scholarly journals Exposure of K562 cells to anti-receptor monoclonal antibody OKT9 results in rapid redistribution and enhanced degradation of the transferrin receptor.

1986 ◽  
Vol 102 (3) ◽  
pp. 951-958 ◽  
Author(s):  
A M Weissman ◽  
R D Klausner ◽  
K Rao ◽  
J B Harford
Keyword(s):  
Monoclonal Antibody ◽  
Transferrin Receptor ◽  
Half Life ◽  
Iron Uptake ◽  
K562 Cells ◽  
Lower Percentage ◽  
Cellular Iron ◽  
Cellular Iron Uptake ◽  
Small Change ◽  
Transferrin Cycle

When the human erythroleukemia cell line K562 is treated with OKT9, a monoclonal antibody against the transferrin receptor, effects on receptor dynamics and degradation ensue. The apparent half-life of the receptor is decreased by greater than 50% as a result of OKT9 treatment. The transferrin receptor is also rapidly redistributed in response to OKT9 such that a lower percentage of the cellular receptors are displayed on the cell surface. OKT9 treatment also leads to a decrease in the total number of receptors participating in the transferrin cycle for cellular iron uptake. The reduction in iron uptake that results from the loss of receptors from the cycle leads to enhanced biosynthesis of the receptor. Receptors with bound OKT9 continue to participate in multiple cycles of iron uptake. However, OKT9 treatment appears to result in a relatively small increase per cycle in the departure of receptors from participation in iron uptake to a pathway leading to receptor degradation. Radiolabeled OKT9 is itself degraded by K562 cells and this degradation is inhibitable by leupeptin or chloroquine. In the presence of leupeptin, OKT9 treatment results in the enhanced intracellular accumulation of transferrin. Because the time involved in the transferrin cycle is shorter (12.5 min) than the normal half-life of the receptor (8 h), a small change in recycling efficiency caused by OKT9 treatment could account for the marked decrease in receptor half-life. In this paper the implications of these findings are discussed as they relate to systems in which receptor number is regulated by ligand.

The transferrin receptor: the cellular iron gate

Metallomics ◽  
2017 ◽  
Vol 9 (10) ◽  
pp. 1367-1375 ◽  
Author(s):  
Elena Gammella ◽  
Paolo Buratti ◽  
Gaetano Cairo ◽  
Stefania Recalcati
Keyword(s):  
Transferrin Receptor ◽  
Iron Uptake ◽  
Iron Homeostasis ◽  
Cellular Iron ◽  
Iron Gate ◽  
Cellular Iron Uptake

The transferrin receptor (TfR1), which mediates cellular iron uptake through clathrin-dependent endocytosis of iron-loaded transferrin, plays a key role in iron homeostasis.

scholarly journals Chelation of transferrin iron by desferrioxamine in K562 cells. The partition of iron between ferrioxamine and ferritin

1988 ◽  
Vol 254 (3) ◽  
pp. 869-875 ◽  
Author(s):  
S Roberts ◽  
A Bomford
Keyword(s):  
Cellular Uptake ◽  
Iron Uptake ◽  
Indirect Method ◽  
K562 Cells ◽  
Linear Increase ◽  
Cellular Iron ◽  
Cellular Iron Uptake ◽  
Leukaemic Cells ◽  
High Concentrations ◽  
In Cells

In this study we have determined whether desferrioxamine can chelate iron delivered to human leukaemic cells by the transferrin endocytic cycle. The cellular uptake of desferrioxamine was investigated by an indirect method in which the conversion of repeated pulses of [59Fe]transferrin to [59Fe]ferrioxamine was determined at two concentrations of the drug. Maximum generation of [59Fe]ferrioxamine occurred in cells exposed to either 100 microM- or 500 microM-desferrioxamine after 40-60 min. Thereafter (up to 180 min) [59Fe]ferrioxamine levels remained steady with 20% of a 59Fe pulse partitioning to chelator at 100 microM and 50% at 500 microM. Of the cellular [59Fe]ferrioxamine loss 50% occurred within 90-120 min. In cells preloaded with desferrioxamine for 1 or 4 h the partitioning of iron during a 3 h incubation with [59Fe]transferrin was dependent upon the extracellular concentration of the chelator. Above 1 mM more than 80% of entering iron was converted to ferrioxamine and less than 5% partitioned to ferritin. Below this concentration (50-500 microM) a proportion of the iron became ferritin associated (7-41%). There was a linear increase in the total amount of intracellular [59Fe]ferrioxamine in accordance with cellular iron uptake showing that transferrin continued to cycle in the presence of high concentrations of desferrioxamine. The uptake of iron and generation of ferrioxamine were markedly reduced by 5 mM-methylamine, which prevented endosome acidification and uncoupling of iron from endocytosed transferrin.

Intracellular Ca2+ regulates the cellular iron uptake in K562 cells

Cell Calcium ◽  
2003 ◽  
Vol 33 (4) ◽  
pp. 257-266 ◽  
Author(s):  
Weimin Ci ◽  
Wenyu Li ◽  
Ya Ke ◽  
Zhong-Ming Qian ◽  
Xun Shen
Keyword(s):  
Iron Uptake ◽  
K562 Cells ◽  
Cellular Iron ◽  
Cellular Iron Uptake

The DMT1 Associated Protein (DAP) Regulates Iron Uptake by Erythroid Cells.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 53-53
Author(s):  
Jonathan Glass ◽  
Yi Chen ◽  
Yuxiang Ma ◽  
Mary Yeh ◽  
Kwo-yih Yeh
Keyword(s):  
Amino Acid ◽  
Nuclear Localization ◽  
Transferrin Receptor ◽  
Nuclear Localization Signal ◽  
Iron Uptake ◽  
K562 Cells ◽  
Rich Region ◽  
Cellular Iron ◽  
Localization Signal ◽  
Glutamine Rich Region

Abstract The divalent metal transporter 1 (DMT1) is essential for cellular iron uptake both in the intestine and in erythroid cells. We have previously shown that with iron feeding the DMT1 expressed on the brush border membrane (BBM) of the intestine undergoes endocytosis (Am. J. Physiol. 283, G965, 2002). Using the yeast two-hybrid system we have isolated a cDNA clone encoding a protein of 526-amino acid residues with a calculated molecular mass of 60 kDa, which interacts with the C-terminus of DMT1 expressed from the IRE containing mRNA (Blood ,100, 7a, 2002). The ORF of the rat protein has been fully sequenced (Genbank #AY336075) and is now designated DMT1 associated protein (DAP). DAP is ubiquitously expressed and is especially abundant in the rat intestine and colon. In rat duodenum DAP is colocalized with DMT1 in the BBM. Both by salt and pH elution DAP was demonstrated to be a peripheral membrane protein. With iron feeding both DMT1 and DAP translocate: DAP moves from the BBM to basolateral membrane (BLM) with DMT1 and some of DMT1 undergoes endocytosis and is found in cytopasmic vesicles. Immunoprecipitation and pull-down assays confirm the interaction of DAP and DMT1 in the BBM vesicles (MMBV). We have analyzed the function of DAP by exploring the role of various consensus sequences in the DAP ORF in the cellular localization of the protein. By sequence motif analysis DAP has a nuclear localization signal, Glutamic acid-rich region, Glutamine-rich region, Arginine-rich region, PKC phosphorylation sites and GOLD domain (Golgi dynamics). The region of DAP protein interacting with the COOH-terminal cytoplasmic domain of DMT1(IRE) was found to be from 171aa to 331aa which contains Glutamic acid-rich region, Glutamine-rich region and Arginine-rich region. Immunocytochemistry confirmed that DAP is localized in the nuclei and the Golgi complex of K562, MDCK, Hela, Cos1 cells, and Caco2 (where DAP is found also in BBM). GFP-fusion constructs containing the DAP nuclear localization signal (amino acids 171–277) or GOLD domain (amino acid 278–526) were transfected into COS-1 and K562 cells and specificity of intracellular localization confirmed by fluorescence confocal microscopy. DAP expression was controlled by cellular iron content: Cells which were iron depleted had increased levels of DAP protein while cells which were iron replete had decreased DAP protein. The regulation by iron was post-transcriptional as iron levels had no affect on DAP mRNA. The levels of DAP expression was also seen to affect iron uptake. Over expression of the region of DAP which binds to DMT1 by transfection of the appropriate construct into K562 cells decreased iron uptake as measured by an increase of transferrin receptor expression and decreased levels of ferritin. Elevated DAP had no affect on endogenous DMT1 expression. Conversely, when siRNAs were used to decrease DAP mRNA in K562 cells there was increased iron uptake with decreased expression of transferrin receptor and increased ferritin expression. In these experiments siRNAs reduced DAP expression by about 60%. This is the first demonstration that a protein which interacts with DMT1 can regulate the uptake of iron into the cell and suggests that DAP may act in a regulatory pathway for iron homeostasis.

Marginally excessive iron loading transiently blocks mucosal iron uptake in iron-deficient rats

2014 ◽  
Vol 307 (1) ◽  
pp. G89-G97 ◽  
Author(s):  
Shoko Shinoda ◽  
Shiho Yoshizawa ◽  
Eriko Nozaki ◽  
Kouki Tadai ◽  
Anna Arita
Keyword(s):  
Iron Uptake ◽  
Iron Concentration ◽  
Iron Loading ◽  
Short Acting ◽  
Excess Iron ◽  
Rapid Induction ◽  
Cellular Iron ◽  
Iron Load ◽  
Iron Deficient ◽  
Cellular Iron Uptake

Regular “mucosal block” is characterized by decreased uptake of a normal iron load 3–72 h after the administration of excess iron (generally 10 mg) to iron-deficient animals. We found that short-acting mucosal block could be induced by much lower iron concentration and much shorter induction time than previously reported, without affecting levels of gene expression. A rapid endocytic mechanism was reported to decrease intestinal iron absorption after a high iron load, but the activating iron load and the time to decreased absorption were undetermined. We assessed the effects of 30–2,000 μg iron load on iron uptake in the duodenal loop of iron-deficient and iron-sufficient rats under anesthesia. One hour later, mucosal cellular iron uptake in iron-deficient rats administered 30 μg iron was 76.1%, decreasing 25% to 50.7% in rats administered 2,000 μg iron. In contrast, iron uptake by iron-sufficient rats was 63% (range 60.3–65.5%) regardless of iron load. Duodenal mucosal iron concentration was significantly lower in iron-deficient than in iron-sufficient rats. Iron levels in portal blood were consistently higher in iron-deficient rats regardless of iron load, in contrast to the decreased iron uptake on the luminal side. Iron loading blocked mucosal uptake of marginally excess iron (1,000 μg), with a greater effect at 15 min than at 30 min. The rapid induction of short-acting mucosal block only in iron-deficient rats suggests DMT1 internalization.

scholarly journals The role of transferrin in the mechanism of cellular iron uptake

1990 ◽  
Vol 271 (1) ◽  
pp. 1-9 ◽  
Author(s):  
K Thorstensen ◽  
I Romslo
Keyword(s):  
Iron Uptake ◽  
Cellular Iron ◽  
Cellular Iron Uptake
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