Proteolytic Processing of Nlrp1b Is Required for Inflammasome Activity

Nlrp1b is a NOD-like receptor that detects the catalytic activity of anthrax lethal toxin and subsequently co-oligomerizes into a pro-caspase-1 activation platform known as an inflammasome. Nlrp1b has two domains that promote oligomerization: a NACHT domain, which is a member of the AAA+ ATPase family, and a poorly characterized Function to Find Domain (FIIND). Here we demonstrate that proteolytic processing within the FIIND generates N-terminal and C-terminal cleavage products of Nlrp1b that remain associated in both the auto-inhibited state and in the activated state after cells have been treated with lethal toxin. Functional significance of cleavage was suggested by the finding that mutations that block processing of Nlrp1b also prevent the ability of Nlrp1b to activate pro-caspase-1. By using an uncleaved mutant of Nlrp1b, we established the importance of cleavage by inserting a heterologous TEV protease site into the FIIND and demonstrating that TEV protease processed this site and induced inflammasome activity. Proteolysis of Nlrp1b was shown to be required for the assembly of a functional inflammasome: a mutation within the FIIND that abolished cleavage had no effect on self-association of a FIIND-CARD fragment, but did reduce the recruitment of pro-caspase-1. Our work indicates that a post-translational modification enables Nlrp1b to function

VACANCY-CATION DISTRIBUTION IN NON STOICHIOMETRIC LAYERED IRON-TITANIUM CHALCOGENIDES

Sept chalcogénures lamellaires de fer et de titane, non stoechiométriques, ont été étudiés par spectroscopie Mössbauer, en relation avec des calculs de distribution statistique des cations et des lacunes. Les résultats obtenus, nous ont permis de déterminer la distribution des cations et des lacunes dans les différents plans, et d'identifier les différents sites de fer.In an extension of a previous study of layered iron titanium chalcogenides /1/, we have studied Mössbauer spectra of seven non-stoichiometric compounds, in the vicitity of the FeTi2S4 composition, in relation with statistical distribution calculations. The results, enabled us, mainly, to obtain informations on the cations-and-vacancy distribution, and to identify the different detected iron-sites

Design of a new family of inorganic compounds Ae(2)F(2)SnX(3) (Ae = Sr, Ba; x = S, Se) using rock salt and fluorite 2D building blocks

International audienceWe could predict the structure of a new family of compounds Ae2F2SnX3 (Ae ) Sr, Ba; X ) S, Se) from the stacking of known 2D building blocks of the rock salt and fluorite types. With a high-temperature ceramic method we have then succeeded to synthesize the four compounds Ba2F2SnS3, Ba2F2SnSe3, Sr2F2SnS3, and Sr2F2SnSe3. The structure refinements from X-ray powder diffraction patterns have confirmed the structure predictions and showed their good accuracy. The structure of the four compounds results from the alternated stacking of fluorite [Ae2F2] (Ae ) Sr, Ba) and distorted rock salt [SnX3] (X ) S, Se) 2D building blocks. As shown by band structure calculations, these blocks behave as a charge reservoir and a charge acceptor, respectively. Sr2F2SnS3 and Ba2F2- SnS3 are transparent with optical gaps of 3.06 and 3.21 eV, respectively. However, an attempt to obtain a transparent conductor by substituting Ba per La in Ba2F2SnS3 was unsuccessfu

STOICHIOMETRY DEPENDENCE OF ZEEMAN HYPERFINE INTERACTIONS IN Fe1+x Ti2(1+x)S4 (x = 0, 0.030, 0.052)

Le rôle de la méthode de préparation du traitement thermique et de la non stoechiométrie sur l'ordre cristallographique et les propriétés magnétiques du chalcogénure ternaire FeTi2S4, a été le sujet de contradictions ces dernières années. Afin de contribuer à l'étude de ces questions, nous avons pensé voir comment les paramètres mentionnés ci-dessus se reflètent dans les spectres Mössbauer. Les résultats obtenus entre 4,2 K et 300 K sont discutés par comparaison aux résultats cristallographiques et magnétiques antérieurs.The role of the method of preparation, of the heat treatment and of the non stoichiometry, on the crystallographic and magnetic ordering of the ternay chalcogenide FeTi2S4 is not well inderstood to date. In order to clarify these questions, or, at least, to give supplementary data for future discussions, we have looked how the parameters mentioned above are reflected in the Mössbauer spectra. The results obtained between 4.2 K and 300 K showed marked differences between stoichiometric and non stoichiometric samples, and small or no differences between the different heat treatments and the different methods of preparation, respectively, and are discussed in terms of crystallographic and magnetic ordering

Predictive approach for the design of improved HDT catalysts: Promoted Mo1-xWxS2 supported on gamma-alumina

International audienceAbstract In the field of hydrotreating (HDT) catalysis, density functional theory (DFT) calculations are of great help to explore new active phases on the basis of volcano curve relationships correlating HDT activities and the sulfur–metal (S–M) bond energy chemical descriptor, calculated in transition metal sulfides catalysts. In the present study, we synthesize Mo1−xWxS2 solid solutions supported on γ-alumina. For non-promoted systems, the catalytic tests reveal that a continuous and linear evolution of the catalytic activity is obtained for solid solutions for x varying between 0 and 1. As expected from the calculated S–M bond energy values, no synergy effect is observed in that case. For Ni and Co promoted Mo1−xWxS2 active phases (ternary metal sulfides), the S–M bond energy values determined with an interpolation model of the binary sulfides predict that NiMo1−xWxS2 phases should be more active than NiMoS and NiWS ones. In contrast, CoMo1−xWxS2 phases are expected to develop weak synergetical effect with respect to CoMoS and CoWS ones. Experiments performed on Co and Ni promoted Mo1−xWxS2 active phases confirmed the DFT-volcano curve prediction and an increment of about 30% in HDS catalytic activity is obtained for NiMo0.5W0.5S catalysts in both model molecule conversion and gas oil treatment