Fig. 9. Mesd inhibits DKK1 binding to LRP6. (A-C) Serum-free conditioned medium was harvested from HEK293 cells transiently transfected with cDNA for human Myc-DKK1 and allowed to bind to LRP6-transduced HT1080 cells (B,C) and control cells (A) in the absence (A,B) or presence (C) of 1 µM Mesd. Cell-surface-bound Myc-tagged DKK proteins were fixed and detected by immunofluorescence staining with anti-Myc antibody. (D) DKK1 binding to cell surface LRP6 is inhibited by Mesd. Binding of ¹²⁵I-DKK1 (5 nM) to LRP6-transduced HT1080 cells or the control cells was carried out for 3 hours at 4°C in the absence (total) or presence of 500 nM RAP or 500 nM Mesd. (E) LRP6-mediated DKK1 degradation is inhibited by Mesd. LRP6-mediated ¹²⁵I-Mesd (5 nM) degradation was carried out for 4 hours at 37°C in the absence or presence of 500 nM RAP or 500 nM Mesd. Values are the means of triple determinations with the s.d. indicated by error bars. Bar, 10 µm.