The study, led by Raymond Swanson, MD, chief of neurology and rehabilitation services at SFVAMC, identified the protein known as EAAC1 in mice and as EAAT3 in humans as the main mechanism through which the amino acid cysteine is transported into neurons. Cysteine is an essential component of glutathione, which Swanson terms "the most important antioxidant in the brain."
It had been thought previously that the main function of the protein was to remove excess glutamate, a neurotransmitter, from brain cells.
"It's known that neurons don't take up cysteine directly, and it's never been clear exactly how it gets there," says Swanson, who is also professor and vice chair of neurology at the University of California, San Francisco. "This study provides the first evidence that EAAC1 is the mechanism by which cysteine gets into neurons and that transporting cysteine is probably its chief function."
Study findings are currently available in the Advance Online Publication section of Nature Neuroscience.
Antioxidants such as glutathione provide protection from oxidative stress, which kills cells through the "uncontrolled reaction of lipids in the cells with oxygen--basically, burning them out," says Swanson. Since the brain uses a lot of oxygen and is "chock full of lipids," it is particularly vulnerable to oxidative stress, he notes.
In the first part of the study, Swanson and his co-authors observed a colony of mice deficient in the gene responsible for the production of EAAC1 and compared their behavior with that of a colony of normal, or "wild type," mice. They noticed that around the age of 11 months old age for a mouse the gene-def
Contact: Steve Tokar
University of California - San Francisco