Metabolites of the β-amyloid precursor protein generated by β-secretase localise to the trans-golgi network and late endosome in 293 cells

Deposition of β-amyloid occurs in the brains of all sufferers of Alzheimer's disease. β-amyloid is proteolytically derived from the β-amyloid precursor protein by as yet unidentified enzymes termed secretases. We have generated and characterised antisera to the carboxy-terminal domain and β-secretase cleavage site of the Alzheimer's amyloid precursor protein. The β-secretase cleavage event occurs at the extreme N-terminus of the β-amyloid peptide. Our antiserum to the N-terminus of the β-amyloid peptide (NTβ4) specifically recognises β-secretase cleaved species as opposed to intact βAPP. NTβ4 specifically immunoprecipitates a 13 kDa fragment of βAPP (p13) which is potentially amyloidogenic. We have used these anti-sera in confocal laser scanning immunofluorescence microscopy to localise the intracellular location of potentially amyloidogenic βAPP processing fragments such as p13. Using a number of marker antisera of known intracellular location, we have defined the major location of βAPP fragments possessing the Asp-1 N-terminus of β-amyloid as the trans-Golgi network or late endosome on the basis of colocalisation with a monoclonal antibody to the cation-independent mannose-6-phosphate receptor. The colocalisation was further investigated using brefeldin A which demonstrated that the p13 fragment and mannose-6-phosphate receptor are trafficked by alternative pathways from the trans-Golgi network. © 1996 Wiley-Liss, Inc.