CIS3/SOCS-3 suppresses erythropoietin (EPO) signaling by binding the EPO receptor and JAK2

Atsuo Sasaki, Hideo Yasukawa, Takanori Shouda, Toshio Kitamura, Ivan Dikic, Akihiko Yoshimura

Research output: Contribution to journalArticle

249 Citations (Scopus)

Abstract

The cytokine-inducible SH2 protein-3 (CIS3/SOCS-3/SSI-3) has been shown to inhibit the JAK/STAT pathway and act as a negative regulator of fetal liver erythropoiesis. Here, we studied the molecular mechanisms by which CIS3 regulates the erythropoietin (EPO) receptor (EPOR) signaling in erythroid progenitors and Ba/F3 cells expressing the EPOR (BF-ER). CIS3 binds directly to the EPOR as well as JAK2 and inhibits EPO-dependent proliferation and STAT5 activation. We have identified the region containing Tyr401 in the cytoplasmic domain of the EPOR as a direct binding site for CIS3. Deletion of the Tyr401 region of the EPOR reduced the inhibitory effect of CIS3, suggesting that binding of CIS3 to the EPOR augmented the negative effect of CIS3. Both N- and C-terminal regions adjacent to the SH2 domain of CIS3 were necessary for binding to EPOR and JAK2. In the N-terminal region of CIS3, the amino acid Gly45 was critical for binding to the EPOR but not to JAK2, while Leu22 was critical for binding to JAK2. The mutation of G45A partially reduced ability of CIS3 to inhibit EPO-dependent proliferation and STAT5 activation, while L22D mutant CIS3 was completely unable to suppress EPOR signaling. Moreover, overexpression of STAT5, which also binds to Tyr401, reduced the binding of CIS3 to the EPOR, and the inhibitory effect of CIS3 against EPO signaling, while it did not affect JAB/SOCS-1/SSI-1. These data demonstrate that binding of CIS3 to the EPOR augments the inhibitory effect of CIS3. CIS3 binding to both EPOR and JAK2 may explain a specific regulatory role of CIS3 in erythropoiesis.

Original languageEnglish
Pages (from-to)29338-29347
Number of pages10
JournalJournal of Biological Chemistry
Volume275
Issue number38
DOIs
Publication statusPublished - 2000 Sep 22

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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