QC is intimately associated with the pathology and severity of AD by paralleling the generation of pE-Aβ in the brain (Figure 1) (Morawski et al., 2014), and the deposition of pE-Aβ was found to be restricted to APP/QC co-expression areas (Hartlage-Rübsamen et al., 2018). Here, APP is linked to Alzheimer disease.