TY - JOUR T1 - C-linker Accounts for Differential Sensitivity of ERG1 and ERG2 K+ Channels to RPR260243-Induced Slow Deactivation JF - Molecular Pharmacology JO - Mol Pharmacol DO - 10.1124/mol.115.098384 SP - mol.115.098384 AU - Alison Gardner AU - Michael C. Sanguinetti Y1 - 2015/01/01 UR - http://molpharm.aspetjournals.org/content/early/2015/04/17/mol.115.098384.abstract N2 - Compounds can activate human ether-a-go-go-related gene 1 (hERG1) channels by several different mechanisms, including a slowing of deactivation, an increase in single channel open probability, or a reduction in C-type inactivation. The first hERG1 activator to be discovered, RPR260243 ((3R,4R)-4-[3-(6-methoxyquinolin-4-yl)-3-oxo-propyl]-1-[3-(2,3,5-trifluoro-phenyl)-prop-2-ynyl]-piperidine-3-carboxylic acid; "RPR" induces a pronounced, voltage-dependent slowing of hERG1 deactivation. The putative binding site for RPR, previously mapped to a hydrophobic pocket located between two adjacent subunits, is fully conserved in the closely related rat ether-a-go-go-related gene 2 (rERG2), yet these channels are relatively insensitive to RPR. Here we use site-directed mutagenesis and heterologous expression of channels in Xenopus oocytes to characterize the structural basis for the differential sensitivity of hERG1 and rERG2 channels to RPR. Analysis of hERG1-rERG2 chimeric channels indicated that the structural determinant of channel sensitivity to RPR was located within the cytoplasmic C-terminus. Analysis of a panel of mutant hERG1 and rERG2 channels further revealed that 7 residues, 5 in the C-linker and 2 in the adjacent region of the cyclic nucleotide-binding homology domain (CNBHD), can fully account for the differential sensitivity of hERG1 and rERG2 channels to RPR. These findings provide further evidence that the C-linker is a key structural component of slow deactivation in ERG channels. ER -