Erythroid cells

K6. Kanno, H., Fujii, H., and Miwa, S., Structural analysis of human pyruvate kinase L-gene and identification of the promoter activity in erythroid cells. Biochem. Biophys. Res. Commun. 188, 516-523 (1992). 

Erythropoietin is a glycoprotein hormone that regulates the proliferation, differentiation, and maturation of erythroid cells. The EPO receptor is a member of the class 1 cytokine receptor superfamily. The crystal structure of an EPO-mimetic peptide and the extracellular portion of the... 

Yet another potential pathway for NTBI uptake by intestinal and erythroid cells has been proposed involving integrins and mobilferrin (Conrad and Umbreit, 1993 Conrad et ah, 1994), although its physiological relevence remains uncertain. 

IX is accompanied by its transport back into the mitochondria whence it came, to undergo oxidation of its methylene groups to protoporphyrin IX and insertion of iron to yield the end product, haem. The two major sites of haem biosynthesis are erythroid cells, which synthesize around 85 % of the body s haem groups, and the liver, which synthesizes most of the remainder. A major function of haem in liver is as the prosthetic group of cytochrome P450, the importance of which in detoxification has been discussed in Chapter 2. The liver cell must synthesize cytochrome P450 throughout its lifetime in quantities that vary with conditions. In contrast, the... 

The regulatory network of IRPs appears also to connect the synthesis of protoporphyrin IX in erythroid cells, and of certain mitochondrial iron-sulfur proteins to iron bioavailability (reviewed in Hentze and Kuhn, 1996). mRNAs encoding erythroid... 

Stimulation of murine peritoneal macrophages with IFNy and LPS induced NO synthesis and activated IRE binding by IRP-1 and IRP-2. This activation is NO dependent and accompanied by a loss of the aconitase activity of IRP-1. This was also shown to occur in other cell types, such as the erythroid cell line K562, rat brain slices and mouse fibroblast lines and did not require cytokine stimulation. The activating effects of NO may depend on a direct interaction with the 4Fe-4S cluster or a slow effect on the low-molecular-weight iron pool. Activation of IRP-2 by LPS and IFN-y has not been universally confirmed (reviewed by Cairo and Pietrangelo, 2000). 

Sawyer, S.T., Krantz, S.B., and Luna, J. (1987) Identification of the receptor for erythropoietin by cross-linking to Friend virus-infected erythroid cells. Proc. Natl. Acad. Sci. USA 84, 3690-3694. 

Main target cells Neutrophils. Also other haemopoietic progenitors and endothelial cells Macrophages and their precursor cells Haematopoietic progenitor cells Granulocytes Monocytes Endothelial cells Megakaryocytes T-lymphocytes Erythroid cells... 

Methylation of histone lysines has been seen only in H3 and H4 at position 9, 27 for H3 and at position 20 of H4. Sometimes a lysine may have more than one methyl group (Ogawa et al., 1969 Patthy et al., 1973 DeLange et al., 1969, 1973). Methylation of histidines was reported for HI and H5 in duck erythroid cells. This modification, which occurs late in S phase or in G, is found in the amino-terminal region of H3 and H4 and is irreversible (for references, see Allfrey, 1977 Dixon, 1976). 

Chung JH, Whiteley M, Felsenfeld G (1993) A 5 element of the chicken beta-globin domain serves as an insulator in human erythroid cells and protects against position effect in Drosophila. Cell 74(3) 505-514... 

Tonks, A., Pearn, L., Tonks, A., Pearce, L., Hoy, T., Phillips, S., Fisher, J., Downing, J., Burnett, A. and Darley, R. (2003) The AMLl-ETO fusion gene promotes extensive self-renewal of human primary erythroid cells. Blood 101, 624-632. 

Erythropoetin EPO kidney erythroid cells (erythrocyte precursors) ... 

Figure 17.9 Rat in vivo hematotoxicity evaluated using flow cytometry (based on Saad et al. [59]). Gating strategy of flow cytometry evaluated rat bone marrow samples. N = at least 10000 cells. Results include absolute number nucleated cells, myeloid cells, nucleated erythroid cells and lymphoid cells.

Figure 17.10 Flow cytometric method does not differentiate between nucleated erythroid cells and reticulocytes, on some instruments. Non-nucleated e throid cells were isolated using cellulose fractionation. Part of the sample was stained with Wright-Giemsa and reticulocytes and mature nucleated cells quantified by trained medical technologists.

Regulation of heme synthesis in erythroid cells occurs at enzymes catalyzing... 

The regulation of hematopoiesis in the bone marrow is not only controlled by the cytokine composition, the cells microenvironment and the oxygen tension, but, as shown recently [55], also by the local pH. For cells of different Hneages deviating pH optima have been described. While CFU-GM proliferate best in a pH range 7.2 - 7.4 (the normal pH of blood), for erythroid cells an optimum of pH 7.6 was found. Below an acidic pH of 6.7 no differentiation or proUferation of any hematopoietic cell was observed. Cells of the erythroid lineage are even strongly inhibited at a pH below 7.1 [56]. 

A well studied example for control at the level of eIF-2 is the regulation of protein biosynthesis in erythroid cells (review Chen and London, 1995). A decrease in the heme concentration in reticulocytes leads to inhibition of globin synthesis at the level... 

Increased erythropoiesis is associated with an increase in the number of transferrin receptors on developing erythroid cells. Iron store depletion and iron deficiency anemia are associated with an increased concentration of serum transferrin. 

---