Mouse Sphingosine Kinase 1a Is Negatively Regulated through Conventional PKC-Dependent Phosphorylation at S373 Residue

Sphingosine kinase is a lipid kinase that converts sphingosine into sphingosine-1-phosphate, an important signaling molecule with intracellular and extracellular functions. Although diverse extracellular stimuli influence cellular sphingosine kinase activity, the molecular mechanisms underlying its regulation remain to be clarified. In this study, we investigated the phosphorylation-dependent regulation of mouse sphingosine kinase (mSK) isoforms 1 and 2. mSK1a was robustly phosphorylated in response to extracellular stimuli such as phorbol ester, whereas mSK2 exhibited a high basal level of phosphorylation in quiescent cells regardless of agonist stimulation. Interestingly, phorbol ester-induced phosphorylation of mSK1a correlated with suppression of its activity. Chemical inhibition of conventional PKCs (cPKCs) abolished mSK1a phosphorylation, while overexpression of PKC alpha, a cPKC isoform, potentiated the phosphorylation, in response to phorbol ester. Furthermore, an in vitro kinase assay showed that PKC alpha directly phosphorylated mSK1a. In addition, phosphopeptide mapping analysis determined that the S373 residue of mSK1a was the only site phosphorylated by cPKC. Interestingly, alanine substitution of S373 made mSK1a refractory to the inhibitory effect of phorbol esters, whereas glutamate substitution of the same residue resulted in a significant reduction in mSK1a activity, suggesting the significant role of this phosphorylation event. Taken together, we propose that mSK1a is negatively regulated through cPKC-dependent phosphorylation at S373 residueopen

Kynurenine–3–monooxygenase inhibition prevents multiple organ failure in rodent models of acute pancreatitis

Acute pancreatitis (AP) is a common and devastating inflammatory condition of the pancreas that is considered to be a paradigm of sterile inflammation leading to systemic multiple organ dysfunction syndrome (MODS) and death1,2 Acute mortality from AP-MODS exceeds 20%3 and for those who survive the initial episode, their lifespan is typically shorter than the general population4. There are no specific therapies available that protect individuals against AP-MODS. Here, we show that kynurenine-3-monooxygenase (KMO), a key enzyme of tryptophan metabolism5, is central to the pathogenesis of AP-MODS. We created a mouse strain deficient for Kmo with a robust biochemical phenotype that protected against extrapancreatic tissue injury to lung, kidney and liver in experimental AP-MODS. A medicinal chemistry strategy based on modifications of the kynurenine substrate led to the discovery of GSK180 as a potent and specific inhibitor of KMO. The binding mode of the inhibitor in the active site was confirmed by X-ray co-crystallography at 3.2 Å resolution. Treatment with GSK180 resulted in rapid changes in levels of kynurenine pathway metabolites in vivo and afforded therapeutic protection against AP-MODS in a rat model of AP. Our findings establish KMO inhibition as a novel therapeutic strategy in the treatment of AP-MODS and open up a new area for drug discovery in critical illness

Mucopolysaccharidoses : quand y penser ?

International audienceLes mucopolysaccharidoses sont des maladies de surcharge lysosomales, secondaires à l'accumulation de mucopolysaccharides. La mucopolysaccharidose de type 1 est la plus fréquente et touche entre 0,69 et 1,66 nouveau-né sur 100 000. Les manifestations cliniques des mucopolysaccharidoses sont de sévérités variables avec des formes létales in utero et des formes atténuées diagnostiquées à l'âge adulte. Les symptômes des plus fréquents sont une petite taille, une dysmorphie faciale, l'atteinte rhumatologique qui peut mimer un rhumatisme inflammatoire chronique, les atteintes osseuses axiales et périphériques, l'hépatosplénomégalie, et un canal carpien précoce. En fonction du type de mucopolysaccharidose, une atteinte cornéenne, cardiaque ou du système nerveux central est possible. Le dépistage repose sur l'analyse des glycosaminoglycanes urinaires, qui oriente vers le type de mucopolysaccharidose. Le dosage de l'enzyme déficiente et la recherche de mutation confirment le diagnostic. La reconnaissance des mucopolysaccharidoses est importante pour la prise en charge du patient et le dépistage familial. De plus, un traitement spécifique par enzymothérapie substitutive existe pour certains types de mucopolysaccharidoses. Les mucopolysaccharidoses étant des maladies systémiques, le médecin interniste a un rôle essentiel dans leur reconnaissance et diagnostic.</div

Lower crustal vs. mantle wedge fingerprint in the Ecuadorian arc magmas: Contribution of Pb isotopes from the Cotopaxi volcano

International audiencePb isotopes are very sensitive to continental crustal contamination. With these isotopes, we are able to discriminate the contribution of the lower crust from that of the upper crust. With the objective of constraining the genesis of arc magmas by focusing here on the role of the continental crust, we propose a geochemical study on eruptive products of the Cotopaxi volcano. This choice is based on the fact that Cotopaxi is constructed on a thick continental crust and that its magmatic series span a large geochemical diversity, from basaltic andesites to rhyolites (Garrison et al., 2006, Garrison et al., 2011). We provide here 23 new high-precision Pb isotope data obtained on tephras, covering the range from andesites to rhyolites, over a period ranging from pre-Holocene to historical times. Isotopes variations are comprised between 18.980 and 18.923 for 206 Pb/ 204 Pb, 15.629 and 15.640 for 207 Pb/ 204 Pb and 38.717 and 38.765 for 208 Pb/ 204 Pb. Comparing these results with published data, we observe that our data have restricte