Figure 1.

A model of microenvironment sensing by DDRs. When tissue is intact and healthy, DDR binding sites in collagen fibrils in tissue are not readily available for DDRs, thus DDRs cannot bind to collagens and the receptor activation does not occur. Upon tissue injuries causing proteolytic damage of ECM microenvironment, DDR binding sites within collagen become exposed, DDR activation tales place, and induce MMP expression and cell migration. This event may lead to tissue repair or contribute to further tissue damage and promote progression of diseases. DS, discoidin domain; DSL, discoidin-like domain; TK, tyrosine kinase domain.