Inhibition of Acetyl-CoA Carboxylase by Phosphorylation or the Inhibitor ND-654 Suppresses Lipogenesis and Hepatocellular Carcinoma

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Encapsulated group B Streptococcus modulates dendritic cell functions via lipid rafts and clathrin‐mediated endocytosis

Group B Streptococcus (GBS) capsular type III is an important agent of life‐threatening invasive infections. It has been previously shown that encapsulated GBS is easily internalized by dendritic cells (DCs) and can persist inside these immune cells. The mechanisms underlying these processes are unknown. Here, colocalization studies and the use of endocytosis inhibitors and caveolin^?/? mice, demonstrated that GBS uses multiple endocytosis mechanisms to enter mouse DCs. The capsular polysaccharide (CPS) selectively drives GBS internalization via caveolae‐independent but lipid raft‐dependent pathways. Non‐encapsulated bacteria failed to engage lipid rafts. GBS internalization by DCs also occurs via clathrin‐mediated endocytosis in a process independent of bacterial CPS. Albeit caveolae are not required for GBS internalization, signalling events through caveolin‐1 are involved in production of the inflammatory chemokine CCL2 by DCs infected with encapsulated GBS only. This study addresses for the first time endocytosis pathways implicated in DC internalization of encapsulated GBS and suggests a complex interplay between GBS and DCs, which was selectively modulated by the presence of CPS.     

Mineralocorticoids participate in the reduced vascular reactivity of pregnant rats

The renin-angiotensin-aldosterone (RAA) system is markedly activated in pregnancy. We evaluated if mineralocorticoid receptors (MR), a major component of the RAA system, are involved in the reduced vascular reactivity associated with pregnancy. Canrenoate (MR antagonist; 20 mg·kg(-1)·day(-1)) was administered to nonpregnant (NP) rats for 7 days and to pregnant rats from day 15 to 22 of gestation. These were killed on day 17, 19, or 22 of gestation and, for NP rats, after 7 days treatment. Constrictor responses to phenylephrine (PhE) and KCl were measured in endothelium-denuded thoracic aortic rings under the influence of modulators of potassium (activators) and calcium (blocker) channels. Responses to the constrictors were blunted from days 17 to 22 of gestation. Although canrenoate increased responses to PhE and KCl, it did not reverse their blunted responses in gestation. NS-1619 and cromakalim (respectively, high-conductance calcium-activated potassium channels and ATP-sensitive potassium channel activators) diminished responses to both PhE and KCl. Inhibition by NS-1619 on responses to both agonists was decreased under canrenoate treatment in NP, but the reduced influence of NS-1619 during gestation was reversed by the mineralocorticoid antagonist. Cromakalim reduced the response to PhE significantly in the pregnant groups; this effect was enhanced by canrenoate. Finally, nifedipine (calcium channel blocker) markedly reduced KCl responses but to a lesser extent at the end of pregnancy, an inhibiting effect that was increased with canrenoate treatment. These data demonstrate that treating rats with a MR antagonist increased vascular reactivity but that it differentially affected potassium and calcium channel activity in aortas of NP and pregnant animals. This suggests that aldosterone is one of the components involved in vascular adaptations to pregnancy.     

Modulation of the phagosome proteome by interferon-gamma

Macrophages are immune cells that function in the clearance of infectious particles. This process involves the engulfment of microbes into phagosomes where these particles are lysed and degraded. In the current study, we used a large scale quantitative proteomics approach to analyze the changes in protein abundance induced on phagosomes by interferon-gamma (IFN-gamma), an inflammatory cytokine that activates macrophages. Our analysis identified 167 IFN-gamma-modulated proteins on phagosomes of which more than 90% were up-regulated. The list of phagosomal proteins regulated by IFN-gamma includes proteins expected to alter phagosome maturation, enhance microbe degradation, trigger the macrophage immune response, and promote antigen loading on major histocompatibility complex (MHC) class I molecules. A dynamic analysis of IFN-gamma-sensitive proteins by Western blot indicated that newly formed phagosomes display a delayed proteolytic activity coupled to an increased recruitment of the MHC class I peptide-loading complex. These phagosomal conditions may favor antigen presentation by MHC class I molecules on IFN-gamma-activated macrophages.     

Genome-wide SNP genotyping highlights the role of natural selection in Plasmodium falciparum population divergence

Background

The malaria parasite Plasmodium falciparum exhibits abundant genetic diversity, and this diversity is key to its success as a pathogen. Previous efforts to study genetic diversity in P. falciparum have begun to elucidate the demographic history of the species, as well as patterns of population structure and patterns of linkage disequilibrium within its genome. Such studies will be greatly enhanced by new genomic tools and recent large-scale efforts to map genomic variation. To that end, we have developed a high throughput single nucleotide polymorphism (SNP) genotyping platform for P. falciparum.

Results

Using an Affymetrix 3,000 SNP assay array, we found roughly half the assays (1,638) yielded high quality, 100% accurate genotyping calls for both major and minor SNP alleles. Genotype data from 76 global isolates confirm significant genetic differentiation among continental populations and varying levels of SNP diversity and linkage disequilibrium according to geographic location and local epidemiological factors. We further discovered that nonsynonymous and silent (synonymous or noncoding) SNPs differ with respect to within-population diversity, inter-population differentiation, and the degree to which allele frequencies are correlated between populations.

Conclusions

The distinct population profile of nonsynonymous variants indicates that natural selection has a significant influence on genomic diversity in P. falciparum, and that many of these changes may reflect functional variants deserving of follow-up study. Our analysis demonstrates the potential for new high-throughput genotyping technologies to enhance studies of population structure, natural selection, and ultimately enable genome-wide association studies in P. falciparum to find genes underlying key phenotypic traits.     

Adaptations of placental and cord blood ABCA1 DNA methylation profile to maternal metabolic status

In utero environmental perturbations have been associated with epigenetic changes in the offspring and a lifelong susceptibility to cardiovascular diseases (CVD). DNA methylation at the ATP-binding cassette transporter A1 (ABCA1) gene was previously associated with CVD, but whether these epigenetic marks respond to changes in the maternal environment is unknown. This study was undertaken to assess the associations between the maternal metabolic profile and ABCA1 DNA methylation levels in placenta and cord blood. Placenta and cord blood samples were obtained at delivery from 100 women including 26 with impaired glucose tolerance (IGT) diagnosed following a 75 g-oral glucose tolerance test (OGTT) between week 24 and 28 of gestation. ABCA1 DNA methylation and mRNA levels were measured using bisulfite pyrosequencing and quantitative real-time PCR, respectively. We report that ABCA1 DNA methylation levels on the maternal side of the placenta are correlated with maternal high density lipoprotein cholesterol (HDL-C) levels (r < –0.21; P < 0.04) and glucose levels 2 h post-OGTT (r = 0.25; P = 0.02). On the fetal side of the placenta, ABCA1 DNA methylation levels are associated with cord blood triglyceride levels (r = –0.28; P = 0.01). ABCA1 DNA methylation variability on both sides of the placenta are also associated with ABCA1 mRNA levels (r < –0.35; P = 0.05). As opposed to placenta, cord blood DNA methylation levels are negatively correlated with maternal glucose 2 h post-OGTT (r = –0.26; P = 0.02). In conclusion, the epivariations observed in placenta and cord blood likely contribute to an optimal materno–fetal cholesterol transfer. These in utero epigenetics adaptations may also potentially trigger the long-term susceptibility of the newborn to dyslipidemia and CVD.     

Betaine Improves Freezing Tolerance in Wheat

The accumulation of the osmolyte betaine was found to be correlatedwith the development of freezing tolerance (FT) of two wheatcultivars where it increases by about three fold during thecold acclimation period. Exogenous betaine application resultedin a large increase in total osmolality mostly due to betaineaccumulation. Plants that accumulated betaine are more tolerantto freezing stress since a four day exposure to 250 mM betaineresulted in a LT₅₀ of –8°C (in spring wheat Glenlea)and –9°C (in winter wheat Fredrick) compared to –3°C(Glenlea) and –4°C (Fredrick) for control non-exposedplants. Betaine treatment (250 mM) during cold acclimation increasedFT in an additive manner since the LT₅₀ reached –14°C(Glenlea) and –22°C (Fredrick) compared to –8°C(Glenlea) and –16°C (Fredrick) for plants that arecold acclimated in the absence of betaine. These results showthat betaine treatment can improve FT by more than 5°C inboth non-acclimated and cold-acclimated plants. The betainetreatment resulted in the induction of a subset of low temperatureresponsive genes, such as the wcor410, and wcor413, that arealso induced by salinity or drought stresses. In addition tothese genetic responses, betaine treatment was also able toimprove the tolerance to photoin-hibition of PSII and the steady-stateyield of electron transport over PSII in a manner that mimickedcold-acclimated plants. These data also suggest that betaineimproves FT by eliciting some of the genetic and physiologicalresponses associated with cold acclimation. (Received April 23, 1998; Accepted September 4, 1998)     

Synthesis of Receptor Sites for Vitamin B12 in Euglena gracilis

In Euglena gracilis, vitamin B₁₂ uptake follows a biphasic patternconsisting of an initial rapid phase followed by a slower secondaryphase. Chase experiments showed that vitamin B₁₂ was tightlybound to its receptor-sites during either rapid or slow phaseof uptake. The slow phase was markedly inhibited when Euglenacells were preincubated with cycloheximide for 30 min at a concentrationof 100µg/ml. When the preincubation time was longer than30 min, a gradual inhibition of the rapid phase occurred andreached 84% after 4 h. This inhibitory effect of cycloheximideis reversible. On the other hand, tunicamycin at 1 µ/mlirreversibly inhibited the B₁₂ uptake suggesting that the receptor-sitefor B₁₂ is glycoprotein in nature. These results suggest thatthe rapid phase is also dependent on protein synthesis and representsB₁₂ binding on preexisting free receptors whereas the secondaryslow phase represents B_l2 binding on newly synthesized receptors.Both phases of uptake seem to be controled by the same receptor.The half-life of the free receptor is estimated to be 66 minwhereas the B₁₂ receptor complex is very stable. (Received October 3, 1988; Accepted February 15, 1989)     

A molecular marker to select for freezing tolerance in Gramineae

Summary We isolated, and expressed in Escherichia coli, a gene (Wcs120) that is strongly induced during cold acclimation of wheat. The gene product was purified and used to produce antibodies. Immunoblotting experiments with the anti-WCS120 antibody identified several cold-induced proteins named FTMs for Freezing Tolerance Markers since they are associated with the development of freezing tolerance. This protein family was found to be coordinately regulated specifically by low temperature, highly hydrophilic, stable to boiling, and to have a pI above 6.5. The accumulation kinetics during the acclimation period indicated a positive correlation with the capacity of each genotype to develop freezing tolerance. Accumulation of the proteins was higher in the freezing-tolerant genotype than in the less tolerant one. In addition, their accumulation was more pronounced in the crown and leaf tissues compared with roots, confirming a relationship to the capacity of the different tissues to develop freezing tolerance. Analysis of different species (eight monocots and four dicots) indicated that this protein family is specific for freezing-tolerant cereals. The antibody did not cross-react with any of the non-cereal species examined. The anti-FTMs antibody represents a potential tool for breeders to select for freezing tolerance traits in the Gramineae.