F-box and WD repeat domain containing 7 inhibits the activation of hepatic stellate cells by degrading delta-like ligand 1 to block Notch signaling pathway

Hepatic fibrosis (HF) is a precursor of liver cirrhosis, and activated hepatic stellate cells are an important driver of fibrosis. F-box and WD repeat domain containing 7 (FBXW7) expression level is down-regulated in HF, but the underlying mechanism is yet to be elucidated. The interaction between FBXW7 and delta-like ligand 1 (DLL1) was predicted. LX-2 cells were subjected to transfection of FBXW7/DLL1 silencing or overexpression plasmid. The expressions of FBXW7 and DLL1 in HF in vitro were measured by quantitative reverse transcription polymerase chain reaction and western blot. The LX-2 cell cycle, viability, proliferation, and ubiquitination were determined by flow cytometry, cell counting kit-8, colony formation, and ubiquitination assays, respectively. FBXW7 overexpression suppressed the cell viability and proliferation, facilitated cell cycle arrest, and down-regulated α-smooth muscle actin (α-SMA), Collagen I, and DLL1 protein levels, but FBXW7 silencing did the opposite. DLL1 was bound to and ubiquitin-dependently degraded by FBXW7 overexpression. DLL1 overexpression promoted the cell viability and proliferation, accelerated cell cycle, and up-regulated the levels of α-SMA, Collagen I, NOTCH2, NOTCH3, and HES1, but these trends were reversed by FBXW7 overexpression. To sum up, FBXW7 overexpression suppresses the progression of HF in vitro by ubiquitin-dependently degrading DLL1.