Coordinated expression of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 4 and heme oxygenase 2: evidence for a regulatory link between glycolysis and heme catabolism.

Abstract

Heme is an essential requirement for cell survival. Heme oxygenase (HO) is the rate-limiting enzyme in heme catabolism and consists of two isozymes, HO-1 and HO-2. To identify the protein that regulates the expression or function of HO-1 or HO-2, we searched for proteins that interact with both isozymes, using protein microarrays. We thus identified 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 4 (PFKFB4) that synthesizes or degrades fructose-2,6-bisphosphate, a key activator of glycolysis, depending on cellular microenvironments. Importantly, HO-2 and PFKFB4 are predominantly expressed in haploid spermatids. Here, we show a drastic reduction in expression levels of PFKFB4 mRNA and protein and HO-2 mRNA in HepG2 human hepatoma cells in responses to glucose deprivation (≤ 2.5 mM), which occurred concurrently with remarkable induction of HO-1 mRNA and protein. Knockdown of HO-2 expression in HepG2 cells, using small interfering RNA, caused PFKFB4 mRNA levels to decrease with a concurrent increase in HO-1 expression. Thus, in HepG2 cells, HO-1 expression was increased, when expression levels of HO-2 and PFKFB4 mRNAs were decreased. Conversely, overexpression of HO-2 in HepG2 cells caused the level of co-expressed PFKFB4 protein to increase. These results suggest a potential regulatory role for HO-2 in ensuring PFKFB4 expression. Moreover, in D407 human retinal pigment epithelial cells, glucose deprivation decreased the expression levels of PFKFB4, HO-1, and HO-2 mRNAs. Thus, glucose deprivation consistently down-regulated the expression of PFKFB4 and HO-2 mRNAs in both HepG2 cells and RPE cells. We therefore postulate that PFKFB4 and HO-2 are expressed in a coordinated manner to maintain glucose homeostasis.

• Authors: Bin Li, Kazuhisa Takeda, Kazunobu Ishikawa, Miki Yoshizawa, Michihiko Sato, Shigeki Shibahara, Kazumichi Furuyama
• Journal: The Tohoku journal of experimental medicine (Tohoku J Exp Med) Vol. 228 Issue 1 Pg. 27-41 (09 2012) ISSN: 1349-3329 [Electronic] Japan
• PMID: 22892400 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• PFKFB4 protein, human
• RNA, Messenger
• Heme
• Heme Oxygenase (Decyclizing)
• Heme Oxygenase-1
• heme oxygenase-2
• Phosphofructokinase-2
• Glucose

Topics

• Animals
• Down-Regulation (genetics)
• Epithelial Cells (enzymology)
• Gene Expression Regulation, Enzymologic
• Gene Knockdown Techniques
• Glucose (deficiency)
• Glycolysis (genetics)
• HeLa Cells
• Heme (metabolism)
• Heme Oxygenase (Decyclizing) (deficiency, genetics, metabolism)
• Heme Oxygenase-1 (genetics, metabolism)
• Hep G2 Cells
• Humans
• Liver (enzymology)
• Male
• Mice
• Mice, Inbred C57BL
• Models, Biological
• Organ Specificity
• Phosphofructokinase-2 (genetics, metabolism)
• Protein Array Analysis
• Protein Binding
• RNA, Messenger (genetics, metabolism)
• Testis (enzymology)