Sterol carrier protein-2 expression modulates protein and lipid composition of lipid droplets

Despite the critical role lipid droplets play in maintaining energy reserves and lipid stores for the cell, little is known about the regulation of the lipid or protein components within the lipid droplet. Although immunofluorescence of intact cells as well as Western analysis of isolated lipid droplets revealed that sterol carrier protein-2 (SCP-2) was not associated with lipid droplets, SCP-2 expression significantly altered the structure of the lipid droplet. First, the targeting of fatty acid and cholesterol to the lipid droplets was significantly decreased. Second, the content of several proteins important for lipid droplet function was differentially increased (perilipin A), reduced severalfold (adipose differentiation-related protein (ADRP), vimentin), or almost completely eliminated (hormone-sensitive lipase and proteins >93 kDa) in the isolated lipid droplet. Third, the distribution of lipids within the lipid droplets was significantly altered. Double labeling of cells with 12-(N-methyl)-N-[(7-nitrobenz-2-oxa-1,3-diazol-4-yl) amino]-octadecanoic acid (NBD-stearic acid) and antisera to ADRP showed that 70, 24, and 13% of lipid droplets contained ADRP, NBD-stearic acid, or both, respectively. SCP-2 expression decreased the level of ADRP in the lipid droplet but increased the proportion wherein ADRP and NBD-stearic acid colocalized by 3-fold. SCP-2 expression also decreased the lipid droplet fatty acid and cholesterol mass (nmol/mg protein) by 5.2- and 6.6-fold, respectively. Finally, SCP-2 expression selectively altered the pattern of esterified fatty acids in favor of polyunsaturated fatty acids within the lipid droplet. Displacement studies showed differential binding affinity of ADRP for cholesterol and fatty acids. These data suggested that SCP-2 and ADRP play a significant role in regulating fatty acid and cholesterol targeting to lipid droplets as well as in determining their lipid and protein components.     

The evolution and phytoplankton composition of mucilaginous aggregates in the northern Adriatic Sea

Recurrent occurrences of visible mucilage “clouds” that cover areas up to several hundred kilometres with vertical dimensions of 20–30 m have been recorded in the stratified water column in the northern Adriatic. In the past this was described as “mare sporco” phenomenon. Past studies of the phenomenon indicated that phytoplankton is an important component of mucilage. Our research revealed the composition of phytoplankton assemblages in different types of mucilaginous aggregates collected during the summers of 1997 and 2000 using pigment biomarkers (HPLC). Phytoplankton biomass in the mucilage samples was very high, ranging from 7.9 μg g⁻¹ to 390.8 μg g⁻¹ of chlorophyll a per unit of dry mass of mucilage. The phytoplankton community in the early, loose stage of mucilaginous aggregates was heterogeneous, as indicated by the diversity of detected pigments. The number of phytoplankton groups decreased as the aggregates aged and diatoms increased in relative biomass (up to 92.7%). Phytoplankton biomass in seawater was similar in years with and without mucilage; however, significantly higher contributions to the total biomass of 19′-hexanoyloxyfucoxanthin-containing phytoplankton (prymnesiophytes) were found in the upper 10 m in spring of the “mucilaginous years” (1997 and 2000) followed by prevalence of diatoms in summer. The F_p pigment index used to assess seawater trophic conditions reached lower values in April–May in mucilaginous years (1997 and 2000) compared to non-mucilaginous years (1998 and 1999). We conclude that the role of prymnesiophytes and other small flagellates is crucial for the initial phases of mucilage appearance. Aggregates represent a favourable environment for the secondary development of opportunistic diatoms that foster mucilage formation.     

固醇调节元件结合蛋白与脂质代谢

固醇调节元件结合蛋白(sterol regulatory element-binding proteins,SREBPs)是脊椎动物细胞脂质稳态的转录调节物,可直接激活多个参与胆固醇、脂肪酸、甘油三酯、磷脂合成和摄取,以及辅助因子NADPH等基因的表达,从而调控胆固醇及脂肪酸等脂类的代谢过程。本文综述了SREBPs转运和活化的过程,以及调节细胞脂质稳态功能的分子机制,并探讨了其在脂代谢紊乱相关疾病发生中的重要作用。     

Sterol composition of Candida curvata yeast

Summary Six sterols were extracted from lipids produced by Candida curvata yeast. Ergosterol (main component) and five minor compounds: ergosta-7, 24(28)-dien-3 -ol, ergosta-5, 7-dien-3 -ol, ergosta-5, 7, 9, (11), 22-tetraen-3 -ol, ergosta 7, 22-dien-3 -ol, ergost-7-en-3 -ol were identified by gas chromafography/mass spectrometry (GCMS) and quantitated by GLC.     

Sterol composition of nystatin-resistantCandida maltosa mutants

Composition of sterol fractions of nystatin-resistantCandida maltosa strains was determined. Using UV-spectrometry, TLC and GLC-MS it was demonstrated that resistance to nystatin is connected with the composition alterations of yeast cell sterols. Block of different stages of ergosterol biosynthesis was revealed in some mutants,viz. C-24-transmethylation, Δ⁸→Δ⁷, 14α-demethylation, C-5(6)-dehydrogenation, reduction of C-14(15) and C-24(28) double bonds.     

Sterol composition and the classification of the demospongiae

The Demospongiae (Porifera) have yielded a wide range of novel and conventional sterols; a sample of 55 species screened and reported on have yielded 45 distinct sterol structures. The taxonomic relevance of the occurrence of particular sterols or overall sterol complement is evaluated and has proved to be informative in the case of the Verongida, Nepheliospongida, Axinellida and Hadromerida. A possible relationship between the occurrence of 26-methyl sterols and oviparous reproductive patterns within the Ceractinomorpha is noted. Sterol complement is observed to be qualitatively stable despite season and location of collection. High molecular weight sterols, present as major components, are probable membrane constituents. They afford an interesting parallel to the occurrence of diverse, high carbon fatty acids in sponge membranes.     

Ethanol sensitivity and membrane lipid composition in three strains of mouse

Strains of mouse (Swiss OF 1, DBA/2J Ico and C57 BL/6J Ico) with different sensitivities to the hypnotic effects of acute ethanol administration were also found to have differences in fatty acid composition in synaptosomal and erythrocyte membrane phospholipids. Chronic ethanol treatment altered membrane fatty acid composition in quantitatively different ways depending on whether the mice developed tolerance (DBA, C57) or not (Swiss). These results support the hypothesis that membrane lipid composition plays a role in the sensitivity to the effects of ethanol.     

Temperature-dependent lipid content and fatty acid composition of three thermophilic bacteria

The lipid content and fatty acid composition of a strain ofBacillus caldolyticus and of two facultative thermophiles (B. flavothermus and strain NZ-2) were analysed after growth at different temperatures. In all three strains the amount of membrane, as a fraction of total cellular dry mass, was found to increase with temperature, however, in varying degrees. Changes of lipid content and protein/lipid ratio inB. caldolyticus between 60°C and 100°C and in strain NZ-2 between 45°C and 70°C were minor; inB. f avothermus the alterations in the 50°C–70°C range were more pronounced. The same was found for changes observed in the phospholipid/total lipid and phospholipid/membrane ratios, and also in the amounts of individual phospholipids. The alterations of the fatty acid composition were most significant inB. caldolyticus, especially between 80°C and 95°C. In contrast, the main changes inB. flavothermus and NZ-2 were found to occur between 30°C and 50°C, and between 45°C and 60°C, respectively. Based on these data, strain NZ-2 could be characterized as the least andB. flavothermus as the most versatile of the three organisms.     

16S rDNA clone library-based bacterial phylogenetic diversity associated with three South China Sea sponges

Culture-independent molecular techniques, 16S rDNA clone library alongside RFLP and phylogenetic analysis, were applied to investigate the bacterial diversity associated with three South China Sea sponges, Stelletta tenui, Halichondria rugosa and Dysidea avara. A wide bacterial diversity was detected according to total genomic DNA-based 16S rDNA clone library, abundant clones with low identify with sequences retrieved from database were found as well as uncultured sponge symbionts. The phylogenetic analysis shows that the bacterial community structure of Stelletta tenui is similar to that of Halichondria rugosa comprising gamma-Proteobacteria and Firmicutes. Whereas, alpha-Proteobacteria, gamma-Protebacteria, Bacteroidetes and uncultured sponge symbionts were found in sponge Dysidea avara, suggesting that Dysidea avara has the highest bacteria diversity among these sponges. A specific sponge–microbe association is suggested based on the difference of bacterial diversity among these three sponges from the same geography location and the observed sponge species-specific bacteria.     

Sterol composition of some mediterranean green algae

The distribution of sterols in ten Mediterranean green algae has been examined. Clionasterol is typical for the Siphonocladales and all the species of the Siphonales not belonging to the genus Codium, which is characterized by clerosterol. 28-Isofucosterol has been confirmed to be characteristic of the Ulotrichales.     

Invasion of amphisteginid foraminifera in the Adriatic Sea

Amphisteginid foraminifera are larger symbiont-bearing foraminifera that are abundant in tropical and subtropical reef and shelf regions of the world’s oceans. There is now unequivocal evidence that climate change has led to an expansion of tropical belts. As temperatures rise, surface isotherms are shifting poleward and habitat ranges are moving towards higher latitudes. Fueled by substantial warming, the Mediterranean has been identified as one of the most severely affected areas. This study documents for the first time that amphisteginid foraminifera have now crossed the Strait of Otranto and invaded the eastern Adriatic coast along southern Albania. Sampling on the opposite side along the southern part of the Italian boot shows, however, that amphisteginid foraminifera have not yet colonized the western coast of the Adriatic. The asymmetric invasion of the Adriatic displays spatial heterogeneity, where the progressive colonization follows the major surface currents with a northerly flow along the eastern coast and a southerly return along the western coastline. Previous sampling along Ionian Sea sample sites provides a baseline chronology allowing computations of range expansion rates. The observed recent rate of range expansion in Amphistegina is computed between 4.0 and 10 km/year^?1 and provides strong support for current species model projections. Based on the new data, the range boundary shift is projected to lead to a total northward range expansion of 5.2° latitude in the year 2100. The latitudinal range extension computed for the Mediterranean is thus almost twice as large as those computed for the southern hemisphere. The ongoing range extension into new areas of the Mediterranean Sea is shown to trigger changes in community structures with potential consequences for ecosystem functioning. Numerical abundances and impacts of invasive amphisteginids are greatest at shallow depths <20 m. Evidence is now accumulating that the invasion of amphisteginid foraminifera results in (1) a loss of benthic foraminiferal biodiversity, (2) alterations of foraminiferal community structures and (3) shifts in abundances of functional groups of foraminifera.     

Exoenzymatic activity and organic matter composition in sediments of the Northern Adriatic Sea: response to a river plume

Exoenzymatic activities (aminopeptidase and b-glucosidase) and organic matter composition were investigated in June 1996 and February 1997 in the sediment of two areas of the Adriatic Sea differently influenced by the Po river. Protein, carbohydrate, and lipid concentrations were comparable to those reported in most productive systems. Sediment chlorophyll a and biopolymeric carbon concentrations in June were twice as high as in February, but highest exoenzymatic activities and organic matter turnover rates were observed in February (with aminopeptidase activities 10 times higher than in June). The accumulation of organic matter and lower protein and carbohydrate turnover rates observed in June were the result of a different biochemical composition of organic matter in the two sampling periods. In June, organic matter was characterized by a more refractory composition. The consequent reduction of available organic substrate was associated with a decrease in the exoenzymatic substrate affinity. Lower organic matter turnover rates were also observed in deeper sediment layers. In February, the freshwater plume was almost completely confined to the northern area, whereas in June it was extended to the southern area. The results suggest that river inputs influence the biochemical composition and distribution of the sediment organic matter and exoenzymatic activities in coastal marine sediments.     

A mycological survey of the South Adriatic Sea

A total of 498 fungal isolates belonging to 33 genera and 90 species were identified in the course of a 2-yr survey of the southern part of the territoreal waters of the Yugoslav Adriatic Sea. The best represented genus was Penicillium (32.12% of the total number of isolates), the P. chrysogenumnotatum series being the most abundant, followed by P. verrucosum var. cyclopium, and P. brevicompactum The genus Aspergillus represented 22.28% of the total. A. versicolor being the most ubiquitous. The Dematiaceae as a group, with 148 isolates included in 14 genera and 26 species, accounted for 29.71% of the total; the dominant genera were Cladosporium, Alternaria, and Ulcladium, with 14 25, 5.42 and 4.21%, respectively of the total number of isolates. Hyphomycetes with hyaloconidia, with 46 isolates included in 9 genera and 20 species, constituted about 8.83%, the best represented genus in this group being Fusarium, with 10 identified species. The Sphaeropsidales accounted for 5.42% of the total number of isolates, the genus Phoma being the most abundant.The number of isolates obtained from surface waters accounted for 85% of the total. The decreasing number of isolates in the water column was particularly evident in the case of the most ubiquitous species, a fact which may be explained by the influence of the contact of water masses with the atmosphere and the lower salinity of the surface waters. The distance from the shore as well as the human factor is reflected in the number of isolates and species. The ecological factors influenced not only the fungal population densities, but also their quality.     

Sterol composition of itraconazole-resistant and itraconazole-susceptible isolates of Aspergillus fumigatus

Sterol composition of four clinical isolates of Aspergillus fumigatus resistant to itraconazole was determined by gas chromatography--mass spectrometry and compared with that of four susceptible strains. For all strains, the major sterol was ergosterol. Sterol compositions were qualitatively and quantitatively similar for the resistant and susceptible strains. These results suggest that itraconazole resistance is not related, for the strains studied, to alterations in the ergosterol synthesis pathway.     

Fatty acids of sponges from the Sea of Okhotsk

The fatty acid (FA) composition of Demospongiae species from the Sea of Okhotsk was studied. Fifteen sponge species were investigated for the first time, and the previously studied species Desmacella rosea and Myxilla incrustans were reexamined for their FA composition. Gas chromatography-mass spectrometry revealed 150 different fatty acids, of which 15 have not been identified in sponge lipids previously. The relative content of saturated FAs varied from 7.6 in Melonachora kobjakovae to 29.6% in Amphilectus digitata, with an average of 14.6% of total FAs. The relative content of monoenic FAs ranged from 12.8 in T. dirhaphis to 27.0% in Polymastia sp., with an average of 20.6% of total FAs. Non-methylen-interrupted, primarily unsaturated Δ5,9-FAs contributed a significantly to the amount of polyunsaturated fatty acids of sponges; this being a distinguishing feature of the FA composition of the investigated group of organisms.