APP and Alzheimer disease: This interaction may therefore be relevant in AD, because SorL1 interacts with amyloid precursor protein (APP) to regulate its processing via the endosome-to-Golgi pathway, and loss of SorL1 or loss of retromer function can increase amyloidogenic processing of APP to the AD-causing Aβ form (reviewed in Fjorback and Andersen, 2012; Small, 2008; Willnow and Andersen, 2013).