Axonal amyloid precursor protein and its fragments undergo somatodendritic endocytosis and processing.
Deposition of potentially neurotoxic Aβ fragments derived from amyloid precursor protein (APP) at synapses may be a key contributor to Alzheimer's disease. However, the location(s) of proteolytic processing and subsequent secretion of APP fragments from highly compartmentalized, euploid neurons that express APP and processing enzymes at normal levels is not well understood. To probe the behavior of endogenous APP, particularly in human neurons, we developed a system using neurons differentiated from human embryonic stem cells, cultured in microfluidic devices, to enable direct biochemical measurements from axons. Using human or mouse neurons in these devices, we measured levels of Aβ, sAPPα, and sAPPβ secreted solely from axons. We found that a majority of the fragments secreted from axons were processed in the soma, and many were dependent on somatic endocytosis for axonal secretion. We also observed that APP and the β-site APP cleaving enzyme were, for the most part, not dependent on endocytosis for axonal entry. These data establish that axonal entry and secretion of APP and its proteolytic processing products traverse different pathways in the somatodendritic compartment before axonal entry.
Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093.
Emily D
ED
Niederst
Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093.
Sol M
SM
Reyna
Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093 lgoldstein@ucsd.edu.
Lawrence S B
LS
Goldstein
D053829:Amyloid Precursor Protein Secretases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001369:Axons / Q000378:metabolism*; D001570:Benzodiazepinones / Q000494:pharmacology; D002454:Cell Differentiation; D002460:Cell Line; D002478:Cells, Cultured; D003712:Dendrites / Q000378:metabolism*; D053595:Embryonic Stem Cells / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D006835:Hydrazones / Q000494:pharmacology; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D046210:Microfluidic Analytical Techniques; D018613:Microscopy, Confocal; D009842:Oligopeptides / Q000494:pharmacology; D010446:Peptide Fragments / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
C529132:2-(((3,5-difluorophenyl)acetyl)amino)-N-(1-methyl-2-oxo-5-phenyl-2,3-dihydro-1H-1,4-benzodiazepin-3-yl)propanamide; D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D001570:Benzodiazepinones; D006835:Hydrazones; D008164:Luminescent Proteins; C511794:N'-(3,4-dihydroxybenzylidene)-3-hydroxy-2-naphthahydrazide; C414614:OM99-2; D009842:Oligopeptides; D010446:Peptide Fragments; D053829:Amyloid Precursor Protein Secretases