Structure of the Human Transferrin Receptor-Transferrin Complex

Cheng, Yifan; Zak, Olga; Aisen, Philip; Harrison, Stephen C.; Walz, Thomas

doi:10.1016/s0092-8674(04)00130-8

Cited by 491 publications

(480 citation statements)

References 51 publications

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“…Iron dissociation from Tf triggers large-scale conformational changes in each of its lobes, which may interfere with the ability of this protein to make contacts with key TfR residues in the binding interface. Recent analysis of the low-resolution structure of the Tf/TfR complex suggests that only conformational changes triggered by iron removal from the N-lobe may be restricted by hTf binding to TfR (22). We note that despite the existence of two distinct conformations (open in the iron-free protein and closed in the holo-form), Tf molecules are highly dynamic in solution, and may sample both open and closed states in the absence of iron (24).…”

Section: Discussionmentioning

confidence: 73%

“…Specific binding of aTf to TfR at mildly basic (near-physiological) pH with modest, but measurable (sub-μM) affinity is rather surprising, since Tf conformation was suggested as the major factor enabling its recognition by the receptor (12,13,22,23). Iron dissociation from Tf triggers large-scale conformational changes in each of its lobes, which may interfere with the ability of this protein to make contacts with key TfR residues in the binding interface.…”

Section: Discussionmentioning

confidence: 99%

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Noncanonical interactions between serum transferrin and transferrin receptor evaluated with electrospray ionization mass spectrometry

Leverence

Mason

Kaltashov

2010

Proc. Natl. Acad. Sci. U.S.A.

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The primary route of iron acquisition in vertebrates is the transferrin receptor (TfR) mediated endocytotic pathway, which provides cellular entry to the metal transporter serum transferrin (Tf). Despite extensive research efforts, complete understanding of Tf-TfR interaction mechanism is still lacking owing to the complexity of this system. Electrospray ionization mass spectrometry (ESI MS) is used in this study to monitor the protein/receptor interaction and demonstrate the ability of metal-free Tf to associate with TfR at neutral pH. A set of Tf variants is used in a series of competition and displacement experiments to bracket TfR affinity of apo-Tf at neutral pH (0.2-0.6 μM). Consistent with current models of endosomal iron release from Tf, acidification of the protein solution results in a dramatic change of binding preferences, with apo-Tf becoming a preferred receptor binder. Contrary to the current models implying that the apo-Tf/TfR complex dissociates almost immediately upon exposure to the neutral environment at the cell surface, our data indicate that this complex remains intact. Iron-loaded Tf displaces apo-Tf from TfR, making it available for the next cycle of iron binding, transport and delivery to tissues. However, apo-Tf may still interfere with the cellular uptake of engineered Tf molecules whose TfR affinity is affected by various modifications (e.g., conjugation to cytotoxic molecules). This work also highlights the great potential of ESI MS as a tool capable of providing precise details of complex protein-receptor interactions under conditions that closely mimic the environment in which these encounters occur in physiological systems.metalloprotein | protein interaction

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Section: Discussionmentioning

confidence: 73%

Section: Discussionmentioning

confidence: 99%

Noncanonical interactions between serum transferrin and transferrin receptor evaluated with electrospray ionization mass spectrometry

Leverence

Mason

Kaltashov

2010

Proc. Natl. Acad. Sci. U.S.A.

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“…When all three proteins are present, HFE⅐TfR⅐Fe-Tf ternary complexes are observed in solution (18) and in lysates from HFE-transfected HeLa cells (21,22). Competition (23), mutagenesis (20,24), time-resolved x-ray footprinting (25), and electron microscopy studies (26) demonstrate that Fe-Tf and HFE compete for overlapping binding sites on each TfR chain; thus, HFE⅐TfR⅐Fe-Tf ternary complexes have a 1:1:1 stoichiometry, such that HFE binds to one TfR polypeptide chain and Fe-Tf binds to the other.…”

mentioning

confidence: 99%

HFE and Transferrin Directly Compete for Transferrin Receptor in Solution and at the Cell Surface

Giannetti¹,

Björkman

2004

Journal of Biological Chemistry

129

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Transferrin receptor (TfR) is a dimeric cell surface protein that binds both the serum iron transport protein transferrin (Fe-Tf) and HFE, the protein mutated in patients with the iron overload disorder hereditary hemochromatosis. HFE and Fe-Tf can bind simultaneously to TfR to form a ternary complex, but HFE binding to TfR lowers the apparent affinity of the Fe-Tf/TfR interaction. This apparent affinity reduction could result from direct competition between HFE and Fe-Tf for their overlapping binding sites on each TfR polypeptide chain, from negative cooperativity, or from a combination of both. To explore the mechanism of the affinity reduction, we constructed a heterodimeric TfR that contains mutations such that one TfR chain binds only HFE and the other binds only Fe-Tf. Binding studies using a heterodimeric form of soluble TfR demonstrate that TfR does not exhibit cooperativity in heterotropic ligand binding, suggesting that some or all of the effects of HFE on iron homeostasis result from competition with Fe-Tf for TfR binding. Experiments using transfected cell lines demonstrate a physiological role for this competition in altering HFE trafficking patterns.

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“…The partition coefficient, κ, was calculated according to the expression κ = (1-λ) 2 , where λ is the diameter of Tf divided by the diameter of the tubule [32]. An average Tf diameter of 60 nM was estimated from the crystal structure of Tf [33], and a tubule diameter of 600 nM was assumed [34].…”

Section: Supplementary Materialsmentioning

confidence: 99%

Inhibition of transferrin iron release increases in vitro drug carrier efficacy

Lao

Tsai

Mashayekhi

et al. 2007

Journal of Controlled Release

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Transferrin (Tf) conjugates of CRM107 are currently being tested in clinical trials for treatment of malignant gliomas. However, the rapid cellular recycling of Tf limits its efficiency as a drug carrier. We have developed a mathematical model of the Tf/TfR trafficking cycle and have identified the Tf iron release rate as a previously unreported factor governing the degree of Tf cellular association. The release of iron from Tf is inhibited by replacing the synergistic carbonate anion with oxalate. Trafficking patterns for oxalate Tf and native Tf are compared by measuring their cellular association with HeLa cells. The amount of Tf associated with the cells is an average of 51% greater for oxalate Tf than for native Tf over a two hour period at Tf concentrations of 0.1 nM and 1 nM. Importantly, diphtheria toxin (DT) conjugates of oxalate Tf are more cytotoxic against HeLa cells than conjugates of native Tf. Conjugate IC 50 values were determined to be 0.06 nM for the oxalate Tf conjugate vs. 0.22 nM for the native Tf conjugate. Thus, we show that inhibition of Tf iron release improves the efficacy of Tf as a drug carrier through increased association with cells expressing TfR.

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Structure of the Human Transferrin Receptor-Transferrin Complex

Cited by 491 publications

References 51 publications

Noncanonical interactions between serum transferrin and transferrin receptor evaluated with electrospray ionization mass spectrometry

Noncanonical interactions between serum transferrin and transferrin receptor evaluated with electrospray ionization mass spectrometry

HFE and Transferrin Directly Compete for Transferrin Receptor in Solution and at the Cell Surface

Inhibition of transferrin iron release increases in vitro drug carrier efficacy

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