ATP synthase complex of Plasmodium falciparum: dimeric assembly in mitochondrial membranes and resistance to genetic disruption

The rotary nanomotor ATP synthase is a central player in the bioenergetics of most organisms. Yet the role of ATP synthase in malaria parasites has remained unclear, as blood stages of Plasmodium falciparum appear to derive ATP largely through glycolysis. Also, genes for essential subunits of the F(O) sector of the complex could not be detected in the parasite genomes. Here, we have used molecular genetic and immunological tools to investigate the localization, complex formation, and functional significance of predicted ATP synthase subunits in P. falciparum. We generated transgenic P. falciparum lines expressing seven epitope-tagged canonical ATP synthase subunits, revealing localization of all but one of the subunits to the mitochondrion. Blue native gel electrophoresis of P. falciparum mitochondrial membranes suggested the molecular mass of the ATP synthase complex to be greater than 1 million daltons. This size is consistent with the complex being assembled as a dimer in a manner similar to the complexes observed in other eukaryotic organisms. This observation also suggests the presence of previously unknown subunits in addition to the canonical subunits in P. falciparum ATP synthase complex. Our attempts to disrupt genes encoding β and γ subunits were unsuccessful, suggesting an essential role played by the ATP synthase complex in blood stages of P. falciparum. These studies suggest that, despite some unconventional features and its minimal contribution to ATP synthesis, P. falciparum ATP synthase is localized to the parasite mitochondrion, assembled as a large dimeric complex, and is likely essential for parasite survival.     

Impact of incubation period on biodegradation of petroleum hydrocarbons from refinery wastewater in Kuantan,Malaysia by indigenous bacteria

This work studied the biodegradation of petroleum hydrocarbons (PHCs) extracted from refinery wastewater to produce industrially important by-products at different incubation periods. Two out of 13 bacterial isolates, KRD2 and KRA4 were isolated. Dichloromethane was used to extract the PHC, and gas chromatography-mass spectrometry (GC-MS) analysis revealed that the refinery wastewater PHC was successfully biodegraded using the selected bacterial isolates within 15 days of incubation. Both KRD2 and KRA4 isolates degraded all 13 initially extracted PHC compounds within 5 days, except C13BD and C9BD, which produced 6 and 4 compounds as secondary metabolites with peak area percentages of 1.58, 1.38, 0.85, 29.94, 7.59, and 11.16% and 3.55, 2.88, 52.31, and 6.14%, respectively. These metabolites have been reported in industrial and medical applications. After 10 days, only 6 and 8 compounds were degraded by both isolates, respectively, and C11PAD compound was produced, as well as C5PAD, C7PAD, and C13PAD. After 15 days, it was clear that all the initial PHC compounds have been completely degraded by both isolates. Metabolites C5PAD, C6PAD, C8PAD, and C13PAD were produced by KRD2, and metabolites C5PAD, C6PAD, C8PAD, and C9PAD were produced by KRA4 at different peak areas. The alignment revealed that the KRA4 isolate was included in the genus Chryseobacterium gambrini, while KRD2 isolate was successfully identified as Mycobacterium confluentis using the Biolog microbial identification system. The incubation period evidently affected biodegradation process by indigenous degraders. These effective bacteria were shown to be of great potential for further application in biodegradation technology of PHC contaminated refinery wastewater to produce industrially important by-products.     

Retinoic acid exerts sexually dimorphic effects on muscle energy metabolism and function

The retinol dehydrogenase Rdh10 catalyzes the rate-limiting reaction that converts retinol into retinoic acid (RA), an autacoid that regulates energy balance and reduces adiposity. Skeletal muscle contributes to preventing adiposity, by consuming nearly half the energy of a typical human. We report sexually dimorphic differences in energy metabolism and muscle function in Rdh10+/− mice. Relative to wild-type (WT) controls, Rdh10+/− males fed a high-fat diet decrease reliance on fatty-acid oxidation and experience glucose intolerance and insulin resistance. Running endurance decreases 40%. Rdh10+/− females fed this diet increase fatty acid oxidation and experience neither glucose intolerance nor insulin resistance. Running endurance increases 220%. We therefore assessed RA function in the mixed-fiber type gastrocnemius muscles (GM), which contribute to running, rather than standing, and are similar to human GM. RA levels in Rdh10+/− male GM decrease 38% relative to WT. Rdh10+/− male GM increase expression of Myog and reduce Eif6 mRNAs, which reduce and enhance running endurance, respectively. Cox5A, complex IV activity, and ATP decrease. Increased centralized nuclei reveal existence of muscle malady and/or repair in GM fibers. Comparatively, RA in Rdh10+/− female GM decreases by less than half the male decrease, from a more modest decrease in Rdh10 and an increase in the estrogen-induced retinol dehydrogenase Dhrs9. Myog mRNA decreases. Cox5A, complex IV activity, and ATP increase. Centralized GM nuclei do not increase. We conclude that Rdh10/RA affects whole body energy use and insulin resistance partially through sexual dimorphic effects on skeletal muscle gene expression, structure, and mitochondria activity.     

Does Breeding Ornamentation Signal Genetic Quality in Arctic charr, <Emphasis Type=Italic>Salvelinus alpinus</Emphasis>?

Genetic theories of sexual selection predict that most ornamental secondary sexual traits provide reliable indication of the genetic quality of their bearers. Accordingly, also the offspring of mates with elaborate mating display should perform better than those of less conspicuous counterparts. In this study, we used Arctic charr (Salvelinus alpinus) as a model species to investigate whether the variation in a carotenoid-based red breeding coloration (a sexually dichromatic trait) in different sexes would reflect differences in individual genetic variability, one measure of individual quality, and/or indirectly, be manifested in variation in the offspring’s early viability and growth. We created maternal half-sibling families by artificially fertilizing the eggs with milt from bright- and pale-coloured males and then held the resulting progenies under identical hatchery conditions. The expression of red coloration among parental fish was not associated with their genetic diversity estimates in either sex nor did offspring sired by bright males consistently differ in terms of embryo survival or endogenous growth efficiency from offspring sired by pale males. By contrast, maternal effects were notably strong and, additionally, the degree of female coloration was negatively linked to their reproductive potential. The more intensely coloured females had a smaller relative fecundity and they also produced offspring of lower viability, implying a significant trade-off in resource allocation between ornamentation and offspring. Our results indicate that the red breeding ornamentation of Arctic charr is likely to be informative rather among females than males when the reproductive quality is predicted on grounds of the number of offspring produced. Nevertheless, this study does not support the direct selection hypothesis in explaining the evolution of female ornamentation, but rather suggests that the less intense coloration of female charr compared to males may reflect inter-sexual differences in the trade-off between natural and sexual selection.     

Staged equilibrium of carbonic anhydrase unfolding in strong denaturants

It has been shown by 1H-NMR, circular dichroism, fluorescence and viscometry techniques that equilibrium unfolding of carbonic anhydrase B (a one-domain globular protein) in urea guanidine hydrochloride consists of two sequential stages. The first stage is connected with a decrease of intramolecular interactions, stabilizing the rigid tertiary structure and with the increase of mobility of aliphatic side chain groups. At the second stage the decrease of protein secondary structure and hydrophobic interactions take place as well as the increase of mobility of massive aromatic side chain groups.     

Morphological Response of the Halophilic Fungal Genus Wallemia to High Salinity

The basidiomycetous genus Wallemia is an active inhabitant of hypersaline environments, and it has recently been described as comprising three halophilic and xerophilic species: Wallemia ichthyophaga, Wallemia muriae, and Wallemia sebi. Considering the important protective role the fungal cell wall has under fluctuating physicochemical environments, this study was focused on cell morphology changes, with particular emphasis on the structure of the cell wall, when these fungi were grown in media with low and high salinities. We compared the influence of salinity on the morphological characteristics of Wallemia spp. by light, transmission, and focused-ion-beam/scanning electron microscopy. W. ichthyophaga was the only species of this genus that was metabolically active at saturated NaCl concentrations. W. ichthyophaga grew in multicellular clumps and adapted to the high salinity with a significant increase in cell wall thickness. The other two species, W. muriae and W. sebi, also demonstrated adaptive responses to the high NaCl concentration, showing in particular an increased size of mycelial pellets at the high salinities, with an increase in cell wall thickness that was less pronounced. The comparison of all three of the Wallemia spp. supports previous findings relating to the extremely halophilic character of the phylogenetically distant W. ichthyophaga and demonstrates that, through morphological adaptations, the eukaryotic Wallemia spp. are representative of eukaryotic organisms that have successfully adapted to life in extremely saline environments.Hypersaline habitats had long been considered to be populated almost exclusively by prokaryotic organisms and the research on hypersaline environments had consequently been monopolized by bacteriologists. In 2000, the first reports appeared showing that fungi are active inhabitants of solar salterns (20). Until then, fungi able to survive in environments with a low amount of biologically available water (low water activity [a_w]) were only known as contaminants of foods preserved with high concentrations of salt or sugar. Since their first discovery in salterns, many new species have been discovered in natural hypersaline environments around the world, including some species that were previously known only as food-borne contaminants. Due to these discoveries, fungi are now recognized as an integral part of indigenous halophilic microbial communities since they can grow and adjust across the whole salinity range, from freshwater to almost saturated NaCl solutions (49). Most fungi differ from the majority of halophilic prokaryotes (16): they tend to be extremely halotolerant rather than halophilic and do not require salt to remain viable, with the exception of Wallemia spp.The order Wallemiales (Wallemiomycetes, Basidiomycota) was only recently introduced to define the single genus Wallemia, a phylogenetic maverick in the Basidiomycota (49). Until 2005, this genus contained only the species W. sebi. However, taxonomic analyses of isolates from sweet, salty, and dried foods (41) and from hypersaline evaporation ponds in the Mediterranean Sea, the Caribbean, and the Dead Sea (45, 49) have resolved this genus into three species: W. ichthyophaga, W. muriae, and W. sebi. The first two of these three Wallemia spp. require additional solutes in the growth media, and W. ichthyophaga is the most halophilic eukaryote described to date, since it cannot grow without the addition of 9% NaCl (wt/vol), and it still shows growth at a_w of 0.77, equivalent to 30% NaCl (wt/vol) (49).The survival, and especially the growth, of microorganisms in highly saline environments requires numerous adaptations (6, 18, 21, 34). The dominant representatives and the most thoroughly investigated halophilic fungi in hypersaline waters of the salterns are the black yeasts, and particularly the model organism Hortaea werneckii (20). An important level of adaptation of the black yeasts to high salinity is seen in their extremophilic ecotype, which is characterized by a special meristematic morphology and changes in cell wall structure and pigmentation (27). Other fungal osmoadaptations include the accumulation of osmolytes (27, 28, 40), the extrusion of sodium (5), modification of the plasma membrane (44) and the cell wall, and even changes in fungal colony morphology (27).The fungal cell wall is the first line of defense against environmental stress; therefore, adaptation at the cell wall level is expected to have one of the most important roles for successful growth at a low a_w (24, 32). The cell wall is essential for maintaining the osmotic homeostasis of cells, since it protects them against mechanical damage as well as high concentrations of salts (7). The central fibrillar glycan network of the cell wall is embedded in highly flexible amorphous cement, which allows considerable stretching with changing osmotic pressure (14, 29). Its balance between a rigid and a dynamic structure influences the shape of cells (14) and enables growth and hyphal branching (11).Since the species within the genus Wallemia have been recognized only recently (49), little is known about their mechanisms of adaptation to high salinity. To investigate the effects of low and high NaCl concentrations on cell morphology, with particular emphasis on cell wall ultrastructure, we compared W. ichthyophaga, the most halophilic fungal species known thus far, with the related xerophilic W. muriae and W. sebi. Micrographs were prepared by using light, transmission, and scanning electron microscopy. The results reveal how this eukaryotic genus uses adaptations at the cell wall level for thriving in extremely saline environments.     

ARTEMIS stabilizes the genome and modulates proliferative responses in multipotent mesenchymal cells

Background  

Unrepaired DNA double-stranded breaks (DSBs) cause chromosomal rearrangements, loss of genetic information, neoplastic transformation or cell death. The nonhomologous end joining (NHEJ) pathway, catalyzing sequence-independent direct rejoining of DSBs, is a crucial mechanism for repairing both stochastically occurring and developmentally programmed DSBs. In lymphocytes, NHEJ is critical for both development and genome stability. NHEJ defects lead to severe combined immunodeficiency (SCID) and lymphoid cancer predisposition in both mice and humans. While NHEJ has been thoroughly investigated in lymphocytes, the importance of NHEJ in other cell types, especially with regard to tumor suppression, is less well documented. We previously reported evidence that the NHEJ pathway functions to suppress a range of nonlymphoid tumor types, including various classes of sarcomas, by unknown mechanisms.     

miR-155 Inhibition Sensitizes CD4+ Th Cells for TREG Mediated Suppression

Background

In humans and mice naturally occurring CD4⁺CD25⁺ regulatory T cells (nTregs) are a thymus-derived subset of T cells, crucial for the maintenance of peripheral tolerance by controlling not only potentially autoreactive T cells but virtually all cells of the adaptive and innate immune system. Recent work using Dicer-deficient mice irrevocably demonstrated the importance of miRNAs for nTreg cell-mediated tolerance.

Principal Findings

DNA-Microarray analyses of human as well as murine conventional CD4⁺ Th cells and nTregs revealed a strong up-regulation of mature miR-155 (microRNA-155) upon activation in both populations. Studying miR-155 expression in FoxP3-deficient scurfy mice and performing FoxP3 ChIP-Seq experiments using activated human T lymphocytes, we show that the expression and maturation of miR-155 seem to be not necessarily regulated by FoxP3. In order to address the functional relevance of elevated miR-155 levels, we transfected miR-155 inhibitors or mature miR-155 RNAs into freshly-isolated human and mouse primary CD4⁺ Th cells and nTregs and investigated the resulting phenotype in nTreg suppression assays. Whereas miR-155 inhibition in conventional CD4⁺ Th cells strengthened nTreg cell-mediated suppression, overexpression of mature miR-155 rendered these cells unresponsive to nTreg cell-mediated suppression.

Conclusion

Investigation of FoxP3 downstream targets, certainly of bound and regulated miRNAs revealed the associated function between the master regulator FoxP3 and miRNAs as regulators itself. miR-155 is shown to be crucially involved in nTreg cell mediated tolerance by regulating the susceptibility of conventional human as well as murine CD4⁺ Th cells to nTreg cell-mediated suppression.     

Cytotoxic activities of Hypericum perforatum L. extracts against 2D and 3D cancer cell models

Cytotechnology - Six extracts were obtained from plant species Hypericum perforatum L., collected at Samsun in Turkey. The aim of this study was to examine the mechanisms of the anticancer activity...