A glycine betaine importer limits Salmonella stress resistance and tissue colonization by reducing trehalose production

Mechanisms by which Salmonella establish chronic infections are not well understood. Microbes respond to stress by importing or producing compatible solutes, small molecules that stabilize proteins and lipids. The Salmonella locus opuABCD (also called OpuC) encodes a predicted importer of the compatible solute glycine betaine. Under stress conditions, if glycine betaine cannot be imported, Salmonella enterica produce the disaccharide trehalose, a highly effective compatible solute. We demonstrate that strains lacking opuABCD accumulate more trehalose under stress conditions than wild-type strains. ΔopuABCD mutant strains are more resistant to high-salt, low-pH and -hydrogen peroxide, conditions that mimic aspects of innate immunity, in a trehalose-dependent manner. In addition, ΔopuABCD mutant strains require the trehalose production genes to out-compete wild-type strains in mice and macrophages. These data suggest that in the absence of opuABCD, trehalose accumulation increases bacterial resistance to stress in broth and mice. Thus, opuABCD reduces bacterial colonization via a mechanism that limits trehalose production. Mechanisms by which microbes limit disease may reveal novel pathways as therapeutic targets.     

Selection on laying date is connected to breeding density in the pied flycatcher

Timing of reproduction and clutch size are important determinants of breeding success, especially in seasonal environments. Several recent bird population studies have shown changes in breeding time and in natural selection on it. These changes have often been linked with climate change, but few studies have investigated how the traits or natural selection are actually connected with climatic factors. Furthermore, the effect of population density on selection has been rarely considered, despite the potential importance of density in demographic processes. We studied variation in natural selection on laying date and on clutch size in relation to measures of spring phenology and population density in a long-term study of pied flycatchers in SW Finland. The phenological stage of the environment at mean egg-laying did not affect the direction of selection on either laying date or on clutch size. There was, however, stronger selection for earlier laying date when the breeding density of the population was high, suggesting that early breeding is not necessarily beneficial as such, but that its importance is emphasized when high population density increases competition. In addition, early breeding was favoured when the pre-breeding period was cool, which may indicate an increased advantage for the fittest individuals in harsher conditions. In the middle of the twentieth century, there was selection for large clutch size, which subsequently ceased, along with an overall decrease in recruit production. Our results indicate that attention should be paid to demographic factors such as breeding density when studying natural selection and temporal changes in it.     

The proteomics of feather development in pied flycatchers (Ficedula hypoleuca) with different plumage coloration

The genetic theory of morphological evolution postulates that form evolves largely by changing the expression proteins that are functionally conserved. It follows that understanding the function of proteins during different phases of development as well as the mechanisms by which the functions are modified is a prerequisite for understanding evolutionary change. Male pied flycatchers exhibit marked phenotypic variation in their breeding plumage. This variation has repeatedly been shown to have adaptive significance, but the molecular basis of this variation is not known. Here, we characterize the proteome of developing pied flycatcher feathers from differently pigmented males and also introduce a new method for examining the effect sizes of expression differences in protein interaction networks. Approximately 300 proteins were identified in the developing feathers of males. Gene products associated with cellular transport, cell metabolism and protein synthesis formed a large part of the developing feather proteome. Sixty‐five proteins associated with the development of the epidermis and/or pigmentation were detected in the data. The examination of expression level differences of protein–protein interaction networks revealed an immunological signalling–related network to exhibit significantly higher expression in black compared to brown males. Additionally, indications of differences in energy balance and oxidative stress related characteristics were detected. Together, these results provide new insight into the molecular mechanisms and evolutionary significance of plumage colour variation.     

Structure of bradavidin-C-terminal residues act as intrinsic ligands

Bradavidin is a homotetrameric biotin-binding protein from Bradyrhizobium japonicum, a nitrogen fixing and root nodule-forming symbiotic bacterium of the soybean. Wild-type (wt) bradavidin has 138 amino acid residues, whereas the C-terminally truncated core-bradavidin has only 118 residues. We have solved the X-ray structure of wt bradavidin and found that the C-terminal amino acids of each subunit were uniquely bound to the biotin-binding pocket of an adjacent subunit. The biotin-binding pocket occupying peptide (SEKLSNTK) was named "Brad-tag" and it serves as an intrinsic stabilizing ligand in wt bradavidin. The binding of Brad-tag to core-bradavidin was analysed by isothermal titration calorimetry and a binding affinity of ～25 μM was measured. In order to study the potential of Brad-tag, a green fluorescent protein tagged with Brad-tag was prepared and successfully concentrated from a bacterial cell lysate using core-bradavidin-functionalized Sepharose resin.     

An ocular cysticercosis in Bali, Indonesia caused by Taenia solium Asian genotype

An ocular cysticercosis case of a nine-year-old Balinese girl in Indonesia is reported. She presented with redness and pain in the left eye and showed a cysticercus in the anterior chamber in December 2010. Morphological feature of the cysticercus removed from the anterior chamber indicated that it was an immature cysticercus of Taenia species with no hooklets. However, mitochondrial DNA analysis using a piece of histopathological specimen revealed it a cysticercus of Taenia solium Asian genotype. Serology by immunoblot and ELISA highly specific to cysticercosis was negative.     

A neurotoxic phospholipase a(2) impairs yeast amphiphysin activity and reduces endocytosis

Background

Presynaptically neurotoxic phospholipases A₂ inhibit synaptic vesicle recycling through endocytosis.

Principal Findings

Here we provide insight into the action of a presynaptically neurotoxic phospholipase A₂ ammodytoxin A (AtxA) on clathrin-dependent endocytosis in budding yeast. AtxA caused changes in the dynamics of vesicle formation and scission from the plasma membrane in a phospholipase activity dependent manner. Our data, based on synthetic dosage lethality screen and the analysis of the dynamics of sites of endocytosis, indicate that AtxA impairs the activity of amphiphysin.

Conclusions

We identified amphiphysin and endocytosis as the target of AtxA intracellular activity. We propose that AtxA reduces endocytosis following a mechanism of action which includes both a specific protein–protein interaction and enzymatic activity, and which is applicable to yeast and mammalian cells. Knowing how neurotoxic phospholipases A₂ work can open new ways to regulate endocytosis.     

Genetic Modulation of Lipid Profiles following Lifestyle Modification or Metformin Treatment: The Diabetes Prevention Program

Weight-loss interventions generally improve lipid profiles and reduce cardiovascular disease risk, but effects are variable and may depend on genetic factors. We performed a genetic association analysis of data from 2,993 participants in the Diabetes Prevention Program to test the hypotheses that a genetic risk score (GRS) based on deleterious alleles at 32 lipid-associated single-nucleotide polymorphisms modifies the effects of lifestyle and/or metformin interventions on lipid levels and nuclear magnetic resonance (NMR) lipoprotein subfraction size and number. Twenty-three loci previously associated with fasting LDL-C, HDL-C, or triglycerides replicated (P = 0.04–1×10⁻¹⁷). Except for total HDL particles (r = −0.03, P = 0.26), all components of the lipid profile correlated with the GRS (partial |r| = 0.07–0.17, P = 5×10⁻⁵–1×10⁻¹⁹). The GRS was associated with higher baseline-adjusted 1-year LDL cholesterol levels (β = +0.87, SEE±0.22 mg/dl/allele, P = 8×10⁻⁵, P _interaction = 0.02) in the lifestyle intervention group, but not in the placebo (β = +0.20, SEE±0.22 mg/dl/allele, P = 0.35) or metformin (β = −0.03, SEE±0.22 mg/dl/allele, P = 0.90; P _interaction = 0.64) groups. Similarly, a higher GRS predicted a greater number of baseline-adjusted small LDL particles at 1 year in the lifestyle intervention arm (β = +0.30, SEE±0.012 ln nmol/L/allele, P = 0.01, P _interaction = 0.01) but not in the placebo (β = −0.002, SEE±0.008 ln nmol/L/allele, P = 0.74) or metformin (β = +0.013, SEE±0.008 nmol/L/allele, P = 0.12; P _interaction = 0.24) groups. Our findings suggest that a high genetic burden confers an adverse lipid profile and predicts attenuated response in LDL-C levels and small LDL particle number to dietary and physical activity interventions aimed at weight loss.     

Endogenous cannabinoid anandamide inhibits nicotinic acetylcholine receptor function in mouse thalamic synaptosomes

The effects of the endogenous cannabinoid anandamide [arachidonylethanolamide (AEA)] on the function of nicotinic acetylcholine receptor (nAChR) were investigated using the ⁸⁶Rb⁺ efflux assay in thalamic synaptosomes. AEA reversibly inhibited ⁸⁶Rb⁺ efflux induced by 300 μM ACh with an IC₅₀ value of 0.9 ± 2 μM. Pre-treatment with the cannabinoid (CB₁) receptor antagonist SR141716A (1 μM), the CB₂ receptor antagonist SR144528 (1 μM), or pertussis toxin (0.2 mg/mL) did not alter the inhibitory effects of AEA, suggesting that known CB receptors are not involved in AEA inhibition of nAChRs. AEA inhibition of ⁸⁶Rb⁺ efflux was not reversed by increasing acetylcholine (ACh) concentrations. In radioligand binding studies, the specific binding of [³H]-nicotine was not altered in the presence of AEA, indicating that AEA inhibits the function of nAChR in a non-competitive manner. Neither the amidohydrolase inhibitor phenylmethylsulfonyl fluoride (0.2 mM) nor the cyclooxygenase inhibitor, indomethacin, (5 μM) affected AEA inhibition of nAChRs, suggesting that the effect of AEA is not mediated by its metabolic products. Importantly, the extent of AEA inhibition of ⁸⁶Rb⁺ efflux was significantly attenuated by the absence of 1% fatty acid free bovine serum albumin pre-treatment, supporting previous findings that fatty acid-like compounds modulate the activity of nAChRs. Collectively, the results indicate that AEA inhibits the function of nAChRs in thalamic synaptosomes via a CB-independent mechanism and that the background activity of these receptors is affected by fatty acids and AEA.