Dr. Tanzi’s first breakthrough discovery was identifying the first
Alzheimer’s gene, the gene responsible for producing the amyloid
precursor protein (APP), which gives rise to toxic brain
beta-amyloid, the initial trigger of Alzheimer’s disease. Despite
being told at Harvard that brain amyloid was just protein garbage
and irrelevant to the disease, he insisted there had to be a gene
linked to it, and mutations in this gene would cause Alzheimer’s. He
was right.
When APP is cut by certain enzymes, it releases the amyloid
beta-protein, a sticky protein that, in excess, forms beta-amyloid
plaques in the brain — the main toxins causing Alzheimer’s. Like
cholesterol, the amyloid beta-protein, the principal component of
beta-amyloid, is necessary in small amounts (to protect against
brain infection and regulate the nerve cell communication), but, in
excess, causes beta-amyloid deposition, which acts like a lit match
to spark disease. It is now clear - the faster one accumulates
beta-amyloid in the brain, the sooner one gets Alzheimer’s disease.