Current approaches to inhibit nuclear receptor (NR) activity target the hormone binding pocket but face limitations. We have proposed that inhibitors, which bind to nuclear receptor surfaces that ...mediate assembly of the receptor's binding partners, might overcome some of these limitations. The androgen receptor (AR) plays a central role in prostate cancer, but conventional inhibitors lose effectiveness as cancer treatments because anti-androgen resistance usually develops. We conducted functional and x-ray screens to identify compounds that bind the AR surface and block binding of coactivators for AR activation function 2 (AF-2). Four compounds that block coactivator binding in solution with IC₅₀ almost equal to 50 μM and inhibit AF-2 activity in cells were detected: three nonsteroidal antiinflammatory drugs and the thyroid hormone 3,3',5-triiodothyroacetic acid. Although visualization of compounds at the AR surface reveals weak binding at AF-2, the most potent inhibitors bind preferentially to a previously unknown regulatory surface cleft termed binding function (BF)-3, which is a known target for mutations in prostate cancer and androgen insensitivity syndrome. X-ray structural analysis reveals that 3,3',5-triiodothyroacetic acid binding to BF-3 remodels the adjacent interaction site AF-2 to weaken coactivator binding. Mutation of residues that form BF-3 inhibits AR function and AR AF-2 activity. We propose that BF-3 is a previously unrecognized allosteric regulatory site needed for AR activity in vivo and a possible pharmaceutical target.
Sirtuin 1 (SIRT1) NAD(+)-dependent deacetylase regulates energy metabolism by modulating expression of genes involved in gluconeogenesis and other liver fasting responses. While many effects of SIRT1 ...on gene expression are mediated by deacetylation and activation of peroxisome proliferator activated receptor coactivator α (PGC-1α), SIRT1 also binds directly to DNA bound transcription factors, including nuclear receptors (NRs), to modulate their activity. Since thyroid hormone receptor β1 (TRβ1) regulates several SIRT1 target genes in liver and interacts with PGC-1α, we hypothesized that SIRT1 may influence TRβ1. Here, we confirm that SIRT1 cooperates with PGC-1α to enhance response to triiodothyronine, T3. We also find, however, that SIRT1 stimulates TRβ1 activity in a manner that is independent of PGC-1α but requires SIRT1 deacetylase activity. SIRT1 interacts with TRβ1 in vitro, promotes TRβ1 deacetylation in the presence of T3 and enhances ubiquitin-dependent TRβ1 turnover; a common response of NRs to activating ligands. More surprisingly, SIRT1 knockdown only strongly inhibits T3 response of a subset of TRβ1 target genes, including glucose 6 phosphatase (G-6-Pc), and this is associated with blockade of TRβ1 binding to the G-6-Pc promoter. Drugs that target the SIRT1 pathway, resveratrol and nicotinamide, modulate T3 response at dual TRβ1/SIRT1 target genes. We propose that SIRT1 is a gene-specific TRβ1 co-regulator and TRβ1/SIRT1 interactions could play important roles in regulation of liver metabolic response. Our results open possibilities for modulation of subsets of TR target genes with drugs that influence the SIRT1 pathway.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The crystal structure of a previously reported screening hit 1 (CCT018159) bound to the N terminal domain of molecular chaperone Hsp90 has been used to design 5-amide analogues. These exhibit ...enhanced potency against the target in binding and functional assays with accompanying appropriate cellular pharmacodynamic changes. Compound 11 (VER-49009) compares favorably with the clinically evaluated 17-AAG.
Inhibitors of the Hsp90 molecular chaperone are showing considerable promise as potential molecular therapeutic agents for the treatment of cancer. Here we describe novel 2-aminothieno2,3-dpyrimidine ...ATP competitive Hsp90 inhibitors, which were designed by combining structural elements of distinct low affinity hits generated from fragment-based and in silico screening exercises in concert with structural information from X-ray protein crystallography. Examples from this series have high affinity (IC50 = 50−100 nM) for Hsp90 as measured in a fluorescence polarization (FP) competitive binding assay and are active in human cancer cell lines where they inhibit cell proliferation and exhibit a characteristic profile of depletion of oncogenic proteins and concomitant elevation of Hsp72. Several examples (34a, 34d and 34i) caused tumor growth regression at well tolerated doses when administered orally in a human BT474 human breast cancer xenograft model.
In capital breeders, individual differences in body size and condition can impact mating effort and success. In addition to the collateral advantages of large body size in competition, large nutrient ...reserves may offer advantages in endurance rivalry and enable the high rates of energy expenditure associated with mating success. We examined the impacts of body reserves and dominance rank on energy expenditure, water flux, mating success, and breeding tenure in the adult male northern elephant seal, a polygynous, capital breeder. Adult males expended energy at a rate of
MJ d−1, which is equivalent to 3.1 times the standard metabolic rate predicted by Kleiber’s equation. Despite high rates of energy expenditure and a long fasting duration, males spared lean tissue effectively, deriving a mean of 7% of their metabolism from protein catabolism. Body composition had a strong impact on the ability to spare lean tissue during breeding. When controlling for body size, energy expenditure, depletion of blubber reserves, and water efflux were significantly greater in alpha males than in subordinate males. Large body size was associated with increased reproductive effort, tenure on shore, dominance rank, and reproductive success. Terrestrial locomotion and topography appeared to strongly influence energy expenditure. Comparisons with conspecific females suggest greater total seasonal reproductive effort in male northern elephant seals when controlling for the effects of body mass. In polygynous capital breeding systems, male effort may be strongly influenced by physiological state and exceed that of females.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NMLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The facile insertion of CO2 into iridium(I) hydroxide, alkoxide, and amide bonds was recently reported. In particular, Ir(cod)(IiPr)(OH) (IiPr=1,3‐bis(isopropyl)imidazol‐2‐ylidene) reacted with CO2 ...in solution and in the solid state in a matter of minutes to give the novel {Ir(cod)(IiPr)}2(μ‐κ1O:κ2O,O‐CO3) complex. In the present study, this reaction is probed using kinetics and theoretical studies, which enabled us to analyse its facile nature and to fully elucidate the reaction mechanism with excellent correlation between the two methods.
The insertion of CO2 into iridium(I) hydroxide and alkoxide bonds is examined from both a kinetics and thermodynamic perspective. The two methods showed excellent correlation, shedding much needed light on the mechanism of CO2 fixation by IrI complexes.
Biological processes require close cooperation of multiple transcription factors that integrate different signals. Thyroid hormone receptors (TRs) induce Krüppel‐like factor 9 (KLF9) to regulate ...neurogenesis. Here, we show that triiodothyronine (T3) also works through TR to induce KLF9 in HepG2 liver cells, mouse liver, and mouse and human primary hepatocytes and sought to understand TR/KLF9 network function in the hepatocyte lineage and stem cells. Knockdown experiments reveal that KLF9 regulates hundreds of HepG2 target genes and modulates T3 response. Together, T3 and KLF9 target genes influence pathways implicated in stem cell self‐renewal and differentiation, including Notch signaling, and we verify that T3 and KLF9 cooperate to regulate key Notch pathway genes and work independently to regulate others. T3 also induces KLF9 in human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSC) and this effect persists during differentiation to definitive endoderm and hiPSC‐derived hepatocytes. Microarray analysis reveals that T3 regulates hundreds of hESC and hiPSC target genes that cluster into many of the same pathways implicated in TR and KLF9 regulation in HepG2 cells. KLF9 knockdown confirms that TR and KLF9 cooperate to regulate Notch pathway genes in hESC and hiPSC, albeit in a partly cell‐specific manner. Broader analysis of T3 responsive hESC/hiPSC genes suggests that TRs regulate multiple early steps in ESC differentiation. We propose that TRs cooperate with KLF9 to regulate hepatocyte proliferation and differentiation and early stages of organogenesis and that TRs exert widespread and important influences on ESC biology. Stem Cells 2015;33:416–428
Dry‐reforming catalysts were prepared by supporting Ni nanoparticles (2–3 nm) on La‐doped silica. These materials display higher activity and stability in low‐temperature dry reforming (773 K) than ...Ni/SiO2 or Ni/La2O3. The La‐doped silica‐supported catalysts were found to have exclusively lanthanum silicate at their surface rather than La2O3 and/or SiO2. While an increasing amount of La was found to favor both CO2 adsorption capacity and strength, it also influenced the hydrogen adsorption strength on nickel particles significantly, as evidenced by H2 temperature‐programmed desorption analysis. Finally, CH4 temperature‐programmed reduction analysis revealed that the CH4 cracking threshold temperature varies in the order: Nibulk<Ni/La34@SiO2<Ni/La2.1@SiO2≪Ni/SiO2<Ni/La2O3, which parallels the catalytic performance. Balancing the adsorption of CH4, H2, and CO2 on supported Ni nanoparticles (2–3 nm) on La‐doped silica improves the catalytic performance of this low‐temperature dry‐reforming catalyst.
A pinch of lanthanum makes a stable support: Doping silica with lanthanum ions significantly enhances the steady‐state activity and stability of supported nickel nanoparticles in dry reforming at 500 °C. Surface lanthanum silicates increase CO2 and H2 adsorption strength and lower the temperature of methane activation on nickel.
Upregulation of estrogen receptor beta (ERβ) in breast cancer cells is associated with epithelial maintenance, decreased proliferation and invasion, and a reduction in the expression of the receptor ...has been observed in invasive breast tumors. However, proof of an association between loss of ERβ and breast carcinogenesis is still missing.
To study the role of ERβ in breast oncogenesis, we generated mouse conditional mutants with specific inactivation of ERβ and p53 in the mammary gland epithelium. For epithelium-specific knockout of ERβ and p53, ERβ
and p53
mice were crossed to transgenic mice that express the Cre recombinase under the control of the human keratin 14 promoter.
Somatic loss of ERβ significantly accelerated formation of p53-deficient mammary tumors. Loss of the receptor also resulted in the development of less differentiated carcinomas with stronger spindle cell morphology and decreased expression of luminal epithelial markers.
Our results show that synergism between ERβ and p53 inactivation functions to determine important aspects of breast oncogenesis and cancer progression.
We report the three-dimensional structure of a β-catenin armadillo repeat in complex with the liver receptor homolog-1 (LRH-1) ligand binding domain at 2.8 Å resolution as the first structure of ...β-catenin in complex with any nuclear receptor. The surface of β-catenin that binds LRH-1 partly overlaps defined contact sites for peptide segments of β-catenin partners, including T-cell factor-4. The surface of LRH-1 that engages β-catenin is comprised of helices 1, 9, and 10 and is distinct from known interaction surfaces of LRH-1, including corepressor and coactivator binding sites. Targeted mutagenesis of amino acids forming both sides of the LRH-1/β-catenin interface reveals that they are essential for stable interactions between these proteins in solution. The LRH-1 binding site in β-catenin is also required for association with androgen receptor, providing evidence that the observed LRH-1/β-catenin interaction may be prototypic.
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