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1.
Australas J Ultrasound Med ; 27(2): 124-130, 2024 May.
Article in English | MEDLINE | ID: mdl-38784694

ABSTRACT

Introduction: Sternal pseudotumour is an important but rare entity thought to be an inflammatory, non-neoplastic lesion that can mimic tumours. The purpose of this paper was to illustrate the imaging features of this lesion to avoid unnecessary investigations. Methods: The clinical notes and imaging features of four patients with a diagnosis of sternal pseudotumour were reviewed over a period from February 2016 to July 2019. Results: All patients were afebrile with no history of trauma. The median age at presentation was 12.5 months. The median length of symptoms prior to presentation was 3.5 days. One patient had a mildly elevated C-reactive protein. Chest radiographs showed a pre-sternal soft-tissue mass, with or without osseous destruction of the subjacent sternum. Ultrasound showed a heterogeneous, hypoechoic pre-sternal soft-tissue mass with variable internal vascularity with extension between sternal ossification centres. CT and MRI showed an enhancing dumbbell-shaped lesion with a pre-sternal and retro-sternal soft-tissue component. The median time to complete resolution was 3 months. One patient had a biopsy that showed chronic inflammation and fibrosis. Discussion: These lesions present in young children typically with a 1- to 2-week history of a focal 2- to 4-cm swelling over the sternum. The aetiology is unknown but may be on the basis of a yet-to-be identified pathogen. Inflammatory markers and cultures are normal or mildly elevated. Important differential considerations include sternal osteomyelitis or neoplastic causes such as Ewing sarcoma, rhabdomyosarcoma, Langerhans cell histiocytosis and infantile fibrosarcoma. Conclusion: Sternal pseudotumor is a rare but important entity to be aware of to avoid unnecessary invasive biopsy or further investigations. Our suggestion is that this is a 'Don't touch' lesion that requires close short-interval follow-up at a surgical outpatient clinic and with ultrasound until resolution.

3.
Mol Cancer Res ; 19(11): 1795-1801, 2021 11.
Article in English | MEDLINE | ID: mdl-34465585

ABSTRACT

Ewing sarcoma is a pediatric bone cancer defined by a chromosomal translocation fusing one of the FET family members to an ETS transcription factor. There have been seven reported chromosomal translocations, with the most recent reported over a decade ago. We now report a novel FET/ETS translocation involving FUS and ETV4 detected in a patient with Ewing sarcoma. Here, we characterized FUS/ETV4 by performing genomic localization and transcriptional regulatory studies on numerous FET/ETS fusions in a Ewing sarcoma cellular model. Through this comparative analysis, we demonstrate significant similarities across these fusions, and in doing so, validate FUS/ETV4 as a bona fide Ewing sarcoma translocation. This study presents the first genomic comparison of Ewing sarcoma-associated translocations and reveals that the FET/ETS fusions share highly similar, but not identical, genomic localization and transcriptional regulation patterns. These data strengthen the notion that FET/ETS fusions are key drivers of, and thus pathognomonic for, Ewing sarcoma. IMPLICATIONS: Identification and initial characterization of the novel Ewing sarcoma fusion, FUS/ETV4, expands the family of Ewing fusions and extends the diagnostic possibilities for this aggressive tumor of adolescents and young adults.


Subject(s)
Proto-Oncogene Proteins c-ets/metabolism , RNA-Binding Protein FUS/metabolism , Sarcoma, Ewing/genetics , Translocation, Genetic/genetics , Humans , Infant, Newborn , Oncogene Proteins, Fusion/genetics , Sarcoma, Ewing/pathology
4.
Vaccine ; 37(25): 3326-3334, 2019 05 31.
Article in English | MEDLINE | ID: mdl-31079849

ABSTRACT

BACKGROUND: We evaluated safety and immunogenicity of the first mRNA vaccines against potentially pandemic avian H10N8 and H7N9 influenza viruses. METHODS: Two randomized, placebo-controlled, double-blind, phase 1 clinical trials enrolled participants between December 2015 and August 2017 at single centers in Germany (H10N8) and USA (H7N9). Healthy adults (ages 18-64 years for H10N8 study; 18-49 years for H7N9 study) participated. Participants received vaccine or placebo in a 2-dose vaccination series 3 weeks apart. H10N8 intramuscular (IM) dose levels of 25, 50, 75, 100, and 400 µg and intradermal dose levels of 25 and 50 µg were evaluated. H7N9 IM 10-, 25-, and 50-µg dose levels were evaluated; 2-dose series 6 months apart was also evaluated. Primary endpoints were safety (adverse events) and tolerability. Secondary immunogenicity outcomes included humoral (hemagglutination inhibition [HAI], microneutralization [MN] assays) and cell-mediated responses (ELISPOT assay). RESULTS: H10N8 and H7N9 mRNA IM vaccines demonstrated favorable safety and reactogenicity profiles. No vaccine-related serious adverse event was reported. For H10N8 (N = 201), 100-µg IM dose induced HAI titers ≥ 1:40 in 100% and MN titers ≥ 1:20 in 87.0% of participants. The 25-µg intradermal dose induced HAI titers > 1:40 in 64.7% of participants compared to 34.5% of participants receiving the IM dose. For H7N9 (N = 156), IM doses of 10, 25, and 50 µg achieved HAI titers ≥ 1:40 in 36.0%, 96.3%, and 89.7% of participants, respectively. MN titers ≥ 1:20 were achieved by 100% in the 10- and 25-µg groups and 96.6% in the 50-µg group. Seroconversion rates were 78.3% (HAI) and 87.0% (MN) for H10N8 (100 µg IM) and 96.3% (HAI) and 100% (MN) in H7N9 (50 µg). Significant cell-mediated responses were not detected in either study. CONCLUSIONS: The first mRNA vaccines against H10N8 and H7N9 influenza viruses were well tolerated and elicited robust humoral immune responses. ClinicalTrials.gov NCT03076385 and NCT03345043.


Subject(s)
Immunogenicity, Vaccine , Influenza Vaccines/genetics , Influenza Vaccines/immunology , Influenza, Human/prevention & control , RNA, Viral/immunology , Adolescent , Adult , Antibodies, Viral/blood , Dose-Response Relationship, Drug , Double-Blind Method , Female , Healthy Volunteers , Humans , Influenza A Virus, H10N8 Subtype , Influenza A Virus, H7N9 Subtype , Influenza Vaccines/adverse effects , Male , Middle Aged , RNA, Viral/administration & dosage , Young Adult
5.
Mol Ther ; 25(6): 1316-1327, 2017 06 07.
Article in English | MEDLINE | ID: mdl-28457665

ABSTRACT

Recently, the World Health Organization confirmed 120 new human cases of avian H7N9 influenza in China resulting in 37 deaths, highlighting the concern for a potential pandemic and the need for an effective, safe, and high-speed vaccine production platform. Production speed and scale of mRNA-based vaccines make them ideally suited to impede potential pandemic threats. Here we show that lipid nanoparticle (LNP)-formulated, modified mRNA vaccines, encoding hemagglutinin (HA) proteins of H10N8 (A/Jiangxi-Donghu/346/2013) or H7N9 (A/Anhui/1/2013), generated rapid and robust immune responses in mice, ferrets, and nonhuman primates, as measured by hemagglutination inhibition (HAI) and microneutralization (MN) assays. A single dose of H7N9 mRNA protected mice from a lethal challenge and reduced lung viral titers in ferrets. Interim results from a first-in-human, escalating-dose, phase 1 H10N8 study show very high seroconversion rates, demonstrating robust prophylactic immunity in humans. Adverse events (AEs) were mild or moderate with only a few severe and no serious events. These data show that LNP-formulated, modified mRNA vaccines can induce protective immunogenicity with acceptable tolerability profiles.


Subject(s)
Influenza A Virus, H10N8 Subtype/genetics , Influenza A Virus, H10N8 Subtype/immunology , Influenza A Virus, H7N9 Subtype/genetics , Influenza A Virus, H7N9 Subtype/immunology , Influenza Vaccines/immunology , Orthomyxoviridae Infections/prevention & control , RNA, Messenger/genetics , Animals , Antibodies, Viral/blood , Antibodies, Viral/immunology , Cell Line , Disease Models, Animal , Female , Ferrets , Gene Expression , Humans , Immunization , Immunization Schedule , Influenza Vaccines/administration & dosage , Influenza Vaccines/adverse effects , Macaca fascicularis , Male , Mice , Protamines , RNA, Messenger/administration & dosage , RNA, Messenger/pharmacokinetics , RNA, Viral , Tissue Distribution
6.
Emerg Med Australas ; 29(2): 198-203, 2017 Apr.
Article in English | MEDLINE | ID: mdl-28332328

ABSTRACT

OBJECTIVE: The objective was to examine the safety and efficacy of high-flow nasal cannula (HFNC) therapy for children with bronchiolitis in a non-tertiary paediatric setting. METHODS: This was a single-centre retrospective study conducted over 26 months (March 2013-April 2015) on children aged 1-23 months with suspected bronchiolitis, who commenced on HFNC therapy in either the ED or the ward. Changes with respect to baseline data were analysed for effect on work of breathing (WOB), heart rate (HR) and respiratory rate (RR). Data was analysed using a linear mixed effects model and adjusted for age (≤12 months and >12 months) and location (ED vs ward). Transfer to a tertiary environment, escalation of care and adverse event rates were also recorded. RESULTS: A total of 61 children commenced on HFNC therapy, with flow rates ranging from 0.6 to 3.3L/kg/min. The proportion of patients with higher WOB scores appeared to reduce within 60 min of initiation of therapy. There was also a progressive reduction in surrogate markers of respiratory distress (HR and RR), with significant reductions evident by 60 min (P < 0.05). There were no adverse events related to HFNC therapy. The transfer rate was 13%. It was predominantly due to lack of improvement of physiological parameters post initiation of HFNC therapy. None of the transferred patients required escalation of care. CONCLUSION: Within the limitations of this study it appears HFNC therapy may be safely commenced in both age groups in a non-tertiary ED or ward, with an appropriate level of observation and robust transfer criteria.


Subject(s)
Cannula/statistics & numerical data , Patient Outcome Assessment , Patient Safety/statistics & numerical data , Pediatrics/methods , Treatment Outcome , Cohort Studies , Emergency Service, Hospital/organization & administration , Emergency Service, Hospital/statistics & numerical data , Female , Humans , Infant , Male , Oxygen Inhalation Therapy/methods , Oxygen Inhalation Therapy/statistics & numerical data , Patient Safety/standards , Pediatrics/standards , Pediatrics/statistics & numerical data , Retrospective Studies
7.
Science ; 355(6327): 817-819, 2017 02 24.
Article in English | MEDLINE | ID: mdl-28219970

ABSTRACT

Ultraluminous x-ray sources (ULXs) in nearby galaxies shine brighter than any x-ray source in our Galaxy. ULXs are usually modeled as stellar-mass black holes (BHs) accreting at very high rates or intermediate-mass BHs. We present observations showing that NGC 5907 ULX is instead an x-ray accreting neutron star (NS) with a spin period evolving from 1.43 seconds in 2003 to 1.13 seconds in 2014. It has an isotropic peak luminosity of [Formula: see text]1000 times the Eddington limit for a NS at 17.1 megaparsec. Standard accretion models fail to explain its luminosity, even assuming beamed emission, but a strong multipolar magnetic field can describe its properties. These findings suggest that other extreme ULXs (x-ray luminosity [Formula: see text] 1041 erg second[Formula: see text]) might harbor NSs.

10.
Ophthalmic Genet ; 34(4): 238-42, 2013 Dec.
Article in English | MEDLINE | ID: mdl-23289805

ABSTRACT

BACKGROUND: Retinoblastoma (RB) is the most common primary childhood intraocular malignancy and usually presents before the age of 4 years. RB in late childhood is rare and may pose a diagnostic challenge to clinicians. MATERIALS AND METHODS: Patients over the age of 4 years with RB were identified retrospectively. Clinical data, histological findings, and molecular genetic diagnoses were obtained. RESULTS: Two cases of late onset RB were identified. Case 1 was a 10-year-old boy who presented with floaters, and was found to have a unilateral exudative retinal detachment and RB on clinical examination. Genetic testing showed a novel homozygous mutation in exon 20 of the RB1 gene in the tumor sample, c.2027_2034dup, resulting in p.Ile679X. No mutation was found in the DNA obtained from the peripheral blood sample. Case 2 was a 6-year-old boy who presented with loss of vision and pain in the left eye. RB was diagnosed on clinical examination with exudative retinal detachment. Genetic testing showed no mutation in the RB1 gene, but complete methylation of the RB1 promoter region. CONCLUSIONS: RB can rarely present in late childhood. Clinicians should consider RB as a diagnosis when faced with a patient with unexplained exudative retinal detachment.


Subject(s)
Genes, Retinoblastoma , Mutation , Retinal Neoplasms/genetics , Retinoblastoma Protein/genetics , Retinoblastoma/genetics , Antineoplastic Agents/therapeutic use , Child , DNA Methylation , DNA Mutational Analysis , Diagnosis, Differential , Exons/genetics , Humans , Magnetic Resonance Imaging , Male , Molecular Diagnostic Techniques , Polymerase Chain Reaction , Retinal Detachment/diagnosis , Retinal Neoplasms/diagnosis , Retinal Neoplasms/drug therapy , Retinoblastoma/diagnosis , Retinoblastoma/drug therapy , Retrospective Studies , Sequence Analysis, DNA , Visual Acuity
11.
J Infect Dis ; 203(1): 75-84, 2011 Jan 01.
Article in English | MEDLINE | ID: mdl-21148499

ABSTRACT

BACKGROUND: ChimeriVax-WN02 is a live, attenuated chimeric vaccine for protection against West Nile virus. This Phase II, randomized, double-blind, placebo-controlled, multicenter study assessed the immunogenicity, viremia, and safety of the ChimeriVax-WN02 vaccine. METHODS: The 2-part study included adults in general good health. In part 1, subjects aged 18-40 years were randomized to 1 of 4 treatment groups: ChimeriVax-WN02 3.7- × -10(5) plaque-forming units (PFU), 3.7 × 10(4) PFU, 3.7 × 10(3) PFU, or placebo. In part 2, subjects aged 41-64 and ≥ 65 years were randomized to receive ChimeriVax-WN02 3.7 × 10(5) PFU or placebo. RESULTS: In both part 1 and part 2, seroconversion was achieved at day 28 by >96% of subjects in active treatment groups. In part 1, neutralizing antibody titers at day 28 were higher and viremia levels lower with the highest dose, whereas the adverse event profile was similar between the dose groups. In part 2, antibody titers and viremia levels were higher in subjects aged ≥ 65 years, and more subjects in the 41-64 years cohort experienced adverse events. CONCLUSIONS: The ChimeriVax-WN02 vaccine was highly immunogenic in younger adults and the elderly, and it was well tolerated at all dose levels and in all age groups investigated. Clinical Trials.gov identifier: NCT00442169.


Subject(s)
West Nile Virus Vaccines/adverse effects , West Nile Virus Vaccines/immunology , Adolescent , Adult , Aged , Antibodies, Neutralizing/blood , Antibodies, Viral/blood , Double-Blind Method , Female , Human Experimentation , Humans , Male , Middle Aged , Placebos/administration & dosage , Vaccines, Attenuated/adverse effects , Vaccines, Attenuated/immunology , Viremia , Young Adult
12.
J Med Chem ; 51(18): 5758-65, 2008 Sep 25.
Article in English | MEDLINE | ID: mdl-18800767

ABSTRACT

A cocrystal structure of T1317 (3) bound to hLXRbeta was utilized in the design of a series of substituted N-phenyl tertiary amines. Profiling in binding and functional assays led to the identification of LXR modulator GSK9772 ( 20) as a high-affinity LXRbeta ligand (IC 50 = 30 nM) that shows separation of anti-inflammatory and lipogenic activities in human macrophage and liver cell lines, respectively. A cocrystal structure of the structurally related analog 19 bound to LXRbeta reveals regions within the receptor that can affect receptor modulation through ligand modification. Mechanistic studies demonstrate that 20 is greater than 10-fold selective for LXR-mediated transrepression of proinflammatory gene expression versus transactivation of lipogenic signaling pathways, thus providing an opportunity for the identification of LXR modulators with improved therapeutic indexes.


Subject(s)
Amines/chemistry , Amines/pharmacology , Anti-Inflammatory Agents/chemistry , Anti-Inflammatory Agents/pharmacology , DNA-Binding Proteins/drug effects , Drug Design , Receptors, Cytoplasmic and Nuclear/drug effects , Crystallography, X-Ray , Liver X Receptors , Magnetic Resonance Spectroscopy , Mass Spectrometry , Models, Molecular , Molecular Structure , Orphan Nuclear Receptors , Structure-Activity Relationship
13.
Comb Chem High Throughput Screen ; 10(4): 239-45, 2007 May.
Article in English | MEDLINE | ID: mdl-17506706

ABSTRACT

Efficient compound selection remains a key challenge in drug discovery today. The goal is to identify developable drug candidates early in the screening process while simultaneously flagging compounds with off-target effects indicative of liabilities or alternate indications. This goal overlaps but is distinct from the goal of toxicogenomics which is focused primarily on identifying toxicity signatures of lead candidates in key tissues. We propose a framework where global changes in gene expression levels in response to compounds can be used as an objective metric for early compound prioritization. We call this metric the Relative Transcription Index (RTI). RTI is a measure of the relative activity of compounds as ascertained by their effects on transcription at a genome-wide level. Compounds with a low RTI affect the expression of only a few genes whereas compounds with a high RTI affect the expression of a large number of genes. This information is useful for differentiating compounds that, based on phenotypic assays alone, may appear to be equally efficacious. Since compounds with high RTI are more likely to display off-target effects, the RTI metric, if implemented early in the screening process, can become a valuable tool for compound selection. The utility of the RTI metric is demonstrated by its application to two different gene expression datasets--one involving modulators of the liver X receptor (LXR) and the other concerning antibacterial compounds belonging to diverse mechanistic classes.


Subject(s)
Anti-Bacterial Agents/chemistry , DNA-Binding Proteins/genetics , Drug Evaluation, Preclinical/methods , Gene Expression , Receptors, Cytoplasmic and Nuclear/genetics , Transcription, Genetic , Algorithms , Anti-Bacterial Agents/pharmacology , Bacillus subtilis/drug effects , Bacillus subtilis/genetics , Bacillus subtilis/metabolism , Cell Line , DNA-Binding Proteins/drug effects , Databases, Genetic , Gene Expression/drug effects , Gene Expression Profiling , Humans , Liver X Receptors , Orphan Nuclear Receptors , Receptors, Cytoplasmic and Nuclear/drug effects , Transcription, Genetic/drug effects
14.
J Med Chem ; 48(17): 5419-22, 2005 Aug 25.
Article in English | MEDLINE | ID: mdl-16107141

ABSTRACT

Substituted 3-(phenylamino)-1H-pyrrole-2,5-diones were identified from a high throughput screen as inducers of human ATP binding cassette transporter A1 expression. Mechanism of action studies led to the identification of GSK3987 as an LXR ligand. GSK3987 recruits the steroid receptor coactivator-1 to human LXRalpha and LXRbeta with EC(50)s of 40 nM, profiles as an LXR agonist in functional assays, and activates LXR though a mechanism that is similar to first generation LXR agonists.


Subject(s)
Aniline Compounds/chemical synthesis , DNA-Binding Proteins/agonists , Maleimides/chemical synthesis , Receptors, Cytoplasmic and Nuclear/agonists , ATP Binding Cassette Transporter 1 , ATP-Binding Cassette Transporters/biosynthesis , ATP-Binding Cassette Transporters/genetics , Aniline Compounds/chemistry , Aniline Compounds/pharmacology , Binding Sites , Cell Line , Crystallography, X-Ray , DNA-Binding Proteins/chemistry , Genes, Reporter , Histone Acetyltransferases , Humans , Ligands , Liver X Receptors , Luciferases/genetics , Maleimides/chemistry , Maleimides/pharmacology , Models, Molecular , Molecular Structure , Monocytes/drug effects , Monocytes/metabolism , Nuclear Receptor Coactivator 1 , Orphan Nuclear Receptors , Promoter Regions, Genetic , Receptors, Cytoplasmic and Nuclear/chemistry , Structure-Activity Relationship , Transcription Factors/metabolism , Up-Regulation
15.
J Occup Environ Hyg ; 2(8): 400-5, 2005 Aug.
Article in English | MEDLINE | ID: mdl-16009648

ABSTRACT

This article presents results of asbestos air sampling conducted to assess the exposure to truck drivers working at the World Trade Center site. Sampling consisted of a combination of area and personal monitoring of 49 truck drivers and included optical and electron microscopic analyses. Three sampling periods were conducted: October 1-7, 2001, October 17-26, 2001, and April 13-23, 2002. Area sample locations were selected to estimate airborne concentrations around the perimeter of the site, on top of the pile, and in the pit. Air samples were collected using a 50-mm conductive cowl and a 25-mm mixed cellulose ester filter at flow rates ranging from 0.5-2 L/min. Samples were analyzed using a combination of phase contrast microscopy (PCM) NIOSH method 7400, transmission electron microscopy (TEM) NIOSH method 7402, and the direct method specified under the Asbestos Hazardous Emergency Response Act. Sample times and flow rates were adjusted to prevent overloading while maximizing sample volume. Personal sampling results suggest that asbestos fiber exposures to truck drivers at the site were low. Exposures based on TEM results generally ranged from less than detectable to 0.1 structures per cubic centimeter (s/cm(3)). TEM-based results further indicate that the majority of asbestos fibers were chrysotile and less than 5 microm in length. PCM-based estimates were generally higher than the TEM results. This is likely due to the counting of nonasbestos fibers. This conclusion is supported by the NIOSH 7402 TEM results, which did not detect asbestos fibers longer than 5 micro m. Area sample results were generally less than the personal results (except for the sample collected on top of the rubble pile) and decreased over the course of the cleanup. Our results show low airborne asbestos concentrations and a predominance of short fibers. Given these low concentrations, evidence of short fibers, and the short duration of the exposure (less than 10 months to complete the cleanup), it is likely that truck drivers working at the site are not at an increased risk for asbestos-related disease.


Subject(s)
Asbestos/analysis , Inhalation Exposure/analysis , Occupational Exposure/analysis , September 11 Terrorist Attacks , Environmental Monitoring/methods , Health Surveys , Humans , Motor Vehicles , New York City , Refuse Disposal , Threshold Limit Values
16.
BJU Int ; 95(1): 59-63, 2005 Jan.
Article in English | MEDLINE | ID: mdl-15638895

ABSTRACT

OBJECTIVE: To compare the costs of managing prostate and bladder cancer and relate them to current expenditure on research, as the increasing prevalence of both necessitates the adequate direction of resources. METHODS: All new prostate and bladder cancers diagnosed in 2001-2002 were identified from British Association of Urological Surgeons Section of Oncology database (national and local). The total cost of diagnosing, treating and following patients for 5 years was estimated as the sum of direct costs (National Health Service) and indirect costs (loss of earnings). Annual research fund allocation (RFA) for each cancer were obtained from the National Cancer Research Institute UK. RESULTS: There were 15 099 and 7703 patients with newly diagnosed prostate (mean age 72.3 years) and bladder cancers (mean age 71.3 years). The total cost for prostate cancer was estimated at 92.74 million UK pounds, with hormonal therapy alone costing 63.1 million UK pounds. The total cost for bladder cancer was 55.39 million UK pounds, of which superficial disease cost 35.25 million. The mean cost per patient was more for bladder than for prostate cancer (8349 UK pounds vs. 7294). The RFA allocation during this period was 20.56 million UK pounds and 4.62 million UK pounds for prostate and bladder cancer, respectively, and the respective RFA allotment per pound spent on the mean cost of disease management per patient was 2818 UK pounds and 553 UK pounds. CONCLUSION: Individual patient management is more costly for bladder cancer but less is invested in research than for prostate cancer. This study suggests a need to re-evaluate future strategies.


Subject(s)
Prostatic Neoplasms/economics , Urinary Bladder Neoplasms/economics , Adolescent , Adult , Aged , Biomedical Research/economics , Costs and Cost Analysis , Female , Health Expenditures , Humans , Income , Male , Middle Aged , Prostatic Neoplasms/epidemiology , Prostatic Neoplasms/surgery , Research Support as Topic , United Kingdom/epidemiology , Urinary Bladder Neoplasms/epidemiology , Urinary Bladder Neoplasms/surgery
17.
J Biol Chem ; 278(29): 27138-43, 2003 Jul 18.
Article in English | MEDLINE | ID: mdl-12736258

ABSTRACT

The x-ray crystal structures of the human liver X receptor beta ligand binding domain complexed to sterol and nonsterol agonists revealed a perpendicular histidinetryptophan switch that holds the receptor in its active conformation. Hydrogen bonding interactions with the ligand act to position the His-435 imidazole ring against the Trp-457 indole ring, allowing an electrostatic interaction that holds the AF2 helix in the active position. The neutral oxysterol 24(S),25-epoxycholesterol accepts a hydrogen bond from His-435 that positions the imidazole ring of the histidine above the pyrrole ring of the tryptophan. In contrast, the acidic T0901317 hydroxyl group makes a shorter hydrogen bond with His-435 that pulls the imidazole over the electron-rich benzene ring of the tryptophan, possibly strengthening the electrostatic interaction. Point mutagenesis of Trp-457 supports the observation that the ligand-histidine-tryptophan coupling is different between the two ligands. The lipophilic liver X receptor ligand-binding pocket is larger than the corresponding steroid hormone receptors, which allows T0901317 to adopt two distinct conformations. These results provide a molecular basis for liver X receptor activation by a wide range of endogenous neutral and acidic ligands.


Subject(s)
Cholesterol/analogs & derivatives , Receptors, Cytoplasmic and Nuclear/chemistry , Anticholesteremic Agents/chemistry , Anticholesteremic Agents/metabolism , Binding Sites , Cholesterol/chemistry , Cholesterol/metabolism , Crystallography, X-Ray , DNA-Binding Proteins , Histidine/chemistry , Humans , Hydrocarbons, Fluorinated , Hydrogen Bonding , In Vitro Techniques , Ligands , Liver/metabolism , Liver X Receptors , Models, Molecular , Mutagenesis, Site-Directed , Orphan Nuclear Receptors , Protein Conformation , Protein Structure, Tertiary , Receptors, Cytoplasmic and Nuclear/genetics , Receptors, Cytoplasmic and Nuclear/metabolism , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , Sulfonamides , Tryptophan/chemistry
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