The amyloid precursor protein forms plasmalemmal clusters via its pathogenic amyloid-β domain.

The amyloid precursor protein (APP) is a large, ubiquitous integral membrane protein with a small amyloid-β (Aβ) domain. In the human brain, endosomal processing of APP produces neurotoxic Aβ-peptides, which are involved in Alzheimer's disease. Here, we show that the Aβ sequence exerts a physiological function when still present in the unprocessed APP molecule. From the extracellular site, Aβ concentrates APP molecules into plasmalemmal membrane protein clusters. Moreover, Aβ stabilization of clusters is a prerequisite for their targeting to endocytic clathrin structures. Therefore, we conclude that the Aβ domain directly mediates a central step in APP trafficking, driving its own conversion into neurotoxic peptides.