Protein complex in brain may be key to Alzheimer’s

• Neurology • Mar 16, 06

Scientists in the U.S. say they have discovered a substance in the brain of mice that causes memory loss; they believe the discovery gives drug developers a target for creating drugs to treat memory loss in people with dementia.

Researchers at the University of Minnesota Medical School in Minneapolis and the VA Medical Center, by using genetically engineered mice that showed early signs of memory loss and had no plaques or nerve cell loss in the brain, discovered a form of the amyloid-beta protein that is distinct from plaques.

Once extracted and purified, the newly found protein complex was injected into healthy rats and it triggered cognitive impairment in the tested animals, confirming the detrimental effect of this protein on memory.

Professor of Neurology Karen H. Ashe, M.D., Ph.D., who led the research team, says that finding the specific cause of memory loss and cognitive decline gives scientists a protein complex to target.

She says they can now begin to work on how that protein leads to the disease and what can be done to prevent it from harming the brain.

Currently about 4.5 million Americans and 12 million people worldwide suffer from Alzheimer’s disease, a number that is projected to increase to 14 million in the next 20 years.

The progressive and debilitating illness which robs people of their memory and mental ability, has no cure, but drug treatments may slow the early progression of the disorder.

In the past, it was generally accepted that Alzheimer’s disease was caused by plaques and tangles, unnatural accumulations of two naturally occurring proteins in the brain: amyloid-beta, which builds into plaques between nerve cells in the brain; and tau, which forms the tangles bundles inside nerve cells.

Ashe’s team proved last year that the tangles are not the cause of memory loss; this latest research shows the plaques aren’t a major cause either.

People with Alzheimer’s disease exhibit memory impairment before they are formally diagnosed, or before nerve cells in their brains begin to die.

Often it can be difficult to tell whether people are experiencing the normal memory impairment that comes with aging or if they are in the early stages of Alzheimer’s disease.

The researchers believe the protein complex impairs memory independently of plaques or nerve loss and may contribute to the drop in cognitive function associated with Alzheimer’s.

The research was done in collaboration with scientists at Johns Hopkins University, University of Southern California, and University of California, Irvine.

The findings are reported in the journal Nature.