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At least 271 records · Page 15Linked to original sources
PubMed2004

Activation of the orphan nuclear receptor RORalpha counteracts the proliferative effect of fatty acids on prostate cancer cells: crucial role of 5-lipoxygenase.

The incidence of prostate carcinoma is very low in Eastern countries, such as Japan, suggesting that life style conditions may play a crucial role in the development of this pathology. Dietary omega-6 polyunsaturated fatty acids, such as linoleic (LA) and arachidonic (AA) acids, have been shown to stimulate the proliferation of prostate cancer cells after being converted into 5-HETE by means of the 5-lipoxygenase (5-LOX) pathway. Blockade of 5-LOX activity has been proposed as an attractive target for the prevention of the mitogenic action of dietary fats on prostate cancer. The 5-LOX gene has been shown to carry a response element for the orphan nuclear receptor RORalpha (for its RORalpha1 isoform in particular) in its promoter region. We attempt to clarify whether activation of RORalpha might modulate the expression of 5-LOX, thus interfering with the mitogenic activity of fatty acids in prostate cancer cells. We show that in androgen-independent DU 145 prostate cancer cells, LA, AA and their metabolite 5-HETE exert a strong stimulatory action on cell proliferation. This effect is completely counteracted by the simultaneous treatment of the cells with a non redox inhibitor of 5-LOX activity. We then demonstrate that: i) RORalpha, and specifically its RORalpha1 isoform, is expressed in DU 145 cells; ii) activation of RORalpha, by means of the thiazolidinedione derivative CGP 52608 (the synthetic RORalpha activator), significantly reduces 5-LOX expression, both at mRNA (as evaluated by comparative RT-PCR) and at protein (as investigated by Western blot analysis) level (this was confirmed by the reduced activity of 5-LOX in CGP 52608 treated cells); and iii) the treatment of DU 145 cells with CGP 52608 completely abrogated the proliferative action of both LA and AA. These results have been confirmed in another androgen-independent prostate cancer cell line (PC3). Our data indicate that, by decreasing the expression of 5-LOX, activation of RORalpha might interfere with the mitogenic activity of fatty acids on prostate cancer. We have shown previously that CGP 52608 reduces the proliferation and the metastatic behavior of DU 145 cells. These observations indicate that the orphan nuclear receptor RORalpha might be considered as a molecular target for the development of new chemopreventive or chemotherapeutic strategies for prostate carcinoma.

Arachidonate 5-Lipoxygenase↗
PubMed2006

Ligand-independent orphan receptor TR2 activation by phosphorylation at the DNA-binding domain.

In a previous report we demonstrated protein kinase C (PKC)-mediated phosphorylation of the ligand-binding domain (LBD) of orphan nuclear receptor TR2. In this report, we provide the evidence of PKC-mediated phosphorylation of the DNA-binding domain (DBD) of TR2. Two PKC target sites were predicted within the DBD, at Ser-170 and Ser-185, but only Ser-185 was confirmed by MS. Phosphorylation of DBD facilitated DNA binding of the TR2 receptor and its recruiting of coactivator p300/CBP-associated factor (P/CAF). Ser-185 was required for DNA binding, whereas both Ser-170 and Ser-185 were necessary for receptor interaction with P/CAF. The P/CAF-interacting domain of TR2 was located in its DBD. A double mutant (Ser-170 and Ser-185) of TR2 significantly lowered the activation of its target gene RARbeta2. This study provides the first evidence for ligand-independent activation of TR2 orphan receptor through PTM at the DBD, which enhanced its DNA-binding ability and interaction with coactivator P/CAF.

Base Sequence↗
PubMed2003

TR2 orphan receptor functions as negative modulator for androgen receptor in prostate cancer cells PC-3.

BACKGROUND: Both androgen receptor (AR) and orphan receptor TR2 (TR2) belong to the steroid nuclear receptor superfamily and are expressed in prostate cancer tissue and cell lines. AR has been known to be involved in prostate proliferation and prostate cancer progression. AR binds to androgen response elements and regulates target gene expression via a mechanism involving coregulators. However, the function of TR2 in prostate and prostate cancer and the relationship between TR2 and AR in the prostate cancer is unclear. METHODS: Transient transfection and CAT reporter gene assays were employed to assess AR-mediated transactivation. The expression level of prostate specific antigen (PSA) was measured by Northern blot analysis. The interaction between AR and TR2 was assessed by glutathione-S-transferase (GST) pull-down assay and mammalian two-hybrid system assay. RESULTS: Orphan nuclear receptor TR2 suppressed androgen-mediated transactivation in prostate cancer PC-3 cells, and over-expression of TR2 suppressed PSA expression. The suppression of AR mediated transactivation by TR2 is not due to competition for the limited coregulator availability by these two receptors, but possibly through the interaction between TR2 and AR nuclear receptors. CONCLUSIONS: TR2 may function as a negative modulator to suppress AR function in prostate cancer. Further studies on how to control TR2 function may result in the ability to modulate AR function in prostate cancer.

Androgen Receptor Antagonists↗
PubMed1994

Characterization of the G-protein linked orphan receptor GPRN1/RDC1.

Site specific antibodies were raised against the second intracellular loop of the G-protein coupled orphan receptor GPRN1 for analysis of receptor protein expression from a number of sources. Immunoblot analyses showed GPRN1 to be a 60 kDa membrane bound glycoprotein. It was found in AR4-2J, PC12 and SK-N-MC cell lines. High amounts of GPRN1 were found in rat stomach, liver, lung, brain, small intestine and pancreas, with lower amounts in spleen and kidney: none was detectable in rat heart. This distribution differs markedly from that of the closely related orphan receptor RDC1. The receptor shows high evolutionary conservation: immunoreactive 60 kDa GPRN1 was detected in membrane glycoprotein fractions from the livers of rat, toad, chick, stingray and shark. It is therefore predicted that GPRN1 and RDC1 represent two tissue specific subtypes of a 60 kDa receptor for a ligand which has likely been highly conserved throughout evolution and which is active upon many organs of the body.

Amino Acid Sequence↗
PubMed1995

The orphan receptor TAK1 acts as a repressor of RAR-, RXR- and T3R-mediated signaling pathways.

Recently, we reported the cloning and characterization of the novel orphan receptor TAK1. In this study, we analyze the interaction of TAK1 with a variety of response elements (RE's) and demonstrate that TAK1 binds effectively to RE's composed of the core motif PuGGTCA configured in direct repeats spaced by one or more nucleotides. TAK1 bound poorly to palindromic or inverted palindromic motifs and was unable to bind to a single core motif, suggesting that a dimeric site is required for binding. Transfection experiments with CV-1 cells revealed that TAK1 is able to repress retinoid- and thyroid-hormone-induced transactivation through a subset of retinoid and thyroid hormone RE's. Our studies indicate that the antagonism of RAR-mediated transactivation does not involve the formation of heterodimers between TAK1 and RAR or RXR but is due to the competition of TAK1 homodimers with RAR-RXR heterodimers and RXR homodimers for binding to RARE and RXRE, respectively. Our results suggest that the orphan receptor TAK1 can be a negative modulator of the regulation of gene expression mediated by retinoid and thyroid hormone signaling pathways.

Animals↗
PubMed2001

Regulation of the nuclear orphan receptor Nur77 in bone by parathyroid hormone.

Osteoblasts function under the control of several hormones and growth factors. Among them, parathyroid hormone (PTH) and steroid hormones have significant effects on bone metabolism. We show that PTH induced the expression of Nur77, a member of the NGFI-B subfamily of nuclear orphan receptors in bone. PTH rapidly and transiently induced Nur77 mRNA in primary mouse osteoblasts that peaked at 1 h and at 10 nM of hormone. Cycloheximide did not affect the induction of Nur77 mRNA, suggesting that protein synthesis is not required for the PTH effect. PTH also induced Nur77 mRNA in calvariae cultures. Finally Nur77 protein expression was induced in nuclear protein extracts of cells treated with PTH. NGFI-B nuclear receptors have been implicated in retinoic acid, vitamin D, and thyroid hormone signaling. We propose that induction of NGFI-B nuclear orphan receptors represents a potential cross-talk mechanism between PTH and steroid hormone signaling to regulate bone metabolism.

Animals↗
PubMed2001

TR4 orphan receptor represses the human steroid 21-hydroxylase gene expression through the monomeric AGGTCA motif.

The human TR4 orphan receptor (TR4) is a member of the nuclear receptor superfamily. It functions as a transcriptional factor which regulates and controls many important physiological functions. It has been documented that TR4 may bind as a homodimer to a DNA response element containing two direct repeats of the AGGTCA consensus motif. Surprisingly, our data reveal that the expression of the human steroid 21-hydroxylase (21-OHase) gene could be repressed by TR4 via the monomeric AGGTCA motif (-228TR4RE) at its 5' flanking region (nucleotide numbers 1431-1444, 5'-GGAAAAAGGTCAGG-3'). Electrophoretic mobility shift assay showed specific binding with a dissociation constant of 0.4 nM between TR4 and the monomeric -288TR4RE motif. However, TR4 does not form heterodimers with either retinoid X receptor alpha or SHP (short heterodimer partner) orphan receptor. Additionally, both dual-luciferase and chloramphenicol acetyltransferase assays demonstrated that TR4 can function as a repressor via the -228TR4RE of the 21-OHase gene. In conclusion, our data suggest that TR4 may bind to a monomeric DNA response element and play an important role in the suppression of the 21-OHase gene expression.

5' Untranslated Regions↗
PubMed2002

An experimental validation of orphan genes of Buchnera, a symbiont of aphids.

Although Buchnera sp. APS, an intracellular symbiont of pea aphids, is a close relative of Escherichia coli, its genome has been extensively modified because of its prolonged intracellular life. In our previous studies on the Buchnera genome, computer analysis predicted three "orphan" genes, yba2, yba3, and yba4, which are open reading frames (ORFs) with no homologs in the database. In this paper, we successfully validated all these orphan genes by RT-PCR and Northern hybridization. The present study also revealed that yba3 and yba4 formed an operon, suggesting that they function in concert. Sequences around transcriptional start sites suggests that these genes are under the control of sigma 70. In view of codon usage and AT bias observed in these genes, it is likely that Buchnera have maintained them for an evolutionarily long time.

Amino Acid Sequence↗
PubMed2000

Hippocampal expression of the orphan nuclear receptor gene hzf-3/nurr1 during spatial discrimination learning.

The immediate-early gene hzf-3, also known as nurr1, is a member of the inducible orphan nuclear receptor family and is one candidate in the search for genes associated with learning and memory processes. Here we report that acquisition of a spatial food search task is accompanied by elevated levels of hzf-3 mRNA in the hippocampus. Adult male Long-Evans rats were handled, food-restricted, and allowed to habituate to the maze prior to training. During acquisition, rats were given one training session per day for 5 days. Each training session consisted of five trials in which animals searched the maze for food located in 4 of 16 holes in the floor of the maze. Training resulted in spatial acquisition of the task. Northern blot analysis showed significant increases in hippocampal hzf-3 mRNA 3 h after training in the maze. Next, brains were obtained from Naive, Habituated, Day 1, Day 3, and Day 5 animals and processed for in situ hybridization. The results showed significant increases of hzf-3 mRNA in CA1 and CA3 subregions of the dorsal hippocampus during acquisition of the task. We conclude that expression of the hzf-3 gene in the brain is associated with long-term spatial memory processes. The present results are the first to implicate an orphan nuclear receptor in long-term information storage in the hippocampus.

Animals↗
PubMed2000

Further pharmacological analysis of the orphan 5-HT receptors mediating feline vasodepressor responses: close resemblance to the 5-HT7, receptor.

It has been suggested that the late hypotensive response to serotonin (5-hydroxytryptamine; 5-HT) in vagosympathectomised cats, being potently mimicked by 5-carboxamidotryptamine (5-CT), not modified by ketanserin and blocked by methiothepin or methysergide, is mediated by '5-HT1-like' receptors. Nevertheless, current guidelines for 5-HT receptor classification refer to this receptor as an orphan receptor. Thus, the present study set out to reanalyse the above suggestion in terms of the classification schemes proposed in 1994 and 1998 by the NC-IUPHAR subcommittee on the classification of 5-HT receptors. Intravenous (i.v.) bolus injections of 5-CT (0.003-0.3 microg/kg), 5-HT (1-100 microg/kg) and 5-methoxytryptamine (5-MeO-T; 1-100 microg/kg) produced dose-dependent vasodepressor responses with a rank order of agonist potency of 5-CT >> 5-HT = 5-MeO-T with sumatriptan (10-300 microg/kg) virtually inactive. The vasodepressor responses to 5-HT, 5-CT and 5-MeO-T were not attenuated following i.v. administration of the antagonists GR127935 (5-HT(IB/ID); 30 microg/kg), tropisetron (5-HT3/4; 3000 microg/kg), (+/-)-pindolol (beta-adrenergic and 5-HT1A; 4000 microg/kg) or equivalent volumes of physiological saline. In contrast, the above vasodepressor responses were markedly and specifically antagonised by i.v. methiothepin (100 microg/kg), lisuride (30 microg/kg and 100 microg/kg), mesulergine (300 microg/kg and 1000 microg/kg) or LY215840 (300 microg/kg and 1000 microg/kg). The above lines of evidence, therefore, indicate that the orphan receptors mediating the vasodepressor responses to 5-HT in vagosympathectomised cats are pharmacologically similar to other 5-HT7 receptors mediating vascular and non-vascular responses (e.g. relaxation of the canine external carotid artery and guinea-pig ileum as well as feline tachycardia).

5-Methoxytryptamine↗
PubMed1998

Cloning and chromosomal mapping of an orphan chemokine receptor: mouse RDC1.

Degenerate RT-PCR was used to identify a new seven-transmembrane-spanning receptor expressed in astrocytes. A receptor, termed RDC1, displaying the characteristic structural features of a chemokine receptor was cloned. The predicted 362-amino-acid sequence displayed 92% and 91% similarity to the human and dog orphan receptor RDC1, respectively. In addition, RDC1 shares 43% amino acid similarity to rabbit and mouse CXCR2. Transcripts of RDC1 were found in astrocytes, heart, kidney, the mesangial tumor line MES-13, spleen, and neutrophils by means of northern blot. Using linkage analysis of interspecies backcross mice, we localized to chromosome 1 the genes for mouse CXCR2, CXCR4, and RDC1. Mouse RDC1 is linked to and lies between the genes for the mouse CXC chemokine receptors CXCR2 and CXCR4. The combined data of chromosomal location and sequence similarity suggest that RDC1 is an orphan CXC chemokine receptor.

Amino Acid Sequence↗
PubMed1998

Expression domains of the medaka (Oryzias latipes) Ol-Gsh 1 gene are reminiscent of those of clustered and orphan homeobox genes.

Screening of a medaka (Oryzias latipes) adult brain cDNA library, with a degenerated probe corresponding to the most conserved region of helix III of the homeodomain, led to the isolation of a gene homologous to a murine orphan Hox gene, named Gsh-1. We have called this gene Ol-Gsh 1 (Oryzias latipes-Gsh 1). Molecular analysis of the Ol-Gsh 1 putative protein points to potential functional domains which are highly conserved between fish and mouse genes. Whole-mount in situ hybridization shows that Ol-Gsh 1 is expressed in several waves during embryonic development. Transcripts are found in many regions of the central nervous system: the spinal cord, dorsal rhombencephalon, optic tectum, dorsal diencephalon, hypothalamus anlagen and rostral telencephalon. This multimodal expression pattern, strikingly conserved between fish and mammals, is reminiscent of both clustered and orphan homeobox genes. In addition, each expression wave is initiated in the fish embryo earlier than in the mammalian embryo, relative to the time scale defined by somitogenesis. We propose that Ol-Gsh 1 may be involved in conserved developmental pathways and in particular may be linked to proliferation events. Mouse Gsh-1 was shown to participate in neuro-endocrine functions of the hypothalamus. From late developmental stages onwards, Ol-Gsh 1 expression is also restricted to the hypothalamus. The expression pattern in this structure raises interesting questions concerning a fully or partially conserved function for these genes.

Amino Acid Sequence↗
PubMed2002

Successful reproduction in wild-released orphan chimpanzees (Pan troglodytes troglodytes).

We report a case of successful reproduction in wild-released orphan chimpanzees. Using non-invasive genetic analysis, we determined the paternity of an infant born to a female chimpanzee released by HELP (Habitat Ecologique et Liberté des Primates) Congo into the Conkouati-Douli National Park, Republic of Congo. The sire was a released male, thus demonstrating successful reproduction in both male and female released chimpanzees. These results provide evidence that release into the wild may be a viable response to the plight of orphan chimpanzees in Africa, and we discuss further applications of non-invasive genetic tagging to release programs.

Alleles↗
PubMed2006

Towards a definition of orphaned and vulnerable children.

The HIV epidemic presents challenges including orphans and a large mass of children rendered vulnerable by the epidemic and other societal forces. Focus on orphaned and vulnerable children (OVC) is important, but needs accurate definition. Twelve focus group interviews of service providers, leaders in these communities, OVC and their caretakers were conducted at six project sites across Botswana, South Africa and Zimbabwe to extend this definition. The loss of a parent through death or desertion is an important aspect of vulnerability. Additional factors leading to vulnerability included severe chronic illness of a parent or caregiver, poverty, hunger, lack of access to services, inadequate clothing or shelter, overcrowding, deficient caretakers, and factors specific to the child, including disability, direct experience of physical or sexual violence, or severe chronic illness. Important questions raised in this research include the long-term implications for the child and community, and the contribution of culture systems.

Child↗
PubMed2005

Transgenic rescue for characterizing orphan receptors: a review of delta2 glutamate receptor.

Even though the genomes of several major species have been sequenced, many orphan receptors with unknown ligands and mechanisms of action remain in the CNS. The delta2 glutamate receptor (GluRdelta2) is one of such receptors expressed predominantly in the cerebellar Purkinje cells. On the basis of amino acid similarity, it belongs to ionotropic glutamate receptor (iGluR) family, which mediates fast excitatory neurotransmission in the mammalian CNS. Although its null-mutant mice show prominent motor discoordination, the mechanisms by which GluRdelta2 participates in the cerebellar functions have been unclear. To gain insight into GluRdelta2's mechanisms, we recently generated mice that express either a wild-type or a mutant GIuRdelta2 transgene, in which the conserved arginine in GluRdelta2's N-terminal putative ligand-binding motif was disrupted. By breeding these transgenic mice onto a GluRdelta2 -/- background, we obtained two transgenic 'rescue' lines. Surprisingly, the mutant GluRdelta2 transgene was as effective as the wild-type GluRdelta2 in rescuing the GluRdelta2-null mice. As the disrupted arginine residue is highly conserved from ancestral bacterial periplasmic amino acid-binding proteins to mammalian iGluRs, we propose that GIuRdelta2 may not require glutamate-like amino acids and may function in an unconventional manner. This 'transgenic rescue' approach to investigating orphan receptors is a relatively easy but powerful method when a knockout mouse with a distinct phenotype is already available. The advantages and limitations of this approach, together with certain cautions in interpreting the resulting data, are discussed in this review.

Animals↗
PubMed1994

Orphan seven transmembrane domain receptors: reversing pharmacology.

The application of molecular genetic approaches to the study of seven transmembrane domain receptors has allowed the cloning of many receptors for which the ligand is initially unknown. These are commonly referred to as 'orphan receptors', and several have subsequently proved to be important pharmacological targets. This article discusses how these receptor sequences were isolated, and presents some of the methods by which the corresponding ligands were identified. These examples are used to propose a rational approach for the study of further orphan receptors.

Amino Acid Sequence↗
PubMed1996

HZF-3, an immediate-early orphan receptor homologous to NURR1/NOT: induction upon membrane depolarization and seizures.

Nuclear hormone receptors are thought to play important roles in the regulation of gene expression in the hippocampus. We report here the isolation of an additional member of this superfamily, HZF-3, which is expressed preferentially in the rat brain and therein within the hippocampus. HZF-3 cDNA encodes a 66.6-kDa protein with high homology to the inducible nuclear orphan receptors NURR1/NOT and NGFI-B. Like NURR1/NOT and NGFI-B, HZF-3 mRNA accumulates in PC12 cells subsequent to membrane depolarization. In the rat brain, HZF-3 expression is induced following seizures elicited by the chlorinated insecticide lindane. The time course of HZF-3 induction by membrane depolarization in PC12 cells and seizures in animals is more prolonged than that observed for other immediate-early genes, such as NGFI-B. Electrophoretic mobility shift assays demonstrated HZF-3 to interact specifically with the same DNA target element as NGFI-B: NBRE. These results suggest HZF-3 is a member of a distinct family of inducible orphan receptors which are likely to display synergistic and/or antagonistic regulatory functions in mediating signal-induced transcriptional responses in the nervous system.

Amino Acid Sequence↗
PubMed1996

A component of the 26S proteasome binds on orphan member of the nuclear hormone receptor superfamily.

The 26S proteasome complex plays a general role in turnover of both short and long lived proteins by specifically degrading ubiquitinated proteins. Recent evidence suggests that this large protease has more specific functions in a number of important cellular processes, ranging from activation of the transcription factor NFkB and antigen processing to transit through mitosis. We have identified a component of the 26S proteasome that interacts specifically with MB67, an orphan member of the nuclear hormone receptor superfamily. MIP224 (MB67 interacting protein) was isolated using the yeast two hybrid system and is apparently identical to the human 26S proteasome component TBP7. MIP224/TBP7 is one of several proteasomal proteins that share a strongly conserved ATPase domain (CAD) which is also present in a rapidly expanding superfamily of proteins with diverse functions. In yeast, MIP224 interacts specifically with MB67 and another closely related orphan receptor, but does not interact with several other receptor superfamily members tested. In mammalian cells, coexpression of MIP224 inhibits transactivation by MB67. MIP224 also interacts in yeast with other CAD proteins, including MSS1, which is proteasomal, and TRIP1, which is associated with transcriptional activation. This interaction of a proteasomal protein with a transcriptional protein suggests a previously unexpected link between the processes of protein degradation and transcriptional regulation.

ATPases Associated with Diverse Cellular Activitie↗