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S4‐01–02: Structure of the catalytic pore of gamma‐secretase
Author(s) -
Iwatsubo Takeshi
Publication year - 2008
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.2008.05.473
Subject(s) - presenilin , chemistry , transmembrane domain , nicastrin , biochemistry , gamma secretase , amyloid precursor protein secretase , transmembrane protein , mutant , ectodomain , proteolysis , membrane protein , membrane , microbiology and biotechnology , amyloid precursor protein , enzyme , biology , alzheimer's disease , gene , medicine , receptor , disease , pathology
A resolution revealed a 10 nm globular particle with an electron-lucent internal cavity and 2 apparent pore-like openings on the luminal and cytoplasmic surfaces. We have subsequently obtained a 3D structure at 12 A resolution by cryo-EM and single particle image reconstruction. The structure reveals multiple low-density areas and a potential lateral gate in the TM region as well as a sizable extracellular density above the putative gate that could serve as a substrate receptor. Images of the 12A structure will be shown. As gamma-secretase is active within membranes, lipid composition is likely to regulate activity. We modified a conventional gamma-activity assay to include a detergent-removal step that facilitates proteoliposome formation, increasing baseline cleavage activity 2-fold. Proteoliposomes containing cerebrosides or gangliosides significantly increased gamma-activity over a phosphatidylcholine-only baseline, whereas addition of phosphatidylinositol decreased activity. Addition of soluble cholesterol in the presence of phospholipids differentially increased the cleavage of APP-, APLP1and Notch-like substrates in a dose-dependent manner. Reconstitution of gamma-secretase in complex lipid mixtures revealed that a lipid raft-like composition supported the highest level of activity compared to other membrane compositions. Conclusions: We conclude that membrane lipid composition is a direct and potent regulator of gamma-secretase, and cholesterol plays a particularly important role.