Neurofibrillary tangles odd, twisted clumps of protein found within nerve cells are a pathological hallmark of Alzheimer's disease. The tangles, which were first identified in the early 1900s by German psychiatrist and neuropathologist Aloysius Alzheimer, are formed when changes in a protein called tau cause it to aggregate in an insoluble mass in the cytoplasm of cells. Normally, the tau protein is involved in the formation of microtubules, hollow filaments that provide cells with support and structure; abnormal tau tangles, however, cause that structure to break down, and lead to cell death.
Researchers have long puzzled over just what produces the tangles and, indeed, if they are a cause or a side effect of Alzheimer's and similar neurodegenerative diseases. Now, new research by Eva Chi, an assistant professor of chemical engineering at the University of New Mexico, and her colleagues suggests that changes to the lipid membranes of nerve cells initiate tangle formation.
"Proteins in the brain do not aggregate spontaneously to form amyloid fibrils to cause diseases," says Chi. Rather, she says, "there are physiological triggers that cause these proteins to start aggregating and the lipid membrane may serve such a role." At the AVS Symposium in Nashville, Tenn., held Oct. 30 Nov. 4, Chi will discuss these tangling triggers and their implications for the development of new Alzheimer's therapies.
Using a combination of techniques, including fluorescence microscopy and X-ray and neutron scattering imaging, Chi and her colleagues found that tau proteins inside nerve cells interact strongly with negatively charged lipids, which are found on the inner surface of cell membranes. "In diseased brains, tau proteins become hyperphosphorylated" adorned with multiple phosphate (PO43-) groups "and detach from microtubules. They can then interact with the negatively charged lipids on the cell membrane and start to aggregate into fibrils and
|Contact: Catherine Meyers|
American Institute of Physics