Negative regulation of Jak2 by its auto-phosphorylation at tyrosine 913 via the Epo signaling pathway

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Time-resolved Förster Resonance Energy Transfer Assays for Measurement of Endogenous Phosphorylated STAT Proteins in Human Cells
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Time-resolved Förster Resonance Energy Transfer Assays for Measurement of Endogenous Phosphorylated STAT Proteins in Human Cells

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Megumi Funakoshi-Tago1, Kenji Tago, Tadashi Kasahara

  • 1Department of Biochemistry, Faculty of Pharmacy, Keio University, 1-5-30 Shibakoen, Minato-ku, Tokyo 105-8512, Japan.

Cellular Signalling
|August 7, 2008
PubMed

Insights

A novel phosphorylation site, tyrosine 913, negatively regulates Janus kinase 2 (Jak2) signaling. This discovery impacts understanding of erythropoietin (Epo) pathways and erythrocyte differentiation.

Area of Science:

  • Cellular signaling pathways
  • Molecular biology
  • Hematopoiesis

Background:

  • Janus kinase 2 (Jak2) is crucial for erythropoietin (Epo) signaling, impacting erythrocyte differentiation and Stat5 activation.
  • Identifying regulatory phosphorylation sites in Jak2 is key to understanding its function.

Purpose of the Study:

  • To identify novel functional phosphorylation sites in Janus kinase 2 (Jak2).
  • To investigate the regulatory role of tyrosine 913 (Y(913)) phosphorylation in Jak2 activity and Epo signaling.

Main Methods:

  • Screening for critical tyrosine phosphorylation residues in Jak2.
  • Site-directed mutagenesis to create Y(913)F (phosphorylation-defective) and Y(913)E (phosphorylation-mimicking) mutants.
  • Epo stimulation assays in Jak2-deficient fetal liver cells.

Main Results:

  • Tyrosine 913 (Y(913)) was identified as a novel, functional phosphorylation site that negatively regulates Jak2.
  • Y(913)F mutation enhanced Epo-induced Jak2 activation, while Y(913)E mutation abrogated it.
  • Jak2-deficient cells expressing Y(913)F showed robust erythroid colony formation, unlike those with Y(913)E.

Conclusions:

  • Tyrosine 913 phosphorylation negatively controls Jak2 activity and is essential for normal erythropoiesis.
  • This Y(913) phosphorylation mechanism may represent a common negative regulation strategy for the Janus kinase (Jak) family, including Jak1.

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