Erythropoietin receptor (truncated form) (EPOR-T)

The truncated form of the erythropoietin receptor (EPOR) is a variant typically resulting from genetic mutations or alternative splicing that removes the C-terminal cytoplasmic domain. This domain is essential for the negative regulation of signaling, as it contains tyrosine residues that recruit phosphatases like SHP-1 to dephosphorylate and deactivate Janus kinase 2 (JAK2) (Source: UniProt P19235; PubMed: 8626781). In the absence of this regulatory region, the receptor exhibits hypersensitivity to erythropoietin (EPO), leading to sustained activation of the JAK2/STAT5 pathway and excessive production of red blood cells. This condition is clinically recognized as primary familial and congenital polycythemia (PFCP), an autosomal dominant disorder (Source: OMIM: 133170). While therapeutic erythropoiesis-stimulating agents (ESAs) like epoetin alfa are designed to target the full-length receptor, they also activate the truncated form, which can lead to dangerous levels of erythrocytosis in affected individuals. Consequently, the truncated EPOR is a critical subject of study in hematology for understanding EPO resistance, hypersensitivity, and the risks of thrombosis associated with elevated hematocrit levels. It also serves as a model for understanding how cytokine receptor signaling is terminated under normal physiological conditions.

Other names

Truncated erythropoietin receptortEPOREPOR-truncatedPFCP-associated erythropoietin receptor

Erythropoiesis-stimulating agents act as agonists that bind to the extracellular domain of the receptor, inducing homodimerization and activation of associated Janus kinase 2 (JAK2). This initiates downstream signaling through STAT5, PI3K/Akt, and MAPK pathways to promote erythroid progenitor survival and differentiation. In the truncated form, the lack of the C-terminal negative regulatory domain prevents signal termination, leading to hypersensitivity.