A novel protein domain required for apoptosis. Mutational analysis of human Fas antigen

TLDR

The Fas antigen is a cell‑surface TNF receptor family protein that mediates apoptosis. The authors generated and expressed mutant Fas cDNAs with cytoplasmic deletions in L929 cells to probe functional domains. Antibody‑induced apoptosis of Fas‑expressing cells was enhanced by a 15‑amino‑acid C‑terminal deletion but lost with further removal, revealing an inhibitory and a 68‑amino‑acid signal‑transducing domain essential for apoptosis.

Abstract

The Fas antigen is a cell surface protein that can mediate apoptosis and that belongs to the tumor necrosis factor receptor family. Murine fibroblast L929 cells or T-cell lymphoma WR19L cells expressing the human Fas antigen were killed within 4-6 h by anti-human Fas antibody in a concentration-dependent manner. Human Fas antigen cDNAs with various mutations in the cytoplasmic region were constructed and expressed in L929 cells. A deletion of 15 amino acids from the C terminus of the Fas antigen enhanced the Fas antibody-induced killing activity, whereas a further deletion abolished its activity. This suggests the presence of an inhibitory as well as a signal-transducing domain in the cytoplasmic region of the Fas antigen. A 68-amino acid portion of the signal-transducing domain significantly conserved in the Fas antigen as well as in the type I tumor necrosis factor receptor was considered to be the novel protein domain required for apoptotic signal transduction.