The receptor-interacting serine-threonine kinase 3 (RIP3) is a key signaling molecule in the programmed necrosis (necroptosis) pathway. This pathway plays important roles in a variety of physiological and pathological conditions, including development, tissue damage response, and antiviral immunity. Here, we report the identification of a small molecule called (E)-N-(4-(N-(3-methoxypyrazin-2-yl)sulfamoyl)phenyl)-3-(5-nitrothiophene-2-yl)acrylamide--hereafter referred to as necrosulfonamide--that specifically blocks necrosis downstream of RIP3 activation. An affinity probe derived from necrosulfonamide and coimmunoprecipitation using anti-RIP3 antibodies both identified the mixed lineage kinase domain-like protein (MLKL) as the interacting target. MLKL was phosphorylated by RIP3 at the threonine 357 and serine 358 residues, and these phosphorylation events were critical for necrosis. Treating cells with necrosulfonamide or knocking down MLKL expression arrested necrosis at a specific step at which RIP3 formed discrete punctae in cells. These findings implicate MLKL as a key mediator of necrosis signaling downstream of the kinase RIP3.

Recent studies have unequivocally associated the fat mass and obesity-associated (FTO) gene with the risk of obesity. In vitro FTO protein is an AlkB-like DNA/RNA demethylase with a strong preference for 3-methylthymidine (3-meT) in single-stranded DNA or 3-methyluracil (3-meU) in single-stranded RNA. Here we report the crystal structure of FTO in complex with the mononucleotide 3-meT. FTO comprises an amino-terminal AlkB-like domain and a carboxy-terminal domain with a novel fold. Biochemical assays show that these two domains interact with each other, which is required for FTO catalytic activity. In contrast with the structures of other AlkB members, FTO possesses an extra loop covering one side of the conserved jelly-roll motif. Structural comparison shows that this loop selectively competes with the unmethylated strand of the DNA duplex for binding to FTO, suggesting that it has an important role in FTO selection against double-stranded nucleic acids. The ability of FTO to distinguish 3-meT or 3-meU from other nucleotides is conferred by its hydrogen-bonding interaction with the two carbonyl oxygen atoms in 3-meT or 3-meU. Taken together, these results provide a structural basis for understanding FTO substrate-specificity, and serve as a foundation for the rational design of FTO inhibitors.

In a single step, from [Cp*RuCl 2 ] 2 (Cp* ) η 5 -C 5 Me 5 ) and Li [BH 4 ], nido-1,2-(Cp*Ru) 2 (µ-H) 2 B 3 H 7 , 1, is produced in high yield. Addition of BH 3 ‚THF to 1 results in conversion to nido-1,2-(Cp*Ru) 2 (µ-H)B 4 H 9 , 2. Reaction of BH 3 ‚THF directly with [Cp*RuCl 2 ] 2 yields a mixture of 1 and 2. In two steps, a rhodium analogue, nido-2,3-(Cp*Rh) 2 B 3 H 7 , 9, is accessible by the reaction of [Cp*RhCl 2 ] 2 and Li [BH 4 ] to exclusively produce (Cp*Rh) 2 B 2 H 6 , 8, which adds BH 3 ‚THF to give 9 as the major product in a mixture. Reaction of BH 3 ‚THF directly with [Cp*RhCl 2 ] 2 yields the chloro derivative of 9, nido-1-Cl-2,3-(Cp*Rh) 2 B 3 H 6 , 11, in high yield via the intermediate positional isomer, nido-3-Cl-1,2-(Cp*Rh) 2 B 3 H 6 , 10. With high concentrations of Co 2 (CO) 8 , 1 reacts with Co 2 (CO) 8 to give nido-1-(Cp*Ru)-2-(Cp*RuCO)-3-Co(CO) 2 (µ 3 -CO)B 3 H 6 , 3, whereas low concentrations permit competitive degradation of 1 to yield arachno-(Cp*Ru)(CO)(µ-H)B 3 H 7 , 4. On the other hand, reaction of 11 with Co 2 (CO) 8 gives closo-1-Cl-6-{Co(CO) 2 }-2,3-(Cp*Rh) 2 (µ 3 -CO)B 3 H 3 , 12. Mild thermolysis of 3 results in loss of hydrogen and the formation of closo-6-Co(CO) 2 -2,3-(Cp*Ru) 2 (µ-CO)(µ 3 -CO)B 3 H 4 , 5, whereas thermolysis of 2 results in loss of hydrogen and formation of pileo-2,3-(Cp*Ru) 2 B 4 H 8 , 6, with a BH-capped square pyramidal structure. Finally, 6 reacts with Fe 2 (CO) 9 to yield pileo-6-Fe(CO) 3 -2,3-(Cp*Ru) 2 (µ 3 -CO)B 4 H 4 , 7, with a BH-capped octahedral cluster structure. The overall isolated yield of 7, formed in four steps from [Cp*RuCl 2 ] 2 , is ≈50% and evidences good control of reactivity.

The liver-specific importer organic anion transporting polypeptide 1b2 (Oatp1b2, Slco1b2, also known as Oatp4 and Lst-1) and its human orthologs OATP1B1/1B3 transport a large variety of chemicals. Oatp1b2-null mice were engineered by homologous recombination and their phenotype was characterized. Oatp1b2 protein was absent in livers of Oatp1b2-null mice. Oatp1b2-null mice develop normally and breed well. However, adult Oatp1b2-null mice had moderate conjugated hyperbilirubinemia. Compared with wild-types, Oatp1b2-null mice had similar hepatic messenger RNA expression of most transporters examined except a higher Oatp1a4 but lower organic anion transporter 2. Intra-arterial injection of the mushroom toxin phalloidin (an Oatp1b2-specific substrate identified in vitro) caused cholestasis in wild-type mice but not in Oatp1b2-null mice. Hepatic uptake of fluorescence-labeled phalloidin was absent in Oatp1b2-null mice. Three hours after administration of microcystin-LR (a blue-green algae toxin), the binding of microcystin-LR to hepatic protein phosphatase 1/2a was much lower in Oatp1b2-null mice compared with wild-type mice. In contrast, Oatp1b2-null mice were transiently protected from decrease in bile flow induced by estradiol-17beta-D-glucuronide, a common substrate for Oatps. Oatp1b2-null mice were completely resistant to the hepatotoxicity induced by phalloidin and microcystin-LR, but were similarly sensitive to alpha-amanitin-induced hepatotoxicity compared with wild-type mice. In conclusion, Oatp1b2-null mice display altered basic physiology and markedly decreased hepatic uptake/toxicity of phalloidin and microcystin-LR. Oatp1b2-null mice are useful in elucidating the role of Oatp1b2 and its human orthologs OATP1B1/1B3 in hepatic uptake and systemic disposition of toxic chemicals and therapeutic drugs.

Late-stage diversification of natural products is an efficient way to generate natural product derivatives for drug discovery and chemical biology. Benefiting from the development of site-selective synthetic methodologies, late-stage diversification of natural products has achieved notable success. This outlook will outline selected examples of novel methodologies for site-selective transformations of reactive functional groups and inert C–H bonds that enable late-stage diversification of complex natural products. Accordingly, late-stage diversification provides an opportunity to rapidly access various derivatives for modifying lead compounds, identifying cellular targets, probing protein–protein interactions, and elucidating natural product biosynthetic relationships.

To improve chemical cross-linking of proteins coupled with mass spectrometry (CXMS), we developed a lysine-targeted enrichable cross-linker containing a biotin tag for affinity purification, a chemical cleavage site to separate cross-linked peptides away from biotin after enrichment, and a spacer arm that can be labeled with stable isotopes for quantitation. By locating the flexible proteins on the surface of 70S ribosome, we show that this trifunctional cross-linker is effective at attaining structural information not easily attainable by crystallography and electron microscopy. From a crude Rrp46 immunoprecipitate, it helped identify two direct binding partners of Rrp46 and 15 protein-protein interactions (PPIs) among the co-immunoprecipitated exosome subunits. Applying it to E. coli and C. elegans lysates, we identified 3130 and 893 inter-linked lysine pairs, representing 677 and 121 PPIs. Using a quantitative CXMS workflow we demonstrate that it can reveal changes in the reactivity of lysine residues due to protein-nucleic acid interaction.DOI: http://dx.doi.org/10.7554/eLife.12509.001

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Angiotensin-(1-7) or its analogs attenuate the key features of acute lung injury and may present a promising therapeutic strategy for the treatment of this disease.