Metabolism of the "Swedish" amyloid precursor protein variant in neuro2a (N2a) cells. Evidence that cleavage at the "beta-secretase" site occurs in the golgi apparatus.
The 4-kDa beta-amyloid peptide (Abeta), a principal component of parenchymal amyloid deposits in Alzheimer's disease, is derived from amyloid precursor proteins (APP). To identify potential intracellular compartments involved in Abeta production, we expressed human APP-695 (APPwt) and APP-695 harboring the Swedish double mutation (APPswe) associated with familial early-onset Alzheimer's disease, in mouse N2a cells. We demonstrate that cells expressing APPswe secrete high levels of Abeta peptides and beta-secretase-generated soluble APP derivatives (APP s beta) relative to cells expressing APPwt. In addition, we observed a concomitant diminution in the levels of alpha-secretase-generated soluble APP derivatives (APP s alpha). Our interpretation of these findings is that beta-secretase cleavage occurs in an intracellular compartment and disables those substrates which would normally be cleaved by alpha-secretase. As anticipated, the levels of APPswe are diminished relative to the steady-state levels of surface-bound APPwt; moreover, surface-bound APPswe and APPwt molecules are released from the plasma membrane after cleavage by alpha-secretase, but not by beta-secretase. Finally, by examining the rate of appearance of specific APP metabolites generated by beta-secretase, we now unequivocally demonstrate that beta-secretase cleavage of APPswe occurs within the Golgi apparatus, as early as the medial compartment.
Thinakaran
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G
Department of Pathology, The John Hopkins University School of Medicine, Baltimore, Maryland 21205-2196, USA.
Teplow
D B
DB
Siman
R
R
Greenberg
B
B
Sisodia
S S
SS
D000544:Alzheimer Disease / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D053829:Amyloid Precursor Protein Secretases; D016229:Amyloid beta-Peptides / Q000096:biosynthesis*; D016564:Amyloid beta-Protein Precursor / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D000818:Animals; D016282:Aspartic Acid Endopeptidases; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D010450:Endopeptidases / Q000378:metabolism*; D014644:Genetic Variation; D006056:Golgi Apparatus / Q000201:enzymology*; D006801:Humans; D007700:Kinetics; D051379:Mice; D008959:Models, Neurological; D008969:Molecular Sequence Data; D009154:Mutation; D009447:Neuroblastoma; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured
D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D011994:Recombinant Proteins; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human; C509282:Bace1 protein, mouse