Visualizing Kv7 channels in living cells using a novel fluorescent probe.

Kv7 (KCNQ) channels are widely expressed on the membrane of excitable cells in central nervous system and play dominant roles in controlling membrane excitability. Abnormal of their surface abundance and activity can cause central nervous system disorders such as epilepsy and painful schizophrenia. Thus, it is important to find a simple and effective molecular tool for detecting the expression of Kv7 channels and further studying their roles in physiology. Fluorescent probe is an effective method for visualizing protein analysis in biological systems with high sensitivity and spatiotemporal resolution. To further understand the roles of Kv7 channels in physiological and pathological processes, we designed fluorescent probes for imaging Kv7 channels (FPKv-1 and FPKv-2) based on the fluorescent emission mechanism of intramolecular rotation restriction using fluorophore quinoline malononitrile as report group. This mechanism was identified by the measurement of absorption and fluorescence spectra in the different solutions. Electrophysiology and confocal imaging showed that FPKv-1 had a higher affinity and selectivity to Kv7 channels over other ion channels such as TRPA1, TRPV1 and TRPV3. We also identified FPKv-1 as a molecular imaging tool can be applied in high-throughput screening of Kv7 agonists.