Protein discovery could lead to depression test

By Julie Steenhuysen

CHICAGO (Reuters) - Changes in the location of a single protein in the brain could be used to tell whether a person with depression is responding to an antidepressant within days of taking the drug, U.S. researchers said on Tuesday.

People with depression now must wait weeks before they learn whether the drug they are taking will bring relief.

But researchers at the University of Illinois at Chicago have discovered that a single protein in the brain changes its location within a cell membrane when an antidepressant is working, and this change could be identified with a simple blood test.

"The possibility there, is if we look at blood from a patient on day zero and day four or five, we'll know whether the antidepressant would be effective," said UIC's Dr. Mark Rasenick, whose study appears in the Journal of Neuroscience.

His team compared brain samples from depressed people who had committed suicide with those from people who had no history of psychiatric disorders.

What they found was a key difference in the location of a signaling protein known as Gs alpha -- which is important for the action of neurotransmitters or message-carrying chemicals such as serotonin.

In people with depression, this protein is trapped in what Rasenick called a "lipid raft" inside the cell membrane. While stuck in this thick, gluey area of the cell, the signaling protein seemed less effective at directing the action of message-carrying chemicals.

In tests on rats and in cell cultures done in Rasenick's lab, antidepressants helped move the Gs alpha protein into an area of the cell where it could be more effective.