Erythroid 5-aminolevulinate synthase, ferrochelatase and DMT1 expression in erythroid progenitors: differential pathways for erythropoietin and iron-dependent regulation.
To determine whether erythropoietin (EPO) affects haem biosynthesis and iron transport, we studied the effects of EPO on the expression of erythroid 5-aminolevulinate synthase (eALAS), ferrochelatase and divalent metal transporter 1 (DMT-1) in human erythroid progenitor cells, and in the murine and human erythroid cell lines MEL and K562. Cytoplasmic e-ALAS mRNA levels were significantly increased after incubation of cells with EPO for at least 24 h, which could be the result of a transcriptional mechanism. In contrast, ferrochelatase or DMT-1 mRNA expression were not affected. Moreover, EPO also increased e-ALAS enzyme activity after only 4 h of stimulation, when mRNA levels were unchanged. The underlying mechanism was an effect of EPO on e-ALAS mRNA translation, which was under the control of iron regulatory proteins (IRP) 1 and 2. Thereby, EPO weakened the binding affinity of IRP-2 to the iron responsive element (IRE) within e-ALAS mRNA which resulted in the increased expression of e-ALAS IRE-controlled reporter gene constructs, following EPO stimulation. Our results show that EPO directly affected haem biosynthesis by stimulating the transcriptional and post-transcriptional expression of the key enzyme e-ALAS. These data provide new insights into the complex biochemical interaction between iron metabolism, haem biosynthesis and EPO biology.
Department of Medicine, University Hospital Innsbruck, Anichstrasse 25, A-6020 Innsbruck, Austria.
Heinz
H
Zoller
Clemens
C
Decristoforo
Günter
G
Weiss
D000624:5-Aminolevulinate Synthetase / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D027682:Cation Transport Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D015672:Erythroid Precursor Cells / Q000201:enzymology / Q000378:metabolism*; D004921:Erythropoietin / Q000494:pharmacology*; D005294:Ferrochelatase / Q000378:metabolism*; D017930:Genes, Reporter; D006418:Heme / Q000096:biosynthesis*; D006801:Humans; D007501:Iron / Q000378:metabolism*; D033862:Iron-Binding Proteins; D051379:Mice; D012333:RNA, Messenger / Q000378:metabolism; D014158:Transcription, Genetic; D000099236:Solute Carrier Family 11, Member 2
D000624:5-Aminolevulinate Synthetase; D027682:Cation Transport Proteins; D004921:Erythropoietin; D005294:Ferrochelatase; D006418:Heme; D007501:Iron; D033862:Iron-Binding Proteins; D012333:RNA, Messenger; D000099236:Solute Carrier Family 11, Member 2