Transferrin receptor synthesis | …
No evidence exists supporting this contention, however. Blockade of transferrin receptor function can halt cell division.
Transferrin Receptor Induction in Mitogen ..
Because maturing red cells shed their transferrin receptors, the quantity of soluble transferrin receptor in plasma reasonably reflects erythropoiesis.
The results suggest that the depletion of cellular nonâheme iron due to the increase in heme synthesis maintains a high level of transferrin receptor expression in differentiating erythroid cells even after the cessation of cell division.">
Transferrin and its receptor appear to be ..
The results suggest that the depletion of cellular nonâheme iron due to the increase in heme synthesis maintains a high level of transferrin receptor expression in differentiating erythroid cells even after the cessation of cell division.
These studies were performed to determine whether the reticulocyte can synthesize its own transferrin receptor and, if so, whether synthesis is subject to translational control by intracellular heme. Reticulocytosis (20-35%) was produced by bleeding rabbits and the washed cells were incubated for 1-4 h at 37 degrees C in buffered nutritional medium containing L-[35S]methionine. After washing and detergent lysis in the presence of protease inhibitors, supernatant reticulocyte extracts were analyzed for transferrin receptors by immunoprecipitation with specific ovine receptor antibody raised against denatured rabbit transferrin receptor. Immunoprecipitates were analyzed by SDS-gel electrophoresis and fluorography. Antibody, but not preimmune sheep immunoglobin, consistently precipitated a 35S-labeled protein with an Mr of 90,000 (reduced), coincident with bona fide receptor subunits purified by ligand-affinity chromatography. Incorporation of radioactive methionine was exclusively associated with receptor in reticulocyte stroma, and nascent receptor was not detected on free polyribosomes. Incorporation of radioactivity in the receptor moiety accounted for 0.1-0.2% of total incorporation into TCA insoluble cell protein. Treatment of the cells with 40 micrograms/ml cycloheximide markedly inhibited amino acid incorporation into the receptor, thus indicating de novo synthesis of receptor protein. On treatment of reticulocytes with 4,6 dioxoheptanoate to induce heme deficiency by diminishing the formation of intracellular heme, synthesis of the receptor was inhibited by greater than 50%; synthesis was restored to control rates on addition of 50 microM exogenous hemin. These findings indicate that the reticulocyte retains receptor mRNA and that synthesis of the receptor in erythroid cells is subject to translational regulation by intracellular heme.
Transferrin receptor and B‐lymphoblast antigen — …
Combinations of anti-transferrin receptor monoclonal antibodies inhibit human tumor cell growth in vitro and in vivo: evidence for synergistic anti-proliferative effects.
We have purified a glycoprotein from chicken sciatic nerves, sciatin, which has pronounced trophic effects on avian skeletal muscle cells in culture. Recent studies have shown that sciatin is identical to the iron-transport protein, transferrin, in terms of its physicochemical structure, immunological reactivity, and biological activity. To determine whether transferrin is synthesized and released by neuronal tissue, we incubated cultures of dissociated chicken spinal neurons in a medium free of L-leucine containing either L-3H-amino acids or L- [14C]leucine and immunoprecipitated transferrin with highly specific antibodies. The radiolabeled protein precipitated by rabbit heteroclonal, goat heteroclonal, or mouse monoclonal antitransferrin antibodies increased in specific activity in a linear manner for at least 30 min. Synthesis of this protein was abolished by the presence of puromycin (20 micrograms/ml) or cycloheximide (10(-5) M). The disappearance of the radiolabeled protein from cells was linear with a half-life (t 1/2) of 8-10 h. When immunoprecipitates were separated by SDS gel electrophoresis, a prominent band corresponding to transferrin (Mr 84,000) was visualized by staining with Coomassie Blue. However, when such gels were fluorographed, no radioactivity was apparent in the transferrin region of the gel although a prominent radioactive band was visualized at an Mr of 56,000. The protein of Mr 56,000 was not simply a degradation product of transferrin because this particular protein band was not generated by incubating radiolabeled transferrin with unlabeled neuronal homogenates. The protein of Mr 56,000 was purified from embryonic chicken brain and spinal cord by immunoabsorption chromatography on mouse monoclonal antitransferrin IgG conjugated to Sepharose 4B followed by affinity chromatography on immobilized transferrin. The purified protein bound radioiodinated transferrin and was precipitated by rabbit anti-chicken transferrin-receptor antibodies. Furthermore, this receptor protein was found to be localized on the plasma membrane of dorsal root ganglion neurons by immunocytochemistry using the peroxidase-antiperoxidase technique, and by blocking experiments, which showed that antitransferrin receptor IgG could inhibit the binding of fluorescein-conjugated transferrin at 4 degrees C to cultured neurons in vitro. From these data, we conclude that transferrin is not synthesized by cultures of chicken spinal cord neurons, but that the receptor for transferrin is synthesized by these cultures and is precipitated by antitransferrin antibodies as an antigen-receptor complex.
Synthesis of the transferrin receptor by ..
Soluble Transferrin Receptor (sTfR): R&D Systems
The density of transferrin receptors on the cell surface changes during erythroid maturation.
Read our article on Soluble Transferrin Receptor (sTfR)
The antibody apparently prevented normal cycling of transferrin receptors, and inhibited efficient iron uptake.
03/02/2011 · Transferrin receptor ..
Induction of T cell activation by monoclonal antibodies specific for the transferrin receptor.
Mechanism of Decrease in Transferrin Receptor Synthesis …
For instance, certain monoclonal antibodies against the transferrin receptor curb proliferation of tumor cells and (Lesley and Schulte, 1985); (White et al., 1990).
EP1765868B1 - Transferrin receptor antibodies - …
Some of these antibodies actually prevent binding of transferrin to its receptor, while others suppress receptor recycling but do not abrogate ligand binding (reviewed by Trowbridge et al., 1987).) Interestingly, there are reports suggesting that the transferrin receptor may have an additional role in activated T cells, apart from its iron uptake function.
WikiGenes - Tfrc - transferrin receptor
Anti-transferrin receptor monoclonal antibodies have been described that can trigger T cell activation and interleukin-2 secretion (Manger et al., 1987); (Cano et al., 1990); (Keyna et al., 1994).
Effect of iron on transferrin receptor expression by …
These antibodies presumably activate a signal transduction pathway beginning with the transferrin receptor, but independent of iron trafficking. The central role of iron in cell proliferation is further demonstrated by chelators that can cross the plasma membrane, bind the metal inside the cell, and limit its bioavailability.
Transferrin receptor expression has ..
Along the same lines, tumor cells upregulate transferrin receptor expression to optimize iron acquisition for proliferation. When stimulated to proliferate, T-lymphocytes also synthesize and secrete transferrin (Bowman).
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Transferrin (Tf) is a growth factor that transports iron in plasma. It is essential for proliferation of activated T lymphocytes. Previous studies have suggested that peripheral blood cells are capable of synthesizing Tf. Using in situ hybridization techniques and human Tf complementary DNAs as probes, peripheral blood cells have been examined for sites of Tf messenger RNA (mRNA) transcription. The studies described here demonstrate that Tf is synthesized by a specific subset of T lymphocytes, the T4+ inducer subset. T lymphocyte proliferation is dependent upon the presence of both interleukin 2 (IL-2) and Tf, even though resting cells do not possess receptors for either. The present studies indicate that during T cell activation, induction of IL-2 mRNA transcription and IL-2 receptor expression precede the transcription of Tf mRNA and expression of Tf receptors, respectively. These events in turn precede the initiation of DNA synthesis. Transferrin and its receptor appear to be involved in an autocrine pathway which is functionally linked to the IL-2/IL-2 receptor autocrine loop.
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