Internal Medicine

Jon C. Houtman, PhD


Associate Professor of Microbiology
Associate Professor of Internal Medicine

Contact Information

Office: 2210 Medical Education and Research Facility
375 Newton Rd
Iowa City, IA 52242
Phone: 319-335-7780

Lab: 2234B Medical Education and Research Facility
375 Newton Rd
Iowa City, IA 52242
Phone: 319-335-7597



BA, Biology and Chemistry, University of Minnesota, Morris
PhD, Cellular and Molecular Biology, University of Wisconsin-Madison

Post Doctorate, Molecular Immunology, National Cancer Institute/NIH/DHHS

Education/Training Program Affiliations

Biosciences Graduate Program
Department of Microbiology Graduate Program
Interdisciplinary Graduate Program in Immunology
Interdisciplinary Graduate Program in Molecular and Cellular Biology
Medical Scientist Training Program

Research Summary

T cell activation is critical for the ability of the human immune system to properly fight an infection by a bacteria, virus or parasite. However, inappropriate or aberrant T cell induction is crucial for the initiation and progression of numerous human diseases, including T cell lymphoma/leukemia, human malignancies, autoimmune disorders, cardiovascular disease and transplant rejection. Human T cells require two signals to become fully stimulated: a primary signal from activation of the T cell receptor (TCR) and a second signal from the induction of one or more costimulatory receptors. Upon TCR and/or costimulatory receptor activation, a number of intracellular signal transduction pathways in the T cell are stimulated, which then control alterations in T cell function. These pathways are regulated by the activation and deactivation of protein tyrosine kinases and phosphatases that control the interactions between receptor, enzymatic effecter proteins and/or non-enzymatic adaptor proteins. Because of their critical role in T cell activation, it is vital that we understand the regulation, formation and function of these signaling complexes in order to develop new treatments for diseases linked to aberrant T cell activation. The goal of my laboratory is to understand the molecular mechanism of the formation of the multiprotein signaling complexes that occur after TCR and/or costimulatory receptor activation. Currently, my laboratory is working on two main projects.

Project 1: The overall goal of this project is to determine the molecular mechanism for the activation and function of the adaptor protein LAT. Upon TCR activation, LAT is phosphorylated on four conserved tyrosines, which then serve as the principle nucleation site for TCR-induced signaling complexes. We are using biochemical and imaging techniques to identify the kinases/phosphatases that regulate the phosphorylation of LAT, characterize the phosphorylation kinetics of individual LAT tyrosines and examine how alterations in these events affect the formation and composition of LAT-mediated complexes. Additionally, we are utilizing highly quantitative biophysical and biochemical tools to characterize the interaction of the adaptor protein Grb2 with various ligands, such as LAT and SOS1, and how these interactions facilitate the formation of LAT-mediated complexes. Ultimately, these studies will allow us to rationally design treatments for diseases linked to the activation of LAT, including human malignancies, autoimmune disorders and cardiovascular disease.

Project 2: The overall focus of this project is to characterize the molecular mechanism for the crosstalk between TCR- and costimulatory receptor-induced signaling pathways. We are interested in how the integrin VLA-4 facilitates the TCR-induced activation of human T cells, with a focus on the tyrosine kinases Pyk2 and Fak as a node of intersection between these two receptors. Fak and Pyk2 are critical for integrating receptor-mediated signals the control the actin cytoskeleton and are frequently overexpressed in human cancers. This project uses biochemical and cell biological techniques to determine the timing and mechanism of the TCR and VLA-4-induced activation of Fak and Pyk2 and characterize the role these kinases play in T cell activation. Additionally, we are examining the function of Toll-like receptors (TLRs) in T cell induction. We are using quantitative cell biological and biochemical methods to examine the molecular mechanism of TLR-induced costimulation. Collectively, these studies will not only allow us to better understand the normal immune response to pathogens, but also help us develop novel treatments for debilitating diseases linked to costimulatory receptor function, including autoimmune disorders, human cancers and transplant rejection.

Center, Program and Institute Affiliations

Center for Immunology and Immune-based Diseases
Holden Comprehensive Cancer Center
Institute for Clinical and Translational Science

Selected Publications

Show All

Chapman N, Yoder A, Barbón K, Bilal M, Connolly S, Houtman J.  Proline-rich tyrosine kinase 2 controls PI3-kinase activation downstream of the T cell antigen receptor in human T cells.  J Leukoc Biol.  2014 November. Epub ahead of print.

Tremblay M, Houtman J.  TCR-mediated functions are enhanced in activated peripheral blood T cells isolated from leucocyte reduction systems.  J Immunol Methods.  2014 November. Epub ahead of print.

Tremblay M, Bilal M, Houtman J.  Prior TLR5 induction in human T cells results in a transient potentiation of subsequent TCR-induced cytokine production.  Mol Immunol.  2014 February. 57(2):161-70.

Chapman N, Connolly S, Reinl E, Houtman J.  Focal adhesion kinase negatively regulates lck function downstream of the T cell antigen receptor.  J Immunol.  2013 December 15. 191(12):6208-21.

Chapman N, Bilal M, Cruz-Orcutt N, Knudson C, Madinaveitia S, Light J, Houtman J.  Distinct signaling pathways regulate TLR2 co-stimulatory function in human T cells.  Cell Signal.  2013 March. 25(3):639-50.

Bartelt R, Houtman J.  The adaptor protein LAT serves as an integration node for signaling pathways that drive T cell activation.  Wiley Interdiscip Rev Syst Biol Med.  2013 January. 5(1):101-10.

Chapman N, Yoder A, Houtman J.  Non-catalytic functions of Pyk2 and Fyn regulate late stage adhesion in human T cells.  PLoS One.  2012. 7(12):e53011.

Collins M, Bartelt R, Houtman J.  T cell receptor activation leads to two distinct phases of Pyk2 activation and actin cytoskeletal rearrangement in human T cells.  Mol Immunol.  2010 May. 47(9):1665-74.

Collins M, Tremblay M, Chapman N, Curtiss M, Rothman P, Houtman J.  The T cell receptor-mediated phosphorylation of Pyk2 tyrosines 402 and 580 occurs via a distinct mechanism than other receptor systems.  J Leukoc Biol.  2010 April. 87(4):691-701.

Cruz-Orcutt N, Houtman J.  PI3 kinase function is vital for the function but not formation of LAT-mediated signaling complexes.  Mol Immunol.  2009 July. 46(11-12):2274-83.

Date Last Modified: 08/04/2015 - 09:28:35