RESUMO
REST/NRSF is a transcriptional repressor of neuronal genes that has been implicated in development and cancer. In epithelial tissues, REST acts as a tumor suppressor and in breast cancer, loss of REST is associated with disease recurrence and poor prognosis. Here, we identify TSPYL2 (also known as CDA1 and DENTT) as a novel component of the REST protein complex. We show that REST and TSPYL2 are regulators of TGFß signaling and that cell-cycle arrest induced by TGFß requires both REST and TSPYL2. Importantly, knockdown of REST or TSPYL2 resulted in transformation of human mammary epithelial cells. Mechanistically, we demonstrate that the TSPYL2/REST complex promotes TGFß signaling by repressing the expression of genes, such as the proto-oncogene neurotrophic tyrosine kinase receptor C (TrkC). These data provide insight into the role of REST as a tumor suppressor in epithelial tissues through the regulation of the TGFß pathway.
Assuntos
Proteínas Nucleares/metabolismo , Proteínas Repressoras/fisiologia , Fator de Crescimento Transformador beta/farmacologia , Western Blotting , Linhagem Celular Tumoral , Imunoprecipitação da Cromatina , Proteínas de Ligação a DNA , Humanos , Espectrometria de Massas , Proteínas Nucleares/genética , Proto-Oncogene Mas , Proteínas Repressoras/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transdução de Sinais/efeitos dos fármacosRESUMO
There are two major physiological androgens, testosterone (T), and 5alpha-dihydrotestosterone (DHT), which induce different responses in mammals. These androgens regulate the target gene transcription via binding to and activating the same androgen receptor (AR). The molecular mechanisms that differ between these two very close androgens through the same AR protein to target the distinct genomic responses remain unknown. Using yeast genetic selection, we identified two kinds of androgen response elements (ARE), which could respond differentially to T vs. DHT. These two AREs also show different T- vs. DHT-induced AR transactivation in mammalian Chinese hamster ovary (CHO) cells in terms of copy number and comparisons with the classic mouse mammary tumor virus ARE. Together, our results suggest that the selective ARE sequence may play an important role in the differential T- vs. DHT-induced AR transactivation.
Assuntos
Di-Hidrotestosterona/metabolismo , Regulação da Expressão Gênica , Genes Reguladores/genética , Receptores Androgênicos/metabolismo , Testosterona/metabolismo , Animais , Sequência de Bases , Células CHO/metabolismo , Células Cultivadas , Cloranfenicol O-Acetiltransferase/biossíntese , Cricetinae , Primers do DNA/química , Biblioteca Gênica , Vetores Genéticos , Luciferases/biossíntese , Dados de Sequência Molecular , Plasmídeos , Saccharomyces/genética , Saccharomyces/metabolismo , Testosterona/genética , TransfecçãoRESUMO
The androgen receptor (AR) binds to androgen response elements and regulates target genes via a mechanism involving coregulators. Here we demonstrate that the AR can interact with the testicular orphan receptor-4 (TR4) and function as a repressor to down-regulate the TR4 target genes by preventing the TR4 binding to its target DNA. Interestingly, the heterodimerization of AR and TR4 also allows TR4 to repress AR target gene expression. Simultaneous exposure to both receptors therefore could result in bidirectional suppression of their target genes. Together, these data demonstrate that the coupling of two different receptors, through the heterodimerization of AR and TR4, is a unique signaling pathway in the steroid receptor superfamily, which may facilitate further understanding of the complicated androgen action in prostate cancer or libido.
Assuntos
Regulação da Expressão Gênica , Proteínas do Tecido Nervoso/metabolismo , Receptores Androgênicos/metabolismo , Receptores de Esteroides/metabolismo , Receptores dos Hormônios Tireóideos , Proteínas Repressoras/metabolismo , Dimerização , Humanos , Masculino , Proteínas do Tecido Nervoso/genética , Ligação Proteica , Receptores Androgênicos/genética , Receptores de Esteroides/genética , Proteínas Recombinantes/metabolismo , Proteínas Repressoras/genética , Elementos de Resposta , Transdução de Sinais , Ativação Transcricional , Técnicas do Sistema de Duplo-HíbridoRESUMO
Several new androgen receptor (AR) cofactors, associated to the ligand binding domain of AR, have been identified by our group and named AR associated protein (ARA)70, ARA55, and ARA54. Our previous reports have suggested that the cofactor ARA70 can confer the androgenic effect from 17 beta-estradiol (E2) and antiandrogen to AR. It is of interest for us to compare and determine if the specificity of sex hormones and antiandrogens could be modulated by different coactivators. Our results indicate that ARA70 is the best coactivator to confer the androgenic activity on E2. Only ARA70 and ARA55 could increase significantly the androgenic activity of hydroxyflutamide, a widely used antiandrogen for the treatment of prostate cancer. Furthermore, as compared to the relative specificity of these coactivators to AR in the prostate cancer DU145 cells, our results suggest that ARA70 has a relatively higher specificity. Together, our data suggest that the specificity of sex hormones and antiandrogens can be modulated by some selective AR coactivators. These findings may not only help us to better understand the specificity of the sex hormones and antiandrogens, but also to facilitate the development of better antiandrogens or androgens to fight the androgen-related diseases, such as prostate cancer.
Assuntos
Proteínas Oncogênicas , Receptores Androgênicos/genética , Proteína do Retinoblastoma/farmacologia , Transativadores/farmacologia , Fatores de Transcrição , Transcrição Gênica/efeitos dos fármacos , Androgênios , Humanos , Coativadores de Receptor NuclearRESUMO
Overexpression of the HER2/Neu protooncogene has been linked to the progression of breast cancer. Here we demonstrate that the growth of prostate cancer LNCaP cells can also be increased by the stable transfection of HER2/Neu. Using AG879, a HER2/Neu inhibitor, and PD98059, a MAP kinase inhibitor, as well as MAP kinase phosphatase-1 (MPK-1), in the transfection assay, we found that HER2/Neu could induce prostate-specific antigen (PSA), a marker for the progression of prostate cancer, through the MAP kinase pathway at a low androgen level. Reporter assays and mammalian two-hybrid assays further suggest this HER2/Neu-induced androgen receptor (AR) transactivation may function through the promotion of interaction between AR and AR coactivators, such as ARA70. Furthermore, we found this HER2/Neu --> MAP kinase --> AR-ARAs --> PSA pathway could not be blocked completely by hydroxyflutamide, an antiandrogen used in the treatment of prostate cancer. Together, these data provide a novel pathway from HER2/Neu to AR transactivation, and they may represent one of the reasons for the PSA re-elevation and hormone resistance during androgen ablation therapy in prostate cancer patients.
Assuntos
Androgênios/genética , Proteínas Quinases Dependentes de Cálcio-Calmodulina/genética , Proteínas Oncogênicas , Receptor ErbB-2/genética , Receptores Androgênicos/genética , Fatores de Transcrição , Antagonistas de Androgênios/farmacologia , Androgênios/farmacologia , Divisão Celular/genética , Flavonoides/farmacologia , Flutamida/análogos & derivados , Flutamida/farmacologia , Regulação Neoplásica da Expressão Gênica/genética , Humanos , Masculino , Mutagênese Sítio-Dirigida , Coativadores de Receptor Nuclear , Antígeno Prostático Específico/genética , Neoplasias da Próstata/genética , Transdução de Sinais , Transativadores/genética , Ativação Transcricional , Transfecção , Células Tumorais Cultivadas , Tirfostinas/farmacologiaRESUMO
The effect of acute non-fatal haemorrhage on adrenocortical function was assessed in 19 Burmese subjects. The results indicated that acute non-fatal haemorrhage as produced by blood donation stimulated the adrenal cortex to increase its secretion.