FLIP as a switch molecule that diverts Fas signals from cell death to proliferation. FLIP is homologous to caspase-8 in containing two DEDs that can interact with the DED of FADD, but its caspase domain is nonfunctional. FLIP physically associates with Raf-1 and TRAF1 and TRAF2, which connect, respectively, with the ERK and NF-κB pathways involved in cell proliferation or differentiation. In this capacity, primary cells that express high levels of FLIP would not only be resistant to Fas-induced death but might also receive a proliferative signal.