Treatments to stop Alzheimer's step closer as scientists discover key inhibitor molecule

Date: Feb-18-2015Scientists have discovered a molecule that can interrupt an important stage

in the development of Alzheimer's disease. The molecule sticks to faulty proteins

and stops them forming toxic clusters in the brain.

The chaperone molecules - black dots - bind to the amyloid fibril.
Image credit: S. Cohen

The UK and Swedish researchers suggest their finding will help the discovery of

drugs that could halt Alzheimer's disease progression.

They write about their discovery and its implications in the journal Nature

Structural & Molecular Biology.

Lead author Dr. Samuel Cohen - a research fellow at St John's College in Cambridge,

UK - says with studies like theirs, we are beginning to reap the rewards of the

extensive work that has been done to increase our understanding of the microscopic

processes involved in the development of Alzheimer's. He adds:

"Our study shows, for the first time, one of these critical processes being

specifically inhibited, and reveals that by doing so we can prevent the toxic

effects of protein aggregation that are associated with this terrible

condition."

Many functions in cells are carried out by carefully folded proteins. Folding is

an energy-efficient way of ensuring distant parts of the protein molecule that need

to interact are near each other. Some of these structures are complex and need the

help of housekeeping molecules called "chaperones."

A key step in the development of Alzheimer's and other degenerative

diseases is the accumulation or "nucleation" of misfolded proteins - known as

amyloid fibrils - that do not disperse or dissolve away but form toxic clusters and

help the disease spread in the brain.

The molecule that the international team has discovered is a chaperone called

Brichos that sticks to threads of amyloid fibrils and stops them coming into contact

with each other, thus breaking the toxic chain reaction.

Brichos interrupts chain reaction that speeds up progression of Alzheimer's

Previous work by this team and others suggest there is a another critical step

in the development of Alzheimer's disease. As amyloid fibrils begin to form, they

cause other proteins to misfold and form small clusters called oligomers. These are

highly toxic to nerve cells and are thought to be responsible for the devastating

effect of Alzheimer's disease.

This second stage - called secondary nucleation - is what scientists believe sets

off the chain reaction that speeds up the progression of Alzheimer's. Without

secondary nucleation, single molecules would have to misfold and form clusters

without help - a much slower and less devastating process.

Thanks to the huge amount of work that has gone on in this field, the team has

collected a wealth of data so they can model what happens not only as Alzheimer's

progresses, but also what happens if a step is interrupted or switched off.

The study shows that Brichos effectively blocks secondary nucleation and stops the chain reaction that speeds up Alzheimer's disease.

In humans, Brichos helps proteins avoid misfolding. Lab tests showed that when

the chaperone encounters an amyloid fibril, it binds itself to sites on its surface

forming a coating that stops it helping other proteins to misfold and nucleate into

toxic oligomers.

Tests in living mice confirmed that the molecule suppressed the chain reaction

from secondary nucleation.

Dr. Cohen says it may not be difficult to find other molecules that do this; until recently, it had just been unclear what to look for. He notes:

"A good tactic now is to search for other

molecules that have this same highly targeted effect and to see if these can be used

as the starting point for developing a future therapy."

Last month, Medical News Today learned of a study that

found a significant link between high use of  anticholinergic drugs and increased risk of developing

dementia and Alzheimer's disease in older people. Anticholinergic drugs include

many popular non-prescription sleep aids and the antihistamine Benadryl

(diphenhydramine).

Written by Catharine Paddock PhD

Courtesy: Medical News Today Note: Any medical information available in this news section is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.