FIGURE 2.

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