Antiapoptotic protein which protects cells uniquely from Fas-induced apoptosis. Regulates Fas-mediated apoptosis in neurons by interfering with caspase-8 activation. Plays a role in cerebellar development by affecting cerebellar size, internal granular layer (IGL) thickness, and Purkinje cell (PC) development (By similarity). Interacts with FAS/TNFRSF6 and BAX. Belongs to the BI1 family. LFG subfamily.