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Modulation of K v 11.1 (hERG) channels by 5‐(((1H–indazol‐5‐yl)oxy)methyl)‐N‐(4‐(trifluoromethoxy)phenyl)pyrimidin‐2‐amine (ITP‐2), a novel small molecule activator
Author(s) -
Sale Harinath,
Roy Samrat,
Warrier Jayakumar,
Thangathirupathy Srinivasan,
Vadari Yoganand,
Gopal Shruthi K,
Krishnamurthy Prasad,
Ramarao Manjunath
Publication year - 2017
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/bph.13859
Subject(s) - herg , homomeric , chemistry , activator (genetics) , biophysics , depolarization , hek 293 cells , electrophysiology , pharmacology , stereochemistry , biochemistry , potassium channel , medicine , receptor , biology , protein subunit , gene
Background and Purpose Activators of K v 11.1 (hERG) channels have potential utility in the treatment of acquired and congenital long QT (LQT) syndrome. Here, we describe a new hERG channel activator, 5‐(((1H–indazol‐5‐yl)oxy)methyl)‐N‐(4‐(trifluoromethoxy)phenyl)pyrimidin‐2‐amine (ITP‐2), with a chemical structure distinct from previously reported compounds. Experimental Approach Conventional electrophysiological methods were used to assess the effects of ITP‐2 on hERG1a and hERG1a/1b channels expressed heterologously in HEK‐293 cells. Key Results ITP‐2 selectively increased test pulse currents (EC 50 1.0 μM) and decreased tail currents. ITP‐2 activated hERG1a homomeric channels primarily by causing large depolarizing shifts in the midpoint of voltage‐dependent inactivation and hyperpolarizing shifts in the voltage‐dependence of activation. In addition, ITP‐2 slowed rates of inactivation and made recovery from inactivation faster. hERG1a/1b heteromeric channels showed reduced sensitivity to ITP‐2 and their inactivation properties were differentially modulated. Effects on midpoint of voltage‐dependent inactivation and rates of inactivation were less pronounced for hERG1a/1b channels. Effects on voltage‐dependent activation and activation kinetics were not different from hERG1a channels. Interestingly, hERG1b channels were inhibited by ITP‐2. Inactivation‐impairing mutations abolished activation by ITP‐2 and led to inhibition of hERG channels. ITP‐2 exerted agonistic effect from extracellular side of the membrane and could activate one of the arrhythmia‐associated trafficking‐deficient LQT2 mutants. Conclusions and Implications ITP‐2 may serve as another novel lead molecule for designing robust activators of hERG channels. hERG1a/1b gating kinetics were differentially modulated by ITP‐2 leading to altered sensitivity. ITP‐2 is capable of activating an LQT2 mutant and may be potentially useful in the development of LQT2 therapeutics.