Protein tyrosine phosphatase 1B (PTP1B) is involved in the defective erythropoietic function of carbamylated erythropoietin

• Epo induced prolonged phosphorylation of proliferation signals in UT-7 cells.
• cEpo induced only transient phosphorylation of proliferative pathways.
• PTP1B activity was significantly increased in cultures with cEpo.
• PTP1B colocalized with both subunits of the heterodimeric receptor used by cEpo.
• Phosphatases are involved in the inability of cEpo to act as an erythroid growth factor.