Alzheimer's protein involved in brain protection

By studying fruit flies, Belgian investigators have discovered that the normal function of the amyloid precursor protein (APP), which has been implicated in Alzheimer's disease, is to stimulate the growth of nerve paths in the brain. This may aid in recovery after brain injury, but may also contribute to the development of Alzheimer's disease.

"In an ironic twist of evolution," lead investigator Dr. Bassem A. Hassan told Reuters Health, "a protective protein, which probably allows the brain to survive and function robustly as we go through the stressful, productive phases of our lives, produces, as an inevitable consequence of its necessary function, a toxic peptide that impairs us in old age."

The normal function of APP, one of the most important proteins related to Alzheimer's disease and the protein that gives rise to amyloid-beta, has been unclear, Hassan from the Flanders Interuniversity Institute for Biotechnology in Leuven and colleagues point out in the EMBO Journal, the journal of the European Molecular Biology Organization.

Alzheimer's disease (AD), one form of dementia, is a progressive, degenerative brain disease. It impairs memory, thinking, and behavior.

Memory impairment is a necessary feature for the diagnosis of this or any type of dementia. Change in one of the following areas must also be present: language, decision-making ability, judgment, attention, and other areas of mental function and personality.

The rate of progression is different for each person. If AD develops rapidly, it is likely to continue to progress rapidly. If it has been slow to progress, it will likely continue on a slow course.

To investigate, Hassan and his colleagues conducted a series of studies in the brains of fruit flies. The researchers found that human APP and its fruit fly counterpart, APPL, promoted nerve cell branching in the brains of mature fruit flies. Brain injury in the fruit fly stimulated APPL in nerve cells - and fruit flies genetically engineered to lack APPL showed increased mortality after traumatic brain injury.

Dr. Hassan said that it appears, at least in fruit flies, "that a pathway triggered by APP may be able to induce re-growth of injured (nerve cell) connections. If the same is true in mammals, then turning on that pathway may one day provide a way of restoring the connection of severed nerves."

The findings may also have implications in the understanding of some aspects of the development of Alzheimer's disease, as well as the link between traumatic brain injury and Alzheimer's disease.

The following steps can help people with Alzheimer's disease: