Abstract
Abstract: :
Purpose: Several members of the ADAM (a disintegrin and metalloprotease) family are implicated in ectodomain shedding of transmembrane proteins and we proposed that activation of an ADAM is required for generating EGFR ligand(s) in response to epithelial wounding in the cornea. In this study, we sought to determine expression and distribution of ADAM-9, 10, 12 and 17 in corneal epithelial cells and their role of epithelial wound healing. Methods: RT-PCR and Western blotting were used to assess the expression of ADAMs in cultured human corneal epithelial cells. Immunohistochemistry was performed to determine the distribution of ADAM-10 and -17 in mouse corneas. MMP inhibitor GM6001 was used to elucidate the role of MMP activity in induction of EGFR activation and epithelial wound healing. Results: All four ADAMs (9, 10, 12 and 17) implicated in ectodomain shedding were expressed in human corneal epithelial cells at mRNA levels. The expression of ADAM-17 and 10 at the protein level was also observed, ADAM17 as a major band at 135 kDa and ADAM-10 two major bands at 135 kDa and 90 kDa. While the levels of ADAM10 and FAK remained the same, the level of ADAM-17 appears to be downregulated in cultured human corneal epithelial cells 10 min post-wounding. Membrane-associated staining pattern was observed for both ADAMs in epithelial and endothelial layers of the mouse corneas. Inhibition of MMP activity resulted in inhibition of wound-induced EGFR phosphorylation and attenuation of epithelial wound closure in cultured bovine corneas and in cultured human corneal epithelial cells. The effects of MMP inhibitor can be reversed by EGF or HB-EGF. Conclusions: ADAM-mediated ectodomain shedding of EGFR ligands may represent an early step to initiate the epithelial response to wounding in the cornea.
Keywords: cornea: epithelium • proteolysis • wound healing