The synthesis of proteins by ribosomes is a fundamental step in the expression of genetic information by living organisms. A simple, reliable, rapid, and generalizable method for stopping this fundamental process for a specific protein with a drug would be an enormously useful tool in biomedical and translational research. It would benefit basic studies of protein function by allowing conditional expression of proteins of interest. It would provide a means for regulating protein production from gene and cellular therapies in vivo. A method for controlling synthesis of specific proteins would also allow assessment of how inducible synthesis of specific proteins contributes to particular biological responses or to disease, a line of investigation which has not been possible. In the proposed work, we will develop a novel generalizable method for shutting off synthesis of genetically tagged proteins using a small-molecule drug, and use this method to address outstanding questions on the role of new protein synthesis in nervous system adaptation. We will express proteins of interest as fusions to a potent degradation signal that undergoes autocatalytic removal. By default, the proteins will be released from the degradation signal and function normally. Application of a specific non-toxic cell-permeable drug will preserve the degradation signal on subsequently synthesized proteins, leading to their rapid degradation. We will perform experiments to validate the utility of this method in primary cells and animals, to determine the protein degradation pathways on which this method relies, and to extend the strategy to controlling production of secreted proteins. We will further use this method to test a long-standing hypothesis that synthesis of specific synapse-regulating proteins is required for memory consolidation in transgenic mice. If successful, these experiments will be groundbreaking in establishing a completely new method for controlling protein production that is rapid, robust, simple, and generalizable. The proposed research will have broad benefits in biomedical research by providing a generic method for regulating protein expression that allows more rapid kinetics than transcriptional control methods but, like transcriptional regulation, produces functional proteins without a permanent fusion tag. This work may thus facilitate studies on protein functions in general, including genome-wide screens, and provide a means for tightly controlling gene and cellular therapies in vivo. This work will also produce the first experimental tools capable of addressing the importance of specific protein synthesis events in normal physiology and disease. Thus the proposed experiments have the potential to produce a major advance in our ability to control protein function for elucidating biological mechanisms and for controlling biological therapies.