Behaviour in captivity predicts some aspects of natural behaviour,but not others,in a wild cricket population

Examining the relevance of ‘animal personality’ involves linking consistent among- and within-individual behavioural variation to fitness in the wild. Studies aiming to do this typically assay personality in captivity and rely on the assumption that measures of traits in the laboratory reflect their expression in nature. We examined this rarely tested assumption by comparing laboratory and field measurements of the behaviour of wild field crickets (Gryllus campestris) by continuously monitoring individual behaviour in nature, and repeatedly capturing the same individuals and measuring their behaviour in captivity. We focused on three traits that are frequently examined in personality studies: shyness, activity and exploration. All of them showed repeatability in the laboratory. Laboratory activity and exploration predicted the expression of their equivalent behaviours in the wild, but shyness did not. Traits in the wild were predictably influenced by environmental factors such as temperature and sunlight, but only activity showed appreciable within-individual repeatability. This suggests that some behaviours typically studied as personality traits can be accurately assayed in captivity, but the expression of others may be highly context-specific. Our results highlight the importance of validating the relevance of laboratory behavioural assays to analogous traits measured in the wild.     

A Novel MHC-I Surface Targeted for Binding by the MCMV m06 Immunoevasin Revealed by Solution NMR

As part of its strategy to evade detection by the host immune system, murine cytomegalovirus (MCMV) encodes three proteins that modulate cell surface expression of major histocompatibility complex class I (MHC-I) molecules: the MHC-I homolog m152/gp40 as well as the m02-m16 family members m04/gp34 and m06/gp48. Previous studies of the m04 protein revealed a divergent Ig-like fold that is unique to immunoevasins of the m02-m16 family. Here, we engineer and characterize recombinant m06 and investigate its interactions with full-length and truncated forms of the MHC-I molecule H2-L^d by several techniques. Furthermore, we employ solution NMR to map the interaction footprint of the m06 protein on MHC-I, taking advantage of a truncated H2-L^d, “mini-H2-L^d,” consisting of only the α1α2 platform domain. Mini-H2-L^d refolded in vitro with a high affinity peptide yields a molecule that shows outstanding NMR spectral features, permitting complete backbone assignments. These NMR-based studies reveal that m06 binds tightly to a discrete site located under the peptide-binding platform that partially overlaps with the β₂-microglobulin interface on the MHC-I heavy chain, consistent with in vitro binding experiments showing significantly reduced complex formation between m06 and β₂-microglobulin-associated MHC-I. Moreover, we carry out NMR relaxation experiments to characterize the picosecond-nanosecond dynamics of the free mini-H2-L^d MHC-I molecule, revealing that the site of interaction is highly ordered. This study provides insight into the mechanism of the interaction of m06 with MHC-I, suggesting a structural manipulation of the target MHC-I molecule at an early stage of the peptide-loading pathway.     

Discovery of a novel and conserved Plasmodium falciparum exported protein that is important for adhesion of PfEMP1 at the surface of infected erythrocytes

Plasmodium falciparum virulence is linked to its ability to sequester in post‐capillary venules in the human host. Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is the main variant surface antigen implicated in this process. Complete loss of parasite adhesion is linked to a large subtelomeric deletion on chromosome 9 in a number of laboratory strains such as D10 and T9‐96. Similar to the cytoadherent reference line FCR3, D10 strain expresses PfEMP1 on the surface of parasitized erythrocytes, however without any detectable cytoadhesion. To investigate which of the deleted subtelomeric genes may be implicated in parasite adhesion, we selected 12 genes for D10 complementation studies that are predicted to code for proteins exported to the red blood cell. We identified a novel single copy gene (PF3D7_0936500) restricted to P. falciparum that restores adhesion to CD36, termed here virulence‐associated protein 1 (Pfvap1). Protein knockdown and gene knockout experiments confirmed a role of PfVAP1 in the adhesion process in FCR3 parasites. PfVAP1 is co‐exported with PfEMP1 into the host cell via vesicle‐like structures called Maurer's clefts. This study identifies a novel highly conserved parasite molecule that contributes to parasite virulence possibly by assisting PfEMP1 to establish functional adhesion at the host cell surface.     

Cd, Fe, and light sensitivity: interrelationships in Cd-treated populus

Cadmium is a toxic heavy metal causing iron deficiency in the shoot and light sensitivity of photosynthetic tissues that leads to decreased photosynthetic performance and biomass production. Light intensity had strong impact on both photosynthetic activity and metal accumulation of cadmium-treated plants. At elevated irradiation, cadmium accumulation increased due to the higher dry mass of plants, but its allocation hardly changed. A considerable amount of iron accumulated in the roots, and iron concentration was higher in leaves developed at moderate rather than low irradiation. At the same time, the higher the irradiation the lower the maximal photochemical quantum efficiency. The decreased photochemical efficiency, however, started to recover after a week of Cd treatment at moderate light without substantial change in metal concentrations but following the accumulation of green fluorescent compounds. Both cadmium treatment and higher light caused the accumulation of flavonoids in leaf mesophyll vacuoles/chloroplasts, but accumulation of flavonols, fluorescing at 510?nm, was characteristic to cadmium stress. Therefore, flavonoids, which may act by scavenging reactive radicals, chelating Cd, and shielding against excess irradiation, play an important part in Cd stress tolerance of Populus, and may have special impact on its phytoremediation capacity.     

Context-dependent encoding of fear and extinction memories in a large-scale network model of the basal amygdala

The basal nucleus of the amygdala (BA) is involved in the formation of context-dependent conditioned fear and extinction memories. To understand the underlying neural mechanisms we developed a large-scale neuron network model of the BA, composed of excitatory and inhibitory leaky-integrate-and-fire neurons. Excitatory BA neurons received conditioned stimulus (CS)-related input from the adjacent lateral nucleus (LA) and contextual input from the hippocampus or medial prefrontal cortex (mPFC). We implemented a plasticity mechanism according to which CS and contextual synapses were potentiated if CS and contextual inputs temporally coincided on the afferents of the excitatory neurons. Our simulations revealed a differential recruitment of two distinct subpopulations of BA neurons during conditioning and extinction, mimicking the activation of experimentally observed cell populations. We propose that these two subgroups encode contextual specificity of fear and extinction memories, respectively. Mutual competition between them, mediated by feedback inhibition and driven by contextual inputs, regulates the activity in the central amygdala (CEA) thereby controlling amygdala output and fear behavior. The model makes multiple testable predictions that may advance our understanding of fear and extinction memories.     

Functional selectivity of adenosine receptor ligands

Adenosine receptors are plasma membrane proteins that transduce an extracellular signal into the interior of the cell. Basically every mammalian cell expresses at least one of the four adenosine receptor subtypes. Recent insight in signal transduction cascades teaches us that the current classification of receptor ligands into agonists, antagonists, and inverse agonists relies very much on the experimental setup that was used. Upon activation of the receptors by the ubiquitous endogenous ligand adenosine they engage classical G protein-mediated pathways, resulting in production of second messengers and activation of kinases. Besides this well-described G protein-mediated signaling pathway, adenosine receptors activate scaffold proteins such as β-arrestins. Using innovative and sensitive experimental tools, it has been possible to detect ligands that preferentially stimulate the β-arrestin pathway over the G protein-mediated signal transduction route, or vice versa. This phenomenon is referred to as functional selectivity or biased signaling and implies that an antagonist for one pathway may be a full agonist for the other signaling route. Functional selectivity makes it necessary to redefine the functional properties of currently used adenosine receptor ligands and opens possibilities for new and more selective ligands. This review focuses on the current knowledge of functionally selective adenosine receptor ligands and on G protein-independent signaling of adenosine receptors through scaffold proteins.     

Septin9 is involved in septin filament formation and cellular stability

Septin9 (Sept9) is a member of the filament-forming septin family of structural proteins and is associated with a variety of cancers and with hereditary neuralgic amyotrophy. We have generated mice with constitutive and conditional Sept9 knockout alleles. Homozygous deletion of Sept9 results in embryonic lethality around day 10 of gestation whereas mice homozygous for the conditional allele develop normally. Here we report the consequences of homozygous loss of Sept9 in immortalized murine embryonic fibroblasts. Proliferation rate was not changed but cells without Sept9 had an altered morphology compared to normal cells, particularly under low serum stress. Abnormal, fragmented, and multiple nuclei were more frequent in cells without Sept9. Cell migration, as measured by gap-filling and filter-invasion assays, was impaired, but individual cells did not move less than wild-type cells. Sept9 knockout cells showed a reduced resistance to hypo-osmotic stress. Stress fiber and vinculin staining at focal adhesion points was less prominent. Long septin filaments stained for Sept7 disappeared. Instead, staining was found in short, often curved filaments and rings. Furthermore, Sept7 was no longer localized to the mitotic spindle. Together, these data reveal the importance of Sept9 for septin filament formation and general cell stability.     

Isolation, functional, and partial biochemical characterization of galatrox, an acidic lectin from Bothrops atrox snake venom

Snake venom lectins have been studied in regard to their chemical structure and biological functions. However, little is known about lectins isolated from Bothrops atrox snake venom. We report here the isolation and partial functional and biochemical characterization of an acidic glycan-binding protein called galatrox from this venom. This lectin was purified by affinity chromatography using a lactosyl-sepharose column, and its homogeneity and molecular mass were evaluated by high-performance liquid chromatography, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry. The purified galatrox was homogeneous and characterized as an acidic protein (pI 5.2) with a monomeric and dimeric molecular mass of 16.2 and 32.5 kDa, respectively. Alignment of N-terminal and internal amino acid sequences of galatrox indicated that this protein exhibits high homology to other C-type snake venom lectins. Galatrox showed optimal hemagglutinating activity at a concentration of 100 μg/ml and this effect was drastically inhibited by lactose, ethylenediaminetetraacetic acid, and heating, which confirmed galatrox's lectin activity. While galatrox failed to induce the same level of paw edema or mast cell degranulation as B. atrox crude venom, galatrox did alter cellular viability, which suggested that galatrox might contribute to venom toxicity by directly inducing cell death.