title: Visualizing APP and BACE-1 approximation in neurons yields insight into the amyloidogenic pathway.
abstract: Cleavage of amyloid precursor protein (APP) by BACE-1 (β-site APP cleaving enzyme-1) is the rate-limiting step in amyloid-β (Aβ) production and a neuropathologic hallmark of Alzheimer's disease; thus, physical approximation of this substrate-enzyme pair is a crucial event with broad biological and therapeutic implications. Despite much research, neuronal locales of APP and BACE-1 convergence and APP cleavage remain unclear. Here we report an optical assay, based on fluorescence complementation, for visualizing in cellulo APP-BACE-1 interactions as a simple on/off signal. Combining this with other assays tracking the fate of internalized APP in hippocampal neurons, we found that APP and BACE-1 interacted in both biosynthetic and endocytic compartments, particularly along recycling microdomains such as dendritic spines and presynaptic boutons. In axons, APP and BACE-1 were cotransported, and they also interacted during transit. Finally, our assay revealed that the Alzheimer's disease-protective 'Icelandic' mutation greatly attenuates APP-BACE-1 interactions, suggesting a mechanistic basis for protection. Collectively, the data challenge canonical models and provide concrete insights into long-standing controversies in the field.
authors.affiliation: Department of Pathology, University of California, San Diego, La Jolla, California, USA.|Department of Neurosciences, University of California, San Diego, La Jolla, California, USA.
authors.forename: Utpal
authors.initials: U
authors.lastname: Das
authors.affiliation: Department of Pathology, University of California, San Diego, La Jolla, California, USA.|Department of Neurosciences, University of California, San Diego, La Jolla, California, USA.
authors.forename: Lina
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Pathology, University of California, San Diego, La Jolla, California, USA.|Department of Neurosciences, University of California, San Diego, La Jolla, California, USA.
authors.forename: Archan
authors.initials: A
authors.lastname: Ganguly
authors.affiliation: Department of Neurosciences, University of California, San Diego, La Jolla, California, USA.
authors.forename: Junmi M
authors.initials: JM
authors.lastname: Saikia
authors.affiliation: Department of Neurosciences, University of California, San Diego, La Jolla, California, USA.
authors.forename: Steven L
authors.initials: SL
authors.lastname: Wagner
authors.affiliation: Department of Neurosciences, University of California, San Diego, La Jolla, California, USA.|Department of Medicine and Physiology, National University of Singapore, Yong Loo Lin School of Medicine, Singapore.
authors.forename: Edward H
authors.initials: EH
authors.lastname: Koo
authors.affiliation: Department of Pathology, University of California, San Diego, La Jolla, California, USA.|Department of Neurosciences, University of California, San Diego, La Jolla, California, USA.
authors.forename: Subhojit
authors.initials: S
authors.lastname: Roy
mesh_terms: D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000378:metabolism; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism*; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism*; D001369:Axons / Q000378:metabolism; D002478:Cells, Cultured; D049229:Dendritic Spines / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D006624:Hippocampus / Q000378:metabolism*; D053858:Metabolic Networks and Pathways / Q000502:physiology*; D051379:Mice; D009474:Neurons / Q000378:metabolism*; D061848:Optical Imaging; D017729:Presynaptic Terminals / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D053829:Amyloid Precursor Protein Secretases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human