Erythropoietin (Epo) and thrombopoietin (Tpo) are the primary cytokines regulating red blood cell production, and megakaryocyte and platelet development, respectively. The adaptor protein Lnk negatively regulates signaling transduction of the Epo receptor (EpoR) and Tpo receptor (mpl), thereby downregulating Tpo-mediated megakaryocytopoiesis and Epo-mediated erythropoiesis. Lnk inhibits the activity of cytokine receptor integral partner, the JAK2 tyrosine kinase. Furthermore, the Lnk SH2 domain is essential for its inhibitory functions, and the functional interaction between Lnk and the receptor/JAK2 complex is phosphorylation-dependent. The purpose of this grant is to unravel the mechanism that encodes how Lnk controls the quantitative response to cytokines, and whose dysregulation predisposes to leukemia. To accomplish this, biochemical, cellular, and mouse genetic approaches will be used with the focus on the Lnk SH2 domain and tyrosine residues. Recombinant peptide library screens will establish Lnk SH2 domain binding motifs and mass spectrometry (MS) will identify Lnk SH2 domain interacting proteins in vivo. Novel primary hematopoietic cell culture systems will be developed to investigate the interactions among Lnk, cytokine receptors, and JAK2. Moreover, the Lnk tyrosines that are phosphorylated in vivo and important for its function will be dissected. Importantly, the mechanisms of Lnk regulatory function will be tested within physiological contexts using gene-deficient primary hematopoietic cells and generating gene-ablated mice. Unchecked and sustained cytokine receptor signaling leads to oncogenic transformation, therefore understanding the cellular mechanisms by which Lnk controls the amplitude and duration of receptor signaling will shed significant light on cytokine receptor regulation in general. Through this proposed research, the applicant will receive training in structural and proteomics biology and will gain the necessary skills and knowledge to become an independent investigator.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Scientist Development Award - Research & Training (K01)
Project #
5K01CA115679-06
Application #
7640868
Study Section
Subcommittee G - Education (NCI)
Program Officer
Lohrey, Nancy
Project Start
2005-07-01
Project End
2010-06-30
Budget Start
2009-07-01
Budget End
2010-06-30
Support Year
6
Fiscal Year
2009
Total Cost
$159,219
Indirect Cost
Name
Children's Hospital of Philadelphia
Department
Type
DUNS #
073757627
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
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Bersenev, Alexey; Wu, Chao; Balcerek, Joanna et al. (2010) Lnk constrains myeloproliferative diseases in mice. J Clin Invest 120:2058-69
Bersenev, Alexey; Wu, Chao; Balcerek, Joanna et al. (2008) Lnk controls mouse hematopoietic stem cell self-renewal and quiescence through direct interactions with JAK2. J Clin Invest 118:2832-44
Scott, Linda M; Tong, Wei; Levine, Ross L et al. (2007) JAK2 exon 12 mutations in polycythemia vera and idiopathic erythrocytosis. N Engl J Med 356:459-68
Tong, Wei; Ibarra, Yessenia M; Lodish, Harvey F (2007) Signals emanating from the membrane proximal region of the thrombopoietin receptor (mpl) support hematopoietic stem cell self-renewal. Exp Hematol 35:1447-55
Tong, Wei; Sulahian, Rita; Gross, Alec W et al. (2006) The membrane-proximal region of the thrombopoietin receptor confers its high surface expression by JAK2-dependent and -independent mechanisms. J Biol Chem 281:38930-40