Amyloid Precursor Protein (APP) functions as a cell surface kinesin I membrane receptor, mediating the axonal transport of beta-secretase and presenilin 1. APP is important for neurite growth, neuronal adhesion and axonogenesis. Immature APP (N-glycosylated in the endoplasmic reticulum) moves to the Golgi complex where complete maturation occurs (O-glycosylated and sulfated). After alpha-secretase cleavage, soluble APP is released into the extracellular space and the C-terminal is internalized to endosomes and lysosomes. Some APP accumulates in secretory transport vesicles leaving the late Golgi compartment and returns to the cell surface. APP is expressed in the brain, kidney, heart and spleen of fetal tissues; it is induced during neuronal differentiation. In adult brain, highest expression of APP is found in the frontal lobe of the cortex and in the anterior perisylvian cortex-opercular gyri. Moderate expression in the cerebellar cortex, the posterior perisylvian cortex-opercular gyri and the temporal associated cortex. Defects in APP are a cause of autosomal dominant Alzheimer's disease (AD).