Studies on extracellular ribonucleases of Ustilago sphaerogena. Purification and properties

1. Four ribonucleases were isolated from culture media of Ustilago sphaerogena. They were designated ribonucleases U(1), U(2), U(3) and U(4). 2. They were purified about 1600-, 3700-, 1100- and 16-fold respectively. 3. It was shown by gel filtration that ribonucleases U(1), U(2) and U(3) have molecular weights about 10000 like ribonuclease T(1), and that ribonuclease U(4) is much larger. 4. Ribonucleases U(1), U(2) and U(3) are thermostable, but ribonuclease U(4) is not. 5. The pH optimum of ribonucleases U(1) and U(4) is pH8.0-8.5, and that of ribonucleases U(2) and U(3) is pH4.5.     

Regulation of adipocytokine secretion and adipocyte hypertrophy by polymethoxyflavonoids, nobiletin and tangeretin

AimsThe polymethoxyflavonoids nobiletin and tangeretin possess several important biological properties such as neuroprotective, antimetastatic, anticancer, and anti-inflammatory properties. The present study was undertaken to examine whether nobiletin and tangeretin could modulate adipocytokine secretion and to evaluate the effects of these flavonoids on the hypertrophy of mature adipocytes.Main methodsAll experiments were performed on the murine preadipocyte cell line 3T3-L1. We studied the formation of intracellular lipid droplets in adipocytes and the apoptosis-inducing activity to evaluate the effects of polymethoxyflavonoids on adipocyte differentiation and hypertrophy, respectively. The secretion of adipocytokines was measured using ELISA.Key findingsWe demonstrated that the combined treatment of differentiation reagents with nobiletin or tangeretin differentiated 3T3-L1 preadipocytes into adipocytes possessing less intracellular triglyceride as compared to vehicle-treated differentiated 3T3-L1 adipocytes. Both flavonoids increased the secretion of an insulin-sensitizing factor, adiponectin, but concomitantly decreased the secretion of an insulin-resistance factor, MCP-1, in 3T3-L1 adipocytes. Furthermore, nobiletin was found to decrease the secretion of resistin, which serves as an insulin-resistance factor. In mature 3T3-L1 adipocytes, nobiletin induced apoptosis; tangeretin, in contrast, did not induce apoptosis, but suppressed further triglyceride accumulation.SignificanceOur results suggest that nobiletin and tangeretin are promising therapeutic candidates for the prevention and treatment of insulin resistance by modulating the adipocytokine secretion balance. We also demonstrated the different effects of nobiletin and tangeretin on mature adipocytes.     

Natural cytotoxicity of lymphocytes and monocytes and its augmentation by OK432 in melanoma patients

Summary Lymphocytes and monocytes from the peripheral blood of 30 patients with malignant melanoma were tested for natural cytotoxicity against K562 cells in a 3-h ⁵¹Cr-release assay, and the effects of OK432 (a streptococcal preparation) on the cytotoxicity were examined. The lymphocyte cytotoxicity of melanoma patients was similar to that of normal donors and control patients with benign skin disease. Furthermore, the lymphocyte cytotoxicity of melanoma patients was not correlated to the stage of the disease. Similarly, lysis of K562 cells by monocytes isolated by adherence to autologous serum-coated plastic dishes in melanoma patients was comparable to that of controls and not associated with the stage of the disease. Positive monocyte reactions were recorded in 10 of 30 (33%) melanoma patients, seven of 21 (33%) normal donors and three of 10 (30%) control patients. There was no correlation between lymphocyte cytotoxicity and monocyte cytotoxicity. Overnight treatment of monocytes and lymphocytes with OK432 resulted in an increase in cytotoxicity. Significant augmentation of cytotoxicity by OK432 was observed in 28% of the monocyte samples and 86% of the lymphocyte samples, while partially purified human interferon augmented cytotoxicity in 63% of the monocyte samples and all the lymphocyte samples. These results suggest that neither lymphocyte nor monocyte cytotoxicities are depressed in melanoma patients as compared with normal donors and patients with benign disease and that OK432 has a stronger stimulatory effect on lymphocytes than on monocytes.     

Correlation between depression of catabolite control of xylose metabolism and a defect in the phosphoenolpyruvate:mannose phosphotransferase system in Pediococcus halophilus.

Pediococcus halophilus X-160 which lacks catabolite control by glucose was isolated from nature (soy moromi mash). Wild-type strains, in xylose-glucose medium, utilized glucose preferentially over xylose and showed diauxic growth. With wild-type strain I-13, xylose isomerase activity was not induced until glucose was consumed from the medium. Strain X-160, however, utilized xylose concurrently with glucose and did not show diauxic growth. In this strain, xylose isomerase was induced even in the presence of glucose. Glucose transport activity in intact cells of strain X-160 was less than 10% of that assayed in strain I-13. Determinations of glycolytic enzymes did not show any difference responsible for the unique behavior of strain X-160, but the rate of glucose-6-phosphate formation with phosphoenolpyruvate (PEP) as a phosphoryl donor in permeabilized cells was less than 10% of that observed in the wild type. Starved P. halophilus I-13 cells contained the glycolytic intermediates 3-phosphoglycerate, 2-phosphoglycerate, and PEP (PEP pool). These were consumed concomitantly with glucose or 2-deoxyglucose uptake but were not consumed with xylose uptake. The glucose transport system in P. halophilus was identified as a PEP:mannose phosphotransferase system on the basis of the substrate specificity of PEP pool-starved cells. It is concluded that, in P. halophilus, this system is functional as a main glucose transport system and that defects in this system may be responsible for the depression of glucose-mediated catabolite control.     

Application of hyperthermophiles and their enzymes

Enzymes from hyperthermophiles display extreme (thermo)stability and a wide range of enzymes have been examined to explore their potential for various biotechnological processes. In addition, recent years have witnessed the development of genetic systems in a number of hyperthermophilic archaea. This has provided the means to initiate cell engineering studies in these organisms. Biofuel production is now an important topic in microbial biotechnology, and the hydrogen producing capabilities of (hyper)thermophiles, as well as their thermostable hydrogenases, are now attracting much attention.     

Temporal and spatial variations of lipid droplets during adipocyte division and differentiation

By capturing time-lapse images of primary stromal-vascular cells (SVCs) derived from rat mesenteric adipose tissue, we revealed temporal and spatial variations of lipid droplets (LDs) in individual SVCs during adipocyte differentiation. Numerous small LDs (a few micrometers in diameter) appeared in the perinuclear region at an early stage of differentiation; subsequently, several LDs grew to more than 10 microm in diameter and occupied the cytoplasm. We have developed a method for the fluorescence staining of LDs in living adipocytes. Time-lapse observation of the stained cells at higher magnification showed that nascent LDs (several 100 nm in diameter) grew into small LDs while moving from lamellipodia to the perinuclear region. We also found that adipocytes are capable of division and that they evenly distribute the LDs between two daughter cells. Immunofluorescence observations of LD-associated proteins revealed that such cell divisions of SVCs occurred even after LDs were coated with perilipin, suggesting that the "final" cell division during adipocyte differentiation occurs considerably later than that characterized in 3T3-L1 cells. Our time-lapse observations have provided a detailed account of the morphological changes that SVCs undergo during adipocyte division and differentiation.     

Histological and Transcriptomic Analysis of Adult Japanese Medaka Sampled Onboard the International Space Station

To understand how humans adapt to the space environment, many experiments can be conducted on astronauts as they work aboard the Space Shuttle or the International Space Station (ISS). We also need animal experiments that can apply to human models and help prevent or solve the health issues we face in space travel. The Japanese medaka (Oryzias latipes) is a suitable model fish for studying space adaptation as evidenced by adults of the species having mated successfully in space during 15 days of flight during the second International Microgravity Laboratory mission in 1994. The eggs laid by the fish developed normally and hatched as juveniles in space. In 2012, another space experiment (“Medaka Osteoclast”) was conducted. Six-week-old male and female Japanese medaka (Cab strain osteoblast transgenic fish) were maintained in the Aquatic Habitat system for two months in the ISS. Fish of the same strain and age were used as the ground controls. Six fish were fixed with paraformaldehyde or kept in RNA stabilization reagent (n = 4) and dissected for tissue sampling after being returned to the ground, so that several principal investigators working on the project could share samples. Histology indicated no significant changes except in the ovary. However, the RNA-seq analysis of 5345 genes from six tissues revealed highly tissue-specific space responsiveness after a two-month stay in the ISS. Similar responsiveness was observed among the brain and eye, ovary and testis, and the liver and intestine. Among these six tissues, the intestine showed the highest space response with 10 genes categorized as oxidation–reduction processes (gene ontogeny term GO:0055114), and the expression levels of choriogenin precursor genes were suppressed in the ovary. Eleven genes including klf9, klf13, odc1, hsp70 and hif3a were upregulated in more than four of the tissues examined, thus suggesting common immunoregulatory and stress responses during space adaptation.     

Stereochemical Configuration of 4-Hydroxy-2-nonenal-Cysteine Adducts and Their Stereoselective Formation in a Redox-regulated Protein

4-Hydroxy-2-nonenal (HNE), a major racemic product of lipid peroxidation, preferentially reacts with cysteine residues to form a stable HNE-cysteine Michael addition adduct possessing three chiral centers. Here, to gain more insight into sulfhydryl modification by HNE, we characterized the stereochemical configuration of the HNE-cysteine adducts and investigated their stereoselective formation in redox-regulated proteins. To characterize the HNE-cysteine adducts by NMR, the authentic (R)-HNE- and (S)-HNE-cysteine adducts were prepared by incubating N-acetylcysteine with each HNE enantiomer, both of which provided two peaks in reversed-phase high performance liquid chromatography (HPLC). The NMR analysis revealed that each peak was a mixture of anomeric isomers. In addition, mutarotation at the anomeric center was also observed in the analysis of the nuclear Overhauser effect. To analyze these adducts in proteins, we adapted a pyridylamination-based approach, using 2-aminopyridine in the presence of sodium cyanoborohydride, which enabled analyzing the individual (R)-HNE- and (S)-HNE-cysteine adducts by reversed-phase HPLC following acid hydrolysis. Using the pyridylamination method along with mass spectrometry, we characterized the stereoselective formation of the HNE-cysteine adducts in human thioredoxin and found that HNE preferentially modifies Cys⁷³ and, to the lesser extent, the active site Cys³². More interestingly, the (R)-HNE- and (S)-HNE-cysteine adducts were almost equally formed at Cys⁷³, whereas Cys³² exhibited a remarkable preference for the adduct formation with (R)-HNE. Finally, the utility of the method for the determination of the HNE-cysteine adducts was confirmed by an in vitro study using HeLa cells. The present results not only offer structural insight into sulfhydryl modification by lipid peroxidation products but also provide a platform for the chemical analysis of protein S-associated aldehydes in vitro and in vivo.Lipid peroxidation in tissue and in tissue fractions represents a degradative process, which is the consequence of the production and the propagation of free radical reactions primarily involving membrane polyunsaturated fatty acids and has been implicated in the pathogenesis of numerous diseases, including atherosclerosis, diabetes, cancer, and rheumatoid arthritis, as well as in drug-associated toxicity, post-ischemic reoxygenation injury, and aging (1). The peroxidative breakdown of polyunsaturated fatty acids has also been implicated in the pathogenesis of many types of liver injury and especially in the hepatic damage induced by several toxic substances. Lipid peroxidation leads to the formation of a broad array of different products with diverse and powerful biological activities. Among them is a variety of different aldehydes (2). The primary products of lipid peroxidation, lipid hydroperoxides, can undergo carbon-carbon bond cleavage via alkoxyl radicals in the presence of transition metals giving rise to the formation of short chain, unesterified aldehydes, or a second class of aldehydes still esterified to the parent lipid. These reactive aldehydic intermediates readily form covalent adducts with cellular macromolecules, including protein, leading to disruption of important cellular functions. The important agents that give rise to the modification of protein may be represented by α,β-unsaturated aldehydic intermediates, such as 2-alkenals, 4-hydroxy-2-alkenals, and 4-oxo-2-alkenals (3, 4).4-Hydroxy-2-nonenal (HNE),² among the reactive aldehydes, is a major product of lipid peroxidation and is believed to be largely responsible for the cytopathological effects observed during oxidative stress (2, 5). HNE exerts these effects because of its facile reactivity with biological materials, particularly the sulfhydryl groups of proteins. The reaction of HNE with sulfhydryl groups leads to the formation of thioether adducts that further undergo cyclization to form cyclic hemiacetals (2). Although HNE also forms Michael adducts with the imidazole moiety of histidine residues and the ϵ-amino group of lysine residues (5), the formation of thiol-derived Michael adducts, stabilized as the cyclic hemiacetal, is considered to constitute the main reactivity of HNE, because of the nucleophilic potential of the sulfhydryl group compared with those of the imidazole and amine groups. However, because of the lack of specific and reliable methods for the determination of HNE-cysteine adducts, no study has so far quantitatively demonstrated their formation in proteins.Because HNE generated in lipid peroxidation is a racemic mixture of 4R- and 4S-enantiomers (6), the HNE Michael adducts, possessing three chiral centers at C-2, C-4, and C-5 in the tetrahydrofuran moiety (Fig. 1A), are composed of at least eight isomers. In our previous study (7), we characterized the configurational isomers of an HNE-histidine adduct by NMR spectroscopy and by molecular orbital calculations, and we found that the configuration of the tetrahydrofuran ring could affect the electron delocalization features, which contribute to the stability of the adduct. Moreover, we raised monoclonal antibodies against (R)-HNE- and (S)-HNE-histidine adducts and observed differential cellular distributions of these adducts in vivo. Balogh et al. (8) recently characterized the stereochemical configurations of the HNE-glutathione adduct by NMR experiments in combination with simulated annealing structure determinations. Despite these studies, however, the stereoselectivity of the HNE Michael addition adducts generated in proteins remains to be fully explored. In this study, to gain further structural insight into sulfhydryl modification by the lipid peroxidation product, we characterized the stereochemical configuration of the HNE-N-acetylcysteine adducts by NMR spectroscopy. In addition, we adapted a pyridylamination-based method for fluorescent labeling of the HNE-cysteine adducts, using 2-aminopyridine (2-AP) and sodium cyanoborohydride (NaCNBH₃), and successfully analyzed the individual (R)-HNE- and (S)-HNE-cysteine adducts by reversed-phase HPLC following acid hydrolysis. Furthermore, using the pyridylamination method along with mass spectrometry, we characterized the stereoselective formation of the HNE-cysteine adducts in human thioredoxin (Trx).Open in a separate windowFIGURE 1.Reaction of cysteine residue with HNE. A, formation of the HNE-cysteine Michael adduct, possessing three chiral centers (asterisks). B, reaction of N-acetylcysteine with enantioisomeric HNE. The reactions were performed as described under “Experimental Procedures.” AU, absorbance units.