BIO254:Amyloid

Introduction

Alzheimer’s Disease (AD) is a neurodegenerative disorder symptomatically characterized by progressive cognitive degeneration and eventual deterioration in diverse aspects of daily life, including motor skills, behavior, and personality. One of the primary pathological features that characterizes Alzheimer’s disease is the deposition of extracellular ß-amyloid plaques in the brain. These extracellular plaques contain many components such as axon terminals, microglia, astrocytes, and aluminum. The major constituents of the plaques are ß-amyloid peptides (Aß), in two main types: 40 amino acids and 42 amino acid sequences. Aß is a 4 kiloDalton peptide that aggregates to form the least soluble, fibrillar component of AD amyloid plaques. Aßs are liberated from a transmembrane amyloid precursor protein (APP) via cleavage by ß and γ secretases. Alternatively, cleavage of APP by α secretase occurs within the Aß region, preventing the release of an intact Aß peptide. Approximately 10% of AD cases are familial and arise primarily from autosomal dominant mutations in APP, presenilin I, or presenilin II. These presenilins are essential components of γ-secretase.