Recombinant tandem of pore-domains in a Weakly Inward rectifying K+ channel 2 (TWIK2) forms active lysosomal channels

Recombinant TWIK2 channels produce weak basal background K+ currents. Current amplitudes depend on the animal species the channels have been isolated from and on the heterologous system used for their re-expression. Here we show that this variability is due to a unique cellular trafficking. We identified three different sequence signals responsible for the preferential expression of TWIK2 in the Lamp1-positive lysosomal compartment. Sequential inactivation of tyrosine-based (Y(308)ASIP) and di-leucine-like (E266LILL and D(282)EDDQVDIL) trafficking motifs progressively abolishes the targeting of TWIK2 to lysosomes, and promotes its functional relocation at the plasma membrane. In addition, TWIK2 contains two N-glycosylation sites (N(79)AS and N(85)AS) on its luminal side, and glycosylation is necessary for expression in lysosomes. As shown by electrophysiology and electron microscopy, TWIK2 produces functional background K+ currents in the endolysosomes, and its expression affects the number and mean size of the lysosomes. These results show that TWIK2 is expressed in lysosomes, further expanding the registry of ion channels expressed in these organelles

Unravelling the sex-specific diversity and functions of adrenal gland macrophages

Despite the ubiquitous function of macrophages across the body, the diversity, origin, and function of adrenal gland macrophages remain largely unknown. We define the heterogeneity of adrenal gland immune cells using single-cell RNA sequencing and use genetic models to explore the developmental mechanisms yielding macrophage diversity. We define populations of monocyte-derived and embryonically seeded adrenal gland macrophages and identify a female-specific subset with low major histocompatibility complex (MHC) class II expression. In adulthood, monocyte recruitment dominates adrenal gland macrophage maintenance in female mice. Adrenal gland macrophage sub-tissular distribution follows a sex-dimorphic pattern, with MHC class IIlow macrophages located at the cortico-medullary junction. Macrophage sex dimorphism depends on the presence of the cortical X-zone. Adrenal gland macrophage depletion results in altered tissue homeostasis, modulated lipid metabolism, and decreased local aldosterone production during stress exposure. Overall, these data reveal the heterogeneity of adrenal gland macrophages and point toward sex-restricted distribution and functions of these cells.</p

Non-Standard Errors

In statistics, samples are drawn from a population in a data-generating process (DGP). Standard errors measure the uncertainty in estimates of population parameters. In science, evidence is generated to test hypotheses in an evidence-generating process (EGP). We claim that EGP variation across researchers adds uncertainty: Non-standard errors (NSEs). We study NSEs by letting 164 teams test the same hypotheses on the same data. NSEs turn out to be sizable, but smaller for better reproducible or higher rated research. Adding peer-review stages reduces NSEs. We further find that this type of uncertainty is underestimated by participants

Acid-sensing ion channel 3 in retinal function and survival.

International audiencePURPOSE: Changes in extracellular pH occur in the retina and directly affect retinal activity and phototransduction. The authors analyzed the expression in rodent retina of ASIC3, a sensor of extracellular acidosis, and used ASIC3 knockout mice to explore its role in retinal function and survival. METHODS: The expression and the role of ASIC3 were examined by immunolocalization and by comparing retinas from wild-type and knockout mice at different ages through electroretinography, retinal histology (light and electron microscopy), expression of glial fibrillary acidic protein (GFAP), analysis of cell apoptosis (TUNEL assay), and patch-clamp recordings in primary cultures of retinal ganglion cells (RGCs). RESULTS: ASIC3 is present in the rod inner segment of photoreceptors and in horizontal and some amacrine cells. ASIC3 is also detected in RGCs but does not significantly contribute to ASIC currents recorded in cultured RGCs. At 2 to 3 months, knockout mice experience a 19% enhancement of scotopic electroretinogram a-wave amplitude and a concomitant increase of b-wave amplitude without alteration of retinal structure. Older (8-month-old) knockout mice have 69% and 64% reductions in scotopic a- and b-waves, respectively, and reductions in oscillatory potential amplitudes associated with complete disorganization of the retina and degenerating rod inner segments. GFAP and TUNEL staining performed at 8 and 12 months of age revealed an upregulation of GFAP expression in Müller cells and the presence of apoptotic cells in the inner and outer retina. CONCLUSIONS: Inactivation of ASIC3 enhances visual transduction at 2 to 3 months but induces late-onset rod photoreceptor death, suggesting an important role for ASIC3 in maintaining retinal integrity

Controlled interactions between silanol groups at the surface of sepiolite and an acrylate matrix: Consequences on the thermal and mechanical properties

International audienceElastomer filled with fibrous clay (sepiolite) was manufactured using a hydrophilic elastomer matrix, poly 2-hydroxyethylacrylate (PHEA). The surface silanol groups located onto the channel sides of the sepiolite were functionalized with both octyltrimethoxysilane (OTMS) and 3-methacryloxypropyltrimethoxysilane (MPTMS), which form covalent bonds with the mineral surface and modify their properties. After the grafting of OTMS, PHEA is in contact with a non-polar chain, which prevents matrix-filler interactions. After the grafting of MPTMS, covalent bonds are formed between the acrylate groups of PHEA and MPTMS, which increase the matrix-filler interactions. After functionalization, there is no change in the structural and zeolitic water of the sepiolite which conserves its hydrophilic character. So, an equivalent distribution of the pristine and modified sepiolite is detected in the elastomeric matrices on transmission electron microscopy views of ultramicrotome cuts. The elastomeric macroscopic behavior is therefore related to the PHEA-sepiolite interactions. We show that the stronger the host-matrix interactions, the more important is the reinforcement effect. A direct relation between the interaction strength and the improvement of the mechanical properties was established. The control of the nature, quantity, and localization of the molecules grafted on the sepiolite surface allows us to manage the mechanical properties

Atypical Membrane-Anchored Cytokine MIF in a Marine Dinoflagellate

International audienceMacrophage Migration Inhibitory Factors (MIF) are pivotal cytokines/chemokines for vertebrate immune systems. MIFs are typically soluble single-domain proteins that are conserved across plant, fungal, protist, and metazoan kingdoms, but their functions have not been determined in most phylogenetic groups. Here, we describe an atypical multidomain MIF protein. The marine dinoflagellate Lingulodinium polyedra produces a transmembrane protein with an extra-cytoplasmic MIF domain, which localizes to cell-wall-associated membranes and vesicular bodies. This protein is also present in the membranes of extracellular vesicles accumulating at the secretory pores of the cells. Upon exposure to biotic stress, L. polyedra exhibits reduced expression of the MIF gene and reduced abundance of the surface-associated protein. The presence of LpMIF in the membranes of secreted extracellular vesicles evokes the fascinating possibility that LpMIF may participate in intercellular communication and/or interactions between free-living organisms in multispecies planktonic communities

Fibre reinforcement of elastomers: nanocomposites based on sepiolite and poly(hydroxyethyl acrylate)

International audienceThe reinforcement of poly(hydroxyethyl acrylate) provided by sepiolite particles has been analysed. Stress-strain measurements at equilibrium, as well as swelling experiments, were carried out on the unfilled and filled polymers. The state of dispersion of the filler was characterized by transmission electron microscopy. Moreover, an evaluation of chain orientation by infrared dichroism reveals a high orientation level in the filled system. The strong interaction between the two phases, combined with a good dispersion and a high shape factor of these clay particles, explain the improvement of the mechanical properties of the composites with respect to the pure polymer

Maya Blue as natural coloring fillers in a multi-scale polymer-clay nanocomposite

International audienceThe purpose of this article is to understand the underlying mechanisms of the potential of nanohybrids. Two types of fillers were dispersed in a biocompatible organic matrix, poly-(hydroxyethyl acrylate) (PHEA): either a natural fibrous clay (pristine sepiolite), or a natural nanopigment (Maya Blue). In comparison with the pure polymer, the mechanical properties of the composites have been already greatly improved with the addition a small amount of Maya Blue. However the PHEA/pristine sepiolite nanohybrid gives better results than the PHEA/Maya Blue for the same ratio of fillers. The stress-strain curves (with unloading and reloading) show that the presence of indigo modifies the interactions between the filler and the matrix. These analyses demonstrate that there is a direct correlation between the filler/matrix local interactions, the dispersion of the fillers and some macroscopical mechanical properties

Thermal and menthol stress induce different cellular events during sea anemone bleaching

International audienceCnidarian-dinoflagellate symbiosis disruption and subsequent bleaching are major concerns, especially regarding their ecological consequences on coral reefs and temperate coralligenous communities. Cnidarian bleaching is caused by a variety of environmental stressors, such as elevated seawater temperature associated with global climate change, and by pollutants, such as herbicides and metals. Several cellular events have been described to explain symbiosis dysfunction and bleaching. Excess or damaged Symbiodinium symbionts are removed through a variety of mechanisms, including exocytosis, apoptosis, necrosis and autophagy. However, few studies have compared in the same species the relative involvement of these mechanisms, according to the stress inducing the bleaching. In this study, we used two different treatments —temperature and menthol— to induce bleaching in the sea anemone Anemonia viridis. By monitoring the ultrastructural tissue modifications, in control specimens we observed a basal rate of in situ symbiont digestion —or symbiophagy— induced by starvation. Symbiophagy was strongly induced in menthol-treated specimens and was the main cellular process of bleaching, whereas apoptosis and necrosis predominated in hyperthermal-induced bleaching. These results suggested a host effect through autophagy in menthol-treated specimens. These observations also suggested that symbiont removal may result from reengagement of the phagosomal maturation process in the host. These overall data demonstrate that several Symbiodinium cell removal mechanisms coexist and that stressors can activate one or more of these pathways, depending on the stress type, intensity or duration