The peptidyl-prolyl isomerase and chaperone Par27 of Bordetella pertussis as the prototype for a new group of parvulins

Proteins that pass through the periplasm in an unfolded state are highly sensitive to proteolysis and aggregation and, therefore, often require protection by chaperone-like proteins. The periplasm of Gram-negative bacteria is well equipped with ATP-independent chaperones and folding catalysts, including peptidyl-prolyl isomerases (PPIases). The filamentous hemagglutinin of Bordetella pertussis, which is secreted by the two-partner secretion pathway, crosses the periplasm in an unfolded conformation. By affinity chromatography, we identified a new periplasmic PPIase of the parvulin family, Par27, which binds to an unfolded filamentous hemagglutinin fragment. Par27 differs from previously characterized bacterial and eukaryotic parvulins. Its central parvulin-like domain is flanked by atypical N- and C-terminal extensions that are found in a number of putative PPIases present mostly in β proteobacteria. Par27 displays both PPIase and chaperone activities in vitro. In vivo, Par27 might function as a general periplasmic chaperone in B. pertussis.     

Spatial variation of airborne pollen over south-east France: characterization and implications for monitoring networks management

The French airborne pollen monitoring network (RNSA) is currently regrouping 70 Hirst-type pollen traps covering the whole French territory. The aim of this paper is to introduce a simple statistical methodology that can be used to characterize pollen spatial variation. This pilot study is restricted to a limited portion of the RNSA network (18 monitoring stations), eight taxa of allergenic relevance, and a 3-year period (2003–2005). The first step of the approach consisted in quantifying the trap-to-trap pollen similarities on the basis of an original index, called mean Pollinic Distance (mPD), that relies on the comparison of pollen concentration time series. Regression analyses were next conducted with different spatial variables. Distance, latitude and altitude differences were identified as significant predictors of pollen variations, as measured by mPD. In order to further characterize pollen spatial properties, cluster analysis was performed with mPD as the distance estimate. Interestingly, the clusters of sites identified on the basis of the similarity of their pollen profiles, correspond to distinct geographic areas that might be interpreted as homogeneous air masses. The results have major implications for monitoring networks management since they provide an objective basis (1) for choosing the relevant scale to elaborate and supply pollen-related information, and (2) for optimizing networks configuration.

Male circumcision: hope for HIV infection decrease in southern Africa

Given the magnitude of the HIV pandemic, development of new prevention means is necessary. Male circumcision reduces HIV transmission from female to male by 57 % [95 % Confident Interval (CI): 42-68 %]. Its generalization in sub-Saharan Africa could avert, among men and women, from 1 to 4 millions new HIV infections over the next ten years. Acceptability of this new prevention mean is high in countries which could benefit the most from male circumcision, that means located in southern Africa, a region where in majority men are uncircumcised and where HIV prevalence is high. Male circumcision is a cost-effective prevention strategy. Actual prevention means (condoms, sexual abstinence and fidelity) are not used enough to curb the HIV epidemic. Research is ongoing on other prevention means (vaccine, pre- and post-exposition prophylaxis, microbicides, diaphragm) but their efficiency has not been demonstrated yet. Nevertheless, generalization of circumcision in southern Africa is responsible for contestations in part due to the fact that this prevention mean protects only partially from HIV infection. Moreover, for now, only a few countries integrated circumcision in their HIV prevention program in spite of WHO (World Health Organization) recommendations supporting male circumcision acknowledgement as an additional, important strategy for the prevention of heterosexually acquired HIV infection in men. Significant available funding should allow the situation to evolve quickly. At the same time, research goes on in order to know more about the effects and to facilitate the generalization of this prevention mean which is a great hope for southern Africa.     

Effects of Naltrexone and Acamprosate on Alcohol-Induced NGFI-A Expression in Mouse Brain

In search for the substrate of naltrexone and acamprosate action on alcohol craving, we investigated the effects of ethanol alone and combined with naltrexone or acamprosate on expression of nerve growth factor-inducible clone A (NGFI-A; zif268). In Experiments 1 and 3, alcohol (2 g/kg) alone or in combination with naltrexone (15 mg/kg) or acamprosate (300 mg/kg) was injected intraperitoneally into mice. In Experiment 2, treatment was nor-BNI (0.5 mg/kg) to investigate whether the effect of naltrexone involved blockade of κ-opioid receptors. Both ethanol and naltrexone alone induced NGFI-A in the central amygdala, but not in several other areas; these effects were additive. However, acamprosate alone or in combination with ethanol had no effect on NGFI-A mRNA, while nor-BNI induced NGFI-A mRNA in the basolateral amygdala. The central amygdala appears to be an important target of both alcohol and naltrexone. Acamprosate may not share the site of action with naltrexone despite being used for the same therapeutic purpose. Special issue article in honor of Dr.Ji-Sheng Han.     

Identification of inhibitors of the E. coli cyclopropane fatty acid synthase from the screening of a chemical library: In vitro and in vivo studies

Using an automated coupled colorimetric assay for the Escherichia coli cyclopropane fatty acid synthase (CFAS), we have screened an academic chemical library of 3040 compounds, to identify new inhibitors of this enzyme. We identified 8 compounds as potent inhibitors of this enzyme, with IC(50) ranging from 1 to 10 microM, in the presence of 750 microM S-adenosyl-l-methionine and 1 mg/mL phospholipids. We conducted kinetic analyses of the inhibition of the CFAS using dioctylamine and three inhibitors identified in this report: sinefungin, 1, a synthetic S-adenosyl-l-homocysteine analog, 2, and an indoloquinolizine derivative, 3. The inhibition patterns observed were interpreted assuming that the E. coli CFAS operated via an ordered Bi Bi mechanism with binding of S-adenosyl-l-methionine first. Dioctylamine was the most potent inhibitor with a competitive inhibition constant of 130 nM with respect to the phospholipids. Compound 2 bound to the two substrate-binding sites of the enzyme suggesting that it acted as a bisubstrate analog (apparent inhibition constant, K(I)=6 microM). Compound 2 was also found to completely inhibit cyclopropanation of the phospholipids in growing E. coli cells, at 150 microM. This molecule is thus the first inhibitor of a cyclopropane synthase that is active in vivo, contrary to sinefungin and other analogs that are only active on the isolated enzyme.     

Trio mediates netrin-1-induced Rac1 activation in axon outgrowth and guidance

The chemotropic guidance cue netrin-1 promotes neurite outgrowth through its receptor Deleted in Colorectal Cancer (DCC) via activation of Rac1. The guanine nucleotide exchange factor (GEF) linking netrin-1/DCC to Rac1 activation has not yet been identified. Here, we show that the RhoGEF Trio mediates Rac1 activation in netrin-1 signaling. We found that Trio interacts with the netrin-1 receptor DCC in mouse embryonic brains and that netrin-1-induced Rac1 activation in brain is impaired in the absence of Trio. Trio(-/-) cortical neurons fail to extend neurites in response to netrin-1, while they are able to respond to glutamate. Accordingly, netrin-1-induced commissural axon outgrowth is reduced in Trio(-/-) spinal cord explants, and the guidance of commissural axons toward the floor plate is affected by the absence of Trio. The anterior commissure is absent in Trio-null embryos, and netrin-1/DCC-dependent axonal projections that form the internal capsule and the corpus callosum are defective in the mutants. Taken together, these findings establish Trio as a GEF that mediates netrin-1 signaling in axon outgrowth and guidance through its ability to activate Rac1.     

Serum-derived hepatitis C virus infection of primary human hepatocytes is tetraspanin CD81 dependent

Hepatitis C virus-positive serum (HCVser, genotypes 1a to 3a) or HCV cell culture (JFH1/HCVcc) infection of primary normal human hepatocytes was assessed by measuring intracellular HCV RNA strands. Anti-CD81 antibodies and siRNA-CD81 silencing markedly inhibited (>90%) HCVser infection irrespective of HCV genotype, viral load, or liver donor, while hCD81-large intracellular loop (LEL) had no effect. However, JFH1/HCVcc infection of hepatocytes was modestly inhibited (40 to 60%) by both hCD81-LEL and anti-CD81 antibodies. In conclusion, CD81 is involved in HCVser infection of human hepatocytes, and comparative studies of HCVser versus JFH1/HCVcc infection of human hepatocytes and Huh-7.5 cells revealed that the cell-virion combination is determinant of the entry process.     

Elevated Serum Beta-D-Glucan with <Emphasis Type="Italic">Pseudomonas</Emphasis>, <Emphasis Type="Italic">Aspergillus</Emphasis>, and a Partially Acid-Fast Organism in Respiratory Cultures: A Case of Hickam’s Dictum Over Occam’s Razor

We describe a case of a man with ectopic Cushing’s syndrome, elevated serum beta-D-glucan, and respiratory cultures with Pseudomonas, Aspergillus, and a partially acid-fast organism. Our case highlights challenges in diagnosis and management of coinfection in an immunocompromised host.     

Identification by MALDI-TOF Mass Spectrometry of Mercury-resistant Bacteria Associated with the Rhizosphere of an Apple Orchard

In this work, mercury-resistant bacterial strains were isolated from the rhizosphere of an apple orchard, growing in a soil with high levels of mercury (Nuevo San Joaquin, Queretaro State, Mexico). Analysis of the soil in this region by the Cold Vapor Atomic Absortion Spectroscopy method showed that it contained 637 ± 51 mg mercury per kg. Mercury accumulation by fresh apples from this orchard amounted to 15.44 ± 4.33 mg/kg. The bacterial isolates were identified by application of proteomic technique of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). They were found to be strains of Bacillus muralis and Bacillus simplex. All strains showed the ability to catalyze the volatilization of Hg as measured via the nonradioactive X-ray method. In all strains merR and merA genes were detected by polymerase chain reaction. Nucleotide sequence analysis showed that merR from B. simplex was 435 bp in length and that its sequence was similar to merR sequences reported for other bacteria such as Cupriavidus, Ralstonia, Pseudomonas and Serratia. To our knowledge, this is the first report of mercury-resistant Bacillus strains isolated from the rhizosphere of an apple orchard and the first merR gene sequence from such Bacilli.