Processing of the pre-beta-amyloid protein by cathepsin D is enhanced by a familial Alzheimer's disease mutation.
A major pre-beta-amyloid protein695 (APP695) processing activity from Alzheimer's disease brain extracts was identified and found to be indistinguishable from the activity of cathepsin D.APP695 processing activity cleaved APP695 into a series of fragments that reacted on immunoblots to a monoclonal antibody (C286.8a) against beta-amyloid-(1-7)-peptide and cleaved N-dansyl-APP-(591-601)-amide at the Glu-Val and Met-Asp bonds. Fragments of 5.5 kDa and 10-12 kDa were formed from the cleavage of APP695 by cathepsin D at the Glu593-Val594 bond, and had the same N-terminus as a minor form of beta-amyloid released by cells. The Lys595-->Asn and Met596-->Leu substitutions found in a pedigree of familial Alzheimer's disease, increased the cathepsin D-catalyzed rate of accumulation of 5.5 kDa and 10-12 kDa C286.8a-reactive fragments 5-10fold. This substitution also increased the rate of N-dansyl-APP-(591-601)-amide cleavage at the Xaa-Asp bond by up to 41-fold. These observations suggest a role of cathepsin D in beta-amyloid formation under certain circumstances.
Dreyer
R N
RN
Institute for Molecular Biologicals, Miles Inc., Pharmaceuticals Division, West Haven, Connecticut 06516.
Bausch
K M
KM
Fracasso
P
P
Hammond
L J
LJ
Wunderlich
D
D
Wirak
D O
DO
Davis
G
G
Brini
C M
CM
Buckholz
T M
TM
König
G
G
D000544:Alzheimer Disease / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D016564:Amyloid beta-Protein Precursor / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D000911:Antibodies, Monoclonal; D002402:Cathepsin D / Q000378:metabolism*; D002852:Chromatography, Ion Exchange; D003619:Dansyl Compounds; D004591:Electrophoresis, Polyacrylamide Gel; D000939:Epitopes / Q000032:analysis; D005625:Frontal Lobe / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000032:analysis / Q000737:chemistry / Q000302:isolation & purification; D017354:Point Mutation; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity
D016564:Amyloid beta-Protein Precursor; D000911:Antibodies, Monoclonal; D003619:Dansyl Compounds; D000939:Epitopes; D010446:Peptide Fragments; D011994:Recombinant Proteins; D002402:Cathepsin D