An ion channel library for drug discovery and safety screening on automated platforms.

Ion channels represent the third largest class of targets in drug discovery after G-protein coupled receptors and kinases. In spite of this ranking, ion channels continue to be under exploited as drug targets compared with the other two groups for several reasons. First, with 400 ion channel genes and an even greater number of functional channels due to mixing and matching of individual subunits, a systematic collection of ion channel-expressing cell lines for drug discovery and safety screening has not been available.

Cardiac glycosides as novel inhibitors of human ether-a-go-go-related gene channel trafficking.

Direct block of the cardiac potassium channel human ether-a-go-go-related gene (hERG) by a large, structurally diverse group of therapeutic compounds causes drug-induced QT prolongation and torsades de pointes arrhythmias. In addition, several therapeutic compounds have been identified more recently that prolong the QT interval by inhibition of hERG trafficking to the cell surface. We used a surface expression assay to identify novel compounds that interfere with hERG trafficking and found that cardiac glycosides are potent inhibitors of hERG expression at the cell surface.

Antimony-based antileishmanial compounds prolong the cardiac action potential by an increase in cardiac calcium currents.

Antimonial agents are a mainstay for the treatment of leishmaniasis, a group of protozoal diseases that includes visceral leishmaniasis, or Kala Azar. Chemotherapy with trivalent potassium antimony tartrate (PAT) and, more importantly, pentavalent antimony-carbohydrate complexes, such as sodium stibogluconate (SSG), has been reported to prolong the QT interval and produce life-threatening arrhythmias. PAT is chemically related to As2O3, which alters cardiac excitability by inhibition of human ether a-go-go related gene (hERG) trafficking and an increase of cardiac calcium currents.

HERG channel trafficking.

Mutations in the cardiac potassium channel hERG/IKr cause inherited long QT syndrome with increased susceptibility to ventricular arrhythmias. Several mutations in hERG produce trafficking-deficient channels that are retained in the endoplasmic reticulum (ER). Surface expression of certain mutations (i.

HERG-Lite: a novel comprehensive high-throughput screen for drug-induced hERG risk.

Introduction: Direct block of I(Kr) by non-antiarrhythmic drugs (NARDs) is a major cause of QT prolongation and torsades de pointes (TdP), and has made the hERG potassium channel a major target of drug safety programs in cardiotoxicity. Block of hERG currents is not the only way that drugs can adversely impact the repolarizing current I(Kr), however. We have shown recently that two drugs in clinical use do not block hERG but produce long QT syndrome (LQTS) and TdP by inhibiting trafficking of hERG to the cell surface.

Pentamidine-induced long QT syndrome and block of hERG trafficking.

The diamidine pentamidine is used to treat leishmaniasis, trypanosomiasis, and Pneumocystis carinii pneumonia. Treatment may be accompanied by prolongation of the QT interval of the electrocardiogram and torsades de pointes tachycardias. Up to now, it has been thought that therapeutic compounds causing QT prolongation are associated with direct block of the cardiac potassium channel human ether a-go-go-related gene (hERG), which encodes the alpha subunit of cardiac I(Kr) currents.

Mechanisms of arsenic-induced prolongation of cardiac repolarization.

Arsenic trioxide (As(2)O(3)) produces dramatic remissions in patients with relapsed or refractory acute promyelocytic leukemia. Its clinical use is burdened by QT prolongation, torsade de pointes, and sudden cardiac death. In the present study, we analyzed the molecular mechanisms leading to As(2)O(3)-induced abnormalities of cardiac electrophysiology.

Inhibition of cardiac HERG currents by the DNA topoisomerase II inhibitor amsacrine: mode of action.

1 The topoisomerase II inhibitor amsacrine is used in the treatment of acute myelogenous leukemia. Although most anticancer drugs are believed not to cause acquired long QT syndrome (LQTS), concerns have been raised by reports of QT interval prolongation, ventricular fibrillation and death associated with amsacrine treatment. Since blockade of cardiac human ether-a-go-go-related gene (HERG) potassium currents is an important cause of acquired LQTS, we investigated the acute effects of amsacrine on cloned HERG channels to determine the electrophysiological basis for its proarrhythmic potential.

Fas activation induces renal tubular epithelial cell beta 8 integrin expression and function in the absence of apoptosis.

Cell fate following Fas (CD95) ligand or agonistic anti-Fas antibody stimulation is determined by multiple factors, including Fas expression level, microdomain localization, and modulating cytokines. Highly expressed Fas clusters and activates a canonical apoptosis signaling pathway. In less susceptible cells, Fas transduces apoptosis-independent signals, which are not well defined, but have been linked to inflammation, angiogenesis, and fibrosis.

Protein kinase A-mediated phosphorylation of HERG potassium channels in a human cell line.

Objective: To investigate the molecular mechanism of human ether-a-go-go-related gene (HERG) potassium channels regulated by protein kinase A (PKA) in a human cell line.

Methods: HERG channels were stably expressed in human embryonic kidney (HEK) 293 cells, and currents were measured with the patch clamp technique. The direct phosphorylation of HERG channel proteins expressed heterologously in Xenopus laevis oocytes was examined by (32)P labeling and immunoprecipitation with an anti-HERG antibody.

Potassium channels Kv1.1, Kv1.2 and Kv1.6 influence excitability of rat visceral sensory neurons.

Voltage-gated potassium channels, Kv1.1, Kv1.2 and Kv1.

Increased K+ efflux and apoptosis induced by the potassium channel modulatory protein KChAP/PIAS3beta in prostate cancer cells.

K(+) channel-associated protein/protein inhibitor of activated STAT (KChAP/PIAS3beta) is a potassium (K(+)) channel modulatory protein that boosts protein expression of a subset of K(+) channels and increases currents without affecting gating. Since increased K(+) efflux is an early event in apoptosis, we speculated that KChAP might induce apoptosis through its up-regulation of K(+) channel expression. KChAP belongs to the protein inhibitor of activated STAT family, members of which also interact with a variety of transcription factors including the proapoptotic protein, p53.