Activation of estrogen receptor-beta by a special extract of Rheum rhaponticum (ERr 731), its aglycones and structurally related compounds

The special extract ERr 731^® from the roots of Rheum rhaponticum is the major constituent of Phytoestrol^® N which is used for the treatment of climacteric symptoms in menopausal women. However, the molecular mode of action of ERr 731^® was unknown. For the first time, ERr 731^® and its aglycones trans-rhapontigenin and desoxyrhapontigenin were investigated with regard to the activation of the estrogen receptor- or estrogen receptor-β (ER, ERβ). The related hydroxystilbenes cis-rhapontigenin, resveratrol and piceatannol were studied as comparators. As controls, 17β-estradiol or the selective ER-(propylpyrazoltriol) or ERβ-agonists (diarylpropionitril) were used. Neither in ER-expressing yeast cells, in the ER-responsive Ishikawa cells, nor in human endometrial HEC-1B cells transiently transfected with the ER an activation of ER by ERr 731^® or the other single compounds was detected. Furthermore, an antiestrogenic effect was not observed. In contrast in human endometrial HEC-1B cells transiently transfected with the ERβ, 100 ng/ml ERr 731^® and the single compounds significantly induced the ERβ-coupled luciferase activity in a range comparable to 10⁻⁸ M 17β-estradiol. All effects were abolished with the pure ER antagonist ICI 182780, indicating an ER-specific effect. The ERβ agonistic activity by ERr 731^® could be of importance for its clinical use, as central functions relevant to climacteric complaints are proposed to be mediated via ERβ activation.     

Hepatocyte growth factor enhances IL-1β stimulated IL-8 secretion by Caco-2 epithelial cells

Hepatocyte growth factor (HGF) can induce proliferation and migration of intestinal epithelial cells and has also been shown to be important in wound healing of inflamed mucosal tissues. HGF is known to be expressed along with interleukin-1 (IL-1) by inflamed mucosal tissues, yet the effect of HGF on IL-1-induced proinflammatory cytokine responses by colonic epithelial cells is unknown. In this report, we have examined the effect of HGF on IL-1-induced secretion of IL-8 by the Caco-2 colonic epithelial cell line. HGF stimulation alone had no effect on the secretion of IL-8 by the Caco-2 cells. However, culture of the cells with HGF and suboptimal levels of IL-1 resulted in a significant enhancement of IL-8 secretion compared to cells cultured with IL-1 alone. A similar effect was seen with HGF and IL-1 simulation of monocyte chemoattractant protein-1 secretion by the rat IEC-6 intestinal epithelial cell line. The enhancing effect of HGF was seen regardless of whether the culture medium contained serum or not. Simultaneous stimulation with HGF and IL-1 was required for the enhancing effect as cells pretreated with HGF for 24 h and then stimulated with IL-1 alone secreted IL-8 levels similar to that of cells stimulated with IL-1 alone. These results suggest that in addition to wound healing, HGF may play a role in the IL-1-induced chemokine response of epithelial cells in inflamed mucosal tissues.     

Low folding propensity and high translation efficiency distinguish in vivo substrates of GroEL from other Escherichia coli proteins

MOTIVATION: Theoretical considerations have indicated that the amount of chaperonin GroEL in Escherichia coli cells is sufficient to fold only approximately 2-5% of newly synthesized proteins under normal physiological conditions, thereby suggesting that only a subset of E.coli proteins fold in vivo in a GroEL-dependent manner. Recently, members of this subset were identified in two independent studies that resulted in two partially overlapping lists of GroEL-interacting proteins. The objective of the work described here was to identify sequence-based features of GroEL-interacting proteins that distinguish them from other E.coli proteins and that may account for their dependence on the chaperonin system. RESULTS: Our analysis shows that GroEL-interacting proteins have, on average, low folding propensities and high translation efficiencies. These two properties in combination can increase the risk of aggregation of these proteins and, thus, cause their folding to be chaperonin-dependent. Strikingly, we find that these properties are absent in proteins homologous to the E.coli GroEL-interacting proteins in Ureaplasma urealyticum, an organism that lacks a chaperonin system, thereby confirming our conclusions.     

A tale of two tails: why are terminal residues of proteins exposed?

MOTIVATION: It is widely known that terminal residues of proteins (i.e. the N- and C-termini) are predominantly located on the surface of proteins and exposed to the solvent. However, there is no good explanation as to the forces driving this phenomenon. The common explanation that terminal residues are charged, and charged residues prefer to be on the surface, cannot explain the magnitude of the phenomenon. Here, we survey a large number of proteins from the PDB in order to explore, quantitatively, this phenomenon, and then we use a lattice model to study the mechanisms involved. RESULTS: The location of the termini was examined for 425 small monomeric proteins (50-200 amino acids) and it was found that the average solvent accessibility of termini residues is 87.1% compared with 49.2% of charged residues and 35.9% of all residues. Using a cutoff of 50% of the maximal possible exposure, 80.3% of the N-terminal and 86.1% of the C-terminal residues are exposed compared to 32% for all residues. In addition, terminal residues are much more distant from the center of mass of their proteins than other residues. Using a 2D lattice, a large population of model proteins was studied on three levels: structural selection of compact structures, thermodynamic selection of conformations with a pronounced energy gap and kinetic selection of fast folding proteins using Monte-Carlo simulations. Progressively, each selection raises the proportion of proteins with termini on the surface, resulting in similar proportions to those observed for real proteins.     

Different mechanistic requirements for prokaryotic and eukaryotic chaperonins: a lattice study

MOTIVATION: The folding of many proteins in vivo and in vitro is assisted by molecular chaperones. A well-characterized molecular chaperone system is the chaperonin GroEL/GroES from Escherichia coli which has a homolog found in the eukaryotic cytosol called CCT. All chaperonins have a ring structure with a cavity in which the substrate protein folds. An interesting difference between prokaryotic and eukaryotic chaperonins is in the nature of the ATP-mediated conformational changes that their ring structures undergo during their reaction cycle. Prokaryotic chaperonins are known to exhibit a highly cooperative concerted change of their cavity surface while in eukaryotic chaperonins the change is sequential. Approximately 70% of proteins in eukaryotic cells are multi-domain whereas in prokaryotes single-domain proteins are more common. Thus, it was suggested that the different modes of action of prokaryotic and eukaryotic chaperonins can be explained by the need of eukaryotic chaperonins to facilitate folding of multi-domain proteins. RESULTS: Using a 2D square lattice model, we generated two large populations of single-domain and double-domain substrate proteins. Chaperonins were modeled as static structures with a cavity wall with which the substrate protein interacts. We simulated both concerted and sequential changes of the cavity surfaces and demonstrated that folding of single-domain proteins benefits from concerted but not sequential changes whereas double-domain proteins benefit also from sequential changes. Thus, our results support the suggestion that the different modes of allosteric switching of prokaryotic and eukaryotic chaperonin rings have functional implications as it enables eukaryotic chaperonins to better assist multi-domain protein folding.     

Perception versus polysomnographic assessment of sleep in CFS and non-fatigued control subjects: results from a population-based study

Background  

Complaints of unrefreshing sleep are a prominent component of chronic fatigue syndrome (CFS); yet, polysomnographic studies have not consistently documented sleep abnormalities in CFS patients. We conducted this study to determine whether alterations in objective sleep characteristics are associated with subjective measures of poor sleep quality in persons with CFS.     

Marker tolerant,immunocompetent animals as a new tool for regenerative medicine and long-term cell tracking

Background  

Immune-mediated rejection of labeled cells is a general problem in transplantation studies using cells labeled with any immunogenic marker, and also in gene therapy protocols. The aim of this study was to establish a syngeneic model for long-term histological cell tracking in the absence of immune-mediated rejection of labeled cells in immunocompetent animals. We used inbred transgenic Fischer 344 rats expressing human placental alkaline phosphatase (hPLAP) under the control of the ubiquitous R26 promoter for this study. hPLAP is an excellent marker enzyme, providing superb histological detection quality in paraffin and plastic sections.     

<Emphasis Type="Italic">Decapentaplegic</Emphasis> (<Emphasis Type="Italic">dpp</Emphasis>) regulates the growth of a morphological novelty,beetle horns

Studies focusing on the development of morphological novelties suggest that patterning genes underlying traditional appendage development (i.e. mouthparts, legs, and wings) also play important roles in patterning novel morphological structures. In this study, we examine whether the expression and function of a member of the TGF-β signaling pathway, decapentaplegic (dpp), promotes development of a morphologically novel structure: beetle horns. Beetle horns are complex secondary sexual structures that develop in the head and/or prothorax, lack obvious homology to other insect outgrowths, and vary remarkably between species and sexes. We studied dpp expression through in situ hybridization, performed functional analyses with RNA interference, and gathered allometric measurements to determine the role of dpp during both pronotal and head horn development in both sexes of two morphologically dissimilar species in the Onthophagus genus, Onthophagus binodis and Onthophagus sagittarius. Our findings show that in addition to affecting growth and patterning of traditional appendages, dpp regulates beetle horn growth and remodeling.     

Quinazolinones as γ-secretase modulators

Synthesis, SAR and evaluation of styrenyl quinazolinones as novel gamma secretase modulators are presented in this communication. Starting from literature and in-house leads we evaluated a range of quinazolinones which showed good modulation of γ-secretase activity.