Okazaki Y, Glass J. Protoporphyrin IX regulates peripheral benzodiazepine receptor associated protein 7 (PAP7) and divalent metal transporter 1 (DMT1) in K562 cells.
Biochem Biophys Rep 2017;
10:26-31. [PMID:
28955733 PMCID:
PMC5614651 DOI:
10.1016/j.bbrep.2017.02.007]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 02/17/2017] [Accepted: 02/25/2017] [Indexed: 11/28/2022] Open
Abstract
Background
Protoporphyrin IX (PP IX), the immediate precursor to heme, combines with ferrous iron to make this product. The effects of exogenous PP IX on iron metabolism remain to be elucidated. Peripheral-type benzodiazepine receptor (PBR) is implicated in the transport of coproporphyrinogen into the mitochondria for conversion to PP IX. We have demonstrated that PBR-Associated Protein 7 (PAP7) bound to the Iron Responsive Element (IRE) isoform of divalent metal transporter 1 (DMT1). PP IX and PAP7 are ligands for PBR, thus, we hypothesized that PAP7 interact with PP IX via PBR.
Methods
We have examined in K562 cells, which can be induced to undergo erythroid differentiation by PP IX and hemin, the effects of PP IX on the expression of PAP7 and other proteins involved in cellular iron metabolism, transferrin receptor 1 (TfR1), DMT1, ferritin heavy chain (FTH), c-Myc and C/EBPα by western blot and quantitative real time PCR analyses.
Results
PP IX significantly decreased mRNA levels of DMT1 (IRE) and (non-IRE) from 4 h. PP IX markedly decreased protein levels of C/EBPα, PAP7 and DMT1. In contrast, hemin, which like PP IX also induces K562 cell differentiation, had no effect on PAP7 or DMT1 expression.
Conclusion
We hypothesize that PP IX binds to PBR displacing PAP7 protein, which is then degraded, decreasing the interaction of PAP7 with DMT1 (IRE) and resulting in increased turnover of DMT1.
General significance
These results suggest that exogenous PP IX disrupts iron metabolism by decreasing the protein expression levels of PAP7, DMT1 and C/EBPα.
Protoporphyrin IX (PP IX) decreased protein levels of PAP7 and DMT1 in K562.
PP IX decreased mRNA levels of DMT1 (IRE) and (non-IRE) isoforms in K562.
PP IX decreased protein level of C/EBPα, which transcribes DMT1 mRNA, in K562.
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