Figure 4. Effect of TMPRSS2 and IFITM on S‐ or ACE2‐expressing cells.

• A
  S‐expressing cells (Donor cells) and ACE2‐expressing cells (Acceptor cells) were co‐transfected with TMPRSS2, IFITM, or control plasmids. Cell fusion was quantified by measuring the GFP⁺ area after 18 h. The indicated combinations were tested. The impact of IFITMs was measured in absence of TMPRSS2 (left panel), in the presence of TMPRSS2 in donor (middle panel) or acceptor cells (right panel). Data are mean ± SD of four independent experiments. Statistical analysis: One‐way ANOVA, ns: non‐significant, **P < 0.01, ****P < 0.0001.
• B–D
  Impact of TMPRSS2 on IFITMs, ACE2, and S levels. B. TMPRSS2 does not decrease IFITM amounts measured by flow cytometry. 293T cells were transfected with the indicated IFITM plasmids, with or without TMPRSS2, and analyzed 18 h later. C. Impact of TMPRSS2 on S and ACE2, measured by Western blot. 293T cells were transfected with or without IFITM1, TMPRSS2, S, or ACE2 plasmids, and analyzed 18 h later. D. TMPRSS2 decreases S surface levels, measured by flow cytometry. 293T cells were transfected with S plasmid, with or without TMPRSS2, and analyzed 18 h later. Murine polyclonal anti‐S antibodies, one serum from a convalescent COVID‐19‐infected patient (sera n°111), and two monoclonal antibodies (anti‐S1 and anti‐S2) were tested. Data are representative of three independent experiments.

Source data are available online for this figure.