Experimental factors that impact CaV1.2 channel pharmacology-Effects of recording temperature, charge carrier, and quantification of drug effects on the step and ramp currents elicited by the "step-step-ramp" voltage protocol.

Background And Purpose: CaV1.2 channels contribute to action potential upstroke in pacemaker cells, plateau potential in working myocytes, and initiate excitation-contraction coupling. Understanding drug action on CaV1.

Determination of five positive control drugs in hERG external solution (buffer) by LC-MS/MS to support in vitro hERG assay as recommended by ICH S7B.

ICH S7B recommends screening for hERG channel block using patch clamp recordings to assess a drug's proarrhythmic risk. Block of the hERG channel has been associated with clinical QT prolongation as well as the rare, but potentially fatal ventricular tachyarrhythmia Torsade de Pointes (TdP). During recording, drug concentrations perfused to the cells can deviate from nominal concentrations due to molecule-specific properties (such as non-specific binding), thereby introducing error when assessing drug potency.

hERG block potencies for 5 positive control drugs obtained per ICH E14/S7B Q&As best practices: Impact of recording temperature and drug loss.

According to the ICH S7B guideline, drug candidates are screened for hERG block prior to first-in-human testing to predict the likelihood of delayed repolarization associated with a rare, but life-threatening, ventricular tachyarrhythmia. The new ICH E14 Q&As guideline allows hERG results to be used in later clinical development for decision-making (Q&As 5.1 and 6.

Mechanisms of QT prolongation by buprenorphine cannot be explained by direct hERG channel block.

Buprenorphine is a μ-opioid receptor (MOR) partial agonist used to manage pain and addiction. QTC prolongation that crosses the 10 msec threshold of regulatory concern was observed at a supratherapeutic dose in two thorough QT studies for the transdermal buprenorphine product BUTRANS®. Because QTC prolongation can be associated with Torsades de Pointes (TdP), a rare but potentially fatal ventricular arrhythmia, these results have led to further investigation of the electrophysiological effects of buprenorphine.

Bipolar switching by HCN voltage sensor underlies hyperpolarization activation.

Despite sharing a common architecture with archetypal voltage-gated ion channels (VGICs), hyperpolarization- and cAMP-activated ion (HCN) channels open upon hyperpolarization rather than depolarization. The basic motions of the voltage sensor and pore gates are conserved, implying that these domains are inversely coupled in HCN channels. Using structure-guided protein engineering, we systematically assembled an array of mosaic channels that display the full complement of voltage-activation phenotypes observed in the VGIC superfamily.

Minimal molecular determinants of isoform-specific differences in efficacy in the HCN channel family.

Hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels generate rhythmic activity in the heart and brain. Isoform-specific functional differences reflect the specializations required for the various roles that they play. Despite a high sequence and structural similarity, HCN isoforms differ greatly in their response to cyclic nucleotides.

Theory of Inpatient Circadian Care (TICC): A Proposal for a Middle-Range Theory.

The circadian system controls the daily rhythms of a variety of physiological processes. Most organisms show physiological, metabolic and behavioral rhythms that are coupled to environmental signals. In humans, the main synchronizer is the light/dark cycle, although non-photic cues such as food availability, noise, and work schedules are also involved.

The two-pore domain potassium channel KCNK5: induction by estrogen receptor alpha and role in proliferation of breast cancer cells.

The growth of many human breast tumors requires the proliferative effect of estrogen acting via the estrogen receptor α (ERα). ERα signaling is therefore a clinically important target for breast cancer prevention and therapeutics. Although extensively studied, the mechanism by which ERα promotes proliferation remains to be fully established.

Dominant-negative regulation of cell surface expression by a pentapeptide motif at the extreme COOH terminus of an Slo1 calcium-activated potassium channel splice variant.

Large-conductance Ca(2+)-activated K(+) (BK(Ca)) channels regulate the physiology of many cell types. A single vertebrate gene variously known as Slo1, KCa1.1, or KCNMA1 encodes the pore-forming subunits of BK(Ca) channel but is expressed in a potentially very large number of alternative splice variants.

Canonical transient receptor potential channel (TRPC)3 and TRPC6 associate with large-conductance Ca2+-activated K+ (BKCa) channels: role in BKCa trafficking to the surface of cultured podocytes.

Large-conductance (BK(Ca) type) Ca(2+)-activated K(+) channels encoded by the Slo1 gene and various canonical transient receptor potential channels (TRPCs) are coexpressed in many cell types, including podocytes (visceral epithelial cells) of the renal glomerulus. In this study, we show by coimmunoprecipitation and GST pull-down assays that BK(Ca) channels can associate with endogenous TRPC3 and TRPC6 channels in differentiated cells of a podocyte cell line. Both types of TRPC channels colocalize with Slo1 in podocytes and in human embryonic kidney (HEK) 293T cells transiently coexpressing the TRPC channels with Slo1.