An experimental and computational approach to unraveling interconnected TLR signaling cascades

Abstract

Previously, a modeling tool was used to construct a model of the TLR4 signaling cascade, and here the utility of the modeling tool in two dimensions – adaptability (different types of TLR cascades and readout systems) and power (the ease with which models of more complex cascades could be created by combining simpler interconnected cascades) was evaluated. In the first case, how the tool would handle a similar yet distinct cascade, TLR5, was evaluated. Although there are differences between the TLR4 and TLR5 signaling cascades, the experimental and modeling data were closely aligned, and the data looked similar regardless of whether NFκB activation or transcription of IL-1β was used as the readout system, further validating the utility of the model. Next, to address multiple interconnected signaling cascades, the modeling process was evaluated by creating a model that combined both TLR4 and TLR5 cascades. This was done by using software to first generate models for TLR4 and TLR5 individually, and subsequently using an additional feature of the software to combine the two existing models to create a new dual signaling model. The experimental and modeling data when TLR4 and TLR5 signaling cascades were simultaneously activated were then evaluated. Once again the modeling data recapitulated the experimental data with both sets of data showing that dual signaling leads to competition between the signaling cascades. Collectively, these results show the adaptability and power of the modeling and experimental systems to investigate multiple interconnected TLR signaling cascades.