Transferrin receptor expression is controlled differently by transferrin-bound and non-transferrin iron in human cells.
We studied the effects of iron supplied as transferrin-bound iron and iron supplied as non-transferrin iron on transferrin receptor expression by human cell lines. Defined conditions of iron supply were represented by (i) 5 microg/ml of iron-saturated transferrin (transferrin medium) and by (ii) 500 microM ferric citrate (ferric citrate medium). Transferrin receptor expression of studied cell lines (HeLa, K562, Jiyoye) grown as long-term cultures in transferrin medium was somewhat higher (up to 137% of the mean fluorescence intensity) than in ferric citrate medium. The receptor expression corresponded with cellular iron regulatory protein (IRP) activity (ratio activated/total), which was also higher in transferrin medium (0.69-0.84) than in ferric citrate medium (0.33-0.60). However, unexpectedly much higher (about 65-135-fold) cellular iron levels were found in ferric citrate medium (13.9-14.9 nmol/10(6) cells) than in transferrin medium (0.11-0.21 nmol/10(6) cells). In contrast to the iron levels, cellular ferritin levels of the cells in ferric citrate medium (38.3-130 ng/10(6) cells) were only about 2-7-fold higher than in transferrin medium (6.8-61.5 ng/10(6) cells). We suggest that iron supplied as non-transferrin iron (ferric citrate) is apparently less available for the control of transferrin receptor expression via IRP activity than iron supplied as transferrin.
Kriegerbecková
K
K
Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague.
Richardson
V
V
Döpper-Brunner
L
L
Chiba
P
P
Kühn
L C
LC
Goldenberg
H
H
Kovár
J
J
D002460:Cell Line; D005290:Ferric Compounds / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007501:Iron / Q000378:metabolism*; D035925:Iron-Regulatory Proteins; D007506:Iron-Sulfur Proteins / Q000378:metabolism; D020014:K562 Cells; D007700:Kinetics; D011485:Protein Binding; D016601:RNA-Binding Proteins / Q000378:metabolism; D011990:Receptors, Transferrin / Q000378:metabolism*; D014168:Transferrin / Q000378:metabolism*
D005290:Ferric Compounds; D035925:Iron-Regulatory Proteins; D007506:Iron-Sulfur Proteins; D016601:RNA-Binding Proteins; D011990:Receptors, Transferrin; D014168:Transferrin; C025314:ferric citrate; D007501:Iron