Two types of receptors (DDR1 and DDR2) on cell surfaces get turned on when collagen binds to them, which then starts chains of chemical signals inside the cell that control growth and survival.

“Collagen binds to two types of DDRs including DDR1 (commonly expressed in epithelial cells) and DDR2 (commonly expressed in fibroblasts and mesenchymal cells) spontaneously at the extra/intracellular juxtamembrane domain, N-terminus, tyrosine kinase domain at the C-terminus and transmembrane domain. Collagen binding with the discoidin domain causes conformation changes in DDRs and tyrosine kinase domain phosphorylation, leading to the engagement of ShcA and Nck2 adapter proteins to the cytoplasmic domain of DDRs.”