This report identifies a novel gene encoding 15-oxoprostaglandin-⌬ 13 -reductase (PGR-2), which catalyzes the reaction converting 15-keto-PGE 2 to 13,14-dihydro-15-keto-PGE 2 . The expression of PGR-2 is up-regulated in the late phase of 3T3-L1 adipocyte differentiation and predominantly distributed in adipose tissue. Overexpression of PGR-2 in cells decreases peroxisome proliferator-activated receptor ␥ (PPAR␥)-dependent transcription and prohibits 3T3-L1 adipocyte differentiation without affecting expression of PPAR␥. Interestingly, we found that 15-keto-PGE 2 can act as a ligand of PPAR␥ to increase coactivator recruitment, thus activating PPAR␥-mediated transcription and enhancing adipogenesis of 3T3-L1 cells. Overexpression of 15-hydroxyprostaglandin dehydrogenase, which catalyzes the oxidation reaction of PGE 2 to form 15-keto-PGE 2, significantly increased PPAR␥-mediated transcription in a PGE 2 -dependent manner. Reciprocally, overexpression of wild-type PGR-2, but not the catalytically defective mutant, abolished the effect of 15-keto-PGE 2 on PPAR␥ activation. These results demonstrate a novel link between catabolism of PGE 2 and regulation of ligand-induced PPAR␥ activation.

Don't interrupt! Protein serotonylation has been implicated in living cells, yet its role remains poorly defined because of the lack of characterization tools. We synthesized a serotonin derivative to enable selective tagging of serotonylation and to investigate its effect on Ras; the latter displayed undisrupted interaction with Raf-1 at the Ras binding domain.

Background: The cell surface lectin Siglec-F is thought to preferentially recognize ligands modified with galactose 6-O-sulfate.Results: Siglec-F ligands are still present in leukocytes and lung tissue from mice lacking galactose 6-O-sulfotransferases.Conclusion: Ligands are restricted to specific cell types, but galactose 6-O-sulfotransferases are not required for ligand binding.Significance: This study refines our understanding of the biological ligands for Siglec-F.

We have previously developed the enabling techniques for sulfoglycomics based on mass spectrometry (MS) analysis of permethylated glycans, which preserves the attractive features of more reliable MS/MS sequencing compared with that performed on native glycans, while providing an easy way to separate and hence enrich the sulfated glycans. Unlike LC-MS/MS analysis of native glycans in negative ion mode that has been more widely in use, the characteristics and potential benefits of similar applications based on permethylated sulfated glycans have not been fully investigated. We report here the important features of reverse phase-based nanoLC-MS/MS analysis of permethylated sulfated glycans in negative ion mode and demonstrate that complementary sets of diagnostic fragment ions afforded can allow rapid identification of various fucosylated, sialylated sulfated glycotopes and definitive determination of the location of sulfate in a way difficult to achieve by other means. A parallel acquisition of both higher collision energy and trap-based MS2 coupled with a product dependent 1 is conceivably the most productive sulfoglycomic workflow currently possible and the manually curated fragmentation characteristics presented here will allow future developments in automating data analysis.