Motogenic activity of IGD-containing synthetic peptides

Although the IGD amino acid motif (iso-gly-asp) is a highly conserved featu re of the fibronectin type I module, no biological activity has as yet been ascribed to it. We have previously reported that the gelatin-binding domai n of fibronectin stimulates the migration of human skin fibroblasts into na tive, but not denatured, type I collagen substrata, Two IGD-containing type I modules are present within the gelatin-binding domain. The object of thi s study was to ascertain whether soluble synthetic peptides containing the ICD motif stimulate fibroblast migration, We found that IGD peptides stimul ated fibroblast migration in the following order of activity: IGDS las pres ent in the ninth type I module) > IGDQ las present in the seventh type I mo dule) > IGD, The scrambled SDGI peptide and the well-characterised RGDS pep tide were devoid of motogenic activity. The migratory response of fibroblas ts to IGD-containing peptides consisted of two distinct phases: an initial period of peptide-mediated cell activation and a subsequent period of enhan ced migration manifest in the absence of further IGD peptide. Cell activati on was substratum-independent (occurring equally well on both native and de natured type I collagen substrata), whilst the manifestation of enhanced mi gration was persistent and substratum-dependent (being evident only by cell s adherent to a native collagen substratum). Our data further indicated tha t cell activation (1) is elicited by a signal transduction cascade occurrin g within minutes of cell exposure to IGD-containing peptides, (2) is depend ent upon integrin alpha v beta 3 functionality, (3) involves the tyrosine p hosphorylation of focal adhesion kinase (ppFAK125) and tit) is inhibited by signalling mediated through integrin alpha 5 beta 1. The expression of mig ration stimulating activity by soluble IGD-containing peptides clearly dist inguishes them from their RGD counterparts. This is the first identified bi ological activity of the highly conserved IGD motif and provides a rational platform for the development of a novel family of therapeutic compounds de signed to stimulate cell migration in relevant clinical situations, such as impaired wound healing.