Decorin/decorin
Decorin belongs to the family of small leucine-rich proteoglycans that harbors one chondroitin/dermatan sulfate side chain at its N terminus. It was originally named because of its ability to “decorate” collagen fibrils, thereby regulating fibrillogenesis, a key mechanism of matrix assembly and homeostasis. Decorin binds to type I collagen and stabilizes the structure of the extracellular matrix. Decorin interacts also with fibronectin, thrombospondin and the complement component C1q.
It suppresses cellular proliferation, is strongly expressed in quiescent post-confluent fibroblasts and rarely expressed within actively proliferating or transformed tissues.
Decorin contains leucine-rich repeats (=matrikines) able to bind EGF receptor (Kd 27-887 nM), thereby triggering a signaling cascade that initially leads to phosphorylation of mitogen-activated protein (MAP) kinase, induction of p21, and growth suppression. This activation eventually results in a decrease of EGFR levels and nearly complete suppression of EGFR autophosporylation.
Decorin regulates the TGF-β signaling pathway. Decorin suppresses tumor cell–mediated angiogenesis by inhibiting the endogenous production of vascular endothelial cell growth factor. Decorin binds directly and with high affinity (Kd = 1.5 nM) to Met, the receptor for hepatocyte growth factor (HGF) and suppresses intracellular levels of β-catenin, a known downstream Met effector, and thereby inhibits Met-mediated cell migration and growth.
During skin repair, decorin would function as a quiescence signal inducing decrease of migration, proliferation and extracellular matrix production by fibroblasts when the wound has reached its mature state.
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