By René A. Azeez, Honours BSc. Developmental Biology, University of Toronto. May 05, 2011.
Old science fiction has, with surprising regularity, become new science. One is reminded of this fact when encountering a new study from scientists at UCLA including David Glanzman, professor of integrative biology and physiology and of neurobiology, in the April 27 issues of the Journal of NeuroScience.The research focused on examining the effects of eliminating a particular protein kinase, an enzyme that modifies other proteins by facilitating the addition of phosphate groups to them, on the long term memory of a marine snail known as Aplysia. The protein kinase, protein kinase M (PKM), is one form of the protein kinase C (PKC) family of proteins that had previously been shown to play a critical role in mammalian long-term memory.
Snails under attack have an elevated sensitivity to their environment, a demonstration of long term memory. In training snails they showed that administration of an electric shock caused them to exhibit a reflex contraction when touched that lasted about 50 seconds, as opposed to a contraction lasting only a few seconds witnessed when snails have not experienced electric shock training. In snails which had established the long term memory from shock training, they found that administering PKM inhibitors resulted in the snails responding with a very brief contraction, the type of reaction expected had they not undergone chemical shock training.
They injected inhibitors to disallow the action of PKM and found that they successfully erased the memory for the long term sensitization (LTS) of the siphon-withdrawal reflex (SWR) of the snails for days after training. Furthermore, they saw a break from the normal occurrence; in which long term facilitation (LTF) of sensorimotor synapses underlies LTS; when the PKM inhibitors were administered. They therefore were specifically able to support the idea that PKM is important in the maintenance of long term memory in Aplysia. They were able to replicate these results using the isolated sensory and motor neurons of the snail’s nervous system in a petri dish, strengthening their hypothesis. They are in fact the first scientists to illustrate that a long-term memory can be erased at a single connection.
So what does this all mean? How can this be of importance? These results can potentially be a first step in understanding and treating conditions of addiction, post-traumatic stress, Alzheimer’s, and event associated depression, to name a few. Glanzman and his group believe that this result is the first step into understanding the formation of specific memories, and therefore the first step to some day in the future being able to target and weaken these specific memories in cases where this would be desirable. Alternatively, the possibility exists that boosting PKM activity could have beneficial implications for persons with afflicted memories, such as Alzheimer’s patients. However, the research team admits that the research is complex and we are a long way off from being at the stages of deleting specific memories or finding a magic bullet for Alzheimer’s disease. They concluded, “the demonstration of memory erasure in this relatively simple model system should greatly facilitate a reductionist analysis of how the activity of PKM supports the persistence of memory.”REFERENCES: D. Cai, K. Pearce, S. Chen, D. L. Glanzman. Protein Kinase M Maintains Long-Term Sensitization and Long-Term Facilitation in Aplysia. Journal of Neuroscience, 2011; 31 (17)
