The Amyloid Precursor Protein Copper Binding Domain Histidine Residues 149 and 151 Mediate APP Stability and Metabolism

One of the key pathological hallmarks of Alzheimer disease (AD) is the accumulation of the APP-derived amyloid beta peptide A beta) in the brain. Altered copper homeostasis has also been reported in AD patients and is thought to increase oxidative stress and to contribute to toxic A beta accumulation and regulate APP metabolism. The potential involvement of the N-terminal APP copper binding domain CuBD) in these events has not been investigated. Based on the tertiary structure of the APP CuBD, we examined the histidine residues of the copper binding site His(147), His(149), and His(151)). We report that histidines 149 and 151 are crucial for CuBD stability and APP metabolism. Co-mutation of the APP CuBD His(149) and His(151) to asparagine decreased APP proteolytic processing, impaired APP endoplasmic reticulum-to-Golgi trafficking, and promoted aberrant APP oligomerization in HEK293 cells. Expression of the triple H147N/H149N/H151N-APP mutant led to up-regulation of the unfolded protein response. Using recombinant protein encompassing the APP CuBD, we found that insertion of asparagines at positions 149 and 151 altered the secondary structure of the domain. This study identifies two APP CuBD residues that are crucial for APP metabolism and suggests an additional role of this domain in APP folding and stability besides its previously identified copper binding activity. These findings are of major significance for the design of novel AD therapeutic drugs targeting this APP domain.