The application of the Escherichia coli giant spheroplast for drug screening with automated planar patch clamp system

• Human Kv2.1 was expressed in the inner membrane of E. coli using prokaryotic codon.
• Bacterial spheroplasts large enough for the automated patch clamp were prepared by microfluidic chips.
• Kv2.1 current was recorded from the giant spheroplast by the automated patch clamp.
• E. coli spheroplasts were used for dose–response assay of potassium channel inhibitors.
• Our system will become the simple and sensitive drug assay method anyone can use.

Kv2.1, the voltage-gated ion channel, is ubiquitously expressed in variety of tissues and dysfunction of this ion channel is responsible for multiple diseases. Electrophysiological properties of ion channels are so far characterized with eukaryotic cells using the manual patch clamp which requires skilful operators and expensive equipments. In this research, we created a simple and sensitive drug screen method using bacterial giant spheroplasts and the automated patch clamp which does not require special skills. We expressed a eukaryotic voltage-gated ion channel Kv2.1 in Escherichia coli using prokaryotic codon, and prepared giant spheroplasts large enough for the patch clamp. Human Kv2.1 currents were successfully recorded from giant spheroplasts with the automated system, and Kv2.1-expressed E. coli spheroplasts could steadily reacted to the dose–response assay with TEA and 4-AP. Collectively, our results indicate for the first time that the bacterial giant spheroplast can be applied for practical pharmaceutical assay using the automated patch clamp.