Figure 4.

Intracellular trafficking of APP. Nascent APP molecules (black bars) mature through the constitutive secretory pathway (1). Once APP reaches the cell surface, it is rapidly internalized (2) and subsequently trafficked through endocytic and recycling organelles to the TGN or the cell surface (3). A small fraction is also degraded in the lysosome. Nonamyloidogenic processing mainly occurs at the cell surface where α-secretases are present. Amyloidogenic processing involves transit through the endocytic organelles where APP encounters β- and γ-secretases.