p75 neurotrophin receptor regulates NGF-induced myofibroblast differentiation and collagen synthesis through MRTF-A.

Myofibroblasts are characterized by de novo expression of α-smooth muscle actin (α-SMA) and play a key role in tissue repair and remodeling. In addition to TGF-β1, recent studies have shown that nerve growth factor (NGF) has effects on myofibroblast differentiation and collagen synthesis. However, the regulatory mechanism remains poorly defined. NGF effects are mediated by the specific expression of the NGF neurotrophic tropomyosin-receptor kinase A (TrkA) and p75 neurotrophin receptor (p75). Using NIH/3T3 fibroblast cell lines, we examined the induction of myofibroblast differentiation stimulated by NGF. Our findings showed that p75 was in keeping with the expression of α-SMA. Herein, we investigated the role of p75 in NGF-induced myofibroblast differentiation and collagen synthesis in these cells using lentivirus transfection to overexpress and knock down. Our results showed that p75 was preferentially expressed and was sufficient to induce actin cytoskeleton remodeling, which was required for NGF-induced α-SMA expression. Furthermore, NGF induced nuclear translocation of MRTF-A, an effect that was regulated by p75, and required for α-SMA and collagen-I expression in myofibroblasts. Using a novel MRTF-A pathway inhibitor, CCG-203971, we further demonstrated the requirement of MRTF-A nuclear localization and activity in NGF-induced α-SMA expression. In conclusion, we conclude that p75 regulates NGF-induced myofibroblast differentiation and collagen synthesis through MRTF-A. Regulation of NGF-p75 interactions represents a promising therapy for fibrotic disorders.