Role of endoplasmic reticulum, endosomal-lysosomal compartments, and microtubules in amyloid precursor protein metabolism of human neurons.
A wide interest in amyloid precursor protein (APP) metabolism stems from the fact that increased amounts of amyloid beta peptide (Abeta), arising through proteolytic processing of APP, likely play a significant role in Alzheimer's disease. As Alzheimer's disease pathology is limited almost exclusively to the human species, we established human primary neuron cultures to address the possibility of distinctive APP processing in human CNS neurons. In the present study, we investigate the role of organelles and protein trafficking in APP metabolism. Using brefeldin A, we failed to detect APP processing into Abeta in the endoplasmic reticulum. Monensin and the lysomotropic agents, NH4Cl and chloroquine, revealed a bypass pH-dependent secretory pathway in a compartment between the endoplasmic reticulum and the medial Golgi, resulting in the secretion of full-length APP. Colchicine treatment resulting in the loss of neurites inhibited processing of APP through the secretory, but not the endosomal-lysosomal, pathway of APP metabolism. The serine protease inhibitor, leupeptin, indicates a role for lysosomes in APP, Abeta, and APP C-terminal fragment turnover. These results demonstrate that the regulation of APP metabolism in human neurons differs considerably from those reported in rodent CNS primary neuron cultures or continuously dividing cell types.
LeBlanc
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AC
Department of Neurology and Neurosurgery, McGill University, and Bloomfield Center for Research in Aging, Lady Davis Institute for Medical Research, Mortimer B. Davis Jewish General Hospital, Montréal, Québec, Canada.
Goodyer
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CG
D000643:Ammonium Chloride / Q000494:pharmacology; D000682:Amyloid / Q000037:antagonists & inhibitors; D016229:Amyloid beta-Peptides / Q000378:metabolism; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism*; D002478:Cells, Cultured; D002738:Chloroquine / Q000494:pharmacology; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000502:physiology*; D011992:Endosomes / Q000502:physiology*; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D008247:Lysosomes / Q000502:physiology*; D008870:Microtubules / Q000502:physiology*; D009474:Neurons / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism; D011108:Polymers / Q000378:metabolism; D012016:Reference Values; D012697:Serine Endopeptidases / Q000378:metabolism
D000682:Amyloid; D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D011108:Polymers; D000643:Ammonium Chloride; D002738:Chloroquine; D010447:Peptide Hydrolases; D012697:Serine Endopeptidases; D003546:Cysteine Endopeptidases