A small molecule known to regulate white blood cells has a surprising second role in protecting brain cells from the deleterious effects of stroke, Johns Hopkins researchers report. The molecule, microRNA-223, affects how cells respond to the temporary loss of blood supply brought on by stroke - and thus the cells' likelihood of suffering permanent damage.
"We set out to find a small molecule with very specific effects in the brain, one that could be the target of a future stroke treatment," says Valina Dawson, Ph.D., a professor in the Johns Hopkins University School of Medicine's Institute for Cell Engineering. "What we found is this molecule involved in immune response, which also acts in complex ways on the brain. This opens up a suite of interesting questions about what microRNA-223 is doing and how, but it also presents a challenge to any therapeutic application." A report on the discovery is published in the Nov. 13 issue of the Proceedings of the National Academy of Sciences.
RNA is best known as a go-between that shuttles genetic information from DNA and then helps produce proteins based on that information. But, Dawson explains, a decade ago researchers unearthed a completely different class of RNA: small, nimble fragments that regulate protein production. In the case of microRNA, one member of this class, that control comes from the ability to bind to RNA messenger molecules carrying genetic information, and thus prevent them from delivering their messages. "Compared with most ways of shutting genes off, this one is very quick," Dawson notes.
Reasoning that this quick action, along with other properties, could make microRNAs a good target for therapy development, Dawson and her team searched for microRNAs that regulate brain cells' response to oxygen deprivation.
To do that, they looked for proteins that increased in number in cells subjected to stress, and then examined how production of these proteins was regulated. For many of them, microRNA-223 played a role, Dawson says.