Characterization of follistatin-type domains and their contribution to myostatin and activin a antagonism

Follistatin (FST)-type proteins are important antagonists of some members of the large TGF-β family of cytokines. These include myostatin, an important negative regulator of muscle growth, and the closely related activin A, which is involved in many physiological functions, including maintenance of a normal reproductive axis. FST-type proteins, including FST and FST-like 3 (FSTL3), differentially inhibit various TGF-β family ligands by binding each ligand with two FST-type molecules. In this study, we sought to examine features that are important for ligand antagonism by FST-type proteins. Previous work has shown that a modified construct consisting of the FST N-terminal domain (ND) followed by two repeating follistatin domains (FSD), herein called FST ND-FSD1-FSD1, exhibits strong specificity for myostatin over activin A. Using cell-based assays, we show that FST ND-FSD1-FSD1 is unique in its specificity for myostatin as compared with similar constructs containing domains from FSTL3 and that the ND is critical to its activity. Furthermore, we demonstrate that FSD3 of FST provides affinity to ligand inhibition and confers resistance to perturbations in the ND and FSD2, likely through the interaction of FSD3 of one FST molecule with the ND of the other FST molecule. Additionally, our data suggest that this contact provides cooperativity to ligand antagonism. Cross-linking studies show that this interaction also potentiates formation of 1:2 ligand-FST complexes, whereas lack of FSD3 allows formation of 1:1 complexes. Altogether, these studies support that domain differences generate FST-type molecules that are each uniquely suited ligand antagonists.     

Thermal Unfolding Pathway of PHD2 Catalytic Domain in Three Different PHD2 Species: Computational Approaches

Prolyl hydroxylase domain 2 containing protein (PHD2) is a key protein in regulation of angiogenesis and metastasis. In normoxic condition, PHD2 triggers the degradation of hypoxia-inducible factor 1 (HIF-1α) that induces the expression of hypoxia response genes. Therefore the correct function of PHD2 would inhibit angiogenesis and consequent metastasis of tumor cells in normoxic condition. PHD2 mutations were reported in some common cancers. However, high levels of HIF-1α protein were observed even in normoxic metastatic tumors with normal expression of wild type PHD2. PHD2 malfunctions due to protein misfolding may be the underlying reason of metastasis and invasion in such cases. In this study, we scrutinize the unfolding pathways of the PHD2 catalytic domain’s possible species and demonstrate the properties of their unfolding states by computational approaches. Our study introduces the possibility of aggregation disaster for the prominent species of PHD2 during its partial unfolding. This may justify PHD2 inability to regulate HIF-1α level in some normoxic tumor types.     

Metabolomic analysis of sex specific metabolites in gonads of the mussel,Mytilus edulis

Marine mussels have been used as sentinel organisms to monitor exposure to a variety of chemical contaminants, including endocrine disrupting chemicals, in the aquatic environment. Although they are an important species for use in ecotoxicology investigations, information on their reproductive physiology and biochemistry is fragmentary. Mass spectrometry-based profiling techniques are increasingly being used to study how the metabolome of an organism changes as a result of tissue differentiation, disease or in response to environmental stressors. In this study, ultraperformance liquid chromatography–time-of-flight-mass spectrometry (UPLC–TOFMS) was used to investigate sex specific differences in the mussel metabolome in order to further investigate the reproductive physiology of this species. Using this method, a comparison of female and male mantle tissues containing mature gonad, revealed significant differences in glycerophosphatidylcholine (PC) and lysophosphatidylcholine (LPC) metabolites. A number of other unidentified metabolites, including those putatively identified as conjugated sterols, were also differentially expressed between male and female mantle/gonadal tissue.     

Sexual differentiation in quail: Conversion of androgen to estrogen mediates testosterone-induced demasculinization of copulation but not other male characteristics

Previous research has shown that administration of either testosterone or estradiol to male quail embryos will demasculinize behavior and morphology. Six experiments in which embryos were treated were conducted to test the hypothesis that this testosterone-induced demasculinization is due to conversion of testosterone to estrogen (aromatization). In Experiment 1, dihydrotestosterone propionate, a nonaromatizable androgen, failed to demasculinize copulatory behavior, but did demasculinize crowing, strutting, and proctodeal glands. In Experiment 2, injection of the aromatizable androgens testosterone propionate (TP), testosterone, or androstenedione demasculinized copulatory behavior, the nonaromatizable androgen androsterone failed to have such an effect, and all androgens demasculinized proctodeal glands. In Experiment 3, Silastic implants of testosterone demasculinized all male characteristics, whereas implants of androsterone demasculinized only proctodeal glands. In Experiment 4, the antiestrogen tamoxifen prevented TP from demasculinizing copulatory behavior, but had no such effect with respect to crowing and strutting. In Experiments 5 and 6, the aromatization inhibitor 1,4,6-androstatrien-3,17-dione (ATD) prevented TP but not estradiol benzoate from demasculinizing copulatory behavior. Thus (1) in quail, testosterone-induced demasculinization of copulatory behavior is due to androgen aromatization, whereas testosterone-induced demasculinization of crowing, strutting, and proctodeal glands is not; (2) the distinct components of normal male reproductive behavior exhibit different patterns of steroid specificity during the organizational period, as was previously shown for the activational period; (3) the steroid specificity of crowing, strutting, and proctodeal glands changes between the organizational and activational periods. During organization, there is little specificity, whereas during activation, these characteristics respond only to androgens, never to estrogens. This difference suggests that developmental changes have occurred in the underlying biochemical substrates.     

Use of Citrobacter koseri whole cells for the production of arabinonucleosides: A larger scale approach

Purine arabinosides are well known antiviral and antineoplastic drugs. Since their chemical synthesis is complex, time-consuming, and polluting, enzymatic synthesis provides an advantageous alternative. In this work, we describe the microbial whole cell synthesis of purine arabinosides through nucleoside phosphorylase-catalyzed transglycosylation starting from their pyrimidine precursors. By screening of our microbial collection, Citrobacter koseri (CECT 856) was selected as the best biocatalyst for the proposed biotransformation. In order to enlarge the scale of the transformations to 150 mL for future industrial applications, the biocatalyst immobilization by entrapment techniques and its behavior in different reactor configurations, considering both batch and continuous processes, were analyzed. C. koseri immobilized in agarose could be used up to 68 times and the storage stability was at least 9 months. By this approach, fludarabine (58% yield in 14 h), vidarabine (71% yield in 26 h) and 2,6-diaminopurine arabinoside (77% yield in 24 h), were prepared.