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P1‐158: Amyloidogenic metabolism of human APP in X11‐like deficient mice brain
Author(s) -
Kondo Maho,
Sakuma Megumi,
Saito Yuhki,
Nakaya Tadashi,
Maeda Masahiro,
Suzuki Toshiharu
Publication year - 2009
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.2009.04.164
Subject(s) - immunoprecipitation , amyloid precursor protein , genetically modified mouse , microbiology and biotechnology , metabolism , signal transducing adaptor protein , chemistry , human brain , biochemistry , phosphorylation , biology , transgene , gene , neuroscience , medicine , alzheimer's disease , disease
Background: X11-like (X11L), which is neuronal adaptor protein containing a phosphotyrosine binding (PTB) and two PDZ domains, interacts with the cytoplasmic GYENPTY motif of APP695 through its PTB domain and regulates APP metabolism (reviewed in J. Biol. Chem. [2008] 283, 29633). In brain hippocampus of X11L-KO mice, b-site cleavage of murine endogenous APP was facilitated and amounts of Ab increased (J. Biol. Chem. [2006] 281, 37853). Further analysis revealed that X11L can function to anchor mature APP outside of detergent-resistant membrane (DRM) where band g-secretases are rich in activity (J. Biol. Chem. [2008] 283, 35763). Our observations propose an idea that malfunction of X11L in the regulation of APP metabolism may facilitate amyloidogenic metabolism of APP in AD. But the effects of X11L deficiency on metabolism of human APP expressing at physiological level in mouse brain have not been revealed along with the regulatory mechanism of APP-X11L interaction. Here we tried to understand these issues. Methods: By crossing X11L-KO mice and transgenic mice expressing human APP at physiological level (APP-Tg), we newly generated APP-Tg/X11L-KO mice. APP C-terminal fragments (CTF) in APP-Tg and APP-Tg/X11L-KO mice brain were analyzed by immunoblotting. The levels of human Ab40 and Ab42 were measured by sELISA system. To identify the regulatory region of X11L in APP-X11L interaction, we prepared epitopetagged and GST-fused X11L proteins including various region deletions and amino acid mutations. The interaction of APP-X11L was examined by co-immunoprecipitation in cells and GST pull-down assay in vitro. Results: APP-Tg/X11L-KO mice showed significant increase of human APP CTFb and Ab compared to APP-Tg mice. We identified the region of X11L that regulates association with APP in outside of, and amino-terminal to, the PTB domain. Conclusions: X11L deficiency induces the amyloidgenic metabolism of human APP as does endogenous APP. This result supports the function of X11L which anchors APP outside of DRM and suppress the pathogenic metabolism of APP. Modification of the region that regulates APP association may induce a conformational change within PTB domain and alter APP-binding ability. Some qualitative change of X11L such as decreased association with APP may lead to onset sporadic AD.