Human Ether Research Articles

Optimizing drug-like properties of selective butyrylcholinesterase inhibitors for cognitive improvement: Enhancing aqueous solubility by disrupting molecular plane

Most recently, worldwide interest in butyrylcholinesterase (BChE) as a potential target for treating Alzheimer's disease (AD) has increased. In this study, the previously obtained selective BChE inhibitors with benzimidazole-oxadiazole scaffold were further structurally modified to increase their aqueous solubility and pharmacokinetic (PK) characteristics. S16–1029 showed improved solubility (3280 μM, upgraded by 14 times) and PK parameters, including plasma exposure (AUC0-inf = 1729.95 ng/mL*h, upgraded by 2.6 times) and oral bioavailability (Fpo = 48.18%, upgraded by 2 times). S16–1029 also displayed weak or no inhibition against Cytochrome P450 (CYP450) and human ether a-go-go related gene (hERG) potassium channel. In vivo experiments on tissue distribution revealed that S16–1029 could cross the blood-brain barrier (BBB) and reach the central nervous system (CNS). In vivo cognitive improvement efficacy and good in vitro target inhibitory activity (eqBChE IC50 = 11.35 ± 4.84 nM, hBChE IC50 = 48.1 ± 11.4 nM) were also assured. The neuroprotective effects against several AD pathology characteristics allowed S16–1029 to successfully protect the CNS of progressed AD patients. According to the findings of this study, altering molecular planarity might be a viable strategy for improving the drug-like property of CNS-treating drugs.

Blocking xCT and PI3K/Akt pathway synergized with DNA damage of Riluzole-Pt(IV) prodrugs for cancer treatment

Cancer treatment requires the participation of multiple targets/pathways, and single approach is hard to effectively curb the proliferation and metastasis of carcinoma cells. In this work, we conjugated FDA-approved riluzole and platinum(II) drugs into a series of unreported riluzole-Pt(IV) compounds, which were designed to simultaneously target DNA, the solute carrier family 7 member 11 (SLC7A11, xCT), and the human ether a go-go related gene 1 (hERG1), to exert synergistic anticancer effect. Among them, c,c,t-[PtCl2(NH3)2(OH)(glutarylriluzole)] (compound 2) displayed excellent antiproliferative activity with IC50 value of 300-times lower than that of cisplatin in HCT-116, and optimal selectivity index between carcinoma and human normal liver cells (LO2). Mechanism studies indicated that compound 2 released riluzole and active Pt(II) species after entering cells to exhibit a prodrug behavior against cancer, which obviously increased DNA-damage and cell apoptosis, as well as suppressed metastasis in HCT-116. Compound 2 persisted in the xCT-target of riluzole and blocked the biosynthesis of glutathione (GSH) to trigger oxidative stress, which could boost the killing to cancer cells and reduce Pt-drug resistance. Meanwhile, compound 2 significantly inhibited invasion and metastasis of HCT-116 cells by targeting hERG1 to interrupt the phosphorylation of phosphatidylinositide 3-kinases/proteinserine-threonine kinase (PI3K/Akt), and reverse epithelial-mesenchymal transformation (EMT). Based on our results, the riluzole-Pt(IV) prodrugs studied in this work could be regarded as a new class of very promising candidates for cancer treatment compared to traditional platinum drugs.

Reclassification of a likely pathogenic Dutch founder variant in KCNH2; implications of reduced penetrance.

Variants in KCNH2, encoding the human ether a-go-go (hERG) channel that is responsible for the rapid component of the cardiac delayed rectifier K+ current (IKr), are causal to long QT syndrome type 2 (LQTS2). We identified eight index patients with a new variant of unknown significance (VUS), KCNH2:c.2717C > T:p.(Ser906Leu). We aimed to elucidate the biophysiological effect of this variant, to enable reclassification and consequent clinical decision-making. A genotype-phenotype overview of the patients and relatives was created. The biophysiological effects were assessed independently by manual-, and automated calibrated patch clamp. HEK293a cells expressing (i) wild-type (WT) KCNH2, (ii) KCNH2-p.S906L alone (homozygous, Hm) or (iii) KCNH2-p.S906L in combination with WT (1:1) (heterozygous, Hz) were used for manual patching. Automated patch clamp measured the variants function against known benign and pathogenic variants, using Flp-In T-rex HEK293 KCNH2-variant cell lines. Incomplete penetrance of LQTS2 in KCNH2:p.(Ser906Leu) carriers was observed. In addition, some patients were heterozygous for other VUSs in CACNA1C, PKP2, RYR2 or AKAP9. The phenotype of carriers of KCNH2:p.(Ser906Leu) ranged from asymptomatic to life-threatening arrhythmic events. Manual patch clamp showed a reduced current density by 69.8 and 60.4% in KCNH2-p.S906L-Hm and KCNH2-p.S906L-Hz, respectively. The time constant of activation was significantly increased with 80.1% in KCNH2-p.S906L-Hm compared with KCNH2-WT. Assessment of KCNH2-p.S906L-Hz by calibrated automatic patch clamp assay showed a reduction in current density by 35.6%. The reduced current density in the KCNH2-p.S906L-Hz indicates a moderate loss-of-function. Combined with the reduced penetrance and variable phenotype, we conclude that KCNH2:p.(Ser906Leu) is a low penetrant likely pathogenic variant for LQTS2.

Intracellular hemin is a potent inhibitor of the voltage-gated potassium channel Kv10.1

Heme, an iron-protoporphyrin IX complex, is a cofactor bound to various hemoproteins and supports a broad range of functions, such as electron transfer, oxygen transport, signal transduction, and drug metabolism. In recent years, there has been a growing recognition of heme as a non-genomic modulator of ion channel functions. Here, we show that intracellular free heme and hemin modulate human ether à go-go (hEAG1, Kv10.1) voltage-gated potassium channels. Application of hemin to the intracellular side potently inhibits Kv10.1 channels with an IC50 of about 4 nM under ambient and 63 nM under reducing conditions in a weakly voltage-dependent manner, favoring inhibition at resting potential. Functional studies on channel mutants and biochemical analysis of synthetic and recombinant channel fragments identified a heme-binding motif CxHx8H in the C-linker region of the Kv10.1 C terminus, with cysteine 541 and histidines 543 and 552 being important for hemin binding. Binding of hemin to the C linker may induce a conformational constraint that interferes with channel gating. Our results demonstrate that heme and hemin are endogenous modulators of Kv10.1 channels and could be exploited to modulate Kv10.1-mediated cellular functions.

Role of gamma radiation on functional expression of the voltage-gated potassium channel Kv10.1 and its importance in the radiobiological response

Exposure of biological systems to a radiation absorbed dose produces early and late radiogenic responses, such as ion channel modulation, oxidative stress, cell migration enhancement, and metabolic changes that could impact the efficiency of radiotherapy. To understand how radiation modulates ion channels, we irradiated HEK cells stably expressing the human ether à-go-go potassium channel-1 with gamma photons in the dose range of 2–10 Gy (60Co, 0.2 Gy/min) and measured ionic currents generated by the channel. The importance of the Kv10.1 modulation by gamma radiation was studied using cell proliferation. Results showed that a radiation-absorbed dose of 4 Gy significantly reduced the Kv10.1-evoked currents by depolarizing pulses between −100 mV and +50 mV. Additionally, the expression of Kv10.1 positively modulates HEK293 proliferation and, certainly, prevents the effect of gamma radiation on this phenomenon. Results allow concluding that the modulation of the functional expression of the Kv10.1 channel, induced by gamma radiation, leads to the expression of a radioresistant phenotype in Kv10.1 expressing cells.

Synthesis and Evaluation of Novel Tetrahydronaphthyridine CXCR4 Antagonists with Improved Drug-like Profiles.

Our first-generation CXCR4 antagonist TIQ15 was rationally modified to improve drug-like properties. Introducing a nitrogen atom into the aromatic portion of the tetrahydroisoquinoline ring led to several heterocyclic variants including the 5,6,7,8-tetrahydro-1,6-naphthyridine series, greatly reducing the inhibition of the CYP 2D6 enzyme. Compound 12a demonstrated the best overall properties after profiling a series of isomeric tetrahydronaphthyridine analogues in a battery of biochemical assays including CXCR4 antagonism, CYP 2D6 inhibition, metabolic stability, and permeability. The butyl amine side chain of 12a was substituted with various lipophilic groups to improve the permeability. These efforts culminated in the discovery of compound 30 as a potent CXCR4 antagonist (IC50 = 24 nM) with diminished CYP 2D6 activity, improved PAMPA permeability (309 nm/s), potent inhibition of human immunodeficiency virus entry (IC50 = 7 nM), a cleaner off-target in vitro safety profile, lower human ether a-go-go-related gene channel activity, and higher oral bioavailability in mice (% FPO = 27) compared to AMD11070 and TIQ15.

Synthesis and biological evaluation of 2-benzylaminoquinazolin-4(3H)-one derivatives as a potential treatment for SARS-CoV-2.

Despite the continuing global crisis caused by coronavirus disease 2019 (COVID‐19), there is still no effective treatment. Therefore, we designed and synthesized a novel series of 2‐benzylaminoquinazolin‐4(3H)‐one derivatives and demonstrated that they are effective against SARS‐CoV‐2. Among the synthesized derivatives, 7‐chloro‐2‐(((4‐chlorophenyl)(phenyl)methyl)amino)quinazolin‐4(3H)‐one (Compound 39) showed highest anti‐SARS‐CoV‐2 activity, with a half‐maximal inhibitory concentration value greater than that of remdesivir (IC50 = 4.2 μM vs. 7.6 μM, respectively), which gained urgent approval from the U.S. Food and Drug Administration. In addition, Compound 39 showed good results in various assays measuring metabolic stability, human ether a‐go‐go, Cytochromes P450 (CYPs) inhibition, and plasma protein binding (PPB), and showed better solubility and pharmacokinetics than our previous work.

Intracellular uptake of agents that block the hERG channel can confound the assessment of QT interval prolongation and arrhythmic risk.

Oliceridine is a biased ligand at the μ-opioid receptor recently approved for the treatment of acute pain. In a thorough QT study, corrected QT (QTc) prolongation displayed peaks at 2.5 and 60 minutes after a supratherapeutic dose. The mean plasma concentration peaked at 5 minutes, declining rapidly thereafter. The purpose of this study was to examine the basis for the delayed effect of oliceridine to prolong the QTc interval. Repolarization parameters and tissue accumulation of oliceridine were evaluated in rabbit left ventricular wedge preparations over a period of 5 hours. The effects of oliceridine on ion channel currents were evaluated in human embryonic kidney and Chinese hamster ovary cells. Quinidine was used as a control. Oliceridine and quinidine produced a progressive prolongation of the QTc interval and action potential duration over a period of 5 hours, paralleling slow progressive tissue uptake of the drugs. Oliceridine caused modest prolongation of these parameters, whereas quinidine produced a prominent prolongation of action potential duration and QTc interval as well as development of early afterdepolarization (after 2 hours), resulting in a high torsades de pointes score. The 50% inhibitory concentration values for the oliceridine inhibition of the rapidly activating delayed rectifier current (human ether a-go-go current) and late sodium channel current were 2.2 and 3.45 μM when assessed after traditional acute exposure but much lower after 3 hours of drug exposure. Our findings suggest that a gradual increase of intracellular access of drugs to the hERG channels as a result of their intracellular uptake and accumulation can significantly delay effects on repolarization, thus confounding the assessment of QT interval prolongation and arrhythmic risk when studied acutely. The multi-ion channel effects of oliceridine, late sodium channel current inhibition in particular, point to a low risk of devloping torsades de pointes.

Investigation of the Inactivation of HERG using Molecular Dynamics Simulations of New cryo-EM Structures

The human ether á-go-go related gene (hERG) encodes the delayed rectifier potassium channel (Kv11.1), best known for mediation of the repolarising current in the cardiac action potential. Loss of function of hERG can lead to long QT-syndrome which causes cardiac arrhythmias and sudden cardiac arrest. hERG is susceptible to a wide range of drugs which can lead to drug induced long QT-syndrome. Here, the recent cryo-EM structure of hERG in an activated state, together with newly-solved structures that are open or inactivated serve as the basis to investigate the structural determinants of hERG inactivation. We used molecular dynamics flexible fitting to refine and relax these new structures in micelles consisting of detergents, lipids and cholesterol. A combination of long simulations and libraries of short simulations were performed with a variety of ion concentrations to study different conformational states. These simulations highlighted the amino acids important for maintaining each state of the selectivity filter and therefore may be involved in hERG inactivation. Furthermore, we have used replica exchange with solute tempering to enhance sampling of the exchange of ions in the hERG selectivity filter. We observe correlations between channel conformation and ion occupancy that shed light on the coupling of ions to inactivation. Together with mutagenesis experiments, these simulations provide molecular-level understanding of hERG inactivation, with considerable clinical and pharmacological potential.

Safety pharmacology of self-assembled-micelle inhibitory RNA-targeting amphiregulin (SAMiRNA-AREG), a novel siRNA nanoparticle platform.

The present safety pharmacology core battery studies (neurobehavior, respiratory, cardiovascular system, and human ether a-go-go (hERG) channel current) investigated the potential harmful effects of self-assembled-micelle inhibitory RNA-targeting amphiregulin (SAMiRNA-AREG). The SAMiRNA-AREG was administered by single intravenous injection at up to 300 mg/kg and 100 mg/kg in mice and monkeys, respectively. The hERG assay was performed in Chinese hamster ovary (CHO) cells at SAMiRNA-AREG concentrations of up to 200 μg/mL. In the evaluation on neurobehavior, a transient decrease in body temperature was found at 0.5 h (30 min) post-dose at both sexes in mice, with a single 300 mg/kg dose of SAMiRNA-AREG. However, these effects had returned to normal at 1 h post-dose. In the evaluation on hERG channel current, there were statistically significant differences in the inhibition of peak hERG potassium channel current between the 20, 100, and 200 μg/mL SAMiRNA-AREG treatment groups and the vehicle control group. However, these effects were less potent than that of E-4031, a positive control article. For the respiratory and cardiovascular systems, no treatment-related changes were observed in mice or monkeys. Thus, under these experimental conditions, these studies suggest that SAMiRNA-AREG showed no adverse effects on the neurobehavior, respiratory, and cardiovascular function.

Antioxidant potential of flavonoid glycosides from Manniophyton fulvum Müll. (Euphorbiaceae): Identification and molecular modeling

Chemical investigation of the leaves of Manniophyton fulvum led to the isolation of seven flavonoid glycosides: myricetin-3-O-β-Dd-rhamnoside (1), kaempferol-3-O-β-d-rhamnoside (2), quercetin-3-O-β-d-glucoside (3), quercetin-3-O-β-d-rhamnoside (4), quercetin-3-O-β-d-galactoside (5), rutin (6) and quercetin (7). The structures of the compounds were established by spectroscopic analyses as well as by comparison with published data. Some of the compounds showed strong antioxidant activity which validates the traditional use of the plant. An attempted correlation between the computed HOMO-LUMO energies and the measured antioxidant activities was established. We have also estimated the cardiotoxicity of the compounds by calculating the predicted logarithm of the human Ether-`a-go-go Related Gene (loghERG) using the QikProp program. These purified flavonoids are new potential lead compounds for the development of antioxidant drugs.

Nonclinical Safety Assessment of Zanubrutinib: A Novel Irreversible BTK Inhibitor.

Zanubrutinib an oral irreversible Bruton's tyrosine kinase (BTK) inhibitor, is under development for the treatment of a variety of B-cell malignancies and has received accelerated approval by the US Food and Drug Administration for treatment of adult patients with mantel cell lymphoma who have received at least one prior therapy. Zanubrutinib moderately inhibited the human ether- à -go-go-related gene channel with half maximal inhibition concentration (IC50) of 9.11 µM and showed neither effects on the cardiovascular system functions in telemetry-implanted dogs nor on the respiratory and central nervous system functions in rats. No toxicologically significant changes were noted in rats and dogs at the systemic exposure ratios (area under the curve ratio between animals and humans at the therapeutic dose) up to 26- and 15-fold for 26-weeks and 39-weeks of treatment, respectively. Zanubrutinib was not genotoxic. Fertility studies showed no abnormal findings in both male and female rats at the systemic exposure ratios of up to 12-fold; embryo-fetal studies showed no fetal lethality or teratogenicity in rabbit or rat fetuses at the systemic exposure ratios of up to 25- and 16-fold, respectively, except for 0.3% to 1.5% of 2 or 3 chambered hearts in rat fetuses; pre- and postnatal developmental toxicity showed no effects in rats at the systemic exposure ratios up to 16-fold except for an increased incidence (26% to 42%) and severity of various ophthalmic lesions in treated groups compared to the concurrent control group (26%). These nonclinical study results suggest that zanubrutinib has a broad safety window and an optimal safety profile while treating patients with advanced cancers.

Fentanyl-Induced Block of hERG Channels Is Exacerbated by Hypoxia, Hypokalemia, Alkalosis, and the Presence of hERG1b.

Human ether-a-go-go-related gene (hERG) encodes the pore-forming subunit of the rapidly activating delayed rectifier potassium current (IKr) important for repolarization of cardiac action potentials. Drug-induced disruption of hERG channel function is a main cause of acquired long QT syndrome, which can lead to ventricular arrhythmias and sudden death. Illicit fentanyl use is associated with sudden death. We have demonstrated that fentanyl blocks hERG current (IhERG) at concentrations that overlap with the upper range of postmortem blood concentrations in fentanyl-related deaths. Since fentanyl can cause respiratory depression and electrolyte imbalances, in the present study we investigated whether certain pathologic circumstances exacerbate fentanyl-induced block of IhERG Our results show that chronic hypoxia or hypokalemia additively reduced IhERG with fentanyl. As well, high pH potentiated the fentanyl-mediated block of hERG channels, with an IC50 at pH 8.4 being 7-fold lower than that at pH 7.4. Furthermore, although the full-length hERG variant, hERG1a, has been widely used to study hERG channels, coexpression with the short variant, hERG1b (which does not produce current when expressed alone), produces functional hERG1a/1b channels, which gate more closely resembling native IKr Our results showed that fentanyl blocked hERG1a/1b channels with a 3-fold greater potency than hERG1a channels. Thus, in addition to a greater susceptibility due to the presence of hERG1b in the human heart, hERG channel block by fentanyl can be exacerbated by certain conditions, such as hypoxia, hypokalemia, or alkalosis, which may increase the risk of fentanyl-induced ventricular arrhythmias and sudden death. SIGNIFICANCE STATEMENT: This work demonstrates that heterologously expressed human ether a-go-go-related gene (hERG) 1a/1b channels, which more closely resemble rapidly activating delayed rectifier potassium current in the human heart, are blocked by fentanyl with a 3-fold greater potency than the previously studied hERG1a expressed alone. Additionally, chronic hypoxia, hypokalemia, and alkalosis can increase the block of hERG current by fentanyl, potentially increasing the risk of cardiac arrhythmias and sudden death.

AKAP5 anchors PKA to enhance regulation of the HERG channel

The activation of the β-adrenergic receptor (β-AR) regulates the human ether a-go-go-related gene (HERG) channel via protein kinase A (PKA), which in turn induces lethal arrhythmia in patients with long QT syndromes (LQTS). However, the role of A-kinase anchoring proteins (AKAPs) in PKA's regulation of the HERG channel and its molecular mechanism are not clear. Here, HEK293 cells were transfected with the HERG gene alone or co-transfected with HERG and AKAP5 using Lipofectamine 2000. Western blotting was performed to determine HERG protein expression, and immunofluorescence and immunoprecipitation were used to assess the binding and cellular colocalization of HERG, AKAP5, and PKA. The HEK293-HERG and HEK293-HERG + AKAP5 cells were treated with forskolin at different concentrations and different time. HERG protein expression significantly increased under all treatment conditions (P < 0.001). The level of HERG protein expression in HEK293-HERG + AKAP5 cells was higher than that observed in HEK293-HERG cells (P < 0.001). Immunofluorescence and immunoprecipitation indicated that HERG bound to PKA and AKAP5 and was colocalized at the cell membrane. The HERG channel protein, AKAP5, and PKA interacted with each other and appeared to form intracellular complexes. These results provide evidence for a novel mechanism which AKAP5 anchors PKA to up-regulate the HERG channel protein.

Transmural and rate-dependent profiling of drug-induced arrhythmogenic risks through in silico simulations of multichannel pharmacology

In vitro human ether-à-go-go related gene (hERG) inhibition assay alone might provide insufficient information to discriminate “safe” from “dangerous” drugs. Here, effects of multichannel inhibition on cardiac electrophysiology were investigated using a family of cardiac cell models (Purkinje (P), endocardial (Endo), mid-myocardial (M) and epicardial (Epi)). We found that: (1) QT prolongation alone might not necessarily lead to early afterdepolarization (EAD) events, and it might be insufficient to predict arrhythmogenic liability; (2) the occurrence and onset of EAD events could be a candidate biomarker of drug-induced arrhythmogenicity; (3) M cells are more vulnerable to drug-induced arrhythmias, and can develop early afterdepolarization (EAD) at slower pacing rates; (4) the application of quinidine can cause EADs in all cell types, while INaL is the major depolarizing current during the generation of drug-induced EAD in P cells, ICaL is mostly responsible in other cell types; (5) drug-induced action potential (AP) alternans with beat-to-beat variations occur at high pacing rates in P cells. These results suggested that quantitative profiling of transmural and rate-dependent properties can be essential to evaluate drug-induced arrhythmogenic risks, and may provide mechanistic insights into drug-induced arrhythmias.

Superparamagnetic iron oxide nanoparticles (SPIONs) modulate hERG ion channel activity

Superparamagnetic iron oxide nanoparticles (SPIONs) are widely used in various biomedical applications, such as diagnostic agents in magnetic resonance imaging (MRI), for drug delivery vehicles and in hyperthermia treatment of tumors. Although the potential benefits of SPIONs are considerable, there is a distinct need to identify any potential cellular damage associated with their use. Since human ether à go-go-related gene (hERG) channel, a protein involved in the repolarization phase of cardiac action potential, is considered one of the main targets in the drug discovery process, we decided to evaluate the effects of SPIONs on hERG channel activity and to determine whether the oxidation state, the dimensions and the coating of nanoparticles (NPs) can influence the interaction with hERG channel. Using patch clamp recordings, we found that SPIONs inhibit hERG current and this effect depends on the coating of NPs. In particular, SPIONs with covalent coating aminopropylphosphonic acid (APPA) have a milder effect on hERG activity. We observed that the time-course of hERG channel modulation by SPIONs is biphasic, with a transient increase (∼20% of the amplitude) occurring within the first 1–3 min of perfusion of NPs, followed by a slower inhibition. Moreover, in the presence of SPIONs, deactivation kinetics accelerated and the activation and inactivation I–V curves were right-shifted, similarly to the effect described for the binding of other divalent metal ions (e.g. Cd2+ and Zn2+). Finally, our data show that a bigger size and the complete oxidation of SPIONs can significantly decrease hERG channel inhibition. Taken together, these results support the view that Fe2+ ions released from magnetite NPs may represent a cardiac risk factor, since they alter hERG gating and these alterations could compromise the cardiac action potential.

HERG1 promotes esophageal squamous cell carcinoma growth and metastasis through TXNDC5 by activating the PI3K/AKT pathway

BackgroundThe human ether a-go-go-related gene 1 (HERG1) is involved in tumor progression; however, its role in esophageal squamous cell carcinoma (ESCC) is not well studied. This study investigated HERG1 function in ESCC progression and elucidated the underlying mechanisms.MethodsThe prognostic value of HERG1 was determined by immunohistochemistry in ESCC biopsies. Cell growth and proliferation were analyzed by colony formation and methyl thiazolyl tetrazolium assays. Cell migration and invasion were analyzed by wound healing and Boyden transwell assays. Epithelial-mesenchymal transition (EMT) was evaluated by immunoblotting and quantitative polymerase chain reaction (qPCR). A xenograft mouse model was used to validate the tumorigenic and metastatic roles of HERG1 in vivo.ResultsHERG1 expression was overall higher in ESCC tissues compared to adjacent non-tumor tissues. A retrospective analysis of 349 patients with ESCC (stages I–IV) confirmed increased HERG1 expression was associated with disease progression and higher mortality rate. The overall survival of the patients was significantly worse when their tumors displayed higher HERG1 expression. HERG1 knockdown reduced tumor growth and metastasis in athymic mice. HERG1 affected the proliferation, migration, and invasion of two ESCC cell lines (TE-1 and KYSE-30). Changes in HERG1 expression affected the expression of cell cycle- and EMT-related proteins; these effects were reversed by altering the expression of thioredoxin domain-containing protein 5 (TXNDC5), which is also associated with the clinicopathological characteristics of patients with ESCC and is relevant to HERG1 in pathological biopsies. Additionally, HERG1 expression altered phosphoinositide 3-kinase (PI3K) and AKT phosphorylation, thereby affecting TXNDC5 expression.ConclusionsHERG1 contributes to poor prognosis in patients with ESCC by promoting ESCC cell proliferation, migration, and invasion via TXNDC5 through the PI3K/AKT signaling pathway. Our findings provided novel insights into the pathology of ESCC and role of HERG1 in tumor progression, suggesting that targeting HERG1 has potential diagnostic and therapeutic value for ESCC treatment.

Molecular Docking Guided Grid-Independent Descriptor Analysis to Probe the Impact of Water Molecules on Conformational Changes of hERG Inhibitors in Drug Trapping Phenomenon.

Human ether a-go-go related gene (hERG) or KV11.1 potassium channels mediate the rapid delayed rectifier current (IKr) in cardiac myocytes. Drug-induced inhibition of hERG channels has been implicated in the development of acquired long QT syndrome type (aLQTS) and fatal arrhythmias. Several marketed drugs have been withdrawn for this reason. Therefore, there is considerable interest in developing better tests for predicting drugs which can block the hERG channel. The drug-binding pocket in hERG channels, which lies below the selectivity filter, normally contains K+ ions and water molecules. In this study, we test the hypothesis that these water molecules impact drug binding to hERG. We developed 3D QSAR models based on alignment independent descriptors (GRIND) using docked ligands in open and closed conformations of hERG in the presence (solvated) and absence (non-solvated) of water molecules. The ligand–protein interaction fingerprints (PLIF) scheme was used to summarize and compare the interactions. All models delineated similar 3D hERG binding features, however, small deviations of about ~0.4 Å were observed between important hotspots of molecular interaction fields (MIFs) between solvated and non-solvated hERG models. These small changes in conformations do not affect the performance and predictive power of the model to any significant extent. The model that exhibits the best statistical values was attained with a cryo_EM structure of the hERG channel in open state without water. This model also showed the best R2 of 0.58 and 0.51 for the internal and external validation test sets respectively. Our results suggest that the inclusion of water molecules during the docking process has little effect on conformations and this conformational change does not impact the predictive ability of the 3D QSAR models.

Downregulation of Herg1 suppresses osteosarcoma proliferation and invasion by targeting Hippo signaling pathway

Objective: To detect the effect and regulatory mechanism of human ether à go-go related gene 1 (Herg 1) knockdown on the proliferation and invasion of osteosarcoma (OS). Methods: We constructed a recombinant adenovirus vector (Ad5-Herg1-shRNA) expressing short hair RNA (shRNA) against Herg1 and tested the knockdown efficiency. Then, the effects of Herg 1 knockdown on the proliferation, growth and invasion of osteosarcoma were measured by using cell counting kit-8 (CCK-8), wound healing assay, Transwell assay and xenograft model of nude mice, respectively. Tandem affinity purification, mass spectrometry and dual luciferase reporter assay were used to find out the molecules interacted with Herg1. Western blot was used to detect the expressions of large tumor suppressor gene (LATS1), p-LATS1, Yes-associated protein (YAP) and p-YAP in cells after infection of Ad5-Herg1-shRNA. Results: Compared to Ad5-control-shRNA, Ad5-Herg1-shRNA dramatically inhibited the expression of Herg1 in OS cells. The result of CCK8 array demonstrated that 143B cell vitalities of Ad5-Herg1-shRNA1 and Ad5-Herg1-shRNA2 group were (65.47±3.90)% and (79.90±1.52)%, significantly lower than (100.00±6.14)% of Ad5-control-shRNA group. Meanwhile, U2OS cell vitality of Ad5-Herg1-shRNA1 and Ad5-Herg1-shRNA2 group were (69.69±1.36)% and (76.72±2.75)%, significantly lower than (100.00±3.01)% of Ad5-control-shRNA group (all P<0.001). The results of wound healing array showed that 143B cell migration rates of Ad5-Herg1-shRNA1 and Ad5-Herg1-shRNA2 group were (33.03±2.88)% and (36.47±4.16)%, significantly lower than (97.78±2.28)% of Ad5-control-shRNA group. Meanwhile, U2OS cell migration rates of Ad5-Herg1-shRNA1 and Ad5-Herg1-shRNA2 group were (68.07±0.90)% and (73.97±1.25)%, significantly lower than (96.50±1.12)% of Ad5-control-shRNA group (all P<0.001). The results of Transwell showed that 143B cell invasion numbers of Ad5-Herg1-shRNA1 and Ad5-Herg1-shRNA2 group were 36.50±12.15 and 44.83±7.62, significantly lower than 195.33±19.68 of Ad5-control-shRNA group. Meanwhile, U2OS cell migration rates of Ad5-Herg1-shRNA1 and Ad5-Herg1-shRNA2 group were 21.83±7.99 and 22.85±7.08, significantly lower than 83.33±12.36 of Ad5-control-shRNA group (all P<0.001). The results of xenograft model of OS showed that the tumor volume and weight of Ad5-Herg1-shRNA group were significantly smaller than of Ad5-control-shRNA group after 14 days and 5 weeks of inoculation, respectively (P<0.001). Moreover, knockdown of Herg1 inhibited the metastasis of OS cells. In mechanism, Herg1 protein interacted with NF2 protein. Knockdown of Herg1 significantly suppressed the expression levels of LATS1 and YAP protein, and promoted the phosphorylation of LATS1 and YAP in OS cells (all P<0.001). Conclusion: Our findings suggest that Herg1 participates in the proliferation and motility of OS cells and may serve as a potential therapeutic target for osteosarcoma patients.

Modulation of KV10.1 Potassium Channel Function by Intracellular Heme

Heme, an iron-protoporphyrin-IX complex, is a cofactor bound to various hemoproteins and promotes a broad range of functions, such as electron transfer, oxygen transport, signal transduction, and drug metabolism. In recent years, there has been growing recognition of heme as a non-genomic modulator of ion channel functions. Here, we show that intracellular free heme/hemin modulates human ether à go-go (hEAG1, Kv10.1) voltage-gated potassium channels. We used an integrative approach that combines electrophysiology and biochemical techniques to dissect the impact of heme on human Kv10.1 channels. Electrophysiology experiments were conducted in the inside-out patch-clamp configuration on Xenopus oocytes. Intracellular application of hemin (Fe3+-protoporphyrin-IX) potently inhibited Kv10.1 channels with an apparent IC50 of 4.2±0.3 nM (oxidizing condition) and 63.3±4.5 nM (reducing condition). Hemin did not affect other delayed rectifier K+ channels such as Kv1.1, Kv1.5, and Kv1.6. The onset of the hemin inhibitory effect on the current followed an exponential time course and was very slowly reversible upon washout. Protoporphyrin-IX and Fe2+ were ineffective on Kv10.1 channel currents. Hemin acts as a gating modifier by reducing the probability of channel opening in a voltage-dependent manner. Studies on recombinant channel fragments encompassing the C terminus of Kv10.1 (M478-N673) revealed a heme-responsive binding site in the C-linker region involving histidine 543 and 552. Heme binding to the C-linker possibly induces a conformational constraint that interferes with channel opening. Overall, this study suggested that free heme is a physiologically relevant modulator of Kv10.1 channels activity and neuronal excitability.