA/metabolismo , Anfioxos/genética , Recombinação V(D)J , Fator de Transcrição YY1/metabolismo , Animais , Técnicas de Silenciamento de Genes , Genes RAG-1 , Instabilidade Genômica , Células HEK293 , Células HeLa , Humanos , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificação , Proteínas Recombinantes/metabolismo , Fator de Transcrição YY1/genética , Fator de Transcrição YY1/isolamento & purificação
7.
J Exp Med ; 217(12)2020 12 07.
Artigo em Inglês | MEDLINE | ID: mdl-32926098

RESUMO

Severe COVID-19 patients develop acute respiratory distress syndrome that may progress to cytokine storm syndrome, organ dysfunction, and death. Considering that neutrophil extracellular traps (NETs) have been described as important mediators of tissue damage in inflammatory diseases, we investigated whether NETs would be involved in COVID-19 pathophysiology. A cohort of 32 hospitalized patients with a confirmed diagnosis of COVID-19 and healthy controls were enrolled. The concentration of NETs was augmented in plasma, tracheal aspirate, and lung autopsies tissues from COVID-19 patients, and their neutrophils released higher levels of NETs. Notably, we found that viable SARS-CoV-2 can directly induce the release of NETs by healthy neutrophils. Mechanistically, NETs triggered by SARS-CoV-2 depend on angiotensin-converting enzyme 2, serine protease, virus replication, and PAD-4. Finally, NETs released by SARS-CoV-2-activated neutrophils promote lung epithelial cell death in vitro. These results unravel a possible detrimental role of NETs in the pathophysiology of COVID-19. Therefore, the inhibition of NETs represents a potential therapeutic target for COVID-19.


Assuntos
Betacoronavirus/fisiologia , Infecções por Coronavirus/imunologia , Infecções por Coronavirus/virologia , Armadilhas Extracelulares/fisiologia , Pneumonia Viral/imunologia , Pneumonia Viral/virologia , Células A549 , Adulto , Morte Celular , Infecções por Coronavirus/sangue , Infecções por Coronavirus/patologia , Células Epiteliais/patologia , Células Epiteliais/virologia , Feminino , Células HeLa , Humanos , Masculino , Ativação de Neutrófilo , Pandemias , Peptidil Dipeptidase A/metabolismo , Pneumonia Viral/sangue , Pneumonia Viral/patologia , Serina Proteases/metabolismo , Sucção , Traqueia/imunologia
8.
Anticancer Res ; 40(10): 5471-5480, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32988869

RESUMO

BACKGROUND/AIM: Accurate regulation of the spindle assembly checkpoint (SAC) and anaphase promoting complex/cyclosome (APC/C) are essential for the correct execution of mitosis. In this work, we focused on MAD2L2 (REV7), a central translesion (TLS) protein, which also functions as a mitotic regulator by inhibiting APC/C in prometaphase. MATERIALS AND METHODS: Using bioinformatics analysis, live cell imaging and APC/C protein binding and degradation assays, we explored the influence of MAD2L2 over-expression in breast cancer. RESULTS: A significant over-expression of MAD2L2 was found in triple negative breast cancers (TNBC), compared to other breast cancers, correlating to poor patient prognosis. We also identified significant over-expression of MAD2L2 in the MDA-MB-157 triple negative (TN) cell line. A high percentage of MDA-MB-157 cells failed to complete mitosis and died during mitosis or shortly after. In addition, these cells completed mitosis at a significantly slower rate than control cells. MDA-MB-157 cells present high levels of mitotic slippage upon nocodazole treatment and acute dysregulation in APC/C function and substrate degradation. Moreover, silencing of MAD2L2 in the MDA-MB-157 cell line improved mitotic phenotypes. CONCLUSION: MAD2L2 over-expression supports the carcinogenic phenotype of MDA-MB-157 cells by promoting uncontrolled mitosis.


Assuntos
Neoplasias da Mama/genética , Proteínas Mad2/genética , Mitose/genética , Neoplasias da Mama/patologia , Feminino , Regulação Neoplásica da Expressão Gênica/genética , Células HeLa , Humanos , Pontos de Checagem da Fase M do Ciclo Celular/genética , Prometáfase/genética
9.
PLoS Pathog ; 16(8): e1008822, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32866204

RESUMO

Shigella flexneri invades host cells by entering within a bacteria-containing vacuole (BCV). In order to establish its niche in the host cytosol, the bacterium ruptures its BCV. Contacts between S. flexneri BCV and infection-associated macropinosomes (IAMs) formed in situ have been reported to enhance BCV disintegration. The mechanism underlying S. flexneri vacuolar escape remains however obscure. To decipher the molecular mechanism priming the communication between the IAMs and S. flexneri BCV, we performed mass spectrometry-based analysis of the magnetically purified IAMs from S. flexneri-infected cells. While proteins involved in host recycling and exocytic pathways were significantly enriched at the IAMs, we demonstrate more precisely that the S. flexneri type III effector protein IpgD mediates the recruitment of the exocyst to the IAMs through the Rab8/Rab11 pathway. This recruitment results in IAM clustering around S. flexneri BCV. More importantly, we reveal that IAM clustering subsequently facilitates an IAM-mediated unwrapping of the ruptured vacuole membranes from S. flexneri, enabling the naked bacterium to be ready for intercellular spread via actin-based motility. Taken together, our work untangles the molecular cascade of S. flexneri-driven host trafficking subversion at IAMs to develop its cytosolic lifestyle, a crucial step en route for infection progression at cellular and tissue level.


Assuntos
Disenteria Bacilar , Shigella flexneri , Transdução de Sinais , Vacúolos , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Disenteria Bacilar/genética , Disenteria Bacilar/metabolismo , Células HeLa , Humanos , Shigella flexneri/genética , Shigella flexneri/metabolismo , Shigella flexneri/patogenicidade , Vacúolos/genética , Vacúolos/metabolismo , Vacúolos/microbiologia , Fatores de Virulência/genética , Fatores de Virulência/metabolismo , Proteínas rab de Ligação ao GTP/genética , Proteínas rab de Ligação ao GTP/metabolismo
11.
Nat Commun ; 11(1): 4576, 2020 09 11.
Artigo em Inglês | MEDLINE | ID: mdl-32917905

RESUMO

Endosome maturation depends on membrane contact sites (MCSs) formed between endoplasmic reticulum (ER) and endolysosomes (LyLEs). The mechanism underlying lipid supply for this process and its pathophysiological relevance remains unclear, however. Here, we identify PDZD8-the mammalian ortholog of a yeast ERMES subunit-as a protein that interacts with protrudin, which is located at ER-LyLE MCSs. Protrudin and PDZD8 promote the formation of ER-LyLE MCSs, and PDZD8 shows the ability to extract various lipids from the ER. Overexpression of both protrudin and PDZD8 in HeLa cells, as well as their depletion in mouse primary neurons, impairs endosomal homeostasis by inducing the formation of abnormal large vacuoles reminiscent of those apparent in spastin- or REEP1-deficient neurons. The protrudin-PDZD8 system is also essential for the establishment of neuronal polarity. Our results suggest that protrudin and PDZD8 cooperatively promote endosome maturation by mediating ER-LyLE tethering and lipid extraction at MCSs, thereby maintaining neuronal polarity and integrity.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Endossomos/fisiologia , Metabolismo dos Lipídeos , Neurônios/metabolismo , Proteínas de Transporte Vesicular/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Animais , Modelos Animais de Doenças , Retículo Endoplasmático/metabolismo , Feminino , Células HEK293 , Células HeLa , Humanos , Lipídeos , Lipossomos/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos ICR , Camundongos Knockout , Mitocôndrias , Domínios Proteicos , Proteômica , Proteínas Recombinantes , Saccharomyces cerevisiae/metabolismo , Proteínas de Transporte Vesicular/genética
12.
PLoS One ; 15(9): e0238614, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32936826

RESUMO

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and associated with severe respiratory illness emerged in Wuhan, China, in late 2019. The virus has been able to spread promptly across all continents in the world. The current pandemic has posed a great threat to public health concern and safety. Currently, there are no specific treatments or licensed vaccines available for COVID-19. We isolated SARS-CoV-2 from the nasopharyngeal sample of a patient in Turkey with confirmed COVID-19. We determined that the Vero E6 and MA-104 cell lines are suitable for supporting SARS-CoV-2 that supports viral replication, development of cytopathic effect (CPE) and subsequent cell death. Phylogenetic analyses of the whole genome sequences showed that the hCoV-19/Turkey/ERAGEM-001/2020 strain clustered with the strains primarily from Australia, Canada, England, Iran and Kuwait and that the cases in the nearby clusters were reported to have travel history to Iran and to share the common unique nucleotide substitutions.


Assuntos
Betacoronavirus/isolamento & purificação , Pandemias , Cultura de Vírus/métodos , Animais , Austrália , Betacoronavirus/genética , Betacoronavirus/fisiologia , Canadá , Linhagem Celular , Chlorocebus aethiops , Busca de Comunicante , Infecções por Coronavirus , Efeito Citopatogênico Viral , DNA Complementar/genética , DNA Viral/genética , Inglaterra , Genoma Viral , Células HeLa , Humanos , Irã (Geográfico) , Kuweit , Macaca mulatta , Nasofaringe/virologia , Filogenia , Pneumonia Viral , Análise de Sequência de DNA , Viagem , Turquia/epidemiologia , Células Vero , Replicação Viral
13.
Anticancer Res ; 40(9): 5025-5033, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32878790

RESUMO

BACKGROUND/AIM: This study aimed to investigate the effect of a new 7-(4-(N-substituted carbamoylmethyl) piperazin-1-yl) ciprofloxacin-derivative on the proliferation and migration abilities of HeLa cells. MATERIALS AND METHODS: Cell viability and morphological alterations were examined. Changes in migration were detected using wound healing and colony formation assays. Flow cytometry and western blotting were used to investigate the molecular mechanisms underlying this ciprofloxacin-derivative's action in HeLa cells. RESULTS: The examined ciprofloxacin-derivative reduced viability of HeLa cells in a concentration-dependent manner and altered cellular morphology, indicating cell death. Furthermore, it significantly inhibited wound closure, even in a non-cytotoxic concentration, and reduced HeLa cell colony formation. In addition, apoptosis was increased probably through significant up-regulation of Bax protein expression and the generation of active cleaved caspase-3 protein. CONCLUSION: Our new derivative inhibits proliferation and induces apoptosis of HeLa cells. Furthermore, it suppressed the migration and colony formation abilities of HeLa cells. Therefore, it represents an attractive agent for drug development against cervical cancer based on its anti-metastatic effect.


Assuntos
Antineoplásicos/farmacologia , Ciprofloxacino/análogos & derivados , Ciprofloxacino/farmacologia , Antineoplásicos/química , Apoptose/efeitos dos fármacos , Linhagem Celular Tumoral , Movimento Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Ciprofloxacino/química , Relação Dose-Resposta a Droga , Células HeLa , Humanos , Estrutura Molecular , Ensaio Tumoral de Célula-Tronco
14.
PLoS Comput Biol ; 16(9): e1008193, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32925919

RESUMO

Segmenting cell nuclei within microscopy images is a ubiquitous task in biological research and clinical applications. Unfortunately, segmenting low-contrast overlapping objects that may be tightly packed is a major bottleneck in standard deep learning-based models. We report a Nuclear Segmentation Tool (NuSeT) based on deep learning that accurately segments nuclei across multiple types of fluorescence imaging data. Using a hybrid network consisting of U-Net and Region Proposal Networks (RPN), followed by a watershed step, we have achieved superior performance in detecting and delineating nuclear boundaries in 2D and 3D images of varying complexities. By using foreground normalization and additional training on synthetic images containing non-cellular artifacts, NuSeT improves nuclear detection and reduces false positives. NuSeT addresses common challenges in nuclear segmentation such as variability in nuclear signal and shape, limited training sample size, and sample preparation artifacts. Compared to other segmentation models, NuSeT consistently fares better in generating accurate segmentation masks and assigning boundaries for touching nuclei.


Assuntos
Núcleo Celular/fisiologia , Aprendizado Profundo , Processamento de Imagem Assistida por Computador/métodos , Microscopia/métodos , Algoritmos , Artefatos , Biologia Computacional , Células HeLa , Humanos , Software
15.
PLoS Comput Biol ; 16(9): e1008202, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32925922

RESUMO

Hydrogen peroxide (H2O2) promotes a range of phenotypes depending on its intracellular concentration and dosing kinetics, including cell death. While this qualitative relationship has been well established, the quantitative and mechanistic aspects of H2O2 signaling are still being elucidated. Mitochondria, a putative source of intracellular H2O2, have recently been demonstrated to be particularly vulnerable to localized H2O2 perturbations, eliciting a dramatic cell death response in comparison to similar cytosolic perturbations. We sought to improve our dynamic and mechanistic understanding of the mitochondrial H2O2 reaction network in HeLa cells by creating a kinetic model of this system and using it to explore basal and perturbed conditions. The model uses the most current quantitative proteomic and kinetic data available to predict reaction rates and steady-state concentrations of H2O2 and its reaction partners within individual mitochondria. Time scales ranging from milliseconds to one hour were simulated. We predict that basal, steady-state mitochondrial H2O2 will be in the low nM range (2-4 nM) and will be inversely dependent on the total pool of peroxiredoxin-3 (Prx3). Neglecting efflux of H2O2 to the cytosol, the mitochondrial reaction network is expected to control perturbations well up to H2O2 generation rates ~50 µM/s (0.25 nmol/mg-protein/s), above which point the Prx3 system would be expected to collapse. Comparison of these results with redox Western blots of Prx3 and Prx2 oxidation states demonstrated reasonable trend agreement at short times (≤ 15 min) for a range of experimentally perturbed H2O2 generation rates. At longer times, substantial efflux of H2O2 from the mitochondria to the cytosol was evidenced by peroxiredoxin-2 (Prx2) oxidation, and Prx3 collapse was not observed. A refined model using Monte Carlo parameter sampling was used to explore rates of H2O2 efflux that could reconcile model predictions of Prx3 oxidation states with the experimental observations.


Assuntos
Peróxido de Hidrogênio/metabolismo , Mitocôndrias/metabolismo , Modelos Biológicos , Neoplasias/metabolismo , Biologia Computacional , Citosol/química , Citosol/metabolismo , Células HeLa , Humanos , Cinética , Mitocôndrias/química , Neoplasias/química , Espécies Reativas de Oxigênio/química , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais/fisiologia
16.
PLoS Pathog ; 16(9): e1008878, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32946535

RESUMO

As an obligate intracellular pathogen, host cell invasion is paramount to Chlamydia trachomatis proliferation. While the mechanistic underpinnings of this essential process remain ill-defined, it is predicted to involve delivery of prepackaged effector proteins into the host cell that trigger plasma membrane remodeling and cytoskeletal reorganization. The secreted effector proteins TmeA and TarP, have risen to prominence as putative key regulators of cellular invasion and bacterial pathogenesis. Although several studies have begun to unravel molecular details underlying the putative function of TarP, the physiological function of TmeA during host cell invasion is unknown. Here, we show that TmeA employs molecular mimicry to bind to the GTPase binding domain of N-WASP, which results in recruitment of the actin branching ARP2/3 complex to the site of chlamydial entry. Electron microscopy revealed that TmeA mutants are deficient in filopodia capture, suggesting that TmeA/N-WASP interactions ultimately modulate host cell plasma membrane remodeling events necessary for chlamydial entry. Importantly, while both TmeA and TarP are necessary for effective host cell invasion, we show that these effectors target distinct pathways that ultimately converge on activation of the ARP2/3 complex. In line with this observation, we show that a double mutant suffers from a severe entry defect nearly identical to that observed when ARP3 is chemically inhibited or knocked down. Collectively, our study highlights both TmeA and TarP as essential regulators of chlamydial invasion that modulate the ARP2/3 complex through distinct signaling platforms, resulting in plasma membrane remodeling events that are essential for pathogen uptake.


Assuntos
Proteínas de Bactérias , Membrana Celular/metabolismo , Chlamydia trachomatis , Proteína Neuronal da Síndrome de Wiskott-Aldrich/metabolismo , Complexo 2-3 de Proteínas Relacionadas à Actina/genética , Complexo 2-3 de Proteínas Relacionadas à Actina/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Membrana Celular/genética , Membrana Celular/patologia , Chlamydia trachomatis/genética , Chlamydia trachomatis/metabolismo , Chlamydia trachomatis/patogenicidade , Células HeLa , Humanos , Mutação , Domínios Proteicos , Pseudópodes/genética , Pseudópodes/metabolismo , Proteína Neuronal da Síndrome de Wiskott-Aldrich/genética
17.
Nat Commun ; 11(1): 4894, 2020 09 29.
Artigo em Inglês | MEDLINE | ID: mdl-32994400

RESUMO

Identification of the complete set of translated genes of viruses is important to understand viral replication and pathogenesis as well as for therapeutic approaches to control viral infection. Here, we use chemical proteomics, integrating bio-orthogonal non-canonical amino acid tagging and high-resolution mass spectrometry, to characterize the newly synthesized herpes simplex virus 1 (HSV-1) proteome in infected cells. In these infected cells, host cellular protein synthesis is shut-off, increasing the chance to preferentially detect viral proteomes. We identify nine previously cryptic orphan protein coding sequences whose translated products are expressed in HSV-1-infected cells. Functional characterization of one identified protein, designated piUL49, shows that it is critical for HSV-1 neurovirulence in vivo by regulating the activity of virally encoded dUTPase, a key enzyme that maintains accurate DNA replication. Our results demonstrate that cryptic orphan protein coding genes of HSV-1, and probably other large DNA viruses, remain to be identified.


Assuntos
Encefalite por Herpes Simples/virologia , Herpesvirus Humano 1/patogenicidade , Pirofosfatases/metabolismo , Proteínas Virais/metabolismo , Fatores de Virulência/metabolismo , Animais , Encéfalo/patologia , Encéfalo/virologia , Chlorocebus aethiops , Replicação do DNA , Modelos Animais de Doenças , Encefalite por Herpes Simples/patologia , Feminino , Genes Virais/genética , Células HEK293 , Células HeLa , Herpesvirus Humano 1/genética , Humanos , Camundongos , Biossíntese de Proteínas , Proteômica/métodos , Células Vero , Proteínas Virais/genética , Fatores de Virulência/genética , Replicação Viral
18.
Acta Crystallogr C Struct Chem ; 76(Pt 8): 795-809, 2020 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-32756043

RESUMO

The crystal structures of four new chiral [1,2,3]triazolo[5,1-b][1,3,4]thiadiazines are described, namely, ethyl 5'-benzoyl-5'H,7'H-spiro[cyclohexane-1,6'-[1,2,3]triazolo[5,1-b][1,3,4]thiadiazine]-3'-carboxylate, C19H22N4O3S, ethyl 5'-(4-methoxybenzoyl)-5'H,7'H-spiro[cyclohexane-1,6'-[1,2,3]triazolo[5,1-b][1,3,4]thiadiazine]-3'-carboxylate, C20H24N4O4S, ethyl 6,6-dimethyl-5-(4-methylbenzoyl)-6,7-dihydro-5H-[1,2,3]triazolo[5,1-b][1,3,4]thiadiazine-3-carboxylate, C17H20N4O3S, and ethyl 5-benzoyl-6-(4-methoxyphenyl)-6,7-dihydro-5H-[1,2,3]triazolo[5,1-b][1,3,4]thiadiazine-3-carboxylate, C21H20N4O4S. The crystallographic data and cell activities of these four compounds and of the structures of three previously reported similar compounds, namely, ethyl 5'-(4-methylbenzoyl)-5'H,7'H-spiro[cyclopentane-1,6'-[1,2,3]triazolo[5,1-b][1,3,4]thiadiazine]-3'-carboxylate, C19H22N4O3S, ethyl 5'-(4-methoxybenzoyl)-5'H,7'H-spiro[cyclopentane-1,6'-[1,2,3]triazolo[5,1-b][1,3,4]thiadiazine]-3'-carboxylate, C19H22N4O4S, and ethyl 6-methyl-5-(4-methylbenzoyl)-6-phenyl-6,7-dihydro-5H-[1,2,3]triazolo[5,1-b][1,3,4]thiadiazine-3-carboxylate, C22H22N4O3S, are contrasted and compared. For both crystallization and an MTT assay, racemic mixtures of the corresponding [1,2,3]triazolo[5,1-b][1,3,4]thiadiazines were used. The main manner of molecular packing in these compounds is the organization of either enantiomeric pairs or dimers. In both cases, the formation of two three-centre hydrogen bonds can be detected resulting from intramolecular N-H...O and intermolecular N-H...O or N-H...N interactions. Molecules of different enantiomeric forms can also form chains through N-H...O hydrogen bonds or form layers between which only weak hydrophobic contacts exist. Unlike other [1,2,3]triazolo[5,1-b][1,3,4]thiadiazines, ethyl 5'-benzoyl-5'H,7'H-spiro[cyclohexane-1,6'-[1,2,3]triazolo[5,1-b][1,3,4]thiadiazine]-3'-carboxylate contains molecules of only the (R)-enantiomer; moreover, the N-H group does not participate in any significant intermolecular interactions. Molecular mechanics methods (force field OPLS3e) and the DFT B3LYP/6-31G+(d,p) method show that the compound forming enantiomeric pairs via weak N-H...N hydrogen bonds is subject to greater distortion of the geometry under the influence of the intermolecular interactions in the crystal. For intramolecular N-H...O and S...O interactions, an analysis of the noncovalent interactions (NCIs) was carried out. The cellular activities of the compounds were tested by evaluating their antiproliferative effect against two normal human cell lines and two cancer cell lines in terms of half-maximum inhibitory concentration (IC50). Some derivatives have been found to be very effective in inhibiting the growth of Hela cells at nanomolar and submicromolar concentrations with minimal cytotoxicity in relation to normal cells.


Assuntos
Cicloexanos/química , Compostos Heterocíclicos/farmacologia , Tiadiazinas/química , Cristalografia por Raios X , Células HeLa , Compostos Heterocíclicos/química , Humanos , Ligação de Hidrogênio , Conformação Molecular , Estereoisomerismo , Tiadiazinas/farmacologia
19.
Nat Commun ; 11(1): 4046, 2020 08 13.
Artigo em Inglês | MEDLINE | ID: mdl-32792488

RESUMO

2-oxoglutarate (2-OG or α-ketoglutarate) relates mitochondrial metabolism to cell function by modulating the activity of 2-OG dependent dioxygenases involved in the hypoxia response and DNA/histone modifications. However, metabolic pathways that regulate these oxygen and 2-OG sensitive enzymes remain poorly understood. Here, using CRISPR Cas9 genome-wide mutagenesis to screen for genetic determinants of 2-OG levels, we uncover a redox sensitive mitochondrial lipoylation pathway, dependent on the mitochondrial hydrolase ABHD11, that signals changes in mitochondrial 2-OG metabolism to 2-OG dependent dioxygenase function. ABHD11 loss or inhibition drives a rapid increase in 2-OG levels by impairing lipoylation of the 2-OG dehydrogenase complex (OGDHc)-the rate limiting step for mitochondrial 2-OG metabolism. Rather than facilitating lipoate conjugation, ABHD11 associates with the OGDHc and maintains catalytic activity of lipoyl domain by preventing the formation of lipoyl adducts, highlighting ABHD11 as a regulator of functional lipoylation and 2-OG metabolism.


Assuntos
Complexo Cetoglutarato Desidrogenase/metabolismo , Ácidos Cetoglutáricos/metabolismo , Mitocôndrias/metabolismo , Mutagênese/fisiologia , Serina Proteases/metabolismo , Metabolismo Energético/genética , Metabolismo Energético/fisiologia , Células HeLa , Humanos , Complexo Cetoglutarato Desidrogenase/genética , Modelos Biológicos , Mutagênese/genética , Serina Proteases/genética
20.
Nat Commun ; 11(1): 4070, 2020 08 13.
Artigo em Inglês | MEDLINE | ID: mdl-32792502

RESUMO

Human astroviruses are small non-enveloped viruses with positive-sense single-stranded RNA genomes. Astroviruses cause acute gastroenteritis in children worldwide and have been associated with encephalitis and meningitis in immunocompromised individuals. It is still unknown how astrovirus particles exit infected cells following replication. Through comparative genomic analysis and ribosome profiling we here identify and confirm the expression of a conserved alternative-frame ORF, encoding the protein XP. XP-knockout astroviruses are attenuated and pseudo-revert on passaging. Further investigation into the function of XP revealed plasma and trans Golgi network membrane-associated roles in virus assembly and/or release through a viroporin-like activity. XP-knockout replicons have only a minor replication defect, demonstrating the role of XP at late stages of infection. The discovery of XP advances our knowledge of these important human viruses and opens an additional direction of research into their life cycle and pathogenesis.


Assuntos
Canais Iônicos/metabolismo , Mamastrovirus/metabolismo , Proteínas não Estruturais Virais/metabolismo , Animais , Linhagem Celular , Cricetinae , Eletroforese em Gel de Poliacrilamida , Genômica/métodos , Células HeLa , Humanos , Immunoblotting , Imunoprecipitação , Canais Iônicos/genética , Mamastrovirus/genética , Microscopia de Fluorescência , Plasmídeos/genética , Ribossomos , Proteínas não Estruturais Virais/genética , Replicação Viral/genética , Replicação Viral/fisiologia
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