Bottom-up reconstruction of functional Death Domain Signalosomes reveals a requirement for polymer stability and avidity

A key feature of innate immune signaling is the compartmentalization of signaling effectors into cellular structures referred to as signalosomes. Critical to the formation of these compartments are protein polymers composed of Death Domains (DD). However, the biophysical properties these polymeric scaffolds require for signal transduction are not clearly defined. Here, we engineered a single-component signalosome, referred to as Chimeric Higher-order Assemblies for Receptor Mediated Signaling (CHARMS). We found that CHARMS functionality depends on the stability provided by the DD polymer, which could also be achieved with bacterial DDs and synthetic filament-forming domains. This demonstrates the importance of kinetic stability and inducibility, irrespective of the origin of the motif. By varying the multiplicity of TRAF6 interaction motifs, we demonstrate that avidity is a tunable property that can control the amplitude of signaling outputs. This work lays out a reductionist framework to dissect the required properties of signaling through polymeric scaffolds by adjusting their assembly kinetics, stability and avidity.