Actin networks modulate heterogenous NF-κB dynamics in response to TNFα

The canonical NF-{kappa}B transcription factor RELA is a master regulator of immune and stress responses and is upregulated in PDAC tumours. Here, we characterised previously unknown endogenous RELA-GFP dynamics in PDAC cell lines by live single cell imaging, which revealed rapid, sustained and non-oscillatory nuclear RELA following TNF stimulation. Using Bayesian analysis of single cell datasets with variation in nuclear RELA, we computationally predicted that RELA heterogeneity in PDAC cell lines is dependent on F-actin dynamics. By RNA-seq, we identified the actin regulators NUAK2 and ARHGAP31 as transcriptionally regulated by RELA. In turn, NUAK2 or ARHGAP31 siRNA depletion downregulates TNF-stimulated RELA nuclear localisation in PDAC cells, establishing a novel negative feedback loop regulating RELA activation by TNF. We identify an additional actin-independent feedback loop involving RELB, which suppresses TNF-mediated RELA nuclear localisation following RELA mediated upregulation of RELB. Taken together, we provide computational and experimental support for interdependence between the F-actin network and RELA translocation dynamics in PDAC.