The endogenous lipid signaling agent oleoylethanolamide (OEA) has recently been described as a peripherally acting agent that reduces food intake and body weight gain in rat feeding models. This paper presents evidence that OEA is an endogenous ligand of the orphan receptor GPR119, a G protein-coupled receptor (GPCR) expressed predominantly in the human and rodent pancreas and gastrointestinal tract and also in rodent brain, suggesting that the reported effects of OEA on food intake may be mediated, at least in part, via the GPR119 receptor. Furthermore, we have used the recombinant receptor to discover novel selective small-molecule GPR119 agonists, typified by PSN632408, which suppress food intake in rats and reduce body weight gain and white adipose tissue deposition upon subchronic oral administration to high-fat-fed rats. GPR119 therefore represents a novel and attractive potential target for the therapy of obesity and related metabolic disorders.

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Human immunodeficiency virus (HIV) RNase H activity is essential for the synthesis of viral DNA by HIV reverse transcriptase (HIV-RT). RNA cleavage by RNase H requires the presence of divalent metal ions, but the role of metal ions in the mechanism of RNA cleavage has not been resolved. We measured HIV RNase H activity associated with HIV-RT protein in the presence of different concentrations of either Mg2+, Mn2+, Co2+ or a combination of these divalent metal ions. Polymerase-independent HIV RNase H was similar to or more active with Mn2+ and Co2+ compared with Mg2+. Activation of RNase H by these metal ions followed sigmoidal dose-response curves suggesting cooperative metal ion binding. Titration of Mg2+-bound HIV RNase H with Mn2+ or Co2+ ions generated bell-shaped activity dose-response curves. Higher activity could be achieved through simultaneous binding of more than one divalent metal ion at intermediate Mn2+ and Co2+ concentrations, and complete replacement of Mg2+ occurred at higher Mn2+ or Co2+ concentrations. These results are consistent with a two-metal ion mechanism of RNA cleavage as previously suggested for a number of polymerase-associated nucleases. In contrast, the structurally highly homologous RNase HI from Escherichia coli is most strongly activated by Mg2+, is significantly inhibited by submillimolar concentrations of Mn2+ and most probably cleaves RNA via a one-metal ion mechanism. Based on this difference in active site structure, a series of small molecule N-hydroxyimides was identified with significant enzyme inhibitory potency and selectivity for HIV RNase H.

GPR119 is a G protein-coupled receptor expressed predominantly in the pancreas (b-cells) and gastrointestinal tract (enteroendocrine cells) in humans. De-orphanization of GPR119 has revealed two classes of possible endogenous ligands, viz., phospholipids and fatty acid amides. Of these, oleoylethanolamide (OEA) is one of the most active ligands tested so far. This fatty acid ethanolamide is of particular interest because of its known effects of reducing food intake and body weight gain when administered to rodents. Agonists at the GPR119 receptor cause an increase in intracellular cAMP levels via G as coupling to adenylate cyclase. In vitro studies have indicated a role for GPR119 in the modulation of insulin release by pancreatic b-cells and of GLP-1 secretion by gut enteroendocrine cells. The effects of GPR119 agonists in animal models of diabetes and obesity are reviewed, and the potential value of such compounds in future therapies for these conditions is discussed.

The viral antigen specificity of primary cytotoxic T cell responses (CTL) of H-2b, H-2k, H-2q, H-2s, H-2f and some H-2-recombinant mice against lymphocytic choriomeningitis virus (LCMV-WE isolate) as well as the specificity of some CTL clones and T cell lines was defined on target cells infected with vaccinia-recombinant virus expressing nucleoprotein (Np) or glycoprotein (Gp). Np was recognized together with H-2q (Dq), H-2d (DLd), H-2s and H-2b (Db). Gp specificity was restricted to H-2f and H-2b (Kb and Db); H-2k-restricted CTL anti-LCMV responses were neither Gp nor Np specific. The anti-viral protective immunity induced by vaccinia-Gp or vaccinia-Np recombinants was evaluated in mice. In vivo protection was T cell mediated by class I restricted Ly-2+ T cells; it correlated well with the CTL specificity defined in vitro. Some of the CTL-nonresponder H-2 allele plus Np or H-2 plus Gp combinations were, however, protected to variable and low degrees by vaccinia-recombinant viruses, indicating that anti-viral protection is a more sensitive readout for CTL activity than the in vitro assay. For example, B10.D2 H-2d mice generated measurable CTL responses only to Np; after immunization with a vaccinia-Np recombinant, LCMV titers were 10(4) times lower in spleens than in vaccinia-primed controls. Although vaccinia-Gp-immunized BALB/c mice revealed no CTL activity in vitro, they nevertheless had 10(2) times lower LCMV titers in spleens than controls. Anti-viral protection, particularly in low-responder combinations, was usually short-lived and diminished after 3 weeks. In a high-responder situation, protection was of a longer duration (greater than 8 weeks). Vaccination with vaccinia-Np or Gp recombinants protected mice against lethal T cell-mediated lymphocytic choriomeningitis induced by LCMV or prevented the local footpad swelling reaction; these in vivo effects were H-2 dependent and followed the identical roles established for CTL recognition in vitro.