Using β-Secretase Inhibitors to Distiguish the Generation of the Aβ Peptides Terminating at Val-40 and Ala-42

Area of Science:

• Neuroscience
• Biochemistry
• Genetics

Background:

• Alzheimer's disease (AD) pathogenesis is strongly linked to beta-amyloid (Aβ) accumulation.
• Aβ neurotoxicity is dependent on the formation of amyloid fibrils, characteristic of senile plaques.
• Autosomal dominant AD mutations in three genes alter amyloid precursor protein (APP) metabolism.

Purpose of the Study:

• To investigate the role of Aβ peptide length and mutations in APP metabolism on Aβ deposition in a mouse model.
• To explore the relationship between amyloidogenic properties of Aβ isoforms and senile plaque formation.

Main Methods:

• Transgenic expression of amyloid precursor protein (APP) in mice.
• Quantitative expression of wild-type APP versus APP with a mutation at codon 717 (known to increase Aβ42 formation).
• Age-dependent monitoring for Aβ deposition and senile plaque formation.

Main Results:

• Overexpression of wild-type APP (twofold) did not result in Aβ deposition.
• Transgenic mice expressing APP with the codon 717 mutation showed Aβ deposits by 18 months of age.
• These findings indicate that increased Aβ42 formation accelerates Aβ deposition.

Conclusions:

• The Aβ load in the brain is a critical factor in Alzheimer's disease pathology.
• The inherent amyloidogenic properties of specific Aβ isoforms, such as Aβ42, directly influence deposition and plaque formation.
• These results support the hypothesis that increased production of longer Aβ peptides drives aggressive, early-onset Alzheimer's disease.