June 8, 2009

Protein Linked To Alzheimer’s Can Spread Through The Brain

New research has shown that a rogue protein thought to cause Alzheimer's can spread through the brain, turning healthy tissue bad, BBC News reported.

The tau protein may share characteristics with the prion proteins that cause vCJD. Scientists found it triggered formation of protein tangles linked to Alzheimer's after they injected it into the brains of healthy mice.

But the study, published in the Nature Cell Biology, said this did not mean tau could be passed from person to person.

Tau is a protein present in all nerve cells and its main role is to keep the cells functioning properly. But researchers discovered that a rogue form of the protein could trigger the formation of protein clumps within nerve cells known as neurofibrillary tangles.

Such tangles are thought to be a major cause of Alzheimer's disease.

Basel and a team from University Hospital extracted sections of brain from mice expressing a mutant form of human tau protein. They then injected the extracts into specific regions in the brains of healthy mice.

They found that this induced normal human tau proteins in the healthy mice to clump together to form neurofibrillary tangles, and these newly formed tangles were also able to spread to nearby regions in the brain.

The prions, another type of rogue protein, which cause diseases such as vCJD, are thought to be able to twist themselves into a shape that gives them the ability to "infect" nearby healthy tissue.

Scientists had previously thought that tau proteins had the same contagious property.

"This opens new avenues in dementia research that will aim to understand how abnormal tau can spread. We can also investigate how diseases caused by tau aggregates and prions are similar," said Dr. Michel Goedert of the MRC Laboratory of Molecular Biology in Cambridge, who worked on the study.

The study might help explain how tangles spread from one region of the brain to another during the course of Alzheimer's, according to Professor David Allsop, an expert in neuroscience at Lancaster University.

But he warned that it did not mean that these diseases are infectious in the same way as mad cow disease and human CJD.

"There is no evidence that diseases like Alzheimer's disease and Parkinson's disease can be transmitted from one person to another," Allsop said.

However, greater understanding of how tangles spread in Alzheimer's may lead to new ways of stopping them and defeating the disease, according to Rebecca Wood, chief executive of the Alzheimer's Research Trust.

But considering the work was carried out in genetically modified mice, Dr. Susanne Sorensen, head of research at the Alzheimer's Society, stressed that there was a lot of work to be done before the implications were fully understood.

She acknowledged there was still so much they do not understand about the changes in tau that lead to tangle formation in humans and, eventually, widespread brain cell death.


On The Net:

Nature Cell Biology

MRC Laboratory of Molecular Biology

Alzheimer's Research Trust

Alzheimer's Society