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P3–398: Cysteine scanning mutagenesis as a tool for structure–function analysis of presenilin 1
Author(s) -
Tolia Alexandra,
Polic Dragana,
Annaert Willem,
De Strooper Bart
Publication year - 2006
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2006.05.1668
Subject(s) - presenilin , transmembrane domain , transmembrane protein , cysteine , chemistry , amyloid precursor protein , biochemistry , mutagenesis , biophysics , biology , amino acid , mutant , alzheimer's disease , enzyme , medicine , disease , gene , receptor , pathology
the active site domain located in its catalytic subunit presenilin (PS), where an additional substrate binding site has been proposed. Objective: To identify sequence determinants in the PS active site domain possibly involved in -secretase substrate identification. To further characterize the PS active site domain, in particular the role of the conserved GxGD protease active site motif. Methods: Mutants of the PS active site domain were generated. The constructs were assessed for -secretase activity towards APP and Notch substrates in embryonic fibroblast cells derived from PS1/2-/knockout mice cells or in HEK293 cells. In addition, the mutants were tested for their rescuing activity of a Notch-signaling deficient C. elegans sel-12 mutant. Results and Conclusions: When the active site domain of PS1 located in transmembrane domains 6 and 7 was exchanged with that of the C. elegans sperm protein SPE-4, the most distant PS homologue, the chimeric protein, PS1/SPE-46/7, supported APP but not Notch processing. In addition, PS1/SPE-46/7 was strongly impaired in C. elegans Notch signaling in vivo. Mapping experiments identified a single amino acid at position (amino acid 383 in PS1) of the GxGD active site motif in transmembrane domain 7 of PS to be responsible for the observed defect in Notch processing and signaling. Our data thus implicate a role of the PS active site domain in APP/Notch substrate selectivity of -secretase. We have also generated mutants of G382 of PS1 to further assess the functional role of the GxGD motif. The progress on these studies will be presented.