Computational Modeling Predicts Phosphatase Oxidation as an Important Axis of Redox Regulation in IL-4 Signaling

Abstract

Reactive oxygen species (ROS) are produced following activation of several types of cell surface receptors and can play an important role in modulating cell signaling. How simultaneous oxidative modifications of multiple proteins, sometimes with potentially opposite effects, regulate cell signaling is not well understood at the system level. We are using computational modeling based on quantitative experimental measurements to develop a systemic understanding of redox regulation of cell signaling in the context of the IL-4 signaling pathway. We observe that IL-4 signaling in Jurkat cells is accompanied by transient ROS production, and ROS augment signaling activity as measured by STAT6 phosphorylation. A number of candidate redox-regulated mechanisms exist in the IL-4 pathway that could contribute to the observed outcomes; however, it is technically challenging to directly measure redox modifications of the possibly redox-regulated proteins. To circumvent this issue, we have developed kinetic models of IL-4 signaling that incorporate competing hypotheses regarding redox regulatory mechanisms. With the guidance of measurable experimental data we are using innovative model selection strategies to determine the best candidate models. We have also acquired time course data for processes not directly related to redox regulation, such as transcriptional negative feedback regulation and proteasomal degradation as mechanisms for downregulating IL-4 signaling, that aid model selection and validation. Our results so far indicate that reversible oxidative inhibition of phosphatases and compartmentation of phosphatase activity between subcellular compartments may be the primary redox regulatory mechanisms in IL-4 signaling. These studies will help evolve an understanding of how oxidative modifications of different components of the signaling pathway operate in parallel along with better studied post-translational modification mechanisms of protein regulation to determine the overall dynamics of cell signaling.