Reproductive and metabolic responses of desert adapted common spiny male mice (Acomys cahirinus) to vasopressin treatment

Sufficient amounts of water and food are important cues for reproduction in an unpredictable environment. We previously demonstrated that increased osmolarity levels, or exogenous vasopressin (VP) treatment halt reproduction of desert adapted golden spiny mice Acomys russatus. In this research we studied gonad regulation by VP and food restriction (FR) in desert adapted common spiny mouse (A. cahirinus) males, kept under two different photoperiod regimes-short (SD-8L:16D) and long (LD-16L:8D) days. Mice were treated with VP, FR, and VP+FR for three weeks. Response was assessed from changes in relative testis mass, serum testosterone levels and mRNA receptor gene expression of VP, aldosterone and leptin in treated groups, compared with their controls. SD-acclimation increased testosterone levels, VP treatment decreased expression of aldosterone mRNA receptor in the testes of SD-acclimated males. FR under SD-conditions resulted in testosterone decrease and elevation of VP- receptor gene expression in testes. Aldosterone receptor mRNA expression was also detected in WAT. These results support the idea that water and food availability in the habitat may be used as signals for activating the reproductive system through direct effects of VP, aldosterone and leptin on the testes or through WAT by indirect effects.     

Different endocytic functions of AGEF-1 in C. elegans coelomocytes

Background

ADP-ribosylation factors (ARFs) are a family of small GTP-binding proteins that play roles in membrane dynamics and vesicle trafficking. AGEF-1, which is thought to act as a guanine nucleotide exchange factor of class I ARFs, is required for caveolin-1 body formation and receptor-mediated endocytosis in oocytes of Caenorhabditis elegans. This study explores additional roles of AGEF-1 in endocytic transport.

Methods

agef-1 expression was knocked down by using RNAi in C. elegans. Markers that allow analysis of endocytic transport in scavenger cells were investigated for studying the effect of AGEF-1 on different steps of membrane transport.

Results

Knockdown of AGEF-1 levels results in two apparent trafficking defects in coelomocytes of C. elegans. First, there is a delay in the uptake of solutes from the extracellular medium. Second, there is a dramatic enlargement of the sizes of lysosomes, even though lysosomal acidification is normal and degradation still occurs.

Conclusion

Our results suggest that AGEF-1 regulates endosome/lysosome fusion or fission events, in addition to earlier steps in endocytic transport.

General significance

AGEF-1 is the first identified GTPase regulator that functions at the lysosome fusion or fission stage of the endocytic pathway. Our study provides insight into lysosome dynamics in C. elegans.     

Isoprene emission and primary metabolism in Phragmites australis grown under different phosphorus levels

Aquatic plants are generally used for wastewater purification and phytoremediation, but some of them also emit large amounts of isoprene, the most abundant biogenic volatile organic compound. Since isoprenoid biosynthesis requires high amounts of phosphorylated intermediates, the emission may also be controlled by inorganic phosphorus concentration (Pi) in leaves. We carried out experiments to determine the emission of isoprene from Phragmites australis plants used in reconstructed wetlands to phytoremediate elevated levels of phosphorus contributed by urban wastes. Four groups of plants were grown hydroponically in water containing different levels of KH(2)PO(4). High levels of phosphorus in the water resulted in high Pi in the leaves. High Pi stimulated photosynthesis at intercellular CO(2) concentrations lower and higher than ambient, implying higher ribulose 1,5-bisphosphate carboxylase (Rubisco) activity and higher ribulose 1,5-bisphosphate regeneration rates, respectively. However, isoprene emission was substantially lower at high Pi than at low Pi, and was not associated to photosynthesis rates at high Pi. This surprising result suggests that isoprene is limited by processes other than photosynthetic intermediate availability or by energetic (ATP) requirements under high Pi levels. Irrespective of the mechanism responsible for the observed reduction of isoprene emission, our results show that Phragmites plants may effectively remove phosphorus from water without concurrently increase isoprene emission, at least on a leaf area basis. Thus, Phragmites used in reconstructed wetlands for phytoremediation of urban wastes rich of phosphates will not contribute high loads of hydrocarbons which may influence air quality over urban and peri-urban areas.     

Quinazolinone derivatives as inhibitors of homologous recombinase RAD51

RAD51 is a vital component of the homologous recombination DNA repair pathway and is overexpressed in drug-resistant cancers, including aggressive triple negative breast cancer (TNBC). A proposed strategy for improving therapeutic outcomes for patients is through small molecule inhibition of RAD51, thereby sensitizing tumor cells to DNA damaging irradiation and/or chemotherapy. Here we report structure-activity relationships for a library of quinazolinone derivatives. A novel RAD51 inhibitor (17) displays up to 15-fold enhanced inhibition of cell growth in a panel of TNBC cell lines compared to compound B02, and approximately 2-fold increased inhibition of irradiation-induced RAD51 foci formation. Additionally, compound 17 significantly inhibits TNBC cell sensitivity to DNA damage, implying a potentially targeted therapy for cancer treatment.     

Mutational dynamics of murine angiogenin duplicates

Background  

Angiogenin (Ang) is a protein involved in angiogenesis by inducing the formation of blood vessels. The biomedical importance of this protein has come from findings linking mutations in Ang to cancer progression and neurodegenerative diseases. These findings highlight the evolutionary constrain on Ang amino acid sequence. However, previous studies comparing human Angiogenin with homologs from other phylogenetically related organisms have led to the conclusion that Ang presents a striking variability. Whether this variability has an adaptive value per se remains elusive. Understanding why many functional Ang paralogs have been preserved in mouse and rat and identifying functional divergence mutations at these copies may explain the relationship between mutations and function. In spite of the importance of testing this hypothesis from the evolutionarily and biomedical perspectives, this remains yet unaccomplished. Here we test the main mutational dynamics driving the evolution and function of Ang paralogs in mammals.     

SEL-5, a serine/threonine kinase that facilitates lin-12 activity in Caenorhabditis elegans

Ligands present on neighboring cells activate receptors of the LIN-12/Notch family by inducing a proteolytic cleavage event that releases the intracellular domain. Mutations that appear to eliminate sel-5 activity are able to suppress constitutive activity of lin-12(d) mutations that are point mutations in the extracellular domain of LIN-12, but cannot suppress lin-12(intra), the untethered intracellular domain. These results suggest that sel-5 acts prior to or during ligand-dependent release of the intracellular domain. In addition, sel-5 suppression of lin-12(d) mutations is tissue specific: loss of sel-5 activity can suppress defects in the anchor cell/ventral uterine precursor cell fate decision and a sex myoblast/coelomocyte decision, but cannot suppress defects in two different ventral hypodermal cell fate decisions in hermaphrodites and males. sel-5 encodes at least two proteins, from alternatively spliced mRNAs, that share an amino-terminal region and differ in the carboxy-terminal region. The amino-terminal region contains the hallmarks of a serine/threonine kinase domain, which is most similar to mammalian GAK1 and yeast Pak1p.     

The role of O-linked and N-linked oligosaccharides on the structure-function of glycoprotein hormones: development of agonists and antagonists

Thyrotropin (TSH) and the gonadotropins; follitropin (FSH), lutropin (LH) and human chorionic gonadotropin (hCG) are a family of heterodimeric glycoprotein hormones. These hormones composed of two noncovalently linked subunits; a common alpha and a hormone specific beta subunits. Assembly of the subunits is vital to the function of these hormones. However, genetic fusion of the alpha and beta subunits of hFSH, hCG and hTSH resulted in active polypeptides. The glycoprotein hormone subunits contain one (TSH and LH) or two (alpha, FSHbeta and hCGbeta) asparagine-linked (N-linked) oligosaccharides. CGbeta subunit is distinguished among the beta subunits because of the presence of a carboxyl-terminal peptide (CTP) bearing four O-linked oligosaccharide chains. To examine the role of the oligosaccharide chains on the structure-function of glycoprotein hormones, chemical, enzymatic and site-directed mutagenesis were used. The results indicated that O-linked oligosaccharides play a minor role in receptor binding and signal transduction of the glycoprotein hormones. In contrast, the O-linked oligosaccharides are critical for in vivo half-life and bioactivity. Ligation of the CTP bearing four O-linked oligosaccharide sites to different proteins, resulted in enhancing the in vivo bioactivity and half-life of the proteins. The N-linked oligosaccharide chains have a minor role in receptor binding of glycoprotein hormones, but they are critical for bioactivity. Moreover, glycoprotein hormones lacking N-linked oligosaccharides behave as antagonists. In conclusion, the O-linked oligosaccharides are not important for in vitro bioactivity or receptor binding, but they play an important role in the in vivo bioactivity and half-life of the glycoprotein hormones. Addition of the O-linked oligosaccharide chains to the backbone of glycoprotein hormones could be an interesting strategy for designing long acting agonists of glycoprotein hormones. On the other hand, the N-linked oligosaccharides are not important for receptor binding, but they are critical for bioactivity of glycoprotein hormones. Deletion of the N-linked oligosaccharides resulted in the development of glycoprotein hormone antagonists. In the case of hTSH, development of an antagonist may offer a novel therapeutic strategy in the treatment of thyrotoxicosis caused by Graves' disease and TSH secreting pituitary adenoma.     

Identification and Isolation of a Castellaniella Species Important during Biostimulation of an Acidic Nitrate- and Uranium-Contaminated Aquifer

Immobilization of uranium in groundwater can be achieved through microbial reduction of U(VI) to U(IV) upon electron donor addition. Microbial community structure was analyzed in ethanol-biostimulated and control sediments from a high-nitrate (>130 mM), low-pH, uranium-contaminated site in Oak Ridge, TN. Analysis of small subunit (SSU) rRNA gene clone libraries and polar lipid fatty acids from sediments revealed that biostimulation resulted in a general decrease in bacterial diversity. Specifically, biostimulation resulted in an increase in the proportion of Betaproteobacteria (10% of total clones in the control sediment versus 50 and 79% in biostimulated sediments) and a decrease in the proportion of Gammaproteobacteria and Acidobacteria. Clone libraries derived from dissimilatory nitrite reductase genes (nirK and nirS) were also dominated by clones related to Betaproteobacteria (98% and 85% of total nirK and nirS clones, respectively). Within the nirK libraries, one clone sequence made up 59 and 76% of sequences from biostimulated sediments but only made up 10% of the control nirK library. Phylogenetic analysis of SSU rRNA and nirK gene sequences from denitrifying pure cultures isolated from the site indicate that all belong to a Castellaniella species; nearly identical sequences also constituted the majority of biostimulated SSU rRNA and nirK clone libraries. Thus, by combining culture-independent with culture-dependent techniques, we were able to link SSU rRNA clone library information with nirK sequence data and conclude that a potentially novel Castellaniella species is important for in situ nitrate removal at this site.