FLASH is involved in Fas induced apoptosis. It is recruited to Fas after the receptor cross-linking. Overexpression of wild type of FLASH facilitates and its dominant negative form inhibits Fas induced apoptosis. FLASH interacts with the DEDs of caspase-8 and FADD through the DED-like domain of FLASH and mediates activation of caspase-8. There are parallels between FLASH and Apaf-1/CED-4 although there are arguments against their structural similarity.

Studies of FLASH protein suggested that this protein may be a component of the death inducing signaling complex that includes Fas receptor, Fas binding adapter FADD, and caspase 8, and plays a regulatory role in Fas mediated apoptosis.