We showed that AD cell and animal models display an increase of C99 at MAM (Pera et al, 2017) that results in the upregulation of MAM activities (Area‐Gomez et al, 2012; Hedskog et al, 2013), including SMases and cholesterol esterification by ACAT1 (Pera et al, 2017), a known MAM‐localized enzyme (Chang et al, 2009). The gene discussed is ACAT1; the disease is Alzheimer disease.