The role of SARS-CoV-2 nucleocapsid protein in effecting immune cells and insights on its molecular mechanisms
The study aims were to explore the immune regulatory function of SARA-CoV-2 Nucleocapsid (N protein) and the related mechanisms. In a series of protein activity experiments, the SARA-CoV-2 Nucleocapsid showed the proliferation effect on three immune cell lines (Raw264.7, Jurkat and Raji) in a dose-dependent manner. N protein(10µg/mL) could significantly change cell cycle progressing of these three immune cell lines and could promote Raw264.7 cells quickly entering G2/M phase from the S phase to achieve rapid growth. Additionally, N protein((10µg/mL) also could stimulate Raw264.7 cells to secrete a large number of proinflammatory factors such as TNFa, IL6 and IL10. The RNA sequencing analysis indicated that N protein changed the expression of some certain genes  significantly in immune related function and four important signaling pathways including JAK-STAT signaling pathway, TNF signaling pathway, NF-kappa B signaling pathway and MAPK signaling pathway, which suggested that N protein could not only regulate the expression of genes involved in the process of resisting virus infection in macrophages of immune system, but also change the cellular signal processing. Overall design: To investigate the effect of SARS-CoV-2 nucleocapsid protein on immune cells .Raw264.7 cells were planted in 75 cm2 cell culture tanks and treated with 10µg/mL N protein of SARS-CoV-2 or Con A (as positive control) for 24 hours. Untreated cells as blank control. Each experiment with three Biological replicates.