The same pathway is also found at human synapses, and the researchers say it could eventually present a target for new therapeutics to treat human memory loss.
The researchers found that messenger RNA (mRNA), a genetic photocopy that conveys information from DNA to a cell’s translation machinery, is transported to synapses as a memory begins to form.
This mRNA transport, and the protein synthesis that follows, are facilitated by components of the RISC pathway. This is a biochemical pathway that determines if and where this protein synthesis happens. Very short RNA molecules called microRNAs are used to guide their activity.
One of these RISC proteins, called Armitage, appears to be a critical regulatory molecule in long-lasting memory formation, and has to be destroyed at particular synapses in order for protein synthesis to occur there.
By manipulating the RISC pathway, the researchers were able to alter the memory of the flies, changing their response to stimuli in subsequent behavioral tests. Using a classical learning test that simultaneously exposes the insects to an odor and an electric shock, the researchers found that long-term memory could be greatly increased by adjusting the activity of the RISC pathway in the fruit flies.
“It has been known for some time that learning and long-term memory require synthesis of new proteins, but exactly how protein synthesis activity relates to memory creation and storage has not been clear,” said Sam Kunes, professor of molecular and cellular biology in Harvard’s Faculty of Arts and Sciences.