Protein Isolated for Memory Formation

May 4, 2012 § Leave a comment

A report published in the March 2 issue of Cell reveals a finding that may link microRNAs to memory and the learning process in general. Scientists at the John Hopkins University School of Medicine studied genetic material that controls protein formation in the brain and found that certain microRNAs control the actions of brain-derived neurotrophic factor (BDNF), which are linked to brain cell survival, learning, and memory boosting. These findings implicate that the use of a drug meant to enhance this function may prevent the mental illness that results from brain wasting diseases such as Huntington’s, Alzheimer’s, and Parkinson’s disease.

BDNF, a growth-factor protein, is released in the hippocampus during the learning process. This protein increases the activity of other proteins involved in memory formation, but only increases production of less than 4% of the brain cell proteins. Mollie K. Meffert, M.D., Ph.D., associate professor of biological chemistry and neuroscience at John Hopkins was determined to find out how BDNF decides which proteins to stimulate, and what is the role of the regulatory microRNAs – small molecules that block protein blueprint messages from being transferred to proteins by binding to them. Too many of these within a cell will halt protein production. Likewise, a loss of certain microRNAs will cause a higher production of proteins.

The researchers compared microRNA levels in the brain cells treated with BDNF to those left untreated. The former had lower levels of microRNAs, suggesting that BDNF controls the levels of these microRNAs, in turn affecting protein production. The microRNAs that were disappearing in the presence of BDNF were all Let-7 microRNAs.

The team then genetically engineered neurons that would stop decreasing Let-7 microRNAs to see if the loss of Let-7 microRNAs would cause BDNF to increase production of proteins. Treating the neurons with the BDNF no longer resulted in decreased microRNA levels (or increased learning and memory proteins). The researchers also found more than 174 microRNAs that increased due to the BDNF therapy, suggesting it may also increase other microRNAs, possibly decreasing the production of proteins that need to be decreased in learning and memory formation.

To confirm these findings, the researchers observed living brain cells to find out how brain messaging responds to the BDNF. The ones that are never translated into the production of proteins can build up within cells. The researchers observed through microscope a lab dish that contained brain cells that had been denoted with a fluorescent molecule. This labeled the formations with glowing spots. Those cells treated with BDNF cells increased in size and number, indicated by the glowing spots. The researchers learned that BDNF uses the microRNA to deliver messages to the spots, where they can be dispelled from the translating apparatus that renders them into proteins.

Meffert said, “Monitoring these fluorescent complexes gave us a window that we needed to understand how BDNF is able to target the production of only certain proteins that help neurons to grow and make learning possible.” He goes on to say that because the team is now aware of how BDNF increases proteins involved in learning and memory formation, they will be able to explore a possible therapy targeted to improve the mechanism in order to treat patients with mental disorders and neurodegenerative diseases.

Works Cited

“Making Memories: How 1 Protein Does It”. (March 5, 2012). Neuroscience News. March 9, 2012.



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