Arachidonic acid-selective cytosolic phospholipase A2 is crucial in the cytotoxic action of tumor necrosis factor.

The role of phospholipase A2 (PLA2) in the cytotoxic action of tumor necrosis factor (TNF) was examined. Recently, we described the characterization of TNF-resistant sublines isolated from TNF-sensitive cell line L929 (Hayakawa, M., Oku, N., Takagi, T., Hori, T., Shibamoto, S., Yamanaka, Y., Takeuchi, K., Tsujimoto, M., and Ito, F. (1991) Cell Struct. Funct. 16, 333-340). The most remarkable features of these TNF-resistant sublines were the defects in TNF-stimulated arachidonate metabolism. In this study, we characterized the PLA2 activities of these sublines and found a significant decrease in the activity in one of the TNF-resistant sublines, C12 cells. The enzymological features, such as Ca2+ requirement and substrate specificity, suggested that the high molecular weight arachidonoyl-selective cytosolic PLA2 (cPLA2) was involved in the TNF action. Northern hybridization analysis demonstrated the reduced expression of high molecular weight cPLA2 in C12 cells. Furthermore, expression of a cloned cPLA2 cDNA in C12 cells increased the sensitivity of cells to the TNF cytotoxicity. These results indicate the crucial role of the high molecular weight cPLA2 in the TNF-induced cytolysis.