Regulation of HIF-1 alpha by the proprotein convertases furin and PC7 in human squamous carcinoma cells.

Abstract

Proprotein convertases (PC), a family of serine proteases, process cancer-related substrates such as growth factors, growth factor receptors, cell adhesion molecules, metalloproteinases, etc. HIF-1α is a major transcription factor involved in tumorigenesis by sensing intratumoral hypoxia. Furin (PCSK3) is one of the numerous target genes regulated by HIF-1α transactivation and its distribution into endosomal compartments and onto the cell surface can be triggered by hypoxia via HIF-1α. siRNAs to knockdown PCs were transfected into cells alone or in combination with different drug treatments. Protein and RNA expression levels were analyzed by Western blotting or RT-PCR, respectively. PC7 (PCSK7) and furin siRNAs upregulated HIF-1α protein under normoxic condition to a level similar to that obtained by cobalt chloride treatment, eventually leading to activation of VEGF-A synthesis in two human head and neck squamous cell carcinoma cell lines. The unchanged levels of HIF-1α mRNA expression under siRNA treatment and the additive HIF-1α induction of PC siRNAs and either cobalt chloride or the 26S ribosome inhibitor, MG-132, suggested a post-transcriptional PC-mediated regulation. Furthermore, cycloheximide chase showed that PC7/furin siRNA regulation occurred at the level of HIF-1α translation. A specific IGF-1R signaling inhibitor was able to attenuate the PC siRNA induction of HIF-1α, suggesting the involvement of the IGF-1R pathway. Thus, the data show that PCs regulate HIF-1α. Furin and PC7 siRNAs induced HIF-1α protein by increasing its translation, resulting in upregulation of VEGF-A. This finding may provide insight into intricate PC functions that seem to be independent from their substrate-processing activity.

• Authors: Jian Fu, Jirong Zhang, Yulan Gong, Courtney Lyons Testa, Andres J Klein-Szanto
• Journal: Molecular carcinogenesis (Mol Carcinog) Vol. 54 Issue 9 Pg. 698-706 (Sep 2015) ISSN: 1098-2744 [Electronic] United States
• PMID: 24436242 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)
• Copyright: © 2014 Wiley Periodicals, Inc.

Chemical References

• Hypoxia-Inducible Factor 1, alpha Subunit
• RNA, Small Interfering
• Vascular Endothelial Growth Factor A
• Insulin-Like Growth Factor I
• PCSK7 protein, human
• Subtilisins
• Furin

Topics

• Carcinoma, Squamous Cell (genetics, metabolism)
• Cell Line, Tumor
• Down-Regulation
• Furin (genetics, metabolism)
• Gene Expression Regulation, Neoplastic
• Head and Neck Neoplasms (genetics, metabolism)
• Humans
• Hypoxia-Inducible Factor 1, alpha Subunit (genetics, metabolism)
• Insulin-Like Growth Factor I (metabolism)
• Protein Biosynthesis
• RNA Interference
• RNA, Small Interfering (genetics)
• Signal Transduction
• Subtilisins (genetics, metabolism)
• Up-Regulation
• Vascular Endothelial Growth Factor A (genetics, metabolism)