It was observed that there was greater staining in cells which the ORF3a accessory protein was expressed indicating a potential link between ORF3a and pro-apoptotic activity seen in host cells. Further evidence on top of the staining patterns was provided by the increased rate of apoptosis seen in host cells that had the ORF3a protein expressed.

Results of Apoptosis Rate and FITC/PI Staining based on Expression of ORF3a of SARS-CoV2 of HEK293T, HepG2, and Vero E6 cells

The effect of the ORF3a protein on apoptosis was investigated by using an apoptosis staining method that involved double staining a culture of cells comprising of Vero E6, HepG2, and HEK293T cells with PI (propidium iodide) and FITC (annexin V-fluorescein 5-isothiocyanate (FITC) where increased staining indicates greater pro-apoptotic activity.

Ohio State University, Columbus

The ORF3a accessory protein has the ability to trigger apoptosis in SARS-CoV, prompting investigations into its role in SARS-CoV-2. The pro-apoptotic effect of the SARS-CoV-2 ORF3a protein was confirmed in Vero E6, HepG2, and HEK293T cells using staining methods and by tracking key molecules involved in apoptosis pathways.

Role of SARS-CoV-2 ORF3a in Inducing Apoptosis

Ren, Y., Shu, T., Wu, D. et al. The ORF3a protein of SARS-CoV-2 induces apoptosis in cells. Cell Mol Immunol 17, 881–883 (2020). https://doi.org/10.1038/s41423-020-0485-9

The ORF3a protein of SARS-CoV-2 induces apoptosis in cells

While many molecules and pathways play a role in apoptosis, in regard to ORF3a’s role in apoptosis, five key molecules need to be explored: Caspase-8, Caspase-9, Cytochrome C, Bid/t-Bid, and Bcl-2.

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