Precise mapping of the CD95 pre-ligand assembly domain.

International audiencePre-association of CD95 at the plasma membrane is mandatory for efficient death receptor signaling. This homotrimerization occurs through self-association of an extracellular domain called the pre-ligand assembly domain (PLAD). Using novel molecular and cellular tools, we confirmed that CD95-PLAD is necessary to promote CD95 multimerization and plays a pivotal role in the transmission of apoptotic signals. However, while a human CD95 mutant deleted of the previously described PLAD domain (amino acids 1 to 66) fails to interact with its wild-type counterpart and trigger autonomous cell death, deletion of amino acids 1 to 42 does not prevent homo- or hetero (human/mouse)-oligomerization of CD95, and thus does not alter transmission of the apoptotic signal. Overall, these findings indicate that the region between amino acids 43 to 66 corresponds to the minimal motif involved in CD95 homotypic interaction and is necessary to convey an efficient apoptotic signal. Interfering with this PLAD may represent a new therapeutic strategy for altering CD95-induced apoptotic and non-apoptotic signals

Modulation of AMPA receptor surface diffusion restores hippocampal plasticity and memory in Huntington’s disease models

International audienc

Expression of specific inflammasome gene modules stratifies older individuals into two extreme clinical and immunological states

Low-grade, chronic inflammation has been associated with many diseases of aging, but the mechanisms responsible for producing this inflammation remain unclear. Inflammasomes can drive chronic inflammation in the context of an infectious disease or cellular stress, and they trigger the maturation of interleukin-1β (IL-1β). Here we find that the expression of specific inflammasome gene modules stratifies older individuals into two extremes: those with constitutive expression of IL-1β, nucleotide metabolism dysfunction, elevated oxidative stress, high rates of hypertension and arterial stiffness; and those without constitutive expression of IL-1β, who lack these characteristics. Adenine and N4-acetylcytidine, nucleotide-derived metabolites that are detectable in the blood of the former group, prime and activate the NLRC4 inflammasome, induce the production of IL-1β, activate platelets and neutrophils and elevate blood pressure in mice. In individuals over 85 years of age, the elevated expression of inflammasome gene modules was associated with all-cause mortality. Thus, targeting inflammasome components may ameliorate chronic inflammation and various other age-associated conditions

The Naturally Processed CD95L Elicits a c-Yes/Calcium/PI3K-Driven Cell Migration Pathway

Patients affected by chronic inflammatory disorders display high amounts of soluble CD95L. This homotrimeric ligand arises from the cleavage by metalloproteases of its membrane-bound counterpart, a strong apoptotic inducer. In contrast, the naturally processed CD95L is viewed as an apoptotic antagonist competing with its membrane counterpart for binding to CD95. Recent reports pinpointed that activation of CD95 may attract myeloid and tumoral cells, which display resistance to the CD95-mediated apoptotic signal. However, all these studies were performed using chimeric CD95Ls (oligomerized forms), which behave as the membrane-bound ligand and not as the naturally processed CD95L. Herein, we examine the biological effects of the metalloprotease-cleaved CD95L on CD95-sensitive activated T-lymphocytes. We demonstrate that cleaved CD95L (cl-CD95L), found increased in sera of systemic lupus erythematosus (SLE) patients as compared to that of healthy individuals, promotes the formation of migrating pseudopods at the leading edge of which the death receptor CD95 is capped (confocal microscopy). Using different migration assays (wound healing/Boyden Chamber/endothelial transmigration), we uncover that cl-CD95L promotes cell migration through a c-yes/Ca2+/PI3K-driven signaling pathway, which relies on the formation of a CD95-containing complex designated the MISC for Motility-Inducing Signaling Complex. These findings revisit the role of the metalloprotease-cleaved CD95L and emphasize that the increase in cl-CD95L observed in patients affected by chronic inflammatory disorders may fuel the local or systemic tissue damage by promoting tissue-filtration of immune cells

Diversité des agricultures familiales

Dans un contexte d’interrogation sur les modèles agricoles et de profondes transformations des agricultures et des marchés, cet ouvrage s’attache à revisiter la diversité des formes familiales de production et leurs mutations de par le monde. Dès lors, l’analyse intègre les liens aux marchés, aux territoires et à l’Ailleurs — par le fait migratoire — les enjeux d’autonomie et de sécurité alimentaire, les stratégies de survie et d’accumulation ainsi que les formes d’action collective et politique. L’ouvrage est construit autour de dix-huit études de cas, menées dans les cinq continents. Elles ont toutes été conduites avec un cadre méthodologique, identique et original, inspiré du Sustainable Rural Livehoods (cadre d’identification des moyens de subsistance durables en milieu rural). Revisitée pour cet ouvrage, cette méthode d’observations et d’analyses permet aux auteurs de préciser finement « ce qui fait famille », d’analyser les adaptations du travail des actifs familiaux et les mettre en perspective avec le contexte territorial et les politiques publiques de chaque pays. Écrit à plusieurs mains, par un réseau de chercheurs, cet ouvrage contribue autant à l’approfondissement des savoirs scientifiques sur les agricultures familiales dans le monde qu’à la mise à l’épreuve d’un cadre méthodologique d’analyse et d’observations en milieu rural. Il vise un public de chercheurs, d’enseignants et d’étudiants, agronomes, économistes, sociologues et historiens. Les experts du développement agricole et rural y trouveront un grand intérêt. Plus largement, toute personne qui s’intéresse aux agricultures familiales et à leurs évolutions dans divers contextes sociaux trouvera avantage à cette lecture. Les chercheurs qui ont coordonné cet ouvrage sont agronomes, économistes et géographes, au Cirad ou à l’Inra où ils mènent des recherches sur les systèmes agricoles familiaux à des échelles locales, nationales ou internationales. Cet ouvrage est le fruit d’une démarche de recherche collective et partagée permettant à de nombreux scientifiques des pays du Sud d’exprimer la diversité des réalités agraires contemporaines. Certains coordinateurs ou auteurs de cet ouvrage ont également collaboré à Agricultures familiales et mondes à venir, titre paru en 2014 chez Quae. Ce livre est également disponible en anglais sous le titreDiversity of Family Farming Around the Worldauprès des éditions Springer -www.springer.co

Cutting edge : modulation of fas-mediated apoptosis by lipid rafts in T lymphocytes.

Abstract In type I cells, Fas-mediated cell death requires cytoplasmic membrane subdomains called microdomains or lipid rafts. On the contrary, Fas signaling is independent of these structures in type II cells. We report that in human T cells, CD28, CD59, and CD55 are all localized into lipid rafts and that CD28 is concentrated into microdomains enriched in ganglioside GM1, whereas CD59 and CD55 are not. Moreover, CD28 cross-linking leads to the formation of lipid raft clusters which exclude CD59 and CD55, and reciprocally. Coligation of Fas with CD55 or CD59 inhibits the apoptotic signal, whereas CD28 recruitment amplifies the Fas signaling pathway. Therefore, we conclude that 1) different types of microdomains exist on the cell surface, with distinct functional properties and 2) the recruitment of these distinct structures may differentially modulate the Fas pathway. Moreover, our results demonstrate that Fas-induced apoptosis can be controlled at the level of the cytoplasmic membrane.</jats:p

Enhancing production and cytotoxic activity of polymeric soluble FasL-based chimeric proteins by concomitant expression of soluble FasL.

International audienceMembrane FasL is the natural trigger of Fas-mediated apoptosis. A soluble homotrimeric counterpart (sFasL) also exists which is very weakly active, and needs oligomerization beyond its trimeric state to induce apoptosis. We recently generated a soluble FasL chimera by fusing the immunoglobulin-like domain of the leukemia inhibitory factor receptor gp190 to the extracellular region of human FasL, which enabled spontaneous dodecameric homotypic polymerization of FasL. This polymeric soluble human FasL (pFasL) displayed anti-tumoral activity in vitro and in vivo without systemic cytotoxicity in mouse. In the present work, we focused on the improvement of pFasL, with two complementary objectives. First, we developed more complex pFasL-based chimeras that contained a cell-targeting module. Secondly, we attempted to improve the production and/or the specific activity of pFasL and of the cell-targeting chimeras. We designed two chimeras by fusing to pFasL the extracellular portions of the HLA-A2 molecule or of a human gamma-delta TCR, and analyzed the consequences of co-expressing these molecules or pFasL together with sFasL on their heterotopic cell production. This strategy significantly enhanced the production of pFasL and of the two chimeras, as well as the cytotoxic activity of the two chimeras but not of pFasL. These results provide the proof of concept for an optimization of FasL-based chimeric proteins for a therapeutic use