Function and interaction of coronavirus ion channel proteins

Objective: COVID-19 has emerged as a significant global health crisis causing devastating effects on world population accounting for over 6 million deaths worldwide. Although acute RTI is the prevalent cause of morbidity, kidney outcomes centered on a spectrum of AKI have evolved over the course of the pandemic. Especially the emerging variants have posed a daunting challenge to the scientific communities, prompting an urging requirement for global contributions in understanding the viral dynamics. In addition to canonical genes, several subgroup- specific accessory genes are located between the S and E genes of coronaviruses regarding which little is known. Previous studies have shown that accessory proteins (aps) in viruses function as viroporins that regulate viral infection, propagation and egress [1]. In this study we attempted to characterize the function of aps of coronavirus variants as ion channels. Furthermore, we also probed the interaction of ap4 with the host system. Method(s): Serial passaging (selection pressure), growth kinetics, confocal imaging, genome sequence analysis and proteomics were performed in Huh-7, MRC5 cells and/or human monocyte derived macrophages. Potassium uptake assay was performed in a Saccharo myces cerevisiae strain, which lacks the potassium transporters trk1 and trk2. Ion conductivity experiments were performed in Xenopus laevis oocytes using Two Electrode Voltage Clamp (TEVC) method. Result(s): Serial passaging demonstrated the acquisition of several frameshift mutations in ORF4 resulting in C-terminally truncated protein versions (ap4 and ap4a) and indicate a strong selection pressure against retaining a complete ORF4 in vitro. Growth kinetics in primary cells illustrated a reduction of viral titers when the full-length ap4 was expressed compared to the C-terminally truncated protein ap4a. Confocal imaging showed that ap4 and ap4a are not exclusively located in a single cellular compartment. Potassium uptake assay in yeast and TEVC analyses in Xenopus oocytes showed that ap4 and ap4a act as a weak K+ selective ion channel. In addition, accessory proteins of other virus variants also elicited microampere range of currents. Conclusion(s): Our study provides the first evidence that ap4 and other accessory proteins of coronavirus variants act as viroporins. Future studies are aimed at demonstrating the role of ap4 during the viral life cycle by modulating ion homeostasis of host cell in vivo (interacting proteins obtained from proteomic studies) and thereby serve as a tool for potential drug target.

Jahrestagung der Gesellschaft fur Padiatrische Nephrologie.

The proceedings contain 92 papers. The topics discussed include: cellular and humoral immune responses after SARS-CoV-2 vaccination in pediatric kidney recipients;adult outcomes of childhood-onset idiopathic nephrotic syndrome: findings from a health insurance database;the genetic landscape and clinical spectrum of nephronophthisis and related ciliopathies;translational profiling of developing podocytes during glomerulogenesis;MAGED2 is required under hypoxia for cAMP signaling by inhibiting MDM2-dependent endocytosis of G-Alpha-S;high throughput investigation of the metabolic flux of intact cortical kidney tubules;peritoneal membrane junction and solute transporter expression and function in health, CKD and PD;and Function and interaction of coronavirus ion channel proteins.

Randomized controlled study protocol: Shensong Yangxin in persistent atrial fibrillation after radiofrequency catheter ablation (SS-ADJUST)

Introduction: Atrial fibrillation (AF) is one of the most common forms of arrhythmia in the clinic. There are about 10 million AF patients in China, of which 1/3 are paroxysmal AF, and the remaining 2/3 are persistent or permanent AF. Long-term AF impairs cardiac function and leads to heart failure and thromboembolism. Moreover, AF increases the risk of mortality and ischemic stroke. Drug therapy and radiofrequency catheter ablation (RFCA) are still the mainstream treatment for AF patients. However, drug therapy has its drawbacks because of the high recurrence rate and side effects. Therefore, the current antiarrhythmic drugs could not meet all the clinical needs of patients with AF. RFCA is superior to antiarrhythmic drugs in maintaining sinus rhythm, improving symptoms and exercise tolerance, and improving quality of life. The role of RFCA in the treatment of persistent AF has gradually been recognized and affirmed. Although RFCA has been progressively used in the treatment of AF, there is still a high recurrence rate of AF after RFCA, especially in patients with persistent AF. Hence, it is meant to solve the high recurrence rate of AF after RFCA. Shensong Yangxin (SSYX) capsule has been proven to treat arrhythmia both in animal studies and clinical research. SSYX capsule could regulate multi-ion channels, improve cardiomyocyte metabolism and regulate autonomic nervous function. In addition, randomized, double-blind, multicenter clinical research indicated that the SSYX capsule exhibited good clinical efficacy in treating ventricular premature beats and paroxysmal AF. However, the effect of SSYX on recurrence after RFCA for patients with persistent AF remains unclear. High-level randomized controlled trials (RCTs) could offer clinicians high-quality evidence regarding the usage of SSYX capsule, especially in persistent AF patients who received RFCA. Hence, the RCTs aim to evaluate the effect of SSYX capsules on the prognosis in patients with persistent AF after RFCA through multicenter, double-blind RCTs. Method(s): This trial will be conducted with a total of 920 participants diagnosed with persistent AF who received RFCA. The participants will be randomized (1:1) into groups receiving either SSYX or Placebo for 1 year. The primary endpoint includes the recurrence of AF within 1 year after RFCA. The secondary outcome measures include changes of AF load at 3 months, 6 months, 9 months, and 1 year after treatment, the time of first atrial flutter/AF, the incidence of cardioversion 1 year after treatment, changes of transthoracic echocardiographic parameters 1 year after treatment, the incidence of stroke and thromboembolism at 6 months and 1 year after treatment, the score of SF-36 within 1 year after treatment. Application: The trial is ongoing. The trial started in September 2019 and recruiting patients. Data collection will be completed after all participants have completed the treatment course and follow-up assessments (expected in 2022, pending COVID-19). Next Steps/Future: The SS-ADJUST study is a randomized control study of TCM in persistent AF after RFCA. It will determine the place of SSYX capsule as a new treatment approach and provide additional and innovative information regarding TCM and the specific use of SSYX in persistent AF after RFCA.

Comparative analysis of SARS-CoV-2 envelope viroporin mutations from COVID-19 deceased and surviving patients revealed implications on its ion-channel activities and correlation with patient mortality.

One major obstacle in designing a successful therapeutic regimen to combat COVID-19 pandemic is the frequent occurrence of mutations in the SARS-CoV-2 resulting in patient to patient variations. Out of the four structural proteins of SARS-CoV-2 namely, spike, envelope, nucleocapsid and membrane, envelope protein governs the virus pathogenicity and induction of acute-respiratory-distress-syndrome which is the major cause of death in COVID-19 patients. These effects are facilitated by the viroporin (ion-channel) like activities of the envelope protein. Our current work reports metagenomic analysis of envelope protein at the amino acid sequence level through mining all the available SARS-CoV-2 genomes from the GISAID and coronapp servers. We found majority of mutations in envelope protein were localized at or near PDZ binding motif. Our analysis also demonstrates that the acquired mutations might have important implications on its structure and ion-channel activity. A statistical correlation between specific mutations (e.g. F4F, R69I, P71L, L73F) with patient mortalities were also observed, based on the patient data available for 18,691 SARS-CoV-2-genomes in the GISAID database till 30 April 2021. Albeit, whether these mutations exist as the cause or the effect of co-infections and/or co-morbid disorders within COVID-19 patients is still unclear. Moreover, most of the current vaccine and therapeutic interventions are revolving around spike protein. However, emphasizing on envelope protein's (1) conserved epitopes, (2) pathogenicity attenuating mutations, and (3) mutations present in the deceased patients, as reported in our present study, new directions to the ongoing efforts of therapeutic developments against COVID-19 can be achieved by targeting envelope viroporin.

SARS-CoV-2 infection alkalinizes the ERGIC and lysosomes through the viroporin activity of the viral envelope protein.

The coronavirus SARS-CoV-2, the agent of the deadly COVID-19 pandemic, is an enveloped virus propagating within the endocytic and secretory organelles of host mammalian cells. Enveloped viruses modify the ionic homeostasis of organelles to render their intra-luminal milieu permissive for viral entry, replication and egress. Here, we show that infection of Vero E6 cells with the delta variant of the SARS-CoV-2 alkalinizes the endoplasmic reticulum (ER)-Golgi intermediate compartment (ERGIC) as well as lysosomes, mimicking the effect of inhibitors of vacuolar proton ATPases. We further show the envelope protein of SARS-CoV-2 accumulates in the ERGIC when expressed in mammalian cells and selectively dissipates the ERGIC pH. This viroporin action is prevented by mutations of Val25 but not Asn15 within the channel pore of the envelope (E) protein. We conclude that the envelope protein acts as a proton channel in the ERGIC to mitigate the acidity of this intermediate compartment. The altered pH homeostasis of the ERGIC likely contributes to the virus fitness and pathogenicity, making the E channel an attractive drug target for the treatment of COVID-19.

Probing the mechanical properties of ORF3a protein, a transmembrane channel of SARS-CoV-2 virus: Molecular dynamics study.

SARS-CoV-2-encoded accessory protein ORF3a was found to be a conserved coronavirus protein that shows crucial roles in apoptosis in cells as well as in virus release and replications. To complete the knowledge and identify the unknown of this protein, further comprehensive research is needed to clarify the leading role of ORF3a in the functioning of the coronavirus. One of the efficient approaches to determining the functionality of this protein is to investigate the mechanical properties and study its structural dynamics in the presence of physical stimuli. Herein, performing all-atom steered molecular dynamics (SMD) simulations, the mechanical properties of the force-bearing components of the ORF3a channel are calculated in different physiological conditions. As variations occurring in ORF3a may lead to alteration in protein structure and function, the G49V mutation was also simulated to clarify the relationship between the mechanical properties and chemical stability of the protein by comparing the behavior of the wild-type and mutant Orf3a. From a physiological conditions point of view, it was observed that in the solvated system, the presence of water molecules reduces Young's modulus of TM1 by ∼30 %. Our results also show that by substitution of Gly49 with valine, Young's modulus of the whole helix increases from 1.61 ± 0.20 to 2.08 ± 0.15 GPa, which is consistent with the calculated difference in free energy of wild-type and mutant helices. In addition to finding a way to fight against Covid-19 disease, understanding the mechanical behavior of these biological nanochannels can lead to the development of the potential applications of the ORF3a protein channel, such as tunable nanovalves in smart drug delivery systems, nanofilters in the new generation of desalination systems, and promising applications in DNA sequencing.

Exhaustive Mutational Analysis of scv ORF3a: an Essential Component in the Pathogen's Infectivity Cycle.

Detailed knowledge of a protein's key residues may assist in understanding its function and designing inhibitors against it. Consequently, such knowledge of one of SARS-CoV-2's proteins is advantageous since the virus is the etiological agent behind one of the biggest health crises of recent times. To that end, we constructed an exhaustive library of bacteria differing from each other by the mutated version of the virus's ORF3a viroporin they harbor. Since the protein is harmful to bacterial growth due to its channel activity, genetic selection followed by deep sequencing could readily identify mutations that abolish the protein's function. Our results have yielded numerous mutations dispersed throughout the sequence that counteract ORF3a's ability to slow bacterial growth. Comparing these data with the conservation pattern of ORF3a within the coronavirinae provided interesting insights: Deleterious mutations obtained in our study corresponded to conserved residues in the protein. However, despite the comprehensive nature of our mutagenesis coverage (108 average mutations per site), we could not reveal all of the protein's conserved residues. Therefore, it is tempting to speculate that our study unearthed positions in the protein pertinent to channel activity, while other conserved residues may correspond to different functionalities of ORF3a. In conclusion, our study provides important information on a key component of SARS-CoV-2 and establishes a procedure to analyze other viroporins comprehensively. This article is protected by copyright. All rights reserved.

The SARS-CoV-2 accessory protein Orf3a is not an ion channel, but does interact with trafficking proteins.

The severe acute respiratory syndrome associated coronavirus 2 (SARS-CoV-2) and SARS-CoV-1 accessory protein Orf3a colocalizes with markers of the plasma membrane, endocytic pathway, and Golgi apparatus. Some reports have led to annotation of both Orf3a proteins as viroporins. Here, we show that neither SARS-CoV-2 nor SARS-CoV-1 Orf3a form functional ion conducting pores and that the conductances measured are common contaminants in overexpression and with high levels of protein in reconstitution studies. Cryo-EM structures of both SARS-CoV-2 and SARS-CoV-1 Orf3a display a narrow constriction and the presence of a positively charged aqueous vestibule, which would not favor cation permeation. We observe enrichment of the late endosomal marker Rab7 upon SARS-CoV-2 Orf3a overexpression, and co-immunoprecipitation with VPS39. Interestingly, SARS-CoV-1 Orf3a does not cause the same cellular phenotype as SARS-CoV-2 Orf3a and does not interact with VPS39. To explain this difference, we find that a divergent, unstructured loop of SARS-CoV-2 Orf3a facilitates its binding with VPS39, a HOPS complex tethering protein involved in late endosome and autophagosome fusion with lysosomes. We suggest that the added loop enhances SARS-CoV-2 Orf3a's ability to co-opt host cellular trafficking mechanisms for viral exit or host immune evasion.

Oligomerization-Dependent Beta-Structure Formation in SARS-CoV-2 Envelope Protein.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the current COVID-19 pandemic. In SARS-CoV-2, the channel-forming envelope (E) protein is almost identical to the E protein in SARS-CoV, and both share an identical α-helical channel-forming domain. Structures for the latter are available in both detergent and lipid membranes. However, models of the extramembrane domains have only been obtained from solution NMR in detergents, and show no ß-strands, in contrast to secondary-structure predictions. Herein, we have studied the conformation of purified SARS-CoV-2 E protein in lipid bilayers that mimic the composition of ER-Golgi intermediate compartment (ERGIC) membranes. The full-length E protein at high protein-to-lipid ratios produced a clear shoulder at 1635 cm-1, consistent with the ß-structure, but this was absent when the E protein was diluted, which instead showed a band at around 1688 cm-1, usually assigned to ß-turns. The results were similar with a mixture of POPC:POPG (2-oleoyl-1-palmitoyl-sn-glycero-3-phosphocholine/3-glycerol) and also when using an E-truncated form (residues 8-65). However, the latter only showed ß-structure formation at the highest concentration tested, while having a weaker oligomerization tendency in detergents than in full-length E protein. Therefore, we conclude that E monomer-monomer interaction triggers formation of the ß-structure from an undefined structure (possibly ß-turns) in at least about 15 residues located at the C-terminal extramembrane domain. Due to its proximity to the channel, this ß-structure domain could modulate channel activity or modify membrane structure at the time of virion formation inside the cell.

Cardiac effects and toxicity of chloroquine: a short update.

There is currently increased interest in the use of the antimalarial drugs chloroquine and hydroxychloroquine for the treatment of other diseases, including cancer and viral infections such as coronavirus disease 2019 (COVID-19). However, the risk of cardiotoxic effects tends to limit their use. In this review, the effects of these drugs on the electrical and mechanical activities of the heart as well as on remodelling of cardiac tissue are presented and the underlying molecular and cellular mechanisms are discussed. The drugs can have proarrhythmic as well as antiarrhythmic actions resulting from their inhibition of ion channels, including voltage-dependent Na+ and Ca2+ channels, background and voltage-dependent K+ channels, and pacemaker channels. The drugs also exert a vagolytic effect due at least in part to a muscarinic receptor antagonist action. They also interfere with normal autophagy flux, an effect that could aggravate ischaemia/reperfusion injury or post-infarct remodelling. Most of the toxic effects occur at high concentrations, following prolonged drug administration or in the context of drug associations.

Assessing the potential of repurposing ion channel inhibitors to treat emerging viral diseases and the role of this host factor in virus replication.

As diseases caused by new and emerging viruses continue to be a major threat to humans and animals worldwide the need for new therapeutic options intensifies. A wide variety of viruses including Influenza A virus, Human immunodeficiency virus, Middle East respiratory syndrome coronavirus and severe acute respiratory syndrome coronavirus require ion channels for efficient replication. Thus, targeting host ion channels may serve as an effective means to attenuate virus replication and help treat viral diseases. Targeting host ion channels is an attractive therapeutic option because a range of ion channel-blocking compounds already exist for the treatment of other human diseases and some of these possess in vitro and sometimes in vivo antiviral activity. Therefore, identifying the specific ion channels involved in replicative cycles could provide opportunities to repurpose these ion channel inhibitors for treating viral diseases. Furthermore, optimised methodologies for identifying effective ion channel targeting drugs and their mechanisms of action could enable rapid responses to newly emerged viruses. This review discusses the potential of ion channels as suitable drug targets to treat diseases caused by viruses by describing known ion channel targeting drugs including their antiviral activity; by summarising prior research demonstrating the requirement for host ion channels for efficient replication of some viruses; and by hypothesising about the role these drugs might play in our ongoing fight against viral diseases.

GABAA receptors as targets for anaesthetics and analgesics and promising candidates to help treat coronavirus infections: A mini-review.

GABA is a major inhibitory neurotransmitter that regulates the balance between excitatory and inhibitory circuits in the human nervous system. The GABA receptors are divided into three main subtypes, GABAA , GABAB , and GABAC (also termed GABAA rho) receptors. GABAA receptors are pentameric ligand-gated ion channels widely expressed throughout the central and peripheral nervous system. The activation of GABAA receptors results in opening of an anion-selective channel that mainly gates chloride ions and allows them to flow into the neuron, causing hyperpolarization of the cell membrane that dampens neural excitability. This makes GABAA receptors critical anaesthetic and analgesic targets for existing as well as for the development of novel drugs. In this review, we first summarize the biochemical properties of GABAA receptors and the clinical anaesthetics and analgesics targeting the receptors. In a forward-looking section, we summarize the emerging role of GABAergic signalling in treatment of COVID-19 related infections. Finally, we discuss the opportunities arising from targeting specific and unique subunit interfaces for the development of novel anaesthetics and analgesics leading to more efficient therapies.

Ion channel inhibition with amiodarone or verapamil in symptomatic hospitalized nonintensive-care COVID-19 patients: The ReCOVery-SIRIO randomized trial.

BACKGROUND: Ion channel inhibition may offer protection against coronavirus disease 2019 (COVID-19). Inflammation and reduced platelet count occur during COVID-19 but precise quantification of risk thresholds is unclear. The Recov ery-SIRIO study aimed to assess clinical effects of amiodarone and verapamil and to relate patient phenotypes to outcomes. METHODS: RECOVERY-SIRIO is a multicenter open-label 1:1:1 investigator-initiated randomized trial with blinded event adjudication. A sample of 804 symptomatic hospitalized nonintensive-care COVID-19 patients, follow-up for 28 days was initially planned. RESULTS: The trial was stopped when a total of 215 patients had been randomized to amiodarone (n = 71), verapamil (n = 72) or standard care alone (n = 72). At 15 days, the hazard ratio (hazard ratio [HR], 95% confidence interval [CI]) for clinical improvement was 0.77 (0.52-1.14) with amiodarone and 0.97 (0.81-1.17) with verapamil as compared to usual care. Clinically relevant associations were found between mortality or lack of clinical improvement and higher peak C-reactive protein (CRP) levels or nadir platelet count at 7, 10 and 15 days. Mortality rate increased by 73% every 5 mg/dL increment in peak CRP (HR 1.73, 95% CI 1.27-2.37) and was two-fold higher for every decrement of 100 units in nadir platelet count (HR 2.19, 95% CI 1.37-3.51). By cluster analysis, thresholds of 5 mg/dL for peak CRP and 187 × 103/mcL for nadir platelet count identified the phenogroup at greatest risk of dying. CONCLUSIONS: In this randomized trial, neither amiodarone nor verapamil were found to significantly accelerate short-term clinical improvement. Peak CRP and nadir platelet counts were associated with increased mortality both in isolation and by cluster analysis.

The Three Two-Pore Channel Subtypes from Rabbit Exhibit Distinct Sensitivity to Phosphoinositides, Voltage, and Extracytosolic pH.

Two pore channels (TPCs) are implicated in vesicle trafficking, virus infection, and autophagy regulation. As Na+- or Ca2+-permeable channels, TPCs have been reported to be activated by NAADP, PI(3,5)P2, and/or high voltage. However, a comparative study on the function and regulation of the three mammalian TPC subtypes is currently lacking. Here, we used the electrophysiological recording of enlarged endolysosome vacuoles, inside-out and outside-out membrane patches to examine the three TPCs of rabbit (Oryctolagus cuniculus, or Oc) heterologously expressed in HEK293 cells. While PI(3,5)P2 evoked Na+ currents with a potency order of OcTPC1 > OcTPC3 > OcTPC2, only OcTPC2 displayed a strict dependence on PI(3,5)P2. Both OcTPC1 and OcTPC3 were activatable by PI3P and OcTPC3 was also activated by additional phosphoinositide species. While OcTPC2 was voltage-independent, OcTPC1 and OcTPC3 showed voltage dependence with OcTPC3 depending on high positive voltages. Finally, while OcTPC2 preferred a luminal pH of 4.6-6.0 in endolysosomes, OcTPC1 was strongly inhibited by extracytosolic pH 5.0 in both voltage-dependent and -independent manners, and OcTPC3 was inhibited by pH 6.0 but potentiated by pH 8.0. Thus, the three OcTPCs form phosphoinositide-activated Na+ channels with different ligand selectivity, voltage dependence, and extracytosolic pH sensitivity, which likely are optimally tuned for function in specific endolysosomal populations.

Cellular and Molecular Machinery of Neuropathic Pain: an Emerging Insight.

Purpose of Review: Neuropathic pain (NP) has been ubiquitously characterized by lesion and its linked somatosensory system either the central nervous system (CNS) or peripheral nervous system (PNS) This PNS episode is the most prevalent site of NP origin and is found to be associated with afferent nerve fibers carrying pain signals from injured/trauma site to the CNS including the brain. Several kinds of pharmacotherapeutic drugs shuch as analgesics, anti-convulsants, and anti-depressants are being employed for the its possible interventions. The NP has been a great interest to follow different pathophysiological mechanisms which are often considered to correlate with the metabolic pathways and its mediated disease. There is paucity of knowledge to make such mechanism via NP. Recent Finding: Most notably, recent pandemic outbreak of COVID-19 has also been reported in chronic pain mediated diabetes, inflammatory disorders, and cancers. There is an increasing incidence of NP and its complex mechanism has now led to identify the possible investigations of responsible genes and proteins via bioinformatics tools. The analysis might be more instrumental as collecting the genes from pain genetic database, analyzing the variants through differential gene expression (DEG) and constructing the protein-protein interaction (PPI) networks and thereby determining their upregulating and downregulating pathways. Summary: This review sheds a bright light towards several mechanisms at both cellular and molecular level, correlation of NP-mediated disease mechanism and possible cell surface biomarkers (receptors), and identified genes could be more promising for their pharmacological targets.

Targeting Viral Ion Channels: A Promising Strategy to Curb SARS-CoV-2.

SARS-CoV-2 is the etiological agent COVID-19, one of the most impactful health crises afflicting humanity in recent decades. While research advances have yielded several treatment and prevention options, the pandemic is slow to abate, necessitating an expansion of our treatment arsenal. As a member of the coronaviridae, SARS-CoV-2 contains several ion channels, of which E and 3a are the best characterized. Since ion channels as a family are excellent drug targets, we sought to inhibit both viroporins as a means to curb infectivity. In a previous targeted study, we identified several blockers to each channel from an extensive drug repurposing library. Herein, we examined the ability of said compounds on the whole virus in cellulo. Gratifyingly, many of the blockers exhibited antiviral activity in a stringent assay examining protection from viral-driven death. In particular, darapladib and flumatinib, both 3a blockers, displayed potent antiviral activity. Furthermore, appreciable synergism between flumatinib and several E blockers was identified in a concentration regime in which the compounds are present in human plasma following oral administration. Taken together, targeting ion channels represents a promising approach to both augment and complement our antiviral arsenal against COVID-19.

Detecting sars-cov-2 orf3a and e ion channel activity in covid-19 blood samples

Introduction: SARS-CoV-2 has been found in the heart of COVID-19 patients. It is unclear how the virus passes from the upper respiratory tract to the myocardium. Hypothesis: SARS-CoV-2 is present in the blood of COVID-19 infected patients. Methods: We targeted two viropotins, Orf3a and E, in SARS-CoV-2. Orf3a and E form non-voltagegated ion channels. A combined fluorescence potassium ion assay with three channel modulators (4-aminopyridine, emodin-Orf3a channel blocker, gliclazide-E channel blocker) was developed to detect SARS-CoV-2 Orf3a/E channel activity. In blood samples, we subtracted the fluorescence signals in the absence and presence of emodin/gliclazide to detect Orf3a and E channel activity. Results: In lentivirus spiked samples, we detected significant channel activity of Orf3a/E based on increase in fluorescence induced by 4-aminopyridine, and this increase in fluorescence was inhibited by emodin and gliclazide. In 18 antigen/PCR positive samples, our test results found 15 are positive, demonstrating 83.3% concordance. In 24 antigen/PCR negative samples, our test results found 21 are negative, showing 87.5% concordance. Conclusions: We developed a cell-free, rapid, and high-throughput test that can detect Orf3a/E channel activity of SARS-CoV-2 in blood samples from COVID-19 infected individuals, which provides a likely explanation that the virus spreads to the heart via blood circulation.

Efficacy of Ion-Channel Inhibitors Amantadine, Memantine and Rimantadine for the Treatment of SARS-CoV-2 In Vitro.

We report the in vitro efficacy of ion-channel inhibitors amantadine, memantine and rimantadine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In VeroE6 cells, rimantadine was most potent followed by memantine and amantadine (50% effective concentrations: 36, 80 and 116 µM, respectively). Rimantadine also showed the highest selectivity index, followed by amantadine and memantine (17.3, 12.2 and 7.6, respectively). Similar results were observed in human hepatoma Huh7.5 and lung carcinoma A549-hACE2 cells. Inhibitors interacted in a similar antagonistic manner with remdesivir and had a similar barrier to viral escape. Rimantadine acted mainly at the viral post-entry level and partially at the viral entry level. Based on these results, rimantadine showed the most promise for treatment of SARS-CoV-2.