FIGURE 4.

Two synthetic peptides derived from the LRR4–6 region of decorin (Dcn) decreases LRP-1-mediated decorin endocytosis and TGF-β-mediated signaling. A, C2C12 myoblasts were incubated with ³⁵S-decorin mutants at 37 °C for 3 h in the absence or presence of 225 nm synthetic peptides derived from the LRR4, LRR5, LRR6, or LRR12 regions of decorin. The cells were then analyzed to determine levels of decorin endocytosis as described in the legend to Fig. 1D. Values correspond to the mean ± S.D. from three independent experiments (* and &, p < 0.05; #, p < 0.001). B, wild type and decorin-deficient myoblasts were transiently transfected with plasmids containing p3TP-lux and pRL-SV40 sequences and incubated with 75 nm hDcnHA in the absence or presence of 225 nm synthetic peptides derived from LRR4, LRR5, LRR6, or LRR12 regions of decorin. After 6 h of TGF-β1 (1.0 ng/ml) treatment, cells were lysed and reporter activities were determined. Values correspond to the mean ± S.D. from three independent experiments (* and &, p < 0.05; #, p < 0.001). C, wild type and decorin-deficient myoblasts were transiently transfected with p3TP-lux and pRL-SV40, and incubated with hDcnHA in the absence or presence of the indicated amounts of synthetic LRR5 and LRR6 peptides. After 6 h of TGF-β1 (1.0 ng/ml) treatment, cells were lysed and reporter activities were determined. 100% correspond to p3TP-lux induction in WT cells. Values correspond to the mean ± S.D. from three independent experiments (*, #, and &, p < 0.05). D, C2C12 myoblasts were incubated with 75 nm hDcnHA at 4 °C for 3 h in the absence or presence of the 75 or 225 nm LRR6 peptides. Lactoferrin was used as a protein that displaces the binding of ligands to LRP-1. Cell extracts were obtained and the immunoprecipitated anti-LRP-1 antibody was evaluated by Western blot using an anti-HA and anti-LRP-1 antibodies, respectively.