A cell-free system for assaying ion channel function

DESCRIPTION (provided by applicant): Ion channels function as cell-signaling effectors for a diverse range of physiological activities, including nerve signal propagation, muscle contraction, cardiopulmonary regulation, and cell metabolism. Their impact on human health is underscored by the existence of forty compounds, including about 15% of the top 100 best-selling drugs, that target ion channels for treatment of important neurological and cardiovascular diseases. Potassium channels, among the most well-studied ion channel classes, are targets for treating diseases such as multiple sclerosis and breast cancer, but their cross-reactivity with drugs is also a major cause of unwanted drug side-effects, responsible for more than 50% of all drug withdrawals from the market since 1998. Despite their biomedical significance, ion channels remain resistant to many traditional and emerging modes of manipulation and detection, in large part because they are topologically complex membrane proteins that span the lipid bilayer of the cell multiple times. Assays for ion channel function usually require the use of living cells because the cellular membrane maintains both ion channel structure and an electrochemical barrier that creates the potential for cellular electrical signals. However, cells possess inherent limitations in size and environmental requirements that, restrict their application to emerging nano- and micro-scale devices that are becoming increasingly important in high-throughput and high-resolution studies of protein function. New methods of manipulating ion channels and studying their function are needed to aid the development of new drugs and to reduce ion channel cross-reactivity. The purpose of this proposal is to develop a product that will measure ion channel function without the need for living cells and with significantly greater applicability to nano- and micro-scale detection devices. We have developed a novel technology, the Lipoparticle, that enables stable manipulation of native ion channels in a nano-scale format. We use non-infectious membrane-enveloped retroviral structures as membrane protein presentation vehicles, eliminating the need for whole cells or detergent-based protein purification. In manuscripts published previously, we demonstrated that Lipoparticles could incorporate diverse membrane proteins, that the membrane proteins retained their native structure, and that the particles could be used to study biomolecular interactions. In previous studies we demonstrated that ion channels could be incorporated into Lipoparticles, and in Phase 1 studies we demonstrated that ion channels could function within the Lipoparticle.