Tyrosine kinase activity is a crucial component of cellular signaling cascades. Precise regulatory control over kinase activity must be maintained during signaling as evidenced by numerous human diseases that arise upon dysregulation of protein kinases. This project is aimed at generating a molecular level understanding of how tyrosine kinase activity is regulated during T cell signaling. The current renewal application continues to focus on the Tec family immunological tyrosine kinase Interleukin-2 tyrosine kinase, Itk. Our work over the last period has generated preliminary data that support mechanistic models for Itk regulation. Specifically, we have identified Itk dimerization as a switch for turning Itk catalytic activity 'off';we have discovered a specific docking interaction between Itk and its substrates that ensures fidelity in target phosphorylation;and we have data that suggest that the peptidyl prolyl isomerase, cyclophilin A, controls Itk activity by preventing substrate docking. Our studies on Itk and related Tec family members have also extended our understanding of substrate recognition for the well studied Src family of tyrosine kinases. The Src kinase, Lck, activates Itk following TCR engagement by phosphorylating a specific tyrosine in the Itk kinase domain and we have now identified that this reaction occurs via recognition of a remote substrate docking site.
The aims proposed in this application will pursue detailed structural studies of all of the protein regulatory complexes described. The molecular level knowledge that will emerge from this work will provide a better understanding of T cell signaling and the means to target specific interactions for therapeutic uses.

Public Health Relevance

This proposal aims to understand specific protein interaction leading to activation of tyrosine kinases in the immune response. The public health relevance of the project relates to developing new ways to either limit or enhance the immune response in the face of autoimmunity, immunosuppression or immunological diseases. Kinases in particular are prime therapeutic targets since they control much of immune cell signaling and genetic defects in specific kinases are linked to specific human diseases.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Special Emphasis Panel (ZRG1-IMM-H (02))
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Mallia, Conrad M
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Iowa State University
Schools of Arts and Sciences
United States
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Wang, Xinxin; Boyken, Scott E; Hu, Jiancheng et al. (2014) Calmodulin and PI(3,4,5)P? cooperatively bind to the Itk pleckstrin homology domain to promote efficient calcium signaling and IL-17A production. Sci Signal 7:ra74
Boyken, Scott E; Chopra, Nikita; Xie, Qian et al. (2014) A conserved isoleucine maintains the inactive state of Bruton's tyrosine kinase. J Mol Biol 426:3656-69
Joseph, Raji E; Kleino, Iivari; Wales, Thomas E et al. (2013) Activation loop dynamics determine the different catalytic efficiencies of B cell- and T cell-specific tec kinases. Sci Signal 6:ra76
Xie, Qian; Joseph, Raji E; Fulton, D Bruce et al. (2013) Substrate recognition of PLC?1 via a specific docking surface on Itk. J Mol Biol 425:683-96
Joseph, Raji E; Ginder, Nathaniel D; Hoy, Julie A et al. (2012) Structure of the interleukin-2 tyrosine kinase Src homology 2 domain; comparison between X-ray and NMR-derived structures. Acta Crystallogr Sect F Struct Biol Cryst Commun 68:145-53
Joseph, Raji E; Ginder, Nathaniel D; Hoy, Julie A et al. (2011) Purification, crystallization and preliminary crystallographic analysis of the SH2 domain of IL-2-inducible T-cell kinase. Acta Crystallogr Sect F Struct Biol Cryst Commun 67:269-73
Min, Lie; Wu, Wenfang; Joseph, Raji E et al. (2010) Disrupting the intermolecular self-association of Itk enhances T cell signaling. J Immunol 184:4228-35
Joseph, Raji E; Xie, Qian; Andreotti, Amy H (2010) Identification of an allosteric signaling network within Tec family kinases. J Mol Biol 403:231-42
Andreotti, Amy H; Schwartzberg, Pamela L; Joseph, Raji E et al. (2010) T-cell signaling regulated by the Tec family kinase, Itk. Cold Spring Harb Perspect Biol 2:a002287
Joseph, Raji E; Severin, Andrew; Min, Lie et al. (2009) SH2-dependent autophosphorylation within the Tec family kinase Itk. J Mol Biol 391:164-77

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