Cloning and characterization of the bovine Fas

Fas (APO-1, CD95), a member of the tumor necrosis factor (TNF) receptor superfamily, is a cell membrane protein that mediates programmed cell death (apoptosis). In an effort to characterize the possible role of Fas-mediated apoptosis in some important physiological processes in livestock, bovine Fas (bFas) cDNA was isolated and its nucleotide sequence determined. The predicted amino acid sequence encodes a 323-amino-acid protein that contains a leader peptide, a transmembrane domain, and three domains of cysteine-rich motif within the extracellular region. At the amino acid level, bFas is 57% and 50% identical to human (hFas) and mouse (mFas), respectively. Its expression is abundant in peripheral blood lymphocytes, lung, spleen, thymus, and ovary, but minimal in heart, liver, and brain. A polyclonal anti-bFas serum raised against the carboxy-terminal half of cysteine-rich motif I recognized a single 46-kD protein in bovine MDBK cells by Western blot analysis. To investigate the apoptotic activity of bFas, MDBK and bFas-transfected L929 cells were exposed to a monoclonal anti-hFas IgM. Unlike other cell culture systems, the antibody failed to trigger cell death in MDBK and bFas transfected L929 cells.