FUNCTIONAL REQUIREMENT OF THE 2 TNF RECEPTORS FOR INDUCTION OF APOPTOSIS IN PC60 CELLS AND THE ROLE OF MITOCHONDRIA IN TNF-INDUCED CYTOTOXICITY

The rat/mouse T-cell hybridoma PC60 was transfected either with hTNF-R 55 cDNA, hTNF-R75 cDNA, or both. Receptor-specific stimulation was ach ieved using agonistic monoclonal antibodies or receptor-specific mutei ns of hTNF. Either hTNF-R55 or hTNF-R75 could mediate the activation o f NF-kappa B and the induction of GM-CSF, IL-6, and IFN-gamma. But onl y in cells carrying both hTNF-R55 and hTNF-R75, was TNF able to induce apoptosis. This apoptosis could be inhibited almost completely by cot ransfection with human bcl-2 cDNA. Functional cooperation was observed between liganded and unliganded receptors for the induction of apopto sis. in vitro protein kinase activity was detected only in TNF-R75 imm unoprecipitates from cells in which the receptor was signaling. Direct evidence was obtained for reactive oxygen intermediates of mitochondr ial origin responsible for TNF-induced cytotoxicity in L929 cells. (C) 1995 Wiley-Liss, Inc.