Integrating Single-Cell Experiments and Stochastic Models to Understand and Predict Glucocorticoid Receptor Transport and DUSP1 mRNA Expression Dynamics*

Over-activation of MAPK signaling drives several inflammatory pathologies. Dexamethasone (Dex) is a common corticosteroid that activates glucocorticoid receptors (GR) to induce dual-specificity phosphatase 1 (DUSP1). In turn, DUSP1 mRNA encode for the MAPK phosphatase 1 (MKP1), which dephosphorylates and suppresses signaling of the p38 and JNK MAPK pathways. We integrated immunocytochemistry and smFISH experiments to quantify GR transport and DUSP1 transcription in thousands of single cells. Applying Bayesian Analysis within the framework of Chemical Master Equations, we inferred a minimal model consisting of mechanisms for Dex-dependent GR nuclear import and turnover, GR modulation of DUSP1 promoter activation, transcriptional elongation, and ARE-mediated cytoplasmic mRNA degradation. Our parameterized model quantitatively predicts joint distributions of GR signaling dynamics, DUSP1 transcription site activity, and accumulation of nuclear and cytoplasmic mRNA dynamics across all Dex doses, all times, and under perturbation by transcriptional inhibitors. Our validated model and inference pipeline sets the stage for future investigations for model-based design of steroidal modulation to control inflammatory signaling.