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PubMed1995

Identification of human TR2 orphan receptor response element in the transcriptional initiation site of the simian virus 40 major late promoter.

A DNA response element (TR2RE-SV40) for the TR2 orphan receptor, a member of the steroid-thyroid hormone receptor superfamily, has been identified in the simian virus 40 (SV40) +55 region (nucleotide numbers 368-389, 5'-GTTAAGGTTCGTAGGTCATGGA-3'). Electrophoretic mobility shift assay, using in vitro translated TR2 orphan receptor with a molecular mass of 67 kilodaltons, showed a specific binding with high affinity (dissociation constant = 9 nM) for this DNA sequence. DNA-swap experiments using chloramphenicol acetyl-transferase assay demonstrated that androgen can suppress the transcriptional activities of SV40 early promoter via the interaction between this TR2RE-SV40 and the chimeric receptor AR/TR2/AR with the DNA-binding domain of the TR2 orphan receptor flanked by the N-terminal and androgen-binding domains of the androgen receptor. In addition, this TR2RE-SV40 can function as a repressor to suppress the transcriptional activities of both SV40 early and late promoters. Together, these data suggest the TR2RE-SV40 may represent the first identified natural DNA response element for the TR2 orphan receptor that may function as a repressor for the SV40 gene expression.

Animals↗
PubMed1995

Identification of dynorphins as endogenous ligands for an opioid receptor-like orphan receptor.

To identify the endogenous ligands for a cloned orphan receptor that shares high degrees of sequence homology with opioid receptors, this orphan receptor was expressed in Xenopus oocytes and in mammalian cell lines CHO-K1 and HEK-293. The coupling of the receptor to a G protein-activated K+ channel was used as a functional assay in oocytes. Endogenous opioid peptide dynorphins were found to activate the K+ channel by stimulating the orphan receptor. This activation was dose-dependent, with EC50 values at 45 and 37 nM for dynorphin A and dynorphin A-(1-13), respectively. The dynorphin effect was antagonized by the non-selective opioid antagonist naloxone but at rather high concentrations in the micromolar range. Naloxone also caused a rightward shift of the dose-response curve for dynorphin A, suggesting a competitive antagonism mechanism. In transiently transfected cells, 5 microM dynorphin A-(1-13) inhibited the forskolin-stimulated cyclic AMP increase by 51 and 35% in CHO-K1 and HEK-293 cells, respectively. Other classes of endogenous opioids, i.e. enkephalins and endorphins, caused very little activation of this receptor. These results suggest that this orphan receptor is a member of the opioid receptor family and that dynorphins are endogenous ligands for this receptor.

Animals↗
PubMed1999

Identification of nuclear orphan receptors as regulators of expression of a neurotransmitter receptor gene.

Nuclear orphan receptors are known to be important mediators of neurogenesis, but the target genes of these transcription factors in the vertebrate nervous system remain largely undefined. We have previously shown that a 500-base pair fragment in the first intron of the GRIK5 gene, which encodes the kainate-preferring glutamate receptor subunit KA2, down-regulates gene expression. In our present studies, mutation of an 11-base pair element within this fragment resulted in a loss of nuclear protein binding and reverses negative regulation by the intron. Using yeast one-hybrid screening, we have identified intron-binding proteins from rat brain as COUP-TFI, EAR2, and NURR1. Gel shift studies with postnatal day 2 rat brain extract indicate the presence of COUP-TFs, EAR2, and NURR1 in the DNA-protein complex. Competition assays with GRIK5-binding site mutations show that the recombinant clones exhibit differential binding characteristics and suggest that the DNA-protein complex from postnatal day 2 rat brain may consist primarily of EAR2. The DNA binding activity was also observed to be enriched in rat neural tissue and developmentally regulated. Co-transfection assays showed that recombinant nuclear orphan receptors function as transcriptional repressors in both CV1 cells and rat CG4 oligodendrocyte cells. Direct interaction of the orphan receptors with and relief of repression by TFIIB indicate likely role(s) in active and/or transrepression. Our findings are thus consistent with the notion that multiple nuclear orphan receptors can regulate the transcription of a widely expressed neurotransmitter receptor gene by binding a common element in an intron and directly modulating the activity of the transcription machinery.

Animals↗
PubMed2004

Identification of specific ligands for orphan olfactory receptors. G protein-dependent agonism and antagonism of odorants.

Olfactory receptors are the largest group of orphan G protein-coupled receptors with an infinitely small number of agonists identified out of thousands of odorants. The de-orphaning of olfactory receptor (OR) is complicated by its combinatorial odorant coding and thus requires large scale odorant and receptor screening and establishing receptor-specific odorant profiles. Here, we report on the stable reconstitution of OR-specific signaling in HeLa/Olf cells via G protein alphaolf and adenylyl cyclase type-III to the Ca2+ influx-mediating olfactory cyclic nucleotide-gated CNGA2 channel. We demonstrate the central role of Galphaolf in odorant-specific signaling out of OR. The employment of the non-typical G protein alpha15 dramatically altered the odorant specificities of 3 of 7 receptors that had been characterized previously by different groups. We further show for two OR that an odorant may be an agonist or antagonist, depending on the G protein used. HeLa/Olf cells proved suitable for high-throughput screening in fluorescence-imaging plate reader experiments, resulting in the de-orphaning of two new OR for the odorant (-)citronellal from an expression library of 93 receptors. To demonstrate the G protein dependence of its odorant response pattern, we screened the most sensitive (-)citronellal receptor Olfr43 versus 94 odorants simultaneously in the presence of Galpha15 or Galphaolf. We finally established an EC50-ranking odorant profile for Olfr43 in HeLa/Olf cells. In summary, we conclude that, in heterologous systems, odorants may function as agonists or antagonists, depending on the G protein used. HeLa/Olf cells provide an olfactory model system for functional expression and de-orphaning of OR.

Acyclic Monoterpenes↗
PubMed2004

Enabling households to support successful migration of AIDS orphans in southern Africa.

Most southern African orphans are cared for by extended families but the implications of the spatial dispersal of such families are seldom recognized: orphans often have to migrate to new homes and communities. This paper, based on qualitative research conducted with children and guardians in urban and rural Lesotho and Malawi, examines orphans' migration experiences in order to assess how successful migration might best be supported. Most children found migration traumatic in the short term, but over time many settled into new environments. Although much AIDS policy in southern Africa stresses the role of communities, the burden of care lay with extended family households. Failed migrations, which resulted in renewed migration and trauma, were attributable to one of two household-level causes: orphans feeling ill-treated in their new families or changes in guardians' circumstances. Policy interventions to reduce disruption and trauma for young AIDS migrants should aim at facilitating sustainable arrangements by enabling suitable households to provide care. Reducing the economic costs of caring for children, particularly school-related costs, would: allow children to stay with those relatives (e.g. grandparents) best able to meet their non-material needs; reduce resentment of foster children in impoverished households; and diminish the need for multiple migrations.

Acquired Immunodeficiency Syndrome↗
PubMed2003

Birth and death of orphan genes in Rickettsia.

The origin and evolution of the thousands of species-specific genes with unknown functions, the so-called orphan genes, has been a mystery. Here, we have studied the rates and patterns of orphan sequence evolution, using the Rickettsia as our reference system. Of the Rickettsia conorii orphans examined in this study, 80% were found to be short gene fragments or fusions of short segments from neighboring genes. We reconstructed the putative sequences of the full-length genes from which the short orphan fragments are thought to have originated. One of the genes thus reconstructed displays weak similarity to the ankyrin-repeat protein family, an identification that is strongly supported by comparative molecular modeling. Studies of the patterns of gene fragmentation underscore the importance of short repeated sequences as targets for recombination events that result in sequence loss and the formation of short, transient open reading frames. Our analysis demonstrates that gene sequences present in the common ancestor can be inferred even in cases when no full-length open reading frame is present in any of the contemporary species. Such reconstructions support the identification of lost protein functions and hint at important lifestyle changes.

Base Sequence↗
PubMed2005

Factors associated with institutionalization of children orphaned by AIDS in a population-based survey in Porto Alegre, Brazil.

BACKGROUND: There are increasing numbers of children orphaned by AIDS, especially in countries without universal free AIDS treatment. As institutionalization is associated with bad health and developmental outcomes, we have identified the factors associated with the institutionalization of AIDS orphans in a population-based survey in a city in southern Brazil. METHODS: Using AIDS mortality and healthcare registries from 1998 to 2001, a cross-sectional study was conducted among the caregivers of children aged 0-14 years who were the survivors of parents dying of AIDS in Porto Alegre. Data were collected by a household survey using a structured questionnaire. RESULTS: Out of 1131 orphans identified, 75.4% of their caregivers participated. Among participants, 70% had lost their father and 50% their mother, and 21% had lost both parents. At the time of the survey, 41% of the children lived with the mother, 25% lived with grandparents and 5% lived in institutions. In multivariate analysis, HIV positivity multiplied the child's chances of living in an institution by a factor of 4.6, losing its mother by 5.9, losing both parents by 3.7, and having a non-white mother by 4.0. CONCLUSION: This study provides population-based data on what has become of the children of individuals dying of AIDS. Improving the quality of life and averting the institutionalization of AIDS orphans requires interventions to promote the survival of mothers living with AIDS, as well as specific interventions for child family placement. Reducing the stigma of HIV infection in children and racial discrimination present challenges in Brazil.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Reverse transcriptase-polymerase chain reaction validation of 25 "orphan" genes from Escherichia coli K-12 MG1655.

Despite the accumulation of sequence information sampling from a broad spectrum of phyla, newly sequenced genomes continue to reveal a high proportion (50%-30%) of "uncharacterized" genes, including a significant number of strictly "orphan" genes, i.e., putative open reading frames (ORFs) without any resemblance to previously determined protein-coding sequences. Most genes found in databases have only been predicted by computer methods and have never been experimentally validated. Although theoretical evolutionary arguments support the reality of genes when homologs are found in a variety of distant species, this is not the case for orphan genes. Here, we report the direct reverse transcriptase-polymerase chain reaction assay of 25 strictly orphan ORFs of Escherichia coli. Two growth conditions, exponential and stationary phases, were tested. Transcripts were identified for a total of 19 orphan genes, with 2 genes found to be expressed in only one of the two growth conditions. Our results suggest that a vast majority of E. coli ORFs presently annotated as "hypothetical" correspond to bona fide genes. By extension, this implies that randomly occurring "junk" ORFs have been actively counter selected during the evolution of the dense E. coli genome.

Escherichia coli↗
PubMed2006

International Union of Pharmacology. LXVI. Orphan nuclear receptors.

Half of the members of the nuclear receptors superfamily are so-called "orphan" receptors because the identity of their ligand, if any, is unknown. Because of their important biological roles, the study of orphan receptors has attracted much attention recently and has resulted in rapid advances that have helped in the discovery of novel signaling pathways. In this review we present the main features of orphan receptors, discuss the structure of their ligand-binding domains and their biological functions. The paradoxical existence of a pharmacology of orphan receptors, a rapidly growing and innovative field, is highlighted.

Animals↗
PubMed1997

Utilization of chemokine receptors, orphan receptors, and herpesvirus-encoded receptors by diverse human and simian immunodeficiency viruses.

Human immunodeficiency virus type 1 (HIV-1) requires both CD4 and a coreceptor to infect cells. Macrophage-tropic (M-tropic) HIV-1 strains utilize the chemokine receptor CCR5 in conjunction with CD4 to infect cells, while T-cell-tropic (T-tropic) strains generally utilize CXCR4 as a coreceptor. Some viruses can use both CCR5 and CXCR4 for virus entry (i.e., are dual-tropic), while other chemokine receptors can be used by a subset of virus strains. Due to the genetic diversity of HIV-1, HIV-2, and simian immunodeficiency virus (SIV) and the potential for chemokine receptors other than CCR5 or CXCR4 to influence viral pathogenesis, we tested a panel of 28 HIV-1, HIV-2, and SIV envelope (Env) proteins for the ability to utilize chemokine receptors, orphan receptors, and herpesvirus-encoded chemokine receptor homologs by membrane fusion and virus infection assays. While all Env proteins used either CCR5 or CXCR4 or both, several also used CCR3. Use of CCR3 was strongly dependent on its surface expression levels, with a larger number of viral Env proteins being able to utilize this coreceptor at the higher levels of surface expression. ChemR1, an orphan receptor recently shown to bind the CC chemokine I309 (and therefore renamed CCR8), was expressed in monocyte and lymphocyte cell populations and functioned as a coreceptor for diverse HIV-1, HIV-2, and SIV Env proteins. Use of ChemR1/CCR8 by SIV strains was dependent in part on V3 loop sequences. The orphan receptor V28 supported Env-mediated cell-cell fusion by four T- or dual-tropic HIV-1 and HIV-2 strains. Three additional orphan receptors failed to function for any of the 28 Env proteins tested. Likewise, five of six seven-transmembrane-domain receptors encoded by herpesviruses did not support Env-mediated membrane fusion. However, the chemokine receptor US28, encoded by cytomegalovirus, did support inefficient infection by two HIV-1 strains. These findings indicate that additional chemokine receptors can function as HIV and SIV coreceptors and that surface expression levels can strongly influence coreceptor use.

Animals↗
PubMed2002

Spermatogenesis and testis development are normal in mice lacking testicular orphan nuclear receptor 2.

Early in vitro cell culture studies suggested that testicular orphan nuclear receptor 2 (TR2), a member of the nuclear receptor superfamily, may play important roles in the control of several pathways including retinoic acids, vitamin D, thyroid hormones, and ciliary neurotrophic factor. Here we report the surprising results showing that mice lacking TR2 are viable and have no serious developmental defects. Male mice lacking TR2 have functional testes, including normal sperm number and motility, and both male and female mice lacking TR2 are fertile. In heterozygous TR2(+/-) male mice we found that beta-galactosidase, the indicator of TR2 protein expression, was first detected at the age of 3 weeks and its expression pattern was restricted mainly in the spermatocytes and round spermatids. These protein expression patterns were further confirmed with Northern blot analysis of TR2 mRNA expression. Together, results from TR2-knockout mice suggest that TR2 may not play essential roles in spermatogenesis and normal testis development, function, and maintenance. Alternatively, the roles of TR2 may be redundant and could be played by other close members of the nuclear receptor superfamily such as testicular orphan receptor 4 (TR4) or unidentified orphan receptors that share many similar functions with TR2. Further studies with double knockouts of both orphan nuclear receptors, TR2 and TR4, may reveal their real physiological roles.

Animals↗
PubMed2004

Coordinating the norms and values of medical research, medical practice and patient worlds-the ethics of evidence based medicine in orphaned fields of medicine.

Evidence based medicine is rightly at the core of current medicine. If patients and society put trust in medical professional competency, and on the basis of that competency delegate all kinds of responsibilities to the medical profession, medical professionals had better make sure their competency is state of the art medical science. What goes for the ethics of clinical trials goes for the ethics of medicine as a whole: anything that is scientifically doubtful is, other things being equal, ethically unacceptable. This particularly applies to so called orphaned fields of medicine, those areas where medical research is weak and diverse, where financial incentives are lacking, and where the evidence regarding the aetiology and treatment of disease is much less clear than in laboratory and hospital based medicine. Examples of such orphaned fields are physiotherapy, psychotherapy, medical psychology, and occupational health, which investigate complex syndromes such as RSI, whiplash, chronic low back pain, and chronic fatigue syndrome. It appears that the primary ethical problem in this context is the lack of attention to the orphaned fields. Although we agree that this issue deserves more attention as a matter of potential injustice, we want to argue that, in order to do justice to the interplay of heterogeneous factors that is so typical of the orphaned fields, other ethical models than justice are required. We propose the coordination model as a window through which to view the important ethical issues which relate to the communication and interaction of scientists, health care workers, and patients.

Allied Health Occupations↗
PubMed2002

Discovery of recently adopted orphan receptors for apelin, urotensin II, and ghrelin identified using novel radioligands and functional role in the human cardiovascular system.

Using novel synthetic radioligands, we have discovered receptors for the recently paired apelin (APJ orphan receptor), ghrelin (GHS orphan receptor), and urotensin II (orphan GPR14) in the human cardiovascular system and determined their anatomical localisation. In addition, we have established functional vasoactive properties for these three peptides as potential vasoconstrictor/vasodilator mediators and provided evidence for alteration of receptor density in cardiovascular disease. We find that receptors for apelin, ghrelin, and urotensin II are widely distributed in human cardiovascular tissue, suggesting perhaps vasoactive roles for these peptides in human vascular physiology and a potential role in pathophysiology. Apelin and urotensin II are potent vasoconstrictors with low efficacy, consistent with their low receptor density. Ghrelin receptor density was increased (approximately three- to fourfold) with atherosclerosis of coronary artery disease and accelerated atherosclerosis of saphenous vein grafts, compared with normal vessels, highlighting a potentially beneficial role for this novel vasodilator peptide in human vascular disease. Our approach has demonstrated one successful strategy for translating genetic information encoding recently paired orphan receptor ligands into discovery of function. This study has the advantage of focussing on the actual disease processes, which allow the more precise identification of novel therapeutic targets.

Amino Acid Sequence↗
PubMed2006

Orphan nuclear receptors: therapeutic opportunities in skeletal muscle.

Nuclear hormone receptors (NRs) are ligand-dependent transcription factors that bind DNA and translate physiological signals into gene regulation. The therapeutic utility of NRs is underscored by the diversity of drugs created to manage dysfunctional hormone signaling in the context of reproductive biology, inflammation, dermatology, cancer, and metabolic disease. For example, drugs that target nuclear receptors generate over $10 billion in annual sales. Almost two decades ago, gene products were identified that belonged to the NR superfamily on the basis of DNA and protein sequence identity. However, the endogenous and synthetic small molecules that modulate their action were not known, and they were denoted orphan NRs. Many of the remaining orphan NRs are highly enriched in energy-demanding major mass tissues, including skeletal muscle, brown and white adipose, brain, liver, and kidney. This review focuses on recently adopted and orphan NR function in skeletal muscle, a tissue that accounts for approximately 35% of the total body mass and energy expenditure, and is a major site of fatty acid and glucose utilization. Moreover, this lean tissue is involved in cholesterol efflux and secretes that control energy expenditure and adiposity. Consequently, muscle has a significant role in insulin sensitivity, the blood lipid profile, and energy balance. Accordingly, skeletal muscle plays a considerable role in the progression of dyslipidemia, diabetes, and obesity. These are risk factors for cardiovascular disease, which is the the foremost cause of global mortality (>16.7 million deaths in 2003). Therefore, it is not surprising that orphan NRs and skeletal muscle are emerging as therapeutic candidates in the battle against dyslipidemia, diabetes, obesity, and cardiovascular disease.

Animals↗
PubMed1999

Diagnostic orphans: adolescents with alcohol symptom who do not qualify for DSM-IV abuse or dependence diagnoses.

OBJECTIVE: Little is known about the validity of the DSM-IV criteria for alcohol use disorders when applied to adolescents. This report describes a group of "diagnostic orphans," adolescents with one or two DSM-IV alcohol dependence symptoms who do not meet the DSM-IV criteria for alcohol abuse or alcohol dependence. METHOD: The study included 199 male and 173 female subjects aged 13-19 years. All subjects were regular drinkers, recruited from community sources and alcohol treatment programs. At baseline and at 1-year follow-up, DSM-IV alcohol use disorders were assessed with a version of the Structured Clinical Interview for DSM-III-R, modified for DSM-IV criteria. RESULTS: Diagnostic orphans represented 31% of the drinkers without an alcohol use disorder. The orphans were similar to the alcohol abusers and dissimilar to the other drinkers in alcohol and substance use patterns and in the course of alcohol problems over 1 year. CONCLUSIONS: The results indicate limitations of the DSM-IV criteria for alcohol use disorders when applied to adolescents. Diagnostic orphans should be considered separately from other drinkers in research and treatment efforts.

Adolescent↗
PubMed1977

Vietnamese and Cambodian orphans 1975--the first look. The initial medical screening and treatment at Clark Air Force Base.

In April of 1975, the United States government evacuated approximately 2,000 orphans from Vietnam and Cambodia. More than 1,500 orphans received initial medical evaluation and treatment at Clark Air Force Base, Republic of the Phillipines. The orphans underwent a minimum of 2 physician evaluations and were individually cared for by a volunteer. One hundred and six children were ill enough to require acute admission to the hospital. Four infants died while at Clark. No unusual tropical illnesses were diagnosed at Clark nor were any diseases identified that might represent a significant health hazard to the United States. The medical conditions found among these orphans appear to be similar to the problems found among the children of migrant farm workers in the United States.

Cambodia↗
PubMed2006

The psychological well-being of children orphaned by AIDS in Cape Town, South Africa.

BACKGROUND: An estimated 2 million children are parentally bereaved by AIDS in South Africa. Little is known about mental health outcomes for this group. METHODS: This study aimed to investigate mental health outcomes for urban children living in deprived settlements in Cape Town. 30 orphaned children and 30 matched controls were compared using standardised questionnaires (SDQ) on emotional and behavioural problems, peer and attention difficulties, and prosocial behaviour. The orphan group completed a modified version of a standardised questionnaire (IES-8), measuring Post-Traumatic Stress symptoms. Group differences were tested using t-tests and Pearson's chi-square. RESULTS: Both groups scored highly for peer problems, emotional problems and total scores. However, orphans were more likely to view themselves as having no good friends (p = .002), to have marked concentration difficulties (p = .03), and to report frequent somatic symptoms (p = .05), but were less likely to display anger through loss of temper (p = .03). Orphans were more likely to have constant nightmares (p = .01), and 73% scored above the cut-off for Post-Traumatic Stress Disorder. CONCLUSION: Findings suggest important areas for larger-scale research for parentally-bereaved children.

Journal Article↗
PubMed2002

Phylogenetic analysis of 277 human G-protein-coupled receptors as a tool for the prediction of orphan receptor ligands.

BACKGROUND: G-protein-coupled receptors (GPCRs) are the largest and most diverse family of transmembrane receptors. They respond to a wide range of stimuli, including small peptides, lipid analogs, amino-acid derivatives, and sensory stimuli such as light, taste and odor, and transmit signals to the interior of the cell through interaction with heterotrimeric G proteins. A large number of putative GPCRs have no identified natural ligand. We hypothesized that a more complete knowledge of the phylogenetic relationship of these orphan receptors to receptors with known ligands could facilitate ligand identification, as related receptors often have ligands with similar structural features. RESULTS: A database search excluding olfactory and gustatory receptors was used to compile a list of accession numbers and synonyms of 81 orphan and 196 human GPCRs with known ligands. Of these, 241 sequences belonging to the rhodopsin receptor-like family A were aligned and a tentative phylogenetic tree constructed by neighbor joining. This tree and local alignment tools were used to define 19 subgroups of family A small enough for more accurate maximum-likelihood analyses. The secretin receptor-like family B and metabotropic glutamate receptor-like family C were directly subjected to these methods. CONCLUSIONS: Our trees show the overall relationship of 277 GPCRs with emphasis on orphan receptors. Support values are given for each branch. This approach may prove valuable for identification of the natural ligands of orphan receptors as their relation to receptors with known ligands becomes more evident.

Amino Acid Sequence↗