UMLS:C1519176 - FACTA Search

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Query: UMLS:C1519176 (PSA)
5,490 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Androgens directly regulate a vast number of physiological events. These direct androgen effects are mediated by a nuclear receptor that exhibits four major functions or activities: steroid binding, DNA binding, transactivation, and nuclear localization. The SBD consists of a hydrophobic pocket of amino acids that exhibits high-affinity, androgen-specific binding. Based on studies of mutant AR, it appears that a number of different amino acids contribute to the steroid binding characteristics of the AR. The DNA binding domain confers sequence-specific binding to structures called androgen-responsive elements. The specificity of steroid binding and DNA binding provides a crucial basis for androgen-specific regulation of target genes. The nuclear localization signal shares homology with known nuclear localization signals and, coupled with the presence of androgens, is responsible for localizing the AR to the nucleus. The transactivation functions reside mostly in the NH2 terminus but the responsible domains are as yet poorly defined. Though the different domains can act as independent moieties, one domain can clearly alter the behavior of another domain. For instance, the SBD appears to inhibit the transactivating functions until steroid is bound and the amino terminus prevents DNA binding activity until steroid is bound. The relative ease of introducing mutations with polymerase chain reaction technology will facilitate further delineation of critical amino acids and domains responsible for the various activities of the AR. The recent cloning and characterization of AR promoters revealed that the AR genes are driven by a TATA-less promoter characteristics of housekeeping genes. Analysis of transcription rates, mRNA levels, and protein levels indicates that androgens and pkA and pkC pathways modulate expression of AR mRNA and protein. This indicates that the same signal pathways that interact to regulate androgen target genes also regulate the levels of AR in the target tissues. Surprisingly few androgen-regulated genes have been well characterized for the mechanisms by which androgen regulates the gene. The C(3), Slp, probasin, PSA, and hKLK2 genes have provided examples where androgens regulate transcription. Posttranscriptional regulation by androgens has been demonstrated for the SVP1, 2, 3, and 4 and AR genes. The mechanisms underlying posttranscriptional regulation are poorly defined but substantial progress has been made in defining the critical elements that mediate transcriptional effects of androgens. Transcriptional effects are mediated through binding of androgen-AR complexes to specific DNA sequences called AREs. Simple AREs such as those found in C(3) and kallikrein genes tend to be permissive in that GR and PR can also act through the same element.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Molecular mechanisms of androgen action. 781 74

Accumulating evidence indicates that androgens and the androgen receptor modulate the development and progression of breast adenocarcinoma; however, the precise role and actions remain poorly defined. We examined previously the steroid hormone regulation of 2 known androgen-regulated kallikreins, KLK3 (encoding PSA) and KLK2 (encoding human kallikrein 2 or hK2) in BT-474, T-47D, ZR75-1, MCF-7, MFM-223 and BT-20 human breast cancer cells and found that they were differentially regulated, with the cells showing variable responses to androgen. To determine if this variable response was reflected by differences in androgen receptor, we characterized the expression of androgen receptor in these cells by Western blot analysis and saturation binding analysis. In addition, we sequenced androgen receptor cDNA from each of these cell lines to check whether any androgen receptor mutations were present. The expression of 11 nuclear receptor co-regulatory factors (SRC-1, AIB1, ARA24, ARA54, ARA55, ARA70, ARA160, FHL2, PDEF, NCoR1, SMRT) was compared in these cell lines by semi-quantitative RT-PCR to determine if the pattern of receptor co-activators or -repressors expressed in these cells might explain the differential regulation of KLK2 and KLK3. The levels of androgen receptor varied among the cell lines, but did not correlate with hK2 and PSA secretion determined previously. No mutations within the coding regions of the receptor were detected. With the exception of receptor expressed by MCF-7 cells, the polymorphic CAG repeat length was in the normal range. Every breast cancer cell line exhibited a distinct expression pattern of the nuclear receptor co-regulators examined raising the possibility that the relative levels of these co-activators/-repressors might differentially modulate androgen receptor transcriptional activity within the promoter/enhancer region of KLK2 and KLK3 of these cells.
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PMID:Characterization of androgen receptor and nuclear receptor co-regulator expression in human breast cancer cell lines exhibiting differential regulation of kallikreins 2 and 3. 1212 98

We have investigated the role of corepressors SMRT (silencing mediator of retinoid and thyroid hormone receptor) and N-CoR (nuclear receptor corepressor) in transcriptional regulation by androgen receptor (AR) in the LNCaP prostate cancer cell line. Using specific small interference RNAs to knock down SMRT and/or N-CoR in LNCaP cells, we found that SMRT and N-CoR not only mediate antagonist-dependent inhibition of AR activation but also have a widespread role in suppressing agonist-dependent activation of several AR target genes we have tested, including PSA (prostate-specific antigen), TSC22 (TSC22 domain family member 1), NKX3-1 (NK3 transcription factor locus 1), and B2M(beta-2-microglobulin). By sequencing analysis followed by analysis of physical association by chromatin immunoprecipitation assay, we mapped the putative androgen response elements in the NKX3-1 and B2M. Consistent with a role in both antagonist- and agonist-regulated transcription by AR, chromatin immunoprecipitation analysis revealed that both SMRT and N-CoR were recruited by AR to these genes in the presence of either flutamide or R1881. Knocking down SMRT and N-CoR enhanced the recruitment of the coactivators steroid receptor coactivator 1 and p300 by agonist-bound AR and led to increased hyperacetylation of histone H3 and H4, suggesting that the corepressors actively compete with coactivators for binding to agonist-bound AR. Taken together, our data indicate that SMRT and N-CoR corepressors are involved in transcriptional regulation by both agonist- and antagonist-bound AR and regulate the magnitude of hormone response, at least in part, by competing with coactivators.
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PMID:The corepressors silencing mediator of retinoid and thyroid hormone receptor and nuclear receptor corepressor are involved in agonist- and antagonist-regulated transcription by androgen receptor. 1637 95

The mechanisms by which androgen receptor (AR) antagonists inhibit AR activity, and how their antagonist activity may be abrogated in prostate cancer that progresses after androgen deprivation therapy, are not clear. Recent studies show that AR antagonists (including the clinically used drug bicalutamide) can enhance AR recruitment of corepressor proteins [nuclear receptor corepressor (NCoR) and silencing mediator of retinoid and thyroid receptors (SMRT)] and that loss of corepressors may enhance agonist activity and be a mechanism of antagonist failure. We first show that the agonist activities of weak androgens and an AR antagonist (cyproterone acetate) are still dependent on the AR NH(2)/COOH-terminal interaction and are enhanced by steroid receptor coactivator (SRC)-1, whereas the bicalutamide-liganded AR did not undergo a detectable NH(2)/COOH-terminal interaction and was not coactivated by SRC-1. However, both the isolated AR NH(2) terminus and the bicalutamide-liganded AR could interact with the SRC-1 glutamine-rich domain that mediates AR NH(2)-terminal binding. To determine whether bicalutamide agonist activity was being suppressed by NCoR recruitment, we used small interfering RNA to deplete NCoR in CV1 cells and both NCoR and SMRT in LNCaP prostate cancer cells. Depletion of these corepressors enhanced dihydrotestosterone-stimulated AR activity on a reporter gene and on the endogenous AR-regulated PSA gene in LNCaP cells but did not reveal any detectable bicalutamide agonist activity. Taken together, these results indicate that bicalutamide lacks agonist activity and functions as an AR antagonist due to ineffective recruitment of coactivator proteins and that enhanced coactivator recruitment, rather than loss of corepressors, may be a mechanism contributing to bicalutamide resistance.
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PMID:Activity of androgen receptor antagonist bicalutamide in prostate cancer cells is independent of NCoR and SMRT corepressors. 1780 55

The estrogen receptor-related receptor alpha (ERRalpha) is an orphan member of the nuclear receptor superfamily that has been shown to interfere with the estrogen-signaling pathway. In this report, we demonstrate that ERRalpha also cross-talks with signaling driven by other steroid hormones. Treatment of human prostatic cells with a specific ERRalpha inverse agonist reduces the expression of several androgen-responsive genes, in a manner that does not involve perturbation of androgen receptor expression or activity. Furthermore, ERRalpha activates the expression of androgen response elements (ARE)-containing promoters, such as that of the prostate cancer marker PSA, in an ARE-dependent manner. In addition, promoters containing a steroid response element can be activated by all members of the ERR orphan receptor subfamily, and this, even in the presence of antisteroid compounds.
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PMID:The orphan receptor ERRalpha interferes with steroid signaling. 1869 14

The androgen receptor (AR) is a ligand activated nuclear receptor, which regulates transcription and stimulates growth of androgen dependent prostate cancer. To regulate transcription, AR recruits a series of coactivators that modify chromatin and facilitate transcription. However, information on ligand and target gene-specific requirements for coactivators is limited. We compared the actions of the p160 coactivators SRC-1 and SRC-3/RAC3 with SRA (steroid receptor RNA activator). All three coactivate AR in the presence of agonist as expected. However, overexpression of either SRC-1 or SRC-3 increased AR activity in response to the partial antagonist, cyproterone acetate, whereas SRA was unable to stimulate AR activity under these conditions. Using siRNA to reduce expression of these coactivators in LNCaP cells, we also found promoter specific requirement for these coactivators. SRC-3 is required for optimal androgen dependent induction of PSA, TMPRSS2, and PMEPA1 whereas SRA is required only for optimal induction of the TMPRSS2 gene. These data indicate that different groups of AR target genes have distinct requirements for coactivators and response to AR ligands.
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PMID:Coactivator selective regulation of androgen receptor activity. 1946 89

Signaling through the androgen receptor (AR) plays a critical role in prostate cancer progression. The AR is a classical nuclear receptor (NR) providing a link between signaling molecule and transcription response. Histone deacetylase inhibitors- (HDACI) have antiproliferative and proapoptotic effects on prostate cancer cells and their implication in silence AR signaling may have potential therapeutic use. We aimed to study the inhibitory effects of the corepressor SMRT (Silencing Mediator for Retinoid and Thyroid -hormone receptors) which forms a complex together with nuclear receptor corepressor (N-CoR) and with histone deacetylase 3 (HDAC3) on AR activity.The androgen-sensitive prostate cancer cell line LNCaP and androgen-insensitive prostate cancer cell line C4-2 both AR-positive, and androgen-insensitive DU145 and PC3 prostate cancer cell lines were treated with two HDACIs, sodium butyrate (NaB) and/or trichostatin A (TSA). We amplified immunoprecipitated DNA by conventional PCR and in the -following step we used the chromatin immunoprecipitation (ChIP) analysis coupled with quantitative PCR for monitoring NaB induced formation of AR-SMRT/N-CoR complex binding on the PSA promoter. The co-immunoprecipitation assay revealed increase in AR-SMRT formation in NaB treated cells. Simultaneously, the Western blot analysis showed a significant decrease in AR protein expression. In conclusion, the inhibitory effect of NaB on AR gene expression seems to be specific and unique for prostate cancer AR-positive cell lines and corresponds with its ability to stimulate AR-SMRT complex formation. We suggest that AR and SMRT/N-CoR corepressors may form a stable complex in vitro and NaB may facilitate the interaction between AR nuclear steroid receptor and SMRT corepressor prote.
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PMID:Binding of AR to SMRT/N-CoR complex and its co-operation with PSA promoter in prostate cancer cells treated with natural histone deacetylase inhibitor NaB. 2056 94

Signaling through the androgen receptor (AR) plays a critical role in prostate cancer progression. The AR is a classical nuclear receptor (NR) providing a link between signaling molecule and transcription response. Histone deacetylase inhibitors (HDACI) have antiproliferative and proapoptotic effects on prostate cancer cells and their implication in silence AR signaling may have potential therapeutic use. We aimed to study the inhibitory effects of the corepressor SMRT (Silencing Mediator for Retinoid and Thyroid hormone receptors) which forms a complex together with nuclear receptor corepressor (N-CoR) and with histone deacetylase 3 (HDAC3) on AR activity. The androgen-sensitive prostate cancer cell line LNCaP and androgen-insensitive prostate cancer cell line C4-2 both AR-positive, and androgen-insensitive DU145 and PC3 prostate cancer cell lines were treated with two HDACIs, sodium butyrate (NaB) and/or trichostatin A (TSA). We amplified immunoprecipitated DNA by conventional PCR and in the following step we used the chromatin immunoprecipitation (ChIP) analysis coupled with quantitative PCR for monitoring NaB induced formation of AR-SMRT/N-CoR complex binding on the PSA promoter. The co-immunoprecipitation assay revealed increase in AR-SMRT formation in NaB treated cells. Simultaneously, the Western blot analysis showed a significant decrease in AR protein expression. Furthermore, we estimated the reduced presence of HDAC2 and HDAC3 proteins by NaB and TSA treatment in AR-negative DU145 cell line. In conclusion, the inhibitory effect of NaB on AR gene expression seems to be specific and unique for prostate cancer AR-positive cell lines and corresponds with its ability to stimulate AR-SMRT complex formation. We suggest that AR and SMRT/N-CoR corepressors may form a stable complex in vitro and NaB may facilitate the interaction between AR nuclear steroid receptor and SMRT corepressor protein.
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PMID:Formation of AR-SMRT binding in prostate cancer cells treated with natural histone deacetylase inhibitor. 2117 66

The androgen receptor (AR) is a ligand-inducible transcription factor, a member of the nuclear receptor superfamily, which plays an important role in the development and progression of prostate cancer (CaP). The transformation to CaP has been linked to several somatic AR gene mutations and changes in AR protein complex formation, which in turn increase the potential activity of the receptor. Thus, to address the mechanism of AR-mediated neoplastic transformation, we developed in vitro methodology to isolate and characterize, via mass spectrometry, AR complexes of three AR genetic variants: wild type-AR, and two somatic gain-of-function AR prostatic mutants (T877A-AR and 0CAG-AR isoforms). To fully characterize the significance of our large raw data set, we employed a sophisticated systems biology approach to create an integrative protein-interaction network profile for each AR isoform. Our comparative analysis identified subnetwork cluster profiles for AR isoforms (WT, T877A, and 0CAG) that segregated AR isoforms on the basis of androgen stimulation conditions and mutant aggressiveness. Furthermore, results from additional correlative gene microarray analysis studies of all three AR isoform (WT, T877A, 0CAG) subnetwork clusters were assessed and found to be significantly enriched in tumor versus normal prostate tissues. We also identified two AR-interaction clusters, containing 21 and 30 proteins, respectively, that showed unfavourable prognosis outcome of recurrent cancers, on the basis of PSA, Gleason score and combined PSA/Gleason score. In conclusion, we have characterized a large panel of novel AR-interacting proteins, through a combined proteomics/systems biology screen, that are of clinical relevance and could potentially serve as novel markers for diagnosis and prognosis of CaP.
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PMID:Dynamic rewiring of the androgen receptor protein interaction network correlates with prostate cancer clinical outcomes. 2190 Nov 93

Androgen receptor (AR) is a member of the nuclear receptor family of transcription factors. Upon binding to androgens, AR becomes transcriptionally active to regulate the expression of target genes that harbor androgen response elements (AREs) in their promoters and/or enhancers. AR is essential for the growth and survival of prostate cancer cells and is therefore a target for current and next-generation therapeutic modalities against prostate cancer. Pathophysiologically relevant protein-protein interaction networks involving AR are, however, poorly understood. In this study, we identified the protein FUsed/Translocated in LipoSarcoma (FUS/TLS) as an AR-interacting protein by co-immunoprecipitation of endogenous proteins in LNCaP human prostate cancer cells. The hormonal response of FUS expression in LNCaP cells was shown to resemble that of other AR co-activators. FUS displayed a strong intrinsic transactivation capacity in prostate cancer cells when tethered to basal promoters using the GAL4 system. Chromatin immunoprecipitation experiments showed that FUS was recruited to ARE III of the enhancer region of the PSA gene. Data from ectopic overexpression and "knock-down" approaches demonstrated that AR transcriptional activity was enhanced by FUS. Depletion of FUS reduced androgen-dependent proliferation of LNCaP cells. Thus, FUS is a novel co-activator of AR in prostate cancer cells.
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PMID:FUS/TLS is a co-activator of androgen receptor in prostate cancer cells. 2190 21

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