SCG2 Transcriptionally Activated by SP1 Promotes Nasal Epithelial Cell Proliferation and Epithelial Mesenchymal Transition

Chronic rhinosinusitis with nasal polyps (CRSwNP) is characterized by a tendency to recur and a poor prognosis. Epithelial mesenchymal transition (EMT) and proliferation of nasal epithelial cells (NECs) play an important role in CRSwNP development. Secretogranin II (SCG2) is reported to be an EMT-related gene, but its role in CRSwNP has not been reported. In this study, human NECs were cultured in an air-liquid interface culture system and stimulated with IL-13 to maintain or promote the CRSwNP state. EMT-associated protein expression levels were examined by real-time quantitative PCR and Western blot. Dual luciferase, chromatin immunoprecipitation, and co-immunoprecipitation experiments were used to validate the regulatory relationship between SP1, SCG2, and ubiquitin-1 (UBQLN1). The nuclear translocation of Snail was examined by immunofluorescence assay. The results showed that the expression levels of SP1, SCG2, and UBQLN1 were all up-regulated in CRSwNP tissues. SCG2 knockdown inhibited EMT and proliferation of human NECs. Mechanistically, SP1 promoted the proliferation and EMT of human NECs by transcriptionally increasing SCG2 expression. SCG2 activated the Akt serine/threonine kinase (Akt)/glycogen synthase kinase-3 beta (GSK-3β)/Snail family transcriptional repressor 1 (Snail) pathway and promoted Snail nuclear translocation via UBQLN1. In short, SCG2, which is transcriptionally up-regulated by SP1, promotes the proliferation and EMT of human NECs by activating the Akt/GSK-3β/Snail pathway through binding to UBQLN1.