Development of a QPatch Automated Electrophysiology Assay for Identifying KCa3.1 Inhibitors and Activators

Abstract The intermediate-conductance Ca2+-activated K+ channel KCa3.1 (also known as KCNN4, IK1, or the Gardos channel) plays an important role in the activation of T and B cells, mast cells, macrophages, and microglia by regulating membrane potential, cellular volume, and calcium signaling. KCa3.1 is further involved in the proliferation of dedifferentiated vascular smooth muscle cells and fibroblast and endothelium-derived hyperpolarization responses in the vascular endothelium. Accordingly, KCa3.1 inhibitors are therapeutically interesting as immunosuppressants and for the treatment of a wide range of fibroproliferative disorders, whereas KCa3.1 activators constitute a potential new class of endothelial function preserving antihypertensives. Here, we report the development of QPatch assays for both KCa3.1 inhibitors and activators. During assay optimization, the Ca2+ sensitivity of KCa3.1 was studied using varying intracellular Ca2+ concentrations. A free Ca2+ concentration of 1 μM was chosen to optim...