Construction of a eukaryotic expression system with stable and secretory expression of mycobacterium tuberculosis 38 kDa protein

The 38 kDa protein is a major antigen of mycobacterium tuberculosis and has been widely used in TB serodiagnosis, due to its highly sensitivity and specificity. Here we attempt to establish a production platform of recombinant 38 kDa protein in mammalian cells and to evaluate the potential value of 38 kDa protein in TB serodiagnosis. The 38 kDa gene is synthesized and cloned into a lentiviral expressing vector. Recombinant lentiviral vector LV-CMV-38 kDa-eGFP was packaged, titered, and then transduced into HEK 293 T cells. Recombinant cell lines were selected by limiting dilution. Supernatants were collected and purified by HisTrapTM HP column. Western blot showed a molecular weight of approximate 38 kDa in cell supernatants as expected. ELISA assay confirmed the immunological specificity of the obtained protein in the presence of MTB-infected human serum samples. In all, we have obtained a stable cell line with long-term and robust expression of secretory MTB 38 kDa protein, which may provide a promising candidate antigen for the development of TB serological diagnosis.

Structural basis of the membrane intramolecular transacylase reaction responsible for lyso-form lipoprotein synthesis

Lipoproteins serve diverse functions in the bacterial cell and some are essential for survival. Some lipoproteins are adjuvants eliciting responses from the innate immune system of the host. The growing list of membrane enzymes responsible for lipoprotein synthesis includes the recently discovered lipoprotein intramolecular transacylase, Lit. Lit creates a lipoprotein that is less immunogenic, possibly enabling the bacteria to gain a foothold in the host by stealth. Here, we report the crystal structure of the Lit enzyme from Bacillus cereus and describe its mechanism of action. Lit consists of four transmembrane helices with an extracellular cap. Conserved residues map to the cap-membrane interface. They include two catalytic histidines that function to effect unimolecular transacylation. The reaction involves acyl transfer from the sn-2 position of the glyceryl moiety to the amino group on the N-terminal cysteine of the substrate via an 8-membered ring intermediate. Transacylation takes place in a confined aromatic residue-rich environment that likely evolved to bring distant moieties on the substrate into proximity and proper orientation for catalysis.

Long-term efficacy of olipudase alfa in adults with acid sphingomyelinase deficiency (ASMD): Further clearance of hepatic sphingomyelin is associated with additional improvements in pro- and anti-atherogenic lipid profiles after 42 months of treatment

The liver is a major site of lipoprotein synthesis and metabolism. Liver manifestations of chronic visceral ASMD include hepatomegaly, fibrosis, elevated liver enzymes and a pro-atherogenic lipid profile. Measurements of sphingomyelin (SM) levels in liver biopsies and lyso-SM in plasma were used as pharmacodynamic biomarkers. Five adult patients with chronic visceral ASMD were enrolled in a 26-week phase 1b trial of enzyme replacement therapy (ERT) with olipudase alfa (NCT01722526) followed by an ongoing long-term extension study (NCT02004704). We compare the changes in hepatic SM levels, plasma lyso-SM, and lipoprotein profiles after 42 months of treatment. Progressive clearance of histologic SM storage was observed throughout the trial, along with similar reductions in plasma lyso-SM. Improvements in liver enzymes were observed at 6 months and remained stable at 42 months. Progressive reductions from baseline in pro-atherogenic lipid profiles (total cholesterol, LDL-C, VLDL-C, triglycerides) were observed at month 6 and 42. Conversely, there were progressive increases in anti-atherogenic markers, HDL-C and apolipoprotein A-I, with HDL-C increases up to 200% over baseline levels after 42 months of treatment. These data demonstrate that hepatic clearance of SM during olipudase alfa treatment over 42 months is associated with overall improvements in the lipid profiles of ASMD patients. The clinical relevance of these findings needs to be determined in the future, but we speculate that these improvements may reduce the risk for liver cirrhosis and cardiovascular disease. Trial registration: Clintrials.gov trial registration # NCT01722526.

Lipoprotein-based drug delivery

Lipoproteins (LPs) are circulating heterogeneous nanoparticles produced by the liver and intestines. LPs play a major role in the transport of dietary and endogenous lipids to target cells through cell membrane receptors or cell surface-bound lipoprotein lipase. The stability, biocompatibility, and selective transport of LPs make them promising delivery vehicles for various therapeutic and imaging agents. This review discusses isolation, manufacturing, and drug loading techniques used for LP-based drug delivery, as well as recent applications for diagnosis and treatment of cancer, atherosclerosis, and other life-threatening diseases.

POST1/C12ORF49 regulates the SREBP pathway by promoting site-1 protease maturation

Sterol-regulatory element binding proteins (SREBPs) are the key transcriptional regulators of lipid metabolism. The activation of SREBP requires translocation of the SREBP precursor from the endoplasmic reticulum to the Golgi, where it is sequentially cleaved by site-1 protease (S1P) and site-2 protease and releases a nuclear form to modulate gene expression. To search for new genes regulating cholesterol metabolism, we perform a genome-wide CRISPR/Cas9 knockout screen and find that partner of site-1 protease (POST1), encoded by C12ORF49, is critically involved in the SREBP signaling. Ablation of POST1 decreases the generation of nuclear SREBP and reduces the expression of SREBP target genes. POST1 binds S1P, which is synthesized as an inactive protease (form A) and becomes fully mature via a two-step autocatalytic process involving forms B'/B and C'/C. POST1 promotes the generation of the functional S1P-C'/C from S1P-B'/B (canonical cleavage) and, notably, from S1P-A directly (non-canonical cleavage) as well. This POST1-mediated S1P activation is also essential for the cleavages of other S1P substrates including ATF6, CREB3 family members and the α/β-subunit precursor of N-acetylglucosamine-1-phosphotransferase. Together, we demonstrate that POST1 is a cofactor controlling S1P maturation and plays important roles in lipid homeostasis, unfolded protein response, lipoprotein metabolism and lysosome biogenesis.

Lipoprotein Processing and Sorting in Helicobacter pylori

Our current understanding of lipoprotein synthesis and localization in Gram-negative bacteria is based primarily on studies of Escherichia coli Newly synthesized E. coli prolipoproteins undergo posttranslational modifications catalyzed by three essential enzymes (Lgt, LspA, and Lnt). The mature lipoproteins are then sorted to the inner or outer membrane via the Lol system (LolABCDE). Recent studies suggested that this paradigm may not be universally applicable among different classes of proteobacteria. In this study, we conducted a systematic analysis of lipoprotein processing and sorting in Helicobacter pylori, a member of the Epsilonproteobacteria that colonizes the human stomach. We show that H. pylorilgt, lspA, and lnt homologs can complement conditionally lethal E. coli mutant strains in which expression of these genes is conditionally regulated. Mutagenesis studies and analyses of conditionally lethal H. pylori mutant strains indicate that lgt and lspA are essential for H. pylori growth but lnt is dispensable. H. pylorilolA and the single lolC (or lolE) homolog are also essential genes. We then explored the role of lipoproteins in H. pylori Cag type IV secretion system (Cag T4SS) activity. Comparative analysis of the putative VirB7 homolog CagT in wild-type and lnt mutant H. pylori strains indicates that CagT undergoes amino-terminal modifications consistent with lipidation, and we show that CagT lipidation is essential for CagT stability and Cag T4SS function. This work demonstrates that lipoprotein synthesis and localization in H. pylori diverge from the canonical pathways and that lipidation of a T4SS component is necessary for H. pylori Cag T4SS activity.IMPORTANCE Bacterial lipoproteins have diverse roles in multiple aspects of bacterial physiology, antimicrobial resistance, and pathogenesis. Dedicated pathways direct the posttranslational lipidation and localization of lipoproteins, but there is considerable variation in these pathways among the proteobacteria. In this study, we characterized the proteins responsible for lipoprotein synthesis and localization in Helicobacter pylori, a member of the Epsilonproteobacteria that contributes to stomach cancer pathogenesis. We also provide evidence suggesting that lipidation of CagT, a component of the H. pylori Cag T4SS, is required for delivery of the H. pylori CagA oncoprotein into human gastric cells. Overall, these results constitute the first systematic analysis of H. pylori lipoprotein production and localization pathways and reveal how these processes in H. pylori differ from corresponding pathways in model proteobacteria.

HCV Interplay with Lipoproteins: Inside or Outside the Cells?

Hepatitis C virus (HCV) infection is a major public health issue leading to chronic liver diseases. HCV particles are unique owing to their particular lipid composition, namely the incorporation of neutral lipids and apolipoproteins. The mechanism of association between HCV virion components and these lipoproteins factors remains poorly understood as well as its impact in subsequent steps of the viral life cycle, such as entry into cells. It was proposed that the lipoprotein biogenesis pathway is involved in HCV morphogenesis; yet, recent evidence indicated that HCV particles can mature and evolve biochemically in the extracellular medium after egress. In addition, several viral, cellular and blood components have been shown to influence and regulate this specific association. Finally, this specific structure and composition of HCV particles was found to influence entry into cells as well as their stability and sensitivity to neutralizing antibodies. Due to its specific particle composition, studying the association of HCV particles with lipoproteins remains an important goal towards the rational design of a protective vaccine.

Lipoproteins: Structure, Function, Biosynthesis

The Lpp lipoprotein of Escherichia coli is the first identified protein with a covalently linked lipid. It is chemically bound by its C-terminus to murein (peptidoglycan) and inserts by the lipid at the N-terminus into the outer membrane. As the most abundant protein in E. coli (10⁶ molecules per cell) it plays an important role for the integrity of the cell envelope. Lpp represents the type protein of a large variety of lipoproteins found in Gram-negative and Gram-positive bacteria and in archaea that have in common the lipid structure for anchoring the proteins to membranes but otherwise strongly vary in sequence, structure, and function. Predicted lipoproteins in known prokaryotic genomes comprise 2.7% of all proteins. Lipoproteins are modified by a unique phospholipid pathway and transferred from the cytoplasmic membrane into the outer membrane by a special system. They are involved in protein incorporation into the outer membrane, protein secretion across the cytoplasmic membrane, periplasm and outer membrane, signal transduction, conjugation, cell wall metabolism, antibiotic resistance, biofilm formation, and adhesion to host tissues. They are only found in bacteria and function as signal molecules for the innate immune system of vertebrates, where they cause inflammation and elicit innate and adaptive immune response through Toll-like receptors. This review discusses various aspects of Lpp and other lipoproteins of Gram-negative and Gram-positive bacteria and archaea.

C-reactive protein levels are inversely correlated with the apolipoprotein B-48-containing triglyceride-rich lipoprotein production rate in insulin resistant men

The pro-inflammatory state and elevated plasma levels of post-prandial triglycerides (TG) are associated with increased cardiovascular disease risk. Recent studies suggested that the increase in the production rate of post-prandial lipoproteins observed in patients with insulin resistance (IR) may be caused, at least in part, by the dysregulation of intestinal insulin sensitivity triggered by inflammation.

OBJECTIVE

The objective of the present study was to evaluate the association between IR, plasma C-reactive protein (CRP) levels and the kinetics of TG-rich lipoprotein (TRL) containing apolipoprotein (apo) B-48 in a large sample of insulin sensitive (IS) and IR men.

METHODS

The in vivo kinetics of TRL apoB-48 were measured in 151 men following a primed-constant infusion of l-[5,5,5-D₃]leucine. IR subjects (n=91) were characterized by fasting TG levels ≥1.5mmol/L and an index of homeostasis model assessment of IR (HOMA-IR)≥2.5 or type 2 diabetes, while IS subjects (n=24) were characterized by an HOMA-IR index <2.5 and TG levels <1.5mmol/L.

RESULTS

IR subjects had higher TRL apoB-48 production rate (+202%; P<0.0001) and CRP levels (+51%; P=0.01) than IS subjects. TRL apoB-48 production rate and CRP levels were inversely correlated in IR subjects (r=-0.32; P=0.002). IR subjects with CRP levels above the median (2.20mg/L) had lower TRL apoB-48 production rate than IR subjects with CRP levels below the median (Δ=-24%; P<0.05).

CONCLUSION

Our results confirm that IR is associated with increased TRL apoB-48 secretion and suggest that a higher inflammatory status is associated with decreased TRL apoB-48 secretion among IR subjects.

Global and hepatocyte-specific ablation of Bmal1 induces hyperlipidaemia and enhances atherosclerosis

Circadian rhythms controlled by clock genes affect plasma lipids. Here we show that global ablation of Bmal1 in Apoe-/- and Ldlr-/- mice and its liver-specific ablation in Apoe-/- (L-Bmal1-/-Apoe-/-) mice increases, whereas overexpression of BMAL1 in L-Bmal1-/-Apoe-/- and Apoe-/-mice decreases hyperlipidaemia and atherosclerosis. Bmal1 deficiency augments hepatic lipoprotein secretion and diminishes cholesterol excretion to the bile. Further, Bmal1 deficiency reduces expression of Shp and Gata4. Reductions in Shp increase Mtp expression and lipoprotein production, whereas reductions in Gata4 diminish Abcg5/Abcg8 expression and biliary cholesterol excretion. Forced SHP expression normalizes lipoprotein secretion with no effect on biliary cholesterol excretion, while forced GATA4 expression increases cholesterol excretion to the bile and reduces plasma lipids in L-Bmal1-/-Apoe-/- and Apoe-/- mice. Thus, our data indicate that Bmal1 modulates lipoprotein production and biliary cholesterol excretion by regulating the expression of Mtp and Abcg5/Abcg8 via Shp and Gata4.

The Journey of Lipoproteins Through the Cell: One Birthplace, Multiple Destinations

Bacterial lipoproteins are a very diverse group of proteins characterized by the presence of an N-terminal lipid moiety that serves as a membrane anchor. Lipoproteins have a wide variety of crucial functions, ranging from envelope biogenesis to stress response. In Gram-negative bacteria, lipoproteins can be targeted to various destinations in the cell, including the periplasmic side of the cytoplasmic or outer membrane, the cell surface or the external milieu. The sorting mechanisms have been studied in detail in Escherichia coli, but exceptions to the rules established in this model bacterium exist in other bacteria. In this chapter, we will present the current knowledge on lipoprotein sorting in the cell. Our particular focus will be on the surface-exposed lipoproteins that appear to be much more common than previously assumed. We will discuss the different targeting strategies, provide numerous examples of surface-exposed lipoproteins and discuss the techniques used to assess their surface exposure.

Effect of Spermidine Analogues on Cell Growth of Escherichia coli Polyamine Requiring Mutant MA261

The effects of spermidine analogues [norspermidine (NSPD, 33), spermidine (SPD, 34), homospermidine (HSPD, 44) and aminopropylcadaverine (APCAD, 35)] on cell growth were studied using Escherichia coli polyamine-requiring mutant MA261. Cell growth was compared at 32°C, 37°C, and 42°C. All four analogues were taken up mainly by the PotABCD spermidine-preferential uptake system. The degree of stimulation of cell growth at 32°C and 37°C was NSPD ≥ SPD ≥ HSPD > APCAD, and SPD ≥ HSPD ≥ NSPD > APCAD, respectively. However, at 42°C, it was HSPD » SPD > NSPD > APCAD. One reason for this is HSPD was taken up effectively compared with other triamines. In addition, since natural polyamines (triamines and teteraamines) interact mainly with RNA, and the structure of RNA is more flexible at higher temperatures, HSPD probably stabilized RNA more tightly at 42°C. We have thus far found that 20 kinds of protein syntheses are stimulated by polyamines at the translational level. Among them, synthesis of OppA, RpoE and StpA was more strongly stimulated by HSPD at 42°C than at 37°C. Stabilization of the initiation region of oppA and rpoE mRNA was tighter by HSPD at 42°C than 37°C determined by circular dichroism (CD). The degree of polyamine stimulation of OppA, RpoE and StpA synthesis by NSPD, SPD and APCAD was smaller than that by HSPD at 42°C. Thus, the degree of stimulation of cell growth by spermidine analogues at the different temperatures is dependent on the stimulation of protein synthesis by some components of the polyamine modulon.

Immunostimulation by phospholipopeptide biosurfactant from Staphylococcus hominis in Oreochromis mossambicus

The immunostimulatory effect of phospholipopeptide biosurfactant from Staphylococcus hominis (GenBank Accession No: KJ564272) was assessed with Oreochromis mossambicus. The non-specific (serum lysozyme activity, serum antiprotease activity, serum peroxidase activity and serum bactericidal activity), specific (bacterial agglutination assay) immune responses and disease resistance activity against Aeromonas hydrophila were examined. Fish were intraperitonially injected with water soluble secondary metabolite (biosurfactant) of S. hominis at a dose of 2 mg, 20 mg and 200 mg kg(-1) body weight. Commercial surfactant surfactin (sigma) at 20 mg kg(-1) was used as standard and saline as negative control. All the doses of water soluble biosurfactant tested, significantly enhanced the specific, nonspecific immunity and disease resistance from the day of post administration of phospholipopeptide biosurfactant till the tail of the experimental period. These results clearly indicated that the secondary metabolite isolated from S. hominis stimulates the immunity of finfish thereby could enhance aquaculture production.

LXR-Mediated ABCA1 Expression and Function Are Modulated by High Glucose and PRMT2

High cholesterol and diabetes are major risk factors for atherosclerosis. Regression of atherosclerosis is mediated in part by the Liver X Receptor (LXR) through the induction of genes involved in cholesterol transport and efflux. In the context of diabetes, regression of atherosclerosis is impaired. We proposed that changes in glucose levels modulate LXR-dependent gene expression. Using a mouse macrophage cell line (RAW 264.7) and primary bone marrow derived macrophages (BMDMs) cultured in normal or diabetes relevant high glucose conditions we found that high glucose inhibits the LXR-dependent expression of ATP-binding cassette transporter A1 (ABCA1), but not ABCG1. To probe for this mechanism, we surveyed the expression of a host of chromatin-modifying enzymes and found that Protein Arginine Methyltransferase 2 (PRMT2) was reduced in high compared to normal glucose conditions. Importantly, ABCA1 expression and ABCA1-mediated cholesterol efflux were reduced in Prmt2^-/- compared to wild type BMDMs. Monocytes from diabetic mice also showed decreased expression of Prmt2 compared to non-diabetic counterparts. Thus, PRMT2 represents a glucose-sensitive factor that plays a role in LXR-mediated ABCA1-dependent cholesterol efflux and lends insight to the presence of increased atherosclerosis in diabetic patients.

Cyclic Lipopeptide Biosynthetic Genes and Products, and Inhibitory Activity of Plant-Associated Bacillus against Phytopathogenic Bacteria

The antibacterial activity against bacterial plant pathogens and its relationships with the presence of the cyclic lipopeptide (cLP) biosynthetic genes ituC (iturin), bmyB (bacillomycin), fenD (fengycin) and srfAA (surfactin), and their corresponding antimicrobial peptide products have been studied in a collection of 64 strains of Bacillus spp. isolated from plant environments. The most frequent antimicrobial peptide (AMP) genes were bmyB, srfAA and fenD (34-50% of isolates). Most isolates (98.4%) produced surfactin isoforms, 90.6% iturins and 79.7% fengycins. The antibacterial activity was very frequent and generally intense among the collection of strains because 75% of the isolates were active against at least 6 of the 8 bacterial plant pathogens tested. Hierarchical and correspondence analysis confirmed the presence of two clearly differentiated groups. One group consisted of Bacillus strains that showed a strong antibacterial activity, presented several cLPs genes and produced several isoforms of cLPs simultaneously, mainly composed of B. subtilis and B. amyloliquefaciens, although the last one was exclusive to this group. Another group was characterized by strains with very low or none antibacterial activity, that showed one or none of the cLP genes and produced a few or none of the corresponding cLPs, and was the most heterogenous group including B. subtilis, B. licheniformis, B. megaterium, B. pumilus, B. cereus and B. thuringiensis, although the last two were exclusive to this group. This work demonstrated that the antagonistic capacity of plant-associated Bacillus against plant pathogenic bacteria is related to the presence of cLP genes and to the production of the corresponding cLPs, and it is mainly associated to the species B. subtilis and B. amyloliquefaciens. Our findings would help to increase the yield and efficiency of screening methods to obtain candidate strains to biocontrol agents with a mechanism of action relaying on the production of antimicrobial cLPs.

Transcriptional characteristics associated with lichenysin biosynthesis in Bacillus licheniformis from Chinese Maotai-flavor liquor making

This work investigated the biosynthetic mechanism of lichenysin, the newly identified nonvolatile matrix component in Chinese liquors. Transcriptomes were analyzed in three producers, Bacillus licheniformis CGMCC 3961, 3962, and 3963, which were isolated from Maotai-flavor liquor-making process and produced 386.3, 553.5, and 795.2 μg/L lichenysin in a simulative liquor fermentation process. Lichenysin synthetase genes lchAA-AD in these three producers were expressed much more highly than those of the nonproducer B. licheniformis ATCC 14580 (>18.4-fold). In addition, ABC transporters were the most significant responsive metabolic pathway, and the expression levels of peptide transporter genes dppABCDE all increased more than 19.2-fold. When B. licheniformis CGMCC 3963 was cultured in synthetic medium, the expression of dppABCDE and lichenysin both increased with the addition of casein hydrolysate (containing various peptides). This indicated that peptide would act as a substrate for lichenysin synthesis. This work sheds new light on the mechanism for lichenysin biosynthesis.

Hepatic lipogenesis and a marker of hepatic lipid oxidation, predict postprandial responses of triglyceride-rich lipoproteins

OBJECTIVE

Postprandial hypertriglyceridemia is an important risk factor for cardiovascular disease. The mechanisms are still unclear. Here it was tested if hepatic de novo lipogenesis (DNL) and lipid oxidation influence the postprandial responses of triglyceride-rich lipoproteins (TRL) in humans.

METHODS

The contribution of hepatic DNL to hepatic TRL production was analyzed in 67 men and women with a moderate range of BMI after a fat-rich meal. Also, lipase activities, liver fat, and 3-OH-butyrate were quantitated as an indicator of β-oxidation. Lipoproteins and metabolic markers were measured in fasting and postprandial blood samples.

RESULTS

Postprandial DNL correlates with postprandial TG and apolipoprotein (apo) C-III responses in plasma and with TG, apoB48 and apoB100 responses in TRLs and their larger remnant particles. Fasting and 8-h postprandial DNL was inversely related to 3-OH-butyrate but not to liver fat content. Fasting apoC-III and 3-OH-butyrate, but not liver fat, independently predicted fasting DNL.

CONCLUSIONS

The fasting and 8-h postprandial rate of DNL was inversely associated with the hepatic lipid oxidation in humans. DNL contributes significantly to the TG content in TRLs but not to the amount of liver fat, suggesting that an imbalance between DNL and fat oxidation contributes to postprandial atherogenic dyslipidemia.

Surfactin Isoforms from Bacillus coagulans

Bacillus coagulans has been found to produce several surfactins that are powerful lipopeptide surfactants. Four main components with molecular weights 1007, 1021 and 1035 Da were separated. Their structures have been confirmed by spectrometric and spectroscopic studies and by acid hydrolysis. The compounds were found to represent two pairs of surfactin isoforms in which β-hydroxy-iso-C14 or anteiso-C15 fatty acids are linked to the [Leu7] or [Val7] heptapeptide moiety by both an amide group and a lactone bond.

BMP4 enhances foam cell formation by BMPR-2/Smad1/5/8 signaling

Atherosclerosis and its complications are characterized by lipid-laden foam cell formation. Recently, an obvious up-regulation of BMP4 was observed in atherosclerotic plaque, however, its function and the underlying mechanism remains unknown. In our study, BMP4 pretreatment induced macrophage foam cell formation. Furthermore, a dramatic increase in the ratio of cholesteryl ester (CE) to total cholesterol (TC) was observed in BMP4-treated macrophages, accompanied by the reduction of cholesterol outflow. Importantly, BMP4 stimulation inhibited the expression levels of the two most important cellular cholesterol transporters ABCA1 and ABCG1, indicating that BMP4 may induce formation of foam cells by attenuating transporters expression. Further mechanism analysis showed that BMPR-2, one of the BMP4 receptors, was significantly increased in BMP4 treated macrophage foam cells. That blocking its expression using specific siRNA significantly increased ABCA1 and ABCG1 levels. Additionally, BMP4 treatment triggered the activation of Smad1/5/8 pathway by BMPR-2 signaling. After blocking the Smad1/5/8 with its inhibitor, ABCA1 and ABCG1 expression levels were up-regulated significantly, suggesting that BMP4 inhibited the expression of ABCA1 and ABCG1 through the BMPR-2/Smad1/2/8 signaling pathway. Therefore, our results will provide a new insight about how BMP4 accelerate the progressio of atherosclerosis, and it may become a potential target against atherosclerosis and its complications.

[Modification of fatty acid composition of polar and neutral lipids of blood and liver in rat in conditions of prolonged high-fat diet]

Studied the composition of fatty acids of polar and neutral lipids of plasma, erythrocytes and liver Wistar rats under prolonged high-fat diet. It was established that during long-term (90-180 days) in rats high-fat load is blocking the cells ligand-retseptor active capture polyunsaturated fatty acids (PUFAs) in the low-density lipoprotein (LDL). This is confirmed by the accumulation of blood in LDL cholesterol and lipid fractions, esterified n-3 and n-6 PUFA (triacylglycerides, sterols esters, phospholipids), while the deficit these same fatty acids in the lipids of erythrocytes. In the liver under the influence of prolonged high-fat diet increased pool monoenic (18:1 n-9) and polyunsaturated (20:5 n-3, 20:3 n-6, 22:5 n-3) fatty acids. These data suggest that prolonged exposure of rats high-fat diet contributes to compensatory de novo synthesis of fatty acids in the liver. However, due to violations of the receptor active transport of fatty acids synthesized in the liver fatty acids are not captured by cells of the peripheral organs. Identified data allow us to expand the understanding of the role of nutritional factors in the physiology and pathophysiology of the cell, modulation of lipid metabolism.

Production of a novel mixture of mycosubtilins by mutants of Bacillus subtilis

Using promoter exchange and gene knock-out strategies, two mutant strains, the so-called BBG116 and BBG125, were constructed from Bacillus subtilis wild-type strain ATCC 6633, a surfactin and mycosubtilin producer. Compared to the parental strain, both mutants overproduced constitutively mycosubtilin, while BBG125 had lost the ability to synthesize surfactin. Surprisingly, BBG125 was found to produce about 2-fold less mycosubtilin than BBG116 despite an expected higher availability of the cytoplasmic precursors and cofactors pool for biosynthesis. Further physiological characterization of BBG125 also highlighted: (i) a strong influence of temperature on mycosubtilin biosynthesis in BBG125 with a maximal productivity observed at 22°C, compared to 15 and 30°C; (ii) substantial changes in fatty acid profiles and thereby in mycosubtilin isoforms, compared to the wild-type strain; and (iii) the presence of five novel mycosubtilin isoforms. The antifungal activities of the new mix were higher than or equal to those of purified isoforms.

ILDR2: an endoplasmic reticulum resident molecule mediating hepatic lipid homeostasis

Ildr2, a modifier of diabetes susceptibility in obese mice, is expressed in most organs, including islets and hypothalamus, with reduced levels in livers of diabetes-susceptible B6.DBA mice congenic for a 1.8 Mb interval of Chromosome 1. In hepatoma and neuronal cells, ILDR2 is primarily located in the endoplasmic reticulum membrane. We used adenovirus vectors that express shRNA or are driven by the CMV promoter, respectively, to knockdown or overexpress Ildr2 in livers of wild type and ob/ob mice. Livers in knockdown mice were steatotic, with increased hepatic and circulating triglycerides and total cholesterol. Increased circulating VLDL, without reduction in triglyceride clearance suggests an effect of reduced hepatic ILDR2 on hepatic cholesterol clearance. In animals that overexpress Ildr2, hepatic triglyceride and total cholesterol levels were reduced, and strikingly so in ob/ob mice. There were no significant changes in body weight, energy expenditure or glucose/insulin homeostasis in knockdown or overexpressing mice. Knockdown mice showed reduced expression of genes mediating synthesis and oxidation of hepatic lipids, suggesting secondary suppression in response to increased hepatic lipid content. In Ildr2-overexpressing ob/ob mice, in association with reduced liver fat content, levels of transcripts related to neutral lipid synthesis and cholesterol were increased, suggesting “relief” of the secondary suppression imposed by lipid accumulation. Considering the fixed location of ILDR2 in the endoplasmic reticulum, we investigated the possible participation of ILDR2 in ER stress responses. In general, Ildr2 overexpression was associated with increases, and knockdown with decreases in levels of expression of molecular components of canonical ER stress pathways. We conclude that manipulation of Ildr2 expression in liver affects both lipid homeostasis and ER stress pathways. Given these reciprocal interactions, and the relatively extended time-course over which these studies were conducted, we cannot assign causal primacy to either the effects on hepatic lipid homeostasis or ER stress responses.

GLP-1 and GLP-2 as yin and yang of intestinal lipoprotein production: evidence for predominance of GLP-2-stimulated postprandial lipemia in normal and insulin-resistant states

The glucagon-like peptides (GLP-1 and GLP-2) are processed from the proglucagon polypeptide and secreted in equimolar amounts but have opposite effects on chylomicron (CM) production, with GLP-1 significantly reducing and GLP-2 increasing postprandial chylomicronemia. In the current study, we evaluated the apparent paradoxical roles of GLP-1 and GLP-2 under physiological conditions in the Syrian golden hamster, a model with close similarity to humans in terms of lipoprotein metabolism. A short (30-min) intravenous infusion of GLP-2 resulted in a marked increase in postprandial apolipoprotein B48 (apoB48) and triglyceride (TG) levels in the TG-rich lipoprotein (TRL) fraction, whereas GLP-1 infusion decreased lipid absorption and levels of TRL-TG and apoB48. GLP-1 and GLP-2 coinfusion resulted in net increased lipid absorption and an increase in TRL-TG and apoB48. However, prolonged (120-min) coinfusion of GLP-1 and GLP-2 decreased postprandial lipemia. Blocking dipeptidyl peptidase-4 activity resulted in decreased postprandial lipemia. Interestingly, fructose-fed, insulin-resistant hamsters showed a more pronounced response, including possible hypersensitivity to GLP-2 or reduced sensitivity to GLP-1. In conclusion, under normal physiological conditions, the actions of GLP-2 predominate; however, when GLP-1 activity is sustained, the hypolipidemic action of GLP-1 predominates. Pharmacological inhibition of GLP-1 degradation tips the balance toward an inhibitory effect on intestinal production of atherogenic CM particles.

Lecithin:cholesterol acyltransferase deficiency protects against cholesterol-induced hepatic endoplasmic reticulum stress in mice

We recently reported that lecithin:cholesterol acyltransferase (LCAT) knock-out mice, particularly in the LDL receptor knock-out background, are hypersensitive to insulin and resistant to high fat diet-induced insulin resistance (IR) and obesity. We demonstrated that chow-fed Ldlr-/-xLcat+/+ mice have elevated hepatic endoplasmic reticulum (ER) stress, which promotes IR, compared with wild-type controls, and this effect is normalized in Ldlr-/-xLcat-/- mice. In the present study, we tested the hypothesis that hepatic ER cholesterol metabolism differentially regulates ER stress using these models. We observed that the Ldlr-/-xLcat+/+ mice accumulate excess hepatic total and ER cholesterol primarily attributed to increased reuptake of biliary cholesterol as we observed reduced biliary cholesterol in conjunction with decreased hepatic Abcg5/g8 mRNA, increased Npc1l1 mRNA, and decreased Hmgr mRNA and nuclear SREBP2 protein. Intestinal NPC1L1 protein was induced. Expression of these genes was reversed in the Ldlr-/-xLcat-/- mice, accounting for the normalization of total and ER cholesterol and ER stress. Upon feeding a 2% high cholesterol diet (HCD), Ldlr-/-xLcat-/- mice accumulated a similar amount of total hepatic cholesterol compared with the Ldlr-/-xLcat+/+ mice, but the hepatic ER cholesterol levels remained low in conjunction with being protected from HCD-induced ER stress and IR. Hepatic ER stress correlates strongly with hepatic ER free cholesterol but poorly with hepatic tissue free cholesterol. The unexpectedly low ER cholesterol seen in HCD-fed Ldlr-/-xLcat-/- mice was attributable to a coordinated marked up-regulation of ACAT2 and suppressed SREBP2 processing. Thus, factors influencing the accumulation of ER cholesterol may be important for the development of hepatic insulin resistance.

Intracellular cholesterol-binding proteins enhance HDL-mediated cholesterol uptake in cultured primary mouse hepatocytes

A major gap in our knowledge of rapid hepatic HDL cholesterol clearance is the role of key intracellular factors that influence this process. Although the reverse cholesterol transport pathway targets HDL to the liver for net elimination of free cholesterol from the body, molecular details governing cholesterol uptake into hepatocytes are not completely understood. Therefore, the effects of sterol carrier protein (SCP)-2 and liver fatty acid-binding protein (L-FABP), high-affinity cholesterol-binding proteins present in hepatocyte cytosol, on HDL-mediated free cholesterol uptake were examined using gene-targeted mouse models, cultured primary hepatocytes, and 22-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-amino]-23,24-bisnor-5-cholen-3β-ol (NBD-cholesterol). While SCP-2 overexpression enhanced NBD-cholesterol uptake, counterintuitively, SCP-2/SCP-x gene ablation also 1) enhanced the rapid molecular phase of free sterol uptake detectable in <1 min and initial rate and maximal uptake of HDL free cholesterol and 2) differentially enhanced free cholesterol uptake mediated by the HDL3, rather than the HDL2, subfraction. The increased HDL free cholesterol uptake was not due to increased expression or distribution of the HDL receptor [scavenger receptor B1 (SRB1)], proteins regulating SRB1 [postsynaptic density protein (PSD-95)/Drosophila disk large tumor suppressor (dlg)/tight junction protein (ZO1) and 17-kDa membrane-associated protein], or other intracellular cholesterol trafficking proteins (steroidogenic acute response protein D, Niemann Pick C, and oxysterol-binding protein-related proteins). However, expression of L-FABP, the single most prevalent hepatic cytosolic protein that binds cholesterol, was upregulated twofold in SCP-2/SCP-x null hepatocytes. Double-immunogold electron microscopy detected L-FABP sufficiently close to SRB1 for direct interaction, similar to SCP-2. These data suggest a role for L-FABP in HDL cholesterol uptake, a finding confirmed with SCP-2/SCP-x/L-FABP null mice and hepatocytes. Taken together, these results suggest that L-FABP, particularly in the absence of SCP-2, plays a significant role in HDL-mediated cholesterol uptake in cultured primary hepatocytes.

Evaluation and comparison of native and recombinant LipL21 protein-based ELISAs for diagnosis of bovine leptospirosis

A 21-kDa leptospiral lipoprotein (LipL21) was evaluated for its diagnostic potential to detect bovine leptospirosis by ELISA. Both native LipL21 (nLipL21) and recombinant LipL21 (rLipL21) proteins were tested and compared regarding diagnostic efficiency, and no statistically significant difference was observed. The sensitivity of rLipL21 ELISA for 62 microscopic agglutination test (MAT) positive sera was 100% and the specificity with 378 MAT negative sera was 97.09%. Thus, rLipL21 protein-based ELISA could be used as an alternative to MAT for the diagnosis of bovine leptospirosis.

[All signs of metabolic syndrome in the hypertensive ISIAH rats are associated with increased activity of transcription factors PPAR, LXR, PXR, and CAR in the liver]

It is known that the metabolic syndrome (MS), which includes hypertension, dislipidemia, glucose intolerance, and obesity leads to cardiovascular diseases. The MS risk is growing catastrophically. Molecular mechanisms allowing to understand the reason of integrated dysfunctions, taking place at MS cases, have remained almost unstudied. The chronical stress plays a crucial role in MS development; therefore in the present work a hypertensive rat strain with Inherited Stress-Induced Arterial Hypertension (ISIAH) was used as a model. It was shown that ISIAH rat strain as compared with the control WAG rat strain is characterized by increased content of triglyceride, VLDL and LDL cholesterols, a decreased content of HDL cholesterol, a high level of apolipoprotein B-100, and decreased level of apolipoprotein A-I. The ISIAH rats body weight was higher as compared with WAG rats; ISIAH rats blood glucose content was higher too. Thus, strain hypertension for ISIAH rat is accompanied by dislipidemia, increased glucose content, and increased body weight, representing a whole set of MS signs. Since at MS cases the systemic abnormalities in lipid and carbohydrate metabolism take place, the functional activity of transcription factors (TFs) participating in integral regulation of lipid and carbohydrate metabolism genes in liver was measured. PPAR, LXR, PXR, CAR DNA-binding activity was increased in ISIAH rats, suggesting involvement of these TFs in MS development. Integrated investigation of PPAR, LXR, PXR, CAR regulatory mechanisms, signal transduction and transcriptional targets will provide insights into the pathogenesis of MS and offer valuable information for designing of drugs for MS treatment.

Construction of prokaryotic expression plasmid of mtrC protein of Neisseria gonorrhoeae and its expression in E. coli

In order to provide a rational research basis for detection of resistance of Neisseria gonorrhoeae to antimicrobial hydrophobic agents and study on the resistant mechanism of multiple transferable resistance (mtr) efflux system, plasmid pET-28a(+) encoding mtrC gene was constructed and the related target protein was expressed in Escherichia coli (E. coli) DE3. The fragments of mtrC gene of Neisseria gonorrhoeae from the standard strains were amplified and cloned into prokaryotic expression plasmid pET-28a(+) with restriction endonuclease to construct recombinant pET-mtrC which was verified by restriction endonuclease and DNA sequencing. The recombinant was transformed into E. coli DE3 to express the protein mtrC induced by IPTG. The results showed mtrC DNA fragment was proved correct through restriction endonuclease and DNA sequencing. Its sequence was 99.5% homologus to that published on GeneBank (U14993). A 48.5 kD fusion protein which was induced by IPTG was detected by SDS-PAGE. It was concluded that the construction of prokaryotic expression plasmid of mtrC protein of Neisseria gonorrhoeae was correct and the fusion protein was successively expressed in E. coli.

Mitogen-activated protein kinases pathway is involved in physiological testosterone-induced tissue factor pathway inhibitor expression in endothelial cells

The mechanism of testosterone inducing the tissue factor pathway inhibitor (TFPI) in protecting against thrombosis is unknown. We aimed to elucidate the mechanisms involved in the induction by observing, in human umbilical vein endothelial cells (HUVECs), the phosphorylation of mitogen-activated protein kinases (MAPKs), a major cell signaling system. The level of testosterone regulating several signaling pathways, including extracellular signal-regulated kinases 1/2 (ERK1/2), c-Jun-N-terminal kinase (JNK), and p38 MAPK, was measured by western blot in HUVECs. ELISA and quantitative real-time reverse transcriptase-PCR were used to analyze TFPI expression after blocking ERK1/2 (with PD98059) or JNK (with SP600125) pathway in HUVECs. Testosterone-induced a rapid phosphorylation of ERK1/2, JNK and p38 MAPK in HUVECs, which could not be inhibited by androgen receptor antagonist flutamide. Blocking ERK1/2 or JNK pathway could significantly impair testosterone-induced TFPI at both translational and transcriptional levels in HUVECs. Testosterone at a physiological concentration may help to prevent thrombosis development by stimulating TFPI expression in HUVECs, partly through the ERK1/2 and JNK MAPK pathway.

[Immunobiological properties of recombinant L peptide from the Pseudomonas aeruginosa outer membrane]

The gene encoding plasma membrane protein L (OprL) was cloned and expressed in E. coli. It was shown that the recombinant protein had immunogenic properties and protected laboratory animals from experimental P. aeruginosa infection. Rabbit hyperimmune sera raised against recombinant L protein possessed antimicrobial activity and prevented infection with P. aeruginosa.

[Obtaining of outer membrane protein I of Pseudomonas aeruginosa and assessment of its antigenic properties]

Gene of outer membrane protein I (OprI) of Pseudomonas aeruginosa was cloned in Escherichia coli cells. Synthesized protein OprI contained additional sequence of 6 histidines on the N-terminus, which allowed its chromatographic purification in Ni-agarose. Obtained recombinant ptotein specifically reacted with hyperimmune rabbit serum against whole-cell P. aeruginosa and stimulated synthesis of specific antibodies in immunized mice and rabbits. Obtained hyperimmune rabbit sera against recombinant protein OprI had directive antimicrobial activity against P. aeruginosa.

[Prokaryotic expression of trigeminy artificial fusion gene of Leptospira interrogans and the immunogenicity of its products]

OBJECTIVE

To construct lipL32/1-lipL21-OmpL1/2 fusion gene of Leptospira interrogans and its prokaryotic expression system, and to identify the immunogenicity of its products.

METHODS

PCR using linking primers was applied to construct lipL32/1-lipL21-OmpL1/2 fusion gene and a prokaryotic expression system of the fusion gene was then established using routine genetic engineering technique. SDS-PAGE was used to examine output of the target recombinant protein rLipL32/1-LipL21-OmpL1/2. Double immunodiffusion and Western Blot assay were applied to identify immunogenicity of rLipL32/1-LipL21-OmpL1/2.

RESULT

lipL32/1-lipL21-OmpL1/2 fusion gene with correct sequence and its prokaryotic expression system E.coli BL21DE3pET42a-lipL32/1-lipL21-ompL1/2 was obtained in this study. The output of rLipL32/1-LipL21- OmpL1/2 after optimisation was 37.78 mg/L. The immunodiffusion titer of rabbit antiserum against rLipL32/1-LipL21-OmpL1/2 was 1:4. The rLipL32/1-LipL21-OmpL1/2 antiserum was able to recognize rLipL32/1-LipL21-OmpL1/2, rLipL32/1, rLipL21 and rOmpL1/2. Positive Western hybridization signals were found among rLipL32/1-LipL21-OmpL1/2 and rabbit antiserum against whole cell of strain 56601 and serum from patients infected with L.interrogans serogroups Icterohaemorrhagiae, Grippotyphosa, Autumnalis and Pomona.

CONCLUSION

The fusion gene lipL32/1-lipL21-OmpL1/2 and its prokaryotic expression system were successfully constructed in this study. The expressed fusion protein can be used as the antigen for developing universal genetic engineering vaccine and universal serological tests of leptospirosis.

Intestinal lipoprotein overproduction in insulin-resistant states

PURPOSE OF REVIEW

Excessive postprandial lipemia is highly prevalent in obese and insulin-resistant/type 2 diabetic individuals and substantially increases the risk of atherosclerosis and cardiovascular disease. This article will review our current understanding of the link between insulin resistance and intestinal lipoprotein overproduction and highlight some of the key recent findings in the field.

RECENT FINDINGS

Emerging evidence from several animal models of insulin resistance as well as insulin-resistant humans clearly supports the link between insulin resistance and aberrant intestinal lipoprotein metabolism. In insulin-resistant states, elevated free fatty acid flux into the intestine, downregulation of intestinal insulin signaling and upregulation of microsomal triglyceride transfer protein all appear to stimulate intestinal lipoprotein production. Gut peptides, GLP-1 and GLP-2, may be important regulators of intestinal lipid absorption and lipoprotein production.

SUMMARY

Available evidence in humans and animal models strongly favors the concept that the small intestine is not merely an absorptive organ but rather plays an active role in regulating the rate of production of triglyceride-rich lipoproteins. Metabolic signals in insulin resistance and type 2 diabetes and in some cases an aberrant intestinal response to these factors all contribute to the enhanced formation and secretion of triglyceride-rich lipoproteins.

Dissociation between the insulin-sensitizing effect of rosiglitazone and its effect on hepatic and intestinal lipoprotein production

CONTEXT

Despite its potent, well-documented insulin-sensitizing effects, rosiglitazone (RSG) does not effectively ameliorate the hypertriglyceridemia of insulin-resistant or diabetic individuals and has even been shown to slightly but significantly increase triglyceride-rich lipoproteins (TRL) in some studies. The mechanism of this effect is currently not known.

OBJECTIVE

We investigated the effect of RSG treatment on TRL metabolism.

DESIGN

This was a 12-wk, single-sequence, cross-over study of rosiglitazone vs. placebo for 6 wk.

PARTICIPANTS

Participants included 17 nondiabetic men with a broad range of insulin sensitivity.

INTERVENTION

INTERVENTION included rosiglitazone 8 mg/d vs. placebo for 6 wk.

MAIN OUTCOME MEASURE

TRL metabolism (concentration, production and catabolic rates) was assessed in a constant fed state with a 12-h primed constant infusion of [D3]l-leucine and multicompartmental modeling.

RESULTS

RSG treatment resulted in significant insulin sensitization with no change in body weight. Fasting plasma triglyceride (TG) concentration, however, was higher with RSG vs. placebo (P = 0.0006), as were fasting and fed TRL-TG, TRL-apoB-48, and TRL-apoB-100 (fed TRL-apoB-48: 0.93 +/- 0.08 vs. 0.76 +/- 0.07 mg/dl, P =0.017, and fed TRL-apoB-100: 15.57 +/- 0.90 vs. 13.71 +/- 1.27 mg/dl, P = 0.029). This small but significant increase in plasma TRL concentration was explained by a tendency for RSG to increase TRL production and reduce particle clearance, as indicated by the significantly increased production to clearance ratios for both apoB-48-containing (0.43 +/- 0.03 vs. 0.34 +/- 0.03, P = 0.048) and apoB-100-containing (7.0 +/- 0.4 vs. 6.2 +/- 0.6, P = 0.029) TRL.

CONCLUSION

These data indicate dissociation between the insulin-sensitizing effects of RSG and absence of anticipated reductions in production rates of apoB-100- and apoB-48-containing-TRL particles, which may explain the absence of TG lowering seen in humans treated with this agent.

[Recombinant plasmid constructed and cytotoxicity studied for outer membrane protein LipL32 gene of Leptospira strain 017]

OBJECTIVE

To construct the recombinant plasmid containing the outer membrane protein LipL32 gene of Leptospira strain 017 and to study on the cytotoxicity of the expression protein.

METHODS

By the polymerase chain reaction (PCR), the LipL32 gene was amplified from Leptospira strain 017 genome and cloned into pET32a(+) with enzyme digestion, then used to transform E. coli JM109. After induced with IPTG, the target protein was expressed and used to immunize New zealand white rabbit. Western Blotting identified the immunogenicity of the expressed protein. Then the purified and renatured protein was acted on ECV304 cell so as to get its cytotoxicity detected by examining the LDH and NO (nitrogen monoxide) release from cell.

RESULTS

The full length of the LipL32 gene about 816 bp was obtained by PCR. The recombinant plasmid was identified by enzyme digestion, PCR and DNA sequencing. After induced with IPTG, the expressed protein existed mainly in the form of inclusion bodies about 52 x 10(3) (relative molecular mass) which was consistent with the expected size of the fused protein. After rabbit immunity, the titre of the produced multiclonal antibody reached 1 : 32 000 measured by ELISA. Western Blotting analysis found a positive band specifically in the target protein position. The release of the LDH and NO of the ECV304 cell treated with LipL32 had significant increase compared with the control group.

CONCLUSION

The recombinant plasmid containing LipL32 gene is successfully constructed and can express the target protein in E. coli JM109. The expressed target protein has cytotoxicity.

Both intestinal and hepatic lipoprotein production are stimulated by an acute elevation of plasma free fatty acids in humans

BACKGROUND

Hepatic lipoprotein production has been shown previously to be regulated by free fatty acid (FFA) flux to the liver, whereas intestinal lipoprotein production is stimulated mainly by ingested fat absorbed from the intestinal lumen. Emerging evidence indicates that intestinal lipoprotein production is increased in insulin resistance and type 2 diabetes mellitus, conditions that are associated with increased levels of circulating FFAs. Here we investigated whether short-term elevation of plasma FFAs stimulates intestinal apolipoprotein (apo) B-48- and hepatic apoB-100-containing triglyceride-rich lipoprotein (TRL) production in humans in the fed state.

METHODS AND RESULTS

TRL apoB-48 and apoB-100 metabolism were examined in 12 healthy men during a constant fed state. The studies were as follows, respectively: (1) Intralipid/heparin was infused intravenously immediately before and during the kinetics study to induce an approximately 3-fold difference in plasma FFA compared with the saline study; (2) saline was infused intravenously as a control. ApoB-48- and apoB-100-containing TRL production and clearance were determined with a 12-hour primed constant infusion of [D3]L-leucine and multicompartmental kinetic modeling. TRL apoB-48 production rate was 69% higher in the Intralipid/heparin study than in the saline control (5.95+/-1.13 versus 3.53+/-0.58 mg/kg per day; P=0.027), and there was no significant difference in TRL apoB-48 clearance. TRL apoB-100 concentrations were also increased (P<0.001) and TRL apoB-100 production rate was 35% higher in the Intralipid/heparin study compared with saline (28+/-4 versus 21+/-3 mg/kg per day; P=0.020).

CONCLUSIONS

This is the first study to demonstrate that intestinal TRL apoB-48 production is increased after short-term elevation of plasma FFAs in humans in the fed state, similar to the well-described stimulation of hepatic TRL apoB100-containing particles by FFAs.

Decreased post-prandial triglyceride response and diminished remnant lipoprotein formation in cholesteryl ester transfer protein (CETP) deficiency

Plasma cholesteryl ester transfer protein (CETP) mediates CE/TG exchange among various lipoproteins. CETP deficiency results in low LDL and high HDL phenotype including apoE-rich large HDL. Large HDL could provide apoE to chylomicron/VLDL during lipolysis in post-prandial state, accelerating remnant lipoprotein uptake in the liver. To determine the effects of low CETP levels on post-prandial lipoprotein metabolism, lipid levels of plasma remnant-like lipoprotein particles (RLP) fraction were determined in one homozygous and three heterozygous CETP deficiency and controls with apoE3/3 phenotype. After oral fat-load, the area under curve (AUC) of TG levels were remarkably decreased in CETP deficiency as compared to controls (423+/-187 [S.D.] mg/dl x h in three heterozygous CETP deficiency and 926+/-268 [S.D.] in 10 controls, P=0.012). Similarly, the homozygote had a low AUC of TG levels (416 mg/dl x h). Plasma RLP-cholesterol levels were decreased in heterozygotes, but not significantly as compared to controls (P=0.14). HPLC analysis showed that increased RLP-cholesterol level was not due to conventional VLDL-LDL size RLP, but to those in large HDL size in the homozygote. In heterozygotes, bimodal distribution of RLP-cholesterol level was found in lipoprotein sizes of conventional VLDL-LDL and large HDL. Subjects with CETP deficiency appeared to have low levels of TG response and diminished remnant lipoprotein formation after fat-load.

Biogenesis of the gram-negative bacterial outer membrane

The cell envelope of gram-negative bacteria consists of two membranes, the inner and the outer membrane, that are separated by the periplasm. The outer membrane consists of phospholipids, lipopolysaccharides, integral membrane proteins, and lipoproteins. These components are synthesized in the cytoplasm or at the inner leaflet of the inner membrane and have to be transported across the inner membrane and through the periplasm to assemble eventually in the correct membrane. Recent studies in Neisseria meningitidis and Escherichia coli have led to the identification of several machineries implicated in these transport and assembly processes.

Regulated synthesis of the Borrelia burgdorferi inner-membrane lipoprotein IpLA7 (P22, P22-A) during the Lyme disease spirochaete's mammal-tick infectious cycle

Results of previous immunological studies suggested that Borrelia burgdorferi regulates synthesis of the IpLA7 lipoprotein during mammalian infection. Through combined use of quantitative reverse transcription PCR, immunofluorescence analyses, ELISA and immunoblotting, it is now demonstrated that IpLA7 is actually expressed throughout mammalian infection, as well as during transmission both from feeding ticks to naïve mice and from infected mice to naïve, feeding ticks. However, proportions of IpLA7-expressing B. burgdorferi within tick midguts declined significantly with time following completion of blood feeding. Cultured bacteria differentially expressed IpLA7 in response to changes in temperature, pH and concentration of 4,5-dihydroxy-2,3-pentanedione, the precursor of autoinducer 2, indicative of mechanisms governing IpLA7 expression. Previous studies also reported mixed results as to the cellular localization of IpLA7. It is now demonstrated that IpLA7 localizes primarily to the borrelial inner membrane and is not surface-exposed, consistent with the ability of these bacteria to produce IpLA7 throughout mammalian infection despite being the target of a robust immune response.

Stereospecific Enzymatic Transformation of α-Ketoglutarate to (2S,3R)-3-Methyl Glutamate during Acidic Lipopeptide Biosynthesis

The acidic lipopeptides, including the calcium-dependent antibiotics (CDA), daptomycin, and A54145, are important macrocyclic peptide natural products produced by Streptomyces species. All three compounds contain a 3-methyl glutamate (3-MeGlu) as the penultimate C-terminal residue, which is important for bioactivity. Here, biochemical in vitro reconstitution of the 3-MeGlu biosynthetic pathway is presented, using exclusively enzymes from the CDA producer Streptomyces coelicolor. It is shown that the predicted 3-MeGlu methyltransferase GlmT and its homologues DptI from the daptomycin producer Streptomyces roseosporus and LptI from the A54145 producer Streptomyces fradiae do not methylate free glutamic acid, PCP-bound glutamate, or Glu-containing CDA in vitro. Instead, GlmT, DptI, and LptI are S-adenosyl methionine (SAM)-dependent alpha-ketoglutarate methyltransferases that catalyze the stereospecific methylation of alpha-ketoglutarate (alphaKG) leading to (3R)-3-methyl-2-oxoglutarate. Subsequent enzyme screening identified the branched chain amino acid transaminase IlvE (SCO5523) as an efficient catalyst for the transformation of (3R)-3-methyl-2-oxoglutarate into (2S,3R)-3-MeGlu. Comparison of reversed-phase HPLC retention time of dabsylated 3-MeGlu generated by the coupled enzymatic reaction with dabsylated synthetic standards confirmed complete stereocontrol during enzymatic catalysis. This stereospecific two-step conversion of alphaKG to (2S,3R)-3-MeGlu completes our understanding of the biosynthesis and incorporation of beta-methylated amino acids into the nonribosomal lipopeptides. Finally, understanding this pathway may provide new possibilities for the production of modified peptides in engineered microbes.

Insect lipoprotein biogenesis depends on an amphipathic β cluster in apolipophorin II/I and is stimulated by microsomal triglyceride transfer protein

Lipoproteins transport lipids in the circulation of an evolutionally wide diversity of animals. The pathway for lipoprotein biogenesis has been revealed to a large extent in mammals only, in which apolipoprotein B (apoB) acquires lipids via the assistance of microsomal triglyceride transfer protein (MTP) and binds them by means of amphipathic protein structures. To investigate whether this is a common mechanism for lipoprotein biogenesis in animals, we studied the structural elements involved in the assembly of the insect lipoprotein, lipophorin. LOCATE sequence analysis predicted that the insect lipoprotein precursor, apolipophorin II/I (apoLp-II/I), contains clusters of amphipathic alpha-helices and beta-strands, organized along the protein as N-alpha(1)-beta-alpha(2)-C, reminiscent of a truncated form of apoB. Recombinant expression of a series of C-terminal truncation variants of Locusta migratoria apoLp-II/I in an insect cell (Sf9) expression system revealed that the formation of a buoyant high density lipoprotein requires the amphipathic beta cluster. Coexpression of apoLp-II/I with the MTP homolog of Drosophila melanogaster affected insect lipoprotein biogenesis quantitatively as well as qualitatively, as the secretion of apoLp-II/I proteins was increased several-fold and the buoyant density of the secreted lipoprotein decreased concomitantly, indicative of augmented lipidation. Based on these findings, we propose that, despite specific modifications, the assembly of lipoproteins involves MTP as well as amphipathic structures in the apolipoprotein carrier, both in mammals and insects. Thus, lipoprotein biogenesis in animals appears to rely on structural elements that are of early metazoan origin.

Lipoprotein synthesis in mycobacteria

Lipoproteins are a functionally diverse class of secreted bacterial proteins characterized by an N-terminal lipid moiety. The lipid moiety serves to anchor these proteins to the cell surface. Lipoproteins are synthesized as pre-prolipoproteins and mature by post-translational modifications. The post-translational modifications are directed by the lipobox motif located within the signal peptide. Enzymes involved in lipoprotein synthesis are essential in Gram-negative bacteria but not in Gram-positive bacteria. Inactivation of genes involved in lipoprotein synthesis attenuates a variety of Gram-positive pathogens, including Mycobacterium tuberculosis. The attenuated phenotype of these mutants indicates an important role of lipoproteins and lipoprotein synthesis in bacterial virulence. M. tuberculosis, the causative agent of tuberculosis, is one of the most devastating pathogens in the world. This article reviews recent findings on the synthesis, localization and function of lipoproteins in mycobacteria.

Setting up and modelling of overflowing fed-batch cultures of Bacillus subtilis for the production and continuous removal of lipopeptides

This work is related to the set-up of overflowing exponential fed-batch cultures (O-EFBC) derived from carbon limited EFBC dedicated to the production of mycosubtilin, an antifungal lipopeptide belonging to the iturin family. O-EFBC permits the continuous removal of the product from the bioreactor achieving a complete extraction of mycosubtilin. This paper also provides a dynamical Monod-based growth model of this process that is accurate enough to simulate the evolution of the specific growth rate and to correlate it to the mycosubtilin specific productivity. Two particular and dependant phenomena related to the foam overflow are taken into account by the model: the outgoing flow rate of a broth volume and the loss of biomass. Interestingly, the biomass concentration in the foam was found to be lower than the biomass concentration in the bioreactor relating this process to a recycling one. Parameters of this model are the growth yield on substrate and the maximal specific growth rate estimated from experiments led at feed rates of 0.062, 0.071 and 0.086h(-1). The model was extrapolated to five additional experiments carried out at feed rates of 0.008, 0.022, 0.040, 0.042 and 0.062h(-1) enabling the correlation of the mean specific growth rates with productivity results. Finally, a feed rate of 0.086h(-1) corresponding to a mean specific growth rate of 0.070h(-1) allowed a specific productivity of 1.27mg of mycosubtiling(-1) of dried biomassh(-1).

Molecular and biochemical detection of fengycin- and bacillomycin D-producing Bacillus spp., antagonistic to fungal pathogens of canola and wheat

Bacillus species are well known for their ability to control plant diseases through various mechanisms, including the production of secondary metabolites. Bacillus subtilis DFH08, an antagonist of Fusarium graminearum , and other Bacillus spp. that are antagonists of common fungal pathogens of canola were screened for peptide synthetase biosynthetic genes of fengycin and bacillomycin D. Specific polymerase chain reaction (PCR) primers identified B. subtilis strains DFH08 and 49 for the presence of the fenD gene of the fengycin operon. Bacillus cereus DFE4, Bacillus amyloliquefaciens strains DFE16 and BS6, and B. subtilis 49 were identified for the presence of the bamC gene of the bacillomycin D synthetase biosynthetic operon. Both fengycin and bacillomycin D were detected in the culture extract of strain Bs49, characterized through MALDI–TOF–MS (matrix-assisted laser desorption ionization – time of flight – mass spectrometry), and their antifungal activities demonstrated against F. graminearum and Sclerotinia sclerotiorum . This study designed and used specific PCR primers for the detection of potential fengycin- and bacillomycin D-producing bacterial antagonists and confirmed the molecular detection with the biochemical detection of the corresponding antibiotic produced. This is also the first report of a B. cereus strain (DFE4) to have bacillomycin D biosynthetic genes. Bacteria that synthesize these lipopeptides could act as natural genetic sources for genetic engineering of the peptide synthetases for production of novel peptides.

Identification of a biosynthetic gene cluster and the six associated lipopeptides involved in swarming motility of Pseudomonas syringae pv. tomato DC3000

Pseudomonas species are known to be prolific producers of secondary metabolites that are synthesized wholly or in part by nonribosomal peptide synthetases. In an effort to identify additional nonribosomal peptides produced by these bacteria, a bioinformatics approach was used to "mine" the genome of Pseudomonas syringae pv. tomato DC3000 for the metabolic potential to biosynthesize previously unknown nonribosomal peptides. Herein we describe the identification of a nonribosomal peptide biosynthetic gene cluster that codes for proteins involved in the production of six structurally related linear lipopeptides. Structures for each of these lipopeptides were proposed based on amino acid analysis and mass spectrometry analyses. Mutations in this cluster resulted in the loss of swarming motility of P. syringae pv. tomato DC3000 on medium containing a low percentage of agar. This phenotype is consistent with the loss of the ability to produce a lipopeptide that functions as a biosurfactant. This work gives additional evidence that mining the genomes of microorganisms followed by metabolite and phenotypic analyses leads to the identification of previously unknown secondary metabolites.

Production of mouse monoclonal antibodies against Helicobacter pylori Lpp20 and mapping the antigenic epitope by phage display library

Lpp20, an outer membrane protein of Helicobacter pylori (H. pylori), has been identified as an immunodominant antigen. To obtain mouse monoclonal antibodies (mAbs) against it and to map its antigenic epitope is potentially to develop a vaccine for prevention and treatment of H. pylori infection. In our study, the Lpp20 gene was obtained from H. pylori genomic DNA by PCR (GenBank accession no. DQ106902), cloned into pGEX-4T-1 vector and expressed in Escherichia coli (E. coli) as a recombinant fusion protein with glutathione-S-transferase (GST), which was purified by GST-affinity chromatography. mAbs were produced by the hybridoma technique using Lpp20-GST as the immunogen. Using mAb as the target molecule and immunoscreening phage-displayed random dodecapeptide library (Ph.D.-12), the positive phage clones were sequenced and analyzed. Phage clones were chosen to immunize mice to evaluate the potential of phagotopes as effective vaccines. One mimotope (SWPLYSDASGLG) showed a good match with the Lpp20 proteins at 114-117aa (DASG) and the serum of mice induced by the phage clone clearly recognized Lpp20 protein. Our work suggests that the antigenic epitope could be mapped through screening the phage-displayed peptide libraries with mAb and a mimotope of Lpp20 providing an alternative approach for the diagnosis and development of a vaccine for H. pylori.

Reduced expression of alpha-tocopherol-associated protein is associated with tumor cell proliferation and the increased risk of prostate cancer recurrence

AIM

To examine the impact and prognostic significance of alpha-tocopherol associated protein (TAP) expression in a series of prostate cancer patients.

METHODS

Tissues from 87 patients underwent radical prostatectomy were examined for TAP expression by immunohistochemistry. The relationships of the staining results, the clinic pathological characteristics and the recurrence times were analyzed.

RESULTS

Compared with the adjacent areas of normal and benign glands, immunoreactivity of TAP was reduced in areas of prostate cancer. A lower TAP-positive cell number per mm(2) of the largest cancer area (defined as TAP-PN) was associated with higher clinical stage (r = -0.248, P = 0.0322). Inverse associations were found among the TAP-PN and positive lymph nodes (r = -0.231, P = 0.0325), preoperative prostate-specific antigen (PSA) levels (r = -0.423, P = 0.0043), tumor size (r= -0.315, P= 0.0210) and elevated tumor cell proliferation, which was indicated by the staining of Ki-67 (r = -0.308, P = 0.0026). TAP-PN was a significant predictor of recurrence univariately (P = 0.0006), as well as multivariately, adjusted for known markers including preoperative PSA, clinical stage, Gleason score, surgical margin, extra-prostatic extension, seminal vesicle invasion and lymph node metastasis (P = 0.0012).

CONCLUSION

Reduced expression of TAP was associated with the cell proliferation status of prostate cancer, adverse pathological parameters and the increased risk of recurrence.

E-cadherin is a receptor for the common protein pneumococcal surface adhesin A (PsaA) of Streptococcus pneumoniae

Streptococcus pneumoniae (Pnc) binds to nasopharyngeal (NP) epithelial cells in the first steps of nasopharyngeal carriage and colonization through bacterial adhesins. The pneumococcal surface adhesin A (PsaA) has previously been reported to play a significant role in pneumococcal adherence and colonization. Identification of a receptor for PsaA on human epithelium will aid in understanding the pathogenesis of this bacterium. Using recombinant PsaA covalently bound to fluorescent spheres (fluospheres), we show PsaA binds to NP cells through interaction with the human cellular receptor, E-cadherin. SDS-PAGE silver stain analysis demonstrates binding of PsaA to E-cadherin. Recombinant human E-cadherin binds to and blocks PsaA-coated fluospheres and whole transparent bacteria from adhering to NP cells, but does not block a Pnc PsaA(-) mutant. Recombinant E-selectin and human alpha(5)beta(1) integrin did not bind to or block PsaA-coated fluosphere adherence to NP cells. Likewise, if NP cells were preincubated with anti-E-cadherin antibody, there was a significant decrease (46%, P=0.05) in PsaA-coated fluosphere adherence to the cells. Additionally, when using E-cadherin transfected cells, we observed PsaA-coated fluospheres bind more efficiently to cells which express E-cadherin. This work identifies E-cadherin as a receptor on human epithelial cells for the pneumococcal surface adhesin, PsaA.

[Optimization of microbial synthesis of recombinant analogs of Treponema pallidum membrane proteins (Tpp17 and Tpp47) and estimation of their immunochemical properties]

Two strains which produce recombinant proteins--analogs of membrane immunodominant epitopes with molecular weights 17 and 47 kDa of Treponema pallidum were constructed on the basis of E. coli recipient BL21 (DE3)-Gold with phage T7RNA-polymerase expression system. The method of mathematical modeling of growth curve was used to determine kinetic parameters which characterized physiological state of the culture producer in the process of fermentation. Results of immunoenzymatic analysis of blood serum samples from patients with syphilis and healthy donors are presented.