| The deposition of the amyloid beta peptide (Abeta) in the brain is central to Alzheimer's disease pathogenesis and may be the primary insult from which all the pathology and symptoms of Alzheimer's disease result. The mechanisms leading to the generation and deposition of Abeta are therefore areas of intense investigation as understanding them may lead to the development of treatments for Alzheimer's disease. Currently, the available therapies are of Little benefit. Abeta is generated from the amyloid precursor protein (APP) following several sequential cleavages. The ultimate cleavage of APP is mediated by a complex of four proteins known as the gamma-secretase. Genetic mutations in one gamma-secretase complex member, presenilin, are known to alter the generation of Abeta and to cause familial Alzheimer's disease. Because the remaining complex members, Pen-2, Aph-1, and nicastrin, have only recently been identified, little is known about the assembly and function of the gamma-secretase complex. Therefore, the manner in which mutations in presenilin result in Alzheimer's disease is unclear. This thesis describes the membrane topology of Pen-2 which I showed is a hairpin structure with the N- and C-termini facing the ER lumen. Furthermore, the thesis examines the metabolism of Pen-2 revealing that Pen-2 must interact rapidly with its binding partner, presenilin, or be subjected to rapid proteasomal degradation. These findings will guide future studies aimed at understanding the regulatory mechanisms and assembly of the gamma-secretase complex. Abeta, as well as two other proteins deposited in brain amyloidoses (alpha-synuclein and tau), is deposited in diseased brain as beta-helical fibrillar deposits. By inhibiting the aggregation of these proteins it may be possible to ameliorate toxicity and prevent disease progression. For this reason, tools to study their aggregation are of great value. This thesis describes the use of a novel fluorescent dye, K114, to quantitatively monitor the fibrillogensis of Abeta, alpha-synuclein, and tau. This work is considered in the context of field-wide advances of Alzheimer's disease research with a focus on the mechanisms of disease pathogenesis. |
