Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 5 de 5
Filtrar
Mais filtros

Base de dados
Tipo de documento
Intervalo de ano de publicação
1.
J Biol Chem ; 288(32): 23447-56, 2013 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-23779105

RESUMO

para-Aminosalicylic acid (PAS) is one of the antimycobacterial drugs currently used for multidrug-resistant tuberculosis. Although it has been in clinical use for over 60 years, its mechanism(s) of action remains elusive. Here we report that PAS is a prodrug targeting dihydrofolate reductase (DHFR) through an unusual and novel mechanism of action. We provide evidences that PAS is incorporated into the folate pathway by dihydropteroate synthase (DHPS) and dihydrofolate synthase (DHFS) to generate a hydroxyl dihydrofolate antimetabolite, which in turn inhibits DHFR enzymatic activity. Interestingly, PAS is recognized by DHPS as efficiently as its natural substrate para-amino benzoic acid. Chemical inhibition of DHPS or mutation in DHFS prevents the formation of the antimetabolite, thereby conferring resistance to PAS. In addition, we identified a bifunctional enzyme (riboflavin biosynthesis protein (RibD)), a putative functional analog of DHFR in a knock-out strain. This finding is further supported by the identification of PAS-resistant clinical isolates encoding a RibD overexpression mutation displaying cross-resistance to genuine DHFR inhibitors. Our findings reveal that a metabolite of PAS inhibits DHFR in the folate pathway. RibD was shown to act as a functional analog of DHFR, and as for DHFS, both were shown to be associated in PAS resistance in laboratory strains and clinical isolates.


Assuntos
Ácido Aminossalicílico , Antituberculosos , Proteínas de Bactérias/antagonistas & inibidores , Proteínas de Bactérias/metabolismo , Antagonistas do Ácido Fólico , Pró-Fármacos , Tetra-Hidrofolato Desidrogenase/metabolismo , Ácido Aminossalicílico/farmacocinética , Ácido Aminossalicílico/farmacologia , Antituberculosos/farmacocinética , Antituberculosos/farmacologia , Proteínas de Bactérias/genética , Di-Hidropteroato Sintase/antagonistas & inibidores , Di-Hidropteroato Sintase/genética , Di-Hidropteroato Sintase/metabolismo , Antagonistas do Ácido Fólico/farmacocinética , Antagonistas do Ácido Fólico/farmacologia , Técnicas de Silenciamento de Genes , Mutação , Pró-Fármacos/farmacocinética , Pró-Fármacos/farmacologia , Tetra-Hidrofolato Desidrogenase/genética
2.
J Immune Based Ther Vaccines ; 6: 2, 2008 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-18439316

RESUMO

BACKGROUND: As the eradication of tumor cells in vivo is most efficiently performed by cytolytic T lymphocytes (CTL), various methods for priming tumor-reactive lymphocytes have been developed. In this study, a method of priming CTLs with ultraviolet (UV)-irradiated tumor cells, which results in termination of tumor cell proliferation, apoptosis, as well as upregulation of heat shock proteins (HSP) expression is described. METHODS: Peripheral blood mononuclear cells (PBMC) were primed weekly with UV-irradiated or mitomycin-treated RPMI 8226 multiple myeloma cells. Following three rounds of stimulation over 21 days, the lymphocytes from the mixed culture conditions were analyzed for anti-MM cell reactivity. RESULTS: By day 10 of cultures, PBMCs primed using UV-irradiated tumor cells demonstrated a higher percentage of activated CD8+/CD4- T lymphocytes than non-primed PBMCs or PBMCs primed using mitomycin-treated MM cells. Cytotoxicity assays revealed that primed PBMCs were markedly more effective (p < 0.01) than non-primed PBMCs in killing RPMI 8226 MM cells. Surface expression of glucose regulated protein 94 (Grp94/Gp96) and Grp78 were both found to be induced in UV-treated MM cells. CONCLUSION: Since, HSP-associated peptides are known to mediate tumor rejection; these data suggest that immune-mediated eradication of MM cells could be elicited via a UV-induced HSP process. The finding that the addition of 17-allylamide-17-demethoxygeldanamycin (17AAG, an inhibitor of HSP 90-peptide interactions) resulted in decreased CTL-induced cytotoxicity supported this hypothesis. Our study, therefore, provides the framework for the development of anti-tumor CTL cellular vaccines for treating MM using UV-irradiated tumor cells as immunogens.

3.
Biochim Biophys Acta ; 1765(2): 223-34, 2006 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-16480833

RESUMO

Ku is a heterodimeric protein made up of two subunits, Ku70 and Ku80. It was originally identified as an autoantigen recognized by the sera of patients with autoimmune diseases. It is a highly versatile regulatory protein that has been implicated in multiple nuclear processes, e.g., DNA repair, telomere maintenance and apoptosis. Accordingly, Ku is thought to play a crucial role in maintenance of chromosomal integrity and cell survival. Recent reports suggest that there is a positive relationship between Ku and the development of cancer, making Ku an important candidate target for anticancer drug development. Specifically, prior studies suggest that a delicate balance exists in Ku expression, as overexpression of Ku proteins promotes oncogenic phenotypes, including hyperproliferation and resistance to apoptosis; whereas deficient or low expression of Ku leads to genomic instability and tumorigenesis. Such observations through various experimental models indicate that Ku may act as either a tumor suppressor or an oncoprotein. Hence, understanding the link between the various functions of Ku and the development of cancer in different cell systems may help in the development of novel anticancer therapeutic agents that target Ku. These studies may also increase our understanding of how Ku autoantibodies are generated in autoimmune diseases.


Assuntos
Antígenos Nucleares/fisiologia , Proteínas de Ligação a DNA/fisiologia , Neoplasias/metabolismo , Animais , Transformação Celular Neoplásica , Humanos , Autoantígeno Ku , Neoplasias/patologia
5.
Nat Commun ; 1: 57, 2010 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-20975714

RESUMO

Candidate antibacterials are usually identified on the basis of their in vitro activity. However, the apparent inhibitory activity of new leads can be misleading because most culture media do not reproduce an environment relevant to infection in vivo. In this study, while screening for novel anti-tuberculars, we uncovered how carbon metabolism can affect antimicrobial activity. Novel pyrimidine-imidazoles (PIs) were identified in a whole-cell screen against Mycobacterium tuberculosis. Lead optimization generated in vitro potent derivatives with desirable pharmacokinetic properties, yet without in vivo efficacy. Mechanism of action studies linked the PI activity to glycerol metabolism, which is not relevant for M. tuberculosis during infection. PIs induced self-poisoning of M. tuberculosis by promoting the accumulation of glycerol phosphate and rapid ATP depletion. This study underlines the importance of understanding central bacterial metabolism in vivo and of developing predictive in vitro culture conditions as a prerequisite for the rational discovery of new antibiotics.


Assuntos
Mycobacterium tuberculosis/efeitos dos fármacos , Mycobacterium tuberculosis/metabolismo , Trifosfato de Adenosina/metabolismo , Antituberculosos/farmacologia , Glicerofosfatos/metabolismo , Imidazóis/farmacologia , Modelos Biológicos
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA