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1.
Sheng Wu Gong Cheng Xue Bao ; 36(8): 1484-1492, 2020 Aug 25.
Artigo em Chinês | MEDLINE | ID: mdl-32924347

RESUMO

Ubiquitination, one type of the most common post-translational modification, mediates the regulation of protein homeostasis in vivo. Since ubiquitin itself contains multiple lysine residues and one N-terminal free amino group, eight types of ubiquitin chains can be formed. The K27 ubiquitin chain is formed through the ubiquitination of the ubiquitin Lys27 (K27), which adopts a compact conformation. In recent years, biological function of the K27 ubiquitin chain in innate immunity, protein homeostasis and DNA damage has been discovered, but the molecular mechanisms of K27 ubiquitin chain assembly, recognition and hydrolysis are still poorly understood. Here we review the structural features and biological functions of K27 ubiquitin chain, to provide a reference for future studies.


Assuntos
Ubiquitina , Imunidade Inata , Lisina , Processamento de Proteína Pós-Traducional , Ubiquitina/química , Ubiquitina/metabolismo , Ubiquitinação
2.
Nat Commun ; 11(1): 4868, 2020 09 28.
Artigo em Inglês | MEDLINE | ID: mdl-32985517

RESUMO

DNA damage sensors DDB2 and XPC initiate global genome nucleotide excision repair (NER) to protect DNA from mutagenesis caused by helix-distorting lesions. XPC recognizes helical distortions by binding to unpaired ssDNA opposite DNA lesions. DDB2 binds to UV-induced lesions directly and facilitates efficient recognition by XPC. We show that not only lesion-binding but also timely DDB2 dissociation is required for DNA damage handover to XPC and swift progression of the multistep repair reaction. DNA-binding-induced DDB2 ubiquitylation and ensuing degradation regulate its homeostasis to prevent excessive lesion (re)binding. Additionally, damage handover from DDB2 to XPC coincides with the arrival of the TFIIH complex, which further promotes DDB2 dissociation and formation of a stable XPC-TFIIH damage verification complex. Our results reveal a reciprocal coordination between DNA damage recognition and verification within NER and illustrate that timely repair factor dissociation is vital for correct spatiotemporal control of a multistep repair process.


Assuntos
Dano ao DNA , Reparo do DNA , Proteínas de Ligação a DNA/metabolismo , Fator de Transcrição TFIIH/metabolismo , Ubiquitina/metabolismo , Núcleo Celular/genética , Núcleo Celular/metabolismo , Proteínas de Ligação a DNA/genética , Humanos , Fator de Transcrição TFIIH/genética , Ubiquitinação
3.
Biomolecules ; 10(8)2020 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-32752270

RESUMO

Posttranslational modifications of cellular proteins by covalent conjugation of ubiquitin and ubiquitin-like polypeptides regulate numerous cellular processes that are captured by viruses to promote infection, replication, and spreading. The importance of these protein modifications for the viral life cycle is underscored by the discovery that many viruses encode deconjugases that reverse their functions. The structural and functional characterization of these viral enzymes and the identification of their viral and cellular substrates is providing valuable insights into the biology of viral infections and the host's antiviral defense. Given the growing body of evidence demonstrating their key contribution to pathogenesis, the viral deconjugases are now recognized as attractive targets for the design of novel antiviral therapeutics.


Assuntos
Antivirais/farmacologia , Enzimas/metabolismo , Interações Hospedeiro-Patógeno/fisiologia , Ubiquitina/metabolismo , Proteínas Virais/metabolismo , Viroses/metabolismo , Adenoviridae/enzimologia , Coronavirus/enzimologia , Enzimas/química , Herpesviridae/enzimologia , Humanos , Processamento de Proteína Pós-Traducional , Proteínas Virais/química , Viroses/tratamento farmacológico
4.
Life Sci ; 257: 118021, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32621919

RESUMO

AIMS: Tribbles homolog 3 (TRIB3) is emerging as a multifunctional oncoprotein associated with various cellular events in different tumors. However, the regulatory mechanism of TRIB3 in acute myeloid leukemia (AML) remains unknown. This study aims to investigate the molecular mechanisms and uncover the functions of TRIB3 in AML. METHODS: Western blotting and quantitative real-time PCR were used to analyze the expression levels of TRIB3, peroxisome proliferator-activated receptor α (PPARα), apoptosis markers and autophagy markers in AML cells. Flow cytometry was used to assess cell apoptosis. The interaction of TRIB3 and PPARα was evaluated by immunofluorescence, coimmunoprecipitation, and in vivo ubiquitination assays. KEY FINDINGS: We demonstrated that downregulating TRIB3 in leukemic cells effectively induced apoptosis and autophagy by regulating the degradation of PPARα. Mechanistically, TRIB3 interacted with PPARα and contributed to its destabilization by promoting its ubiquitination. When PPARα was activated by its specific agonist clofibrate, the apoptosis and autophagy of AML cells were significantly enhanced. These results were confirmed by rescue experiments. Blocking PPARα expression using the PPARα inhibitor GW6471 reversed the functional influence of TRIB3 on AML cells. SIGNIFICANCE: The aim of this study is to provide evidence of the degradation of PPARα by TRIB3 via ubiquitin-dependent proteasomal degradation. This process meditates the progression of AML and prolongs the survival of leukemic cells. As a result, these data indicate that TRIB3 is a novel and promising therapeutic target for AML treatment.


Assuntos
Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Leucemia Mieloide Aguda/genética , Proteínas Serina-Treonina Quinases/antagonistas & inibidores , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismo , Apoptose/fisiologia , Autofagia/fisiologia , Bases de Dados Genéticas , Humanos , Leucemia Mieloide Aguda/metabolismo , PPAR alfa/genética , PPAR alfa/metabolismo , Complexo de Endopeptidases do Proteassoma/metabolismo , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , Proteostase/fisiologia , Transdução de Sinais/fisiologia , Ubiquitina/metabolismo , Ubiquitinação
5.
PLoS Biol ; 18(7): e3000606, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32687490

RESUMO

The 70 kDa heat shock protein (HSP70) family of chaperones are the front line of protection from stress-induced misfolding and aggregation of polypeptides in most organisms and are responsible for promoting the stability, folding, and degradation of clients to maintain cellular protein homeostasis. Here, we demonstrate quantitative identification of HSP70 and 71 kDa heat shock cognate (HSC70) clients using a ubiquitin-mediated proximity tagging strategy and show that, despite their high degree of similarity, these enzymes have largely nonoverlapping specificities. Both proteins show a preference for association with newly synthesized polypeptides, but each responds differently to changes in the stoichiometry of proteins in obligate multi-subunit complexes. In addition, expression of an amyotrophic lateral sclerosis (ALS)-associated superoxide dismutase 1 (SOD1) mutant protein induces changes in HSP70 and HSC70 client association and aggregation toward polypeptides with predicted disorder, indicating that there are global effects from a single misfolded protein that extend to many clients within chaperone networks. Together these findings show that the ubiquitin-activated interaction trap (UBAIT) fusion system can efficiently isolate the complex interactome of HSP chaperone family proteins under normal and stress conditions.


Assuntos
Proteínas de Choque Térmico HSC70/metabolismo , Proteínas de Choque Térmico HSP70/metabolismo , Proteoma/metabolismo , Linhagem Celular , Humanos , Mutação/genética , Ligação Proteica , Biossíntese de Proteínas , Dobramento de Proteína , Especificidade por Substrato , Ubiquitina/metabolismo
6.
PLoS One ; 15(7): e0235925, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32639967

RESUMO

Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by speech impairment, intellectual disability, ataxia, and epilepsy. AS is caused by mutations in the maternal copy of UBE3A located on chromosome 15q11-13. UBE3A codes for E6AP (E6 Associated Protein), a prominent member of the HECT (Homologous to E6AP C-Terminus) E3 ubiquitin ligase family. E6AP catalyzes the posttranslational attachment of ubiquitin via its HECT domain onto various intracellular target proteins to regulate DNA repair and cell cycle progression. The HECT domain consists of an N-lobe, required for E2~ubiquitin recruitment, while the C-lobe contains the conserved catalytic cysteine required for ubiquitin transfer. Previous genetic studies of AS patients have identified point mutations in UBE3A that result in amino acid substitutions or premature termination during translation. An AS transversion mutation (codon change from ATA to AAA) within the region of the gene that codes for the catalytic HECT domain of E6AP has been annotated (I827K), but the molecular basis for this loss of function substitution remained elusive. Here, we demonstrate that the I827K substitution destabilizes the 3D fold causing protein aggregation of the C-terminal lobe of E6AP using a combination of spectropolarimetry and nuclear magnetic resonance (NMR) spectroscopy. Our fluorescent ubiquitin activity assays with E6AP-I827K show decreased ubiquitin thiolester formation and ubiquitin discharge. Using 3D models in combination with our biochemical and biophysical results, we rationalize why the I827K disrupts E6AP-dependent ubiquitylation. This work provides new insight into the E6AP mechanism and how its malfunction can be linked to the AS phenotype.


Assuntos
Síndrome de Angelman/genética , Ubiquitina-Proteína Ligases/metabolismo , Síndrome de Angelman/patologia , Biocatálise , Dicroísmo Circular , Humanos , Mutagênese Sítio-Dirigida , Ressonância Magnética Nuclear Biomolecular , Domínios Proteicos , Estabilidade Proteica , Estrutura Secundária de Proteína , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/química , Proteínas Recombinantes/isolamento & purificação , Ubiquitina/metabolismo , Ubiquitina-Proteína Ligases/química , Ubiquitina-Proteína Ligases/genética , Ubiquitinação
7.
Nucleic Acids Res ; 48(14): 7944-7957, 2020 08 20.
Artigo em Inglês | MEDLINE | ID: mdl-32667666

RESUMO

Circadian clocks are endogenous oscillators that control ∼24-hour physiology and behaviors in virtually all organisms. The circadian oscillator comprises interconnected transcriptional and translational feedback loops, but also requires finely coordinated protein homeostasis including protein degradation and maturation. However, the mechanisms underlying the mammalian clock protein maturation is largely unknown. In this study, we demonstrate that necdin, one of the Prader-Willi syndrome (PWS)-causative genes, is highly expressed in the suprachiasmatic nuclei (SCN), the pacemaker of circadian clocks in mammals. Mice deficient in necdin show abnormal behaviors during an 8-hour advance jet-lag paradigm and disrupted clock gene expression in the liver. By using yeast two hybrid screening, we identified BMAL1, the core component of the circadian clock, and co-chaperone SGT1 as two necdin-interactive proteins. BMAL1 and SGT1 associated with the N-terminal and C-terminal fragments of necdin, respectively. Mechanistically, necdin enables SGT1-HSP90 chaperone machinery to stabilize BMAL1. Depletion of necdin or SGT1/HSP90 leads to degradation of BMAL1 through the ubiquitin-proteasome system, resulting in alterations in both clock gene expression and circadian rhythms. Taken together, our data identify the PWS-associated protein necdin as a novel regulator of the circadian clock, and further emphasize the critical roles of chaperone machinery in circadian clock regulation.


Assuntos
Fatores de Transcrição ARNTL/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Proteínas de Ciclo Celular/metabolismo , Relógios Circadianos , Proteínas de Choque Térmico HSP90/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Proteínas Nucleares/metabolismo , Animais , Relógios Circadianos/genética , Expressão Gênica , Camundongos , Proteínas do Tecido Nervoso/genética , Proteínas Nucleares/genética , Complexo de Endopeptidases do Proteassoma/metabolismo , Estabilidade Proteica , Ubiquitina/metabolismo
8.
Mol Cell Biol ; 40(18)2020 08 28.
Artigo em Inglês | MEDLINE | ID: mdl-32631902

RESUMO

hRpn13/ADRM1 links substrate recruitment with deubiquitination at the proteasome through its proteasome- and ubiquitin-binding Pru domain and DEUBAD domain, which binds and activates deubiquitinating enzyme (DUB) UCHL5/Uch37. Here, we edit the HCT116 colorectal cancer cell line to delete part of the hRpn13 Pru, producing cells that express truncated hRpn13 (trRpn13), which is competent for UCHL5 binding but defective for proteasome interaction. trRpn13 cells demonstrate reduced levels of proteasome-bound ubiquitinated proteins, indicating that the loss of hRpn13 function at proteasomes cannot be fully compensated for by the two other dedicated substrate receptors (hRpn1 and hRpn10). Previous studies indicated that the loss of full-length hRpn13 causes a corresponding reduction of UCHL5. We find UCHL5 levels unaltered in trRpn13 cells, but hRpn11 is elevated in ΔhRpn13 and trRpn13 cells, perhaps from cell stress. Despite the ∼90 DUBs in human cells, including two others in addition to UCHL5 at the proteasome, we found deletion of UCHL5 from HCT116 cells to cause increased levels of ubiquitinated proteins in whole-cell extract and at proteasomes, suggesting that UCHL5 activity cannot be fully assumed by other DUBs. We also report anticancer molecule RA190, which binds covalently to hRpn13 and UCHL5, to require hRpn13 Pru and not UCHL5 for cytotoxicity.


Assuntos
Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Chaperonas Moleculares/metabolismo , Ubiquitina Tiolesterase/metabolismo , Sequência de Aminoácidos , Sítios de Ligação , Citoplasma/metabolismo , Células HCT116 , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/genética , Glicoproteínas de Membrana/metabolismo , Chaperonas Moleculares/genética , Complexo de Endopeptidases do Proteassoma/metabolismo , Ligação Proteica , Ubiquitina/metabolismo , Ubiquitina Tiolesterase/genética , Proteínas Ubiquitinadas/metabolismo
9.
PLoS Pathog ; 16(6): e1008640, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32569299

RESUMO

Ubiquitylation is a common post translational modification of eukaryotic proteins and in the human malaria parasite, Plasmodium falciparum (Pf) overall ubiquitylation increases in the transition from intracellular schizont to extracellular merozoite stages in the asexual blood stage cycle. Here, we identify specific ubiquitylation sites of protein substrates in three intraerythrocytic parasite stages and extracellular merozoites; a total of 1464 sites in 546 proteins were identified (data available via ProteomeXchange with identifier PXD014998). 469 ubiquitylated proteins were identified in merozoites compared with only 160 in the preceding intracellular schizont stage, suggesting a large increase in protein ubiquitylation associated with merozoite maturation. Following merozoite invasion of erythrocytes, few ubiquitylated proteins were detected in the first intracellular ring stage but as parasites matured through trophozoite to schizont stages the apparent extent of ubiquitylation increased. We identified commonly used ubiquitylation motifs and groups of ubiquitylated proteins in specific areas of cellular function, for example merozoite pellicle proteins involved in erythrocyte invasion, exported proteins, and histones. To investigate the importance of ubiquitylation we screened ubiquitin pathway inhibitors in a parasite growth assay and identified the ubiquitin activating enzyme (UBA1 or E1) inhibitor MLN7243 (TAK-243) to be particularly effective. This small molecule was shown to be a potent inhibitor of recombinant PfUBA1, and a structural homology model of MLN7243 bound to the parasite enzyme highlights avenues for the development of P. falciparum specific inhibitors. We created a genetically modified parasite with a rapamycin-inducible functional deletion of uba1; addition of either MLN7243 or rapamycin to the recombinant parasite line resulted in the same phenotype, with parasite development blocked at the schizont stage. Nuclear division and formation of intracellular structures was interrupted. These results indicate that the intracellular target of MLN7243 is UBA1, and this activity is essential for the final differentiation of schizonts to merozoites.


Assuntos
Merozoítos/metabolismo , Plasmodium falciparum/metabolismo , Proteínas de Protozoários/metabolismo , Ubiquitina/metabolismo , Ubiquitinação , Humanos , Plasmodium falciparum/genética , Proteínas de Protozoários/genética , Ubiquitina/genética
10.
Mol Pharmacol ; 98(2): 130-142, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32487733

RESUMO

Aberrant cellular Myc (c-Myc) is a common feature in the majority of human cancers and has been linked to oncogenic malignancies. Here, we developed a novel c-Myc-targeting compound, N, N-bis (5-ethyl-2-hydroxybenzyl) methylamine (EMD), and present evidence demonstrating its effectiveness in targeting c-Myc for degradation in human lung carcinoma. EMD exhibited strong cytotoxicity toward various human lung cancer cell lines, as well as chemotherapeutic-resistant patient-derived lung cancer cells, through apoptosis induction in comparison with chemotherapeutic drugs. The IC50 of EMD against lung cancer cells was approximately 60 µM. Mechanistically, EMD eliminated c-Myc in the cells and initiated caspase-dependent apoptosis cascade. Cycloheximide chase assay revealed that EMD tended to shorten the half-life of c-Myc by approximately half. The cotreatment of EMD with the proteasome inhibitor MG132 reversed its c-Myc-targeting effect, suggesting the involvement of ubiquitin-mediated proteasomal degradation in the process. We further verified that EMD strongly induced the ubiquitination of c-Myc and promoted protein degradation. c-Myc inhibition and apoptosis induction were additionally shown in hematologic malignant K562 cells, indicating the generality of the observed EMD effects. Altogether, we identified EMD as a novel potent compound targeting oncogenic c-Myc that may offer new opportunities for lung cancer treatment. SIGNIFICANCE STATEMENT: The deregulation of c-Myc is frequently associated with cancer progression. This study examined the effect of a new compound, N, N-bis (5-ethyl-2-hydroxybenzyl) methylamine (EMD), in targeting c-Myc in several lung cancer cell lines and drug-resistant primary lung cancer cells. EMD induced dramatic c-Myc degradation through a ubiquitin-proteasomal mechanism. The promising anticancer and c-Myc-targeted activities of EMD support its use in potential new approaches to treat c-Myc-driven cancer.


Assuntos
Antineoplásicos/síntese química , Neoplasias Pulmonares/metabolismo , Metilaminas/síntese química , Proteínas Proto-Oncogênicas c-myc/química , Proteínas Proto-Oncogênicas c-myc/metabolismo , Antineoplásicos/química , Antineoplásicos/farmacologia , Linhagem Celular Tumoral , Sobrevivência Celular , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Humanos , Células K562 , Neoplasias Pulmonares/tratamento farmacológico , Metilaminas/química , Metilaminas/farmacologia , Estrutura Molecular , Complexo de Endopeptidases do Proteassoma/metabolismo , Proteólise , Proteínas Proto-Oncogênicas c-myc/efeitos dos fármacos , Ubiquitina/metabolismo
12.
Mol Cell ; 79(2): 332-341.e7, 2020 07 16.
Artigo em Inglês | MEDLINE | ID: mdl-32521225

RESUMO

The Ddi1/DDI2 proteins are ubiquitin shuttling factors, implicated in a variety of cellular functions. In addition to ubiquitin-binding and ubiquitin-like domains, they contain a conserved region with similarity to retroviral proteases, but whether and how DDI2 functions as a protease has remained unknown. Here, we show that DDI2 knockout cells are sensitive to proteasome inhibition and accumulate high-molecular weight, ubiquitylated proteins that are poorly degraded by the proteasome. These proteins are targets for the protease activity of purified DDI2. No evidence for DDI2 acting as a de-ubiquitylating enzyme was uncovered, which could suggest that it cleaves the ubiquitylated protein itself. In support of this idea, cleavage of transcription factor NRF1 is known to require DDI2 activity in vivo. We show that DDI2 is indeed capable of cleaving NRF1 in vitro but only when NRF1 protein is highly poly-ubiquitylated. Together, these data suggest that DDI2 is a ubiquitin-directed endoprotease.


Assuntos
Ácido Aspártico Proteases/metabolismo , Fator 1 Nuclear Respiratório/metabolismo , Ubiquitina/metabolismo , Ácido Aspártico Proteases/genética , Sítios de Ligação , Sistemas CRISPR-Cas , Linhagem Celular , Técnicas de Inativação de Genes , Células HEK293 , Humanos , Biossíntese de Proteínas , Proteólise
13.
PLoS One ; 15(6): e0234708, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32555680

RESUMO

Fibroblast growth factor receptors (FGFRs) are frequently altered in a variety of human cancer cells and are overexpressed in hepatocellular carcinoma (HCC). Several literatures have proven that they are efficacious for HCC therapy, however, the underlying mechanism remains unclear. Here, we found FGFR4 was overexpressed in HCC cell lines HepG2 and Hep3B and we used PD173074, an FGFR4 inhibitor, to explore the role of FGFR4 and its underlying mechanism in these cell lines. The results showed that PD173074 significantly arrested HepG2 and Hep3B cells in G1 phase and inhibited cell proliferation. Furthermore, Western blot analysis revealed that PD173074 decreased the levels of P-FRS2α, P-ERK, CDK2, cyclin E and NF-κB (p65) in the nucleus while it increased the levels of ubiquitin and CUL3, an E3 ubiquitin ligase which involves in cyclin E degradation. Meanwhile, the data from RT-qPCR showed that PD173074 also decreased miR-141 level. In conclusion, these results suggest that FGFR4 is involved in HCC by ERK/CUL3/cyclin E signaling pathway, and the finding may provide a potential theoretical basis for treatment by targeting FGFR4 in HCC.


Assuntos
Proteínas Culina/metabolismo , Pontos de Checagem da Fase G1 do Ciclo Celular/efeitos dos fármacos , Pirimidinas/farmacologia , Ubiquitina/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Carcinoma Hepatocelular/metabolismo , Carcinoma Hepatocelular/patologia , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Proteínas Culina/antagonistas & inibidores , Proteínas Culina/genética , Ciclina E/metabolismo , Regulação para Baixo/efeitos dos fármacos , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Células Hep G2 , Humanos , Neoplasias Hepáticas/metabolismo , Neoplasias Hepáticas/patologia , Proteínas de Membrana/metabolismo , MicroRNAs/metabolismo , Interferência de RNA , RNA Interferente Pequeno/metabolismo , Receptor Tipo 4 de Fator de Crescimento de Fibroblastos/antagonistas & inibidores , Receptor Tipo 4 de Fator de Crescimento de Fibroblastos/metabolismo , Transdução de Sinais/efeitos dos fármacos , Fator de Transcrição RelA/antagonistas & inibidores , Fator de Transcrição RelA/genética , Fator de Transcrição RelA/metabolismo
14.
Nat Commun ; 11(1): 3234, 2020 06 26.
Artigo em Inglês | MEDLINE | ID: mdl-32591519

RESUMO

In shotgun proteomics, the analysis of label-free quantification experiments is typically limited by the identification rate and the noise level in the quantitative data. This generally causes a low sensitivity in differential expression analysis. Here, we propose a quantification-first approach for peptides that reverses the classical identification-first workflow, thereby preventing valuable information from being discarded in the identification stage. Specifically, we introduce a method, Quandenser, that applies unsupervised clustering on both MS1 and MS2 level to summarize all analytes of interest without assigning identities. This reduces search time due to the data reduction. We can now employ open modification and de novo searches to identify analytes of interest that would have gone unnoticed in traditional pipelines. Quandenser+Triqler outperforms the state-of-the-art method MaxQuant+Perseus, consistently reporting more differentially abundant proteins for all tested datasets. Software is available for all major operating systems at https://github.com/statisticalbiotechnology/quandenser, under Apache 2.0 license.


Assuntos
Proteômica , Análise por Conglomerados , Bases de Dados de Proteínas , Proteínas de Escherichia coli/metabolismo , Células HeLa , Humanos , Peptídeos/metabolismo , Complexo de Endopeptidases do Proteassoma/metabolismo , Proteoma/metabolismo , Saccharomyces cerevisiae/metabolismo , Software , Ubiquitina/metabolismo
15.
Proc Natl Acad Sci U S A ; 117(25): 14220-14230, 2020 06 23.
Artigo em Inglês | MEDLINE | ID: mdl-32513741

RESUMO

Because raising cAMP enhances 26S proteasome activity and the degradation of cell proteins, including the selective breakdown of misfolded proteins, we investigated whether agents that raise cGMP may also regulate protein degradation. Treating various cell lines with inhibitors of phosphodiesterase 5 or stimulators of soluble guanylyl cyclase rapidly enhanced multiple proteasome activities and cellular levels of ubiquitinated proteins by activating protein kinase G (PKG). PKG stimulated purified 26S proteasomes by phosphorylating a different 26S component than is modified by protein kinase A. In cells and cell extracts, raising cGMP also enhanced within minutes ubiquitin conjugation to cell proteins. Raising cGMP, like raising cAMP, stimulated the degradation of short-lived cell proteins, but unlike cAMP, also markedly increased proteasomal degradation of long-lived proteins (the bulk of cell proteins) without affecting lysosomal proteolysis. We also tested if raising cGMP, like cAMP, can promote the degradation of mutant proteins that cause neurodegenerative diseases. Treating zebrafish models of tauopathies or Huntington's disease with a PDE5 inhibitor reduced the levels of the mutant huntingtin and tau proteins, cell death, and the resulting morphological abnormalities. Thus, PKG rapidly activates cytosolic proteasomes, protein ubiquitination, and overall protein degradation, and agents that raise cGMP may help combat the progression of neurodegenerative diseases.


Assuntos
Proteínas Quinases Dependentes de GMP Cíclico/metabolismo , GMP Cíclico/metabolismo , Doenças Neurodegenerativas/metabolismo , Complexo de Endopeptidases do Proteassoma/metabolismo , Proteólise , Animais , Animais Geneticamente Modificados , AMP Cíclico/metabolismo , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Modelos Animais de Doenças , Humanos , Fosforilação , Tauopatias , Ubiquitina/metabolismo , Proteínas Ubiquitinadas/metabolismo , Ubiquitinação , Peixe-Zebra , Proteínas tau/metabolismo
16.
Nat Commun ; 11(1): 3106, 2020 06 19.
Artigo em Inglês | MEDLINE | ID: mdl-32561765

RESUMO

Nonsense-mediated mRNA decay (NMD) typifies an mRNA surveillance pathway. Because NMD necessitates a translation event to recognize a premature termination codon on mRNAs, truncated misfolded polypeptides (NMD-polypeptides) could potentially be generated from NMD substrates as byproducts. Here, we show that when the ubiquitin-proteasome system is overwhelmed, various misfolded polypeptides including NMD-polypeptides accumulate in the aggresome: a perinuclear nonmembranous compartment eventually cleared by autophagy. Hyperphosphorylation of the key NMD factor UPF1 is required for selective targeting of the misfolded polypeptide aggregates toward the aggresome via the CTIF-eEF1A1-DCTN1 complex: the aggresome-targeting cellular machinery. Visualization at a single-particle level reveals that UPF1 increases the frequency and fidelity of movement of CTIF aggregates toward the aggresome. Furthermore, the apoptosis induced by proteotoxic stresses is suppressed by UPF1 hyperphosphorylation. Altogether, our data provide evidence that UPF1 functions in the regulation of a protein surveillance as well as an mRNA quality control.


Assuntos
Degradação do RNAm Mediada por Códon sem Sentido , Complexo de Endopeptidases do Proteassoma/metabolismo , RNA Helicases/metabolismo , RNA Mensageiro/metabolismo , Transativadores/metabolismo , Resposta a Proteínas não Dobradas/genética , Autofagia , Códon sem Sentido , Complexo Dinactina/metabolismo , Fatores de Iniciação em Eucariotos/metabolismo , Células HEK293 , Células HeLa , Humanos , Imagem Molecular , Fator 1 de Elongação de Peptídeos/metabolismo , Fosforilação , Agregados Proteicos/genética , Imagem Individual de Molécula , Ubiquitina/metabolismo
17.
Nat Commun ; 11(1): 2751, 2020 06 02.
Artigo em Inglês | MEDLINE | ID: mdl-32488130

RESUMO

The bacterial effector MavC catalyzes non-canonical ubiquitination of host E2 enzyme UBE2N without engaging any of the conventional ubiquitination machinery, thereby abolishing UBE2N's function in forming K63-linked ubiquitin (Ub) chains and dampening NF-кB signaling. We now report the structures of MavC in complex with conjugated UBE2N~Ub and an inhibitor protein Lpg2149, as well as the structure of its ortholog, MvcA, bound to Lpg2149. Recognition of UBE2N and Ub depends on several unique features of MavC, which explains the inability of MvcA to catalyze ubiquitination. Unexpectedly, MavC and MvcA also possess deubiquitinase activity against MavC-mediated ubiquitination, highlighting MavC as a unique enzyme possessing deamidation, ubiquitination, and deubiquitination activities. Further, Lpg2149 directly binds and inhibits both MavC and MvcA by disrupting the interactions between enzymes and Ub. These results provide detailed insights into catalysis and regulation of MavC-type enzymes and the molecular mechanisms of this non-canonical ubiquitination machinery.


Assuntos
Bactérias/metabolismo , Enzimas de Conjugação de Ubiquitina/química , Enzimas de Conjugação de Ubiquitina/metabolismo , Ubiquitina/metabolismo , Ubiquitinação , Catálise , Cristalografia por Raios X , Humanos , Modelos Moleculares , NF-kappa B/metabolismo , Conformação Proteica , Domínios e Motivos de Interação entre Proteínas
18.
Nat Commun ; 11(1): 2846, 2020 06 05.
Artigo em Inglês | MEDLINE | ID: mdl-32503993

RESUMO

Based on extensive structural analysis it was proposed that RING E3 ligases prime the E2~ubiquitin conjugate (E2~Ub) for catalysis by locking it into a closed conformation, where ubiquitin is folded back onto the E2 exposing the restrained thioester bond to attack by substrate nucleophile. However the proposal that the RING dependent closed conformation of E2~Ub represents the active form that mediates ubiquitin transfer has yet to be experimentally tested. To test this hypothesis we use single molecule Förster Resonance Energy Transfer (smFRET) to measure the conformation of a FRET labelled E2~Ub conjugate, which distinguishes between closed and alternative conformations. We describe a real-time FRET assay with a thioester linked E2~Ub conjugate to monitor single ubiquitination events and demonstrate that ubiquitin is transferred to substrate from the closed conformation. These findings are likely to be relevant to all RING E3 catalysed reactions ligating ubiquitin and other ubiquitin-like proteins (Ubls) to substrates.


Assuntos
Proteínas Nucleares/metabolismo , Fatores de Transcrição/metabolismo , Enzimas de Conjugação de Ubiquitina/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Ubiquitina/metabolismo , Cristalografia por Raios X , Transferência Ressonante de Energia de Fluorescência , Estrutura Terciária de Proteína , Domínios RING Finger , Imagem Individual de Molécula , Ubiquitinação
19.
Mol Cell ; 79(1): 54-67.e7, 2020 07 02.
Artigo em Inglês | MEDLINE | ID: mdl-32521226

RESUMO

Exposure of cells to heat or oxidative stress causes misfolding of proteins. To avoid toxic protein aggregation, cells have evolved nuclear and cytosolic protein quality control (PQC) systems. In response to proteotoxic stress, cells also limit protein synthesis by triggering transient storage of mRNAs and RNA-binding proteins (RBPs) in cytosolic stress granules (SGs). We demonstrate that the SUMO-targeted ubiquitin ligase (StUbL) pathway, which is part of the nuclear proteostasis network, regulates SG dynamics. We provide evidence that inactivation of SUMO deconjugases under proteotoxic stress initiates SUMO-primed, RNF4-dependent ubiquitylation of RBPs that typically condense into SGs. Impairment of SUMO-primed ubiquitylation drastically delays SG resolution upon stress release. Importantly, the StUbL system regulates compartmentalization of an amyotrophic lateral sclerosis (ALS)-associated FUS mutant in SGs. We propose that the StUbL system functions as surveillance pathway for aggregation-prone RBPs in the nucleus, thereby linking the nuclear and cytosolic axis of proteotoxic stress response.


Assuntos
Esclerose Amiotrófica Lateral/patologia , Núcleo Celular/metabolismo , Grânulos Citoplasmáticos/metabolismo , Proteínas Nucleares/metabolismo , Proteínas de Ligação a RNA/metabolismo , Proteína SUMO-1/metabolismo , Fatores de Transcrição/metabolismo , Ubiquitina/metabolismo , Esclerose Amiotrófica Lateral/genética , Núcleo Celular/genética , Células HeLa , Resposta ao Choque Térmico , Humanos , Mutação , Proteínas Nucleares/genética , Proteólise , Proteína FUS de Ligação a RNA/genética , Proteínas de Ligação a RNA/genética , Proteína SUMO-1/genética , Sumoilação , Fatores de Transcrição/genética , Ubiquitinação
20.
Nat Commun ; 11(1): 2793, 2020 06 03.
Artigo em Inglês | MEDLINE | ID: mdl-32493905

RESUMO

Biology utilizes multiple strategies, including sequestration in lipid vesicles, to raise the rate and specificity of chemical reactions through increases in effective molarity of reactants. We show that micelle-assisted reaction can facilitate native chemical ligations (NCLs) between a peptide-thioester - in which the thioester leaving group contains a lipid-like alkyl chain - and a Cys-peptide modified by a lipid-like moiety. Hydrophobic lipid modification of each peptide segment promotes the formation of mixed micelles, bringing the reacting peptides into close proximity and increasing the reaction rate. The approach enables the rapid synthesis of polypeptides using low concentrations of reactants without the need for thiol catalysts. After NCL, the lipid moiety is removed to yield an unmodified ligation product. This micelle-based methodology facilitates the generation of natural peptides, like Magainin 2, and the derivatization of the protein Ubiquitin. Formation of mixed micelles from lipid-modified reactants shows promise for accelerating chemical reactions in a traceless manner.


Assuntos
Lipídeos/química , Micelas , Peptídeos/química , Tensoativos/química , Sequência de Aminoácidos , Cinética , Luz , Magaininas/síntese química , Magaininas/química , Peptídeos/síntese química , Ubiquitina/metabolismo
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