Figure 1.

Mitoxantrone affects the spike-heparin interaction. (A) Spike binds to heparin in a salt sensitive manner. Purified spike ECD was incubated with either Sepharose or heparin-coated Sepharose in a buffer containing either low salt (2 mM) or 150 mM salt. Bound proteins and a fraction of input were analyzed by SDS-PAGE and Coomassie blue staining. (B–D) Mitoxantrone but not Banoxantrone enhances the interaction of spike with heparin. (B) Heparin (HP) Sepharose beads were pre-incubated with a buffer in the absence or presence of 50 μM Mitoxantrone (MTAN) or Banoxantrone (BANO). After removing unbound drugs, the beads were incubated with recombinant spike ECD. Proteins precipitated were analyzed by immunoblotting with spike antibodies. PD, pulldown. (C,D) Quantification of the full-length spike ECD (S) or the furin-cleaved spike (S2) in (B). n = 4 independent experiments. (E) Mitoxantrone does not affect heparin-spike interaction under low salt conditions. As in (B), except that spike was pulled down in a low salt buffer and that the samples were analyzed by Coomassie blue staining. Asterisk indicates Mitoxantrone bound to heparin beads.