scholarly journals Iron modulation of erythropoiesis is associated with Scribble-mediated control of the erythropoietin receptor

2017 ◽  
Vol 215 (2) ◽  
pp. 661-679 ◽  
Author(s):  
Shadi Khalil ◽  
Lorrie Delehanty ◽  
Stephen Grado ◽  
Maja Holy ◽  
Zollie White ◽  
...  
Keyword(s):  
Surface Display ◽  
Intravenous Iron ◽  
Surface Expression ◽  
Nutrient Sensing ◽  
Erythropoietin Receptor ◽  
Control Element ◽  
Erythroid Progenitors ◽  
Iron Restriction ◽  
Epo Receptor ◽  
Proliferation And Differentiation

Iron-restricted human anemias are associated with the acquisition of marrow resistance to the hematopoietic cytokine erythropoietin (Epo). Regulation of Epo responsiveness by iron availability serves as the basis for intravenous iron therapy in anemias of chronic disease. Epo engagement of its receptor normally promotes survival, proliferation, and differentiation of erythroid progenitors. However, Epo resistance caused by iron restriction selectively impairs proliferation and differentiation while preserving viability. Our results reveal that iron restriction limits surface display of Epo receptor in primary progenitors and that mice with enforced surface retention of the receptor fail to develop anemia with iron deprivation. A mechanistic pathway is identified in which erythroid iron restriction down-regulates a receptor control element, Scribble, through the mediation of the iron-sensing transferrin receptor 2. Scribble deficiency reduces surface expression of Epo receptor but selectively retains survival signaling via Akt. This mechanism integrates nutrient sensing with receptor function to permit modulation of progenitor expansion without compromising survival.

Regulation of the Erythroid Iron Deprivation Response By a TfR2-Scribble-Epor Integrated Module Coupling Iron Sensing with Receptor Presentation

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 3615-3615
Author(s):  
Shadi Khalil ◽  
Lorrie L Delehanty ◽  
Maja Holy ◽  
Stephen Grado ◽  
Grant C. Bullock ◽  
...  
Keyword(s):  
Iron Deficiency ◽  
Conflicts Of Interest ◽  
Nutrient Sensing ◽  
Erythropoietin Receptor ◽  
Erythroid Progenitors ◽  
Intracellular Iron ◽  
Iron Deprivation ◽  
Downstream Effector ◽  
Proliferation And Differentiation ◽  
Cathepsin Protease

Abstract Iron deficiency in humans causes desensitization of erythroid progenitors to erythropoietin, the principal cytokine for erythroid survival, proliferation, and differentiation. This nutrient deprivation response acts in a lineage-selective, non-apoptotic manner to restrain expansion of the tissue responsible for the majority of iron consumption, thereby triaging iron utilization under conditions of deficiency. The molecular basis for this response is incompletely understood but involves transferrin receptor 2 (TfR2) and aconitase enzymatic activity as extra- and intracellular iron sensors. Here, we identify a multi-component, integrated module connecting these two elements of erythroid iron sensing with endo-lysosomal trafficking, receptor surface delivery, and configuration of EpoR signaling. Specifically, iron and aconitase activity modulate the rate of TfR2 catabolism by cathepsin protease activity. Scribble, a conserved regulator of receptor transport and signaling, binds TfR2 and serves as a downstream effector through to its co-catabolism. Scribble levels in turn influence surface delivery of the erythropoietin receptor (EpoR), which physically interacts with both Scribble and TfR2. The TfR2-dependent downregulation of Scribble associated with iron deprivation diminishes surface EpoR density and skews its signaling from JAK-STAT to Akt pathways. Mice with surface-trapped, endocytosis-defective EpoR fail to develop anemia in response to iron deficiency. These findings establish a tissue-specific nutrient sensing pathway relevant to the pathogenesis of human anemias and their resistance to erythropoietin therapy. Disclosures No relevant conflicts of interest to declare.

scholarly journals The Glucocorticoid Receptor Cooperates With the Erythropoietin Receptor and c-Kit to Enhance and Sustain Proliferation of Erythroid Progenitors In Vitro

Blood ◽  
1999 ◽  
Vol 94 (2) ◽  
pp. 550-559 ◽  
Author(s):  
Marieke von Lindern ◽  
Wolfgang Zauner ◽  
Georg Mellitzer ◽  
Peter Steinlein ◽  
Gerhard Fritsch ◽  
...  
Keyword(s):  
Erythropoietin Receptor ◽  
Erythroid Cells ◽  
Erythroid Progenitors ◽  
Liquid Cultures ◽  
Expression Of Genes ◽  
Proliferation And Differentiation ◽  
In Vitro Expansion ◽  
Blast Cells ◽  
Colony Forming Capacity

Abstract Although erythropoietin (Epo) is essential for the production of mature red blood cells, the cooperation with other factors is required for a proper balance between progenitor proliferation and differentiation. In avian erythroid progenitors, steroid hormones cooperate with tyrosine kinase receptors to induce renewal of erythroid progenitors. We examined the role of corticosteroids in the in vitro expansion of primary human erythroid cells in liquid cultures and colony assays. Dexamethasone (Dex), a synthetic glucocorticoid hormone, cooperated with Epo and stem cell factor to induce erythroid progenitors to undergo 15 to 22 cell divisions, corresponding to a 105- to 106-fold amplification of erythroid cells. Dex acted directly on erythroid progenitors and maintained the colony-forming capacity of the progenitor cells expanded in liquid cultures. The hormone delayed terminal differentiation into erythrocytes, which was assayed by morphology, hemoglobin accumulation, and the expression of genes characteristic for immature cells. Sustained proliferation of erythroid progenitors could be induced equally well from purified erythroid burst-forming units (BFU-E), from CD34+ blast cells, and from bone marrow depleted from CD34+ cells.

scholarly journals The Glucocorticoid Receptor Cooperates With the Erythropoietin Receptor and c-Kit to Enhance and Sustain Proliferation of Erythroid Progenitors In Vitro

Blood ◽  
1999 ◽  
Vol 94 (2) ◽  
pp. 550-559 ◽  
Author(s):  
Marieke von Lindern ◽  
Wolfgang Zauner ◽  
Georg Mellitzer ◽  
Peter Steinlein ◽  
Gerhard Fritsch ◽  
...  
Keyword(s):  
Erythropoietin Receptor ◽  
Erythroid Cells ◽  
Erythroid Progenitors ◽  
Liquid Cultures ◽  
Expression Of Genes ◽  
Proliferation And Differentiation ◽  
In Vitro Expansion ◽  
Blast Cells ◽  
Colony Forming Capacity

Although erythropoietin (Epo) is essential for the production of mature red blood cells, the cooperation with other factors is required for a proper balance between progenitor proliferation and differentiation. In avian erythroid progenitors, steroid hormones cooperate with tyrosine kinase receptors to induce renewal of erythroid progenitors. We examined the role of corticosteroids in the in vitro expansion of primary human erythroid cells in liquid cultures and colony assays. Dexamethasone (Dex), a synthetic glucocorticoid hormone, cooperated with Epo and stem cell factor to induce erythroid progenitors to undergo 15 to 22 cell divisions, corresponding to a 105- to 106-fold amplification of erythroid cells. Dex acted directly on erythroid progenitors and maintained the colony-forming capacity of the progenitor cells expanded in liquid cultures. The hormone delayed terminal differentiation into erythrocytes, which was assayed by morphology, hemoglobin accumulation, and the expression of genes characteristic for immature cells. Sustained proliferation of erythroid progenitors could be induced equally well from purified erythroid burst-forming units (BFU-E), from CD34+ blast cells, and from bone marrow depleted from CD34+ cells.

scholarly journals Mammalian Granulocyte–Macrophage Colony-stimulating Factor Receptor Expressed in Primary Avian Hematopoietic Progenitors: Lineage-specific Regulation of Proliferation and Differentiation

1998 ◽  
Vol 141 (4) ◽  
pp. 1041-1051
Author(s):  
Oliver Wessely ◽  
Eva-Maria Deiner ◽  
Kim Chew Lim ◽  
Georg Mellitzer ◽  
Peter Steinlein ◽  
...  
Keyword(s):  
Erythropoietin Receptor ◽  
Colony Stimulating Factor ◽  
Erythroid Progenitors ◽  
Erythroid Progenitor ◽  
Gm Csf ◽  
Proliferation And Differentiation ◽  
Macrophage Colony Stimulating Factor ◽  
Α Chain ◽  
Macrophage Colony ◽  
Stimulating Factor

The cytokine Granulocyte–Macrophage Colony-Stimulating Factor (GM-CSF) regulates proliferation, differentiation, and apoptosis during myelopoiesis and erythropoiesis. Structure–function relationships of GM-CSF interactions with its receptor (GM-R), the biochemistry of GM-R signal transduction, and GM-CSF action in vivo are relatively well understood. Much less is known, however, about GM-R function in primary hematopoietic cells. In this paper we show that expression of the human GM-R in a heterologous cell system (primary avian erythroid and myeloid cells) confirms respective results in murine or human cell lines, but also provides new insights how the GM-R regulates progenitor proliferation and differentiation. As expected, the hGM-CSF stimulated myeloid progenitor proliferation and differentiation and enhanced erythroid progenitor proliferation during terminal differentiation. In the latter cells, however, the hGM-R only partially substituted for the activities of the erythropoietin receptor (EpoR). It failed to replace the EpoR in its cooperation with c-Kit to induce long-term proliferation of erythroid progenitors. Furthermore, the hGM-R α chain specifically interfered with EpoR signaling, an activity neither seen for the βc subunit of the receptor complex alone, nor for the α chain of the closely related Interleukin-3 receptor. These results point to a novel role of the GM-R α chain in defining cell type–specific functions of the GM-R.

Both proteasomes and lysosomes degrade the activated erythropoietin receptor

Blood ◽  
2005 ◽  
Vol 105 (2) ◽  
pp. 600-608 ◽  
Author(s):  
Pierre Walrafen ◽  
Frédérique Verdier ◽  
Zahra Kadri ◽  
Stany Chrétien ◽  
Catherine Lacombe ◽  
...  
Keyword(s):  
Cell Surface ◽  
Intracellular Signaling ◽  
Erythropoietin Receptor ◽  
Janus Kinase ◽  
Receptor Internalization ◽  
Down Regulation ◽  
Epo Receptor ◽  
Receptor Complexes ◽  
Regulation Mechanisms ◽  
Rapid Activation

AbstractActivation of the erythropoietin receptor (EpoR) after Epo binding is very transient because of the rapid activation of strong down-regulation mechanisms that quickly decrease Epo sensitivity of the cells. Among these down-regulation mechanisms, receptor internalization and degradation are probably the most efficient. Here, we show that the Epo receptor was rapidly ubiquitinated after ligand stimulation and that the C-terminal part of the Epo receptor was degraded by the proteasomes. Both ubiquitination and receptor degradation by the proteasomes occurred at the cell surface and required Janus kinase 2 (Jak2) activation. Moreover, Epo-EpoR complexes were rapidly internalized and targeted to the lysosomes for degradation. Neither Jak2 nor proteasome activities were required for internalization. In contrast, Jak2 activation was necessary for lysosome targeting of the Epo-EpoR complexes. Blocking Jak2 with the tyrphostin AG490 led to some recycling of internalized Epo-Epo receptor complexes to the cell surface. Thus, activated Epo receptors appear to be quickly degraded after ubiquitination by 2 proteolytic systems that proceed successively: the proteasomes remove part of the intracellular domain at the cell surface, and the lysosomes degrade the remaining part of the receptor-hormone complex. The efficiency of these processes probably explains the short duration of intracellular signaling activated by Epo.

scholarly journals Identification of a novel pathway important for proliferation and differentiation of primary erythroid progenitors

1997 ◽  
Vol 94 (7) ◽  
pp. 3016-3021 ◽  
Author(s):  
U. Klingmuller ◽  
H. Wu ◽  
J. G. Hsiao ◽  
A. Toker ◽  
B. C. Duckworth ◽  
...  
Keyword(s):  
Erythroid Progenitors ◽  
Proliferation And Differentiation

scholarly journals Missense mutation of the erythropoietin receptor is a rare event in human erythroid malignancies

Blood ◽  
1996 ◽  
Vol 87 (4) ◽  
pp. 1502-1511 ◽  
Author(s):  
JP Le Couedic ◽  
MT Mitjavila ◽  
JL Villeval ◽  
F Feger ◽  
S Gobert ◽  
...  
Keyword(s):  
Missense Mutation ◽  
Rare Event ◽  
Unknown Origin ◽  
Erythropoietin Receptor ◽  
R Gene ◽  
Erythroid Progenitors ◽  
Consensus Binding Site ◽  
Abnormal Growth ◽  
Barr Virus ◽  
Epstein Barr

Human erythroid malignancies (polycythemia vera [PV] and erythroleukemia) are associated with erythropoietin (Epo)-independent growth and differentiation. Missense or nonsense mutations in the Epo receptor (Epo-R) have been recently described in experimental erythroleukemia in mice and in cases of erythrocytosis in humans. To search for a similar genetic alteration in erythroleukemia and PV, we entirely sequenced the exons of the Epo-R gene as well as the intron- exon junctions in these disorders using polymerase chain reaction. In 1 of 10 cases of erythroleukemia, a single allele mutation was found in the 8th Epo-R gene exon that changed asparagine 487 into a serine. No Epo-r gene mutation was found in 12 PV cases studied, but the same mutation (N487S) was found in 1 patient with polycythemia that did not fulfill the criteria of PV (polycythemia of unknown origin). We did not detect this mutation after sequencing part of the 8th exon of the Epo-R gene from 21 other patients with polycythemia of unknown origin and 51 normal controls. The Epo-R mutation was also found in Epstein-Barr virus-derived cell lines from both cases, suggesting that it is not related to the malignant clone. Therefore, this mutation does not appear to be somatic, although no familial cases were found. The biologic effect of this mutation was subsequently studied. Erythroid progenitors from the polycythemic patient normally responded to Epo, whereas those from the erythroleukemic patient were Epo-independent due to autocrine stimulation by Epo. The normal and the mutated Epo-R were transfected into the murine Ba/F3 cell line. Both types of cells displayed the same response to Epo for proliferation, differentiation, and inhibition of apoptosis. Although this mutation may destroy a consensus binding site for Grb2, no obvious differences either in the pattern of Epo-induced tyrosine phosphorylated proteins or in the binding of Grb2 to the Epo-R were observed. In conclusion, a somatic Epo-R missense mutation does not appear to be a molecular mechanism involved in the abnormal growth of human erythroleukemia and PV. However, the Epo-R mutation (N487S) that we describe is located in the same tyrosine sequence beginning at AA 485 as the one previously observed (P488S) in as case of polycythemia (Sokol et al, Exp Hematol 22:447, 1994). These results suggest that this phosphopeptide sequence may play an important role in Epo signalling.

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