Pulse-chase experiments revealed beta-secretase cleavage from immature full-length amyloid precursor protein harboring the Swedish mutation. Implications for distinct pathways.
The molecular mechanisms of the nonamyloidogenic and the amyloidogenic pathways of the amyloid precursor protein (APP) are unknown, but proteolysis of APP is essential for the generation of beta-amyloid. To study the time-course of C-terminal fragment generation by alpha- and beta-secretase, we expressed the APP751 isoform with the Swedish mutation in the human neuroblastoma cell line SY5Y as previously described (Urmoneit et al., 1995). We show in pulse-chase experiments that the C-terminal fragments, CT, generated by alpha-secretase and A4CT, generated by beta-secretase, could be generated from immature full-length APP before O-glycosylation is completed. Thus beta A4 may be generated from immature APP that has not passed through the trans-Golgi-network (TGN), which presents experimental evidence for the intracellular localization of beta-secretase activity in an earlier Golgi complex.
Urmoneit
B
B
University of Düsseldorf, Berlin, Germany.
Turner
J
J
Dyrks
T
T
D000544:Alzheimer Disease / Q000235:genetics / Q000378:metabolism; D053829:Amyloid Precursor Protein Secretases; D016564:Amyloid beta-Protein Precursor / Q000235:genetics* / Q000378:metabolism*; D016282:Aspartic Acid Endopeptidases; D020126:Brefeldin A / Q000494:pharmacology; D002451:Cell Compartmentation / Q000502:physiology; D010450:Endopeptidases / Q000235:genetics* / Q000378:metabolism*; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D007476:Ionophores / Q000494:pharmacology; D008715:Methionine / Q000378:metabolism / Q000494:pharmacology; D008985:Monensin / Q000494:pharmacology; D016296:Mutagenesis / Q000502:physiology; D009447:Neuroblastoma; D010446:Peptide Fragments / Q000378:metabolism; D010957:Plasmids; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D013462:Sulfur Radioisotopes; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000201:enzymology
D016564:Amyloid beta-Protein Precursor; D007476:Ionophores; D010446:Peptide Fragments; D011500:Protein Synthesis Inhibitors; D013462:Sulfur Radioisotopes; D020126:Brefeldin A; D008985:Monensin; D008715:Methionine; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human