TNFR1 mediates heterogeneity in single-cell NF-κB activation.

Nuclear factor kappa B (NF-κB) is a key regulator in immune signaling and is known to exhibit a digital activation pattern. Yet the molecular basis underlying the heterogeneity in NF-κB activation at single-cell level is not entirely understood. Here, we show that NF-κB activation in single cells is largely regulated by intrinsic differences at the receptor level. Using the genome editing and time-lapse imaging, we directly characterize endogenous TNFR1 dynamics and NF-κB activation from the same single cells. Total internal reflection fluorescence (TIRF) microscopy shows that endogenous TNFR1 forms pre-ligand clusters in the resting cells. Upon tumor necrosis factor (TNF) stimulation, the diffusion coefficient of membrane TNFR1 was significantly decreased and a substantial level of TNFR1 undergoes oligomerization to form trimers and hexamers. Moreover, multi-color cell imaging reveals that both digital and graded information processing regulate NF-κB activation across different TNFR1 expression levels. Our results indicate that single-cell NF-κB activation potential strongly correlates with its TNFR1 characteristics.