Thomas E. Smithgall, Ph.D.


Thomas Smithgall William S. McEllroy Professor & Chair
530 BSP2
450 Technology Drive
Pittsburgh, Pennsylvania 15219

Phone: (412) 648-8106
Fax: (412) 624-1401
E-mail: tsmithga@pitt.edu

Lab Phone: (412) 648-9240

Biography


      Dr. Smithgall is Professor and Chairman of Microbiology and Molecular Genetics at the University of Pittsburgh School of Medicine. Dr. Smithgall received his Ph.D. from the Department of Pharmacology at the University of Pennsylvania School of Medicine and completed his postdoctoral training at the National Cancer Institute of the National Institutes of Health in Besthesda, MD.

Research


      Our research focuses on non-receptor protein-tyrosine kinase structure, regulation and signal transduction in cancer, AIDS, and embryonic stem cell biology.

Src family kinases, HIV Nef, and AIDS. Our group continues to explore the interaction of Src family kinases with Nef, an HIV accessory protein essential for AIDS progression. Nef binds directly to the SH3 domains of three Src family members found in HIV target cells (Hck, Lyn and c-Src), leading to constitutive kinase activation. At the molecular level, we found that the Nef:Hck complex represents a novel active conformation of the kinase, which has important implications for both Src family kinase signal transduction and selective inhibitor discovery. In collaboration with the University of Pittsburgh Drug Discovery Institute, we have completed in vitro and cell-based high-throughput screens of chemical libraries to identify selective inhibitors of the Nef:Hck complex. The screens identified two new classes of compounds with potent anti-HIV activity in vitro. These compounds represent exciting new tools for exploring the role of Nef-SFK signaling in HIV pathogenesis and may represent new leads for anti-HIV drug development. In collaboration with the Department of Structural Biology, we are actively seeking to map the binding site for these small molecule inhibitors within the Nef:Hck complex.

Src family kinases, Bcr-Abl and chronic myelogenous leukemia (CML). We have recently completed a study of the interaction of SFKs with Bcr-Abl, the chimeric tyrosine kinase associated with CML. Using a sophisticated mass spectrometry-based approach, we were able to identify seven previously unrecognized sites of SFK-mediated phosphorylation in the regulatory SH3-SH2 region of Bcr-Abl. Follow-up experiments with phosphospecific antibodies show that these phosphorylation events occur in CML cells, where they appear to be essential for Bcr-Abl transforming function. We believe these findings are important because they suggest that Bcr-Abl recruits proteins which serve as upstream regulators, leading to further amplification of the oncogenic signal. This finding could also explain the remarkable efficacy of dual Src/Abl kinase inhibitors which are currently in clinical trials for the management of Gleevec-resistant CML. This work was published in the Journal of Biological Chemistry and cited by the Faculty of 1000/Biology for its significance to the field.

Chemical genetics of Src family kinases in ES cells. A new area of investigation in our lab involves the role of Src family kinases in the early fate determination of murine embryonic stem (ES) cells. A few years ago we discovered that selective pharmacological inhibitors of Src family kinases could either induce terminal differentiation or promote self-renewal of ES cells, suggesting the Src-family kinases control key signal pathways related to these biological outcomes. Because ES cells express multiple Src family members, we have taken a chemical genetics approach to the problem. This entails engineering functionally silent mutations into the kinase genes that renders them selectively sensitive to specific inhibitors. Our plan is to introduce these mutations into ES cells with standard gene-targeting approaches, thus allowing specific pharmacological assessment of the role of single kinase activities on developmental outcomes. Our longer term goal is to identify kinases that can be specifically manipulated with selective inhibitors to either force renewal or guide desired developmental fates.

The c-fes tyrosine kinase: Oncogene or tumor suppressor? While tyrosine kinase activity is most commonly associated with tumor formation and progression, we recently made the unexpected finding that expression of the c-Fes tyrosine kinase is commonly lost in colonic epithelial cells from colon cancer patients. Like many other tumor suppressor genes, the c-fes promoter region is heavily methylated in DNA from tumor specimens, but not in normal epithelial cells where the gene is expressed. We are now formally testing a tumor suppressor role for c-fes in APC-min mice, an animal model that is genetically predisposed to intestinal cancer. We plan to cross fes-null animals into the APC-Min background and look for changes in tumor latency.

Selected Publications


  • Meyn III, M.A. and Smithgall, T.E. Chemical Genetics Identifies c-Src as an Activator of Primitive Ectoderm Formation in Murine Embryonic Stem Cells. Science Signaling in press, 2009.


  • Emert-Sedlak, L., Kodama, T., Lerner, E.C., Trible, R.P., Dai, W., Foster, C., Day, B., Lazo, J.S., and Smithgall, T.E. Chemical library screens targeting an HIV-1 Nef Accessory Factor/host cell kinase complex identify novel anti-retroviral compounds. ACS Chemical Biol. in press, 2009.


  • Poe, J.A. and Smithgall, T.E. Bimolecular Fluorescence Complementation Reveals Residues Essential for HIV-1 Nef Oligomerization, CD4 Downregulation and Viral Replication. J. Mol. Biol. in press, 2009.


  • Choi, Y., Seeliger, M., Panjarian, S., Kim, H., Deng, X., Sim, T., Couch, B., Koleske, T., Smithgall, T.E. and Gray, N. N-Myristoylated Abl Tyrosine Kinase Localizes to the Endoplasmic Reticulum upon Binding to an Allosteric Inhibitor. J. Biol. Chem. 284: 29005-29014, 2009.


  • Iacob, R.E., Dumitrescu, T.P., Zhang, J., Gray, N.S., Smithgall, T.E., and Engen J.R. 2009. "Conformational disturbance in Abl kinase upon mutation and deregulation" Proc. Natl. Acad. Sci. USA 106: 1386-912009 | Abstract


  • Dumitrescu, T.P., Peterson, L.F., Donato, N.J., and Smithgall, T.E. 2008. "An inhibitor-resistant mutant of Hck protects CML cells against the anti-proliferative and apoptotic effects of the broad-spectrum Src-family kinase inhibitor, A-419259" Oncogene 27: 7055-7069. | Abstract


  • Shaffer, J.M. and Smithgall, T.E. 2008. "Promoter methylation blocks c-fes protein-tyrosine kinase gene expression in colorectal cancer" Genes, Chromosomes and Cancer 48: 272-284. | Abstract


  • Trible, R.P., Emert-Sedlak, L., Wales, T., Ayyavoo, V., Engen, J.R. and Smithgall, T.E. 2007. "Allosteric Loss-of-function Mutations in HIV-1 Nef from a Long-Term Non-Progressor" J. Mol. Biol. 374: 121-129. | Abstract


  • Meyn III, M.A., Wilson, M.B., Abdi, F.A., Fahey, N., Schiavone, A.P., Wu, J., Hochrein, J.M., Engen, J.R., and Smithgall, T.E. 2006. "Src family kinases phosphorylate the Abl SH3-SH2 region and modulate Bcr-Abl transforming activity" J. Biol. Chem. 281: 30907-30916, 2006. Cited by the Faculty of 1000/Biology | Abstract


  • Trible RP, Emert-Sedlak L, Smithgall TE. 2006. "HIV-1 Nef selectively activates Src family kinases Hck, Lyn, and c-Src through direct SH3 domain interaction" J Biol Chem. 281:27029-38. | Abstract



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