Up-regulation of HSP70 by the fibronectin-derived peptide PHSRN in human corneal epithelial cells

HSP70 is a member of the heat shock protein family and is induced by various types of cellular stress. We examined whether HSP70 might play a role in the healing of corneal epithelial wounds. Given that the PHSRN peptide, which corresponds to the second cell-binding domain of fibronectin, promotes corneal epithelial migration, we investigated the effect of this peptide on HSP70 expression in cultured human corneal epithelial cells. Reverse transcription–polymerase chain reaction and immunoblot analyses revealed that PHSRN increased the amounts of HSP70 mRNA and protein in these cells in a concentration- and time-dependent manner, whereas a control peptide (NRSHP) had no such effects. Furthermore, the PHSRN-induced up-regulation of HSP70 was blocked by SB203580, an inhibitor of p38 mitogen-activated protein kinase (MAPK), but it was not affected by PD98059 or SP600125, inhibitors of signaling by the MAPKs ERK and JNK, respectively. Our results suggest that induction of HSP70 expression may contribute to the promotion of corneal epithelial migration by PHSRN and hence to corneal epithelial wound healing.