Intracellular generation of amyloid beta-protein from amyloid beta-protein precursor fragment by direct cleavage with beta- and gamma-secretase.
Two amyloid beta protein precursor (beta APP) fragments involving Met and 103 amino acids of C-terminus of beta APP (delta NOR-beta) and its KM-NL substitution (delta NL-beta) were expressed in COS-7 cells to clarify the proteolytic cleavages to generate amyloid beta protein (A beta). The 4.5-kD protein, A beta with additional N-terminal amino acids, and 4-kD A beta were directly produced and released from 12.5-kD expression proteins without any production of 11.4-kD C-terminal fragment starting at N-terminus of A beta and 3-kD "p3" A beta derivative. Intracellular 4-kD A beta was also detected. The substitution of KM-NL of beta APP found in Swedish familial Alzheimer's disease (AD) promoted the production of intracellular A beta and its release with no increase in level of 11.4-kD C-terminal fragment. These results suggested the presence of a distinct pathway in which A beta is directly cleaved at both N- and C-termini from beta APP fragment intracellularly to release A beta. Since KM-NL substitution enhanced intracellular A beta generation, this pathway may be associated with amyloidogenesis in AD.
Iizuka
T
T
Department of Neurology, Gunma University School of Medicine, Japan.
Shoji
M
M
Kawarabayashi
T
T
Sato
M
M
Kobayashi
T
T
Tada
N
N
Kasai
K
K
Matsubara
E
E
Watanabe
M
M
Tomidokoro
Y
Y
Hirai
S
S
D000544:Alzheimer Disease / Q000235:genetics / Q000378:metabolism; D000643:Ammonium Chloride / Q000494:pharmacology; D053829:Amyloid Precursor Protein Secretases; D016229:Amyloid beta-Peptides / Q000096:biosynthesis*; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism*; D000818:Animals; D016282:Aspartic Acid Endopeptidases; D001483:Base Sequence; D002460:Cell Line; D002522:Chlorocebus aethiops; D017931:DNA Primers; D010450:Endopeptidases / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D007976:Leupeptins / Q000494:pharmacology; D008744:Methylamines / Q000494:pharmacology; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011480:Protease Inhibitors / Q000494:pharmacology; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D014162:Transfection
D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D017931:DNA Primers; D007976:Leupeptins; D008744:Methylamines; D010446:Peptide Fragments; D011480:Protease Inhibitors; D011994:Recombinant Proteins; D000643:Ammonium Chloride; C027451:methylamine; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human; C032854:leupeptin