The APP-processing pathway is a pathological component of Alzheimer's disease (AD), but there is no consensus regarding the physiological functions of APP and its products. Two studies (Nikolaev et al., 2009, Lauren et al., 2009) link the physiological and pathological aspects of APP processing. They show that the APP products, N-APP and Aβ42, are ligands for death receptor 6 and cellular prion protein, respectively, which are important in nervous system development and synaptic suppression.