Specific Mutations in Aph1 Cause γ-Secretase Activation

Area of Science:

• Neuroscience
• Biochemistry
• Molecular Biology

Background:

• Amyloid beta peptides (Aβs) are key in Alzheimer's disease pathogenesis.
• Gamma-secretase, involving presenilin 1 (PS1), cleaves amyloid precursor protein (APP).
• Familial Alzheimer's disease (FAD) mutations in PS1 alter γ-secretase activity.

Purpose of the Study:

• To identify activating mutations in Aph1, a γ-secretase regulatory subunit.
• To investigate the role of Aph1 in modulating γ-secretase cleavage activity.
• To understand the impact of Aph1 mutations on Aβ production.

Main Methods:

• Utilized a yeast γ-secretase assay to screen for Aph1 mutations.
• Analyzed identified Aph1 mutations in the presence of nicastrin (NCT).
• Assessed Aβ production in mouse embryonic fibroblasts expressing Aph1 mutants.

Main Results:

• Identified Aph1 mutations active in the absence of NCT.
• The Aph1 L30F/T164A mutation demonstrated activating effects on γ-secretase.
• Aph1 mutants increased production of both short and long Aβ species.
• The mutation enhanced cleavage activity without altering γ-secretase complex levels.

Conclusions:

• Aph1 plays a regulatory role in γ-secretase activity.
• Specific Aph1 mutations can enhance catalytic activity, increasing Aβ production.
• These findings provide novel insights into γ-secretase regulation and potential therapeutic targets for Alzheimer's disease.