Interaction of transferrin and its iron-binding fragments with heparin.

The hepatic uptake of transferrin-bound iron by aIron is required for the synthesis of many heme and nontransferrin receptor (NTR)-mediated process was non-heme proteins and enzymes necessary for cellular investigated using the human hepatoma cell line HuH7. growth and metabolism. Most cells take up iron from Because HuH7 cells also acquire iron from transferrin serum transferrin by a transferrin receptor (TR)-mediby a receptor (TR)-mediated process, TR expression was ated process. Hepatocytes, in addition to their own inhibited by transfecting the cells with a plasmid con-need for iron, are also an important site of iron storage. taining human TR complementary DNA in antisense ori-They acquire iron by many pathways, including TRentation relative to a human cytomegalovirus promoter/ mediated uptake of iron from transferrin, 1 iron taken enhancer element. Cell clones were obtained that exup by from desialylated transferrin through the asiapressed a 50% to 60% reduction in cell surface TR, leadloglycoprotein receptor, 2 iron carried by ferritin, 3,4 and ing to a corresponding decrease in transferrin and iron uptake compared with wild-type cells. Uptake of trans-transferrin-iron secured by a non-transferrin receptorferrin by a second process was nonsaturable and not mediated process 5 (NTR). The TR-mediated uptake of inhibited by a 100-fold excess of unlabeled transferrin. transferrin-iron has been studied extensively, particuThe amounts of transferrin taken up by the wild-type larly in the developing erthyroid cell. 6 The receptorand antisense cells by this process were similar, showing mediated process involves the binding of transferrin to that it did not involve TR. The proteolytic enzyme Pro-a cell surface TR, internalization of the transferrin-TR nase reduced the uptake of transferrin, suggesting that complex into an endocytotic vesicle, the release of iron the NTR-mediated process entailed the nonsaturable from transferrin, and transport into the cell cytosol and binding of transferrin to plasma membrane proteins.the recycling of the apotransferrin-TR complex to the This process, like the TR-mediated one, involved the incell surface, where the apotransferrin is released.7 By ternalization and recycling of transferrin, leading to accumulation of iron with time. Iron uptake mediated by contrast, the other processes of iron delivery, especially NTR process was saturable and displaced by 100-fold the TR-independent uptake of transferrin-iron, have excess unlabeled transferrin and reduced by weak bases not been well characterized. and metabolic inhibitors. Therefore, the NTR-mediatedIn an earlier study from this laboratory, data were process entailed transferrin adsorption to membrane-presented indicating that the uptake of iron from transbound proteins, internalization, and release of iron from ferrin by isolated hepatocytes was dependent on the transferrin by a pH-dependent step followed by the in-extracellular transferrin concentration. Received July 13, 1995; accepted December 29, 1995. ical importance of...

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“…the N-terminal lobe of the protein. 27,28 The proteoglycan-transferrin-binding activity was also sensitive to…”

Section: P0e$$0043mentioning

confidence: 99%

Transferrin receptor-independent uptake of differic transferrin by human hepatoma cells with antisense inhibition of receptor expression

1996

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“…The HS binding capacity of the three scFvs were analyzed with heparin LC. Although heparin and HS are structurally different molecules, both consist of sulfated glycosaminglycan chains, and ligands that can bind heparin can also bind HS 32,37,[52][53][54] . Importantly, it has been shown that transferrin binds both heparin and HS 37,53 .…”

Section: Discussionmentioning

confidence: 99%

“…Although heparin and HS are structurally different molecules, both consist of sulfated glycosaminglycan chains, and ligands that can bind heparin can also bind HS 32,37,[52][53][54] . Importantly, it has been shown that transferrin binds both heparin and HS 37,53 . The HS(+)scFv8D3 mutant was able to bind the heparin column and was eluted in two peaks.…”

Section: Discussionmentioning

confidence: 99%

Introducing or removing heparan sulfate binding sites does not alter brain uptake of the blood-brain barrier shuttle scFv8D3

Rosa

Metzendorf

Morrison

et al. 2022

Preprint

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The blood-brain barrier (BBB) greatly limits the delivery of protein-based drugs into the brain and is a major obstacle for the treatment of brain disorders. Targeting the transferrin receptor (TfR) is a strategy for transporting protein-based drugs into the brain, which can be utilized by using TfR-binding BBB transporters, such as the TfR-binding antibody 8D3. In this current study, we investigated if binding to heparan sulfate (HS) contributes to the brain uptake of a single chain fragment variable of 8D3 (scFv8D3). We designed and produced a scFv8D3 mutant, engineered with additional HS binding sites, HS(+)scFv8D3, to assess whether increased HS binding would improve brain uptake. Additionally, a mutant with a reduced number of HS binding sites, HS(-)scFv8D3, was also engineered to see if reducing the HS binding sites could also affect brain uptake. Heparin column chromatography showed that only the HS(+)scFv8D3 mutant bound HS in the experimental conditions. Ex vivo results showed that the brain uptake was unaffected by the introduction or removal of HS binding sites, which indicates that scFv8D3 is not dependent on the HS binding sites for brain uptake. Conversely, introducing HS binding sites to scFv8D3 decreased its renal excretion while removing them had the opposite effect.

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“…3B). The ability of transferrins to interact with heparin was described to depend on its iron content and pH 21 . The occurrence of serotransferrin both in the H − and H + fractions of prostate secretion might be explained by its different iron content.…”

Section: Discussionmentioning

confidence: 99%

Characterization of Proteins from Boar Prostate

Maňásková

Ryšlavá

Tichá

et al. 2002

American J Rep Immunol

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Presented results demonstrate composition of the main proteins of boar prostate secretion. Beta-Microseminoprotein was found to be a major protein of prostate secretion. PSP I and PSP II, major proteins of the H- fraction of boar seminal plasma, were found in boar prostate secretion in lower amounts. The major proteins of the H+ fraction of boar seminal plasma (AQN, AWN) were not detected in prostate secretion.

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Interaction of transferrin and its iron-binding fragments with heparin.

Cited by 12 publications

References 30 publications

Transferrin receptor-independent uptake of differic transferrin by human hepatoma cells with antisense inhibition of receptor expression

Transferrin receptor-independent uptake of differic transferrin by human hepatoma cells with antisense inhibition of receptor expression

Introducing or removing heparan sulfate binding sites does not alter brain uptake of the blood-brain barrier shuttle scFv8D3

Characterization of Proteins from Boar Prostate

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