title: Resistance to killing by tumor necrosis factor in an adipocyte cell line caused by a defect in arachidonic acid biosynthesis.
abstract: We have found that TA1-R6, which are resistant to the cytotoxic effects of tumor necrosis factor (TNF) in the presence of cycloheximide (Reid, T. R., Torti, F., and Ringold, G. M. (1989) J. Biol. Chem. 264, 4583-4589), have reduced ability to release arachidonic acid (20:4) from membrane phospholipids in response to either TNF or the calcium ionophore A23187 treatment. However, no defect in the activity of phospholipase A2, the principal enzyme responsible for the release of 20:4 from phospholipids, was observed in these cells. Detailed biochemical characterization of these TNF-resistant cells has revealed that these cells are unable to synthesize 20:4 endogenously because of a defect in delta 6-desaturase, the rate-limiting enzyme of 20:4 biosynthesis. This deficiency leads to a marked decrease in the steady-state levels of 20:4 present in choline-containing phospholipid (PC) and ethanolamine-containing phospholipid (PE). The TA1-R6 cells, however, are capable of incorporating exogenous 20:4 into PC and PE, and when loaded in such manner they become significantly more sensitive to the cytotoxic effects of TNF in the presence of cycloheximide. Therefore, the release of arachidonic acid from phospholipids appears to be a critical element in the signaling pathway utilized by TNF and is essential to the rapid cytotoxic response elicited by TNF in the absence of protein synthesis in wild-type TA1 cells.
authors.affiliation: Institute of Cancer and Developmental Biology, Syntex Research, Palo Alto, California 94304.
authors.forename: T
authors.initials: T
authors.lastname: Reid
authors.forename: C S
authors.initials: CS
authors.lastname: Ramesha
authors.forename: G M
authors.initials: GM
authors.lastname: Ringold
mesh_terms: D000273:Adipose Tissue / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000096:biosynthesis*; D000001:Calcimycin / Q000494:pharmacology; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D003513:Cycloheximide / Q000494:pharmacology; D004351:Drug Resistance; D044943:Fatty Acid Desaturases / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D007700:Kinetics; D050602:Linoleoyl-CoA Desaturase; D010743:Phospholipids / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D001095:Arachidonic Acids; D005227:Fatty Acids; D010743:Phospholipids; D014409:Tumor Necrosis Factor-alpha; D016718:Arachidonic Acid; D000001:Calcimycin; D003513:Cycloheximide; D044943:Fatty Acid Desaturases; D050602:Linoleoyl-CoA Desaturase