TY - JOUR T1 - Reporting Sodium Channel Activity using Calcium Flux: Pharmacological Promiscuity of Cardiac Nav1.5 JF - Molecular Pharmacology JO - Mol Pharmacol DO - 10.1124/mol.114.094789 SP - mol.114.094789 AU - Hongkang Zhang AU - Beiyan Zou AU - Fang Du AU - Kaiping Xu AU - Min Li Y1 - 2014/11/24 UR - http://molpharm.aspetjournals.org/content/early/2014/11/24/mol.114.094789.abstract N2 - Voltage-gated sodium channels (Navs) are essential for membrane excitability and represent therapeutic targets for treating human diseases. Recent reports suggest that these channels, e.g., Nav1.3 and Nav1.5, are inhibited by multiple structurally distinctive small molecule drugs. These studies give reason to wonder whether these drugs collectively target a single site or multiple sites in manifesting such pharmacological promiscuity. We thus investigate pharmacological profile of Nav1.5 through systemic analysis of its sensitivity to diverse compound collections. Here we report a dual-color fluorescent method that exploits a customized Nav1.5 (SoCal5) with engineered enhanced calcium permeability. SoCal5 retains wild-type Nav1.5 pharmacological profiles. Wild-type SoCal5 and SoCal5 with local anesthetics binding site mutated (F1760A) could be expressed in separate cells, each with a different-colored genetically encoded calcium sensor, which allows a simultaneous report of compound activity and site dependence. Pharmacological profile of SoCal5 reveals a hit rate (>50% inhibition) around 13% at 10 μM, comparable to that of hERG. The channel activity is susceptible to blockage by known drugs and structurally diverse compounds. The broad inhibition profile is highly dependent on the F1760 residue in the inner cavity, a residue conserved among all nine subtypes of Nav channels. Both promiscuity and dependence on F1760 seen in Nav1.5 were replicated in Nav1.4. Our evidence of a broad inhibition profile of Nav channels suggests a need to consider off-target effects on Nav channels. The site-dependent promiscuity forms a foundation to better understand Navs and compound interaction. ER -