Transcriptional Regulation of Secreted Phospholipase A2 in Human HepG2 Cells, Rat Astrocytes and Rabbit Articular Chondrocytes
We studied the regulation of the release and transcriptional regulation of the secreted type II phospholipase A2 (PLA2) in rat astrocytes, rabbit articular chondrocytes and the human hepatoma cell line HepG2. The interleukins IL-1, IL-6, TNF« stimulate PLA release in these cell lines. Okadaic acid and TPA decrease the release of PLA,, by HepG2 cells which is contrary to the effect of forskolin. Synergisms between IL-1 and forskolin in rat astrocytes, IL-6 and forskolin in HepG2 cells were observed in the secretion of PLA2. The same synergisms were observed for transcriptional activity measured in CAT assays. Surprisingly IL-1 and TNF as well as okadaïc acid and TPA decrease the CAT activities induced in HepG2 cells. The transcription of the PLA2 gene in rabbit chondrocytes and rat astrocytes appears to be regulated by positive regulatory DNA elements located in the first hundred base pairs upstream to the first exon. In rabbit chondrocytes, the region [−326; −264] was found to be critical for the transcriptional activity. The regulation of the promoter in HepG2 cells seems to be more complex and results from the combination of several positive and negative regulatory elements located in the region which spans from positions −1614 to −87.
KeywordsHepG2 Cell Okadaic Acid PLA2 Activity cAMP Dibutyryl Human HepG2
Unable to display preview. Download preview PDF.
- 2.Sharp, J.D., White, D.L., Chiou, X.G., Goodson, T., Gamboa, G.C., McClure, D., Burgett, S., Hoskins, J., Skatrud, P.L., Sportsman, J.R., Becker, G.W., Kang, L.H., Roberts, E.F. and Kramer, R. Molecular cloning and expression of human Cat+-sensitive cytosolic phospholipase A?. J. Biol. Chem. 266 (1991) 14850–14853PubMedGoogle Scholar
- 3.Seilhamer, J.J., Pruzanski, W., Vadas, P., Plant, S., Miller, J.A., Kloss, J. and Johnson, L.K. Cloning and recombinant expression of phospholipase A2 present in rheumatoid arthritic synovial fluid. J. Biol. Chem. 266 (1989) 5335–5338.Google Scholar
- 7. Berenbaum, F., Thomas, G., Poiraudeau, S., Bereziat, G., Corvol, M.T. and Masliah, J. Insulin like growth factor inhibit arachidonic acid release and type II phospholipase A2 gene expression by interleukin-lß in articular rabbit chondrocytes. (1993) submitted to publicationGoogle Scholar
- 8.Schalkwijk, C., Pfeilschifter, J., Märki, F. and van den Bosch, H. Interleukin-lß-and forskolin-induced synthesis and secretion of group II phospholipase A, and prostaglandin E7 in rat mesangial cells is prevented by transforming growth factor-ß2. J. Biol. Chem. 267 (1992) 8846–8851PubMedGoogle Scholar
- Nakano, T., Ohara, O., Teraoka, H. and Arita, H. Group II phospholipase A2 mRNA synthesis is stimulated by two distinct mechanisms in rat vascular smooth muscle cells. FEBS Lett 261 (1990) 171–174.Google Scholar
- 32.Park, K., Chung, M. and Kim, S.J. Inhibition of myogenesis by okadaic acid, and inhibitor of protein phosphatases, 1 and 2A, correlates with the induction of AP1. J. Biol. Chem. 267 (1992) 10810–10815.Google Scholar