tetano
Editor, Senior Moderator
J Virol
. 2023 Mar 6;e0001123.
doi: 10.1128/jvi.00011-23. Online ahead of print.
SARS-CoV-2 ORF8 Protein Induces Endoplasmic Reticulum Stress-like Responses and Facilitates Virus Replication by Triggering Calnexin: an Unbiased Study
Xuefeng Wang[SUP] #[/SUP][SUP] 1 [/SUP], Wenqi Wang[SUP] #[/SUP][SUP] 2 3 [/SUP], Tiecheng Wang[SUP] 1 2 4 [/SUP], Jianzhong Wang[SUP] 5 [/SUP], Yuhang Jiang[SUP] 1 6 [/SUP], Xue Wang[SUP] 1 2 [/SUP], Ze Qiu[SUP] 1 2 [/SUP], Na Feng[SUP] 1 [/SUP], Weiyang Sun[SUP] 1 [/SUP], Chang Li[SUP] 1 [/SUP], Songtao Yang[SUP] 1 [/SUP], Xianzhu Xia[SUP] 1 4 [/SUP], Hongbin He[SUP] 2 [/SUP], Yuwei Gao[SUP] 1 [/SUP]
Affiliations
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the viral pathogen responsible for the worldwide coronavirus disease 2019 (COVID-19) pandemic. The novel SARS-CoV-2 ORF8 protein is not highly homologous with known proteins, including accessory proteins of other coronaviruses. ORF8 contains a 15-amino-acid signal peptide in the N terminus that localizes the mature protein to the endoplasmic reticulum. Oligomannose-type glycosylation has been identified at the N78 site. Here, the unbiased molecular functions of ORF8 are also demonstrated. Via an immunoglobulin-like fold in a glycan-independent manner, both exogenous and endogenous ORF8 interacts with human calnexin and HSPA5. The key ORF8-binding sites of Calnexin and HSPA5 are indicated on the globular domain and the core substrate-binding domain, respectively. ORF8 induces species-dependent endoplasmic reticulum stress-like responses in human cells exclusively via the IRE1 branch, including intensive HSPA5 and PDIA4 upregulation, with increases in other stress-responding effectors, including CHOP, EDEM and DERL3. ORF8 overexpression facilitates SARS-CoV-2 replication. Both stress-like responses and viral replication induced by ORF8 have been shown to result from triggering the Calnexin switch. Thus, ORF8 serves as a key unique virulence gene of SARS-CoV-2, potentially contributing to COVID-19-specific and/or human-specific pathogenesis. IMPORTANCE Although SARS-CoV-2 is basically regarded as a homolog of SARS-CoV, with their genomic structure and the majority of their genes being highly homologous, the ORF8 genes of SARS-CoV and SARS-CoV-2 are distinct. The SARS-CoV-2 ORF8 protein also shows little homology with other viral or host proteins and is thus regarded as a novel special virulence gene of SARS-CoV-2. The molecular function of ORF8 has not been clearly known until now. Our results reveal the unbiased molecular characteristics of the SARS-CoV-2 ORF8 protein and demonstrate that it induces rapidly generated but highly controllable endoplasmic reticulum stress-like responses and facilitates virus replication by triggering Calnexin in human but not mouse cells, providing an explanation for the superficially known in vivo virulence discrepancy of ORF8 between SARS-CoV-2-infected patients and mouse.
Keywords: Calnexin; ORF8; SARS-CoV-2; endoplasmic reticulum stress.
. 2023 Mar 6;e0001123.
doi: 10.1128/jvi.00011-23. Online ahead of print.
SARS-CoV-2 ORF8 Protein Induces Endoplasmic Reticulum Stress-like Responses and Facilitates Virus Replication by Triggering Calnexin: an Unbiased Study
Xuefeng Wang[SUP] #[/SUP][SUP] 1 [/SUP], Wenqi Wang[SUP] #[/SUP][SUP] 2 3 [/SUP], Tiecheng Wang[SUP] 1 2 4 [/SUP], Jianzhong Wang[SUP] 5 [/SUP], Yuhang Jiang[SUP] 1 6 [/SUP], Xue Wang[SUP] 1 2 [/SUP], Ze Qiu[SUP] 1 2 [/SUP], Na Feng[SUP] 1 [/SUP], Weiyang Sun[SUP] 1 [/SUP], Chang Li[SUP] 1 [/SUP], Songtao Yang[SUP] 1 [/SUP], Xianzhu Xia[SUP] 1 4 [/SUP], Hongbin He[SUP] 2 [/SUP], Yuwei Gao[SUP] 1 [/SUP]
Affiliations
- PMID: 36877072
- DOI: 10.1128/jvi.00011-23
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the viral pathogen responsible for the worldwide coronavirus disease 2019 (COVID-19) pandemic. The novel SARS-CoV-2 ORF8 protein is not highly homologous with known proteins, including accessory proteins of other coronaviruses. ORF8 contains a 15-amino-acid signal peptide in the N terminus that localizes the mature protein to the endoplasmic reticulum. Oligomannose-type glycosylation has been identified at the N78 site. Here, the unbiased molecular functions of ORF8 are also demonstrated. Via an immunoglobulin-like fold in a glycan-independent manner, both exogenous and endogenous ORF8 interacts with human calnexin and HSPA5. The key ORF8-binding sites of Calnexin and HSPA5 are indicated on the globular domain and the core substrate-binding domain, respectively. ORF8 induces species-dependent endoplasmic reticulum stress-like responses in human cells exclusively via the IRE1 branch, including intensive HSPA5 and PDIA4 upregulation, with increases in other stress-responding effectors, including CHOP, EDEM and DERL3. ORF8 overexpression facilitates SARS-CoV-2 replication. Both stress-like responses and viral replication induced by ORF8 have been shown to result from triggering the Calnexin switch. Thus, ORF8 serves as a key unique virulence gene of SARS-CoV-2, potentially contributing to COVID-19-specific and/or human-specific pathogenesis. IMPORTANCE Although SARS-CoV-2 is basically regarded as a homolog of SARS-CoV, with their genomic structure and the majority of their genes being highly homologous, the ORF8 genes of SARS-CoV and SARS-CoV-2 are distinct. The SARS-CoV-2 ORF8 protein also shows little homology with other viral or host proteins and is thus regarded as a novel special virulence gene of SARS-CoV-2. The molecular function of ORF8 has not been clearly known until now. Our results reveal the unbiased molecular characteristics of the SARS-CoV-2 ORF8 protein and demonstrate that it induces rapidly generated but highly controllable endoplasmic reticulum stress-like responses and facilitates virus replication by triggering Calnexin in human but not mouse cells, providing an explanation for the superficially known in vivo virulence discrepancy of ORF8 between SARS-CoV-2-infected patients and mouse.
Keywords: Calnexin; ORF8; SARS-CoV-2; endoplasmic reticulum stress.