Iron Export through the Transporter Ferroportin 1 Is Modulated by the Iron Chaperone PCBP2

Ferroportin 1 (FPN1) is an iron export protein found in mammals. FPN1 is important for the export of iron across the basolateral membrane of absorptive enterocytes and across the plasma membrane of macrophages. The expression of FPN1 is regulated by hepcidin, which binds to FPN1 and then induces its degradation. Previously, we demonstrated that divalent metal transporter 1 (DMT1) interacts with the intracellular iron chaperone protein poly(rC)-binding protein 2 (PCBP2). Subsequently, PCBP2 receives iron from DMT1 and then disengages from the transporter. In this study, we investigated the function of PCBP2 in iron export. Mammalian genomes encode four PCBPs (i.e. PCBP1–4). Here, for the first time, we demonstrated using both yeast and mammalian cells that PCBP2, but not PCBP1, PCBP3, or PCBP4, binds with FPN1. Importantly, iron-loaded, but not iron-depleted, PCBP2 interacts with FPN1. The PCBP2-binding domain of FPN1 was identified in its C-terminal cytoplasmic region. The silencing of PCBP2 expression suppressed FPN1-dependent iron export from cells. These results suggest that FPN1 exports iron received from the iron chaperone PCBP2. Therefore, it was found that PCBP2 modulates cellular iron export, which is an important physiological process.

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Chaperone turns gatekeeper: PCBP2 and DMT1 form an iron-transport pipeline

Biochemical Journal ◽

10.1042/bj20140720 ◽

2014 ◽

Vol 462 (1) ◽

pp. e1-e3 ◽

Cited By ~ 11

Author(s):

Darius J. R. Lane ◽

Des R. Richardson

Keyword(s):

Mammalian Cells ◽

Iron Transport ◽

Divalent Metal Transporter 1 ◽

Divalent Metal Transporter ◽

Metal Transporter ◽

Cellular Iron ◽

Biochemical Journal ◽

Ferroportin 1 ◽

Fe Uptake ◽

First Time

How is cellular iron (Fe) uptake and efflux regulated in mammalian cells? In this issue of the Biochemical Journal, Yanatori et al. report for the first time that a member of the emerging PCBP [poly(rC)-binding protein] Fe-chaperone family, PCBP2, physically interacts with the major Fe importer DMT1 (divalent metal transporter 1) and the Fe exporter FPN1 (ferroportin 1). In both cases, the interaction of the Fe transporter with PCBP2 is Fe-dependent. Interestingly, another PCBP Fe-chaperone, PCBP1, does not appear to bind to DMT1. Strikingly, the PCBP2–DMT1 interaction is required for DMT1-dependent cellular Fe uptake, suggesting that, in addition to functioning as an intracellular Fe chaperone, PCBP2 may be a molecular ‘gate- keeper’ for transmembrane Fe transport. These new data hint at the possibility that PCBP2 may be a component of a yet-to-be-described Fe-transport metabolon that engages in Fe channelling to and from Fe transporters and intracellular sites.

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Hepcidin inhibits apical iron uptake in intestinal cells

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00122.2007 ◽

2008 ◽

Vol 294 (1) ◽

pp. G192-G198 ◽

Cited By ~ 107

Author(s):

Natalia P. Mena ◽

Andrés Esparza ◽

Victoria Tapia ◽

Pamela Valdés ◽

Marco T. Núñez

Keyword(s):

Iron Uptake ◽

Basolateral Membrane ◽

Intestinal Cells ◽

Divalent Metal Transporter 1 ◽

Divalent Metal Transporter ◽

Cell Monolayers ◽

Metal Transporter ◽

Protein Levels ◽

J774 Cells ◽

Iron Export

Hepcidin (Hepc) is considered a key mediator in iron trafficking. Although the mechanism of Hepc action in macrophages is fairly well established, much less is known about its action in intestinal cells, one of the main targets of Hepc. The current study investigated the effects of physiologically generated Hepc on iron transport in Caco-2 cell monolayers and rat duodenal segments compared with the effects on the J774 macrophage cell line. Addition of Hepc to Caco-2 cells or rat duodenal segments strongly inhibited apical 55Fe uptake without apparent effects on the transfer of 55Fe from the cells to the basolateral medium. Concurrently, the levels of divalent metal transporter 1 (DMT1) mRNA and protein in Caco-2 cells decreased while the mRNA and protein levels of the iron export transporter ferroportin did not change. Plasma membrane localization of ferroportin was studied by selective biotinylation of apical and basolateral membrane domains; Hepc induced rapid internalization of ferroportin in J774 cells but not in Caco-2 cells These results indicate that the effect of Hepc is cell dependent: in macrophages it inhibits iron export by inducing ferroportin degradation, whereas in enterocytes it inhibits apical iron uptake by inhibiting DMT1 transcription. Our results highlight the crucial role of Hepc in the control of intestinal iron absorption.

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Iron Imports. V. Transport of iron through the intestinal epithelium

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00489.2005 ◽

2006 ◽

Vol 290 (3) ◽

pp. G417-G422 ◽

Cited By ~ 33

Author(s):

Yuxiang Ma ◽

Mary Yeh ◽

Kwo-yih Yeh ◽

Jonathan Glass

Keyword(s):

Iron Transport ◽

Brush Border Membrane ◽

Iron Absorption ◽

Basolateral Membrane ◽

Apical Surface ◽

Intracellular Iron ◽

Divalent Metal Transporter 1 ◽

Divalent Metal Transporter ◽

Metal Transporter ◽

Apical Compartment

Iron absorption across the brush-border membrane requires divalent metal transporter 1 (DMT1), whereas ferroportin (FPN) and hephaestin are required for exit across the basolateral membrane. However, how iron passes across the enterocyte is poorly understood. Both chaperones and transcytosis have been postulated to account for intracellular iron transport. With iron feeding, DMT1 undergoes endocytosis and FPN translocates from the apical cytosol to the basolateral membrane. The fluorescent metallosensor calcein offered to the basolateral surface of enterocytes is found in endosomes in the apical compartment, and its fluorescence is quenched when iron is offered to the apical surface. These experiments are consistent with vesicular iron transport as a possible pathway for intracellular iron transport.

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Expression of iron transport proteins divalent metal transporter-1, Ferroportin-1, HFE and transferrin receptor-1 in human monocyte-derived dendritic cells

Cell Biochemistry and Function ◽

10.1002/cbf.1363 ◽

2007 ◽

Vol 25 (3) ◽

pp. 287-296 ◽

Cited By ~ 7

Author(s):

Martin Brinkmann ◽

Regina Teuffel ◽

Nihay Laham ◽

Rachel Ehrlich ◽

Patrice Decker ◽

...

Keyword(s):

Transferrin Receptor ◽

Iron Transport ◽

Human Monocyte ◽

Transport Proteins ◽

Divalent Metal ◽

Divalent Metal Transporter 1 ◽

Divalent Metal Transporter ◽

Metal Transporter ◽

Ferroportin 1 ◽

Transferrin Receptor 1

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Hyperglycemia Does Not Affect Iron Mediated Toxicity of Cultured Endothelial and Renal Tubular Epithelial Cells: Influence of L-Carnosine

Journal of Diabetes Research ◽

10.1155/2016/8710432 ◽

2016 ◽

Vol 2016 ◽

pp. 1-9 ◽

Cited By ~ 4

Author(s):

Shiqi Zhang ◽

Emmanouil Ntasis ◽

Sarah Kabtni ◽

Jaap van den Born ◽

Gerjan Navis ◽

...

Keyword(s):

Epithelial Cells ◽

Umbilical Vein ◽

Receptor Protein ◽

Dependent Manner ◽

Tubular Epithelial Cells ◽

Intracellular Iron ◽

Alternative Source ◽

Divalent Metal Transporter 1 ◽

Divalent Metal Transporter ◽

Metal Transporter

Iron has been suggested to affect the clinical course of type 2 diabetes (T2DM) as accompanying increased intracellular iron accumulation may provide an alternative source for reactive oxygen species (ROS). Although carnosine has proven its therapeutic efficacy in rodent models of T2DM, little is known about its efficacy to protect cells from iron toxicity. We sought to assess if high glucose (HG) exposure makes cultured human umbilical vein endothelial cells (HUVECs) and renal proximal tubular epithelial cells (PTECs) more susceptible to metal induced toxicity and if this is ameliorated by L-carnosine. HUVECs and PTECs, cultured under normal glucose (5 mM, NG) or HG (30 mM), were challenged for 24 h with FeCl3. Cell viability was not impaired under HG conditions nor did HG increase susceptibility to FeCl3. HG did not change the expression of divalent metal transporter 1 (DMT1), ferroportin (IREG), and transferrin receptor protein 1 (TFRC). Irrespective of glucose concentrations L-carnosine prevented toxicity in a dose-dependent manner, only if it was present during the FeCl3challenge. Hence our study indicates that iron induced cytotoxicity is not enhanced under HG conditions. L-Carnosine displayed a strong protective effect, most likely by chelation of iron mediated toxicity.

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