RT Journal Article
SR Electronic
T1 Concatenated hERG1 Tetramers Reveal Stoichiometry of Altered Channel Gating by RPR-260243
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP mol.114.096693
DO 10.1124/mol.114.096693
A1 Wei Wu
A1 Alison Gardner
A1 Michael C. Sanguinetti
YR 2014
UL http://molpharm.aspetjournals.org/content/early/2014/12/17/mol.114.096693.abstract
AB Activation of human ether-a-go-go-related gene 1 (hERG1) K+ channels mediate repolarization of action potentials in cardiomyocytes. RPR-260243 [(3R,4R)-4-[3-(6-methoxy-quinolin-4-yl)-3-oxo-propyl]-1-[3-(2,3,5 trifluorophenyl)-prop-2-ynyl]-piperidine-3-carboxylic acid] (RPR) slows deactivation and attenuates inactivation of hERG1 channels. A detailed understanding of the molecular mechanism of hERG1 agonists such as RPR may facilitate the design of more selective and potent compounds for prevention of arrhythmia associated with abnormally prolonged ventricular repolarization. RPR binds to a hydrophobic pocket located between two adjacent hERG1 subunits and hence, a homotetrameric channel has four identical RPR binding sites. To investigate the stoichiometry of altered channel gating induced by RPR, we constructed and characterized tetrameric hERG1 concatemers containing a variable number of wild-type subunits and subunits containing a point mutation (L553A) that rendered the channel insensitive to RPR, ostensibly by preventing ligand binding. The slowing of deactivation by RPR was proportional to the number of wild-type subunits (i.e., available binding sites) incorporated into a concatenated tetrameric channel, and all four binding sites were required to achieve maximal slowing of deactivation. In contrast, occupancy of only one RPR binding site was sufficient to achieve half of the maximal shift in the voltage dependence of hERG1 inactivation, and maximal effects were achieved by occupancy of three binding sites. Together our findings suggest that the allosteric modulation of channel gating involves distinct mechanisms of coupling between drug binding and altered deactivation and inactivation.