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Regulatory T cells (Tregs) suppress pro-inflammatory conventional T cell (Tconv) responses. As lipids impact cell signaling and function, we compare the lipid composition of CD4+ thymus-derived (t)Tregs and Tconvs. Lipidomics reveal constitutive enrichment of neutral lipids in Tconvs and phospholipids in tTregs. TNFR2-co-stimulated effector tTregs and Tconvs are both glycolytic, but only in tTregs are glycolysis and the tricarboxylic acid (TCA) cycle linked to a boost in fatty acid (FA) synthesis (FAS), supported by relevant gene expression. FA chains in tTregs are longer and more unsaturated than in Tconvs. In contrast to Tconvs, tTregs effectively use either lactate or glucose for FAS and rely on this process for proliferation. FASN and SCD1, enzymes responsible for FAS and FA desaturation, prove essential for the ability of tTregs to suppress Tconvs. These data illuminate how effector tTregs can thrive in inflamed or cancerous tissues with limiting glucose but abundant lactate levels. [Display omitted] • Human conventional (Tconv) and regulatory T (Treg) cells have distinct lipidomes • TNFR2-driven glycolysis links to fatty acid synthesis (FAS) in Tregs but not Tconvs • Treg proliferation relies on FAS fueled by glucose or lactate • Treg suppressive function relies on synthesis of unsaturated fatty acids de Kivit et al. reveal discerning lipidomes of conventional T cells (Tconvs) versus thymus-derived regulatory T cells (tTreg). Effector tTregs can use either glucose or lactate to synthesize long and unsaturated fatty acids, on which they rely for proliferation and suppressive function. These tTreg-specific properties may be therapeutically exploited. [ABSTRACT FROM AUTHOR]

The function of p53 is best understood in response to genotoxic stress, but increasing evidence suggests that p53 also plays a key role in the regulation of metabolic homeostasis. p53 and its family members directly influence various metabolic pathways, enabling cells to respond to metabolic stress. These functions are likely to be important for restraining the development of cancer but could also have a profound effect on the development of metabolic diseases, including diabetes. A better understanding of the metabolic functions of p53 family members may aid in the identification of therapeutic targets and reveal novel uses for p53-modulating drugs. [Copyright &y& Elsevier]

Abstract: Reverse proteolysis and transpeptidation lead to the generation of polypeptide sequences that cannot be inferred directly from genome sequences as they are post-translational phenomena. These phenomena have so far received little attention although the physiological consequences may reach far. The protease-mediated synthesis of several immunodominant MHC class I antigens was recently reported, underscoring its importance to immunity. Reverse proteolytic and transpeptidation mechanisms as well as conditions that favor successful protease-catalyzed synthetic events are discussed here. [Copyright &y& Elsevier]

Summary: The dipeptide boronic acid bortezomib, also termed VELCADE®, is a proteasome inhibitor now in use for the treatment of multiple myeloma, and its use for the treatment of other malignancies is being explored. We determined the crystal structure of the yeast 20S proteasome in complex with bortezomib to establish the specificity and binding mode of bortezomib to the proteasome''s different catalytically active sites. This structure should enable the rational design of new boronic acid derivatives with improved affinities and specificities for individual active subunits. [Copyright &y& Elsevier]

Invariant natural killer T (iNKT) cells are a subpopulation of T cells that are reactive with glycolipids that are bound by CD1d antigen-presenting molecules. a-Galactosylceramide (a-GalCer) is a synthetic glycolipid that is a potential treatment for several autoimmune diseases, infectious diseases and cancer. Its therapeutic effect can be traced back to its ability to bind CD1d and activate iNKT cells, which results in the production of T helper 1 (Th1) and Th2 cytokines. However, the effectiveness of a-GalCer therapy is limited by the opposing actions of Th1 and Th2 cytokines. The a-GalCer analogs OCH and the recently designed and synthesized C-glycosidic a-GalCer selectively activate one of two types of cytokine profiles, possibly because either reduced or enhanced overall stability of the CD1d¿glycolipid¿T-cell-receptor complex leads to a higher potency in vivo, compared with the parent compound. These discoveries boost the potential of glycolipid-based therapies. [Copyright &y& Elsevier]

Abstract: The synthesis of a multiple tritiated analog of KRN7000 (α-galactosyl ceramide) is described, enabling further studies to quantitate the affinity of KRN7000 for its receptor and to study its pharmacokinetic properties. [Copyright &y& Elsevier]

• Higher levels of protein are found in certain types of cancer. • This is attributed to overexpression of a key protein involved in proline biosynthesis. • Focused screening has for the first time identified a small fragment-like inhibitor (ProPI-1) of this protein target. • Mechanistic studies show ProPI-1 can attenuate proline biosynthesis in relevant cell types. • Phenotypic studies reveal that ProPI-1 can control cell proliferation in two different breast cancer cell types. Pyrroline-5-carboxylate reductase 1 (PYCR1) is the final enzyme involved in the biosynthesis of proline and has been found to be upregulated in various forms of cancer. Due to the role of proline in maintaining the redox balance of cells and preventing apoptosis, PYCR1 is emerging as an attractive oncology target. Previous PYCR1 knockout studies led to a reduction in tumor growth. Accordingly, a small molecule inhibitor of PYCR1 could lead to new treatments for cancer, and a focused screening effort identified pargyline as a fragment-like hit. We report the design and synthesis of the first tool compounds as PYCR1 inhibitors, derived from pargyline, which were assayed to assess their ability to attenuate the production of proline. Structural activity studies have revealed the key determinants of activity, with the most potent compound (4) showing improved activity in vitro in enzyme (IC 50 = 8.8 µM) and pathway relevant effects in cell-based assays. [ABSTRACT FROM AUTHOR]

Phospho-MurNAc-pentapeptide translocase (MraY) catalyzes the synthesis of Lipid I, a bacterial peptidoglycan precursor. As such, MraY is essential for bacterial survival and therefore is an ideal target for developing novel antibiotics. However, the understanding of its catalytic mechanism, despite the recently determined crystal structure, remains limited. In the present study, the kinetic properties of Bacillus subtilis MraY (BsMraY) were investigated by fluorescence enhancement using dansylated UDP-Mur- NAc-pentapeptide and heptaprenyl phosphate (C35-P, shortchain homolog of undecaprenyl phosphate, the endogenous substrate ofMraY)as second substrate. Varying the concentrations of both of these substrates and fitting the kinetics data to two-substrate models showed that the concomitant binding of both UDPMurNAc- pentapeptide-DNS and C35-P to the enzyme is required before the release of the two products, Lipid I andUMP.Webuilt a model of BsMraY and performed docking studies with the substrate C35-P to further deepen our understanding of how MraY accommodates this lipid substrate. Based on these modeling studies, a novel catalytic role was put forward for a fully conserved histidine residue inMraY(His-289 in BsMraY), which has been experimentally confirmed to be essential for MraY activity. Using the current model of BsMraY, we propose that a small conformational change is necessary to relocate the His-289 residue, such that the translocase reaction can proceed via a nucleophilic attack of the phosphate moiety of C35-P on bound UDP-MurNAc-pentapeptide. [ABSTRACT FROM AUTHOR]