title: The location and trafficking routes of the neuronal retromer and its role in amyloid precursor protein transport.
abstract: The retromer complex plays an important role in intracellular transport, is highly expressed in the hippocampus, and has been implicated in the trafficking of the amyloid precursor protein (APP). Nevertheless, the trafficking routes of the neuronal retromer and the role it plays in APP transport in neuronal processes remain unknown. Here we use hippocampal neuronal cultures to address these issues. Using fluorescence microscopy, we find that Vps35, the core element of the retromer complex, is in dendrites and axons, is enriched in endosomes and trans-Golgi network, and is found in APP-positive vesicles. Next, to identify the role the neuronal retromer plays in cargo transport, we infected hippocampal neurons with a lentivirus expressing shRNA to silence Vps35. By live fluorescence imaging, Vps35 deficiency was found to reduce the frequency, but not the kinetics, of long-range APP transport within neuronal processes. Supporting the interpretation that retromer promotes long-range transport, Vps35 deficiency led to increased APP in the early endosomes, in processes but not the soma. Finally, Vps35 deficiency was associated with increased levels of Aβ, a cleaved product of APP, increased colocalization of APP with its cleaving enzyme BACE1 in processes, and caused an enlargement of early endosomes. Taken together, our studies clarify the function of the neuronal retromer, and suggest specific mechanisms for how retromer dysfunction observed in Alzheimer's disease affects APP transport and processing.
authors.affiliation: The Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Department of Neurology, Columbia University College of Physicians and Surgeons, New York NY10032, USA.
authors.forename: Akhil
authors.initials: A
authors.lastname: Bhalla
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Vetanovetz
authors.forename: Etienne
authors.initials: E
authors.lastname: Morel
authors.forename: Zeina
authors.initials: Z
authors.lastname: Chamoun
authors.forename: Gilbert
authors.initials: G
authors.lastname: Di Paolo
authors.forename: Scott A
authors.initials: SA
authors.lastname: Small
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism*; D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000378:metabolism; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism*; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism; D002478:Cells, Cultured; D011992:Endosomes / Q000378:metabolism*; D006624:Hippocampus / Q000378:metabolism; D006801:Humans; D009474:Neurons / Q000378:metabolism*; D021381:Protein Transport; D033921:Vesicular Transport Proteins / Q000378:metabolism*; D021601:trans-Golgi Network / Q000378:metabolism*
chemical_list: D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; C419573:VPS35 protein, human; D033921:Vesicular Transport Proteins; D053829:Amyloid Precursor Protein Secretases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human