Two domains within the first putative transmembrane domain of presenilin 1 differentially influence presenilinase and gamma-secretase activity.
Presenilins (PS) are thought to contain the active site for presenilinase endoproteolysis of PS and gamma-secretase cleavage of substrates. The structural requirements for PS incorporation into the gamma-secretase enzyme complex, complex stability and maturation, and appropriate presenilinase and gamma-secretase activity are poorly understood. We used rescue assays to identify sequences in transmembrane domain one (TM1) of PS1 required to support presenilinase and gamma-secretase activities. Swap mutations identified an N-terminal TM1 domain that is important for gamma-secretase activity only and a C-terminal TM1 domain that is essential for both presenilinase and gamma-secretase activities. Exchange of residues 95-98 of PS1 (sw95-98) completely abolishes both activities while the familial Alzheimer's disease mutation V96F significantly inhibits both activities. Reversion of residue 96 back to valine in the sw95-98 mutant rescues PS function, identifying V96 as the critical residue in this region. The TM1 mutants do not bind to an aspartyl protease transition state analog gamma-secretase inhibitor, indicating a conformational change induced by the mutations that abrogates catalytic activity. TM1 mutant PS1 molecules retain the ability to interact with gamma-secretase substrates and gamma-secretase complex members, although Nicastrin stability is decreased by the presence of these mutants. gamma-Secretase complexes that contain V96F mutant PS1 molecules display a partial loss of function for gamma-secretase that alters the ratio of amyloid-beta peptide species produced, leading to the amyloid-beta peptide aggregation that causes familial Alzheimer's disease.
Department of Psychiatry, Washington University School of Medicine, St Louis, Missouri 63110, USA.
A L
AL
Brunkan
M
M
Martinez
J
J
Wang
E S
ES
Walker
D
D
Beher
M S
MS
Shearman
A M
AM
Goate
D000595:Amino Acid Sequence; D053829:Amyloid Precursor Protein Secretases; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism*; D002478:Cells, Cultured; D004355:Drug Stability; D010450:Endopeptidases; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005347:Fibroblasts / Q000201:enzymology / Q000378:metabolism; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D053764:Presenilin-1; D017434:Protein Structure, Tertiary / Q000502:physiology
D008562:Membrane Glycoproteins; D008565:Membrane Proteins; C508853:PSEN1 protein, human; D053764:Presenilin-1; C413604:nicastrin protein; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C475285:presenilinase, human; C509280:BACE1 protein, human; C509282:Bace1 protein, mouse