PCSK2 and Alzheimer disease: Furthermore, an important subset of brain enzymes, including PCMT1, PCSK2, DPYSL2, and BLVRA, displayed a positive association with presymptomatic AD, as shown in Fig. 3b—IV, and significant dysregulation of the mitophagy and phagophore-associated protein GABARAP was also observed in this AD3-positively associated cluster (Fig. 3b—V).