Hw. Klafki et al., THE CARBOXYL TERMINI OF BETA-AMYLOID PEPTIDE-1-40 AND PEPTIDE-1-42 ARE GENERATED BY DISTINCT GAMMA-SECRETASE ACTIVITIES, The Journal of biological chemistry, 271(45), 1996, pp. 28655-28659
We have studied the effects of peptide aldehyde protease inhibitors on
the secretion of beta-amyloid peptide 1-40 (A beta(1-40)) and A beta(
1-42) by HEK 293 and COS-1 cells expressing beta-amyloid precursor pro
tein with the Swedish double mutation. A multiphasic SDS-polyacrylamid
e gel electrophoresis system was used for the discrimination of A beta
(1-40) and A beta(1-42). Calpain inhibitor I, carbobenzoxyl-Leu-Leu-le
ucinal, and calpeptin were found to reduce the amount of A beta(1-40)
released into the medium in a dose-dependent manner. The reduction of
A beta(1-40) after treatment with 50 mu M calpain inhibitor I or 5 mu
M carbobenzoxyl-Leu-Leu-leucinal was accompanied by a slight increase
of A beta(1-42) released into the medium. These observations suggest t
hat the cleavages at residues 40 and 42 are accomplished by different
enzyme activities.