Phospholipase A
2 (PLA
2)-activating protein (PLAA) is a novel signaling molecule that regulates the production of prostaglandins (PGE
2) and tumor necrosis factor (TNF)-
![greek small letter alpha greek small letter alpha](http://www.sciencedirect.com/scidirimg/entities/204e.gif)
. To characterize the function of native PLAA
in situ, we generated HeLa (Tet-off) cells overexpressing
plaa (
plaahigh) and control (
plaalow) cells, with the
plaa gene in opposite orientation in the latter construct. The
plaahigh cells produced significantly more PGE
2 and interleukin (IL)-6 compared to
plaalow cells in response to TNF-
![greek small letter alpha greek small letter alpha](http://www.sciencedirect.com/scidirimg/entities/204e.gif)
. There was an increased activation and/or expression of cytosolic PLA
2, cyclooxgenase-2, and NF-κB after induction of
plaahigh cells with TNF-
![greek small letter alpha greek small letter alpha](http://www.sciencedirect.com/scidirimg/entities/204e.gif)
compared to the respective
plaalow cells. Microarray analysis of
plaahigh cells followed by functional assays revealed increased production of proinflammatory cytokine IL-32 and a decrease in the production of annexin A4 and clusterin compared to
plaalow cells. We demonstrated the role of annexin A4 as an inhibitor of PLA
2 and showed that addition of exogeneous clusterin limited the production of PGE
2 from
plaahigh cells. To understand regulation of
plaa gene expression, we used a luciferase reporter system in HeLa cells and identified one stimulatory element, with Sp1 binding sites, and one inhibitory element, in exon 1 of the
plaa gene. By using
decoy DNA
oligonucleotides to Sp1 and competitive binding assays, we showed that Sp1 maintains basal expression of the
plaa gene and binds to the above-mentioned stimulatory element. We demonstrated for the first time that the induction of native PLAA by TNF-
![greek small letter alpha greek small letter alpha](http://www.sciencedirect.com/scidirimg/entities/204e.gif)
can perpetuate inflammation by enhancing activation of PLA
2 and NF-κB.