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1.
Nucleic Acids Res ; 52(2): 784-800, 2024 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-38000394

RESUMO

Activation-induced cytidine deaminase (AID) interacts with replication protein A (RPA), the major ssDNA-binding protein, to promote deamination of cytosine to uracil in transcribed immunoglobulin (Ig) genes. Uracil-DNA glycosylase (UNG) acts in concert with AID during Ig diversification. In addition, UNG preserves genome integrity by base-excision repair (BER) in the overall genome. How UNG is regulated to support both mutagenic processing and error-free repair remains unknown. UNG is expressed as two isoforms, UNG1 and UNG2, which both contain an RPA-binding helix that facilitates uracil excision from RPA-coated ssDNA. However, the impact of this interaction in antibody diversification and genome maintenance has not been investigated. Here, we generated B-cell clones with targeted mutations in the UNG RPA-binding motif, and analysed class switch recombination (CSR), mutation frequency (5' Ig Sµ), and genomic uracil in clones representing seven Ung genotypes. We show that the UNG:RPA interaction plays a crucial role in both CSR and repair of AID-induced uracil at the Ig loci. By contrast, the interaction had no significant impact on total genomic uracil levels. Thus, RPA coordinates UNG during CSR and pre-replicative repair of mutagenic uracil in ssDNA but is not essential in post-replicative and canonical BER of uracil in dsDNA.


Assuntos
Proteína de Replicação A , Uracila-DNA Glicosidase , Citidina Desaminase/genética , Citidina Desaminase/metabolismo , Reparo do DNA/genética , DNA de Cadeia Simples/genética , Switching de Imunoglobulina/genética , Isotipos de Imunoglobulinas/genética , Imunoglobulinas/genética , Mutagênicos , Proteína de Replicação A/genética , Proteína de Replicação A/metabolismo , Uracila/metabolismo , Uracila-DNA Glicosidase/genética , Uracila-DNA Glicosidase/metabolismo , Humanos , Animais , Camundongos
2.
J Transl Med ; 22(1): 548, 2024 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-38849800

RESUMO

BACKGROUND: Despite significant advancements in treatment strategies, multiple myeloma remains incurable. Additionally, there is a distinct lack of reliable biomarkers that can guide initial treatment decisions and help determine suitable replacement or adjuvant therapies when relapse ensues due to acquired drug resistance. METHODS: To define specific proteins and pathways involved in the progression of monoclonal gammopathy of undetermined significance (MGUS) to multiple myeloma (MM), we have applied super-SILAC quantitative proteomic analysis to CD138 + plasma cells from 9 individuals with MGUS and 37 with MM. RESULTS: Unsupervised hierarchical clustering defined three groups: MGUS, MM, and MM with an MGUS-like proteome profile (ML) that may represent a group that has recently transformed to MM. Statistical analysis identified 866 differentially expressed proteins between MM and MGUS, and 189 between MM and ML, 177 of which were common between MGUS and ML. Progression from MGUS to MM is accompanied by upregulated EIF2 signaling, DNA repair, and proteins involved in translational quality control, whereas integrin- and actin cytoskeletal signaling and cell surface markers are downregulated. CONCLUSION: Compared to the premalignant plasma cells in MGUS, malignant MM cells apparently have mobilized several pathways that collectively contribute to ensure translational fidelity and to avoid proteotoxic stress, especially in the ER. The overall reduced expression of immunoglobulins and surface antigens contribute to this and may additionally mediate evasion from recognition by the immune apparatus. Our analyses identified a range of novel biomarkers with potential prognostic and therapeutic value, which will undergo further evaluation to determine their clinical significance.


Assuntos
Progressão da Doença , Gamopatia Monoclonal de Significância Indeterminada , Mieloma Múltiplo , Humanos , Mieloma Múltiplo/imunologia , Mieloma Múltiplo/patologia , Gamopatia Monoclonal de Significância Indeterminada/imunologia , Proteômica , Masculino , Feminino , Biossíntese de Proteínas , Pessoa de Meia-Idade , Idoso , Análise por Conglomerados , Plasmócitos/imunologia , Plasmócitos/patologia , Plasmócitos/metabolismo , Transdução de Sinais , Proteoma/metabolismo , Controle de Qualidade
3.
EMBO J ; 38(1)2019 01 03.
Artigo em Inglês | MEDLINE | ID: mdl-30523148

RESUMO

During active DNA demethylation, 5-methylcytosine (5mC) is oxidized by TET proteins to 5-formyl-/5-carboxylcytosine (5fC/5caC) for replacement by unmethylated C by TDG-initiated DNA base excision repair (BER). Base excision generates fragile abasic sites (AP-sites) in DNA and has to be coordinated with subsequent repair steps to limit accumulation of genome destabilizing secondary DNA lesions. Here, we show that 5fC/5caC is generated at a high rate in genomes of differentiating mouse embryonic stem cells and that SUMOylation and the BER protein XRCC1 play critical roles in orchestrating TDG-initiated BER of these lesions. SUMOylation of XRCC1 facilitates physical interaction with TDG and promotes the assembly of a TDG-BER core complex. Within this TDG-BERosome, SUMO is transferred from XRCC1 and coupled to the SUMO acceptor lysine in TDG, promoting its dissociation while assuring the engagement of the BER machinery to complete demethylation. Although well-studied, the biological importance of TDG SUMOylation has remained obscure. Here, we demonstrate that SUMOylation of TDG suppresses DNA strand-break accumulation and toxicity to PARP inhibition in differentiating mESCs and is essential for neural lineage commitment.


Assuntos
Diferenciação Celular/genética , Desmetilação do DNA , Reparo do DNA/fisiologia , Células-Tronco Embrionárias/fisiologia , Sumoilação/fisiologia , Proteína 1 Complementadora Cruzada de Reparo de Raio-X/metabolismo , 5-Metilcitosina/metabolismo , Animais , Células Cultivadas , Citosina/análogos & derivados , Citosina/metabolismo , Humanos , Camundongos , Complexos Multiproteicos/metabolismo , Multimerização Proteica/fisiologia
4.
Nature ; 551(7680): 389-393, 2017 11 16.
Artigo em Inglês | MEDLINE | ID: mdl-29144457

RESUMO

DNA repair is essential to prevent the cytotoxic or mutagenic effects of various types of DNA lesions, which are sensed by distinct pathways to recruit repair factors specific to the damage type. Although biochemical mechanisms for repairing several forms of genomic insults are well understood, the upstream signalling pathways that trigger repair are established for only certain types of damage, such as double-stranded breaks and interstrand crosslinks. Understanding the upstream signalling events that mediate recognition and repair of DNA alkylation damage is particularly important, since alkylation chemotherapy is one of the most widely used systemic modalities for cancer treatment and because environmental chemicals may trigger DNA alkylation. Here we demonstrate that human cells have a previously unrecognized signalling mechanism for sensing damage induced by alkylation. We find that the alkylation repair complex ASCC (activating signal cointegrator complex) relocalizes to distinct nuclear foci specifically upon exposure of cells to alkylating agents. These foci associate with alkylated nucleotides, and coincide spatially with elongating RNA polymerase II and splicing components. Proper recruitment of the repair complex requires recognition of K63-linked polyubiquitin by the CUE (coupling of ubiquitin conjugation to ER degradation) domain of the subunit ASCC2. Loss of this subunit impedes alkylation adduct repair kinetics and increases sensitivity to alkylating agents, but not other forms of DNA damage. We identify RING finger protein 113A (RNF113A) as the E3 ligase responsible for upstream ubiquitin signalling in the ASCC pathway. Cells from patients with X-linked trichothiodystrophy, which harbour a mutation in RNF113A, are defective in ASCC foci formation and are hypersensitive to alkylating agents. Together, our work reveals a previously unrecognized ubiquitin-dependent pathway induced specifically to repair alkylation damage, shedding light on the molecular mechanism of X-linked trichothiodystrophy.


Assuntos
Enzimas AlkB/metabolismo , Adutos de DNA/metabolismo , Reparo do DNA , Complexos Multiproteicos/metabolismo , Transdução de Sinais , Síndromes de Tricotiodistrofia/genética , Ubiquitina/metabolismo , Homólogo AlkB 3 da Dioxigenase Dependente de alfa-Cetoglutarato/metabolismo , Alquilantes/farmacologia , Alquilação , Sequência de Aminoácidos , Adutos de DNA/química , DNA Helicases/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Retículo Endoplasmático/metabolismo , Genes Ligados ao Cromossomo X , Humanos , Cinética , Modelos Moleculares , Proteínas Nucleares/química , Proteínas Nucleares/metabolismo , Poliubiquitina/metabolismo , RNA Polimerase II/metabolismo , Splicing de RNA , Síndromes de Tricotiodistrofia/metabolismo , Síndromes de Tricotiodistrofia/patologia , Ubiquitinação
5.
Nucleic Acids Res ; 49(7): 3948-3966, 2021 04 19.
Artigo em Inglês | MEDLINE | ID: mdl-33784377

RESUMO

Uracil occurs at replication forks via misincorporation of deoxyuridine monophosphate (dUMP) or via deamination of existing cytosines, which occurs 2-3 orders of magnitude faster in ssDNA than in dsDNA and is 100% miscoding. Tethering of UNG2 to proliferating cell nuclear antigen (PCNA) allows rapid post-replicative removal of misincorporated uracil, but potential 'pre-replicative' removal of deaminated cytosines in ssDNA has been questioned since this could mediate mutagenic translesion synthesis and induction of double-strand breaks. Here, we demonstrate that uracil-DNA glycosylase (UNG), but not SMUG1 efficiently excises uracil from replication protein A (RPA)-coated ssDNA and that this depends on functional interaction between the flexible winged-helix (WH) domain of RPA2 and the N-terminal RPA-binding helix in UNG. This functional interaction is promoted by mono-ubiquitination and diminished by cell-cycle regulated phosphorylations on UNG. Six other human proteins bind the RPA2-WH domain, all of which are involved in DNA repair and replication fork remodelling. Based on this and the recent discovery of the AP site crosslinking protein HMCES, we propose an integrated model in which templated repair of uracil and potentially other mutagenic base lesions in ssDNA at the replication fork, is orchestrated by RPA. The UNG:RPA2-WH interaction may also play a role in adaptive immunity by promoting efficient excision of AID-induced uracils in transcribed immunoglobulin loci.


Assuntos
DNA Glicosilases/metabolismo , Replicação do DNA , DNA de Cadeia Simples/metabolismo , Proteína de Replicação A/metabolismo , Uracila/metabolismo , Sítios de Ligação , Humanos , Ligação Proteica , Proteínas Recombinantes/metabolismo
6.
FASEB J ; 35(7): e21714, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-34118107

RESUMO

We tested the hypothesis that cancer cachexia progression would induce oxidative post-translational modifications (Ox-PTMs) associated with skeletal muscle wasting, with different responses in muscles with the prevalence of glycolytic and oxidative fibers. We used cysteine-specific isotopic coded affinity tags (OxICAT) and gel-free mass spectrometry analysis to investigate the cysteine Ox-PTMs profile in the proteome of both plantaris (glycolytic) and soleus (oxidative) muscles in tumor-bearing and control rats. Histological analysis revealed muscle atrophy in type II fibers in plantaris muscle, with no changes in plantaris type I fibers and no differences in both soleus type I and II fibers in tumor-bearing rats when compared to healthy controls. Tumor progression altered the Ox-PTMs profile in both plantaris and soleus. However, pathway analysis including the differentially oxidized proteins revealed tricarboxylic acid cycle and oxidative phosphorylation as main affected pathways in plantaris muscle from tumor-bearing rats, while the same analysis did not show main metabolic pathways affected in the soleus muscle. In addition, cancer progression affected several metabolic parameters such as ATP levels and markers of oxidative stress associated with muscle atrophy in plantaris muscle, but not in soleus. However, isolated soleus from tumor-bearing rats had a reduced force production capacity when compared to controls. These novel findings demonstrate that tumor-bearing rats have severe muscle atrophy exclusively in glycolytic fibers. Cancer progression is associated with cysteine Ox-PTMs in the skeletal muscle, but these modifications affect different pathways in a glycolytic muscle compared to an oxidative muscle, indicating that intrinsic muscle oxidative capacity determines the response to cancer cachectic effects.


Assuntos
Músculo Esquelético/patologia , Atrofia Muscular/patologia , Neoplasias/patologia , Estresse Oxidativo/fisiologia , Animais , Caquexia/patologia , Progressão da Doença , Glicólise/fisiologia , Masculino , Fibras Musculares de Contração Rápida/patologia , Fibras Musculares de Contração Lenta/patologia , Oxirredução , Fosforilação Oxidativa , Ratos , Ratos Wistar
7.
Nucleic Acids Res ; 48(2): 830-846, 2020 01 24.
Artigo em Inglês | MEDLINE | ID: mdl-31799605

RESUMO

RNA methylations are essential both for RNA structure and function, and are introduced by a number of distinct methyltransferases (MTases). In recent years, N6-methyladenosine (m6A) modification of eukaryotic mRNA has been subject to intense studies, and it has been demonstrated that m6A is a reversible modification that regulates several aspects of mRNA function. However, m6A is also found in other RNAs, such as mammalian 18S and 28S ribosomal RNAs (rRNAs), but the responsible MTases have remained elusive. 28S rRNA carries a single m6A modification, found at position A4220 (alternatively referred to as A4190) within a stem-loop structure, and here we show that the MTase ZCCHC4 is the enzyme responsible for introducing this modification. Accordingly, we found that ZCCHC4 localises to nucleoli, the site of ribosome assembly, and that proteins involved in RNA metabolism are overrepresented in the ZCCHC4 interactome. Interestingly, the absence of m6A4220 perturbs codon-specific translation dynamics and shifts gene expression at the translational level. In summary, we establish ZCCHC4 as the enzyme responsible for m6A modification of human 28S rRNA, and demonstrate its functional significance in mRNA translation.


Assuntos
Adenosina/análogos & derivados , Metiltransferases/genética , RNA Mensageiro/genética , RNA Ribossômico 28S/genética , Adenosina/química , Adenosina/genética , Catálise , Humanos , Metilação , Metiltransferases/química , Ligação Proteica/genética , RNA Ribossômico 28S/química
8.
J Transl Med ; 19(1): 287, 2021 07 03.
Artigo em Inglês | MEDLINE | ID: mdl-34217309

RESUMO

BACKGROUND: Reversible enzymatic methylation of mammalian mRNA is widespread and serves crucial regulatory functions, but little is known to what degree chemical alkylators mediate overlapping modifications and whether cells distinguish aberrant from canonical methylations. METHODS: Here we use quantitative mass spectrometry to determine the fate of chemically induced methylbases in the mRNA of human cells. Concomitant alteration in the mRNA binding proteome was analyzed by SILAC mass spectrometry. RESULTS: MMS induced prominent direct mRNA methylations that were chemically identical to endogenous methylbases. Transient loss of 40S ribosomal proteins from isolated mRNA suggests that aberrant methylbases mediate arrested translational initiation and potentially also no-go decay of the affected mRNA. Four proteins (ASCC3, YTHDC2, TRIM25 and GEMIN5) displayed increased mRNA binding after MMS treatment. ASCC3 is a binding partner of the DNA/RNA demethylase ALKBH3 and was recently shown to promote disassembly of collided ribosomes as part of the ribosome quality control (RQC) trigger complex. We find that ASCC3-deficient cells display delayed removal of MMS-induced 1-methyladenosine (m1A) and 3-methylcytosine (m3C) from mRNA and impaired formation of MMS-induced P-bodies. CONCLUSIONS: Our findings conform to a model in which ASCC3-mediated disassembly of collided ribosomes allows demethylation of aberrant m1A and m3C by ALKBH3. Our findings constitute first evidence of selective sanitation of aberrant mRNA methylbases over their endogenous counterparts and warrant further studies on RNA-mediated effects of chemical alkylators commonly used in the clinic.


Assuntos
Citosina , Ribossomos , Adenosina/análogos & derivados , Homólogo AlkB 3 da Dioxigenase Dependente de alfa-Cetoglutarato , Animais , Citosina/análogos & derivados , DNA Helicases , Humanos , RNA Helicases , RNA Mensageiro/genética , Fatores de Transcrição , Proteínas com Motivo Tripartido , Ubiquitina-Proteína Ligases
9.
Int J Mol Sci ; 22(8)2021 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-33921666

RESUMO

DNA of all living cells undergoes continuous structural and chemical alterations resulting from fundamental cellular metabolic processes and reactivity of normal cellular metabolites and constituents. Examples include enzymatically oxidized bases, aberrantly methylated bases, and deaminated bases, the latter largely uracil from deaminated cytosine. In addition, the non-canonical DNA base uracil may result from misincorporated dUMP. Furthermore, uracil generated by deamination of cytosine in DNA is not always damage as it is also an intermediate in normal somatic hypermutation (SHM) and class shift recombination (CSR) at the Ig locus of B-cells in adaptive immunity. Many of the modifications alter base-pairing properties and may thus cause replicative and transcriptional mutagenesis. The best known and most studied epigenetic mark in DNA is 5-methylcytosine (5mC), generated by a methyltransferase that uses SAM as methyl donor, usually in CpG contexts. Oxidation products of 5mC are now thought to be intermediates in active demethylation as well as epigenetic marks in their own rights. The aim of this review is to describe the endogenous processes that surround the generation and removal of the most common types of DNA nucleobase modifications, namely, uracil and certain epigenetic modifications, together with their role in the development of hematological malignances. We also discuss what dictates whether the presence of an altered nucleobase is defined as damage or a natural modification.


Assuntos
Uracila/metabolismo , Animais , Citidina Desaminase/genética , Citidina Desaminase/metabolismo , Metilação de DNA/fisiologia , Reparo do DNA/genética , Reparo do DNA/fisiologia , Epigênese Genética/genética , Epigenômica/métodos , Humanos
10.
Int J Mol Sci ; 22(10)2021 May 19.
Artigo em Inglês | MEDLINE | ID: mdl-34069552

RESUMO

There is little in vitro data available on long-term effects of TiO2 exposure. Such data are important for improving the understanding of underlying mechanisms of adverse health effects of TiO2. Here, we exposed pulmonary epithelial cells to two doses (0.96 and 1.92 µg/cm2) of TiO2 for 13 weeks and effects on cell cycle and cell death mechanisms, i.e., apoptosis and autophagy were determined after 4, 8 and 13 weeks of exposure. Changes in telomere length, cellular protein levels and lipid classes were also analyzed at 13 weeks of exposure. We observed that the TiO2 exposure increased the fraction of cells in G1-phase and reduced the fraction of cells in G2-phase, which was accompanied by an increase in the fraction of late apoptotic/necrotic cells. This corresponded with an induced expression of key apoptotic proteins i.e., BAD and BAX, and an accumulation of several lipid classes involved in cellular stress and apoptosis. These findings were further supported by quantitative proteome profiling data showing an increase in proteins involved in cell stress and genomic maintenance pathways following TiO2 exposure. Altogether, we suggest that cell stress response and cell death pathways may be important molecular events in long-term health effects of TiO2.


Assuntos
Células Epiteliais Alveolares/metabolismo , Titânio/efeitos adversos , Células Epiteliais Alveolares/efeitos dos fármacos , Apoptose/efeitos dos fármacos , Autofagia/efeitos dos fármacos , Ciclo Celular/efeitos dos fármacos , Divisão Celular , Linhagem Celular , Células Epiteliais/metabolismo , Expressão Gênica/genética , Perfilação da Expressão Gênica/métodos , Humanos , Pulmão/metabolismo , Nanopartículas Metálicas/efeitos adversos , Nanopartículas/efeitos adversos , Estresse Oxidativo/efeitos dos fármacos , Proteômica/métodos , Alvéolos Pulmonares/efeitos dos fármacos , Alvéolos Pulmonares/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Titânio/metabolismo , Transcriptoma/genética
11.
J Transl Med ; 18(1): 310, 2020 08 10.
Artigo em Inglês | MEDLINE | ID: mdl-32778120

RESUMO

BACKGROUND: HIV-1 Vpr encodes a 14 kDa protein that has been implicated in viral pathogenesis through modulation of several host cell functions. In addition to pro-apoptotic and cytostatic properties, Vpr can redirect cellular E3 ubiquitin ligases (such as DCAF1-Cul4A E3 ligase complex) to target many host proteins and interfere with their functions. Among them, Vpr binds the uracil DNA glycosylase UNG2, which controls genome uracilation, and induces its specific degradation leading to loss of uracil removal activity in infected cells. Considering the essential role of UNG2 in antibody diversification in B-cells, we evaluated the impact of Vpr on UNG2 fate in B lymphocytes and examined the functional consequences of UNG2 modulations on class switch recombination (CSR). METHODS: The impact of Vpr-induced UNG2 deregulation on CSR proficiency was evaluated by using virus-like particles able to deliver Vpr protein to target cells including the murine model CSR B cell line CH12F3 and mouse primary B-cells. Co-culture experiments were used to re-examine the ability of Vpr to be released by HIV-1 infected cells and to effectively accumulate in bystander B-cells. Vpr-mediated UNG2 modulations were monitored by following UNG2 protein abundance and uracil removal enzymatic activity. RESULTS: In this study we report the ability of Vpr to reduce immunoglobulin class switch recombination (CSR) in immortalized and primary mouse B-cells through the degradation of UNG2. We also emphasize that Vpr is released by producing cells and penetrates bystander B lymphocytes. CONCLUSIONS: This work therefore opens up new perspectives to study alterations of the B-cell response by using Vpr as a specific CSR blocking tool. Moreover, our results raise the question of whether extracellular HIV-1 Vpr detected in some patients may manipulate the antibody diversification process that engineers an adapted response against pathogenic intruders and thereby contribute to the intrinsic B-cell humoral defect reported in infected patients.


Assuntos
HIV-1 , Animais , Linfócitos B/metabolismo , Proteínas Culina/genética , Proteínas Culina/metabolismo , Reparo do DNA , Humanos , Camundongos , Produtos do Gene vpr do Vírus da Imunodeficiência Humana/genética
12.
J Transl Med ; 18(1): 159, 2020 04 07.
Artigo em Inglês | MEDLINE | ID: mdl-32264925

RESUMO

BACKGROUND: HDAC inhibitors (HDACi) belong to a new group of chemotherapeutics that are increasingly used in the treatment of lymphocyte-derived malignancies, but their mechanisms of action remain poorly understood. Here we aimed to identify novel protein targets of HDACi in B- and T-lymphoma cell lines and to verify selected candidates across several mammalian cell lines. METHODS: Jurkat T- and SUDHL5 B-lymphocytes were treated with the HDACi SAHA (vorinostat) prior to SILAC-based quantitative proteome analysis. Selected differentially expressed proteins were verified by targeted mass spectrometry, RT-PCR and western analysis in multiple mammalian cell lines. Genomic uracil was quantified by LC-MS/MS, cell cycle distribution analyzed by flow cytometry and class switch recombination monitored by FACS in murine CH12F3 cells. RESULTS: SAHA treatment resulted in differential expression of 125 and 89 proteins in Jurkat and SUDHL5, respectively, of which 19 were commonly affected. Among these were several oncoproteins and tumor suppressors previously not reported to be affected by HDACi. Several key enzymes determining the cellular dUTP/dTTP ratio were downregulated and in both cell lines we found robust depletion of UNG2, the major glycosylase in genomic uracil sanitation. UNG2 depletion was accompanied by hyperacetylation and mediated by increased proteasomal degradation independent of cell cycle stage. UNG2 degradation appeared to be ubiquitous and was observed across several mammalian cell lines of different origin and with several HDACis. Loss of UNG2 was accompanied by 30-40% increase in genomic uracil in freely cycling HEK cells and reduced immunoglobulin class-switch recombination in murine CH12F3 cells. CONCLUSION: We describe several oncoproteins and tumor suppressors previously not reported to be affected by HDACi in previous transcriptome analyses, underscoring the importance of proteome analysis to identify cellular effectors of HDACi treatment. The apparently ubiquitous depletion of UNG2 and PCLAF establishes DNA base excision repair and translesion synthesis as novel pathways affected by HDACi treatment. Dysregulated genomic uracil homeostasis may aid interpretation of HDACi effects in cancer cells and further advance studies on this class of inhibitors in the treatment of APOBEC-expressing tumors, autoimmune disease and HIV-1.


Assuntos
Inibidores de Histona Desacetilases , Uracila , Animais , Linhagem Celular , Cromatografia Líquida , Genômica , Inibidores de Histona Desacetilases/farmacologia , Camundongos , Proteínas Oncogênicas , Linfócitos T , Espectrometria de Massas em Tandem , Uracila/farmacologia
13.
Hum Mol Genet ; 26(6): 1031-1040, 2017 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-28007905

RESUMO

Recessive loss of function of the neuronal ubiquitin hydrolase UCHL1 has been implicated in early-onset progressive neurodegeneration (MIM no. 615491), so far only in one family. In this study a second family is characterized, and the functional consequences of the identified mutations in UCHL1 are explored. Three siblings developed childhood-onset optic atrophy, followed by spasticity and ataxia. Whole exome sequencing identified compound heterozygous variants in UCHL1, c.533G > A (p.Arg178Gln) and c.647C > A (p.Ala216Asp), cosegregating with the phenotype. Enzymatic activity of purified recombinant proteins analysed by ubiquitin hydrolase assays showed a 4-fold increased hydrolytic activity of the recombinant UCHL1 mutant Arg178Gln compared to wild type, whereas the Ala216Asp protein was insoluble. Structural 3D analysis of UCHL1 by computer modelling suggests that Arg178 is a rate-controlling residue in catalysis which is partly abolished in the Arg178Gln mutant and, consequently, the Arg178Gln mutant increases the enzymatic turnover. UCHL1 protein levels in fibroblasts measured by targeted mass spectrometry showed a total amount of UCHL1 in control fibroblasts about 4-fold higher than in the patients. Hence, studies of the identified missense variants reveal surprisingly different functional consequences as the insoluble Ala216Asp variant leads to loss of function, whereas the Arg178Gln leads to increased enzyme activity. The reported patients have remarkably preserved cognition, and we propose that the increased enzyme activity of the Arg178Gln variant offers a protective effect on cognitive function. This study establishes the importance of UCHL1 in neurodegeneration, provides new mechanistic insight about ubiquitin processing, and underlines the complexity of the different roles of UCHL1.


Assuntos
Ataxia/genética , Degeneração Neural/genética , Atrofia Óptica/genética , Proteínas Recombinantes/genética , Ubiquitina Tiolesterase/genética , Idoso , Animais , Ataxia/diagnóstico por imagem , Ataxia/fisiopatologia , Modelos Animais de Doenças , Exoma , Feminino , Heterozigoto , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Masculino , Pessoa de Meia-Idade , Mutação , Degeneração Neural/diagnóstico por imagem , Degeneração Neural/fisiopatologia , Atrofia Óptica/diagnóstico por imagem , Atrofia Óptica/fisiopatologia , Conformação Proteica , Proteínas Recombinantes/química , Irmãos , Relação Estrutura-Atividade , Ubiquitina Tiolesterase/química
14.
Clin Immunol ; 174: 10-17, 2017 01.
Artigo em Inglês | MEDLINE | ID: mdl-27871892

RESUMO

Autoimmune diseases are characterized by chronic inflammatory reactions localized to an organ or organ-system. They are caused by loss of immunologic tolerance toward self-antigens, causing formation of autoantibodies that mistakenly attack their own body. Psoriasis is a chronic inflammatory autoimmune skin disease in which the underlying molecular mechanisms remain elusive. In this review, we present evidence accumulated through more than three decades that the serpin-derived protein Pso p27 is an autoantigen in psoriasis and probably also in other chronic inflammatory diseases. Pso p27 is derived from the serpin molecules SERPINB3 and SERPINB4 through non-canonical cleavage by mast cell chymase. In psoriasis, it is exclusively found in skin lesions and not in uninvolved skin. The serpins are cleaved into three fragments that remain associated as a Pso p27 complex with novel immunogenic properties and increased tendency to form large aggregates compared to native SERPINB3/B4. The amount of Pso p27 is directly correlated to disease activity, and through formation of complement activating immune-complexes, Pso p27 contribute to the inflammation in the skin lesions. SERPINB3/B4 are expressed in skin fibroblasts and keratinocytes, but normally absent in mast cells. Overexpression of the serpins may be induced by inflammation and hypoxia, resulting in mast cell uptake via yet unknown mechanisms. Here the generation and subsequent release of Pso p27 aggregates may promote an inflammatory loop that contributes to the chronicity of psoriasis and other autoimmune diseases.


Assuntos
Antígenos/imunologia , Autoantígenos/imunologia , Psoríase/imunologia , Antígenos de Neoplasias/imunologia , Humanos , Mastócitos/imunologia , Serpinas/imunologia
15.
Anal Biochem ; 523: 10-16, 2017 04 15.
Artigo em Inglês | MEDLINE | ID: mdl-28167071

RESUMO

The Multiplexed Inhibitor Bead (MIB) assay is a previously published quantitative proteomic MS-based approach to study cellular kinomes. A rather extensive procedure, need for multiple custom-made kinase inhibitors and an inability to re-use the MIB-columns, has limited its applicability. Here we present a modified MIB assay in which elution of bound proteins is facilitated by on-column trypsinization. We tested the modified MIB assay by analyzing extract from three human cancer cell lines treated with the cytotoxic drugs cisplatin or docetaxel. Using only three immobilized kinase inhibitors, we were able to detect about 6000 proteins, including ∼40% of the kinome, as well as other signaling, metabolic and structural proteins. The method is reproducible and the MIB-columns are re-usable without loss of performance. This makes the MIB assay a simple, affordable, and rapid assay for monitoring changes in cellular signaling.


Assuntos
Sobrevivência Celular/efeitos dos fármacos , Neoplasias/tratamento farmacológico , Inibidores de Proteínas Quinases/farmacologia , Proteínas Quinases/metabolismo , Proteômica/métodos , Tripsina/farmacologia , Bioensaio , Humanos , Espectrometria de Massas , Neoplasias/metabolismo , Neoplasias/patologia , Proteínas Quinases/química , Transdução de Sinais , Células Tumorais Cultivadas
16.
Biochim Biophys Acta ; 1854(1): 84-90, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-25448019

RESUMO

Transient transfection of mammalian cells with plasmid expression vectors and chemical transfection reagents is widely used to study protein transport and dynamics as well as phenotypic alterations mediated by the overexpressed protein. Despite the undisputed impact of this technique, surprisingly little is known about the cellular effects mediated by the transfection process per se. Conceivably, off-target effects could have implications upon proteins or processes being studied and understanding the molecular pathways affected would add value to the interpretation of experimental observations subsequent to cell transfection. Here we have used a SILAC-based proteomic approach to study differentially expressed proteins after transfection of HeLa cells with ECFP vector using a commonly employed non-liposome based transfection reagent, Fugene®HD. Whereas the transfection reagent itself mediated minimal effects upon protein expression, 11 proteins were found to be significantly upregulated after transfection, all of which were associated with an interferon type I/II response. The upregulated proteins might potentially inflict major cellular processes such as RNA splicing, chromatin remodeling, post-translational protein modification and cell cycle control. The results were validated by western analysis as well as quantitative RT-PCR and this demonstrated that an essentially identical response was induced in HeLa by transfection using an empty pUC18 vector, which does not contain a mammalian virus promoter, as well as a liposome-based transfection reagent, Lipofectamine(TM)2000. Notably, no induction of the interferon response was observed in HEK293 cells, suggesting that these cells might be preferable to HeLa to avoid undesired off-target effects in transfection studies encompassing interferon-signaling and antiviral responses.


Assuntos
Plasmídeos/genética , Proteoma/metabolismo , Proteômica/métodos , Transfecção/métodos , Western Blotting , Isótopos de Carbono/metabolismo , Cromatografia Líquida/métodos , Expressão Gênica , Células HEK293 , Células HeLa , Humanos , Marcação por Isótopo/métodos , Lipídeos/química , Lisina/metabolismo , Proteoma/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Espectrometria de Massas em Tandem/métodos
18.
Plant Physiol ; 167(2): 493-506, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25489022

RESUMO

The eukaryotic, highly conserved serine (Ser)/threonine-specific protein phosphatase 2A (PP2A) functions as a heterotrimeric complex composed of a catalytic (C), scaffolding (A), and regulatory (B) subunit. In Arabidopsis (Arabidopsis thaliana), five, three, and 17 genes encode different C, A, and B subunits, respectively. We previously found that a B subunit, B'θ, localized to peroxisomes due to its C-terminal targeting signal Ser-Ser-leucine. This work shows that PP2A C2, C5, andA2 subunits interact and colocalize with B'θ in peroxisomes. C and A subunits lack peroxisomal targeting signals, and their peroxisomal import depends on B'θ and appears to occur by piggybacking transport. B'θ knockout mutants were impaired in peroxisomal ß-oxidation as shown by developmental arrest of seedlings germinated without sucrose, accumulation of eicosenoic acid, and resistance to protoauxins indole-butyric acid and 2,4-dichlorophenoxybutyric acid. All of these observations strongly substantiate that a full PP2A complex is present in peroxisomes and positively affects ß-oxidation of fatty acids and protoauxins.


Assuntos
Arabidopsis/enzimologia , Holoenzimas/metabolismo , Peroxissomos/enzimologia , Proteína Fosfatase 2/metabolismo , Arabidopsis/efeitos dos fármacos , Domínio Catalítico , Sequência Conservada , Evolução Molecular , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Ácidos Indolacéticos/farmacologia , Metabolismo dos Lipídeos/efeitos dos fármacos , Modelos Biológicos , Mutação/genética , Oxirredução/efeitos dos fármacos , Peroxissomos/efeitos dos fármacos , Fenótipo , Fosforilação/efeitos dos fármacos , Plantas Geneticamente Modificadas , Ligação Proteica/efeitos dos fármacos , Subunidades Proteicas/metabolismo , Proteínas Recombinantes de Fusão/metabolismo , Plântula/efeitos dos fármacos , Plântula/metabolismo , Estresse Fisiológico/efeitos dos fármacos , Sacarose/farmacologia , Triglicerídeos/metabolismo
19.
Biochim Biophys Acta ; 1842(5): 734-8, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24560885

RESUMO

Psoriasis is a chronic inflammatory skin disease with unknown aetiology. Infiltration of inflammatory cells as the initial event in the development of new psoriatic plaques together with the defined inflamed areas of such lesions argues for an immunological disease with a local production of a causal antigen. The auto-antigen Pso p27 is a protein expressed in the skin lesions. We recently demonstrated that Pso p27 is homologous to the core amino acid sequences of squamous cell carcinoma antigens 1 and 2 (SCCA1/2) and it is apparently generated from SCCA molecules by digestion with highly specific endoproteases. In this communication we demonstrate the generation of Pso p27 from SCCA1 with extracts from psoriatic scale and even more remarkably, the generation of Pso p27 from SCCA1 in the presence of mast cell associated chymase. These findings open up for new therapeutic strategies in psoriasis and probably also in other autoimmune diseases as Pso p27 epitopes have been detected in diseased tissues from patients with various chronic inflammatory diseases.


Assuntos
Antígenos de Neoplasias/metabolismo , Antígenos/biossíntese , Quimases/metabolismo , Psoríase/etiologia , Serpinas/metabolismo , Antígenos/química , Eletroforese em Gel de Poliacrilamida , Humanos , Modelos Moleculares , Proteólise , Proteínas Recombinantes/metabolismo
20.
Basic Res Cardiol ; 110(4): 44, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26112154

RESUMO

Diabetes mellitus (DM) increases the risk of heart failure after myocardial infarction (MI), and aggravates ventricular arrhythmias in heart failure patients. Although exercise training improves cardiac function in heart failure, it is still unclear how it benefits the diabetic heart after MI. To study the effects of aerobic interval training on cardiac function, susceptibility to inducible ventricular arrhythmias and cardiomyocyte calcium handling in DM mice after MI (DM-MI). Male type 2 DM mice (C57BLKS/J Lepr (db) /Lepr (db) ) underwent MI or sham surgery. One group of DM-MI mice was submitted to aerobic interval training running sessions during 6 weeks. Cardiac function and structure were assessed by echocardiography and magnetic resonance imaging, respectively. Ventricular arrhythmias were induced by high-frequency cardiac pacing in vivo. Protein expression was measured by Western blot. DM-MI mice displayed increased susceptibility for inducible ventricular arrhythmias and impaired diastolic function when compared to wild type-MI, which was associated with disruption of cardiomyocyte calcium handling and increased calcium leak from the sarcoplasmic reticulum. High-intensity exercise recovered cardiomyocyte function in vitro, reduced sarcoplasmic reticulum diastolic calcium leak and significantly reduced the incidence of inducible ventricular arrhythmias in vivo in DM-MI mice. Exercise training also normalized the expression profile of key proteins involved in cardiomyocyte calcium handling, suggesting a potential molecular mechanism for the benefits of exercise in DM-MI mice. High-intensity aerobic exercise training recovers cardiomyocyte function and reduces inducible ventricular arrhythmias in infarcted diabetic mice.


Assuntos
Arritmias Cardíacas/prevenção & controle , Diabetes Mellitus Tipo 2/complicações , Infarto do Miocárdio/complicações , Condicionamento Físico Animal , Animais , Cálcio/metabolismo , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Contração Miocárdica , Canal de Liberação de Cálcio do Receptor de Rianodina/fisiologia , Retículo Sarcoplasmático/metabolismo , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/fisiologia , Função Ventricular Esquerda
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