Molecular characterization of a CD95 signaling mutant

Objective. To study the intracellular signaling events associated with ligation of the surface receptor CD95. Methods. A mutant clone of Jurkat T cells, DD3, which fails to transmit apoptotic signals through CD95, was selected for study. Surface expression of CD95 and the primary nucleotide sequence of CD95, as well as the functional effects of a mutant CD95 molecule found in DD3, were examined. Results. DD3, while exhibiting impaired ability to undergo apoptosis after CD95 ligation, retained the ability to die after ultraviolet light stimulation. A CD95 complementary DNA (cDNA) cloned from DD3 encoded a mutant transmembrane protein lacking the carboxyterminal 'death domain.' Western blotting confirmed the presence of both wild-type and mutant CD95 protein in DD3. Transfection of the mutant CD95 cDNA into parental Jurkat cells conferred protection from CD95-mediated apoptosis. Conclusion. A mutant CD95 receptor lacking the cytoplasmic 'death domain' can interfere with wild-type receptor function in T cells.