Single-molecule-force spectroscopy study of the mechanism of interactions between TSP-1 and CD47

The 4N1K peptide, which is derived from the C-terminal domain of thrombospondin-1 (TSP-1), is usually used as a functional mimic peptide for TSP-1. Knowledge about the interaction force of 4N1K/CD47 is important in explaining how TSP-1 affects the biological effect of CD47. Here we used a single-molecule force spectroscopy (SMFS) technique to explore the interaction of 4N1K/CD47 on both normal and oxidative human red blood cells (hRBCs) at single-molecule level. There was no interaction force between 4N1K and CD47 on normal hRBCs; however, we did find 4N1K-bound CD47 on oxidative hRBCs. We also detected interaction forces for 4N1K/CD47(ex) (extracellular domain of human CD47), and 4N1K/oxidative CD47(ex). The interaction forces of 4N1K/CD47(ex) were almost consistent with those of 4N1K/oxidative CD47(ex) at the same loading rate. These results suggest that the conformational change of CD47 is critical for 4N1K-CD47 interaction on oxidative hRBCs