Unconventional secretion of unglycosylated ORF8 is critical for the cytokine storm during SARS-CoV-2 infection

• Published in: PLoS pathogens 2023-01, Vol.19 (1), p.e1011128-e1011128
• Main Authors: Lin, Xiaoyuan, Fu, Beibei, Xiong, Yan, Xing, Na, Xue, Weiwei, Guo, Dong, Zaky, Mohamed, Pavani, Krishna, Kunec, Dusan, Trimpert, Jakob, Wu, Haibo
• Format: Article
• Language: English
• Subjects: Alveoli; Apoptosis; Biology and life sciences; Cell culture; Cell interactions; Cellular communication; Coronaviruses; COVID-19; COVID-19 - pathology; Cytokine Release Syndrome - pathology; Cytokine storm; Cytokines; Disease transmission; Epithelial cells; Epithelium; Glycosylation; Golgi apparatus; Hamsters; Health aspects; Humans; Immune response; Infections; Infectious diseases; Inflammation; Interleukin 17; International economic relations; Life cycles; Macrophages; Medicine and health sciences; NF-κB protein; Open Reading Frames; Pathogenesis; Physiological aspects; Proteins; Research and Analysis Methods; Respiratory diseases; SARS-CoV-2 - physiology; Scientific equipment and supplies industry; Severe acute respiratory syndrome; Severe acute respiratory syndrome coronavirus 2; Signal transduction; Steric hindrance; Structural proteins; Viral diseases; Viral proteins; Viral Proteins - metabolism; Viruses
• ISSN: 1553-7374; 1553-7366; 1553-7374
• DOI: 10.1371/journal.ppat.1011128

Coronavirus disease 2019 is a respiratory infectious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Evidence on the pathogenesis of SARS-CoV-2 is accumulating rapidly. In addition to structural proteins such as Spike and Envelope, the functional roles of non-structural and accessory proteins in regulating viral life cycle and host immune responses remain to be understood. Here, we show that open reading frame 8 (ORF8) acts as messenger for inter-cellular communication between alveolar epithelial cells and macrophages during SARS-CoV-2 infection. Mechanistically, ORF8 is a secretory protein that can be secreted by infected epithelial cells via both conventional and unconventional secretory pathways. Conventionally secreted ORF8 is glycosylated and loses the ability to recognize interleukin 17 receptor A of macrophages, possibly due to the steric hindrance imposed by N-glycosylation at Asn78. However, unconventionally secreted ORF8 does not undergo glycosylation without experiencing the ER-Golgi trafficking, thereby activating the downstream NF-κB signaling pathway and facilitating a burst of cytokine release. Furthermore, we show that ORF8 deletion in SARS-CoV-2 attenuates inflammation and yields less lung lesions in hamsters. Our data collectively highlights a role of ORF8 protein in the development of cytokine storms during SARS-CoV-2 infection.