CTSB and Alzheimer disease: Autophagy and mitophagy are impaired in AD as evidenced by reduced autophagy/mitophagy event (using electron microscopy techniques), low colocalization of the mitochondrial protein TOMM20 to the lysosomal protein LAMP2, and altered levels/activities of key autophagy/mitophagy proteins such as ULK1, AMPK, PICALM, BECN1, PI3P, AMBRA1, TBK1, BCL2L13, PINK1, BNIP3L/NIX, DISC1, BNIP3, PS1, CTSB (cathepsin B), and CTSD [6,12–15].