Proteins Promote Brain Cell Growth

Healthy prion proteins spur the formation of brain cells, according to a new study­ published in the Proccedings of the National Academy of Sciences by Harvard-affiliated researchers.

Prior to the study, which was conducted in the laboratory of MIT Professor Susan L. Lindquist at the Whitehead Institute in Cambridge, investigations had focused on the importance of the abnormal folding of certain prions, often associated with “mad cow” disease.

This abnormal structure results in the inability of the proteins to be broken down by enzymes, and subsequently in the accumulation of the protein in the brain­—which leads to disease.

However, according to Lindquist, once scientists identify the characteristics of healthy prions, it may be possible to prevent them from becoming abnormal.

“Maybe if we knew the biological function of the [healthy] prions, we could lock them into the normal protein structure,” she said.

Lindquist, along with colleagues at the Harvard Medical School, found that in embryonic brain cells where healthy prion concentration was high, there was an increase in the proliferation of the brain cells.

Researchers tested the levels of healthy prions—abbreviated as Prp(c)s—on the embryonic brain tissue of mice both with and without Prp(c) genes, along with mice that overexpressed the gene.

The mice that overexpressed the gene had markedly increased amounts of proliferating cells, while those that lacked the Prp(c) gene had lower amounts of cell formation, yet grew into normal adults.

Lindquist said this indicates healthy prions must have a function that is not essential to the survival of the cell.

A post-doc in the lab, Andrew Steele, proposed the study three years ago.

Lindquist said Steele became interested in the normal function of prions after noticing high concentrations of healthy prions in stem cells.

In an e-mail, Steele said the lab might now study the function of the Prp(c) gene in adult stem cells. They may also investigate the signaling pathways that involve healthy prions.