Erythropoietin gene expression pathway (EPO pathway)

The Erythropoietin (EPO) gene expression pathway is the primary physiological mechanism for regulating red blood cell production in response to oxygen levels [1.1.1, 1.3.1]. At the heart of this pathway is the oxygen-sensing system involving Hypoxia-Inducible Factors (HIFs) and Prolyl Hydroxylase Domain (PHD) enzymes [1.4.2]. Under normal oxygen conditions, PHD enzymes hydroxylate HIF-α subunits, marking them for proteasomal degradation [1.1.1]. In contrast, hypoxia or pharmacological inhibition of PHDs stabilizes HIF-α (particularly HIF-2α), allowing it to translocate to the nucleus and bind to Hypoxia Response Elements (HREs) within the EPO gene promoter and 3' enhancer regions [1.3.1, 1.5.1]. This binding triggers the transcription of EPO mRNA, leading to the production of the EPO hormone, which then stimulates erythropoiesis in the bone marrow [1.3.4]. This pathway is a major therapeutic target for treating anemia associated with chronic kidney disease, where drugs known as HIF-PH inhibitors are used to boost endogenous EPO production [1.4.3]. However, because the pathway also regulates other genes involved in angiogenesis and iron metabolism, its systemic activation carries risks such as thrombosis and potential tumor growth [1.3.2, 1.4.4].

Other names

HIF-EPO signaling axisHypoxia-inducible factor pathwayEPO promoter-enhancer complexOxygen-sensing pathway

Inhibition of prolyl hydroxylase domain (PHD) enzymes stabilizes hypoxia-inducible factor (HIF) subunits, which then bind to hypoxia response elements (HRE) in the EPO promoter and enhancer to induce endogenous erythropoietin transcription [1.4.2, 1.4.3].