Advances in Human Biology

: 2022  |  Volume : 12  |  Issue : 2  |  Page : 114--119

The role of severe acute respiratory syndrome coronavirus 2 viroporins in inflammation

Arghavan Zebardast, Tayebeh Latifi, Jila Yavarian 
 Department of Virology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran

Correspondence Address:
Jila Yavarian
Department of Virology, School of Public Health, Tehran University of Medical Sciences, Tehran


In December 2019, genomic screening of clinical samples from patients with viral pneumonia in Wuhan, China, revealed the presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). COVID-19 is the official name for the disease caused by this virus, according to the World Health Organization. SARS-CoV-2 can activate the NLRP3 inflammasome directly in apoptosis-associated speck-like protein (ASC)-dependent or independent manner through several proteins, including viroporins. Viroporins are viral proteins with ion channel functions that play crucial roles in different aspects of virus replication and pathogenesis. SARS-CoV-2 viroporins encoded by Open Reading Frame (ORF) 3a, ORF8 and the E gene activate the NLRP3 inflammasome and trigger the cleavages of pro-interleukin 1 β (IL1 β) and pro-IL18 by the caspase enzyme and convert them to the mature form (IL-1 β, IL18). Most of the inflammation in severe COVID-19 patients is caused by the activation of inflammasomes. Studies revealed that SARS-CoV-2 viroporins could be the possible targets for therapeutic interventions.

How to cite this article:
Zebardast A, Latifi T, Yavarian J. The role of severe acute respiratory syndrome coronavirus 2 viroporins in inflammation.Adv Hum Biol 2022;12:114-119

How to cite this URL:
Zebardast A, Latifi T, Yavarian J. The role of severe acute respiratory syndrome coronavirus 2 viroporins in inflammation. Adv Hum Biol [serial online] 2022 [cited 2022 Aug 19 ];12:114-119
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In December 2019, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was discovered for the first time in Wuhan, China.[1] SARS-CoV-2 spreads quickly in China and other nations and caused an epidemic disease. As SARS-CoV-2 seriously threatened world health and claimed many lives, the World Health Organization declared COVID-19 as a pandemic on 11 March 2020.[2] The new coronavirus is a member of the Beta-coronavirus genus that shares similarities to SARS-CoV.[3],[4]

Host cells directly infected by SARS-CoV-2 and the virus replication cycle resulted in increased inflammatory responses by different mechanisms.[5],[6] Viroporins have different amino acid lengths, for example, Open Reading Frame (ORF) 3a is the largest accessory protein with 275 amino acids, but the E protein is a small envelope protein that is composed of 75 amino acids.[7],[8] Viroporins also contain highly hydrophobic domains that form an amphipathic alpha-helix.[9] While many viroporins are not needed for viral replication, their presence significantly boosts virus particle formation.[10],[11],[12],[13] They communicate directly with membranes and form pores to enhance the transport of ions and small molecules across cell membrane.[14],[15] Studies showed that viroporins have crucial roles in severe COVID-19 inflammations and prompt infected cells to death.[16],[17] Increased production of pro-inflammatory cytokines is the main cause of ARDS development, lung injury and death.[18],[19] In human primary monocytes, SARS-CoV-2 infection causes pyroptosis-induced lytic cell death, which may contribute to the increased inflammatory response and leukocytopenia seen in patients with severe COVID-19 infection.[20] In addition, the pathogenesis and pathophysiology of autoimmune disorders, infectious diseases and neurodegenerative diseases are all linked to abnormal inflammasome activation.[21] SARS-CoV-2 encodes three viroporins, including ORF3a, E and ORF8a, which can modify the permeability of the host cell membranes to facilitate viral assembly and release, and they are considered as virulence factors.[22] These viroporins can be the potential targets for antiviral therapies.[23],[24] In this review, we try to summarise the role of SARS-CoV-2 viroporins in COVID-19 inflammation.

 Severe Acute Respiratory Syndrome Coronavirus 2

Coronaviruses are pleomorphic RNA viruses and belong to the nidovirales order, which comprises the cornidovirineae suborder that contains the coronaviridae family.[25] There are four genera of coronaviruses in the coronaviridae family known as alpha-coronaviruses, beta-coronaviruses, gamma-coronaviruses and delta-coronaviruses.[26] The novel beta-coronavirus has been reported in Wuhan, Hubei province, China and is called SARS-CoV-2. This virus causes coronavirus disease 2019 (COVID-19), a disease that may affect the lung tissue and airways.[27]

SARS-CoV-2 has a single-stranded positive-sense RNA genome that is approximately 30 kb.[28] It contains 29 ORFs that encode 16 non-structural (NSP1-NSP16), four structural including spike (S), envelope (E), membrane (M) and nucleocapsid (N) and nine accessory proteins (ORF3a, ORF3b, ORF6, ORF7a, ORF7b, ORF8, ORF9b, ORF9c and ORF10).[29],[30] The viral accessory proteins are involved in ion channel activity, morphogenesis, virus release and pathogenesis.[31]

SARS-CoV-2 encodes three viroporins, including ORF3a, E and ORF8a, which can alter the host cell membrane permeability to promote viral assembly and release. These viroporins can act as virulence factors by modifying the NOD-, leucine-rich repeat (LRR)- and pyrin domain-containing protein 3 (NLRP3) inflammasomes pathways. A dysregulated NLRP3 inflammasome activity by viral proteins can result in severe COVID-19 with tissue damage and a cytokine storm in patients with reduced immune fitness.[32] The cytokine storm is one of the pathological outcomes of this infection which occurs when the immune system overproduces inflammatory cytokines as a result of infection and a lack of negative feedback.[33] The inflammatory response in COVID-19 patients is an antiviral mechanism, but a powerful cytokine storm triggered by an unbalanced response can be very harmful to the patients. On the other hand, the overactivation of the immune response to SARS-CoV-2 infection can result in the severity of COVID-19.[34]

 Severe Acute Respiratory Syndrome Coronavirus 2 Open Reading Frame 3a

Enveloped viruses, like SARS-CoV-2, have viroporins inserted into membranes, and by transferring ions through membranes, they destroy chemoelectrical barriers.[35] ORF3a is the gene that encodes protein ORF3a, the largest of the three viroporins with 275 amino acids.[36] It has 72.4% sequence identity and 85.1% sequence similarity with the SARS-CoV ORF3a protein.[37] ORF3a is a multipass membrane protein that has two domains: a transmembrane domain (TMD) at the N-terminus and a cytosolic domain at the C-terminus (CM). ORF3a interacts with structural proteins S, E and M and facilitates virus spread by helping scatter membrane for cell lysis and virus release.[14],[38],[39] Furthermore, caveolin interacts with this protein, possibly controlling various stages of the viral cycle.[40] SARS-CoV-2 infection elicited strong CD4+ and CD8+ T cell responses against ORF3a in infected individuals.[41]

ORF3a contains a tumour necrosis factor receptor-associated factor 3-binding motif that activates the NLRP3 inflammasome and is a strong inducer of pro-IL1 β gene transcription.[42] This viral accessory protein activates the inflammasome in both ASC-dependent and independent modes by promoting IL-1β expression through NF-Kb.[43],[44] The inflammasome is a multiprotein complex that plays a role in inflammation. It regulates caspase-1 activation and processing of the pro-inflammatory cytokines IL-1 β and IL-18 during the innate immune response. The ORF3a protein of the SARS-CoV-2 primes and activates the inflammasome by effluxing potassium ions and oligomerising NEK7 and NLRP3.[16] Upon this oligomerisation, pro-caspase 1 will be recruited. The release of pro-inflammatory cytokines, including IL-1 β and IL18, is then mediated by caspase-1 [Dure 1].[43],[44]

An extraordinarily high level of inflammatory cytokines such as IL-1 β in severe COVID-19 patients characterises the increased immune response. An exacerbated immune response has been suggested as a major factor in these patients' poor outcomes.[45],[46],[47],[48] Higher SARS-CoV-2 infection and mortality rates are linked to mutations in the ORF3a protein.[37] Since ORF3a's ability to activate caspase-1, the main mediator of pro-inflammatory responses, is dependent on NLRP3, this pathway can be blocked in infected cells using a selective inhibitor of NLRP3 for therapeutic aims[16] [Table 1].{Table 1}

 Severe Acute Respiratory Syndrome Coronavirus 2 Open Reading Frame 8

SARS-CoV-2 ORF8 gene encodes two proteins, ORF8a with 39 aa and ORF8b with 84 aa.[53] The ORF8a protein in SARS-CoV2 human infected cells is the result of a 29-nt deletion in ORF8 that occurred after the virus crossed species.[54] The ORF8b protein strongly activates the NLRP3 inflammasome in macrophages and lung epithelial cells.[55] This protein interacts directly with the LRR domain of NLRP3 and forms cytosolic dot-like structures with NLRP3 and ASC, which causes cell death in macrophages similar to pyroptotic cell death [Figure 1].[55]{Figure 1}

In SARS-CoV and SARS-CoV-2 infections, activating NLRP3 inflammasome pathways in patients cause acute respiratory distress syndrome and, eventually, death.[49] ORF8a also induces apoptosis through a mitochondrion-dependent pathway.[56] The full-length E and 3a proteins are essential for SARS-CoV replication and virulence, while viroporin 8a had only a minor impact on these processes.[23] Inhibition of the ORF8 function could be used as a tactic to increase SARS-CoV-2 surveillance and speed up eradication[57] [Table 1].

 Severe Acute Respiratory Syndrome Coronavirus 2 E protein

The E protein is the smallest of the main structural proteins in coronaviruses that are found on the viral envelope. This protein monomer can oligomerise to form a viroporin, which is an ion channel protein.[58] Besides viroporin activity, the E protein can participate in viral morphogenesis, assembly and budding.[59] The protein contains 74–109 amino acids and 8.4–109 kDa and has three regions: N-terminal negatively charged, TMD not recharged and C-terminal (CT) negatively charged.[60] It has several motifs, one of these motifs is a β-coil-β-motif which is a conserved proline residue in the CT region of the E protein and has a key role in the maturation and targeting of the protein in the Golgi. It has been shown that mutation in this residue prevents the assembly and release of virus particles.[61] A PDZ-binding motif (PBM) is another residue in the CT region of E protein with a critical role in pathogenicity by interactions with cell host factors such as the B-cell lymphoma extra-large protein, caenorhabditis elegans lin-7 protein 1 (PALS1); syntenin (an adaptor-like molecule with PDZ domains), sodium/potassium (Na+/K+) ATPase α-1 subunit, and stomatin with interfering in cell signalling.[62],[63]

In endoplasmic-reticulum–Golgi intermediate compartment (ERGIC) membranes, the SARS-CoV E protein forms protein-lipid channels that are permeable to calcium ions. This ion-channel activity promotes NLRP3 inflammasome activation and results in IL-1 β overproduction, which leads to immunopathological effects and worsens the disease [Figure 1].[52] Based on the GISAID database, from 4085 SARS-CoV-2 genomes, more than 40 amino acid mutations in the E gene were discovered. It shows the high mutation rates of the E gene.[50]

Several studies have been demonstrating that the interaction of E protein with host factors leads to increasing the virus pathogenicity. The interaction of E protein with PALSI disrupts tight junctions in the lungs and causes the SARS-CoV-2 to become more pathogenic than other coronaviruses.[64] Furthermore, the association of E with syntenin leads to the production of inflammatory cytokines that may contribute to tissue damage.[63] Given the critical role of E protein in virus assembly and pathogenicity, the E has the potential to be a target for antiviral therapy in COVID-19 patients, as some studies have shown that Gliclazide, Memantine and Retinol can inhibit E protein channel activity[45],[65] [Table 1].

 Viroporins Interactions

Protein-protein interactions are frequently used by viroporins and cellular IC proteins to cluster ICs at appropriate places in the cell.[66],[67],[68] PDZ domains and PBMs, peptide sequences that are most commonly found at the C terminus of IC proteins, mediate these interactions.[69],[70] During morphogenesis, the CT domain of the CoV E protein interacts with the viral membrane (M) protein. A PBM in the E protein sequence is important in interactions with cellular proteins and pathogenicity.[15] The interaction of protein 3a PBM with cellular PDZ proteins most likely results in a non-pathogenic signalling pathway for the host.[23] Furthermore, ORF7a and ORF3 may have a synergistic effect on ORF3 protein expression.[71] It has been discovered that these viroporins oligomerise and create holes during viral infections, disrupting normal physiological homeostasis in the host cell and so contributing to viral pathogenicity.[35],[42],[72] Two viroporins, the more dominant protein E and ORF3a, each with a PBM and IC activity, are essential for optimum viral replication in SARS-CoV. ORF3a and E are both needed for viral replication and pathogenicity.[23]

Several CoVs encode two viroporins,[73],[74],[75] including Middle East respiratory syndrome coronavirus, human coronavirus (HCoV)-229E, HCoV-OC43 and porcine epidemic diarrhoea virus, while SARS-CoV-1 and SARS-CoV-2 encode three proteins 3a, E and 8.[22],[23],[76],[77] Only three amino acid changes and one deletion distinguish the E protein of SARS-CoV-2 (T55S, V56F, E69R and G70-GAP) from SARS-COV-1.[78] When compared to the E protein of SARS-CoV, four mutations (including one deletion mutation) in the C-terminus of the SARS-CoV-2 E protein at positions 56, 57, 69 and 70 include an extra amino acid with an alkaline R group.[79] These mutations in the C-terminus of the SARS-CoV-2 E protein could disrupt the E protein's interaction with the host protein.[6] Regarding ORF3a, the sequence of the 3a protein was found to be 97.82% identical to the non-structural protein NS3 of the bat coronavirus RaTG13. SARS-CoV-2 ORF3a signature mutations cause isolates to cluster into established phylogenetic clades. Researchers discovered six functional domains (I to VI) in SARS-CoV-2. Virulence, infectivity, ion channel creation and virus release were all linked to the functional domains.[31] SARS-CoV-2 may encode an ORF8 protein that is similar in length to the full-length ORF8 seen in early SARS-Cov isolates, but its identity (32%) is significantly lower than that of the other proteins.[80]

Because many viruses have been discovered to have ion channels, inhibiting these proteins could be a promising avenue for antiviral medication development.[81] Only one class of chemicals, anti-flu aminoadamantanes, has been licensed as an antiviral medication so far.[82] In COVID-19 patients with cardiovascular illness, targeted suppression of the SARS-CoV-2 E viroporin can minimise the risk of sudden cardiac death and heart injury. Hexamethylene amiloride and amantadine, as well as their combinations, could be used to target the pentameric E protein channels.[77] Furthermore, ORF8 and ORF3a could be another promising therapeutic targets for disease treatment.[82],[83],[84] Inhibition of the ORF8 function could be used as a tactic to increase SARS-CoV-2 surveillance and speed up eradication.[85]


SARS-CoV-2 accessory proteins such as ORF3a, ORF8 and structural E proteins are critical in COVID-19 pathogenesis by manipulating host immune mechanisms such as NLRP3 inflammasome pathways and producing inflammatory cytokines such as IL-1 β. Different COVID-19 studies around the world suggest that some viroporin inhibitors are thought to be equally efficient in blocking the SARS-CoV-2 viroporins. Effective treatment of cytokine storms, specifically in the 2nd week of disease, would necessitate both antiviral and anti-inflammatory strategies. However, to determine the antiviral activity of the various blockers and the dose-response characteristics of these viroporins for the tested inhibitors, more future in vitro and in vivo investigations will be required to improve the COVID-19 patients' outcomes.

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1Amirfakhryan H, Safari F. Outbreak of SARS-CoV2: Pathogenesis of infection and cardiovascular involvement. Hellenic J Cardiol 2021;62:13-23.
2Organization WH. WHO Director-General's Statement on ihr Emergency Committee on Novel Coronavirus (2019-nCoV). Geneva: World Health Organization; 2020.
3Pal M, Berhanu G, Desalegn C, Kandi V. Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2): An update. Cureus 2020;12:e7423.
4Machado C, Gutierrez JV. Brainstem Dysfunction in SARS-COV2 Infection Can Be a Potential Cause of Respiratory Distress. Preprints 2020, 2020040330. [doi: 10.20944/preprints202004.0330.v1].
5Lega S, Naviglio S, Volpi S, Tommasini A. Recent insight into SARS-CoV2 immunopathology and rationale for potential treatment and preventive strategies in COVID-19. Vaccines (Basel) 2020;8:224.
6Aguirre García MM, Mancilla-Galindo J, Paredes-Paredes M, Tiburcio ÁZ, Ávila-Vanzzini N. Mechanisms of infection by SARS-CoV-2, inflammation and potential links with the microbiome. Future Virology 2021;16.1:43-57.
7Azad GK, Khan PK. Variations in Orf3a protein of SARS-CoV-2 alter its structure and function. Biochem Biophys Rep 2021;26:100933.
8Chai J, Cai Y, Pang C, Wang L, McSweeney S, Shanklin J, et al. Structural basis for SARS-CoV-2 envelope protein recognition of human cell junction protein PALS1. Nat Commun 2021;12:3433.
9González ME, Carrasco L. Viral proteins that enhance membrane permeability. In: Viral Membrane Proteins: Structure, Function, and Drug Design .Microbes and infection: Springer; 2020;22.10:592-7.
10Hatta M, Kawaoka Y. The NB protein of influenza B virus is not necessary for virus replication in vitro. J Virol 2003;77:6050-4.
11Klimkait T, Strebel K, Hoggan MD, Martin MA, Orenstein JM. The human immunodeficiency virus type 1-specific protein vpu is required for efficient virus maturation and release. J Virol 1990;64:621-9.
12Loewy A, Smyth J, Von Bonsdorff C, Liljeström P, Schlesinger MJ. The 6-kilodalton membrane protein of Semliki Forest virus is involved in the budding process. J Virol 1995;69:469-75.
13Watanabe T, Watanabe S, Ito H, Kida H, Kawaoka Y. Influenza A virus can undergo multiple cycles of replication without M2 ion channel activity. J Virol 2001;75:5656-62.
14Gonzalez ME, Carrasco L. Viroporins. FEBS Lett 2003;552:28-34.
15Nieto-Torres JL, Verdiá-Báguena C, Castaño-Rodriguez C, Aguilella VM, Enjuanes L. Relevance of viroporin ion channel activity on viral replication and pathogenesis. Viruses 2015;7:3552-73.
16Xu H, Chitre SA, Akinyemi IA, Loeb JC, Lednicky JA, McIntosh MT, et al. SARS-CoV-2 viroporin triggers the NLRP3 inflammatory pathway. BioRxiv 2020;[in print]. [doi: 101101/20201027357731].
17To J, Surya W, Torres J. Targeting the channel activity of viroporins. Adv Protein Chem Struct Biol 2016;104:307-55.
18Sepehrinezhad A, Gorji A, Sahab Negah S. SARS-CoV-2 may trigger inflammasome and pyroptosis in the central nervous system: A mechanistic view of neurotropism. Inflammopharmacology 2021;29:1049-59.
19Gallelli L, Zhang L, Wang T, Fu F. Severe acute lung injury related to COVID-19 infection: A review and the possible role for escin. J Clin Pharmacol 2020;60:815-25.
20Cheon SY, Koo BN. Inflammatory response in COVID-19 patients resulting from the interaction of the inflammasome and SARS-CoV-2. Int J Mol Sci 2021;22:7914.
21Voet S, Srinivasan S, Lamkanfi M, van Loo G. Inflammasomes in neuroinflammatory and neurodegenerative diseases. EMBO Mol Med 2019;11:e10248.
22Kern DM, Sorum B, Mali SS, Hoel CM, Sridharan S, Remis JP, et al. Cryo-EM structure of the SARS-CoV-2 3a ion channel in lipid nanodiscs. Nature Structural & Molecular Biology (2021): 1-10. [doi: 101101/20200617156554].
23Castaño-Rodriguez C, Honrubia JM, Gutiérrez-Álvarez J, DeDiego ML, Nieto-Torres JL, Jimenez-Guardeño JM, et al. Role of severe acute respiratory syndrome coronavirus viroporins E, 3a, and 8a in replication and pathogenesis. mBio 2018;9:e02325-17.
24Scott C, Griffin S. Viroporins: Structure, function and potential as antiviral targets. J Gen Virol 2015;96:2000-27.
25ICTV. Virus Taxonomy: 2014 Release. London: ICTV; 2014.
26Fu Y, Pistolozzi M, Yang X, Lin Z. A comprehensive classification of coronaviruses and inferred cross-host transmissions. bioRxiv [In print]. [doi: 101101/20200811232520].
27Tang X, Wu C, Li X, Song Y, Yao X, Wu X, et al. On the origin and continuing evolution of SARS-CoV-2. Natl Sci Rev 2020;7:1012-23.
28Wu F, Zhao S, Yu B, Chen YM, Wang W, Song ZG, et al. A new coronavirus associated with human respiratory disease in China. Nature 2020;579:265-9.
29Khailany RA, Safdar M, Ozaslan M. Genomic characterization of a novel SARS-CoV-2. Gene Rep 2020;19:100682.
30Malik YA. Properties of coronavirus and SARS-CoV-2. Malays J Pathol 2020;42:3-11.
31Issa E, Merhi G, Panossian B, Salloum T, Tokajian S. SARS-CoV-2 and ORF3a: Nonsynonymous mutations, functional domains, and viral pathogenesis. mSystems 2020;5:e00266-20.
32van den Berg DF, Te Velde AA. Severe COVID-19: NLRP3 inflammasome dysregulated. Front Immunol 2020;11:1580.
33Ding Y, Wang H, Shen H, Li Z, Geng J, Han H, et al. The clinical pathology of severe acute respiratory syndrome (SARS): A report from China. J Pathol 2003;200:282-9.
34Song P, Li W, Xie J, Hou Y, You C. Cytokine storm induced by SARS-CoV-2. Clin Chim Acta 2020;509:280-7.
35Nieva JL, Madan V, Carrasco L. Viroporins: Structure and biological functions. Nat Rev Microbiol 2012;10:563-74.
36Hassan SS, Choudhury PP, Basu P, Jana SS. Molecular conservation and differential mutation on ORF3a gene in Indian SARS-CoV2 genomes. Genomics 2020;112:3226-37.
37Majumdar P, Niyogi S. ORF3a mutation associated with higher mortality rate in SARS-CoV-2 infection. Epidemiol Infect 2020;148. [doi:10.1017/S0950268820002599].
38Tomaszewski T, DeVries RS, Dong M, Bhatia G, Norsworthy MD, Zheng X, et al. New pathways of mutational change in SARS-CoV-2 proteomes involve regions of intrinsic disorder important for virus replication and release. Evol Bioinform 2020;16:1176934320965149.
39Tang X, Li G, Vasilakis N, Zhang Y, Shi Z, Zhong Y, et al. Differential stepwise evolution of SARS coronavirus functional proteins in different host species. BMC Evol Biol 2009;9:1-15.
40Padhan K, Tanwar C, Hussain A, Hui PY, Lee MY, Cheung CY, et al. Severe acute respiratory syndrome coronavirus Orf3a protein interacts with caveolin. J Gen Virol 2007;88:3067-77.
41Grifoni A, Weiskopf D, Ramirez SI, Mateus J, Dan JM, Moderbacher CR, et al. Targets of T cell responses to SARS-CoV-2 coronavirus in humans with COVID-19 disease and unexposed individuals. Cell 2020;181:1489-501.e15.
42Siu KL, Yuen KS, Castano-Rodriguez C, Ye ZW, Yeung ML, Fung SY, et al. Severe acute respiratory syndrome Coronavirus ORF3a protein activates the NLRP3 inflammasome by promoting TRAF3-dependent ubiquitination of ASC. FASEB J 2019;33:8865-77.
43Alschuler L, Weil A, Horwitz R, Stamets P, Chiasson AM, Crocker R, et al. Integrative considerations during the COVID-19 pandemic. Explore (NY) 2020;16:354-6.
44Freeman LC, Ting JP. The pathogenic role of the inflammasome in neurodegenerative diseases. J Neurochem 2016;136 Suppl 1:29-38.
45Mehta P, McAuley DF, Brown M, Sanchez E, Tattersall RS, Manson JJ. COVID-19: Consider cytokine storm syndromes and immunosuppression. Lancet 2020;395:1033-4.
46Huang C, Wang Y, Li X, Ren L, Zhao J, Hu Y, et al. Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China. Lancet 2020;395:497-506.
47Ragab D, Salah Eldin H, Taeimah M, Khattab R, Salem R. The COVID-19 cytokine storm; what we know so far. Front Immunol 2020;11:1446.
48Del Valle DM, Kim-Schulze S, Huang HH, Beckmann ND, Nirenberg S, Wang B, et al. An inflammatory cytokine signature predicts COVID-19 severity and survival. Nat Med 2020;26:1636-43.
49Asghari A, Naseri M, Safari H, Saboory E, Parsamanesh N. The novel insight of SARS-CoV-2 molecular biology and pathogenesis and therapeutic options. DNA Cell Biol 2020;39:1741-53.
50Sun YS, Xu F, An Q, Chen C, Yang ZN, Lu HJ, et al. A SARS-CoV-2 variant with the 12-bp deletion at E gene. Emerg Microbes Infect 2020;9:2361-7.
51De Maio F, Cascio EL, Babini G, Sali M, Della Longa S, Tilocca B, et al. Enhanced binding of SARS-CoV-2 envelope protein to tight junction-associated PALS1 could play a key role in COVID-19 pathogenesis. Microbes and infection 2020;22.10:592-7.
52Nieto-Torres JL, Verdiá-Báguena C, Jimenez-Guardeño JM, Regla-Nava JA, Castaño-Rodriguez C, Fernandez-Delgado R, et al. Severe acute respiratory syndrome coronavirus E protein transports calcium ions and activates the NLRP3 inflammasome. Virology 2015;485:330-9.
53Zinzula L. Lost in deletion: The enigmatic ORF8 protein of SARS-CoV-2. Biochem Biophys Res Commun 2021;538:116-24.
54Oostra M, Hagemeijer MC, van Gent M, Bekker CP, te Lintelo EG, Rottier PJ, et al. Topology and membrane anchoring of the coronavirus replication complex: Not all hydrophobic domains of nsp3 and nsp6 are membrane spanning. J Virol 2008;82:12392-405.
55Shi CS, Nabar NR, Huang NN, Kehrl JH. SARS-Coronavirus Open Reading Frame-8b triggers intracellular stress pathways and activates NLRP3 inflammasomes. Cell Death Discov 2019;5:101.
56Chen CY, Ping YH, Lee HC, Chen KH, Lee YM, Chan YJ, et al. Open reading frame 8a of the human severe acute respiratory syndrome coronavirus not only promotes viral replication but also induces apoptosis. J Infect Dis 2007;196:405-15.
57Su YC, Anderson DE, Young BE, Linster M, Zhu F, Jayakumar J, et al. Discovery and genomic characterization of a 382-nucleotide deletion in ORF7b and ORF8 during the early evolution of SARS-CoV-2. mBio 2020;11:e01610-20.
58Schoeman D, Fielding BC. Coronavirus envelope protein: Current knowledge. Virol J 2019;16:69.
59DeDiego ML, Nieto-Torres JL, Jimenez-Guardeño JM, Regla-Nava JA, Castaño-Rodriguez C, Fernandez-Delgado R, et al. Coronavirus virulence genes with main focus on SARS-CoV envelope gene. Virus Res 2014;194:124-37.
60Nieto-Torres JL, Dediego ML, Alvarez E, Jiménez-Guardeño JM, Regla-Nava JA, Llorente M, et al. Subcellular location and topology of severe acute respiratory syndrome coronavirus envelope protein. Virology 2011;415:69-82.
61Cohen JR, Lin LD, Machamer CE. Identification of a Golgi complex-targeting signal in the cytoplasmic tail of the severe acute respiratory syndrome coronavirus envelope protein. J Virol 2011;85:5794-803.
62Javier RT, Rice AP. Emerging theme: Cellular PDZ proteins as common targets of pathogenic viruses. J Virol 2011;85:11544-56.
63Jimenez-Guardeño JM, Nieto-Torres JL, DeDiego ML, Regla-Nava JA, Fernandez-Delgado R, Castaño-Rodriguez C, et al. The PDZ-binding motif of severe acute respiratory syndrome coronavirus envelope protein is a determinant of viral pathogenesis. PLoS Pathog 2014;10:e1004320.
64De Maio F, Lo Cascio E, Babini G, Sali M, Della Longa S, Tilocca B, et al. Improved binding of SARS-CoV-2 envelope protein to tight junction-associated PALS1 could play a key role in COVID-19 pathogenesis. Microbes Infect 2020;22:592-7.
65Liu Y, Yan LM, Wan L, Xiang TX, Le A, Liu JM, et al. Viral dynamics in mild and severe cases of COVID-19. Lancet Infect Dis 2020;20:656-7.
66Piserchio A, Spaller M, Mierke DF. Targeting the PDZ domains of molecular scaffolds of transmembrane ion channels. AAPS J 2006;8:E396-401.
67Feng W, Zhang M. Organization and dynamics of PDZ-domain-related supramodules in the postsynaptic density. Nat Rev Neurosci 2009;10:87-99.
68Guggino WB, Stanton BA. New insights into cystic fibrosis: Molecular switches that regulate CFTR. Nat Rev Mol Cell Biol 2006;7:426-36.
69Hung AY, Sheng M. PDZ domains: Structural modules for protein complex assembly. J Biol Chem 2002;277:5699-702.
70Münz M, Hein J, Biggin PC. The role of flexibility and conformational selection in the binding promiscuity of PDZ domains. PLoS Comput Biol 2012;8:e1002749.
71Fang P, Fang L, Zhang H, Xia S, Xiao S. Functions of coronavirus accessory proteins: Overview of the state of the art. Viruses 2021;13:1139.
72Torres J, Maheswari U, Parthasarathy K, Ng L, Liu DX, Gong X. Conductance and amantadine binding of a pore formed by a lysine-flanked transmembrane domain of SARS coronavirus envelope protein. Protein Sci 2007;16:2065-71.
73Zhang R, Wang K, Lv W, Yu W, Xie S, Xu K, et al. The ORF4a protein of human coronavirus 229E functions as a viroporin that regulates viral production. Biochim Biophys Acta 2014;1838:1088-95.
74Zhang R, Wang K, Ping X, Yu W, Qian Z, Xiong S, et al. The ns12.9 accessory protein of human coronavirus OC43 is a viroporin involved in virion morphogenesis and pathogenesis. J Virol 2015;89:11383-95.
75Wang K, Lu W, Chen J, Xie S, Shi H, Hsu H, et al. PEDV ORF3 encodes an ion channel protein and regulates virus production. FEBS Lett 2012;586:384-91.
76Flower TG, Buffalo CZ, Hooy RM, Allaire M, Ren X, Hurley JH. Structure of SARS-CoV-2 ORF8, a rapidly evolving immune evasion protein. Proc Natl Acad Sci U S A 2021;118:e2021785118.
77Cao Y, Yang R, Lee I, Zhang W, Sun J, Wang W, et al. Characterization of the SARS-CoV-2 E Protein: Sequence, structure, viroporin, and inhibitors. Protein Sci 2021;30:1114-30.
78Tilocca B, Soggiu A, Sanguinetti M, Babini G, De Maio F, Britti D, et al. Immunoinformatic analysis of the SARS-CoV-2 envelope protein as a strategy to assess cross-protection against COVID-19. Microbes Infect 2020;22:182-7.
79Li S, Yuan L, Dai G, Chen RA, Liu DX, Fung TS. Regulation of the ER stress response by the ion channel activity of the infectious bronchitis coronavirus envelope protein modulates virion release, apoptosis, viral fitness, and pathogenesis. Front Microbiol 2019;10:3022.
80Cagliani R, Forni D, Clerici M, Sironi M. Coding potential and sequence conservation of SARS-CoV-2 and related animal viruses. Infect Genet Evol 2020;83:104353.
81Singh Tomar PP, Arkin IT. SARS-CoV-2 E protein is a potential ion channel that can be inhibited by Gliclazide and Memantine. Biochem Biophys Res Commun 2020;530:10-4.
82Tomar PP, Krugliak M, Arkin IT. Blockers of the SARS-CoV-2 3a channel identified by targeted drug repurposing. Viruses 2021;13:532.
83Arya R, Kumari S, Pandey B, Mistry H, Bihani SC, Das A, et al. Structural insights into SARS-CoV-2 proteins. J Mol Biol 2021;433:166725.
84Meinberger D, Koch M, Roth A, Hermes G, Stemler J, Cornely OA, et al. Analysis of IgM, IgA, and IgG isotype antibodies directed against SARS-CoV-2 spike glycoprotein and ORF8 in the course of COVID-19. Sci Rep 2021;11:8920.
85Zhang Y, Chen Y, Li Y, Huang F, Luo B, Yuan Y, et al. The ORF8 protein of SARS-CoV-2 mediates immune evasion through down-regulating MHC-I. Proc Natl Acad Sci 2021;118:e2024202118.