RESUMO
Splicing modulation is a promising treatment strategy pursued to date only in splicing factor-mutant cancers; however, its therapeutic potential is poorly understood outside of this context. Like splicing factors, genes encoding components of the cohesin complex are frequently mutated in cancer, including myelodysplastic syndromes (MDS) and secondary acute myeloid leukemia (AML), where they are associated with poor outcomes. Here, we showed that cohesin mutations are biomarkers of sensitivity to drugs targeting the splicing factor 3B subunit 1 (SF3B1) H3B-8800 and E-7107. We identified drug-induced alterations in splicing, and corresponding reduced gene expression, of a number of DNA repair genes, including BRCA1 and BRCA2, as the mechanism underlying this sensitivity in cell line models, primary patient samples and patient-derived xenograft (PDX) models of AML. We found that DNA damage repair genes are particularly sensitive to exon skipping induced by SF3B1 modulators due to their long length and large number of exons per transcript. Furthermore, we demonstrated that treatment of cohesin-mutant cells with SF3B1 modulators not only resulted in impaired DNA damage response and accumulation of DNA damage, but it sensitized cells to subsequent killing by poly(ADP-ribose) polymerase (PARP) inhibitors and chemotherapy and led to improved overall survival of PDX models of cohesin-mutant AML in vivo. Our findings expand the potential therapeutic benefits of SF3B1 splicing modulators to include cohesin-mutant MDS and AML.
Assuntos
Leucemia Mieloide Aguda , Síndromes Mielodisplásicas , Humanos , Coesinas , Síndromes Mielodisplásicas/tratamento farmacológico , Síndromes Mielodisplásicas/genética , Síndromes Mielodisplásicas/metabolismo , Splicing de RNA , Fatores de Processamento de RNA/genética , Mutação/genética , Fatores de Transcrição/metabolismo , Leucemia Mieloide Aguda/tratamento farmacológico , Leucemia Mieloide Aguda/genética , Reparo do DNA/genética , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Dano ao DNARESUMO
Somatic UBA1 mutations in hematopoietic cells are a hallmark of Vacuoles, E1 enzyme, X-linked, Autoinflammatory, Somatic (VEXAS) syndrome, which is a late-onset inflammatory disease associated with bone marrow failure and high mortality. The majority of UBA1 mutations in VEXAS syndrome comprise hemizygous mutations affecting methionine-41 (M41), leading to the expression of UBA1M41T, UBA1M41V, or UBA1M41L and globally reduced protein polyubiquitination. Here, we used CRISPR-Cas9 to engineer isogenic 32D mouse myeloid cell lines expressing hemizygous Uba1WT or Uba1M41L from the endogenous locus. Consistent with prior analyses of patients with VEXAS syndrome samples, hemizygous Uba1M41L expression was associated with loss of the UBA1b protein isoform, gain of the UBA1c protein isoform, reduced polyubiquitination, abnormal cytoplasmic vacuoles, and increased production of interleukin-1ß and inflammatory chemokines. Vacuoles in Uba1M41L cells contained a variety of endolysosomal membranes, including small vesicles, multivesicular bodies, and multilamellar lysosomes. Uba1M41L cells were more sensitive to the UBA1 inhibitor TAK243. TAK243 treatment promoted apoptosis in Uba1M41L cells and led to preferential loss of Uba1M41L cells in competition assays with Uba1WT cells. Knock-in of a TAK243-binding mutation, Uba1A580S, conferred TAK243 resistance. In addition, overexpression of catalytically active UBA1b in Uba1M41L cells restored polyubiquitination and increased TAK243 resistance. Altogether, these data indicate that loss of UBA1b underlies a key biochemical phenotype associated with VEXAS syndrome and renders cells with reduced UBA1 activity vulnerable to targeted UBA1 inhibition. Our Uba1M41L knock-in cell line is a useful model of VEXAS syndrome that will aid in the study of disease pathogenesis and the development of effective therapies.
Assuntos
Células Mieloides , Células Progenitoras Mieloides , Animais , Camundongos , Humanos , Lisossomos , Isoformas de ProteínasRESUMO
Nuclear hormone receptors (NRs) are ligand-binding transcription factors that are widely targeted therapeutically. Agonist binding triggers NR activation and subsequent degradation by unknown ligand-dependent ubiquitin ligase machinery. NR degradation is critical for therapeutic efficacy in malignancies that are driven by retinoic acid and estrogen receptors. Here, we demonstrate the ubiquitin ligase UBR5 drives degradation of multiple agonist-bound NRs, including the retinoic acid receptor alpha (RARA), retinoid x receptor alpha (RXRA), glucocorticoid, estrogen, liver-X, progesterone, and vitamin D receptors. We present the high-resolution cryo-EMstructure of full-length human UBR5 and a negative stain model representing its interaction with RARA/RXRA. Agonist ligands induce sequential, mutually exclusive recruitment of nuclear coactivators (NCOAs) and UBR5 to chromatin to regulate transcriptional networks. Other pharmacological ligands such as selective estrogen receptor degraders (SERDs) degrade their receptors through differential recruitment of UBR5 or RNF111. We establish the UBR5 transcriptional regulatory hub as a common mediator and regulator of NR-induced transcription.
Assuntos
Cromatina , Fatores de Transcrição , Humanos , Ligantes , Cromatina/genética , Fatores de Transcrição/metabolismo , Receptores Citoplasmáticos e Nucleares/genética , Ubiquitinas , Ubiquitina-Proteína Ligases/genéticaRESUMO
The IL-3, IL-5, and GM-CSF family of cytokines play an essential role in the growth, differentiation, and effector functions of multiple hematopoietic cell types. Receptors in this family are composed of cytokine-specific α chains and a common ß chain (CSF2RB), responsible for the majority of downstream signaling. CSF2RB abundance and stability influence the magnitude of the cellular response to cytokine stimulation, but the exact mechanisms of regulation are not well understood. Here, we use genetic screens in multiple cellular contexts and cytokine conditions to identify STUB1, an E3 ubiquitin ligase, and CHIC2 as regulators of CSF2RB ubiquitination and protein stability. We demonstrate that Stub1 and Chic2 form a complex that binds Csf2rb and that genetic inactivation of either Stub1 or Chic2 leads to reduced ubiquitination of Csf2rb. The effects of Stub1 and Chic2 on Csf2rb were greatest at reduced cytokine concentrations, suggesting that Stub1/Chic2-mediated regulation of Csf2rb is a mechanism of reducing cell surface accumulation when cytokine levels are low. Our study uncovers a mechanism of CSF2RB regulation through ubiquitination and lysosomal degradation and describes a role for CHIC2 in the regulation of a cytokine receptor.
Assuntos
Subunidade beta Comum dos Receptores de Citocinas , Ubiquitina-Proteína Ligases , Subunidade beta Comum dos Receptores de Citocinas/genética , Fator Estimulador de Colônias de Granulócitos e Macrófagos/genética , Interleucina-3/genética , Interleucina-3/metabolismo , Interleucina-5/genética , Interleucina-5/metabolismo , Estabilidade Proteica , Ubiquitina-Proteína Ligases/genética , Ubiquitina-Proteína Ligases/metabolismo , UbiquitinaçãoRESUMO
Bleeding in patients with acute myeloid leukemia (AML) receiving intensive induction chemotherapy is multifactorial and contributes to early death. We sought to define the incidence and risk factors of grade 4 bleeding to support strategies for risk mitigation. Bleeding events were retrospectively assessed between day-14 and day +60 of induction treatment according to the World Health Organization (WHO) bleeding assessment scale, which includes grade 4 bleeding as fatal, life-threatening, retinal with visual impairment, or involving the central nervous system. Predictors were considered pretreatment or prior to grade 4 bleeding. Using multivariable competing-risk regression analysis with grade 4 bleeding as the primary outcome, we identified risk factors in the development cohort (n = 341), which were tested in an independent cohort (n = 143). Grade 4 bleeding occurred in 5.9% and 9.8% of patients in the development and validation cohort, respectively. Risk factors that were independently associated with grade 4 bleeding included baseline platelet count ≤40 × 109/L compared with >40 × 109/L, and baseline international normalized ratio of prothrombin time (PT-INR) >1.5 or 1.3 > 1.5 compared with ≤1.3. These variables were allocated points, which allowed for stratification of patients with low- and high-risk for grade 4 bleeding. Cumulative incidence of grade 4 bleeding at day+60 was significantly higher among patients with high- vs low-risk (development: 31 ± 7% vs 2 ± 1%; P < .001; validation: 25 ± 9% vs 7 ± 2%; P = .008). In both cohorts, high bleeding risk was associated with disseminated intravascular coagulation (DIC) and proliferative disease. We developed and validated a simple risk model for grade 4 bleeding, which enables the development of rational risk mitigation strategies to improve early mortality of intensive induction treatment.
Assuntos
Coagulação Intravascular Disseminada , Leucemia Mieloide Aguda , Hemorragia/epidemiologia , Hemorragia/etiologia , Humanos , Quimioterapia de Indução/efeitos adversos , Leucemia Mieloide Aguda/complicações , Leucemia Mieloide Aguda/tratamento farmacológico , Estudos RetrospectivosRESUMO
Casitas B-lineage lymphoma (CBL) encodes an E3 ubiquitin ligase and signaling adaptor that regulates receptor and nonreceptor tyrosine kinases. Recurrent CBL mutations occur in myeloid neoplasms, including 10% to 20% of chronic myelomonocytic leukemia (CMML) cases, and selectively disrupt the protein's E3 ubiquitin ligase activity. CBL mutations have been associated with poor prognosis, but the oncogenic mechanisms and therapeutic implications of CBL mutations remain incompletely understood. We combined functional assays and global mass spectrometry to define the phosphoproteome, CBL interactome, and mechanism of signaling activation in a panel of cell lines expressing an allelic series of CBL mutations. Our analyses revealed that increased LYN activation and interaction with mutant CBL are key drivers of enhanced CBL phosphorylation, phosphoinositide-3-kinase regulatory subunit 1 (PIK3R1) recruitment, and downstream phosphatidylinositol 3-kinase (PI3K)/AKT signaling in CBL-mutant cells. Signaling adaptor domains of CBL, including the tyrosine kinase-binding domain, proline-rich region, and C-terminal phosphotyrosine sites, were all required for the oncogenic function of CBL mutants. Genetic ablation or dasatinib-mediated inhibition of LYN reduced CBL phosphorylation, CBL-PIK3R1 interaction, and PI3K/AKT signaling. Furthermore, we demonstrated in vitro and in vivo antiproliferative efficacy of dasatinib in CBL-mutant cell lines and primary CMML. Overall, these mechanistic insights into the molecular function of CBL mutations provide rationale to explore the therapeutic potential of LYN inhibition in CBL-mutant myeloid malignancies.
Assuntos
Classe Ia de Fosfatidilinositol 3-Quinase/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Proteínas Proto-Oncogênicas c-cbl/genética , Quinases da Família src/metabolismo , Neoplasias Hematológicas/genética , Neoplasias Hematológicas/metabolismo , Humanos , Mutação , Mapas de Interação de Proteínas , Proteínas Proto-Oncogênicas c-cbl/metabolismo , Transdução de SinaisRESUMO
Chronic graft-versus-host disease (cGVHD) affects >50% of hematopoietic stem cell transplant patients. Extracorporeal photopheresis (ECP), an immunomodulatory therapy, provides clinical benefit in steroid-refractory (SR) cGVHD, possibly via regulatory T (Treg) and natural killer (NK) cell expansion. We demonstrated that low-dose interleukin-2 (IL2) led to clinical improvement in SR-cGVHD and stimulated preferential Treg and NK-cell expansion with minimal effect on conventional T (Tcon) cells. We evaluated the effect of ECP (weeks 1-16) plus IL2 (1 × 106 IU/m2, weeks 9-16) in 25 adult patients with SR-cGVHD in a prospective phase 2 trial. Objective responses occurred in 29% and 62% of evaluable patients at weeks 8 (ECP alone) and 16 (ECP plus IL2), respectively. Eight weeks of ECP alone was associated with a marked decline in CD4+ Tcon (P = .03) and CD8+ T cells (P = .0002), with minimal change in Treg cells, Treg:Tcon cell ratio, or NK cells. Adding IL2 induced an increase in Treg cells (P < .05 at weeks 9-16 vs week 8), Treg:Tcon cell ratio (P < .0001 at weeks 9-16 vs week 8), and NK cells (P < .05 at weeks 9-16 vs week 8). Patients responding to ECP alone had significantly fewer CD4+ Tcon and CD8+ T cells at baseline compared with patients who responded after IL2 addition and patients who did not respond; neither Treg nor NK cells were associated with response to ECP alone. Altogether, ECP plus IL2 is safe and effective in patients with SR-cGVHD. ECP and IL2 have distinct immunologic effects, suggesting different therapeutic mechanisms of action. This trial was registered at www.clinicaltrials.gov as #NCT02340676.
Assuntos
Terapia Combinada/métodos , Doença Enxerto-Hospedeiro/terapia , Interleucina-2/uso terapêutico , Fotoferese/métodos , Adulto , Idoso , Linfócitos T CD4-Positivos , Linfócitos T CD8-Positivos , Proliferação de Células/efeitos dos fármacos , Proliferação de Células/efeitos da radiação , Doença Crônica , Feminino , Humanos , Interleucina-2/imunologia , Células Matadoras Naturais/citologia , Masculino , Pessoa de Meia-Idade , Linfócitos T Reguladores/citologia , Fatores de Tempo , Resultado do TratamentoRESUMO
Hematologic malignancies are driven by combinations of genetic lesions that have been difficult to model in human cells. We used CRISPR/Cas9 genome engineering of primary adult and umbilical cord blood CD34+ human hematopoietic stem and progenitor cells (HSPCs), the cells of origin for myeloid pre-malignant and malignant diseases, followed by transplantation into immunodeficient mice to generate genetic models of clonal hematopoiesis and neoplasia. Human hematopoietic cells bearing mutations in combinations of genes, including cohesin complex genes, observed in myeloid malignancies generated immunophenotypically defined neoplastic clones capable of long-term, multi-lineage reconstitution and serial transplantation. Employing these models to investigate therapeutic efficacy, we found that TET2 and cohesin-mutated hematopoietic cells were sensitive to azacitidine treatment. These findings demonstrate the potential for generating genetically defined models of human myeloid diseases, and they are suitable for examining the biological consequences of somatic mutations and the testing of therapeutic agents.
Assuntos
Sistemas CRISPR-Cas/genética , Edição de Genes , Genoma Humano , Hematopoese , Células-Tronco Hematopoéticas/metabolismo , Modelos Biológicos , Transtornos Mieloproliferativos/genética , Transtornos Mieloproliferativos/patologia , Animais , Antígenos CD34/metabolismo , Linhagem da Célula , Células Clonais , Genótipo , Transplante de Células-Tronco Hematopoéticas , Humanos , Leucemia/patologia , Camundongos , Mutação/genética , Zigoto/metabolismoRESUMO
BACKGROUND: Collection of hematopoietic progenitor cells by apheresis (HPC-A) requires separation of cells by density. Previous studies highlighted the challenges of HPC-A collection from patients with abnormal red blood cells (RBCs). TEMPI syndrome is a recently described condition defined by teleangiectasias, elevated erythropoietin and erythrocytosis, monoclonal gammopathy, perinephric fluid collections, and intrapulmonary shunting. Patients with TEMPI syndrome have responded to therapies used to treat plasma cell dyscrasias and may benefit from autologous HPC transplantation. We report HPC-A collection from a patient with TEMPI syndrome that was complicated by severe iron deficiency. STUDY DESIGN AND METHODS: The patient received granulocyte-colony-stimulating factor (G-CSF) and plerixafor for HPC mobilization and underwent 3 days of HPC-A collection. RESULTS: The patient presented for collection with a microcytic erythrocytosis. Over 3 days, approximately 50 L of whole blood was processed, and 2 × 10(8) CD34+ cells were collected (2.8 × 10(6) CD34+ cells/kg). The mean collection efficiency (CE), percentage of mononuclear cells, hematocrit (Hct), and RBC count were 18%, 90%, 14%, and 9 × 10(11) , respectively. Altering collection variables to avoid RBC contamination reduced CE. Ficoll preparations of the products after freeze-thaw showed RBC contamination and hemolysis. Postthaw viability exceeded 95%. The products were not RBC reduced or washed. There were no adverse reactions during or after infusion. CONCLUSIONS: HPC-A collection from a patient with TEMPI syndrome was complicated by microcytic erythrocytosis, leading to RBC contamination and hemolysis in the product. Adequate HPCs were collected and the patient tolerated infusion without RBC depletion or washing. Our report highlights difficulties of HPC-A collection from iron-deficient patients.
Assuntos
Citaferese , Eritrócitos Anormais , Eritropoetina/sangue , Mobilização de Células-Tronco Hematopoéticas , Células-Tronco Hematopoéticas , Nefropatias/sangue , Paraproteinemias/sangue , Policitemia/sangue , Benzilaminas , Ciclamos , Fator Estimulador de Colônias de Granulócitos/administração & dosagem , Compostos Heterocíclicos/administração & dosagem , Humanos , Contagem de Leucócitos , Masculino , Pessoa de Meia-Idade , SíndromeRESUMO
Genome sequencing studies have shown that human malignancies often bear mutations in four or more driver genes, but it is difficult to recapitulate this degree of genetic complexity in mouse models using conventional breeding. Here we use the CRISPR-Cas9 system of genome editing to overcome this limitation. By delivering combinations of small guide RNAs (sgRNAs) and Cas9 with a lentiviral vector, we modified up to five genes in a single mouse hematopoietic stem cell (HSC), leading to clonal outgrowth and myeloid malignancy. We thereby generated models of acute myeloid leukemia (AML) with cooperating mutations in genes encoding epigenetic modifiers, transcription factors and mediators of cytokine signaling, recapitulating the combinations of mutations observed in patients. Our results suggest that lentivirus-delivered sgRNA:Cas9 genome editing should be useful to engineer a broad array of in vivo cancer models that better reflect the complexity of human disease.
Assuntos
Neoplasias da Medula Óssea/genética , Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas/genética , Animais , Modelos Animais de Doenças , CamundongosRESUMO
Immature dendritic cells (DCs) specialize in antigen capture and maintain a highly dynamic pool of intracellular major histocompatibility complex class II (MHCII) that continuously recycles from peptide loading compartments to the plasma membrane and back again. This process facilitates sampling of environmental antigens for presentation to T helper cells. Here, we show that a signaling pathway mediated by the DC immunoreceptor tyrosine-based activation motif (ITAM)-containing adaptors (DAP12 and FcRγ) and Vav family guanine nucleotide exchange factors controls the half-life of surface peptide-MHCII (pMHCII) complexes and is critical for CD4 T-cell triggering in vitro. Strikingly, mice with disrupted DC ITAMs show defective T helper cell priming in vivo and are protected from experimental autoimmune encephalitis. Mechanistically, we show that deficiency in ITAM signaling results in increased pMHCII internalization, impaired recycling, and an accumulation of ubiquitinated MHCII species that are prematurely degraded in lysosomes. We propose a novel mechanism for control of T helper cell priming.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/imunologia , Células Dendríticas/imunologia , Antígenos de Histocompatibilidade Classe II/imunologia , Proteínas Proto-Oncogênicas c-vav/imunologia , Receptores de IgG/imunologia , Linfócitos T Auxiliares-Indutores/imunologia , Motivos de Aminoácidos , Animais , Apresentação de Antígeno , Encefalopatias/induzido quimicamente , Encefalopatias/imunologia , Linfócitos T CD4-Positivos/imunologia , Encefalite , Doença de Hashimoto/induzido quimicamente , Doença de Hashimoto/imunologia , Antígenos de Histocompatibilidade Classe II/metabolismo , Lisossomos/metabolismo , Camundongos , Transdução de Sinais , Tirosina/imunologia , UbiquitinaçãoRESUMO
Peptides derived from exogenous proteins are presented by both MHC class I and II. Despite extensive study, the features of the endocytic pathway that mediate cross-presentation of exogenous antigens on MHC class I are not entirely understood and difficult to generalize to all proteins. Here, we used dendritic cells and macrophages to examine MHC class I and II presentation of hen egg-white lysozyme (HEL) in different forms, soluble and liposome encapsulated. Soluble HEL or HEL targeted to a late endosomal compartment only allowed for MHC class II presentation, in a process that was blocked by chloroquine and a cathepsin S (CatS) inhibitor; brefeldin A (BFA) also blocked presentation, indicating a requirement for nascent MHC class II. In contrast, liposome-encapsulated HEL targeted to early endosomes entered the MHC class I and II presentation pathways. Cross-presentation of HEL in early endosomal liposomes had several unique features: it was markedly increased by BFA and by blockade of the proteasome or CatS activity, it occurred independently of the transporter associated with antigen processing but required an MHC class I surface-stabilizing peptide, and it was inhibited by chloroquine. Remarkably, chloroquine facilitated MHC class I cross-presentation of soluble HEL and HEL in late endosomal liposomes. Altogether, MHC class I and II presentation of HEL occurred through pathways having distinct molecular and proteolytic requirements. Moreover, MHC class I sampled antigenic peptides from various points along the endocytic route.
Assuntos
Antígenos de Histocompatibilidade Classe II/genética , Antígenos de Histocompatibilidade Classe I/genética , Animais , Brefeldina A/farmacologia , Galinhas , Cloroquina/farmacologia , Células Dendríticas/imunologia , Endocitose/imunologia , Antígenos de Histocompatibilidade Classe I/efeitos dos fármacos , Antígenos de Histocompatibilidade Classe II/efeitos dos fármacos , Humanos , Lipossomos/química , Macrófagos/imunologia , Camundongos , Camundongos Endogâmicos NOD/imunologia , Muramidase/química , Muramidase/genéticaRESUMO
Parkinson's disease (PD) is characterized pathologically by preferential degeneration of the dopaminergic neurons in the substantia nigra pars compacta (SNc). Nigral cell death is accompanied by the accumulation of a wide range of poorly degraded proteins and the formation of proteinaceous inclusions (Lewy bodies) in dopaminergic neurons. Mutations in the genes encoding alpha-synuclein and two enzymes of the ubiquitin-proteasome system, parkin and ubiquitin C-terminal hydrolase L1, are associated with neurodegeneration in some familial forms of PD. We now show that, in comparison to age-matched controls, alpha-subunits (but not beta-subunits) of 26/20S proteasomes are lost within dopaminergic neurons and 20S proteasomal enzymatic activities are impaired in the SNc in sporadic PD. In addition, while the levels of the PA700 proteasome activator are reduced in the SNc in PD, PA700 expression is increased in other brain regions such as the frontal cortex and striatum. We also found that levels of the PA28 proteasome activator are very low to almost undetectable in the SNc compared to other brain areas in both normal and PD subjects. These findings suggest that failure of the ubiquitin-proteasome system to adequately clear unwanted proteins may underlie vulnerability and degeneration of the SNc in both sporadic and familial PD.
Assuntos
Encéfalo/enzimologia , Cisteína Endopeptidases/metabolismo , Complexos Multienzimáticos/metabolismo , Doença de Parkinson/enzimologia , Peptídeo Hidrolases/metabolismo , Idoso , Encéfalo/patologia , Cisteína Endopeptidases/deficiência , Dopamina/biossíntese , Ativação Enzimática , Feminino , Humanos , Masculino , Complexos Multienzimáticos/deficiência , Neurônios/enzimologia , Neurônios/patologia , Especificidade de Órgãos , Doença de Parkinson/patologia , Peptídeo Hidrolases/deficiência , Complexo de Endopeptidases do Proteassoma , Subunidades Proteicas/deficiência , Subunidades Proteicas/metabolismo , Substância Negra/metabolismo , Substância Negra/patologiaRESUMO
Structural and functional defects in 26/20S proteasomes occur in the substantia nigra pars compacta and may underlie protein accumulation, Lewy body formation and dopaminergic neuronal death in Parkinson's disease. We therefore determined the pathogenicity of proteasomal impairment following stereotaxic unilateral infusion of lactacystin, a selective proteasome inhibitor, into the substantia nigra pars compacta of rats. These animals became progressively bradykinetic, adopted a stooped posture and displayed contralateral head tilting. Administration of apomorphine to lactacystin-treated rats reversed behavioral abnormalities and induced contralateral rotations. Lactacystin caused dose-dependent degeneration of dopaminergic cell bodies and processes with the cytoplasmic accumulation and aggregation of alpha-synuclein to form inclusion bodies. These findings support the notion that failure of the ubiquitin-proteasome system to degrade and clear unwanted proteins is an important etiopathogenic factor in Parkinson's disease.
Assuntos
Acetilcisteína/análogos & derivados , Corpos de Inclusão/patologia , Complexos Multienzimáticos/antagonistas & inibidores , Degeneração Estriatonigral/patologia , Substância Negra/patologia , Acetilcisteína/farmacologia , Animais , Cisteína Endopeptidases/metabolismo , Dopamina/metabolismo , Relação Dose-Resposta a Droga , Corpos de Inclusão/efeitos dos fármacos , Corpos de Inclusão/enzimologia , Complexos Multienzimáticos/metabolismo , Neurônios/efeitos dos fármacos , Neurônios/patologia , Doença de Parkinson/patologia , Doença de Parkinson Secundária/induzido quimicamente , Complexo de Endopeptidases do Proteassoma , Ratos , Ratos Sprague-Dawley , Degeneração Estriatonigral/induzido quimicamente , Degeneração Estriatonigral/enzimologia , Substância Negra/efeitos dos fármacos , Substância Negra/enzimologiaRESUMO
The proteolytic activities of 26/20S proteasomes are impaired in the substantia nigra pars compacta (SNc) in sporadic Parkinson's disease (PD). In the present study, we examined the structural integrity of the proteasome by determining the levels of the beta- and alpha-subunits which together normally constitute the catalytic core of 26/20S proteasomes. Western blot analyzes and immunohistochemical staining revealed a major and selective loss of alpha-subunits in dopaminergic neurons of the SNc but not in other brain regions in sporadic PD. This defect is known to cause the proteasome to become unstable and prevents its assembly with resultant impairment of enzymatic activity. Thus, structural and function defects in 26/20S proteasomes may underlie protein accumulation, formation of proteinaceous Lewy bodies and dopaminergic neuronal death in the SNc in sporadic PD.