Metabolism of the "Swedish" amyloid precursor protein variant in Madin-Darby canine kidney cells.
The 4-kDa beta-amyloid peptide (A beta), a major constituent of parenchymal amyloid deposits in Alzheimer's disease, is derived from larger amyloid precursor proteins (APP). We have examined the metabolism of APP in Madin-Darby canine kidney cells stably transfected with cDNA encoding either wild-type human APP-695 or human APP-695 that harbors the Swedish double mutation associated with familial early-onset Alzheimer's disease. Although approximately 90% of total soluble APP secreted from wild-type cells is secreted basolaterally following cleavage at the alpha-secretase site, soluble derivatives cleaved near or at the amino terminus of A beta (presumably the "beta-secretase" site) are preferentially secreted into the apical compartment of SWE cells. Concomitantly, levels of a specific A beta-containing carboxyl-terminal fragment are elevated in SWE cell lysates. Using domain-specific biotinylation and release assays, we failed to detect a beta-secretase-generated soluble derivative (APPs beta) released from the surface of SWE cells. However, APPs beta can be detected in SWE cell lysates, consistent with "beta-secretase" cleavage occurring in an intracellular compartment. Finally, we demonstrate that A beta is secreted into the basolateral compartment of SWE cells and that the majority of these A beta-related species contains an amino-terminal aspartate residue (+1).
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Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205-2196.
Haass
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Wagner
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Teplow
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Sisodia
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D000595:Amino Acid Sequence; D053829:Amyloid Precursor Protein Secretases; D016564:Amyloid beta-Protein Precursor / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001224:Aspartic Acid / Q000737:chemistry; D016282:Aspartic Acid Endopeptidases; D001483:Base Sequence; D002478:Cells, Cultured; D004285:Dogs; D010450:Endopeptidases / Q000378:metabolism; D006868:Hydrolysis; D007668:Kidney / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation; D009838:Oligodeoxyribonucleotides; D013347:Subcellular Fractions / Q000201:enzymology
D016564:Amyloid beta-Protein Precursor; D009838:Oligodeoxyribonucleotides; D001224:Aspartic Acid; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human