tailieunhanh - Báo cáo Y học: A new high affinity binding site for suppressor of cytokine signaling-3 on the erythropoietin receptor

Erythropoietin (Epo) is a hematopoietic cytokine that is crucial for the differentiation and proliferation of erythroid progenitor cells. Epo acts on its target cells by inducing homodimerization of the erythropoietin receptor (EpoR), thereby triggering intracellular signaling cascades. The EpoR encompasses eight tyrosine motifs on its cytoplasmic tail that have been shown to recruit a number of regulatory proteins. | Eur. J. Biochem. 269 2516-2526 2002 FEBS 2002 doi A new high affinity binding site for suppressor of cytokine signaling-3 on the erythropoietin receptor Michael Hortner1 2 Ulrich Nielsch1 Lorenz M. Mayr3 Peter C. Heinrich2 and Serge Haan2 1 Bayer Pharma Research Center Wuppertal Germany 2Institut fur Biochemie Rheinisch-Westfalische Technische Hochschule Aachen Germany 3Novartis Pharma Basel Switzerland Erythropoietin Epo is a hematopoietic cytokine that is crucial for the differentiation and proliferation of erythroid progenitor cells. Epo acts on its target cells by inducing homodimerization of the erythropoietin receptor EpoR thereby triggering intracellular signaling cascades. The EpoR encompasses eight tyrosine motifs on its cytoplasmic tail that have been shown to recruit a number of regulatory proteins. Recently the feedback inhibitor suppressor of cytokine signaling-3 SOCS-3 also referred to as cytokineinducible SH2-containing protein 3 CIS-3 has been shown to act on Epo signaling by both binding to the EpoR and the EpoR-associated Janus kinase 2 Jak2 Sasaki A. Yasukawa H. Shouda T. Kitamura T. Dikic I. Yoshimura A. 2000 J. Biol. Chem 275 29338-29347 . In this study tyrosine 401 was identified as a binding site for SOCS-3 on the EpoR. Here we show that human SOCS-3 binds to pY401 with a Kj of M while another EpoR tyrosine motif pY429pY431 can also interact with SOCS-3 but with a ninefold higher affinity than we found for the previously reported motif pY401. In addition SOCS-3 binds the double phosphorylated motif pY429pY431 more potently than the respective singly phosphorylated tyrosines indicating a synergistic effect of these two tyrosine residues with respect to SOCS-3 binding. Surface plasmon resonance analysis together with peptide precipitation assays and model structures of the SH2 domain of SOCS-3 complexed with EpoR peptides provide evidence for pY429pY431 being a new high affinity binding site for SOCS-3 on .