Pro-collagenase-1 (Matrix Metalloproteinase-1) Binds the α 2β1 Integrin upon Release from Keratinocytes Migrating on Type I Collagen

Abstract

In injured skin, collagenase-1 (matrix metalloproteinase-1 (MMP-1)) is induced in migrating keratinocytes. This site-specific expression is regulated by binding of the α2β1 integrin with dermal type I collagen, and the catalytic activity of MMP-1 is required for keratinocyte migration. Because of this functional association among substrate/ligand, receptor, and proteinase, we assessed whether the integrin also directs the compartmentalization of MMP-1 to its matrix target. Indeed, pro-MMP-1 co-localized to sites of α2β1 contacts in migrating keratinocytes. Furthermore, pro-MMP-1 co-immunoprecipitated with α2β1 from keratinocytes, and α2β1 co-immunoprecipitated with pro-MMP-1. No other MMPs bound α2β1, and no other integrins interacted with MMP-1. Pro-MMP-1 also provided a substrate for α2β1-dependent adhesion of platelets. Complex formation on keratinocytes was most efficient on native type I collagen and reduced or ablated on denatured or cleaved collagen. Competition studies suggested that the α2 I domain interacts with the linker and hemopexin domains of pro-MMP-1, not with the pro-domain. These data indicate that the interaction of pro. MMP-1 with α2β1 confines this proteinase to points of cell contact with collagen and that the ternary complex of integrin, enzyme, and substrate function together to drive and regulate keratinocyte migration.