Mutant-selective proteolytic logic of EGFR

Many cancers are addicted to the activity of a certain protein to accelerate cellular growth and thus promote the disease. Often the enhanced protein activity is mediated by genetic alteration or mutations of the encoding gene. One such example is the protein kinase EGFR, which is frequently mutated in lung cancer, the leading cause of cancer-related death in the western world. While the mutations enable the enhanced protein activity required to drive uncontrolled cellular growth, they seem to come at a cost: the stability of the mutated protein is reduced compared to the original non- mutated protein. We propose that this may provide a true Achilles heel to enable novel ways to interfere with cancer if we can understand how activity and stability of a protein are interconnected. From a translational perspective, we could envision making use of this concept and further push the disease-causing protein into being even less stable and thus destroy the key driver for the uncontrolled cellular growth. In this project we will study how different mutations affect protein stability and activity focusing on EGFR. Importantly, we will use a strategy termed saturating mutagenesis, which enables us to look at every possible mutation for target regions within the EGFR protein, also reaching beyond those known to cause disease and constrained by evolution. With this stability and activity landscape in hand we can then untangle key hotspots or molecular switches that may provide novel starting points for therapeutic intervention to enhance mutant EGFR turnover. Next, we will uncover what cellular machineries oversee the altered turnover. Here we will focus on disease-causing mutations in combination with the uncovered molecular switches. Are novel interactions within the cell important drivers of enhanced turnover, or are we losing important interactions that, in the non-disease setting, protect wild-type EGFR from being destroyed? With this study, we expect to generate fundamental insights into why activating mutations enhance protein turnover, while also providing a novel entry point for alternative therapeutic strategies. EGFR serves as an ideal foundation to elucidate this question, given the urgent need for new therapeutic approaches. Furthermore, we believe that the insights gained from this study will be applicable to other proteins, including other kinases implicated in various types of cancer and diseases. Targeted protein degradation has emerged as a significant advancement in pharmacology, revolving around the elimination of disease-causing proteins. By offering new insights into the cellular machineries that integrate this converse relationship between activity and stability, we aim to contribute novel strategies for its implementation.