scholarly journals Membrane-inserted conformation of transmembrane domain 4 of divalent-metal transporter

2003 ◽  
Vol 372 (3) ◽  
pp. 757-766 ◽  
Author(s):  
Hongyan LI ◽  
Fei LI ◽  
Hongzhe SUN ◽  
Zhong Ming QIAN
Keyword(s):  
Transmembrane Domain ◽  
Ph Value ◽  
Structural Features ◽  
Divalent Metal ◽  
Divalent Metal Transporter 1 ◽  
Divalent Metal Transporter ◽  
Metal Transporter ◽  
Sds Micelles ◽  
Domain 4

Divalent-metal transporter 1 (DMT1) is involved in the intestinal iron absorption and in iron transport in the transferrin cycle. It transports metal ions at low pH (≈5.5), but not at high pH (7.4), and the transport is a proton-coupled process. Previously it has been shown that transmembrane domain 4 (TM4) is crucial for the function of this protein. Here we provide the first direct experimental evidence for secondary-structural features and membrane insertions of a 24-residue peptide, corresponding to TM4 of DMT1 (DMTI-TM4), in various membrane-mimicking environments by the combined use of CD and NMR spectroscopies. The peptide mainly adopts an α-helical structure in trifluoroethanol, SDS and dodecylphosphocholine micelles, and dimyristoyl phosphatidylcholine and dimyristoyl phosphatidylglycerol small unilamellar vesicles. It has been demonstrated from both Hα secondary shifts and nuclear-Overhauser-enhancement (NOE) connectivities that the peptide is well folded into an α-helix from Val8 to Lys23 in SDS micelles at pH 4.0, whereas the N-terminus is highly flexible. The α-helical content estimated from NMR data is in agreement with that extracted from CD simulations. The highest helicity was observed in the anionic phospholipids {1,2-dimyristoyl-sn-glycero-3-[phospho-rac-(1-glycerol)]}, indicating that electrostatic attraction is important for peptide binding and insertion into the membranes. The secondary-structural transition of the peptide occurred at pH 4.3 in the 2,2,2-trifluoroethanol (TFE) water mixed solvent, whereas at a higher pH value (5.6) in SDS micelles, DMT1-TM4 exhibited a more stable structure in SDS micelles than that in TFE in terms of changing the pH and temperature. PAGE did not show high-molecular-mass aggregates in SDS micelles. The position of the peptide relative to SDS micelles was probed by the effects of 5- and 16-doxylstearic acids on the intensities of the peptide proton resonances. The results showed that the majority of the peptide is inserted into the hydrophobic interior of SDS micelles, whereas the C-terminal residues are surface-exposed. The ability of DMT1-TM4 to assume transmembrane features may be crucial for its biological function in vivo.

Divalent metal transporter-1 decreases metal-related injury in the lung

2005 ◽  
Vol 289 (3) ◽  
pp. L460-L467 ◽  
Author(s):  
Andrew J. Ghio ◽  
Claude A. Piantadosi ◽  
Xinchao Wang ◽  
Lisa A. Dailey ◽  
Jacqueline D. Stonehuerner ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Metal Transport ◽  
Airway Epithelial Cells ◽  
Divalent Metal ◽  
Primary Role ◽  
Airway Epithelial ◽  
Divalent Metal Transporter 1 ◽  
Divalent Metal Transporter ◽  
Metal Transporter

Exposure to airborne particulates makes the detoxification of metals a continuous challenge for the lungs. Based on the fate of iron in airway epithelial cells, we postulated that divalent metal transporter-1 (DMT1) participates in detoxification of metal associated with air pollution particles. Homozygous Belgrade rats, which are functionally deficient in DMT1, exhibited diminished metal transport from the lower respiratory tract and greater lung injury than control littermates when exposed to oil fly ash. Preexposure of normal rats to iron in vivo increased expression of the isoform of DMT1 protein that lacked an iron-response element (−IRE), accelerated metal transport out of the lung, and decreased injury after particle exposure. In contrast, normal rats preexposed to vanadium showed less expression of the −IRE isoform of DMT1, decreased metal transport, and greater pulmonary injury after particle instillation. Respiratory epithelial cells in culture gave similar results. Also, DMT1 mRNA and protein expression for the −IRE isoform increased or decreased in these cells when exposed to iron or vanadium, respectively. These results thus demonstrate for the first time a primary role for DMT1 in lung metal transport and detoxification.

scholarly journals Small molecule inhibitors of divalent metal transporter-1

2009 ◽  
Vol 296 (4) ◽  
pp. G798-G804 ◽  
Author(s):  
Peter D. Buckett ◽  
Marianne Wessling-Resnick
Keyword(s):  
Small Molecule ◽  
Iron Metabolism ◽  
Iron Uptake ◽  
Small Molecule Inhibitors ◽  
Structural Features ◽  
Divalent Metal ◽  
Divalent Metal Transporter 1 ◽  
Divalent Metal Transporter ◽  
Copper Chelation ◽  
Metal Transporter

Divalent metal transporter-1 (DMT1) is a divalent cation transporter that plays a key role in iron metabolism by mediating ferrous iron uptake across the small intestine. We have previously identified several small molecule inhibitors of iron uptake ( 4 ). Using a cell line that stably overexpresses DMT1, we screened the ability of these inhibitors to specifically block this transporter's activity. One compound, NSC306711, inhibited DMT1-mediated iron uptake in a reversible and competitive manner. This inhibitor is a polysulfonated dye containing two copper centers. Although one of these two sites could be chelated by Triethylenetetramine copper chelation did not perturb NSC306711 inhibition of DMT1 activity. Several other polysulfonated dyes with structural features similar to NSC306711 were identified as potential DMT1 transport inhibitors. This study characterizes important pharmacological tools that can be used to probe DMT1's mechanism of iron transport and its role in iron metabolism.

Two routes of iron accumulation in astrocytes: ascorbate-dependent ferrous iron uptake via the divalent metal transporter (DMT1) plus an independent route for ferric iron

2010 ◽  
Vol 432 (1) ◽  
pp. 123-132 ◽  
Author(s):  
Darius J.R. Lane ◽  
Stephen R. Robinson ◽  
Hania Czerwinska ◽  
Glenda M. Bishop ◽  
Alfons Lawen
Keyword(s):  
Iron Uptake ◽  
Divalent Metal ◽  
Iron Accumulation ◽  
Mammalian Brain ◽  
Divalent Metal Transporter 1 ◽  
Divalent Metal Transporter ◽  
Metal Transporter ◽  
Uptake Pathway ◽  
Cultured Astrocytes

Astrocytes are central to iron and ascorbate homoeostasis within the brain. Although NTBI (non-transferrin-bound iron) may be a major form of iron imported by astrocytes in vivo, the mechanisms responsible remain unclear. The present study examines NTBI uptake by cultured astrocytes and the involvement of ascorbate and DMT1 (divalent metal transporter 1). We demonstrate that iron accumulation by ascorbate-deficient astrocytes is insensitive to both membrane-impermeant Fe(II) chelators and to the addition of the ferroxidase caeruloplasmin. However, when astrocytes are ascorbate-replete, as occurs in vivo, their rate of iron accumulation is doubled. The acquisition of this additional iron depends on effluxed ascorbate and can be blocked by the DMT1 inhibitor ferristatin/NSC306711. Furthermore, the calcein-accessible component of intracellular labile iron, which appears during iron uptake, appears to consist of only Fe(III) in ascorbate-deficient astrocytes, whereas that of ascorbate-replete astrocytes comprises both valencies. Our data suggest that an Fe(III)-uptake pathway predominates when astrocytes are ascorbate-deficient, but that in ascorbate-replete astrocytes, at least half of the accumulated iron is initially reduced by effluxed ascorbate and then imported by DMT1. These results suggest that ascorbate is intimately involved in iron accumulation by astrocytes, and is thus an important contributor to iron homoeostasis in the mammalian brain.

scholarly journals Divalent Metal Transporter 1 Knock-Down Modulates IL-1β Mediated Pancreatic Beta-Cell Pro-Apoptotic Signaling Pathways through the Autophagic Machinery

2021 ◽  
Vol 22 (15) ◽  
pp. 8013
Author(s):  
Taewook Kang ◽  
Honggang Huang ◽  
Thomas Mandrup-Poulsen ◽  
Martin R. Larsen
Keyword(s):  
Cell Death ◽  
Divalent Metal ◽  
Β Cells ◽  
Β Cell ◽  
Divalent Metal Transporter 1 ◽  
Divalent Metal Transporter ◽  
Knock Down ◽  
Metal Transporter ◽  
Cell Functions ◽  
Protective Proteins

Pro-inflammatory cytokines promote cellular iron-import through enhanced divalent metal transporter-1 (DMT1) expression in pancreatic β-cells, consequently cell death. Inhibition of β-cell iron-import by DMT1 silencing protects against apoptosis in animal models of diabetes. However, how alterations of signaling networks contribute to the protective action of DMT1 knock-down is unknown. Here, we performed phosphoproteomics using our sequential enrichment strategy of mRNA, protein, and phosphopeptides, which enabled us to explore the concurrent molecular events in the same set of wildtype and DMT1-silenced β-cells during IL-1β exposure. Our findings reveal new phosphosites in the IL-1β-induced proteins that are clearly reverted by DMT1 silencing towards their steady-state levels. We validated the levels of five novel phosphosites of the potential protective proteins using parallel reaction monitoring. We also confirmed the inactivation of autophagic flux that may be relevant for cell survival induced by DMT1 silencing during IL-1β exposure. Additionally, the potential protective proteins induced by DMT1 silencing were related to insulin secretion that may lead to improving β-cell functions upon exposure to IL-1β. This global profiling has shed light on the signal transduction pathways driving the protection against inflammation-induced cell death in β-cells after DMT1 silencing.

Sign in / Sign up

Export Citation Format

Share Document