Reactive oxygen species (ROS) such as hydrogen peroxide and superoxide are generated by ligand binding across a diverse range of receptor families. Redox couples provide a means of translating the presence of ROS into useful signals in the cell. Thioredoxin and glutathione-mediated post-translational modifications of proteins (S-thiolation and S-glutathionylation, respectively) have been shown to functionally alter the activity of certain proteins. Few proteins have been investigated in depth to understand this relationship. More broadly, how redox-related effects systemically influence the regulation of receptor signaling pathways is unknown. Challenges in quantifying post-translational events and discerning the effects of one redox couple from another have compounded the difficulties in understanding the role of redox couples in cellular signaling, mandating a modeling-based approach for gaining insight into these biological processes.
Our lab uses computational modeling and wet-lab experimentation to investigate how thiolation/glutathionylation of proteins influences the information flow from receptors to the nucleus. We study these effects primarily in the context of T cell activation through TCR ligation. Research projects include:
Modeling of NF-κB regulation through redox couples in pediatric acute lymphoblastic leukemia
(with Harry Findley, Children's Healthcare of Atlanta and Emory School of Medicine)
There has been increasing interest in the relationship between the NF-κB anti-apoptosis signaling pathway and the generation of reactive oxygen species (ROS) in pediatric acute lymphoblastic leukemia (ALL) during clinical therapy. We are studying two patient-derived ALL cells lines which show differential regulation of NF-κB-activation levels post-treatment with a commonly used chemotherapeutic drug. We are investigating how key redox buffering components protect ALL cells from ROS-generating agents by preventing ROS-mediated downregulation of NF-κB.
Design of microfluidic devices for capturing fast dynamics of T cell signaling
(with Hang Lu, Georgia Tech)
Adoptive transfer of T cells is a promising clinical cancer therapy that relies on enhancing the adaptive immune response to target tumor cells in vivo. Widespread application of this therapy, however, has been hindered by the necessary expansion of large populations of T cells for each patient (often selected for tumor antigen specificity) and loss of functionality of the T cells post-transfer. Our long-term objective is to understand how T cell activation is dampened in vivo by the tumor milieu and to be able to evaluate the responsiveness ex vivo-expanded T cells accurately for cancer therapy. Microfluidic chips are ideal for high-throughput parallel experimentation and automation. In addition, microfluidics also provides the relevant length scales (~microns) and unique physical phenomena (e.g. laminar flow) to handle cells. The type of multiplex data that we can obtain from this technology will enable quantitative modeling of T cell activation and better understanding and characterization of anergy.
Novel nanoprobes for monitoring protein localization during oxidative stress
(with Rob Dickson, Christoph Fahrni, and Christine Payne, Georgia Tech)
Proteins signal through a "circuitry" of protein networks to communicate information about the extracellular environment. Unlike an electrical circuit, however, proteins rely on spatial and temporal changes in order to operate. We are currently limited in what we can observe in a live cell because most probes are too large to allow for some small proteins to operate normally when labeled. These signaling dynamics can only be visualized through the development of greatly improved protein labels that enable the unraveling of intracellular pathways through single molecule interactions. We are developing a new generation of tools to label proteins -- multifunctional, modular Ag nanodots -- that will allow the observation of synchronous multi-protein dynamics. Because subcellular localization plays a critical role in redox regulation during oxidative stress, monitoring real-time movement of key proteins will shed light in how cells maintain compartments' redox potentials out of equilibrium.
Development of new techniques to monitor glutathionylation of proteins
Modeling systemic influences of endogenous hydrogen peroxide on cellular phosphorylation levels