Modulation of protein tyrosine phosphatase 1B by erythropoietin in UT-7 cell line. 2007

Mariana A Callero, and Gladys M Pérez, and Daniela C Vittori, and Nicolás Pregi, and Alcira B Nesse
Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina. mcallero@qb.fcen.uba.ar

OBJECTIVE Since the reversible phosphorylation of tyrosyl residues is a critical event in cellular signaling pathways activated by erythropoietin (Epo), attention has been focused on protein tyrosine phosphatases (PTPs) and their coordinated action with protein tyrosine kinases. The prototypic member of the PTP family is PTP1B, a widely expressed non-receptor PTP located both in cytosol and intracellular membranes via its hydrophobic C-terminal targeting sequence. PTP1B has been implicated in the regulation of signaling pathways involving tyrosine phosphorylation induced by growth factors, cytokines, and hormones, such as the downregulation of erythropoietin and insulin receptors. However, little is known about which factor modulates the activity of this enzyme. METHODS The effect of Epo on PTP1B expression was studied in the UT-7 Epo-dependent cell line. PTP1B expression was analyzed under different conditions by Real-Time PCR and Western blot, while PTP1B phosphatase activity was determined by a p-nitrophenylphosphate hydrolysis assay. RESULTS Epo rapidly induced an increased expression of PTP1B which was associated with higher PTP1B tyrosine phosphorylation and phosphatase activity. The action of Epo on PTP1B induction involved Janus Kinase 2 (JAK2) and Phosphatidylinositol-3 kinase (PI3K). CONCLUSIONS The results allow us to suggest for the first time that, besides modulating Epo/Epo receptor signaling, PTP1B undergoes feedback regulation by Epo.

UI MeSH Term Description Entries
D010766 Phosphorylation The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety. Phosphorylations
D002460 Cell Line Established cell cultures that have the potential to propagate indefinitely. Cell Lines,Line, Cell,Lines, Cell
D002470 Cell Survival The span of viability of a cell characterized by the capacity to perform certain functions such as metabolism, growth, reproduction, some form of responsiveness, and adaptability. Cell Viability,Cell Viabilities,Survival, Cell,Viabilities, Cell,Viability, Cell
D004921 Erythropoietin Glycoprotein hormone, secreted chiefly by the KIDNEY in the adult and the LIVER in the FETUS, that acts on erythroid stem cells of the BONE MARROW to stimulate proliferation and differentiation.
D000081082 Phosphoinositide-3 Kinase Inhibitors Agents that inhibit PHOSPHOINOSITIDE-3 KINASE activity. Phosphoinositide-3 Kinase Inhibitor,Inhibitor, Phosphoinositide-3 Kinase,Inhibitors, Phosphoinositide-3 Kinase,Kinase Inhibitor, Phosphoinositide-3,Kinase Inhibitors, Phosphoinositide-3,Phosphoinositide 3 Kinase Inhibitor,Phosphoinositide 3 Kinase Inhibitors
D015536 Down-Regulation A negative regulatory effect on physiological processes at the molecular, cellular, or systemic level. At the molecular level, the major regulatory sites include membrane receptors, genes (GENE EXPRESSION REGULATION), mRNAs (RNA, MESSENGER), and proteins. Receptor Down-Regulation,Down-Regulation (Physiology),Downregulation,Down Regulation,Down-Regulation, Receptor
D015971 Gene Expression Regulation, Enzymologic Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action in enzyme synthesis. Enzymologic Gene Expression Regulation,Regulation of Gene Expression, Enzymologic,Regulation, Gene Expression, Enzymologic
D017027 Protein Tyrosine Phosphatases An enzyme group that specifically dephosphorylates phosphotyrosyl residues in selected proteins. Together with PROTEIN-TYROSINE KINASE, it regulates tyrosine phosphorylation and dephosphorylation in cellular signal transduction and may play a role in cell growth control and carcinogenesis. Phosphotyrosine Phosphatase,Protein-Tyrosine-Phosphatase,Tyrosyl Phosphoprotein Phosphatase,PTPase,Phosphotyrosyl Protein Phosphatase,Protein-Tyrosine Phosphatase,Phosphatase, Phosphotyrosine,Phosphatase, Phosphotyrosyl Protein,Phosphatase, Protein-Tyrosine,Phosphatase, Tyrosyl Phosphoprotein,Phosphatases, Protein Tyrosine,Phosphoprotein Phosphatase, Tyrosyl,Protein Phosphatase, Phosphotyrosyl,Protein Tyrosine Phosphatase,Tyrosine Phosphatases, Protein
D053614 Janus Kinase 2 A Janus kinase subtype that is involved in signaling from GROWTH HORMONE RECEPTORS; PROLACTIN RECEPTORS; and a variety of CYTOKINE RECEPTORS such as ERYTHROPOIETIN RECEPTORS and INTERLEUKIN RECEPTORS. Dysregulation of Janus kinase 2 due to GENETIC TRANSLOCATIONS have been associated with a variety of MYELOPROLIFERATIVE DISORDERS. JAK-2 Protein Tyrosine Kinase,JAK2 Protein Tyrosine Kinase,JAK 2 Protein Tyrosine Kinase
D054562 Protein Tyrosine Phosphatase, Non-Receptor Type 1 A subtype of non-receptor protein tyrosine phosphatases that includes two distinctive targeting motifs; an N-terminal motif specific for the INSULIN RECEPTOR, and a C-terminal motif specific for the SH3 domain containing proteins. This subtype includes a hydrophobic domain which localizes it to the ENDOPLASMIC RETICULUM. PTPase 1B,PTPase HA2,Protein Tyrosine Phosphatase 1B,Protein-Tyrosine Phosphatase HA2,Protein Tyrosine Phosphatase HA2,Protein Tyrosine Phosphatase, Non Receptor Type 1

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