Erythropoiesis protein

Kochendoerfer GG, Chen SY, Mao F, Cressman S, Traviglia S, Shao H, et al. Design and chemical synthesis of a homogeneous polymer-modified erythropoiesis protein. Science 2003 299(5608) 884-887. 

The synthetic erythropoiesis protein (SEP), a permitted therapeutic agent, is an example for this technique. Two branched polymers with negative charged end... 

Aranesp Mircera" SEP (synthetic erythropoiesis protein) Amgen Roche Gryphon Therapeutics CHO X X... 

Human erythropoietin is a glycoprotein of 166 amino acids (molecular mass about 34 kDa). Its amount in plasma can be measured by radioimmunoassay. It is the major regulator of human erythropoiesis. Erythropoietin is synthesized mainly by the kidney and is released in response to hypoxia into the bloodstream, in which it travels to the bone marrow. There it interacts with progenitors of red blood cells via a specific receptor. The receptor is a transmembrane protein consisting of two different subunits and a number of domains. It is not a tyrosine kinase, but it stimulates the activities of specific... 

About a quarter of the total body iron is stored in macrophages and hepatocytes as a reserve, which can be readily mobilized for red blood cell formation (erythropoiesis). This storage iron is mostly in the form of ferritin, like bacterioferritin a 24-subunit protein in the form of a spherical protein shell enclosing a cavity within which up to 4500 atoms of iron can be stored, essentially as the mineral ferrihydrite. Despite the water insolubility of ferrihydrite, it is kept in a solution within the protein shell, such that one can easily prepare mammalian ferritin solutions that contain 1 M ferric iron (i.e. 56 mg/ml). Mammalian ferritins, unlike most bacterial and plant ferritins, have the particularity that they are heteropolymers, made up of two subunit types, H and L. Whereas H-subunits have a ferroxidase activity, catalysing the oxidation of two Fe2+ atoms to Fe3+, L-subunits appear to be involved in the nucleation of the mineral iron core once this has formed an initial critical mass, further iron oxidation and deposition in the biomineral takes place on the surface of the ferrihydrite crystallite itself (see a further discussion in Chapter 19). 

All tissues except mature red blood cells are able to manufacture haem for use in the respiratory cytochrome proteins of the electron transport chain. However, the liver is an especially important site of haem synthesis because it (a) is a major organ of erythropoiesis in utero and (b) haem-containing cytochrome-P450 (CYP-450) enzymes play significant roles in hepatic detoxification of drugs, toxins and endogenous waste products (Section 6.4). 

Description Aranesp is an erythropoiesis stimulating protein (EPO) produced using rDNA technology in CHO cells. It has 165 amino acids and the molecular weight is 30-37 kDa. 

Figure 18.3 Competition for iron between proliferating bacteria, erythropoiesis in the bone marrow and proliferating lymphocytes in the lymph nodes. The iron ion is required for synthesis of haemoglobin, cytochromes and iron-sulphur proteins, and for maintenance of the structure of DNA.

About 70% of the total body store of iron (-5 g) is contained within erythrocytes. When these are degraded by macrophages of the reticuloendothelial (mononuclear phagocyte) system, iron is liberated from hemoglobin. Fe can be stored as ferritin (= protein apoferri-tin + Fe ) or returned to erythropoiesis sites via transferrin. 

Goldknopf, I.L., Wilson, G., Ballal, N.R., and Busch, H. (1980). Chromatin conjugate protein A24 is cleaved and ubiquitin is lost during chicken erythropoiesis. J. Biol. Chem. 255,10555-10558. 

Partial or total deficiency, or inhibition of bilirubin UDP-glucuronyltransferase may cause unconjugated hyperbilirubinemia. Increased production (hemolysis, ineffective erythropoiesis) should be excluded by investigating hematologic parameters. Determination in vitro of bilirubin UDP-glycosyltransferase activities can contribute to a differential diagnosis. To minimize the effect of cytoplasmic carrier proteins, in in vitro... 

Pharmacology Darbepoetin alfa is an erythropoiesis-stimulating protein produced by recombinant DNA technology. Darbepoetin stimulates erythropoiesis by the same mechanism as endogenous erythropoietin. 

A number of clinical circumstances have been identified which are characterized by an often profoundly depressed rate of erythropoiesis (Table 6.7). Many, if not all, such conditions could be/are responsive to administration of exogenous EPO. The prevalence of anaemia, and the medical complications which ensue, prompts tremendous therapeutic interest in this haemopoietic growth factor. EPO has been approved for use to treat various forms of anaemia (Table 6.8). It was the first therapeutic protein produced by genetic engineering, whose annual sales value topped 1 billion. Its current annual sales value is now close to 2 billion. EPO used therapeutically is produced by recombinant means in CHO cells. 

Erythropoietin is a protein produced mainly in the cortex of the kidney. Erythropoietin binds to a receptor on the surface of erythroid precursor cells. It stimulates erythropoiesis and is primarily indicated for the treatment of anemia in patients with chronic renal failure. Other indications are the management of anemia in cancer patients and in HIV positive subjects treated with anti-HIV regimens. 

Studies indieate that the erythrocytosis is mediated by an inereased renal produetion of erythropoietin. Erythropoietin is a protein produced by the kidney, which enhances erythropoiesis by stimulating the formation of proerythrocytes and the release of retieulocytes from the bone marrow. Overall, the results indicate that niekel exposure results in hematological effects in both humans and... 

Abbreviations rhuEPO, recombinant human erythropoietin NESP, novel erythropoiesis stimulating protein derived from genetic modification of rhuEPO to create two additional N-linked gylcosylation sites. 

As well reviewed elsewhere [2], the control exerted by 5a-reduced steroids on erythropoiesis is best explained by transcriptional control of the erythropoietin gene. Certainly, such androgens are actively concentrated in the nuclear chromatin of bone marrow, both in vivo and in vitro. By contrast, the situation is entirely different with respect to 5/3-reduced steroids. In the embryonic and fetal organs of many animals, aetiocholanolone or 5/3-DHT regulate the appearance of a 5 cap-recognition protein, without which the translation of the mRNAs for haemoglobin E (embry-... 

Approximately 20 mg of iron is required daily for erythropoiesis. The iron requirements are supplied by recycled iron and from residual body iron stores. One major store is in hepato-cytes where 0.5-1 g of iron is bound to specialized proteins such as ferritin and hemosiderin. Ferritin is a large, 440-kd cellular storage protein for iron. Measurement of plasma ferritin is seen as a reflection of the cellular ferritin stores, which in turn reflects cellular iron stores. Body stores of iron are maintained by recycling Senescent erythrocytes are ingested by macrophages, and their iron is taken up by serum transferrin. The iron is delivered to... 

The biotechnology industry has evolved significantly since the introduction in 1982 of human insulin synthesized in Escherichia coli—the first Food and Drug Administration (FDA)-approved recombinant therapeutic agent in the United States. Since then, over 75 other recombinant proteins have been introduced. The list is comprised of cytokines, hormones, monoclonal antibodies, and vaccines. There are more than 1100 companies competing for this market, and the current sale of these products comprises approximately 10% of the sales of all therapeutic products sold in the United States. One such product, erythropoietin, an erythropoiesis-stimulating factor also known... 

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