With the recent discoveries of novel forms of phospholipases A2 (PLA2s),2 new schemes for the roles of various PLA2s in lipid metabolism must be considered. The type II 14-kDa PLA2 isolated from human synovial fluid or platelet has many of the biochemical characteristics of the homologous snake venom and mammalian pancreatic PLA2s. It appears to function both as a cell-associated enzyme and extracellularly, where its expression and/or release is regulated by a variety of mediators such as cytokines or growth factors. The mammalian 85-kDa PLA2 purified from monocytic cells or platelets has no sequence homology to the 14-kDa PLA2 and exhibits biochemically different characteristics. It translocates from cytosol to particulate cell fractions in the presence of submicromolar levels of Ca2+ and has a substrate preference for sn-2-arachidonoyl-containing phospholipids. The cellular function and relative importance of these two enzymes in lipid metabolism remain to be determined. In this review, the biochemistry, localization, function, and regulation of these two distinct mammalian Ca(2+)-dependent PLA2 are compared.

TRAIL is a member of the tumor necrosis factor (TNF) family of cytokines which induces apoptotic cell death in a variety of tumor cell lines. It mediates its apoptotic effects through one of two receptors, DR4 and DR5, which are members of of the TNF receptor family, and whose cytoplasmic regions contain death domains. In addition, TRAIL also binds to 3 "decoy" receptors, DcR2, a receptor with a truncated death domain, DcR1, a glycosylphosphatidylinositol-anchored receptor, and OPG a secreted protein which is also known to bind to another member of the TNF family, RANKL. However, although apoptosis depends on the expression of one or both of the death domain containing receptors DR4 and/or DR5, resistance to TRAIL-induced apoptosis does not correlate with the expression of the "decoy" receptors. Previously, TRAIL has been described to bind to all its receptors with equivalent high affinities. In the present work, we show, by isothermal titration calorimetry and competitive enzyme-linked immunosorbent assay, that the rank order of affinities of TRAIL for the recombinant soluble forms of its receptors is strongly temperature dependent. Although DR4, DR5, DcR1, and OPG show similar affinities for TRAIL at 4°C, their rankordered affinities are substantially different at 37°C, with DR5 having the highest affinity (K D < 2 nM) and OPG having the weakest (K D ‫؍‬ 400 nM). Preferentially enhanced binding of TRAIL to DR5 was also observed at the cell surface. These results reveal that the rank ordering of affinities for protein-protein interactions in general can be a strong function of temperature, and indicate that sizeable, but hitherto unobserved, TRAIL affinity differences exist at physiological temperature, and should be taken into account in order to understand the complex physiological and/or pathological roles of TRAIL.

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Field tests of corn co-expressing two new delta-endotoxins from Bacillus thuringiensis (Bt) have demonstrated protection from root damage by western corn rootworm (Diabrotica virgifera virgifera LeConte). The level of protection exceeds that provided by chemical insecticides. In the bacterium, these proteins form crystals during the sporulation phase of the growth cycle, are encoded by a single operon, and have molecular masses of 14 kDa and 44 kDa. Corn rootworm larvae fed on corn roots expressing the proteins showed histopathological symptoms in the midgut epithelium.

Interleukin 1␤ (IL-1␤) up-regulates human rheumatoid synovial fibroblast (RSF) 85-kDa phospholipase A 2 (PLA 2 ) and mitogen-inducible cyclooxygenase (COX) II. Promoter regions for these genes contain a motif that closely resembles the "classic" NFB consensus site. Immunoblot analysis identified NFB1 (p50), RelA (p65), and c-Rel in RSF. Upon IL-1␤-stimulation, p65 and c-Rel but not p50 protein levels were reduced suggesting nuclear translocation. IL-1␤-induced RSF nuclear extracts contained a p65-containing complex, which bound to the classical NFB consensus motif. An NFB classical oligonucleotide decoy produced a concentration-dependent decrease in IL-1-stimulated PGE 2 production (IC 50 ‫؍‬ ϳ2 M), indicating a role of NFB. Utilization of antisense technology showed that p65 but not p50 or c-Rel mediated IL-1␤-stimulated PGE 2 formation. Treated RSF could not transcribe COX II or 85-kDa PLA 2 mRNA, which reduced their respective proteins. Interestingly, stimulated IL-8 production was not inhibited by the classical NFB decoy but was reduced by treatment with antisense to both p65 and c-Rel supporting preferential binding of c-Rel-p65 to the "alternative" IL-8 B motif. Taken together, these data provide the first direct evidence for a role of p65 in COX II and 85-kDa PLA 2 gene induction and support the IL-1 activation and participation of distinct NFB protein dimers in RSF prostanoid and IL-8 formation.Rheumatoid arthritis is an autoimmune disease characterized by chronic inflammation and hyperproliferation of the synovial lining (1). Enhanced levels of the cytokine, interleukin (IL)-1␤, 1 perpetuate the disease process through up-regulation of a multitude of factors leading to eicosanoid formation, matrix degradation, bone resorption, and proliferation in the joint (2-6). We and others have demonstrated that human rheumatoid synovial fibroblast (RSF) prostaglandin (PG) E 2 accumulation in response to IL-1␤ is a direct result of the coordinate up-regulation of 85-kDa phospholipase A 2 (PLA 2 ) and the induction of COX II (6 -8). Indeed, we reported that depletion of IL-1␤-induced 85-kDa PLA 2 to basal levels by antisense severely compromised the ability of RSF to make PGE 2 . However, the mechanism(s) by which IL-1␤ regulates 85-kDa PLA 2 and COX II gene induction in this system have not been elucidated.IL-1␤ is a potent activator of nuclear factor B (NFB) (1, 9, 10) in other cell systems, and this transcription factor in turn regulates a wide variety of inflammatory and immunoregulatory genes (10 -16). 5Ј-flanking regulatory regions for both the human 85-kDa PLA 2 and COX II genes have recently been isolated (17, 18), and sequence analysis has identified a number of possible transcription factor consensus binding motifs, including NFB. The putative NFB motif in the 85-kDa PLA 2 promoter is located at Ϫ1099 base pairs (17), whereas the NFB consensus site in the human COX II promoter is located at Ϫ233 base pairs (18).NFB is a dimeric DNA binding protein comprised of members of the NFB/Rel/dorsal family of protei...