The influence of endoproteolytic processing of familial Alzheimer's disease presenilin 2 on abeta42 amyloid peptide formation.
Mutant presenilins (PS) contribute to the pathogenesis of familial Alzheimer's disease (FAD) by enhancing the production of Abeta42 from beta-amyloid precursor protein. Presenilins are endoproteolytically processed to N-terminal and C-terminal fragments, which together form a stable 1:1 complex. We have mapped the cleavage site in the PS2 protein by direct sequencing of its C-terminal fragment isolated from mouse liver. Three different N-terminal residues were identified starting at Val-299, Thr-301, and Leu-307 that correspond closely to the previously described N termini of the C-terminal fragment of human PS1. Mutational analysis of the PS2 cleavage site indicates that the principal endoproteolytic cleavage occurs at residues Met-298/Val-299 and that the N terminus is subsequently modified by secondary proteolytic cleavages. We have generated cleavage defective PS2 constructs, which accumulate exclusively as full-length polypeptides in transfected Neuro2a cells. Functional analysis of such cleavage defective PS2 carrying the FAD mutation Asn-141 --> Ile showed that its Abeta42 producing activity was strongly reduced compared with cleavage-competent FAD PS2. In contrast, cleavage defective PS2 was active in rescuing the egg-laying defect of a sel-12 mutant in Caenorhabditis elegans. We conclude that PS2 endoproteolytic cleavage is not an absolute requirement for its activities but may rather selectively enhance or stabilize its functions.
Jacobsen
H
H
Pharma Division, Preclinical Central Nervous System Research, CH-4070 Basel, Switzerland. helmut.jacobsen@roche.com
Reinhardt
D
D
Brockhaus
M
M
Bur
D
D
Kocyba
C
C
Kurt
H
H
Grim
M G
MG
Baumeister
R
R
Loetscher
H
H
D000544:Alzheimer Disease / Q000378:metabolism*; D000595:Amino Acid Sequence; D016229:Amyloid beta-Peptides / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans; D002478:Cells, Cultured; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism*; D011233:Precipitin Tests; D053766:Presenilin-2; D011401:Promoter Regions, Genetic; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D014162:Transfection
D016229:Amyloid beta-Peptides; D008565:Membrane Proteins; C508861:PSEN2 protein, human; D010446:Peptide Fragments; D053766:Presenilin-2; C075222:amyloid beta-protein (1-42)