New membrane model may help study the beginning of Alzheimer's

Washington, July 24 : Scientists at the National Institute of Standards and Technology (NIST) and three other institutions have developed a new model of the membrane surrounding neurons in the brain, which may help understand what role a protein may play in beginning Alzheimer's disease.

Writing about their work in the Biophysical Journal, the researchers highlight the fact that the brain's neurons transmit nerve impulses down a long stem that is surrounded by a two-layer membrane.

They also point out that medical experts have believed for years that small polypeptides called amyloid beta peptides create a "leaky" membrane that disrupts this impulse transmission, a breakdown that may start Alzheimer's disease.

The researchers say that amyloid beta peptides clump together to form plaques as the disease progresses, further destroying nerve function.

According to them, their laboratory model recreates a simplified version of the nerve cell membrane, and this may allow the study of Alzheimer's disease mechanisms at the molecular level.

In an experiment, the researchers exposed the membrane model to different concentrations of a specific form of amyloid beta peptides, which increased cation movement across the normally strong barrier at the higher concentrations of the peptides.

The data support the hypothesis that membrane "leakiness" is not due to a permanent hole being formed but rather to an aggregation of amyloid beta peptides in the membrane that allows cations to be passed from peptide to peptide across the bilayer, like a baton handed off by relay runners.

The researchers are continuing to use their model system to better understand the role amyloid beta peptides play in early-stage Alzheimer's disease.

In due course, they will be investigating how amyloid beta peptide aggregates arrange themselves in the membrane, how the peptide aggregates affect or influence calcium channels (portals for calcium ion movement) in the membrane, and how the peptides interact with membranes constructed with other types of lipids.

ANI