PrPC when altered causes mad cow disease and vCJD but when normal prevents formation of beta amyloid.
Researchers at the University of Leeds found that the normal prions produced by the body help to prevent the plaques that build up in the brain to cause Alzheimer’s disease.
“In vCJD, the normal version of prion protein, PrPc, found naturally in the brain, is corrupted by infectious prions to cause disease. Our experiments have shown that the normal prion proteins found in brain cells reduce the formation of beta amyloid, a protein that binds with others to build plaques in the brain that are found in Alzheimer’s disease,” explains Nigel Hooper, Ph.D., a professor at Leeds and leader of the research.
Using cells grown in the lab, the team looked at the effect of high and low levels of normal prion protein in the successful formation of beta amyloid. They found that beta amyloid did not form in cells with higher than usual levels of PrPc. In comparison, when the level of PrPc was low or absent, beta amyloid formation was found to go back up again.
Mice genetically engineered to lack PrPc were also studied. Again, this revealed that in its absence, the harmful beta amyloid proteins were able to form.
It appears that PrPc, the normal prion protein, exerts its beneficial effect by stopping beta secretase from cutting up amyloid protein into the smaller beta amyloid fragments needed to build plaques.