Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Transferrin”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,729 records · Page 96Linked to original sources
PubMed1983

Human lactotransferrin: molecular, functional and evolutionary comparisons with human serum transferrin and hen ovotransferrin.

In this review article, human lactotransferrin is compared to human serum transferrin and hen ovotransferrin. For the first time the possibility of a 6-fold internal homology of the transferrins is raised: a scheme in which 6 domains are defined is reported; two of them with the highest homology seem to be implicated in the 2 iron binding sites of each transferrin. The location of the disulfide bridges of the 3 transferrins and of their prosthetic sugar groups is discussed: some not yet described half-cystine containing lactotransferrin peptides are indicated.

Amino Acid Sequence↗
PubMed1981

Differential effects of dimethyl sulfoxide and sodium butyrate on alpha-fetoprotein, albumin, and transferrin production by rat hepatomas in culture.

Radioimmunoassay was used to determine alpha-fetoprotein (AFP), albumin, and transferrin production (ng/10(5) cells/24 h) by two cell lines (7777 and 8994) derived from chemically induced rat hepatomas. alpha-Fetoprotein production was high (2000 to 4400) in 7777, but was very low (0.2 to 0.4) in 8994. Albumin production varied from 0.4-0.8 (7777) to 14-26 (8994). Both lines produced substantial amounts of transferrin (180 to 240 by 7777 and 29 to 42 by 8994). Addition of dimethyl sulfoxide (DMSO, 1 to 4%) or sodium butyrate (BA, 0.5 to 2.0 mM) to the medium inhibited growth in both lines, but 8994 was more sensitive to these agents than 7777. Dimethyl sulfoxide treatment (2 to 4%) resulted in a dose-related decrease (less than 10% of control at 4% DMSO) in AFP, albumin, and transferrin production by 7777, but in 8994, DMSO (1 to 2%) resulted in an increase (up to sixfold) in albumin and transferrin production, without affecting AFP production. By contrast, BA (2 to 4 mM) stimulated the production of all three proteins in both lines, most notably that of albumin (up to sixfold) by 7777 and that of AFP (up to 20-fold) by 8994. It is concluded that both DMSO and BA can enhance the expression of differentiated functions of the hepatoma cell, and that DMSO at the same time can suppress the expression of an oncofetal function. However, neither DMSO nor BA is selective in its effects on specific genes (i.e., normal, adult vs. oncofetal genes), and it appears that their effects may be the result of a more general phenomenon, the expression of which may be related to the stage of differentiation of the cell.

Albumins↗
PubMed1987

Purification and identification of transferrin as a major pituitary-derived mitogen for MTW9/PL2 rat mammary tumor cells.

Transferrin was identified as a major tissue-derived growth factor for MTW9/PL2 rat mammary tumor cells. Mitogenic activity was assayed by the ability to stimulate the increase in number of MTW9/PL2 cells over 4 d in Dulbecco's modified Eagle's medium containing only 15 mM HEPES, 2 mM glutamine, and 50 micrograms/ml gentamicin. This growth-promoting activity was purified from ammonium sulfate precipitates of phosphate buffered saline extracts of porcine pituitaries using DEAE-Sepharose, chromatofocusing, molecular sieve chromatography and reverse phase high performance liquid chromatography. Pig pituitary mitogen (PPM) migrated as a single band at molecular weight 78,000 on sodium dodecyl sulfate polyacrylamide gel electrophoresis, eluted from chromatofocusing at multiple pH values near 6.3, exhibited an absorption maximum at 465 nm which was diminished by removal of iron, showed a characteristic salmon-pink color in aqueous solution, and was similar in amino acid composition to previously reported values for porcine transferrin. Purified PPM stimulated the growth of MTW9/PL2 cells with mitogenic potency (ED50 = 190 to 280 ng/ml) similar to commercially available human transferrin (ED50 = 160 to 350 ng/ml). We have concluded that using serum-free assay conditions with MTW9/PL2 cells, transferrin was a major source of the mitogenic activity present in extracts of porcine pituitary.

Amino Acids↗
PubMed1984

Effects of ferrous iron and transferrin on cell proliferation of human diploid fibroblasts in serum-free culture.

Iron-free RITC 80-7 defined medium was used to examine effects of ferrous iron and transferrin on cell proliferation of human diploid fibroblasts. Both ferrous iron and holo-transferrin stimulated cell proliferation in the medium, but apotransferrin did not. When 5 g/l human serum albumin (HSA) was added to the defined medium, excellent growth was obtained under hypoxic conditions, whereas a reduction of cellular growth during the culture periods was observed under aerobic conditions. When ferrous iron was added to the HSA medium alone, the reduction in growth increased in proportion to the concentrations, whereas the addition of transferrin prevented this reduction in a concentration-dependent manner. This suggests that the ferrous iron concentration in media causes a reduction in growth under aerobic conditions and transferrin prevents this reduction because it decreases the ferrous iron concentration. Further, serum albumin seems to be a source of iron in media.

Aerobiosis↗
PubMed1984

Effect of lactoferrin on the growth of a human colon adenocarcinoma cell line--comparison with transferrin.

Lactoferrin was examined for its effect on the growth of a human colon adenocarcinoma cell line (HT 29) in culture and its action was compared to that produced by transferrin and two different iron solutions (ferrous sulfate and ferric chloride). When transferrin was replaced by either iron solutions the cell grew in proportion to the quantity added and the maximal effect obtained was identical to that produced by transferrin alone. When transferrin was replaced by lactoferrin the cells were unable to proliferate for a long time. However, in the presence of low-concentration iron solutions, lactoferrin stimulated the cell growth, and the effect was more pronounced with the ferric chloride solution.

Adenocarcinoma↗
PubMed1982

Transferrin support of stimulated lymphocytes.

Transferrin was tested for its ability to replace serum in supporting mitogen and allogeneic cell stimulated human lymphocyte proliferation. Although transferrin, at concentrations greater than 5 microgram/ml, was incapable of completely replacing the serum used to support phytohemagglutinin, Concanavalin A, and pokeweed mitogen, stimulated human lymphocytes, in the absence of serum it significantly augmented the proliferative responses observed for mitogen, yet not allogeneically-stimulated cells. Augmentation is not due to a nonspecific protein effect and appears to be independent of the metal content of transferrin. The mechanism of growth support appears to involve an effect of transferrin following the G1 phase in the initial cell cycle.

Cells, Cultured↗
PubMed1990

67Ga in transferrin-unbound form is taken up by inflamed liver of mouse treated with CCl4.

In order to investigate whether or not transferrin is involved in the uptake of 67Ga by inflamed liver (acute inflammatory tissues) the uptake of 67Ga by the liver of mice treated with carbon tetrachloride (CCl4) was studied. The serum GPT value reached its maximum on the 1st day after the CCl4 treatment. The uptake of 67Ga by the liver also reached its maximum on the 1st day after the CCl4 treatment and the amount uptaken into inflamed liver was about 6 times that uptaken into normal liver. On the other hand, the uptake of 125I-transferrin into inflamed liver on the 1st day after CCl4 treatment was only about 1.6 times that into normal liver. Moreover, cold Fe3+ decreased the uptake of 67Ga by normal liver but increased the uptake of 67Ga by inflamed liver. These results show that transferrin plays an important role in the uptake of 67Ga by normal liver but not by inflamed liver, i.e. 67Ga in the transferrin-unbound form is preferentially taken up by inflamed liver.

Animals↗
PubMed2006

Molecular evolution of the transferrin receptor/glutamate carboxypeptidase II family.

The transferrin receptor family is represented by at least seven different homologous proteins in primates. Transferrin receptor (TfR1) is a type II membrane glycoprotein that, as a cell surface homodimer, binds iron-loaded transferrin as part of the process of iron transfer and uptake. Other family members include transferrin receptor 2 (TfR2), glutamate carboxypeptidase II (GCP2 or PSMA), N-acetylated alpha-linked acidic dipeptidase-like protein (NLDL), N-acetylated alpha-linked acidic dipeptidase 2 (NAALAD2), and prostate-specific membrane antigen-like protein (PMSAL/GCPIII). We compared 86 different sequences from 24 different species, from mammals to fungi. Through this comparison, we have identified several highly conserved residues specific to each family not previously associated with clinical mutations. The evolutionary history of the TfR/GCP2 family shows repeated episodes of duplications consistent with recent theories that nondispensable, slowly evolving genes are more likely to form multiple gene families.

Amino Acid Sequence↗
PubMed2000

Serum transferrin receptor in children and adolescents with inflammatory bowel disease.

UNLABELLED: Iron studies are difficult to interpret in patients with chronic inflammatory states such as inflammatory bowel disease (IBD). Serum transferrin receptor (TfR) has been reported to be a reliable tool for the diagnosis of iron deficiency in adults. Our aim was to evaluate the role of serum TfR in diagnosing iron deficiency in children and adolescents with IBD. A total of 63 consecutive patients with IBD, aged 9 to 22 years (median 15 years), were tested for serum haemoglobin level, mean corpuscular volume (MCV), and serum iron, transferrin, ferritin and serum TfR levels. Those found to be anaemic were compared with seven age-matched subjects with iron deficiency anaemia (IDA) and 24 age-matched children without signs of anaemia or inflammation. Of the 63 patients with IBD, 26 had anaemia. Based on ferritin levels and MCV indices, anaemia was classified as IDA in 11 patients and as anaemia of chronic disease (ACD) in 15 patients. Mean serum TfR level in normal controls was 3.5 mg/l (range 1.2-8.2 mg/l). Mean (+/-SD) serum TfR levels were significantly lower in the IBD patients with ACD (5.3 +/- 2.3 mg/l) than in the IBD patients with IDA (8.2 +/- 3.1 mg/l) (P < 0.05). Serum TfR levels above 5 mg/l identified 10/11 IBD patients with IDA. The calculated TfR/ferritin ratio was 84 (range 17-367) for controls and 133 (range 6.4-1840) for IBD patients. A cut-off level of 350 (91% sensitivity, 100% specificity, 100% positive predictive value, 98% negative predictive value) was established for the diagnosis of IDA in IBD. CONCLUSION: The results suggest that serum transferrin receptor is a useful parameter for the diagnosis of iron deficiency in inflammatory bowel disease, in particular, the transferrin receptor/ferritin ratio with a cut-off level > or = 350.

Adolescent↗
PubMed2006

Characterisation of recombinant unglycosylated human serum transferrin purified from Saccharomyces cerevisiae.

Structural identity between a recombinant transferrin mutant (N413Q, N611Q) secreted from Saccharomyces cerevisiae and the native protein was shown by CD analysis and immunodiffusion assays against anti-hSTf. The ability of the recombinant protein to bind iron was confirmed by urea-PAGE and EPR analysis of the iron-saturated protein revealed the characteristic holo-transferrin spectrum, indicating conservation of both iron-binding sites. The integrity of the unglycosylated recombinant protein indicates that such protein could be a valuable tool not only for structure-function characterisation but also crystallisation assays. In addition, the recombinant transferrin was found to be as effective as native transferrin as a growth factor in cell culture medium.

Cell Proliferation↗
PubMed2002

Serum citrate levels, haptoglobin haplotypes and transferrin receptor (CD71) in patients with HIV-1 infection.

BACKGROUND: The progression of HIV-1 infection towards its more advanced stages is accompanied by changes in iron metabolism and increased body iron stores. PATIENTS AND METHODS: Given the ability of HIV to alter iron metabolism, we studied the principal (transferrin system) and alternative (citrate system) iron pathways in a group of 65 HIV-infected patients (symptomatic stage B1-B3) and in a group of 36 healthy seronegative individuals. We determined serum citrate levels, haptoglobin (Hp) haplotypes, expression of transferrin receptor (CD71) on cell lines infected with HIV-1 as well as iron markers including blood iron, transferrin and ferritin. RESULTS: Our data showed decreased serum citrate levels in the HIV-infected patients compared to controls (92.9 +/- 22.4 microM/l vs 126.2 +/- 29.2 microM/L; p < 0.01). In particular, the serum citrate levels negatively correlated with HIV-1 RNA copy number (mean: 2.53 +/- 1.88 x 10(5)/ml, r(s) = 0.70, p < 0.01) and positively correlated with CD4+ T-lymphocyte count (mean: 241 +/- 168/ml, r(s) = 0.64, p > 0.05). Accordingly, blood iron, transferrin and red cell concentrations were lower in HIV-infected patients compared to the controls, whereas serum ferritin levels were higher in HIV-infected patients. Moreover, the Hp haplotype distribution showed significant differences only in the group of HIV-infected patients (p = 0.02; chi2 test). CONCLUSION: Our results show that iron metabolism is altered in patients with HIV-1 infection. The alternative pathway (citrate system) is particularly affected, since when citrate levels are low, both aconitase activity and HIV-1 replication need iron.

Adult↗
PubMed1985

Localization of transferrin receptor in the chorionic villi of complete molar pregnancy.

Transferrin receptors have been identified on the villous trophoblast of normal chorionic villi by immunohistochemical techniques. The current study investigated the expression of transferrin receptors on molar chorionic villi by using a monoclonal antibody in immunofluorescence assays. The villous trophoblast of molar chorionic villi was brightly positive for transferrin receptor in the immunofluorescence assay. The presence of transferrin receptors on molar villous trophoblast may influence the immunologic relationship between molar and host tissues.

Antibodies, Monoclonal↗
PubMed1992

Magnetic cell sorting and the transferrin receptor as potential means of prenatal diagnosis from maternal blood.

OBJECTIVE: We wanted to test whether the recently described method of using the transferrin receptor system for fluorescence-activated cell-sorter enrichment of nucleated red blood cells can be used for prenatal diagnosis from maternal blood. STUDY DESIGN: Instead of the laborious, expensive fluorescence-activated cell-sorter system, we used the newly described magnetic-activated cell sorter. RESULTS: An effective enrichment could be achieved with separation of lymphocyte subsets. With the transferrin receptor, however, the enrichment was very inefficient because of the poor specificity of the antibody itself. Even in umbilical cord blood only 25% of nucleated red blood cells were labeled as demonstrated by immunogold silver enhancement of transferrin receptor-labeled cells. CONCLUSION: In spite of the availability of a fast and effective separation method (magnetic-activated cell sorter) the use of the transferrin receptor antigen alone is not likely to enable a reliable identification of fetal cells in maternal circulation.

Cell Separation↗
PubMed1988

Incorporation of myristate and palmitate into the sheep reticulocyte transferrin receptor: evidence for identical sites of labeling.

The ability of sheep reticulocytes and plasma membranes isolated from them to incorporate fatty acids into the transferrin receptor has been examined using both [3H]palmitate and [3H]myristate. Both fatty acids, when incorporated into the transferrin receptor, can be released by treating the protein with 1 M hydroxylamine at pH 7.0. After treatment of the 3H-acylated receptor with borohydride, an 3H-labeled alcohol is released, suggesting that the receptor-bound fatty acid is in thioester linkage. With both [3H]myristate and [3H]palmitate, Cleveland maps from immunoprecipitates of the transferrin receptor labeled in intact cells and isolated membranes show that identical peptides are labeled. No evidence was obtained for qualitatively different labeling with the two fatty acids. In intact reticulocytes, incorporation of [3H]palmitate into the transferrin receptor is approximately 3.5 times greater than the incorporation of [3H]myristate from equivalent concentrations of the labeled fatty acids. However, in isolated reticulocyte plasma membranes, there is much less difference between palmitate and myristate incorporation (with ATP) or between their acyl-CoA derivatives. The reason for the discrepancy between cells and membranes is unknown but may be due to the presence in intact cells of more than one enzyme for activating the fatty acids. Acylation of the receptor in isolated plasma membranes is fourfold greater with the CoA derivatives than with the free fatty acids. The fatty acid activating enzyme(s) as well as the acyltransferase(s) appear to be membrane bound in reticulocytes.

Acylation↗
PubMed1976

The effect of trypsin on bovine transferrin and lactoferrin.

The iron-saturated and iron-free (apo) forms of bovine transferrin and lactoferrin were digested with trypsin and the digests analysed by column chromatography and electrophoresis. Both of the iron-saturated proteins were more resistant to proteolysis than the corresponding apoproteins, and iron-transferrin was more resistant than iron-lactoferrin. Digestion of iron-transferrin yielded two iron-binding fragments with molecular weights of 32 000 and 38 500 whereas apotransferrin yielded only the larger fragment. In digests of lactoferrin, up to five different fragments with molecular weights ranging from 25 000 to 52 700 were detected, there being no obvious qualitative difference between digests of iron-lactoferrin and apolactoferrin. The susceptibility of apolactoferrin to tryptic digestion was only slightly reduced when apolactoferrin was complexed with beta-lactoglobulin, suggesting that complex-formation is not a mechanism for protecting lactoferrin against intestinal degradation. There was no immunological cross reaction between bovine transferrin or its digestion products against anti-lactoferrin antiserum, or vice-versa.

Animals↗
PubMed1977

The cross-linking of 125I-labelled transferrin to rabbit reticulocytes.

125I-labelled transferrin has been covalently linked to proteins of rabbit reticulocyte membranes using three different cross-linking reagents: (a) bis(methyl) suberimidate (b) 4-methyl mercaptobutirimidate and (c) Cu-o-phenanthroline. Analysis of the products of the cross-linking reactions by SDS polyacrylamide gel electrophoresis revealed three radioactively labelled components. The major component corresponds to non-cross-linked transferrin while a second smaller component represents a complex (125 000 daltons) of membrane protein and transferrin. A third component (210 000 daltons) was observed when 4-methyl mercaptobutirimidate was used as a cross-linking reagent. The possibility that the two higher molecular weight complexes contain the receptor protein for transferrin is discussed.

Animals↗
PubMed1977

The isolation and partial characterization of transferrin binding components of the rabbit reticulocyte plasma membrane.

An affinity chromatograpy method utilising transferrin liganded agarose has been developed for the partial purification of transferrin binding components from Triton X-100 solubilised rabbit reticulocyte plasma membranes. A protein of molecular weight 30-35 000, shown to be located at the reticulocyte extra-cellular surface by lactoperoxidase 125I labelling, was isolated by the affinity method. The protein appeared to form a dimer of molecular weight 65-70 000 in Triton X-100 solution and was shown to associate with both 125I-labelled and unlabelled rabbit transferrin to form a high molecular weight complex in the same solution. N-[14C]Ethylmaleimide appeared to disrupt this association with transferrin and inhibit the formation of the dimer in Triton X-100 by binding to the protein. The protein appeared as a broad band of molecular weight 40 000 on sodium dodecyl sulphate polyacrylamide gel electrophoresis.

Animals↗
PubMed1979

Studies on the mechanism of iron release from transferrin.

Iron release from human, rabbit, rat and sheep transferrin, chicken conalbumin and human lactoferrin was measured by the change in absorbance of solutions of the iron-protein complexes or by the release of 59Fe from the protein conjugated to agarose. Several phosphatic compounds and iron chelators were able to mediate the process (ATP, GTP, 2,3-diphosphoglycerate, inositol hexaphosphate, pyridoxal 5-phosphate, cytidine 5-triphosphate, pyrophosphate, inorganic phosphate, citrate, EDTA, oxalate, nitrilotriacetate). The greatest rate of iron release was found with pyrophosphate and the least with inorganic phosphate. Different rates of iron release were obtained with the different proteins, greatest with human transferrin and least with lactoferrin. With each of the proteins and the mediators there was a linera relationship between the H+ concentration and the rate of iron release. At any given pH the rate of iron release increased to a maximal rate as the mediator concentration was raised. It is concluded that iron release from transferrin under the conditions of these experiments involves an initial interaction between H+ and the iron-transferrin complex followed by release of the iron under the action of the mediator.

Animals↗