"When we want to learn something we repeat the process many times. This repeated stimulation leads to a strengthening of the chemical signaling at specialized connections, called synapses, between nerve cells," says Thomas Soderling, Ph.D., associate director of OHSU's Vollum Institute and senior author of the article. "Nerve cells work by generating electrical signals which are then passed on to the next nerve cell by chemical signals at the synapse."
In a complex kind of biochemical minuet, a molecule called CaM-KII adds a chemical phosphate group to a protein receptor which relays the chemical signaling at the synapse. "This addition of a phosphate group, called phosphorylation, to the receptor facilitates communication between nerve cells by increasing the strength of the electrical signal in the second nerve cell," says co-author Andres Barria, a Ph.D. student from Chile working at the Vollum Institute.
This strengthening of communications between nerve cells, called long-term potentiation or LTP, has been extensively studied by neuroscientists. They focus on neurons in the hippocampus, a region of the brain known to be critical for memory formation. But until now, the molecular underpinnings of LTP have remained elusive.
"A large body of evidence suggests that CaM-KII is a critical player in long-term potentiation," says John Lisman, author of a perspective article in the same issue of the journal. "CaM-KII has special properties that make it an attractive candidate for exhibiting persistent changes and serving as a memory molecule. With these new results, a strong case is emerging for the importance of CaM-KII in the direct control of synaptic strength and, by implication, in the storage of information. This report is a significant step forward in our understanding of the persistent biochemical modifications that underlie this form of LTP."