In Alzheimer's disease, too much beta-amyloid is produced by an enzyme that has many other essential roles. As a result, simply blocking the whole enzyme knocks out many of its other functions which is fatal to the organism.
Using cultured human and mouse cells, as well as test-tube assays, UT Southwestern researchers singled out how just one portion of the enzyme, a protein called nicastrin, is involved in the pathway that produces beta-amyloid, thereby leading to Alzheimer's disease. They hope next to work on ways to specifically block nicastrin. The study appears in the August 12 issue of the journal Cell.
"The work provides an attractive potential strategy for developing treatment for Alzheimer's disease," said Dr. Gang Yu, assistant professor in the Center for Basic Neuroscience and of cell biology and senior author of the study. The research uncovered an "unprecedented mechanism of biochemistry," Dr. Yu said.
Nicastrin is a large protein that is a component of an enzyme called gamma-secretase, which is lodged in the cell's membrane. When it is at the cell surface, nicastrin sticks out into the area outside the cell. It has been thought to play a key role in the creation of a protein called amyloid-beta the prime suspect for the damage Alzheimer's does to the brain but the exact mechanism was unknown.
Dr. Yu and his colleagues found that nicastrin binds to several proteins lodged in the cell's membrane, including one called amyloid precursor protein, or APP. Nicastrin then guides membrane-bound proteins to the active area of gamma-secretase, which then splits the proteins. APP, for example, is chopped into
Contact: Aline McKenzie
UT Southwestern Medical Center