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Bernard Haendler

Publications and source records attributed to Bernard Haendler.

11 recordsLinked to original sources
PubMed2005

The ubiquitin-specific protease USP10 modulates androgen receptor function.

The role of the ubiquitin/proteasome system in degrading nuclear hormone receptors and regulating their transcriptional function has emerged in the last few years. We identified the ubiquitin-specific protease USP10 as part of DNA-bound androgen receptor (AR) complexes purified from nuclear extracts of PC-3 cells stably expressing the AR. The interaction between USP10 and the AR was confirmed by GST pull-down assays. Fluorescence microscopy documented that USP10 was localised in the nucleus and the cytoplasm. Cell-based transactivation assays in PC-3/AR cells revealed that overexpression of wild-type USP10, but not of an enzymatically inactive form, stimulated AR activity mediated by reporter constructs harbouring selective androgen response elements (AREs), non-selective steroid response elements (SREs) or the mouse mammary tumour virus (MMTV) promoter. Conversely, USP10 expression knock-down by siRNAs impaired the MMTV response to androgen. In summary, the data indicate that USP10 is a new cofactor that binds to the AR and stimulates the androgen response of target promoters. This finding underlines the role of the ubiquitin/proteasome system in modulating the AR function.

Androgens↗
PubMed2005

The role of DNA response elements as allosteric modulators of steroid receptor function.

Steroid receptors are ligand-activated transcription factors which control the expression of their target genes by binding to specific DNA elements. Consensus response elements have been delineated for the glucocorticoid, androgen, progesterone and mineralocorticoid receptors on one hand (steroid response element, SRE) and for the estrogen receptor on the other hand (estrogen response element, ERE). Small variations in these sequences not only affect the binding but may also have a dramatic impact on the transcriptional activity of steroid receptors. It has now become obvious that DNA response elements do not merely tether regulatory proteins to control regions of target genes but may additionally impart conformational changes onto the DNA-binding domain as well as to neighbouring domains of steroid receptors. This in turn will create unique platforms for selective recruitment of cofactors and possibly for induction of modifications in local chromatin architecture. An additional level of complexity is added by the frequent presence of multiple response elements in gene promoter regions. The allosteric effects of DNA response elements on steroid receptors may be essential for differential gene expression and this offers interesting perspectives for the identification of selective modulators.

Allosteric Regulation↗
PubMed2005

Androgen receptor function is modulated by the tissue-specific AR45 variant.

A naturally occurring variant of the human androgen receptor (AR) named AR45 has been identified. It lacks the entire region encoded by exon 1 of the AR gene and is composed of the AR DNA-binding domain, hinge region and ligand-binding domain, preceded by a novel seven amino-acid long N-terminal extension. A survey of human tissues revealed that AR45 was expressed mainly in heart and skeletal muscle. In cotransfection experiments, AR45 inhibited AR function, an effect necessitating intact DNA- and ligand-binding properties. Overexpression of AR45 reduced the proliferation rate of the androgen-dependent LNCaP cells, in line with the repressive effects of AR45 on AR growth-promoting function. AR45 interacted with the AR N-terminal domain in two-hybrid assays, suggesting that AR inhibition was due to the formation of AR-AR45 heterodimers. Under conditions where the transcriptional coactivator TIF2 or the oncogene beta-catenin were overexpressed, AR45 stimulated androgen-dependent promoters in presence of dihydrotestosterone. AR45 activity was triggered additionally by the adrenal androgen androstenedione in presence of exogenous TIF2. Altogether, the data suggest an important role of AR45 in modulating AR function and add a novel level of complexity to the mode of action of androgens.

Amino Acid Sequence↗
PubMed2004

Cyr61, a deregulated gene in endometriosis.

Gene expression profiling was performed to identify genes involved in the development of endometriosis. In the secretory phase of the menstrual cycle, several estrogen-regulated genes were up-regulated in endometria of women with endometriosis. The most consistent regulation with one of the highest factors was observed for the Cyr61 gene, which codes for a secreted, cysteine-rich, heparin-binding protein that promotes cell adhesion, migration, and neovascularization. Estrogen responsiveness of endometrial Cyr61 expression was suggested by the higher expression during the proliferative phase and the reduction observed in human endometrial fragments grafted into nude mice subsequently treated with an anti-estrogen. The expression level of Cyr61 was found to be further increased in ectopic endometriotic lesions, as compared to eutopic endometria. In these lesions, an imbalance in expression of the estrogen-converting enzymes 17beta-hydroxysteroid dehydrogenase type 1 and 2 was found, which might explain the elevated Cyr61 level. However, Cyr61 expression was not altered in endometriotic lesions of women treated with a GnRH agonist. These results suggest that Cyr61 may represent a gene characteristic for endometriosis and also play an important role in the development and persistence of endometriotic lesions.

17-Hydroxysteroid Dehydrogenases↗
PubMed2004

Cycle-dependent endometrial expression and hormonal regulation of the fibulin-1 gene.

Fibulin-1 is a secreted protein associated with elastic matrix fibres and basement membranes. It plays a role in stabilizing blood vessels and can also regulate cell motility and invasiveness. We studied the regulation of the fibulin-1 gene in the rat and human endometrium, an organ where cyclic tissue remodeling and angiogenesis take place. The rat fibulin-1C and -1D-specific DNA sequences were first identified and a comparison of the deduced amino acid sequence with the mouse and human counterparts showed a very strong conservation. The exon-intron structure was also maintained. Primers were derived for RT-PCR analysis of fibulin-1 expression in rat endometrium. The highest levels of fibulin-1C and -1D transcripts were measured at metestrous and diestrous, and in early pregnancy at day 3 post-coitum. In vivo studies showed stimulation of endometrial fibulin-1D expression after estrogen application, an effect prevented by parallel treatment with progesterone. Analysis of human endometrial tissues indicated that the fibulin-1D transcript levels were higher during the mid-secretory phase than during the proliferative and early secretory phases. Cultured human endometrial stromal cells treated with progesterone responded with a dramatic increase of fibulin-1 protein expression. This was enhanced by parallel treatment with epidermal growth factor and prevented by application of the antiprogestin RU486. Altogether the results show a cycle-dependent regulation of endometrial fibulin-1 expression controlled by both progesterone and estrogen. Based on its implication in tissue remodeling and angiogenesis, fibulin-1 may play an important role in endometrial receptivity for embryo implantation.

Amino Acid Sequence↗
PubMed2004

Novel molecular aspects of prostate carcinogenesis.

Prostate adenocarcinoma is one of the most frequently diagnosed forms of cancer in the male population of the Western world. The pivotal role of androgen and its receptor in this disease has been abundantly documented and indeed, chemical castration and treatment with antiandrogens are now standard therapies. However, relapse is often observed after 18-24 months, due to the remarkable ability of prostate tumour cells to adapt to low or undetectable androgen levels. Amplification and mutations of the androgen receptor (AR) gene have been described as well as alterations in cofactor expression and crosstalk with other signalling pathways. Another recent line of research focused on the re-programming of gene expression taking place in prostate tumours. Global expression profiling of normal and cancerous prostate tissues led to the identification of tumour-distinctive patterns. Validation studies are currently underway to identify novel drug targets as well as diagnostic and outcome prediction markers.

Animals↗
PubMed2003

Differential modulation of androgen receptor action by deoxyribonucleic acid response elements.

In addition to the steroid response elements (SREs), which are recognized by several steroid receptors, a second class of DNA elements exhibiting selectivity for the androgen receptor (AR) and named androgen response elements (AREs) has been identified. Here we provide evidence for the differential role of these element classes in modulating AR function. AR complexes attached to response elements representative of each class were purified. Limited protease digests of ARE- or SRE-bound AR complexes led to the generation of different patterns, in line with differential accessibilities. In transactivation assays, mutations in the AR dimerization interface of the DNA-binding domain had various effects, depending on the response elements tested. The R598D mutant displayed much enhanced activity on SREs, whereas far less effect was seen on the selective AREs. The A596T mutant had reduced activity on AREs but not on SREs. Ectopic expression of the coactivators transcriptional intermediary factor 2 (TIF2) and ARA55 stimulated AR activity to different extents, depending on the response element. When using cysteine-rich secretory protein 1 (CRISP-1) SRE as reference, the most significant difference was observed with Pem ARE-2. A differential response of each element class was furthermore observed in the presence of two enzymes involved in the sumoylation pathway. Ubiquitin-conjugating enzyme 9 (Ubc9) overexpression enhanced AR action conveyed by SREs, whereas little effect was seen on Pem ARE-1 and repression on Pem ARE-2. Protein inhibitor of activated STAT (PIAS)xalpha overexpression had little influence on SRE-mediated AR activity but was repressive when using AREs. Altogether, these results demonstrate that DNA response elements play an important modulatory role in transmitting AR action and may be determinative for specificity of gene expression in cell or tissue types.

Animals↗
PubMed2003

Androgen receptor and prostate cancer: molecular aspects and gene expression profiling.

Prostate cancer represents a major health problem in the aging population of Western countries. Androgen ablation is one of the preferred treatments for this disease; unfortunately, relapse is often observed, and no therapeutic agent is available at this stage of the disease. Although numerous studies indicate that the androgen receptor (AR) remains largely involved at the late stages of the disease, the molecular mechanisms responsible for the transition from an androgen-dependent to an androgen-independent state are still poorly understood. Newly discovered aspects of the mode of action of AR, such as cross-talk with other signaling pathways, post-translational modifications, interaction with co-factors and allosteric modulation by DNA response elements have helped to broaden our knowledge on how target gene transcription is regulated. In addition, the gene expression profiles recently determined on prostate-derived cell lines and on normal and diseased prostate tissues should help to decipher the mechanisms leading to uncontrolled growth and metastasis.

Androgens↗
PubMed2002

OTEX, an androgen-regulated human member of the paired-like class of homeobox genes.

paired genes emerged early in evolution and code for homeobox transcription factors, having fundamental roles in various biological processes. We identified a novel human member of the paired-like class, which we named OTEX. A phylogenetic analysis revealed that OTEX belonged to the recently defined PEPP subfamily of paired-like homeobox genes. It was organized into three introns and, like the other PEPP genes, it was mapped to chromosome X. Its transcripts were detected mainly in the ovary, testis and epididymis, but also in the prostate and mammary gland. In the PC-3/ARwt prostate cell line, OTEX expression was stimulated dramatically following androgen treatment. Immunofluorescence studies revealed an exclusively nuclear localization of the OTEX protein. Mutation of the RARCRRHQRE amino acid sequence present at the C-terminus of the OTEX homeodomain resulted in a mainly cytoplasmic localization, indicating that this motif harboured the nuclear localization signal. No inherent transactivation function was seen for OTEX using the one-hybrid assay, and no homodimer formation was observed in the two-hybrid assay, suggesting that additional partners were needed for this activity. Taken together, the data show that OTEX represents a novel, androgen-regulated, paired-like homeobox protein, with possibly an important role in human reproduction.

Amino Acid Sequence↗
PubMed2002

Receptor type I and type II binding regions and the peptidyl-prolyl isomerase site of cyclophilin B are required for enhancement of T-lymphocyte adhesion to fibronectin.

Cyclophilin B (CyPB), a cyclosporin A (CsA) binding protein, interacts with two types of binding sites at the surface of T-lymphocytes. The type I sites correspond to functional receptors involved in endocytosis and the type II sites to sulfated glycosaminoglycans (GAGs). Mutational analysis of CyPB has revealed that W128, which is part of the CsA-binding pocket, is implicated in the binding to the functional type I receptors and that two amino acid clusters located in the N-terminus ensure the binding to GAGs. The peptidyl-prolyl isomerase activity of CyPB is not required for receptor binding. We have recently demonstrated that CyPB enhances adhesion of peripheral blood T-lymphocytes to fibronectin, a component of the extracellular matrix. We intended to identify additional amino acids involved in the binding of CyPB to its functional type I receptor and to determine regions responsible for the stimulation of peripheral blood T-lymphocyte adhesion. We determined that residues R76, G77, K132, D155, and D158 of the calcineurin (CN) interacting region were implicated in the recognition of type I receptor but not of GAGs. We also found that two different changes in the N-terminal extension that abated binding to GAGs prevented adhesion of peripheral blood T-lymphocytes to coated CyPB, whereas abbrogation of the PPIase activity had no effect. On the other hand, the adhesion of peripheral blood T-lymphocytes to coated fibronectin was not stimulated by CyPB mutants devoid of either type I receptor or GAGs binding activity or by mutants of the PPIase site. Altogether, the results demonstrate that different regions of CyPB are involved in peripheral blood T-lymphocyte activation and imply a novel important physiological function for peptidyl-prolyl isomerase activity.

Adjuvants, Immunologic↗