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Aug 1, 2009 (Vol. 29, No. 14)

Innovative Drug Screening Methodologies

New Assays Streamline Scrutiny of Cellular and Molecular Binding Events

  • Analyzing Altered Ion Channels

    NMI Ion Channel Services investigates the function and dysfunction of ion channels for pharma and biotech companies, according to Timm Danker, Ph.D., a scientist with the firm. “Today although more than 300 ion-channel genes are known through the human genome project, only about 100 have been isolated and tested.”

    Clearly, the automation and adaptation for high-throughput platforms would profoundly affect the capacity of investigators to screen, using electrophysiological approaches, promising ion channel drug candidates. The Roboocyte is an automated, flexible platform for voltage-clamp recordings on Xenopus laevis (the African tree frog) oocytes adaptable to a wide range of applications.

    In the oocyte voltage clamp technique, two microelectrodes are pierced into the cells membrane. The cell can then be stimulated and current changes can be measured under different conditions, including treatment with candidate drugs. The Roboocyte is configured to allow the individual testing of large numbers of oocytes in conical wells.

    Accurate, fast, and versatile, it can be left unattended overnight to yield up to 2000 data points in a month’s time, when three machines are employed simultaneously. The data is highly reproducible, with clean kinetics, he added.

    Dr. Danker and his colleagues evaluated the selectivity of blockers of the closely related channels Kv1.3 (expressed in T lymphocytes) and Kv1.5, expressed in cardiomyocytes. Using standard molecular biology protocols, the genes for these channels and other proteins of interest can be cloned and expressed in the Xenopus oocytes. They showed highly reproducible dose response curves, which present a basis for selectivity-screening of molecules of interest.

    On the drawing board are plans to extend these studies to point-mutated ion channels using a high throughput approach.

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