Parallel electrophysiological characterization of sodium channels

Ion channel proteins play a pivotal role in a wide variety of physiological processes and (chronic) diseases and are consequently of considerable interest to the pharmaceutical industry. Electrophysiology is the gold standard for investigating the function of channel proteins and their modulation by pharmaceutical drugs, particularly at single-channel level, and is the only method that enables the characterization of voltage-gated channels. It involves placing an electrode on either side of a membrane and measuring the current flow through the membrane-embedded channels, which is typically between 1 and 150 pA per channel. The key challenge is to obtain a 'Gigaseal' configuration where the two aqueous compartments are electrically insulated from each other by a stable cell membrane or lipid bilayer. This is difficult to achieve, rendering conventional electrophysiology a laborious process with a notoriously low throughput.Voltage-gated sodium channels, responsible for the transport of sodium ions across cell membranes in all eukaryotic organisms and in a range of bacteria, represent an ion channel family for which the electrophysiology is of great interest. In humans as well as lower eukaryotes these channels are essential for normal functioning; various isoforms are found in different tissues, ranging from heart to brain, with different functional roles in the healthy organism. In humans, sodium channel mutations give rise to a number of disease states, as well as being associated with ageing and pain; as a result they are the targets of many pharmaceutical drugs, including ones for treatment of epilepsy, chronic pain, and cardiovascular diseases.This proposal aims to exploit a novel platform for parallel on-chip electrophysiology, developed at the University of Southampton, for the functional characterization of a family of voltage-gated sodium channels, including human/bacterial chimeras, for which the expression, purification and reconstitution into liposomes is being developed at Birkbeck College. Specifically, the project will use this high-throughput platform to identify novel ligands/drugs that modulate the conductance properties of the sodium channels. As this project represents a collaboration between two labs with the very different but complementary expertise associated with microelectronic and microfluidic technique development & biochemical purification and characterisation of an important channel system, it falls within the cross-disciplinary theme 'Interfacing Electronics to Biology'. It combines strategic and applied research and it will train postgraduate researchers in cross-disciplinary science and technology.The potential public and economic impacts of this research are manifold. For example, voltage-gated sodium channels are essential components in human health and in agriculture. Improved knowledge of the structure/function/drug binding of these channels would impact on beneficiaries in the public, third and private industry sectors. Furthermore, the new technology platform will have many applications in industries for drug discovery and testing in addition to those in fundamental research. Commercial products with medical impact can be realized when the outcomes of this project are taken up by the leading electrophysiological companies. We will actively engage with these companies and other stakeholders by various routes, including a workshop targeted to key stakeholders in high-throughput electrophysiology. To maximize its economic and societal impact, the novel platform developed in this project -and its direct application to evaluate sodium channel drug efficacy- will be disseminated through professional publications, at major conferences with industry participation, and through press releases and active media engagement.

This project seeks to realize high-throughput single-channel electrophysiology, which has the potential to dramatically increase the rate and scope of ion channel characterization, including the screening for new pharmaceutical drugs. As a technology development, it is of immediate interest to the electrophysiological companies who have already successfully commercialized high-throughput patch clamp instruments. Single-channel electrophysiology is a powerful complementary approach; the major companies develop both types of instruments. Given the rapid uptake by the pharmaceutical industry of the high-throughput patch clamp systems that have recently come on the market, we anticipate that our high-throughput single-channel recording platform will be of immediate interest to the commercial sector. At an intermediate time scale, several years after completion of the project, the pharmaceutical industry could benefit from a powerful and cost-effective commercialized platform for the functional drug screening of ion channels. The route from the first identification of a potential new drug to approval by the relevant health authorities can take up to 15 years but the potential societal benefits are enormous, especially in view of an ageing population and an increasing socio-economical drive towards early intervention. The platform developed in this project will enable pharmaceutical companies and public sector biomedical laboratories to substantially increase the throughput and widen the scope of their drug screening programmes, hence offering the prospect of an increase in the amount of approved drugs for the many diseases that have an ion channel target. In particular, our project aims to use the high-throughput platform to perform an extensive drug screening study of our unique bacterial/human voltage-gated sodium channels that are implicated in pain perception. The pharmaceutical market for specific and highly efficacious sodium channel inhibitors/modulators is enormous, because the potential number of people with either chronic or acute pain is vast. It is for this reason that many (most) of the world - and in particular, UK - big pharma companies, as well as many smaller biotech companies have active programmes for the development of sodium channel-targeting drugs. Other sodium channel isoforms are the targets of other pharmaceuticals, notably those for treatment of epilepsy and certain cardiovascular diseases. Summarizing, the economic benefits of our novel platform for high-throughput electrophysiology concern electrophysiological and pharmaceutical companies (strong in the UK). At a longer time scale, societal benefits could arise from an increased availability of new drugs, reducing the impact of (chronic) disease and enhancing the quality of life of an ageing population. A wider range of manageable diseases may in turn reduce the cost of the healthcare system and lead to further economic benefits. The research team consists of two labs and an international collaborator with expertise in microelectronic and microfluidic technique development & biochemical purification and characterisation of an important channel system. The team has a strong track record in cross-disciplinary research and training the cross-disciplinary scientists and engineers that are central to future R&D in the UK commercial and public sector. We will also develop a simplified version of the technology for demonstration at secondary schools, promoting modern cross-disciplinary scientific research. We have extensive existing collaborations with leading international pharmaceutical and instrument companies. We will use these contacts and our wider network, which will be expanded at an international workshop dedicated to high-throughput electrophysiology, to realize the potential impact of both the specific drug screening data on our sodium channels and of the new technology itself. These efforts will be aided by professional media engagement.