Study of TRP channels by automated patch clamp systems.

Ion channels are responsible for the permeation of ions across the membrane and their central role in cellular physiology is well established. Historically, the direct study of ion channels has been considered technically challenging. As such, a significant barrier to drug discovery for ion channels has been the low throughput of high quality electrophysiological data. The emergence of automated high throughput platforms for studying ion channel kinetics and pharmacology has lowered this barrier. Ion channels are now recognized as increasingly important drug targets and a diverse range of ion channels are implicated in a variety of drug discovery and cardiac safety assessment programs. The TRP (Transient Receptor Potential) superfamily of ion channels play a crucial role in a broad range of sensory functions including vision, taste, olfaction, hearing, touch, pain and thermosensation. Many of the TRP channels are polymodal in their activation and deactivation mechanisms and even with conventional patch clamp electrophysiology, the TRP channels are considered to be a very complex target class. Here we present an update on the significant progress made on the TRP receptor assays with the available automated patch clamp systems.

Upscaling and automation of electrophysiology: toward high throughput screening in ion channel drug discovery.

Effective screening of large compound libraries in ion channel drug discovery requires the development of new electrophysiological techniques with substantially increased throughputs compared to the conventional patch clamp technique. Sophion Bioscience is aiming to meet this challenge by developing two lines of automated patch clamp products, a traditional pipette-based system called Apatchi-1, and a silicon chip-based system QPatch. The degree of automation spans from semi-automation (Apatchi-1) where a trained technician interacts with the system in a limited way, to a complete automation (QPatch 96) where the system works continuously and unattended until screening of a full compound library is completed. The performance of the systems range from medium to high throughputs.

Characterization of potassium channel modulators with QPatch automated patch-clamp technology: system characteristics and performance.

Planar silicon chips with 1-2-microm etched holes (average resistance: 2.04 +/- 0.02 MOmega in physiological buffer, n = 274) have been developed for patch-clamp recordings of whole-cell currents from cells in suspension. An automated 16-channel parallel screening system, QPatch 16, has been developed using this technology. A single-channel prototype of the QPatch system was used for validation of the patch-clamp chip technology. We present here data on the quality of patch-clamp recordings and from actual drug screening studies of human potassium channels expressed in cultured cell lines. Using Chinese hamster ovary (CHO) and human embryonic kidney cells (HEK), gigaseals of 4.1 +/- 0.4 GOmega (n = 146) and high-quality whole-cell current recordings were obtained from hERG and KCNQ4 potassium channels. Success rates for gigaseal recordings varied from 40 to 95%, and 67% of the whole-cell configurations lasted for >20 min. Cells were maintained in suspension up to 4 h in a cell storage facility that is integrated in the QPatch 16. No decline in patchability was observed during this time course. A series of screens was conducted with known inhibitors of the hERG and KCNQ4 potassium channels. Dose-response relationship characterizations of verapamil and rBeKm-1 blockage of hERG currents provided IC(50) values similar to values reported in the literature.