APP and Alzheimer disease: In addition to its role in neuronal plasticity (reviewed in [11]), MT5-MMP has been shown to cleave the amyloid precursor protein (APP) [12,13], a key protein in AD, whose metabolism leads to the accumulation of the APP C-terminal fragment (CTF) (i.e., C99) and its immediate derivative, the amyloid beta peptide (Aβ) [13,14].