Journal: Nat Commun / Year: 2024 Title: Apo and Aβ46-bound γ-secretase structures provide insights into amyloid-β processing by the APH-1B isoform. Authors: Ivica Odorčić / Mohamed Belal Hamed / Sam Lismont / Lucía Chávez-Gutiérrez / Rouslan G Efremov / Abstract: Deposition of amyloid-β (Aβ) peptides in the brain is a hallmark of Alzheimer's disease. Aβs are generated through sequential proteolysis of the amyloid precursor protein by the γ-secretase ...Deposition of amyloid-β (Aβ) peptides in the brain is a hallmark of Alzheimer's disease. Aβs are generated through sequential proteolysis of the amyloid precursor protein by the γ-secretase complexes (GSECs). Aβ peptide length, modulated by the Presenilin (PSEN) and APH-1 subunits of GSEC, is critical for Alzheimer's pathogenesis. Despite high relevance, mechanistic understanding of the proteolysis of Aβ, and its modulation by APH-1, remain incomplete. Here, we report cryo-EM structures of human GSEC (PSEN1/APH-1B) reconstituted into lipid nanodiscs in apo form and in complex with the intermediate Aβ46 substrate without cross-linking. We find that three non-conserved and structurally divergent APH-1 regions establish contacts with PSEN1, and that substrate-binding induces concerted rearrangements in one of the identified PSEN1/APH-1 interfaces, providing structural basis for APH-1 allosteric-like effects. In addition, the GSEC-Aβ46 structure reveals an interaction between Aβ46 and loop 1, and identifies three other H-bonding interactions that, according to functional validation, are required for substrate recognition and efficient sequential catalysis.
Model: Quantifoil R0.6/1 / Material: COPPER / Mesh: 300 / Support film - #0 - Film type ID: 1 / Support film - #0 - Material: CARBON / Support film - #0 - topology: HOLEY / Support film - #1 - Film type ID: 2 / Support film - #1 - Material: GRAPHENE OXIDE / Support film - #1 - topology: CONTINUOUS
Energy filter - Name: In-column Omega Filter / Energy filter - Slit width: 20 eV
Image recording
Film or detector model: GATAN K3 (6k x 4k) / Digitization - Dimensions - Width: 5760 pixel / Digitization - Dimensions - Height: 4092 pixel / Number grids imaged: 1 / Number real images: 10733 / Average exposure time: 3.0 sec. / Average electron dose: 61.0 e/Å2
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
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