Identification of cathepsin B as a novel target of hypoxia-inducible factor-1-alpha in HepG2 cells

• Published in: Biochemical and biophysical research communications Vol. 503; no. 2; pp. 1057 - 1062
• Main Authors: Xiaofei, Cheng, Yanqing, Li, Dongkai, Zhou, Dong, Chen, Feng, Zhao, Weilin, Wang
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 05.09.2018
• Subjects: 60 APPLIED LIFE SCIENCES; ANGIOGENESIS; Cathepsin B (CTSB); Cathepsin B - genetics; CATHEPSINS; Cell Hypoxia; CELL PROLIFERATION; GLUCOSE; Hep G2 Cells; Humans; Hypoxia-Inducible Factor 1, alpha Subunit - metabolism; Hypoxia-inducible factor-1-alpha (HIF-1α); LUCIFERASE; MESSENGER-RNA; NEOPLASMS; Oxygen - metabolism; Promoter Regions, Genetic; Response Elements; Target gene; Transcription; Transcriptional Activation; Up-Regulation; Cathepsin B (CTSB); Transcription; Hypoxia-inducible factor-1-alpha (HIF-1α); Target gene
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2018.06.116

Hypoxia-inducible factor-1-alpha (HIF-1α) activates the transcription of many genes that code for proteins involved in angiogenesis, glucose metabolism, cell proliferation/survival, and invasion/metastasis. However, the mechanisms between HIF-1 and its downstream target genes are still poorly understood. Our experimental results had shown that nuclear HIF-1α proteins were significantly induced after HepG2 cells treatment with 1% O2 for 6 h and reached the peak expression level in 24 h. Meanwhile, the results of RT-qPCR and Western-blotting showed that HIF-1α and cathepsin B (CTSB) expressions increased with a similar pattern in response to hypoxia in the HepG2 cells. Additionally, based on bioinformatics analysis, we identified a hypoxia response element in the CTSB promoter, indicating a possible association between HIF-1α and CTSB. Moreover, luciferase assay was performed to reflect the transcriptional activity mediated through the HIF-1α binding HRE within the CTSB promoter. Furthermore, electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (CHIP) revealed a specific HIF-1α binding activity to the CTSB gene promoter. For the first time, we demonstrated that CTSB is a new HIF-1α-target gene. We believe these findings will contribute to the research and development of neoplasm-targeted therapies. •Cathepsin B (CTSB) is a novel target gene of hypoxia-inducible factor-1-alpha (HIF-1α).•CTSB mRNA and protein levels can be up-regulated in a HIF-1α-dependent manner.•CTSB promoter activity can be elevated by the HIF-1α protein.•HIF-1α protein binds the CTSB promoter directly.