Syndecan peptides alter cell migration and fibronectin fibrillogenesis of syndecan 1 null dermal fibroblasts

Syndecan 1 (Sdc1) is a transmembrane proteoglycan known to regulate integrin activity at the cell surface. The influence of sdc1 on integrin activity can be assessed by evaluating the effect of peptides derived from syndecan core proteins on cell migration rates and extracellular matrix assembly. If syndecan peptides activate integrins, cell migration rates will be reduced because activated integrins have a higher affinity for adhesion to substrates, which increases the frictional force needed to allow cells to migrate. In addition, sdc peptide‐induced integrin activation would enhance fibronectin (FN) fibrillogenesis. To determine whether the core proteins of sdc1 and sdc4 affect cell migration and FN fibrillogenesis, sdc1 and sdc4 ectodomain peptides tagged with GST were produced in transformed bacteria. Peptides were added to wild‐type and sdc1‐null tertiary passage dermal fibroblasts. Cells were tracked by time‐lapse microscopy and were also fixed and stained to reveal the organization state of the fibronectin matrix. Results show that sdc1 and sdc4 peptides had no statistically significant impact on wt cell migration rates but the sd4 peptide eliminated the difference between wt and sdc1 null cell migration rates whereas the sdc1 peptide had no affect. Sdc1 null dermal fibroblasts had less FN present within their matrix. Preliminary studies show that sdc4 peptides increased FN fibrillogenesis in sdc1 null fibroblasts. These data suggest that sdc peptides alter integrin activity in cells that lack endogenous sdc1.