A genetically encodable cell-type-specific protein synthesis inhibitor
Long-lasting memories in the brain are made possible by remodeling the connections (“synapses”) between brain cells, or “neurons”. During memory formation, the complement of proteins present at synapses is remodeled by making new proteins and degrading old ones, leading to a change in how the synapse functions- a physical impression of the memory. Studies in the 1960s performed with rats showed that injections of drugs that block protein production (protein synthesis inhibitors) during or just after learning block subsequent memory for the learned task. These early studies have been replicated over the past 50 years many times. From these experiments, we know that protein synthesis is required for memory formation, but because the chemical inhibitors block protein synthesis in all cells, it is not known which cells are important and when they need new proteins. To solve this problem, Heumueller and colleagues have borrowed a tool from plants. Many plant species have genes that encode proteins that are potent inhibitors of protein synthesis- they use these inhibitors to ward off predators. In the upcoming online issue of Nature Methods, an international team of scientists, led by Erin Schuman, director at the Max Planck Institute for Brain Research, modified the plant protein so that it’s expression can be controlled: researchers can turn on and off the protein synthesis inhibitor in the right cells at the right time. The team calls their modified protein gePSI- for genetically encodable protein synthesis inhibitor. The gePSI can be used to study which cells are important for learning and memory but also might be useful in very different situations. For example, it could be used to block protein synthesis in cancer cells.