β-Barrel Mobility Underlies Closure of the Voltage-Dependent Anion Channel

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Highlights? The rigid N-terminal helix of VDAC stabilizes the cylindrical β-barrel ? Removal of the helix leads to elliptical, semicollapsed pore shapes ? Semicollapse can quantitatively explain conductance and selectivity of closed VDAC ? The N terminus acts as a switch controlling VDAC entry into the closed state     

Habitat stability affects dispersal and the ability to track climate change

Habitat persistence should influence dispersal ability, selecting for stronger dispersal in habitats of lower temporal stability. As standing (lentic) freshwater habitats are on average less persistent over time than running (lotic) habitats, lentic species should show higher dispersal abilities than lotic species. Assuming that climate is an important determinant of species distributions, we hypothesize that lentic species should have distributions that are closer to equilibrium with current climate, and should more rapidly track climatic changes. We tested these hypotheses using datasets from 1988 and 2006 containing all European dragon- and damselfly species. Bioclimatic envelope models showed that lentic species were closer to climatic equilibrium than lotic species. Furthermore, the models over-predicted lotic species ranges more strongly than lentic species ranges, indicating that lentic species track climatic changes more rapidly than lotic species. These results are consistent with the proposed hypothesis that habitat persistence affects the evolution of dispersal.     

miR-17-5p Regulates Endocytic Trafficking through Targeting TBC1D2/Armus

miRNA cluster miR-17-92 is known as oncomir-1 due to its potent oncogenic function. miR-17-92 is a polycistronic cluster that encodes 6 miRNAs, and can both facilitate and inhibit cell proliferation. Known targets of miRNAs encoded by this cluster are largely regulators of cell cycle progression and apoptosis. Here, we show that miRNAs encoded by this cluster and sharing the seed sequence of miR-17 exert their influence on one of the most essential cellular processes – endocytic trafficking. By mRNA expression analysis we identified that regulation of endocytic trafficking by miR-17 can potentially be achieved by targeting of a number of trafficking regulators. We have thoroughly validated TBC1D2/Armus, a GAP of Rab7 GTPase, as a novel target of miR-17. Our study reveals regulation of endocytic trafficking as a novel function of miR-17, which might act cooperatively with other functions of miR-17 and related miRNAs in health and disease.     

No Concordant Phylogeographies of the Rose Gall Wasp Diplolepis rosae (Hymenoptera,Cynipidae) and Two Associated Parasitoids across Europe

According to the Host-tracking Hypothesis, species of higher trophic levels with a close relationship to their hosts, such as parasites or parasitoids, are expected to show spatio-temporal phylogeographic patterns similar to those of their host. Alternatively, with ecological sorting, a subset of the local species pools might shift to a related host species, thereby disengaging common phylogeographic patterns. Here, we compare the phylogeographic structures of the cynipid rose gall wasp Diplolepis rosae across Europe and of two of its most common parasitoids, the wasps Orthopelma mediator and Glyphomerus stigma, by analysing the sequences of two gene fragments (COI and ITS 2). The phylogeographic structures of the three species associated with roses were incongruent. D. rosae had the lowest genetic diversity with one major clade, O. mediator showed the classical phylogeographic structure for Europe with one eastern and one western clade, and G. stigma had the highest diversity but no geographical structuring. This discordance of geographical patterns may be explained by 1) the dispersal propensity of adult parasitoids or 2) the parasitoids having the ability to switch to another host, while the primary host becomes rare or is even not available. Furthermore there was no indication that phylogenetic patterns were affected by Wolbachia infections. Our results document that communities of closely interacting species may be the result of idiosyncratic biogeographic histories.     

In vivo determination of mouse olfactory mucus cation concentrations in normal and inflammatory States

Objective

Olfaction is impaired in chronic rhinosinusitis (CRS). The study has two aims: (1) to determine whether changes in cation concentration occur in the olfactory mucus of mice with CRS, which may affect chemo-electrical transduction, (2) and to examine whether these alterations are physiologically significant in humans.

Study Design

Animal study in mice and translational study in humans.

Methods

Inflammation was induced by sensitization and chronic exposure of 16 C57BL/6 mice to Aspergillus fumigatus. The control group included 16 untreated mice. Ion-selective microelectrodes were used to measure free cation concentrations in the olfactory mucus of 8 mice from each treatment group, while the remaining mice were sacrificed for histology. To validate the findings in the animal model, olfactory threshold was measured in 11 healthy human participants using Sniffin’ Sticks before and after nasal irrigation with solutions that were composed of either of the cation concentrations.

Results

In 8 mice, olfactory mucus of chronically inflamed mice had lower [Na⁺] (84.8±4.45 mM versus 93.73±3.06 mM, p = 0.02), and higher [K⁺] (7.2±0.65 mM versus 5.7±0.20 mM, p = 0.04) than controls. No difference existed in [Ca²⁺] (0.50±0.12 mM versus 0.54±0.06 mM, p = 0.39). In humans, rinsing with solutions replicating ion concentrations of the mouse mucosa with chronic inflammation caused a significant elevation in the median olfactory threshold (9.0 to 4.8, p = 0.003) but not with the control solution (8.3 to 7.8, p = 0.75).

Conclusion

Chronic inflammation elevates potassium and lowers sodium ion concentration in mice olfactory mucus. Nasal irrigation with a corresponding solution induced olfactory threshold shift in humans.     

Triangular Relationship between Sleep Spindle Activity,General Cognitive Ability and the Efficiency of Declarative Learning

EEG sleep spindle activity (SpA) during non-rapid eye movement (NREM) sleep has been reported to be associated with measures of intelligence and overnight performance improvements. The reticular nucleus of the thalamus is generating sleep spindles in interaction with thalamocortical connections. The same system enables efficient encoding and processing during wakefulness. Thus, we examined if the triangular relationship between SpA, measures of intelligence and declarative learning reflect the efficiency of the thalamocortical system. As expected, SpA was associated with general cognitive ability, e.g. information processing speed. SpA was also associated with learning efficiency, however, not with overnight performance improvement in a declarative memory task. SpA might therefore reflect the efficiency of the thalamocortical network and can be seen as a marker for learning during encoding in wakefulness, i.e. learning efficiency.     

Spatiotemporal Correlations between Cytosolic and Mitochondrial Ca2+ Signals Using a Novel Red-Shifted Mitochondrial Targeted Cameleon

The transfer of Ca²⁺ from the cytosol into the lumen of mitochondria is a crucial process that impacts cell signaling in multiple ways. Cytosolic Ca²⁺ ([Ca²⁺]_cyto) can be excellently quantified with the ratiometric Ca²⁺ probe fura-2, while genetically encoded Förster resonance energy transfer (FRET)-based fluorescent Ca²⁺ sensors, the cameleons, are efficiently used to specifically measure Ca²⁺ within organelles. However, because of a significant overlap of the fura-2 emission with the spectra of the cyan and yellow fluorescent protein of most of the existing cameleons, the measurement of fura-2 and cameleons within one given cell is a complex task. In this study, we introduce a novel approach to simultaneously assess [Ca²⁺]_cyto and mitochondrial Ca²⁺ ([Ca²⁺]_mito) signals at the single cell level. In order to eliminate the spectral overlap we developed a novel red-shifted cameleon, D1GO-Cam, in which the green and orange fluorescent proteins were used as the FRET pair. This ratiometric Ca²⁺ probe could be successfully targeted to mitochondria and was suitable to be used simultaneously with fura-2 to correlate [Ca²⁺]_cyto and [Ca²⁺]_mito within same individual cells. Our data indicate that depending on the kinetics of [Ca²⁺]_cyto rises there is a significant lag between onset of [Ca²⁺]_cyto and [Ca²⁺]_mito signals, pointing to a certain threshold of [Ca²⁺]_cyto necessary to activate mitochondrial Ca²⁺ uptake. The temporal correlation between [Ca²⁺]_mito and [Ca²⁺]_cyto as well as the efficiency of the transfer of Ca²⁺ from the cytosol into mitochondria varies between different cell types. Moreover, slow mitochondrial Ca²⁺ extrusion and a desensitization of mitochondrial Ca²⁺ uptake cause a clear difference in patterns of mitochondrial and cytosolic Ca²⁺ oscillations of pancreatic beta-cells in response to D-glucose.     

Antigen-driven interactions with dendritic cells and expansion of Foxp3+ regulatory T cells occur in the absence of inflammatory signals

Foxp3+ regulatory T cells (Tregs) play a pivotal role in the maintenance of peripheral T cell tolerance and are thought to interact with dendritic cells (DC) in secondary lymphoid organs. We analyzed here the in vivo requirements for selective expansion of Ag-specific Treg vs CD4+CD25- effector T cells and engagement of Ag-specific Treg-DC interactions in secondary lymphoid organs. Using i.v. Ag delivery in the absence of inflammation, we found that CD4+CD25+Foxp3+ Tregs undergo vigorous expansion and accumulate whereas naive CD4+CD25-Foxp3- T cells undergo abortive activation. Quantifying directly the interactions between Tregs and CD11c+ DC, we found that Tregs establish cognate contacts with endogenous CD11c+ DC in spleen and lymph nodes at an early time point preceding their expansion. Importantly, we observed that as few as 10(3) Tregs selectively expanded by i.v. Ag injection are able to suppress B and T cell immune responses in mouse recipients challenged with the Ag. Our results demonstrate that Tregs are selectively mobilized by Ag recognition in the absence of inflammatory signals, and can induce thereafter potent tolerance to defined Ag targets.     

Different development of myelin basic protein agonist- and antagonist-specific human TCR transgenic T cells in the thymus and periphery

Myelin basic protein (MBP)-specific T cells are thought to play a role in the development of multiple sclerosis. MBP residues 111-129 compose an immunodominant epitope cluster restricted by HLA-DRB1*0401. The sequence of residues 111-129 of MBP (MBP(111-129)) differs in humans (MBP122:Arg) and mice (MBP122:Lys) at aa 122. We previously found that approximately 50% of human MBP(111-129) (MBP122:Arg)-specific T cell clones, including MS2-3C8 can proliferate in response to mouse MBP(111-129) (MBP122:Lys). However, the other half of T cell clones, including HD4-1C2, cannot proliferate in response to MBP(111-129) (MBP122:Lys). We found that MBP(111-129) (MBP122:Lys) is an antagonist for HD4-1C2 TCR, therefore, MS2-3C8 and HD4-1C2 TCRs are agonist- and antagonist-specific TCRs in mice, respectively. Therefore, we examined the development of HD4-1C2 TCR and MS2-3C8 TCR transgenic (Tg) T cells in the thymus and periphery. We found that dual TCR expression exclusively facilitates the development of MBP(111-129) TCR Tg T cells in the periphery of HD4-1C2 TCR/HLA-DRB1*0401 Tg mice although it is not required for their development in the thymus. We also found that MS2-3C8 TCR Tg CD8(+) T cells develop along with MS2-3C8 TCR Tg CD4(+) T cells, and that dual TCR expression was crucial for the development of MS2-3C8 TCR Tg CD4(+) and CD8(+) T cells in the thymus and periphery, respectively. These results suggest that thymic and peripheral development of MBP-specific T cells are different; however, dual TCR expression can facilitate their development.