Inwardly rectifying potassium (Kir) channels are key regulators of diverse physiological processes and may represent novel drug targets for diseases. Their therapeutic potential has not been tested directly, however, due to the lack of drug-like compounds targeting inward rectifiers. The lack of selective "probes" has also hindered efforts to define the physiological functions of some Kir channels. To overcome this formidable barrier and create new opportunities for studying inward rectifier physiology, the investigators performed a high- throughput screen (HTS) of more than 200,000 compounds for small-molecule modulators of ROMK (Kir1.1), a putative target for a novel class of diuretic. One compound, termed VU590, inhibits ROMK at nanomolar concentrations and Kir7.1 in the low micromolar range, making it the first small-molecule inhibitor of both channels. The investigators went on to use medicinal chemistry to rationally design a nanomolar-affinity probe, termed VU591, which is highly selective for ROMK over more than 60 potential off targets, including inward rectifiers and BK channels.
In Aim 1, the investigators will employ state-of-the-art molecular modeling techniques, atomic structure-guided mutagenesis and electrophysiology to define the VU590/591 binding sites in ROMK and Kir7.1. VU591 is remarkably selective for ROMK and therefore represents a promising candidate for further development for use in animal studies.
In Aim 2, the investigators will first determine if VU591 is active in the native tissue by assessing its effects on K and Na transport in isolated perfused cortical collecting ducts under low- and high-flow conditions. The investigators also discovered a nanomolar-affinity inhibitor of a G-protein regulated inward rectifier (GIRK), a putative therapeutic target for atrial fibrillation.
In Aim 3, the investigators will use medicinal chemistry, structure-guided mutagenesis and electrophysiology to define the molecular binding sites for this novel compound termed VU592. These studies will provide important new insights into the atomic structures of inward rectifiers and generate critically needed probes with which to define the integrative physiology and therapeutic potential of these channels. Lay summary: The investigators will combine medicinal chemistry, advanced computational techniques and classical physiological methods to develop drug-like compounds targeting potassium channels that could be therapeutic targets for hypertension, edema and cardiac arrhythmia.

Public Health Relevance

Inward rectifying potassium (Kir) channels play key physiological roles in diverse cellular functions and may represent novel drug targets. However, the lack of selective pharmacological probes has hindered efforts to explore the integrative physiology and therapeutic potential of most Kir channels. Here we propose to employ medicinal chemistry, atomic structure-guided mutagenesis, kidney tubule microperfusion and electrophysiology to develop the small-molecule pharmacology for Kir1.1, Kir7.1 and Kir3 channels. NARRATIVE Inward rectifying potassium (Kir) channels play key physiological roles in diverse cellular functions and may represent novel drug targets. However, the lack of selective pharmacological probes has hindered efforts to explore the integrative physiology and therapeutic potential of most Kir channels. Here we propose to employ medicinal chemistry, atomic structure-guided mutagenesis, kidney tubule microperfusion and electrophysiology to develop the small-molecule pharmacology for Kir1.1, Kir7.1 and Kir3 channels.

Agency
National Institute of Health (NIH)
Type
Research Project (R01)
Project #
5R01DK082884-05
Application #
8723159
Study Section
Cellular and Molecular Biology of the Kidney Study Section (CMBK)
Program Officer
Ketchum, Christian J
Project Start
Project End
Budget Start
Budget End
Support Year
5
Fiscal Year
2014
Total Cost
Indirect Cost
Name
Vanderbilt University Medical Center
Department
Anesthesiology
Type
Schools of Medicine
DUNS #
City
Nashville
State
TN
Country
United States
Zip Code
37212
Swale, Daniel R; Kharade, Sujay V; Denton, Jerod S (2014) Cardiac and renal inward rectifier potassium channel pharmacology: emerging tools for integrative physiology and therapeutics. Curr Opin Pharmacol 15:7-15
Denton, Jerod S (2014) Druggability of the inward rectifier family: a hope for rare channelopathies? Future Med Chem 6:971-3
Raphemot, Rene; Rouhier, Matthew F; Swale, Daniel R et al. (2014) Discovery and characterization of a potent and selective inhibitor of Aedes aegypti inward rectifier potassium channels. PLoS One 9:e110772
Rouhier, Matthew F; Hine, Rebecca M; Park, Seokhwan Terry et al. (2014) Excretion of NaCl and KCl loads in mosquitoes. 2. Effects of the small molecule Kir channel modulator VU573 and its inactive analog VU342. Am J Physiol Regul Integr Comp Physiol 307:R850-61
Raphemot, Rene; Estévez-Lao, Tania Y; Rouhier, Matthew F et al. (2014) Molecular and functional characterization of Anopheles gambiae inward rectifier potassium (Kir1) channels: a novel role in egg production. Insect Biochem Mol Biol 51:10-9
Rouhier, Matthew F; Raphemot, Rene; Denton, Jerod S et al. (2014) Pharmacological validation of an inward-rectifier potassium (Kir) channel as an insecticide target in the yellow fever mosquito Aedes aegypti. PLoS One 9:e100700
Raphemot, Rene; Swale, Daniel R; Dadi, Prasanna K et al. (2014) Direct activation of ?-cell KATP channels with a novel xanthine derivative. Mol Pharmacol 85:858-65
Raphemot, Rene; Weaver, C David; Denton, Jerod S (2013) High-throughput screening for small-molecule modulators of inward rectifier potassium channels. J Vis Exp :
Kaufmann, Kristian; Romaine, Ian; Days, Emily et al. (2013) ML297 (VU0456810), the first potent and selective activator of the GIRK potassium channel, displays antiepileptic properties in mice. ACS Chem Neurosci 4:1278-86
Denton, Jerod S; Pao, Alan C; Maduke, Merritt (2013) Novel diuretic targets. Am J Physiol Renal Physiol 305:F931-42

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