Synthesis and biological activity of new 5-O-sugar modified ketolide and 2-fluoro-ketolide antibiotics

A series of new triazole-containing ketolides and 2-fluoro-ketolides in which the 5-O-desosamine was replaced by unnatural sugars were synthesized and evaluated against relevant macrolide-sensitive and macrolide-resistant respiratory pathogens. Excellent in vitro antibacterial activities were demonstrated for ketolide analogues having the 6'-OBz-3'-dimethylamino-glucose and 6'-OBz-4'-deoxy-3'-dimethylamino-glucose substituents.     

Evolutionary rate heterogeneity in proteins with long disordered regions

The dominant view in protein science is that a three-dimensional (3-D) structure is a prerequisite for protein function. In contrast to this dominant view, there are many counterexample proteins that fail to fold into a 3-D structure, or that have local regions that fail to fold, and yet carry out function. Protein without fixed 3-D structure is called intrinsically disordered. Motivated by anecdotal accounts of higher rates of sequence evolution in disordered protein than in ordered protein we are exploring the molecular evolution of disordered proteins. To test whether disordered protein evolves more rapidly than ordered protein, pairwise genetic distances were compared between the ordered and the disordered regions of 26 protein families having at least one member with a structurally characterized region of disorder of 30 or more consecutive residues. For five families, there were no significant differences in pairwise genetic distances between ordered and disordered sequences. The disordered region evolved significantly more rapidly than the ordered region for 19 of the 26 families. The functions of these disordered regions are diverse, including binding sites for protein, DNA, or RNA and also including flexible linkers. The functions of some of these regions are unknown. The disordered regions evolved significantly more slowly than the ordered regions for the two remaining families. The functions of these more slowly evolving disordered regions include sites for DNA binding. More work is needed to understand the underlying causes of the variability in the evolutionary rates of intrinsically ordered and disordered protein.     

Inhibition of mammalian legumain by Michael acceptors and AzaAsn-halomethylketones

Legumain is a lysosomal cysteine peptidase specific for an asparagine residue in the P1-position. It has been classified as a member of clan CD peptidases due to predicted structural similarities to caspases and gingipains. So far, inhibition studies on legumain are limited by the use of endogenous inhibitors such as cystatin C. A series of Michael acceptor inhibitors based on the backbone Cbz-L-Ala-L-Ala-L-Asn (Cbz= benzyloxycarbonyl) has been prepared and resulted in an irreversible inhibition of porcine legumain. Variation of the molecular size within the 'war head' revealed the best inhibition for the compound containing the allyl ester (kobs/I=766 M(-1) s(-1)). To overcome cyclisation between the amide moiety of the Asn residue and the 'war head', several asparagine analogues have been synthesised. Integrated in halomethylketone inhibitors, azaasparagine is accepted by legumain in the P1-position. The most potent inhibitor of this series, Cbz-L-Ala-L-Ala-AzaAsn-chloromethylketone, displays a k(obs)/I value of 139,000 M(-1) s(-1). Other cysteine peptidases, such as papain and cathepsin B, are not inhibited by this compound at concentrations up to 100 microM. The synthetic inhibitors described here represent useful tools for the investigation of the structural and physiological properties of this unique asparagine-specific peptidase.     

The docosatriene protectin D1 is produced by TH2 skewing and promotes human T cell apoptosis via lipid raft clustering

Docosahexaenoic acid, a major omega-3 fatty acid in human brain, synapses, retina, and other neural tissues, displays beneficial actions in neuronal development, cancer, and inflammatory diseases by mechanisms that remain to be elucidated. In this study we found, using lipid mediator informatics employing liquid chromatography-tandem mass spectrometry, that (10,17S)-docosatriene/neuroprotectin D1, now termed protectin D1 (PD1), is generated from docosahexaenoic acid by T helper type 2-skewed peripheral blood mononuclear cells in a lipoxygenase-dependent manner. PD1 blocked T cell migration in vivo, inhibited tumor necrosis factor alpha and interferon-gamma secretion, and promoted apoptosis mediated by raft clustering. These results demonstrated novel anti-inflammatory roles for PD1 in regulating events associated with inflammation and resolution.     

Stereoselective determination of methadone and the primary metabolite EDDP in human plasma by automated on-line extraction and liquid chromatography mass spectrometry

A sensitive stereoselective bioanalytical liquid chromatographic assay with mass spectrometric detection (LC-MS) was developed and validated for the on-line extraction and quantification of R- and S-methadone and the primary metabolite R- and S-2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) from human plasma. Deproteinized plasma was injected directly onto a small C8 column, washed and then back-flushed using a column switching valve and a second pump onto an alpha1-acid glycoprotein analytical column, and enantioselective separation achieved using a mobile phase gradient of methanol and ammonium formate. Analytes were validated over a range of 0.1-25 ng/ml R- and S-EDDP and 0.1-100ng/ml R- and S-methadone, respectively. Unweighted standard curves were linear over this concentration range (regression coefficients > 0.999). Quality control samples were evaluated at 1, 5, 12.5 ng/ml R- and S-EDDP and 1, 10, 50 ng/ml R- and S-methadone. Intra- and inter-day accuracy was >95%, and intra- and inter-day coefficients of variation were less than 10% for all analytes and concentrations. This assay represents the only method currently available which combines on-line extraction and achieves chiral separation of both methadone and EDDP from plasma, and offers improvements in sensitivity over existing methods.     

Measurement of Apolipoprotein E (apoE) in Cerebrospinal Fluid

Apolipoprotein E (apoE) is a protein involved in transport of lipids and has been implicated to play an important role in regeneration after nerve injury. Determination of apoE in cerebrospinal fluid (CSF) thus have a potential interest when studying different forms of brain damage and as a marker of ongoing regenerative processes in the brain. However, previous studies on CSF-ApoE in Alzheimer's disease (AD) have given inconclusive results. Such inconsistant results might be related to confounding factors interfering with sample handling and/or analyses, which have not been fully elucidated. We therefore examined different potential confounding factors for analyses of apoE in CSF and also developed a new enzyme linked immunosorbent assay (ELISA). The hydrophobic character of ApoE resulted in adsorbtion to different types of test tubes commonly used for collection of CSF at lumbar puncture, resulting in falsly low levels. This makes CSF handling critical, especially if samples are taken in different types of tubes, or is transferred to new tubes. Taking this confounding factors in consideration and analysing patient and control CSF handled in the same way and using the new ELISA, we could confirm our previous finding of reduced levels of ApoE in AD, (3.4 ± 1.3mg/l) compared with controls (4.5 ± 2.7mg/l) (p = 0.045). Both in the AD and in the control group, higher levels of CSF-ApoE was found in individuals possessing the ApoE4 alleles. Our results support that CSF-ApoE is reduced in AD, and that handling of CSF is a critical factor, which may explain the discrepant results from previous studies. Differences in the amount of patients and controls possessing the ApoE4 allele included might also increase the variance between different studies.     

Trends in the knowledge, attitudes and practices of travel risk groups towards prevention of malaria: results from the Dutch Schiphol Airport Survey 2002 to 2009

ABSTRACT: BACKGROUND: Previous studies investigating the travellers' knowledge, attitudes and practices (KAP) profile indicated an important educational need among those travelling to risk destinations. Initiatives to improve such education should target all groups of travellers, including business travellers, those visiting friends and relatives (VFRs), and elderly travellers. METHODS: In the years 2002 to 2009, a questionnaire-based survey was conducted at the Dutch Schiphol Airport with the aim to study trends in KAP of travel risk groups towards prevention of malaria. The risk groups last-minute travellers, solo-travellers, business travellers, VFRs and elderly travellers were specifically studied. RESULTS: A total of 3,045 respondents were included in the survey. Travellers to destinations with a high risk for malaria had significantly more accurate risk perceptions (knowledge) than travellers to low-risk destinations. The relative risk for malaria in travellers to high-risk destinations was probably mitigated by higher protection rates against malaria as compared with travellers to low risk destinations. There were no significant differences in intended risk-taking behaviour. Trend analyses showed a significant change over time in attitude towards more risk-avoiding behaviour and towards higher protection rates against malaria in travellers to high-risk destinations. The KAP profile of last-minute travellers substantially increased their relative risk for malaria, which contrasts to the slight increase in relative risk of solo travellers, business travellers and VFRs for malaria. CONCLUSIONS: The results of this sequential cohort survey in Dutch travellers suggest an annual 1.8% increase in protection rates against malaria coinciding with an annual 2.5% decrease in intended risk-seeking behaviour. This improvement may reflect the continuous efforts of travel health advice providers to create awareness and to propagate safe and healthy travel. The KAP profile of last-minute travellers, in particular, substantially increased their relative risk for malaria, underlining the continuous need for personal protective measures and malaria chemoprophylaxis for this risk group.     

The yeast homologue of the microtubule-associated protein Lis1 interacts with the sumoylation machinery and a SUMO-targeted ubiquitin ligase

Microtubules and microtubule-associated proteins are fundamental for multiple cellular processes, including mitosis and intracellular motility, but the factors that control microtubule-associated proteins (MAPs) are poorly understood. Here we show that two MAPs—the CLIP-170 homologue Bik1p and the Lis1 homologue Pac1p—interact with several proteins in the sumoylation pathway. Bik1p and Pac1p interact with Smt3p, the yeast SUMO; Ubc9p, an E2; and Nfi1p, an E3. Bik1p interacts directly with SUMO in vitro, and overexpression of Smt3p and Bik1p results in its in vivo sumoylation. Modified Pac1p is observed when the SUMO protease Ulp1p is inactivated. Both ubiquitin and Smt3p copurify with Pac1p. In contrast to ubiquitination, sumoylation does not directly tag the substrate for degradation. However, SUMO-targeted ubiquitin ligases (STUbLs) can recognize a sumoylated substrate and promote its degradation via ubiquitination and the proteasome. Both Pac1p and Bik1p interact with the STUbL Nis1p-Ris1p and the protease Wss1p. Strains deleted for RIS1 or WSS1 accumulate Pac1p conjugates. This suggests a novel model in which the abundance of these MAPs may be regulated via STUbLs. Pac1p modification is also altered by Kar9p and the dynein regulator She1p. This work has implications for the regulation of dynein''s interaction with various cargoes, including its off-loading to the cortex.     

Open Field Release of Genetically Engineered Sterile Male Aedes aegypti in Malaysia

Background

Dengue is the most important mosquito-borne viral disease. In the absence of specific drugs or vaccines, control focuses on suppressing the principal mosquito vector, Aedes aegypti, yet current methods have not proven adequate to control the disease. New methods are therefore urgently needed, for example genetics-based sterile-male-release methods. However, this requires that lab-reared, modified mosquitoes be able to survive and disperse adequately in the field.

Methodology/Principal Findings

Adult male mosquitoes were released into an uninhabited forested area of Pahang, Malaysia. Their survival and dispersal was assessed by use of a network of traps. Two strains were used, an engineered ‘genetically sterile’ (OX513A) and a wild-type laboratory strain, to give both absolute and relative data about the performance of the modified mosquitoes. The two strains had similar maximum dispersal distances (220 m), but mean distance travelled of the OX513A strain was lower (52 vs. 100 m). Life expectancy was similar (2.0 vs. 2.2 days). Recapture rates were high for both strains, possibly because of the uninhabited nature of the site.

Conclusions/Significance

After extensive contained studies and regulatory scrutiny, a field release of engineered mosquitoes was safely and successfully conducted in Malaysia. The engineered strain showed similar field longevity to an unmodified counterpart, though in this setting dispersal was reduced relative to the unmodified strain. These data are encouraging for the future testing and implementation of genetic control strategies and will help guide future field use of this and other engineered strains.     

GEF-H1 Mediates Tumor Necrosis Factor-��-induced Rho Activation and Myosin Phosphorylation: ROLE IN THE REGULATION OF TUBULAR PARACELLULAR PERMEABILITY*

Tumor necrosis factor-α (TNF-α), an inflammatory cytokine, has been shown to activate the small GTPase Rho, but the underlying signaling mechanisms remained undefined. This general problem is particularly important in the kidney, because TNF-α, a major mediator of kidney injury, is known to increase paracellular permeability in tubular epithelia. Here we aimed to determine the effect of TNF-α on the Rho pathway in tubular cells (LLC-PK₁ and Madin-Darby canine kidney), define the upstream signaling, and investigate the role of the Rho pathway in the TNF-α-induced alterations of paracellular permeability. We show that TNF-α induced a rapid and sustained RhoA activation that led to stress fiber formation and Rho kinase-dependent myosin light chain (MLC) phosphorylation. To identify new regulators connecting the TNF receptor to Rho signaling, we applied an affinity precipitation assay with a Rho mutant (RhoG17A), which captures activated GDP-GTP exchange factors (GEFs). Mass spectrometry analysis of the RhoG17A-precipitated proteins identified GEF-H1 as a TNF-α-activated Rho GEF. Consistent with a central role of GEF-H1, its down-regulation by small interfering RNA prevented the activation of the Rho pathway. Moreover GEF-H1 and Rho activation are downstream of ERK signaling as the MEK1/2 inhibitor PD98059 mitigated TNF-α-induced activation of these proteins. Importantly TNF-α enhanced the ERK pathway-dependent phosphorylation of Thr-678 of GEF-H1 that was key for activation. Finally the TNF-α-induced paracellular permeability increase was absent in LLC-PK₁ cells stably expressing a non-phosphorylatable, dominant negative MLC. In summary, we have identified the ERK/GEF-H1/Rho/Rho kinase/phospho-MLC pathway as the mechanism mediating TNF-α-induced elevation of tubular epithelial permeability, which in turn might contribute to kidney injury.Tumor necrosis factor-α (TNF-α)² is a pleiotropic proinflammatory cytokine that is synthesized as a membrane protein in response to inflammation, infection, and injury (1). Subsequently it is cleaved by the metalloprotease TNF-α convertase enzyme to release a 17-kDa soluble peptide (for a review, see Ref. 2). TNF-α has two receptors, the constitutively expressed, ubiquitous TNF receptor 1 and the inducible TNF receptor 2.An increasing body of evidence supports a key role for TNF-α in both acute renal injury and chronic kidney diseases (for reviews, see Refs. 3 and 4). Although TNF-α is almost undetectable in normal kidneys, elevated intrarenal, serum, or urine concentrations have been reported in various pathological states including ischemia-reperfusion, endotoxinemia, and early diabetic nephropathy (5–8). Moreover kidney injury in various pathological states was prevented or mitigated by inhibition of TNF-α production, by addition of neutralizing antibodies, or in TNF receptor knock-out mice (for a review, see Ref. 3). The central role of TNF-α in mediating kidney injury is therefore well established. Importantly TNF-α can be produced in the kidney not only by infiltrating macrophages and lymphocytes but by resident cells including the tubular epithelium. For example, in reperfusion injury TNF-α expression precedes macrophage infiltration and localizes mostly to the tubules (3, 7). Tubular TNF-α production is also enhanced by endotoxin and hypoxia (9–12). Although effects of locally released TNF-α on the tubular epithelium could contribute to its deleterious actions, the underlying mechanisms have been incompletely explored.Although a large number of studies have focused on the inflammatory and apoptotic signaling initiated by TNF-α in various cells, its cytoskeletal effects remain much less explored. In recent years Rho and its effector, Rho kinase (ROK), key regulators of both the actin cytoskeleton and myosin phosphorylation (13), have emerged as important mediators of TNF-α effects in endothelial cells (14–18). Similar effects in the tubular epithelium, however, have not been established. Even more importantly, the upstream signaling that connects the TNF receptor to activation of the Rho pathway remains completely unknown. Like other small GTPases, Rho cycles between an inactive (GDP-bound) and active (GTP-bound) form (13). The exchange of GDP to GTP during activation is stimulated by GDP-GTP exchange factors (GEFs). The diverse family of Rho GEFs contains >70 members in humans (19), making it challenging to identify the specific factors involved in mediating Rho activation through receptor-mediated stimuli. In the case of TNF-α, neither the particular Rho GEF involved nor the mechanism of its regulation has been identified in any of the cell systems studied.A rise in epithelial paracellular permeability through the intercellular junctions is a prominent event during inflammation (“leaky epithelium”) (for reviews, see Refs. 20 and 21). In addition, the junctions maintain the polarized phenotype of epithelial cells that is necessary for directional transport processes and constitute an important signaling platform that transmits environmental cues to the cells. Therefore, the consequences of junction disruption during inflammation might go beyond the compromised barrier functions. Interestingly TNF-α has been reported to affect the permeability of the tubular epithelium. Mullin et al. (22) have reported that in a tubular cell line TNF-α induced a temporary elevation in transepithelial resistance followed by a drop in transepithelial resistance and increased paracellular permeability. The transepithelial resistance decrease was blocked by genistein, a general tyrosine kinase inhibitor; however, the exact mechanism underlying the observed permeability changes remained incompletely explored.The actin cytoskeleton and especially phosphorylation of myosin light chain (MLC) was shown to be essential for the permeability increase caused by pathogens, cytokines, and growth factors in various epithelial and endothelial systems (for reviews, see Refs. 21, 23, and 24). Interestingly although myosin phosphorylation mediates the TNF-α-elicited permeability changes in intestinal cells (25, 26), phospho-MLC was reported not to be involved in the TNF-α-induced permeability rise in endothelial cells (17). The possible role of the Rho pathway and myosin phosphorylation in the TNF-α-induced permeability changes in the tubular epithelium therefore remains to be established.The aim of this study was to explore the signaling pathways through which TNF-α causes cytoskeleton remodeling and elevates paracellular permeability in kidney tubular cells. Our findings show that TNF-α induces rapid activation of RhoA that leads to Rho/Rho kinase-dependent actin remodeling and myosin phosphorylation. Using an affinity precipitation assay followed by mass spectrometry, we identified GEF-H1 as a TNF-α-activated GEF. We showed that GEF-H1 mediates the TNF-α-induced stimulation of Rho and its effectors. In addition, activation of the GEF-H1/Rho pathway by TNF-α was downstream of ERK signaling and required GEF-H1 phosphorylation on Thr-678. Finally using a dominant negative MLC mutant, we showed that myosin phosphorylation is essential for the TNF-α-induced elevation in paracellular permeability.