Carrier transferrin

Chowers, I, Wong, R, Dentchev, T, Farkas, RH, Iacovelli, J, Gunatilaka, TL, Medeiros, NE, Presley, JB, Campochiaro, PA, Curcio, CA, Dunaief, JL, and Zack, DJ, 2006. The iron carrier transferrin is upregulated in retinas from patients with age-related macular degeneration. Invest Ophthalmol Vis Sci 47, 2135-2140. 

Transport Ceruloplasmin (copper carrier), transferrin (iron carrier)... 

Using cultured mammalian sarcoma cells, it has been found that transferrin is necessary in the growth medium for galllum-67 uptake to occur (95,96.97). A "transferrin receptor" on EMT-6 sarcoma cells for 25i iabeled transferrin was characterized by Scatchard analysis to have an average association constant K = 4.54 X 10 1/mole and approximately (with variation) 500,000 receptors per cell ( ). It was proposed that tumor accumulation of galllum-67 can occur only if the metal is complexed with transferrin so that it can interact with the receptors of tumor, as well as non-mallgnant cells (.33). The complex then enters the cell via an "adsorptive endocytosis" process (95.96.97.98.99) similar to the manner in which iron is taken up by reticulocytes and bone marrow cells (100.101). These transferrin receptors are saturable (that is, a plot of 125i transferrin uptake versus extracellular transferrin concentration reaches a peak ( at about 200 u g/ml) as more carrier transferrin is added to the medium) (95). Since uptake is also proportional to the fraction of... 

FIG. 15 Cellular entry and intracellular kinetics of the cationic lipid-DNA complexes. Cationic lipid-DOPE liposomes form electrostatic complexes with DNA, and, in this case, also transferrin (Tf) is incorporated. Cellular uptake by endoc5dosis and endosomal acidification can be blocked with cytochaiasin B and bafilomycin Aj, respectively. DNA is proposed to be released at the level of endosomal wall after fusion of the carrier lipids with endosomal bilayer. This process is facilitated by the formation of inverted hexagonal DOPE phase as illustrated in the lower corner on the right. After its release to the C5doplasm DNA may enter the nucleus. (From Ref. 253. By permission of Nature Publishing Group.)... 

Even though the specific protein that binds the lanthanides may or may not be transferrin, the behavior of high-specific activity lanthanides (< 1 jtM/kg7) compared with that of lanthanides administered with significant amounts of stable carrier strongly suggests the kind of break-through one would expect if a protein transport system were overloaded. As long as the amount of lanthanide introduced into the... 

Wagner E, Zenke M, Cotten M, Beug H, Bimstiel ML (1990) Transferrin-polycation conjugates as carriers for DNA uptake into cells. Proc Natl Acad Sci USA 87 3410-3414... 

Transferrin is an iron carrier protein that acts as a trophic survival factor for neurons, astrocytes and OLs. As the blood-brain barrier becomes established during development, neural cells become dependent on transferrin produced by OLs and choroid plexus epithelial cells (Fig. 25-14). OLs are the major source of transferrin in the CNS. This suggests an important function for OLs in... 

Welch, S. (1992) Transferrin The Iron Carrier, CRC Press, Boca Raton, Florida... 

Very little is known about the transport of nickel, manganese and cobalt. Plasma transferrin, conalbumin and citrate have been suggested to serve as carrier ligands. Transferrin is the main transport protein for vanadium in humans, and will transfer vanadium to ferritin. 

Boado et al. [28] devised delivery systems based on conjugates of streptavidin and the 0X26 monoclonal antibody directed to the transferrin receptor as a carrier for the transport of ASO. These delivery systems were found to transport peptide nucleic acid antisense molecules, but not ASO, across the BBB. These authors attributed this difference to preferential binding of phosphorothioate oligonucleotide to plasma protein instead of the antibody complex, which reduced their transport. 

Other mechanisms are also involved in the reticulocyte-mediated release of iron from transferrin, and its subsequent incorporation into heme. Intact oxidation-reduction pathways are essential and seem to operate at a step following the attack on the anion (90). Heme exerts an inhibitory influence on iron transfer from protein to cell, seemingly by interfering at an early stage in the release of the metal from transferrin (89). Non-transferrin carriers for iron have also been identified in the reticulocyte and may participate in its incorporation into heme (81). 

Because most of the first transition series elements are essential in biological systems there is considerable interest in the possibility that transferrins may be involved in their binding and translocation. This is certainly a distinct possibility, because neither transferrin nor lactoferrin is more than 30% saturated with iron in body fluids. There is as yet little hard evidence, however. Transferrin has been reported to be the main carrier for manganese in blood (158), just as lactoferrin is in milk (25), and thermodynamic studies suggest that transferrin is also capable of competing with serum albumin for zinc under the... 

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