Development of an ICMT Supported Membrane Sensor

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The long term goal of this project is the development of multi-element membrane-based sensor arrays on a single chip for high-throughput, parallel sensing of therapeutic agent candidates acting on specific membrane protein targets. Successful development of this sensing technology can lead to accelerated drug discovery targeted to membrane proteins involved in a variety of diseases. We will develop a stabilized asymmetric membrane structure containing isoprenylcysteine carboxylmethyltransferase (ICMT) in this project as a potential new tool for drug discovery in cancer chemotherapy. ICMT is a membrane protein in the endoplasmic reticulum responsible for the carboxylmethylation of -CaaX motif proteins, including the Ras signal transduction proteins. This membrane sensor architecture will enable the detection of Icmt-mediated methylation of the model substrate N-acetylfarnesylcysteine as a change in fluorescence emission due to the coupled cleavage of a disulfide-linked molecular beacon. Sensors developed from these asymmetric structures will provide a direct indication of a drug candidate's ability to inhibit methylation catalyzed by Icmt. This approach will serve as a powerful tool for screening drug libraries for lead compounds that are likely to inhibit the methylation of cellular oncogenic Ras proteins. Discovery and development of these compounds are important because inhibition of Ras carboxylmethylation promotes not only the mislocalization of the Ras proteins, but also inhibits the ability of Ras to transform cells. ICMT is an excellent model system for development of this membrane-based sensor because many well-characterized substrates exist to provide data validation. These substrates will be used as tools to develop a high-throughput screening approach that may lead to improved chemotherapeutic agents for refractory tumors. Subsequent phases of the project will address the design, fabrication, characterization, and validation of multi-element sensor arrays on an optically transparent substrate. A multidisciplinary team approach will be used, combining expertise in biochemistry, materials synthesis and characterization, analytical chemistry, and theory to achieve the target supported membrane device. Future extension of this detector array concept could have far reaching potential for accelerating the discovery of new therapeutic agents targeted to many other classes of membrane-associated proteins.