β‐Amyloid Toxicity: Diverse Biological Activities Drive Multiple Cellular Mechanisms

Beta-amyloid is a 40-42 amino acid peptide derived from the processing of the amyloid precursor protein. Beta-amyloid assumes many different conformations, which are capable of different biological activities. Yet, the in vivo role of Beta-amyloid in neuronal degeneration is still controversial, possibly because it can assume so many biological roles or personalities. In this chapter, we propose a multiple variable model for the role of Beta-amyloid and suggest that a major part of the controversy surrounding the role of Beta-amyloid in neurodegeneration and Alzheimer's disease is that it does not fit the single factor model that is so pervasive in current research.