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. Interacts with FAS/TNFRSF6 and BAX. Brain. Highly expressed in cerebellum, also found in cortex, olfactory bulb, and hippocampus. Mice show reduced cerebellar size and internal granular layer (IGL) thickness in early developmental stages, delayed Purkinje Cell (PC) development, with an abnormal morphology and reduced cellular density, increased caspase-8 and caspase-3 activity in PCs and higher sensitivity to Fas-mediated apoptosis. Belongs to the BI1 family. LFG subfamily. Extended N-terminus.