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Abstract: Objective: The human ether-a-go-go-related gene (hERG) encodes the rapid component of the cardiac repolarizing delayed rectifier potassium current, IKr. The direct interaction of the commonly used protein kinase C (PKC) inhibitor bisindolylmaleimide I (BIM I) with hERG, KvLQT1/minK, and IKr currents was investigated in this study. Methods: hERG and KvLQT1/minK channels were heterologously expressed in Xenopus laevis oocytes, and currents were measured using the two-microelectrode voltage clamp technique. In addition, hERG currents in stably transfected human embryonic kidney (HEK 293) cells, native IKr currents and action potentials in isolated guinea pig ventricular cardiomyocytes were recorded using whole-cell patch clamp electrophysiology. Results: Bisindolylmaleimide I blocked hERG currents in HEK 293 cells and Xenopus oocytes in a concentration-dependent manner with IC50 values of 1.0 and 13.2 μM, respectively. hERG channels were primarily blocked in the open state in a frequency-independent manner. Analysis of the voltage-dependence of block revealed a reduction of inhibition at positive membrane potentials. BIM I caused a shift of −20.3 mV in the voltage-dependence of inactivation. The point mutations tyrosine 652 alanine (Y652A) and phenylalanine 656 alanine (F656A) attenuated hERG current blockade, indicating that BIM I binds to a common drug receptor within the pore region. KvLQT1/minK currents were not significantly altered by BIM I. Finally, 1 μM BIM I reduced native IKr currents by 69.2% and lead to action potential prolongation. Conclusion: In summary, PKC-independent effects have to be carefully considered when using BIM I as PKC inhibitor in experimental models involving hERG channels and IKr currents. [Copyright &y& Elsevier]

Zebrafish combine the relevance of a vertebrate with the scalability of an invertebrate. They can live in 96-well plate format and readily absorb chemicals from the water. These features have stimulated the use of zebrafish by medical researchers to model human disease and then assess the action of compounds in a whole organism. Examples of the power of this system have been illustrated with the cloning of zebrafish human ether-a-go-go-related gene (HERG), which shows near 100% homology in key domains, and the associated ability to identify drugs that prolong the QT interval both rapidly and with tiny amounts (micrograms) of compound. [Copyright &y& Elsevier]

The scorpion toxin peptide BeKm-1 was synthesised by fluorenylmethoxycarbonyl solid phase chemistry and folded by air oxidation. The peptide’s effects on heterologous human ether-a-go-go-related gene potassium current (IHERG) in HEK293 cells were assessed using ‘whole-cell’ patch clamp. Blockade of IHERG by BeKm-1 was concentration-dependent, temperature-dependent, and rapid in onset and reversibility. Blockade also exhibited inverse voltage dependence, inverse dependence on duration of depolarisation, and reverse use- and frequency-dependence. Blockade by BeKm-1 and recombinant ergtoxin, another scorpion toxin known to block HERG, differed in their recovery from HERG current inactivation elicited by strong depolarisation and in their ability to block HERG when the channels were already activated. We conclude that synthetic BeKm-1 toxin blocks HERG preferentially through a closed (resting) state channel blockade mechanism, although some open channel blockade also occurs. [Copyright &y& Elsevier]

Objective: Patients with HERG-associated long QT syndrome typically develop tachyarrhythmias during physical or emotional stress. Previous studies have revealed that activation of the beta-adrenergic system and consecutive elevation of the intracellular cAMP concentration regulate HERG channels via protein kinase A-mediated phosphorylation of the channel protein and via direct interaction with the cAMP binding site of HERG. In contrast, the influence of the alpha-adrenergic signal transduction cascade on HERG currents as suggested by recent reports is less well understood. The aim of the present study was to elucidate the biochemical pathways of the protein kinase C (PKC)-dependent regulation of HERG currents. Methods: HERG channels were heterologously expressed in Xenopus laevis oocytes, and currents were measured using the two-microelectrode voltage clamp technique. Results: Application of the phorbol ester PMA, an unspecific protein kinase activator, shifted the voltage dependence of HERG activation towards more positive potentials. This effect could be mimicked by activation of conventional PKC isoforms with thymeleatoxin. Coexpression of HERG with the beta-subunits minK or hMiRP1 did not alter the effect of PMA. Specific inhibition of PKC abolished the PMA-induced activation shift, suggesting that PKC is required within the regulatory mechanism. The PMA-induced effect could still be observed when the PKC-dependent phosphorylation sites in HERG were deleted by mutagenesis. Cytoskeletal proteins such as actin filaments or microtubules did not affect the HERG activation shift. Conclusion: In addition to the known effects of PKA and cAMP, HERG channels are also modulated by PKC. The molecular mechanisms of this PKC-dependent process are not completely understood but do not depend on direct PKC-dependent phosphorylation of the channel. [Copyright &y& Elsevier]

The three-dimensional structure of chemically synthesized CnErg1 (Ergtoxin), which specifically blocks HERG (human ether-a-go-go-related gene) K+ channels, was determined by nuclear magnetic resonance spectroscopy. CnErg1 consists of a triple-stranded β-sheet and an α-helix, as is typical of K+ channel scorpion toxins. The peptide structure differs from the canonical structures in that the first β-strand is shorter and is nearer to the second β-strand rather than to the third β-strand on the C-terminus. There is also a large hydrophobic patch on the surface of the toxin, surrounding a central lysine residue, Lys13. We postulate that this hydrophobic patch is likely to form part of the binding surface of the toxin. [Copyright &y& Elsevier]

We used Xenopus oocytes co-expressing thyrotropin-releasing hormone (TRH) receptors and human ether-a-go-go-related gene (HERG) K+ channel variants carrying different amino-terminal modifications to check the relevance of the proximal domain for hormonal regulation of the channel. Deletion of the whole proximal domain (Δ138–373) eliminates TRH-induced modifications in activation and deactivation parameters. TRH effects on activation are also suppressed with channels lacking the second half of the proximal domain or only residues 326–373. However, normal responses to TRH are obtained with Δ346–373 channels. Thus, whereas residues 326–345 are required for the hormonal modulation of HERG activation, different proximal domain sequences contribute to set HERG gating characteristics and its regulation by TRH. [Copyright &y& Elsevier]

Severe acute respiratory syndrome has relapsed recently as novel coronavirus causing a life threat to the entire world in the absence of an effective therapy. To hamper the replication of the deadly SARS CoV-2 inside the host cells, systematic in silico virtual screening of total 267,324 ligands from Asinex EliteSynergy and BioDesign libraries has been performed using AutoDock Vina against RdRp. The molecular modeling studies revealed the identification of twenty-one macrocyclic hits ( 2 - 22 ) with better binding energy than remdesivir ( 1 ), marketed SARS CoV-2 inhibitor. Further, the analysis using rules for drug-likeness and their ADMET profile revealed the candidature of these hits due to superior oral bioavailability and druggability. Further, the MD simulation studies of top two hits ( 2 and 3 ) performed using GROMACS 2020.1 for 10 ns revealed their stability into the docked complexes. These results provide an important breakthrough in the design of macrocyclic hits as SARS CoV-2 RNA replicase inhibitor., Competing Interests: The authors declare no competing financial interest., (© 2021 Elsevier B.V. All rights reserved.)

The 90-kiloDalton (kD) heat shock protein (Hsp90) is a ubiquitous, ATP-dependent molecular chaperone whose primary function is to ensure the proper folding of several hundred client protein substrates. Because many of these clients are overexpressed or become mutated during cancer progression, Hsp90 inhibition has been pursued as a potential strategy for cancer as one can target multiple oncoproteins and signaling pathways simultaneously. The first discovered Hsp90 inhibitors, geldanamycin and radicicol, function by competitively binding to Hsp90's N-terminal binding site and inhibiting its ATPase activity. However, most of these N-terminal inhibitors exhibited detrimental activities during clinical evaluation due to induction of the pro-survival heat shock response as well as poor selectivity amongst the four isoforms. Consequently, alternative approaches to Hsp90 inhibition have been pursued and include C-terminal inhibition, isoform-selective inhibition, and the disruption of Hsp90 protein-protein interactions. Since the Hsp90 protein folding cycle requires the assembly of Hsp90 into a large heteroprotein complex, along with various co-chaperones and immunophilins, the development of small molecules that prevent assembly of the complex offers an alternative method of Hsp90 inhibition., Competing Interests: The authors have no conflict of interest to declare., (© 2020 Chinese Pharmaceutical Association and Institute of Materia Medica, Chinese Academy of Medical Sciences. Production and hosting by Elsevier B.V.)

Medulloblastoma (MB) is a common yet highly heterogeneous childhood malignant brain tumor, however, clinically effective molecular targeted therapy is lacking. Modulation of hedgehog (HH) signaling by epigenetically targeting the transcriptional factors GLI through bromodomain-containing protein 4 (BRD4) has recently spurred new interest as potential treatment of HH-driven MB. Through screening of current clinical BRD4 inhibitors for their inhibitory potency against glioma-associated oncogene homolog (GLI) protein, the BRD4 inhibitor 2 was selected as the lead for further structural optimization, which led to the identification of compounds 25 and 35 as the high potency HH inhibitors. Mechanism profiling showed that both compounds suppressed HH signaling by interacting with the transcriptional factor GLI, and were equally potent against the clinical resistant mutants and the wild type of smoothened (SMO) receptor with IC 50 values around 1 nmol/L. In the resistant MB allograft mice, compound 25 was well tolerated and markedly suppressed tumor growth at both 5 mg/kg (TGI = 83.3%) and 10 mg/kg (TGI = 87.6%) doses. Although further modification is needed to improve the pharmacokinetic (PK) parameters, compound 25 represents an efficacious lead compound of GLI inhibitors, possessing optimal safety and tolerance to fight against HH-driven MB., Competing Interests: The authors have no conflicts of interest to declare., (© 2021 Chinese Pharmaceutical Association and Institute of Materia Medica, Chinese Academy of Medical Sciences. Production and hosting by Elsevier B.V.)

Background: Among many drugs that hold potential in COVID-19 pandemic, chloroquine (CQ), and its derivative hydroxychloroquine (HCQ) have generated unusual interest. With increasing usage, there has been growing concern about the prolongation of QTc interval and Torsades de Pointes (TdP) with HCQ, especially in combination with azithromycin., Aims: This meta-analysis is planned to study the risk of QTc prolongation and Torsades de pointes (TdP) by a well-defined criterion for HCQ, CQ alone, and in combination with Azithromycin in patients with COVID-19., Methods: A comprehensive literature search was made in two databases (PubMed, Embase). Three outcomes explored in the included studies were frequency of QTc > 500 ms (ms) or ΔQTc > 60 ms (Outcome 1), frequency of QTc > 500 ms (Outcome 2) and frequency of TdP (Outcome 3). Random effects method with inverse variance approach was used for computation of pooled summary and risk ratio., Results: A total of 13 studies comprising of 2138 patients were included in the final analysis. The pooled prevalence of outcome 1, outcome 2 and outcome 3 for HCQ, CQ with or without Azithromycin were 10.18% (5.59-17.82%, I 2 - 92%), 10.22% (6.01-16.85%, I 2 - 79%), and 0.72% (0.34-1.51, I 2 - 0%) respectively. The prevalence of outcome 2 in subgroup analysis for HCQ and HCQ + Azithromycin was 7.25% (3.22-15.52, I 2 - 59%) and 8.61% (4.52-15.79, I 2 - 76%), respectively. The risk ratio (RR) for outcome 1 and outcome 2 between HCQ + Azithromycin and HCQ was 1.22 (0.77-1.93, I 2 - 0%) & 1.51 (0.79-2.87, I 2 - 13%), respectively and was not significant. Heterogeneity was noted statistically as well clinically (regimen types, patient numbers, study design, and outcome definition)., Conclusion: The use of HCQ/CQ is associated with a high prevalence of QTc prolongation. However, it is not associated with a high risk of TdP., Competing Interests: None., (© 2020 Indian Heart Rhythm Society. Production and hosting by Elsevier B.V.)

Src homology containing protein tyrosine phosphatase 2 (SHP2) represents a noteworthy target for various diseases, serving as a well-known oncogenic phosphatase in cancers. As a result of the low cell permeability and poor bioavailability, the traditional inhibitors targeting the protein tyrosine phosphate catalytic sites are generally suffered from unsatisfactory applied efficacy. Recently, a particularly large number of allosteric inhibitors with striking inhibitory potency on SHP2 have been identified. In particular, few clinical trials conducted have made significant progress on solid tumors by using SHP2 allosteric inhibitors. This review summarizes the development and structure-activity relationship studies of the small-molecule SHP2 inhibitors for tumor therapies, with the purpose of assisting the future development of SHP2 inhibitors with improved selectivity, higher oral bioavailability and better physicochemical properties., Competing Interests: The authors have no conflicts of interest to declare., (© 2021 Chinese Pharmaceutical Association and Institute of Materia Medica, Chinese Academy of Medical Sciences. Production and hosting by Elsevier B.V.)

Disopyramide is effective and safe in patients with obstructive hypertrophic cardiomyopathy. However, its cellular and molecular mechanisms of action are unknown. We tested disopyramide in cardiomyocytes from the septum of surgical myectomy patients: disopyramide inhibits multiple ion channels, leading to lower Ca transients and force, and shortens action potentials, thus reducing cellular arrhythmias. The electrophysiological profile of disopyramide explains the efficient reduction of outflow gradients but also the limited prolongation of the QT interval and the absence of arrhythmic side effects observed in 39 disopyramide-treated patients. In conclusion, our results support the idea that disopyramide is safe for outpatient use in obstructive patients., (© 2019 The Authors.)

Chronic constipation is a common gastrointestinal disease severely affecting the patient׳s quality of life. The traditional treatment of constipation is the use of laxatives. Recently, several new drugs including lubiprostone, linaclotide and prucalopride have been approved for treatment of chronic constipation. However, a significant unmet medical need still remains, particularly among those patients achieving poor results by current therapies. The 5-HT4 receptor modulators velusetrag and naronapride, the guanylate cyclase C agonist plecanatide and the ileal bile acid transporter inhibitor elobixibat are recognized as the most promising drugs under investigation. Herein, we give a comprehensive review on the pharmacological therapeutics for the treatment of chronic constipation, with the purpose of reflecting the drug development trends in this field.