title: Arf6 controls beta-amyloid production by regulating macropinocytosis of the Amyloid Precursor Protein to lysosomes.
abstract: Alzheimer's disease (AD) is characterized by the deposition of Beta-Amyloid (Aβ) peptides in the brain. Aβ peptides are generated by cleavage of the Amyloid Precursor Protein (APP) by the β - and γ - secretase enzymes. Although this process is tightly linked to the internalization of cell surface APP, the compartments responsible are not well defined. We have found that APP can be rapidly internalized from the cell surface to lysosomes, bypassing early and late endosomes. Here we show by confocal microscopy and electron microscopy that this pathway is mediated by macropinocytosis. APP internalization is enhanced by antibody binding/crosslinking of APP suggesting that APP may function as a receptor. Furthermore, a dominant negative mutant of Arf6 blocks direct transport of APP to lysosomes, but does not affect classical endocytosis to endosomes. Arf6 expression increases through the hippocampus with the development of Alzheimer's disease, being expressed mostly in the CA1 and CA2 regions in normal individuals but spreading through the CA3 and CA4 regions in individuals with pathologically diagnosed AD. Disruption of lysosomal transport of APP reduces both Aβ40 and Aβ42 production by more than 30 %. Our findings suggest that the lysosome is an important site for Aβ production and that altering APP trafficking represents a viable strategy to reduce Aβ production.
authors.affiliation: J. Allyn Taylor Centre for Cell Biology, Molecular Medicine Research Group, Robarts Research Institute, 1151 Richmond St, London, ON, N6A 5B8, Canada. weihao.tang@athenadiagnostics.com.|Department of Physiology and Pharmacology, Schulich School of Medicine, the University of Western Ontario, London, ON, N6A 5B7, Canada. weihao.tang@athenadiagnostics.com.
authors.forename: Weihao
authors.initials: W
authors.lastname: Tang
authors.affiliation: J. Allyn Taylor Centre for Cell Biology, Molecular Medicine Research Group, Robarts Research Institute, 1151 Richmond St, London, ON, N6A 5B8, Canada. joshuahktam@gmail.com.|Department of Physiology and Pharmacology, Schulich School of Medicine, the University of Western Ontario, London, ON, N6A 5B7, Canada. joshuahktam@gmail.com.
authors.forename: Joshua H K
authors.initials: JH
authors.lastname: Tam
authors.affiliation: J. Allyn Taylor Centre for Cell Biology, Molecular Medicine Research Group, Robarts Research Institute, 1151 Richmond St, London, ON, N6A 5B8, Canada. cseah@uwo.ca.
authors.forename: Claudia
authors.initials: C
authors.lastname: Seah
authors.affiliation: J. Allyn Taylor Centre for Cell Biology, Molecular Medicine Research Group, Robarts Research Institute, 1151 Richmond St, London, ON, N6A 5B8, Canada. jchiu54@uwo.ca.|Department of Physiology and Pharmacology, Schulich School of Medicine, the University of Western Ontario, London, ON, N6A 5B7, Canada. jchiu54@uwo.ca.
authors.forename: Justin
authors.initials: J
authors.lastname: Chiu
authors.affiliation: J. Allyn Taylor Centre for Cell Biology, Molecular Medicine Research Group, Robarts Research Institute, 1151 Richmond St, London, ON, N6A 5B8, Canada. Andrea.Tyrer@camh.ca.|Department of Physiology and Pharmacology, Schulich School of Medicine, the University of Western Ontario, London, ON, N6A 5B7, Canada. Andrea.Tyrer@camh.ca.
authors.forename: Andrea
authors.initials: A
authors.lastname: Tyrer
authors.affiliation: J. Allyn Taylor Centre for Cell Biology, Molecular Medicine Research Group, Robarts Research Institute, 1151 Richmond St, London, ON, N6A 5B8, Canada. scregan@robarts.ca.|Department of Physiology and Pharmacology, Schulich School of Medicine, the University of Western Ontario, London, ON, N6A 5B7, Canada. scregan@robarts.ca.
authors.forename: Sean P
authors.initials: SP
authors.lastname: Cregan
authors.affiliation: J. Allyn Taylor Centre for Cell Biology, Molecular Medicine Research Group, Robarts Research Institute, 1151 Richmond St, London, ON, N6A 5B8, Canada. smeakin@robarts.ca.|Department of Biochemistry, Schulich School of Medicine, the University of Western Ontario, London, ON, N6A 5B7, Canada. smeakin@robarts.ca.
authors.forename: Susan O
authors.initials: SO
authors.lastname: Meakin
authors.affiliation: J. Allyn Taylor Centre for Cell Biology, Molecular Medicine Research Group, Robarts Research Institute, 1151 Richmond St, London, ON, N6A 5B8, Canada. spasternak@robarts.ca.|Department of Clinical Neurological Sciences, Schulich School of Medicine, the University of Western Ontario, London, ON, N6A 5B7, Canada. spasternak@robarts.ca.|Department of Physiology and Pharmacology, Schulich School of Medicine, the University of Western Ontario, London, ON, N6A 5B7, Canada. spasternak@robarts.ca.
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Pasternak
mesh_terms: D020823:ADP-Ribosylation Factor 1 / Q000378:metabolism; D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D000429:Alcohol Oxidoreductases / Q000378:metabolism; D000544:Alzheimer Disease / Q000378:metabolism / Q000473:pathology; D016229:Amyloid beta-Peptides / Q000096:biosynthesis*; D000818:Animals; D002451:Cell Compartmentation; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D002470:Cell Survival; D003432:Cross-Linking Reagents / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D003911:Dextrans / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism / Q000648:ultrastructure; D055785:Gene Knockdown Techniques; D006624:Hippocampus / Q000378:metabolism; D006801:Humans; D052118:Lysosomal-Associated Membrane Protein 1 / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism* / Q000648:ultrastructure; D051379:Mice; D050505:Mutant Proteins / Q000378:metabolism; D010873:Pinocytosis; D021381:Protein Transport; D034741:RNA, Small Interfering / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
chemical_list: D000089982:ADP-Ribosylation Factor 6; D000199:Actins; D016229:Amyloid beta-Peptides; D003432:Cross-Linking Reagents; D004268:DNA-Binding Proteins; D003911:Dextrans; D052118:Lysosomal-Associated Membrane Protein 1; D050505:Mutant Proteins; D034741:RNA, Small Interfering; D000429:Alcohol Oxidoreductases; C096794:C-terminal binding protein; D020823:ADP-Ribosylation Factor 1; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human; C000715727:Arf6 protein, mouse; D020830:rac1 GTP-Binding Protein