Figure 3.

SKI-1 and nSREBP-2 enhance cell-to-cell fusion. (A) HeLa cells were transiently transfected with an empty vector (EV) or one encoding WT-spike (S). Acceptor TZM-bl cells were transfected with a vector expressing ACE2 alone or with vector expressing either SKI-1 or nSREBP-2. After 48 h, donor and acceptor cells were co-cultured for 18 h. (B) Donor cells were transfected with vectors expressing either no protein (empty vector, EV) or WT-spike (S) were co-cultured for 18 h with acceptor TZMbl HeLa cells expressing ACE2 receptor. Prior to co-culture, the cells were treated with 2.5 mM mevalonate. Relative luminescence units (RLU) were normalized to the EV value arbitrarily set to 1. Data are presented as mean values ± SD (n = 3 independent experiments). (C) Calu-3 cells were transduced with nanoluciferase-expressing HIV particles pseudotyped with empty vector (EV) or SARS-CoV-2 wild-type spike (WT), in absence or presence of 2.5 mM of Mevalonate (Mev). Pseudoparticle entry was expressed as relative luminescence units (RLU). Representative blots of at least three independent experiments are shown. p values (*, p < 0.05) were evaluated by a Student’s t-test.