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BACKGROUND & AIMS: Mitochondrial dysfunction disrupts the synthesis and secretion of digestive enzymes in pancreatic acinar cells and plays a primary role in the etiology of exocrine pancreas disorders. However, the transcriptional mechanisms that regulate mitochondrial function to support acinar cell physiology are poorly understood. Here, we aim to elucidate the function of estrogen-related receptor γ (ERRγ) in pancreatic acinar cell mitochondrial homeostasis and energy production. METHODS: Two models of ERRγ inhibition, GSK5182-treated wild-type mice and ERRγ conditional knock-out (cKO) mice, were established to investigate ERRγ function in the exocrine pancreas. To identify the functional role of ERRγ in pancreatic acinar cells, we performed histological and transcriptome analysis with the pancreas isolated from ERRγ cKO mice. To determine the relevance of these findings for human disease, we analyzed transcriptome data from multiple independent human cohorts and conducted genetic association studies for ESRRG variants in two distinct human pancreatitis cohorts. RESULTS: Blocking ERRγ function in mice by genetic deletion or inverse agonist treatment results in striking pancreatitis-like phenotypes accompanied by inflammation, fibrosis, and cell death. Mechanistically, loss-of-ERRγ in primary acini abrogates mRNA expression and protein levels of mitochondrial oxidative phosphorylation (OXPHOS) complex genes, resulting in defective acinar cell energetics. Mitochondrial dysfunction due to ERRγ deletion further triggers autophagy dysfunction, ER stress, and production of reactive oxygen species, ultimately leading to cell death. Interestingly, ERRγ-deficient acinar cells that escape cell death acquire ductal cell characteristics indicating a role for ERRγ in acinar-to-ductal metaplasia. Consistent with our findings in ERRγ cKO mice, ERRγ expression was significantly reduced in patients with chronic pancreatitis compared to normal subjects. Furthermore, candidate locus region genetic association studies revealed multiple single nucleotide variants (SNVs) for ERRγ that associated with chronic pancreatitis. CONCLUSIONS: Collectively, our findings highlight an essential role for ERRγ in maintaining the transcriptional program that supports acinar cell mitochondrial function and organellar homeostasis and provide a novel molecular link between ERRγ and exocrine pancreas disorders.

We previously showed that an antagonist-based peptide ligand, H-Cys(Npys)-Arg-Tyr-Tyr-Arg- Ile-Lys-NH2 , captures the free thiol groups in the ligand-binding site of the nociceptin receptor ORL1. However, the exact receptor sites of this thiol-disulfide exchange reaction have not been uncovered, although such identification would help to clarify the ligand recognition site. Since the Cys→Ala substitution prevents the reaction, we performed the so-called Ala scanning for all the Cys residues in the transmembrane (TM) domains of the ORL1 receptor. Seven different mutant receptors were soundly expressed in the COS-7 cells and examined for their specific affinity labeling by a competitive binding assay using nociceptin and [(3) H]nociceptin. The results of in vitro Ala scanning analyses revealed that the labeled residues were Cys59 in TM1, Cys215 and Cys231 in TM5, and Cys310 in TM7. The present study has provided a novel method of Cys(Npys)-affinity labeling for identification of the ligand-binding sites in the ORL1 receptor. © 2016 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 460-469, 2016.

Estrogen-related receptor γ (ERRγ) is a constitutively active nuclear receptor functioning as a transcription factor. ERRγ binds to a single half site designated as ERRE that has only a single DNA-binding motif. However, with regard to the subunit structure, it remains a matter of controversy whether ERRγ binds as a monomer or dimer. Because the ligand-binding domain (LBD) of ERRγ was in a homodimer form in its X-ray crystal structure, the peptide fragments present in the dimer interfaces would perturb or destabilize the dimer structure by inhibiting the mutual interaction among ERRγ molecules. Thus, to demonstrate the essential homodimer structure of ERRγ, we utilized the peptides corresponding to the α-helix peptides 7 (H7), H9, and H10/11 in order to test such inhibitor activity. These selections were done based on a structural analysis of the X-ray crystal structures of ERRγ-LBD, which forms a head-to-head dimer structure. Peptides were evaluated by means of a luciferase reporter gene assay, in which ERRγ exhibited a high constitutive activity with no ligand. When the peptide was expressed in the HeLa cells together with ERRγ, these peptides clearly showed a concentration-dependent activity inhibition, indicating that ERRγ is indeed homodimerized as required for DNA transcription activity. The present results strongly suggest that human nuclear receptor ERRγ functions as a genuine homomeric dimer with symmetrical dimeric interface regions. © 2015 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 547-554, 2016.

Huge numbers of chemicals are released uncontrolled into the environment and some of these chemicals induce unwanted biological effects, both on wildlife and humans. One class of these chemicals are endocrine-disrupting chemicals (EDCs), which are released even though EDCs can affect not only the functions of steroid hormones but also of various signaling molecules, including any ligand-mediated signal transduction pathways. Dichlorodiphenyltrichloroethane (DDT), a pesticide that is already banned, is one of the best-publicized EDCs and its metabolites have been considered to cause adverse effects on wildlife, even though the exact molecular mechanisms of the abnormalities it causes still remain obscure. Recently, an industrial raw material, bisphenol A (BPA), has attracted worldwide attention as an EDC because it induces developmental abnormalities even at low-dose exposures. DDT and BPA derivatives have structural similarities in their chemical features. In this short review, unclear points on the molecular mechanisms of adverse effects of DDT found on alligators are summarized from data in the literature, and recent experimental and molecular research on BPA derivatives is investigated to introduce novel perspectives on BPA derivatives. Especially, a recently developed BPA derivative, bisphenol C (BPC), is structurally similar to a DDT derivative called dichlorodiphenyldichloroethylene (DDE).

IsoVa-RYYRIK-NH2 is a highly specific antagonist ligand of the opioid receptor-like 1 (ORL1) receptor, an endogenous ligand of which is 17-mer peptide nociceptin. ORL1 antagonists have potential for clinical use as analgesic and antineuropathic drugs, and thus information on the receptor-binding characteristics of antagonists is very important for rational drug design. In the present study, we prepared tritium-labelled isova-RYYRIK-NH2 from its precursor with the 3-methylcrotonyl (CH3)2C CHCO group by a catalytic reduction using tritium gas. The resulting [3H]isoVa-RYYRIK-NH2 was evaluated in a saturation binding assay using the COS-7 cell membrane preparations of transiently expressed ORL1. It exhibited more than 90% specific binding with a dissociation constant of 1.21 ± 0.03 nM. From the mutual heterologous binding assays using [3H]isoVa-RYYRIK-NH2 and [3H]nociceptin, isoVa-RYYRIK-NH2 and nociceptin were found to share the receptor-binding site, but each also had a separate specific binding site of its own. They differentiated the two different binding states or conformations of ORL1, which might represent the agonist-active and antagonist-inactive conformations of ORL1. [3H]isoVa-RYYRIK-NH2 is thus a key tracer to uncover the amino acid residues important for receptor inactivation.

An endocrine-disrupting chemical Bisphenol A (BPA) binds specifically to a nuclear receptor (NR) named ERRγ. Although the importance of receptor-binding evaluation for human NRs is often stressed, the binding characteristics of so-called next-generation (NextGen) bisphenol compounds are still poorly understood. The ultimate objective of this investigation was to evaluate BPA and its NextGen analogs for their abilities to bind to 21 human NRs, the greatest members of NRs for which tritium-labeled specific ligands were available. After establishing the detailed assay conditions for each NR, the receptor binding affinities of total 11 bisphenols were evaluated in competitive binding assays. The results clearly revealed that BPA and the NextGen bisphenols of BPAF, BPAP, BPB, BPC, BPE, and BPZ were highly potent against one or more of NRs such as CAR, ERα, ERβ, ERRγ, and GR, with IC50 values of 3.3–73 nM. These bisphenols were suggested strongly to be disruptive to these NRs. BPM and BPP also appeared to be disruptive, but less potently. BPF exhibited only weak effects and only against estrogen-related NRs. Surprisingly, most doubtful bisphenol BPS was supposed not to be disruptive. The NRs to which BPA and NextGen bisphenols did not bind were RARα, RARβ, RARγ, and VDR. PPARγ, RORα, RORβ, RORγ, RXRα, RXRβ, and RXRγ, exhibited very weak interaction with these bisphenols. The ten remaining NRs, namely, ERRγ, ERβ, ERα, CAR, GR, PXR, PR, AR, LXRβ, and LXRα, showed distinctly strong binding to some bisphenols in this order, being likely to have consequential endocrine-disruption effects.

Pigment-dispersing factor (PDF) is a neuropeptide widely distributed in insect brains and plays important roles in the circadian system. In this study, we used RNA interference to study the role of the pigment-dispersing factor ( pdf) gene in regulating circadian locomotor rhythms in the cricket, Gryllus bimaculatus. Injections of pdf double-stranded RNA (ds pdf) effectively knocked down the pdf mRNA and PDF peptide levels. The treated crickets maintained the rhythm both under light-dark cycles (LD) and constant darkness (DD). However, they showed rhythms with reduced nocturnal activity with prominent peaks at lights-on and lights-off. Entrainability of ds pdf-injected crickets was higher than control crickets as they required fewer cycles to resynchronize to the LD cycles shifted by 6 h. The free-running periods of the ds pdf-injected crickets were shorter than those of control crickets in DD. These results suggest that PDF is not essential for the rhythm generation but involved in control of the nocturnality, photic entrainment, and fine tuning of the free-running period of the circadian clock.

Bisphenol AF has been acknowledged to be useful for the production of CF3-containing polymers with improved chemical, thermal, and mechanical properties. Because of the lack of adequate toxicity data, bisphenol AF has been nominated for comprehensive toxicological characterization.We aimed to determine the relative preference of bisphenol AF for the human nuclear estrogenic receptors ERalpha and ERbeta and the bisphenol A-specific estrogen-related receptor ERRgamma, and to clarify structural characteristics of receptors that influence bisphenol AF binding.We examined receptor-binding activities of bisphenol AF relative to [3H]17beta-estradiol (for ERalpha and ERbeta) and [3H]bisphenol A (for ERRgamma). Functional luciferase reporter gene assays were performed to assess receptor activation in HeLa cells.We found that bisphenol AF strongly and selectively binds to ERs over ERRgamma. Furthermore, bisphenol AF receptor-binding activity was three times stronger for ERbeta [IC50 (median inhibitory concentration) = 18.9 nM] than for ERalpha. When examined using a reporter gene assay, bisphenol AF was a full agonist for ERalpha. In contrast, it was almost completely inactive in stimulating the basal constitutive activity of ERbeta. Surprisingly, bisphenol AF acted as a distinct and strong antagonist against the activity of the endogenous ERbeta agonist 17beta-estradiol.Our results suggest that bisphenol AF could function as an endocrine-disrupting chemical by acting as an agonist or antagonist to perturb physiological processes mediated through ERalpha and/or ERbeta.

A receptor-binding assay and X-ray crystal structure analysis demonstrated that the endocrine disruptor bisphenol A (BPA) strongly binds to human estrogen-related receptor gamma (ERRgamma). BPA is well anchored to the ligand-binding pocket, forming hydrogen bonds with its two phenol-hydroxyl groups. In this study, we found that 4-alpha-cumylphenol lacking one of its phenol-hydroxyl groups also binds to ERRgamma very strongly. The 2.0 A crystal structure of the 4-alpha-cumylphenol/ERRgamma complex clearly revealed that ERRgamma's Leu345-beta-isopropyl plays a role in the tight binding of 4-alpha-cumylphenol and BPA, rotating in a back-and-forth induced-fit manner.

Background Various lines of evidence have shown that bisphenol A [BPA; HO-C6H4-C(CH3)2-C6H4-OH] acts as an endocrine disruptor when present in very low doses. We have recently demonstrated that BPA binds strongly to human estrogen-related receptor-γ (ERR-γ ) in a binding assay using [3H]4-hydroxytamoxifen ([3H]4-OHT). We also demonstrated that BPA inhibits the deactivation activity of 4-OHT. Objectives In the present study, we intended to obtain direct evidence that BPA interacts with ERR-γ as a strong binder, and also to clarify the structural requirements of BPA for its binding to ERR-γ. Methods We examined [3H]BPA in the saturation binding assay using the ligand binding domain of ERR-γ and analyzed the result using Scatchard plot analysis. A number of BPA derivatives were tested in the competitive binding assay using [3H]BPA as a tracer and in the luciferase reporter gene assay. Results [3H]BPA showed a KD of 5.50 nM at a Bmax of 14.4 nmol/mg. When we examined BPA derivatives to evaluate the structural essentials required for the binding of BPA to ERR-γ , we found that only one of the two phenol-hydroxyl groups was essential for the full binding. The maximal activity was attained when one of the methyl groups was removed. All of the potent BPA derivatives retained a high constitutive basal activity of ERR-γ in the luciferase reporter gene assay and exhibited a distinct inhibitory activity against 4-OHT. Conclusion These results indicate that the phenol derivatives are potent candidates for the endocrine disruptor that binds to ERR-γ.

Pigment-dispersing factor PDF is an 18-amino acid insect neuropeptide that mediates a circadian rhythmicity in locomotor activity. PDF is coded in a precursor protein together with another neuropeptide named PDF-associated peptide, PAP. PDF is highly conserved among insects, whereas the homology of PAPs is very low with considerably varied amino acid sequences. Since such dissimilarity has suggested that the function of PAP peptide is not associated with that of PDF, we have attempted to analyze the sequences of PDF precursor proteins among a series of species of insects and hypothesized that PDF precursors are classified into at least three different classes: Drosophila-Musca, Meimuna-Romalea, and Gryllus. In order to exemplify this hypothesis, we here describe the molecular cloning of the pdf-gene of the black blowfly Phormia regina and an in silico screening for the pdf-gene in the genome databank of the mosquito Anopheles gambie, both species belonging to the Diptera. It was found that deduced amino acid sequences of PDF peptides are almost completely conserved among all Dipterans and also the amino acid sequences of PAPs are considerably highly preserved (55–82 similarity) among the species of Diptera. The results confirmed the validity of grouping the PDF precursor proteins. In situ hybridization was carried out in fly brains to identify the precise locations of pdf-expressing cells and to examine any daily cycling of pdf mRNA. Intense signals for pdf mRNA were identified in the medulla, but not in the pars lateralis where PDF neurons were strongly immunostained by the antibody raised against PDF peptide. Hybridization was also performed for the brain samples at two hour intervals throughout the day. Although very intense hybridization signals were observed at ZT8 even in some neurites, no prominent rhythmicity of pdf mRNA expression was observed.

Pigment-dispersing factor PDF is an 18-amino acid insect neuropeptide that mediates a circadian rhythmicity in locomotor activity. PDF is coded in a precursor protein together with another neuropeptide named PDF-associated peptide, PAP. PDF is highly conserved among insects, whereas the homology of PAPs is very low with considerably varied amino acid sequences. Since such dissimilarity has suggested that the function of PAP peptide is not associated with that of PDF, we have attempted to analyze the sequences of PDF precursor proteins among a series of species of insects and hypothesized that PDF precursors are classified into at least three different classes: Drosophila-Musca, Meimuna-Romalea, and Gryllus. In order to exemplify this hypothesis, we here describe the molecular cloning of the pdf-gene of the black blowfly Phormia regina and an in silico screening for the pdf-gene in the genome databank of the mosquito Anopheles gambie, both species belonging to the Diptera. It was found that deduced amino acid sequences of PDF peptides are almost completely conserved among all Dipterans and also the amino acid sequences of PAPs are considerably highly preserved (55–82 similarity) among the species of Diptera. The results confirmed the validity of grouping the PDF precursor proteins. In situ hybridization was carried out in fly brains to identify the precise locations of pdf-expressing cells and to examine any daily cycling of pdf mRNA. Intense signals for pdf mRNA were identified in the medulla, but not in the pars lateralis where PDF neurons were strongly immunostained by the antibody raised against PDF peptide. Hybridization was also performed for the brain samples at two hour intervals throughout the day. Although very intense hybridization signals were observed at ZT8 even in some neurites, no prominent rhythmicity of pdf mRNA expression was observed.

Bisphenol A, 2,2-bis(4-hydroxyphenyl)propane, is an estrogenic endocrine disruptor that influences various physiological functions at very low doses, even though bisphenol A itself is ineffectual as a ligand for the estrogen receptor. We recently demonstrated that bisphenol A binds strongly to human estrogen-related receptor gamma, one of 48 human nuclear receptors. Bisphenol A functions as an inverse antagonist of estrogen-related receptor gamma to sustain the high basal constitutive activity of the latter and to reverse the deactivating inverse agonist activity of 4-hydroxytamoxifen. However, the intrinsic binding mode of bisphenol A remains to be clarified. In the present study, we report the binding potentials between the phenol-hydroxyl group of bisphenol A and estrogen-related receptor gamma residues Glu275 and Arg316 in the ligand-binding domain. By inducing mutations in other amino acids, we evaluated the change in receptor binding capability of bisphenol A. Wild-type estrogen-related receptor gamma-ligand-binding domain showed a strong binding ability (K(D) = 5.70 nm) for tritium-labeled [(3)H]bisphenol A. Simultaneous mutation to Ala at positions 275 and 316 resulted in an absolute inability to capture bisphenol A. However, individual substitutions revealed different degrees in activity reduction, indicating the chief importance of phenol-hydroxyl--Arg316 hydrogen bonding and the corroborative role of phenol-hydroxyl--Glu275 hydrogen bonding. The data obtained with other characteristic mutations suggested that these hydrogen bonds are conducive to the recruitment of phenol compounds by estrogen-related receptor gamma. These results clearly indicate that estrogen-related receptor gamma forms an appropriate structure presumably to adopt an unidentified endogenous ligand.

Pigment-dispersing factor (PDF), an 18-amino acid neuropeptide, is a principal circadian neurotransmitter for the circadian rhythms of the locomotor activity in flies. Recently, two completely different types of PDF precursor were clarified; that of the cricket Gryllus bimaculatus and that of the last-summer cicada Meimuna opalifera. The G. bimaculatus PDF precursor is extraordinarily short and comprises a nuclear localization signal (NLS), while the M. opalifera PDF precursor is of ordinary length, comparable to that seen for the precursors of crustacean beta-PDH homologues. Although their PDF peptide regions were exactly the same, the regions containing a signal peptide combined with a PDF-associated peptide (PAP) were remarkably different from each other. Such a grouping suggested a fundamental role for the PAP peptide in the circadian clock, perhaps associated with PDF function. In the present study, the cDNA cloning of PDF from the adult brains of the housefly Musca domestica was carried out and it was found that an isolated clone (527 bp) encodes a PDF precursor protein of ordinary length. The PDF peptide shows a high sequence identity (78%-94%) and similarity (89%-100%) to insect PDFs and also to the crustacean beta-PDH peptides. In particular, there is only a single amino acid difference between the PDFs of Musca and Drosophila; at position 14 Ser for Musca PDF and Asn for Drosophila PDF. A characteristic Ser10 in Drosophila was retained in Musca, indicating the presence of a structural profile unique to these PDFs. The results of sequence analyses suggest that Musca and Drosophila PDFs are to be considered members of a single group that has evolved structurally. When the primary structure of the PAP regions was compared, the Musca PDF precursor also belonged to the same group as that to which the Drosophila PDF precursor belongs.

In the ligand/receptor interaction, the side chain phenyl group of phenylalanine (Phe) is involved in a so-called hydrophobic interaction, in which the Phe-phenyl group functions as a p element or merely as a hydrophobic element. The thrombin receptor-tethered ligand SFLLRNP consists of the Phe-2 residue essential for receptor activation. In order to explore the molecular characteristics of this Phe-2-phenyl group, a complete set of S/Phe/LLRNP peptides comprising six different difluorophenylalanine isomers [(F(2))Phe] was newly synthesized and assayed to evaluate their ability to induce the aggregation of human platelets. The assay results clarified several important structural elements to conclude that Phe-2-phenyl of S/Phe/LLRNP is in the edge-to-face CH/pi interaction with the receptor aromatic group, utilizing the Phe-phenyl edge along with adjacent benzene hydrogens at positions (2-3) or (5-6). It was also found that the fluorine atom at position 4 increases the acidity of the hydrogen mainly at its ortho position, resulting in a reinforcement of the CH/pi interaction and thus in an enhancement of biological activity. The H-->F replacement in the benzene ring was found to provide an effective structural examination to the Phe residue; i.e., to identify the hydrogens in the CH/pi interaction, and to strengthen the CH/pi interaction.