Elevation of beta-amyloid peptide 2-42 in sporadic and familial Alzheimer's disease and its generation in PS1 knockout cells.
Urea-based beta-amyloid (Abeta) SDS-polyacrylamide gel electrophoresis and immunoblots were used to analyze the generation of Abeta peptides in conditioned medium from primary mouse neurons and a neuroglioma cell line, as well as in human cerebrospinal fluid. A comparable and highly conserved pattern of Abeta peptides, namely, 1-40/42 and carboxyl-terminal-truncated 1-37, 1-38, and 1-39, was found. Besides Abeta1-42, we also observed a consistent elevation of amino-terminal-truncated Abeta2-42 in a detergent-soluble pool in brains of subjects with Alzheimer's disease. Abeta2-42 was also specifically elevated in cerebrospinal fluid samples of Alzheimer's disease patients. To decipher the contribution of potential different gamma-secretases (presenilins (PSs)) in generating the amino-terminal- and carboxyl-terminal-truncated Abeta peptides, we overexpressed beta-amyloid precursor protein (APP)-trafficking mutants in PS1+/+ and PS1-/- neurons. As compared with APP-WT (primary neurons from control or PS1-deficient mice infected with Semliki Forest virus), PS1-/- neurons and PS1+/+ neurons overexpressing APP-Deltact (a slow-internalizing mutant) show a decrease of all secreted Abeta peptide species, as expected, because this mutant is processed mainly by alpha-secretase. This drop is even more pronounced for the APP-KK construct (APP mutant carrying an endoplasmic reticulum retention motif). Surprisingly, Abeta2-42 is significantly less affected in PS1-/- neurons and in neurons transfected with the endocytosis-deficient APP-Deltact construct. Our data confirm that PS1 is closely involved in the production of Abeta1-40/42 and the carboxyl-terminal-truncated Abeta1-37, Abeta1-38, and Abeta1-39, but the amino-terminal-truncated and carboxyl-terminal-elongated Abeta2-42 seems to be less affected by PS1 deficiency. Moreover, our results indicate that the latter Abeta peptide species could be generated by a beta(Asp/Ala)-secretase activity.
Wiltfang
J
J
Department of Psychiatry, Molecular Neurobiology, and Department of Biochemistry II, University of Göttingen, D-37073 Göttingen, Germany. jwiltfa@gwdg.de
Esselmann
H
H
Cupers
P
P
Neumann
M
M
Kretzschmar
H
H
Beyermann
M
M
Schleuder
D
D
Jahn
H
H
Rüther
E
E
Kornhuber
J
J
Annaert
W
W
De Strooper
B
B
Saftig
P
P
D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000134:cerebrospinal fluid / Q000378:metabolism*; D000595:Amino Acid Sequence; D053829:Amyloid Precursor Protein Secretases; D016229:Amyloid beta-Peptides / Q000096:biosynthesis* / Q000134:cerebrospinal fluid* / Q000737:chemistry*; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism; D001921:Brain / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D051379:Mice; D018345:Mice, Knockout; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation; D009474:Neurons / Q000378:metabolism; D010446:Peptide Fragments / Q000096:biosynthesis* / Q000134:cerebrospinal fluid* / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012672:Semliki forest virus / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D016229:Amyloid beta-Peptides; D018076:DNA, Complementary; D010446:Peptide Fragments; D010455:Peptides; C075222:amyloid beta-protein (1-42); C442220:amyloid beta-protein (2-42); D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human; C509282:Bace1 protein, mouse