[Function, molecular structure and gene expression regulation of erythropoietin]

Erythropoietin (EPO) is a glycoprotein hormone which enhances red blood cell production by stimulating growth and differentiation of erythroid progenitor cells. Recombinant human EPO (huEPO), expressed in CHO cells, is highly similar to urinary huEPO with respect to both structural and functional properties. EPO production is primarily localized to peritubular interstitial cells in the cortex of the kidney. Increased EPO production due to anemia seems to be correlated with increased numbers of EPO-producing cells rather than with increased production by the individual EPO-producing cells. A heme protein is proposed to be the oxygen sensor. Tissue-specific and hypoxia-inducible expression of EPO gene is governed by multiple regulatory elements. Murine CFU-E from the spleens of mice, infected with the anemia-inducing strain of Friend virus, differentiate into reticulocytes in response to EPO. EPO appears to prevent CFU-E from programmed death (apoptosis). The gene for mouse EPO receptor produces 65 Kd protein on the cell surface. This protein seems to be specifically associated with another 100 Kd and/or 85 Kd proteins. The gene for human EPO receptor was also cloned, based on its similarity to murine counterpart. EPO receptor belongs to a novel class of receptors termed the cytokine receptor superfamily.