Effects of ACE Mutations Associated with Alzheimer’s Disease on Blood ACE Phenotype

An analysis of 1300+ existing ACE mutations revealed that 400+ are damaging and led us to hy-pothesize that carriers of heterozygous loss-of-function (LoF) ACE mutations (which result in low ACE levels) could be at risk for the development of late-onset Alzheimer’s disease (AD) [Danilov, 2024]. Here we quantified blood ACE levels in EDTA-plasma from 41patients with 10 different heterozygous ACE mutations, as well as 33 controls, and estimated the effect of these mutations on ACE phenotype using a set of mAbs to ACE and two ACE substrates. We found that relatively frequent (~1%) AD-associated ACE mutations in the N domain of ACE, Y215C and G325R are truly damaging and, likely, transport-deficient, with ACE levels in plasma only ~50% of controls. Another AD-associated ACE mutation, R1250Q, in the cytoplasmic tail, did not cause a decrease in ACE and, likely, did not affect surface ACE expression. We have also developed a method to identify patients with anti-catalytic mutations in the N domain. These mutations may result in reduced degradation of amyloid beta peptide Aβ42, an important component for amyloid deposition. Consequently, these could pose a risk factor for the development of AD. Therefore, a systematic analysis of blood ACE levels in patients with all ACE mutations has potential to identify individuals at an increased risk of late-onset AD. These individuals may benefit from future preventive or therapeutic interventions involving a combination of chemical and pharmacological chaperones, as well as proteasome inhibitors, aiming to enhance ACE protein traffic. This approach has been previously demonstrated in a cell model of the transport-deficient ACE mutation, Q1069R [Danilov, 2010].