EPO

Fig1. Recently defined EPO/EPOR signal transduction circuits. (Alexander Weidemann, 2009)

What is EPO Protein?

EPO gene (erythropoietin) is a protein coding gene which situated on the long arm of chromosome 7 at locus 7q22. This gene encodes a secreted, glycosylated cytokine composed of four alpha helical bundles. The encoded protein is mainly synthesized in the kidney, secreted into the blood plasma, and binds to the erythropoietin receptor to promote red blood cell production, or erythropoiesis, in the bone marrow. Expression of this gene is upregulated under hypoxic conditions, in turn leading to increased erythropoiesis and enhanced oxygen-carrying capacity of the blood. Expression of this gene has also been observed in brain and in the eye, and elevated expression levels have been observed in diabetic retinopathy and ocular hypertension. The EPO protein is consisted of 193 amino acids and EPO molecular weight is approximately 21.3 kDa.

What is the Function of EPO Protein?

The main function of EPO is to promote the growth, proliferation, differentiation and maturation of erythroid progenitor cells in bone marrow, which is one of the most important factors in erythropoiesis. It acts by binding to receptors on the surface of bone marrow cells, especially in the process of red blood cell production plays a key stimulating role.EPO production is affected by a variety of factors, in particular, it is very sensitive to hypoxia. Under hypoxia conditions, the kidney will respond quickly and synthesize a large number of EPO, and then promote the transformation of erythroid progenitor cells into red blood cells through blood circulation to improve the body's ability to combine oxygen. In addition, the role of EPO is not limited to erythropoiesis, it is also expressed in different non-erythropoiesis tissues, can promote the survival of endothelial cells and neurons, has the effect of anti-oxidation and stability of red blood cell membrane.

EPO Related Signaling Pathway

In the JAK2/STAT5 pathway, EPO binds to EPOR and activates Janus kinase 2 (JAK2), which in turn activates signal transducers and transcriptional activators 5 (STAT5). EPO also activates the mitogen-activated protein kinase (MAPK) signaling pathway, which is involved in the regulation of cell proliferation, differentiation and survival. By activating phosphatidylinositol-3-kinase (PI3K) and protein kinase B (AKT), EPO promotes cell survival and metabolic activity. In addition, EPO exerts its anti-inflammatory and anti-apoptotic effects by blocking the p38 MAPK signaling pathway, which is particularly important in alleviating ischemia-reperfusion-induced acute lung injury. These mechanisms of action of EPO not only play a role in erythropoiesis, but also play an important role in non-hematopoietic tissues and tumor cells, showing the diversity and complexity of EPO functions.

Fig2. Recently defined EPO/EPOR signal transduction circuits. (David Kuhrt, 2015)

EPO Related Diseases

EPO is associated with a variety of diseases, especially anemia. It plays an important role in the treatment of anemia associated with chronic kidney disease, anemia caused by chemotherapy, and certain inherited anemia, such as thalassemia. In addition, abnormal levels of EPO have also been linked to the development of certain cancers, such as certain types of leukemia. EPO is also being studied for the treatment of certain neurodegenerative diseases, such as Alzheimer's disease, as well as heart disease because of its neuroprotective and cardioprotective properties. However, the misuse of EPO has also caused concern, especially in the field of sports, as it can improve athletes' endurance and performance.

Bioapplications of EPO

The applications of EPO are mainly concentrated in the medical field, especially for the treatment of anemia symptoms. Recombinant human erythropoietin (rHuEPO) is widely used as a drug in the treatment of chronic renal failure, chemotherapy-induced anemia, myelodysplastic syndrome, and some hereditary anemia diseases. In addition, EPO has been studied as a treatment for heart disease, stroke, certain neurodegenerative diseases, and as a potential means of improving athletic performance, although there are ethical and legal issues with the latter. Clinically, the use of EPO has helped improve patients' quality of life and increased oxygen carrying capacity by stimulating the production of red blood cells.

Case Study 1: Alexey P Kostikov, 2012

N-Succinimidyl 3-(di-tert-butyl[(18)F]fluorosilyl)benzoate ([(18)F]SiFB), a novel synthon for one-step labeling of proteins, was synthesized via a simple (18)F-(19)F isotopic exchange. A new labeling technique that circumvents the cleavage of the highly reactive active ester moiety under regular basic (18)F-labeling conditions was established. In order to synthesize high radioactivity amounts of [(18)F]SiFB, it was crucial to partially neutralize the potassium oxalate/hydroxide that was used to elute (18)F(-) from the QMA cartridge with oxalic acid to prevent decomposition of the active ester moiety. Purification of [(18)F]SiFB was performed by simple solid-phase extraction, which avoided time-consuming HPLC and yielded high specific activities of at least 525 Ci/mmol and radiochemical yields of 40-56%. [(18)F]SiFB was applied to the labeling of various proteins in likeness to the most commonly used labeling synthon in protein labeling, N-succinimidyl-4-[(18)F]fluorobenzoate ([(18)F]SFB). Rat serum albumin (RSA), apo-transferrin, a β-cell-specific single chain antibody, and erythropoietin were successfully labeled with [(18)F]SiFB in good radiochemical yields between 19% and 36%. This approach proved to be more successful and EPO was employed for labeling.

Fig1. Radioactive labeling of various proteins using [18F]SiFB ([18F]5) and the most commonly applied synthon in protein labeling via acylation, [18F]SFB.

Fig2. Time–activity curves for small bone, vessel, spleen, aorta, and liver extracted from in vivo PET scan for up to 60 min post injection of [18F]SiB-RSA.

Case Study 2: Janki Jayesh Patel, 2015

Bone morphogenetic protein-2 (BMP2) delivered from PCL produces bone when implanted subcutaneously, and erythropoietin (EPO) works synergistically with BMP2. In this study, EPO and BMP2 are adsorbed separately on two 3D-printed PCL scaffold modules that are assembled for codelivery on a single scaffold structure. This assembled modular PCL scaffold with dual BMP2 and EPO delivery was shown to increase bone growth in an ectopic location when compared with BMP2 delivery along a replicate scaffold structure. EPO (200 IU/mL) and BMP2 (65 μg/mL) were adsorbed onto the outer and inner portions of a modular scaffold, respectively. Protein binding and release studies were first quantified. Dual delivery produced more dense cellular marrow, while BMP2 had more fatty marrow. Dual EPO and BMP2 delivery is a potential method to regenerate bone faster for prefabricated flaps.

Fig3. Modular scaffold assembly.

Fig4. EPO cumulative release profile.

EPO has several biochemical functions, for example, erythropoietin receptor binding,hormone activity,protein binding. Some of the functions are cooperated with other proteins, some of the functions could acted by EPO itself. We selected most functions EPO had, and list some proteins which have the same functions with EPO. You can find most of the proteins on our site.

EPO has direct interactions with proteins and molecules. Those interactions were detected by several methods such as yeast two hybrid, co-IP, pull-down and so on. We selected proteins and molecules interacted with EPO here. Most of them are supplied by our site. Hope this information will be useful for your research of EPO.

EPOR;DOK2;EP300