May play a role in postsynaptic function. The C-terminal gamma-secretase processed fragment, ALID1, activates transcription activation through APBB1 (Fe65) binding (By similarity). Couples to JIP signal transduction through C-terminal binding. May interact with cellular G-protein signaling pathways. Can regulate neurite outgrowth through binding to components of the extracellular matrix such as heparin and collagen I. The gamma-CTF peptide, C30, is a potent enhancer of neuronal apoptosis. Monomer and homodimer. Heparin binding promotes homodimerization. Binds, via its C-terminus, to the PID domain of several cytoplasmic proteins, including APBB and APBA family members, MAPK8IP1 and DAB1 (By similarity). Binding to Dab1 inhibits its serine phosphorylation (By similarity). Interacts with CPEB1. Interacts (via NPXY motif) with DAB2 (via PID domain); the interaction is impaired by tyrosine phosphorylation of the NPXY motif. Interacts (via NPXY motif) with DAB1 (By similarity). C-terminally processed in the Golgi complex. Expressed in the cerebral cortex where it is localized to the postsynaptic density (PSD). The NPXY sequence motif found in many tyrosine-phosphorylated proteins is required for the specific binding of the PID domain. However, additional amino acids either N- or C-terminal to the NPXY motif are often required for complete interaction. The NPXY site is also involved in clathrin-mediated endocytosis. Proteolytically cleaved by caspases during neuronal apoptosis. Cleaved, in vitro, at Asp-620 by caspase-3 (By similarity). N- and O-glycosylated. O-glycosylation with core 1 or possibly core 8 glycans. Glycosylation on Ser-227 is the preferred site to Thr-228. Binds zinc and copper in the extracellular domain. Zinc-binding increases heparin binding. No Cu(2+) reducing activity with copper-binding. Belongs to the APP family.