The crystal structure of the plant small GTPase OsRac1 reveals its mode of binding to NADPH oxidase

This research was originally published in Journal of Biological Chemistry. Ken-ichi Kosami, Izuru Ohki, Minoru Nagano, Kyoko Furuita, Toshihiko Sugiki, Yoji Kawano, Tsutomu Kawasaki, Toshimichi Fujiwara, Atsushi Nakagawa, Ko Shimamoto and Chojiro Kojima. The crystal structure of the plant small GTPase OsRac1 reveals its mode of binding to NADPH oxidase. Journal of Biological Chemistry. 2014; 289, 28569-28578. © the American Society for Biochemistry and Molecular Biology

Biophysical analysis of the plant-specific GIPC sphingolipids reveals multiple modes of membrane regulation

The plant plasma membrane (PM) is an essential barrier between the cell and the external environment, controlling signal perception and transmission. It consists of an asymmetrical lipid bilayer made up of three different lipid classes: sphingolipids, sterols, and phospholipids. The glycosyl inositol phosphoryl ceramides (GIPCs), representing up to 40% of total sphingolipids, are assumed to be almost exclusively in the outer leaflet of the PM. However, their biological role and properties are poorly defined. In this study, we investigated the role of GIPCs in membrane organization. Because GIPCs are not commercially available, we developed a protocol to extract and isolate GIPC-enriched fractions from eudicots (cauliflower and tobacco) and monocots (leek and rice). Lipidomic analysis confirmed the presence of trihydroxylated long chain bases and 2-hydroxylated very long-chain fatty acids up to 26 carbon atoms. The glycan head groups of the GIPCs from monocots and dicots were analyzed by gas chromatograph–mass spectrometry, revealing different sugar moieties. Multiple biophysics tools, namely Langmuir monolayer, ζ-Potential, light scattering, neutron reflectivity, solid state 2H-NMR, and molecular modeling, were used to investigate the physical properties of the GIPCs, as well as their interaction with free and conjugated phytosterols. We showed that GIPCs increase the thickness and electronegativity of model membranes, interact differentially with the different phytosterols species, and regulate the gel-to-fluid phase transition during temperature variations. These results unveil the multiple roles played by GIPCs in the plant PM.Vers un modèle intégratif de la bicouche lipidique de la membrane plasmique végétaleDéveloppement d’une infrastructure française distribuée pour la métabolomique dédiée à l’innovatio

The Non-Thermal Effects of Pulsed Ultrasound Irradiation on the Development of Disuse Muscle Atrophy in Rat Gastrocnemius Muscle

This study examined the effects of therapeutic pulsed ultrasound (US) on the development of disuse muscle atrophy in rat gastrocnemius muscle. Male Wistar rats were randomly distributed into control, immobilization (Im), sham US, and US groups. In the Im, sham US and US groups, the bilateral ankle joints of each rat were immobilized in full plantar flexion with a plaster cast for a 4-wk period. The pulsed US (frequency, 1 MHz; intensity, 1.0 W/cm2; pulsed mode 1:4; 15 min) was irradiated to the gastrocnemius muscle in the US group over a 4-wk immobilization period. The pulsed US irradiation delivered only non-thermal effects to the muscle. In conjunction with US irradiation, 5-bromo-2\u27-deoxyuridine (BrdU) was injected subcutaneously to label the nuclei of proliferating satellite cells 1 h before each pulsed US irradiation. Immobilization resulted in significant decreases in the mean diameters of type I, IIA and IIB muscle fibers of the gastrocnemius muscle in the Im, sham US and US groups compared with the control group. However, the degrees of muscle fiber atrophy for all types were significantly lower in the US group compared with the Im and sham US groups. Although the number of capillaries and the concentrations of insulin-like growth factor and basic fibroblast growth factor did not change in the muscle, the number of BrdU-positive nuclei in the muscle was significantly increased by pulsed US irradiation in the US group. The results of this study suggest that pulsed US irradiation inhibits the development of disuse muscle atrophy partly via activation of satellite cells

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements