Fig 4. PLSCR1 is a highly effective anti-SARS-CoV-2 effector ISG contributing to intrinsic immunity in the absence of IFN.

(A) Cells were pretreated with a JAK-STAT inhibitor (InSolution 1 μM) for 2 hours, followed by IFN-ɑ2a (10 pM Huh-7.5 or 20 μM A549-ACE2) for 24 hours and were infected with SARS-CoV-2 for 24 hours followed by IF staining for viral N protein. Huh-7.5 infection using an MOI of 0.5 (titer determined by focus forming assay on Huh-7.5 WT cells). A549-ACE2 infection using an MOI of 0.01 (titer determined by focus forming assay on A549-ACE2 WT cells). The percentage of SARS-CoV-2-positive cells is plotted. n = 4 separate wells infected on the same day. (B) Cells were reconstituted with the indicated proteins by stable transduction with lentiviruses and then infected as in (A). n = 4 separate wells infected on the same day. (C) Cells were cocultured as indicated (50:50 mix) and then infected as in (A), and the % infection of each cell type was determined. n = 4 separate wells infected on the same day; ****, p ≤ 0.0001; two-tailed t test. The data underlying this Figure can be found in S1 Table. IF, immunofluorescence; IFN, interferon; ISG, IFN-stimulated gene; MOI, multiplicity of infection; PLSCR1, phospholipid scramblase 1; SARS-CoV-2, Severe Acute Respiratory Syndrome Coronavirus 2; WT, wild type.