The ORF8 protein of SARS-CoV-2 induced endoplasmic reticulum stress and mediated immune evasion by antagonizing production of interferon beta

Abstract

The open reading frame 8 (orf8) is an accessory protein of SARS-CoV-2. It has 121 amino acids with two genotypes, orf8L and orf8S. In this study, we overexpressed the orf8L and orf8S of SARS-CoV-2 as well as the orf8b of SARS-CoV to investigate their roles in the regulation of endoplasmic reticulum (ER) stress and the inhibition of interferon beta (IFNß) production. We found that the two genotypes of SARS-CoV-2 orf8 are capable of inducing ER stress without significant difference by triggering the activating transcription factor 6 (ATF6) and inositol-requiring enzymes 1 (IRE1) branches of the ER stress pathway. However, the third branch of ER stress pathway, i.e. the protein kinase-like ER kinase (PERK), was unaffected by the overexpression of SARS-CoV-2 orf8L or orf8S. Moreover, both orf8L and orf8S of SARS-CoV-2 are capable of down regulating the production of IFNß and interferon-stimulated genes (ISG), ISG15 and ISG56 induced by polyinosinic-polycytidylic acid (poly (I:C)). Moreover, we also found decreased nuclear translocation of Interferon regulatory factor 3 (IRF3), after overexpressing orf8L and orf8S induced by poly (I:C). Our data demonstrated that SARS-CoV-2 orf8 protein could induce ER stress by activating the ATF6 and IRE1 pathways, but not the PERK pathway, and functions as an interferon antagonist to inhibit the production of IFNß. However, these functions appeared not to be affected by the genotypes of SARS-CoV-2 orf8L and orf8S.

A Novel SARS-CoV-2 Viral Sequence Bioinformatic Pipeline Has Found Genetic Evidence That the Viral 3′ Untranslated Region (UTR) Is Evolving and Generating Increased Viral Diversity

“…Regardless the fact that all genomes from B.1.1.7 lineage contain the Q27 ∗ variant, around 14% of these genomes contain another downstream stop codon, Q68 ∗ ( Figure 3E ), confirming that ORF8 is prone to accumulate non-sense variants and B.1.1.7 lineage transmits successfully without expression of ORF8. ORF8 from SARS-CoV-2 has been shown to accumulate in the endoplasmic reticulum (ER) and activate an ER-mediated stress response that cause immune evasion via downregulation of the expression of interferon beta ( Rashid et al, 2021 ) and the major histocompatibility complex I ( Zhang Y. et al, 2020 ). Also, along with ORF3b, it is responsible for initiating an early antibody response in the host ( Hachim et al, 2020 ).…”

An Issue of Concern: Unique Truncated ORF8 Protein Variants of SARS-CoV-2

“…ORF8 is 121-amino-acid with two genotypes (orf8L and orf8S), Ig-Like fold, highly immunogenic, SARS-CoV-2 protein interacting with 47 human proteins 15 of them are drug targeting was noticed to interact with MHC-I molecules and significantly down-regulate their surface expression on various cell types [16,46,47]. As a result, it was proposed that inhibiting ORF8 function could boost special immune surveillance and speed up SARS-CoV-2 eradication in vivo [47].…”

“…It directly interacts with major histocompatibility complex class I (MHC-I) both invitro and invivo, and is down-regulated, which impairs its ability to antigen presentation and rendering infected cells less sensitive to lysis by cytotoxic T lymphocytes [15]. ORF8 suppresses type I interferon antiviral responses and interacts with host factors involved in pulmonary inflammation and fibrogenesis [15,16]. From all viral proteomes interacting with human metalloproteome, the ORF8 interplay with 10 out 58 [17].…”

SARS-CoV-2 infection in the Syrian hamster model causes inflammation as well as type I interferon dysregulation in both respiratory and non-respiratory tissues including the heart and kidney

“…Dysregulation of the interferon response is a strategy employed by viruses to evade host immunity. Previous investigations of the host response to SARS-CoV (severe acute respiratory syndrome coronavirus 1) and MERS-CoV (Middle East respiratory syndrome coronavirus) infection suggest that multiple coronaviruses employ this strategy [55][56][57][58][59]. The 2020 study by Xia et al determined this dysregulation utilized by the highly pathogenic coronaviruses extends to SARS-CoV-2 by demonstrating that all three of these beta-coronaviruses downregulate the type I interferon pathway.…”