The research in my laboratory focuses primarily on understanding the physiological processes mediated by Src-family kinases, a group of highly related non-receptor tyrosine kinases originally identified as oncogenes. To facilitate analysis of pathways controlled by these genes, mouse mutants lacking different Src kinases were isolated. Despite the fact that these genes are broadly expressed, mutant mice showed phenotypes in only a selected subset of cells. A mutation in one of these kinases, Fyn, results in observable defects in skin cells, hippocampus in the brain, and T lymphocytes. In general, the mutant mice, and cell lines derived from them, are being used to delineate affected pathways and facilitate identification of potential downstream targets. The studies on these mice also provide insight into the mechanisms by which Src kinases promote oncogenesis.
More specifically, current laboratory interests fall into two main categories. One is the role of Src kinases in T cell development, and the other is the function of Src kinases in epithelial cell growth and differentiation. T cells express two Src family kinases, Fyn and Lck. Loss of Lck results in impaired T cell development. In contrast, fyn mutants have normal numbers of T cells and have relatively modest defects in T cell activation, although single positive thymocytes fail to proliferate in vitro. However, recently we demonstrated that Fyn is selectively required for development of NKT cells, a unique lymphoid population with characteristics of NK cells and T lymphocytes. NKT cells appear capable of suppressing a variety of deviant immune responses, including autoimmunity and GVHD. Our future directions are geared towards understanding how Src kinases, especially Fyn, mediate the phenotypic effects observed in the mutants. The types of questions to be addressed include i) how does Fyn control NKT cell development; ii) defining the molecular features of Src kinases that drive proliferation/expansion of thymocytes; iii) defining the requirement for Src kinases in mediating immune responses in vivo. We are also using the mutant mice to determine how loss of these molecules affect formation of supramolecular structures associated with T cell/B cell synapse.
A second area of active study is the role of Src kinases in regulating epithelial growth and differentiation. We demonstrated that Fyn is required for proper differentiation of certain types of epithelial cells. To begin understanding how Fyn regulates differentiation, we isolated a novel signaling protein that interacts with Src kinases and can bind other signaling intermediates. Based on these properties, we named the protein, SRCASM, for Src activating and signaling molecule. We are now studying the function of Srcasm in a variety of epithelial cells, including breast cancer. In addition, we are examining the function of Src kinases in epithelial biology by generating mice deficient in multiple Src kinases using conditional mutations. This will allow us to examine their role in cell adhesion and proliferative/differentiation pathways.
Publications:
Cabodi, S., Calautti, E., Kuroki, T., Stein, P.L., and Dotto, G.P.: A Protein Kinase C eta / Fyn dependent pathway leading to keratinocyte growth arrest and differentiation. Molec. Cell 6:1121-1129, 2000.
Seykora, J.T., Mei, L., Dotto, G.P., and Stein, P.L.: Srcasm: a novel Src activating and signaling molecule, J. Biol. Chem. 277:2812-2822, 2002.
Gadue, P., and Stein, P.L.: NKT cell precursors exhibit differential cytokine regulation and require Itk for efficient maturation. J. Immun. 169:2397-2406, 2002.
Gadue, P., Yin, L., Jain, S., and Stein, P.L.: Restoration of NKT cell development in fyn mutants by a TCR reveals a requirement for Fyn during early NKT cell ontogeny. J. Immun. 172:6093-6100, 2004.
