The signal transducer and activator of transcription factor 5 (Stat5) plays a very important role in functions of a broad spectrum of cytokines. Upon binding of cytokines to their receptors, Stat5 is tyrosine-phosphorylated (at Tyr694 of Stat5A) by activated Janus protein tyrosine kinases (Jaks), forms a dimer, translocates to the nucleus, and turns on a variety of cytokine-inducible genes. Although much is known about the process of Stat5 activation, little is known about the mechanism by which the tyrosine-phosphorylated Stat5 is inactivated. Our recent studies demonstrate that inactivation of the tyrosine-phosphorylated Stat5 is via dephosphorylation. Using peptides corresponding to the Stat5A tyrosine phosphorylation site, we identified the protein-tyrosine phosphatase, Shp-2, as a Stat5 phosphatase. Shp-2 specifically interacts with Stat5 under physiological conditions in a tyrosine-phosphorylation-dependent manner. Over-expression of Shp-2 attenuates cytokine-induced tyrosine phosphorylation of Stat5, whereas Shp-2 deficiency dramatically delays the dephosphorylation of Stat5. Shp-2 normally exists as an inactive form in cells, inhibited by binding of its own N-terminal SH2 domain to its catalytic domain. Our preliminary data show that the SH2 domains of Shp-2 do not directly interact with tyrosine-phosphorylated Stat5. Using the tyrosine-phosphorylated Stat5A peptides, we have co-purified the adapter protein, CrkL, with Shp-2. CrkL is able to associate with both Stat5 and Shp-2 in cells. Moreover, preliminary data show that over-expression of CrkL in cells accelerates the dephosphorylation of Star5. Based on these findings, we hypothesize that Shp-2 is a specific Stat5 phosphatase that is recruited to tyrosine-phosphorylated Stat5 and released from an inactive form to an active one by the adapter protein CrkL. Upon cytokine stimulation, activated Jaks phosphorylate Stat5 and the adapter protein CrkL. Tyrosine-phosphorylated Stat5 and CrkL form a complex, and subsequently, tyrosine-phosphorylated CrkL recruits Shp-2 to the complex through interaction of the sole phosphotyrosine of CrkL with SH2 domains of Shp-2, leading to activation of Shp2. Consequently, the activated Shp-2 accesses and dephosphorylates tyrosine-phosphorylated Stat5. To test our hypothesis, we will 1) identify the domains of Stat5 and Shp-2 that are required for Stat5 interaction with Shp-2, 2) determine the role of CrkL in Stat5 interaction with, and dephosphorylation by, Shp-2, and 3) study the physiological role of Stat5 dephosphorylation. The proposed research will contribute to understanding of the mechanism of Stat5 inactivation, provide more clues to the molecular pathogenesis of numerous diseases including hematological malignancies, and help identify targets for specific therapies.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL073284-04
Application #
7030252
Study Section
Hematology Subcommittee 2 (HEM)
Program Officer
Thomas, John
Project Start
2003-04-01
Project End
2008-03-31
Budget Start
2006-04-01
Budget End
2007-03-31
Support Year
4
Fiscal Year
2006
Total Cost
$270,135
Indirect Cost
Name
Bloodcenter of Wisconsin, Inc.
Department
Type
DUNS #
057163172
City
Milwaukee
State
WI
Country
United States
Zip Code
53233
Fu, Guoping; Yu, Mei; Chen, Yuhong et al. (2017) Phospholipase C?1 is required for pre-TCR signal transduction and pre-T cell development. Eur J Immunol 47:74-83
Chen, Yuhong; Yu, Mei; Dai, Xuezhi et al. (2011) Critical role for Gimap5 in the survival of mouse hematopoietic stem and progenitor cells. J Exp Med 208:923-35
Wuerzberger-Davis, Shelly M; Chen, Yuhong; Yang, David T et al. (2011) Nuclear export of the NF-?B inhibitor I?B? is required for proper B cell and secondary lymphoid tissue formation. Immunity 34:188-200
Fu, Guoping; Chen, Yuhong; Yu, Mei et al. (2010) Phospholipase C{gamma}1 is essential for T cell development, activation, and tolerance. J Exp Med 207:309-18
Schuman, James; Chen, Yuhong; Podd, Andrew et al. (2009) A critical role of TAK1 in B-cell receptor-mediated nuclear factor kappaB activation. Blood 113:4566-74
Ohmori, Keitaro; Luo, Yuchun; Jia, Yi et al. (2009) IL-3 induces basophil expansion in vivo by directing granulocyte-monocyte progenitors to differentiate into basophil lineage-restricted progenitors in the bone marrow and by increasing the number of basophil/mast cell progenitors in the spleen. J Immunol 182:2835-41
Schulteis, Ryan D; Chu, Haiyan; Dai, Xuezhi et al. (2008) Impaired survival of peripheral T cells, disrupted NK/NKT cell development, and liver failure in mice lacking Gimap5. Blood 112:4905-14
Chen, Yabing; Wang, Xiaohong; Di, Lie et al. (2008) Phospholipase Cgamma2 mediates RANKL-stimulated lymph node organogenesis and osteoclastogenesis. J Biol Chem 283:29593-601
Zeng, Hu; Chen, Yuhong; Yu, Mei et al. (2008) T cell receptor-mediated activation of CD4+CD44hi T cells bypasses Bcl10: an implication of differential NF-kappaB dependence of naive and memory T cells during T cell receptor-mediated responses. J Biol Chem 283:24392-9
Chen, Yuhong; Yu, Mei; Podd, Andrew et al. (2008) A critical role of Rap1b in B-cell trafficking and marginal zone B-cell development. Blood 111:4627-36

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