Scientists Find Protein That Causes Memory Loss

MICHELE NORRIS, host:

News today from the frontlines in the battle against Alzheimer's Disease. Scientists have found a molecule that appears to play a critical role in the memory loss associated with the disease. The molecule starts its insidious destruction of the brain long before damage is visible.

NPR's Joe Palca has our report.

JOE PALCA reporting:

The brains of patients with advanced Alzheimer's look strange. They're filled with tangled bundles of fibers and peculiar clumps of protein. What's more, nerve cells in parts of the brain crucial for memory die off.

Now it's tempting to look at all this damage and say, aha, that must be what's causing the memory problems, but neuroscientist Karen Ash says that's a mistake.

Dr. KAREN ASH (University of Minnesota Medical School): What we're finding now is that Alzheimer's Disease, the process itself probably begins long before neurons are lost. It may begin decades before patients show up at the doctor's office.

PALCA: Ash leads an Alzheimer's research team at the University of Minnesota Medical School in Minneapolis. The team studies a special breed of mice that have a form of Alzheimer's. She's been using the mice to hunt down candidate molecules that might play a role in the early stages of the disease.

Dr. ASH: It's a three-step process whereby first you identify the candidate and the candidate has to be present in animals that are impaired and not present in animals that are not impaired.

PALCA: In step two, Ash extracts the candidate molecule from the brains of mice that are showing signs of memory loss.

Dr. ASH: And then step three is to apply it to the brain of a normal animal and determine whether you can induce memory impairment.

PALCA: As she reports in the current issue of the journal Nature, she's found a candidate that has gone through all three steps. It's a molecule made of 12 proteins, known individually as amyloid beta, linked together. Alzheimer's researcher Dennis Selco of Brigham and Women's Hospital in Boston says Ash has found what a lot of researchers have been looking for, namely --

Dr. DENNIS SELCO (Brigham and Women's Hospital, Boston): That a certain, well- defined, bio-chemically isolated form of amyloid beta protein can short circuit memory and learning.

PALCA: Although Selco says other researchers including himself have other candidate molecules. Huda Zoghbi is Howard Hughes Medical Investigator at Baylor College of Medicine in Houston. She says Karen Ash has more work to do before she can say with certainty her candidate is the correct one.

Dr. HUDA ZOGHBI (Baylor College of Medicine, Houston): It's not quite yet the proof until you really show the mechanism by which it's doing it and this way you know for sure it's not guilt by association, but it's truly the toxic agent.

PALCA: For her part, Ash agrees she'll have to find some drug that blocks her candidate molecule, give that drug to an animal showing early signs of Alzheimer's --

Dr. ASH: And show that it prevents the disease or wipes it out in a very significant way. That's the only way that this hypothesis will get firmly proven.

PALCA: Ash has taken her candidate through step one in humans. She says she's shown that patients with Alzheimer's have detectable amounts of the molecule, whereas people who don't have Alzheimer's do not. She's now trying to show that the molecule is present in people who have no symptoms at the moment, but who later develop full-blown signs of the disease.

And if it is, neuroscientist Richard Morris of the University of Edinburgh in Scotland says that would allow doctors to diagnose Alzheimer's in its earliest stages.

Dr. RICHARD MORRIS (University of Edinburgh, Scotland): And that early diagnosis is going to be really, really helpful when it comes to testing any kind of new therapies that might be able to help people through the first few years of this condition. We may not be able to stem the tide completely, but to help people through the first few years, to be able to carry on living an independent life for just that little bit longer.

PALCA: And Morris says for people facing the onslaught of Alzheimer's, that would be an important step.

Joe Palca, NPR News, Washington. Transcript provided by NPR, Copyright NPR.