Protein Provides Clue to Alzheimer’s Disease

USC researchers have developed a new clue about the cause of Alzheimer’s disease, a mystifying disease that causes mental deterioration in as many as 4 million aging Americans. The primary physical manifestation of Alzheimer’s in the brain is the accumulation of clumps of a protein called amyloid. These protein deposits may interfere with normal communication between brain cells.

Researchers do not yet know the normal role of amyloid protein in the brain, but they have recently found that it is located in the membranes of brain cells. It may thus participate in communication between cells or it may function in transporting regulatory chemicals in and out of the cells.

The first clue about why amyloid accumulates in the brains of Alzheimer’s victims was reported at a seminar last week by USC neurobiologist Caleb Finch. He said the gene that serves as the blueprint for amyloid can be read by the cell in different ways to produce at least seven different forms of the protein.

The variant forms of amyloid, he said, contain a protein fragment that blocks the activity of enzymes that would normally degrade amyloid after it has served its purpose in the brain. When their activity is blocked, amyloid can accumulate in the brain in damaging concentrations. Finch has found that as people susceptible to Alzheimer’s grow older, their cells produce a much higher percentage of this form of amyloid, thereby leading to its accumulation. He is now trying to learn why the change occurs.