The discoidin domain-containing receptor (DDR) family includes DDR1 and DDR2. DDR family members are receptor tyrosine kinases (RTKs) whose activating ligands are various collagens []. The proteins contain an extracellular discoidin domain, which binds various collagen proteins, and an intracellular tyrosine kinase domain.DDR2 may have a role in wound healing; DDR2 signalling regulates cell proliferation and extracellular matrix synthesis, which are key aspects of fibroblast contribution to tissue healing []. Increased expression of DDR2 may also be important in the pathogenesis of osteoarthritis [], and there is evidence that the receptor could be implicated in certain forms of cancer - mutations in the DDR2 kinase gene have been detected in ~ 4% of squamous cell lung cancers [].Epithelial discoidin domain-containing receptor 1 (also known as DDR1) is involved in smooth muscle cell migration and matrix metalloproteinase expression []. It is responsible for maintaining the normal structure of skin and kidney epithelia []. The receptor may play a critical role in inducing tumour cell adhesion and invasion []. Itsstructure has been solved [].
