Biology subjects

Ziska, E.

Publications and source records attributed to Ziska, E..

4 recordsLinked to original sources

bioRxiv2024

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.

cell biology↗

bioRxiv2023

IRAK4 autophosphorylation controls inflammatory signaling by activating IRAK oligomerization

The controlled oligomerization of signaling proteins is an essential feature of many inflammatory signaling pathways. An example is IL-1 receptor signaling, which relies on the oligomerization of the Death Domain (DD)-containing proteins MyD88 and IRAK family kinases. This process leads to the assembly of the Myddosome signaling complex, and disrupting assembly holds potential for anti-inflammatory treatments. However, IRAKs signaling activity is also regulated by auto-/trans-phosphorylation, and it is unclear if these processes operate at or downstream of Myddosome assembly. Here, we find that the initial stage of Myddosome assembly is solely controlled by MyD88:IRAK4 DD interactions. In later stages, IRAK4 auto-phosphorylation serves as a switch, regulating IRAK1/2/3 incorporation and DD oligomerization. Small molecule inhibitors of IRAK4 kinase activity block this later stage of assembly, explaining how they dampen inflammatory signaling. Our data reveals IRAK4 auto-phosphorylation as an energy-dependent switch activating the heterotypic assembly of IRAKs DDs and downstream inflammatory IL-1 signaling. This highlights how a signaling cascade integrates phosphorylation and protein oligomerization steps.

immunology↗

bioRxiv2023

Myddosome clustering in IL-1 receptor signaling regulates the formation of an NF-kB activating signalosome

Signaling pathways can produce digital invariant outputs and analog outputs that scale with the amount of stimulation. In IL-1 receptor (IL-1R) signaling both types of outputs require the Myddosome, a multi-protein complex. The Myddosome is required for polyubiquitin chain formation and NF-kB signaling. However, the ways in which these signals are spatially and temporally regulated to drive switch-like and proportional outcomes is not understood. We find that during IL-1R signaling, Myddosomes dynamically re-organize into large, multi-Myddosome clusters at the cell membrane. Blockade of Myddosome clustering using nanoscale extracellular barriers reduces NF-kB activation. We find that Myddosomes function as a scaffold that assembles an NF-kB signalosome consisting of E3-ubiquitin ligases TRAF6 and LUBAC, K63/M1-linked polyubiquitin chains, phospho-IKK, and phospho-p65. This signalosome preferentially assembles at regions of high Myddosome density, which enhances the recruitment of TRAF6 and LUBAC. Extracellular barriers that restrict Myddosome clustering perturbed the recruitment of both ligases. We found that LUBAC was especially sensitive to clustering with a sevenfold lower recruitment to single Myddosomes than clustered Myddosomes. This data reveals that the clustering behavior of Myddosome provides the basis for digital and analog IL-1R signaling.

cell biology↗

bioRxiv2020

On demand MyD88 oligomerization is controlled by IRAK4 during Myddosome signaling

A recurring feature of innate immune receptor signaling is the self-assembly of signaling proteins into oligomeric complexes. The Myddosome is an oligomeric complex that is required to transmit inflammatory signals from TLR/IL1Rs and consists of MyD88 and IRAK family kinases. However, the molecular basis for how Myddosome proteins self-assemble and regulate intracellular signaling remains poorly understood. Here, we developed a novel assay to analyze the spatiotemporal dynamics of IL1R and Myddosome signaling in live cells. We found that MyD88 oligomerization is inducible and initially reversible. Moreover, the formation of larger, stable oligomers consisting of more than 4 MyD88s triggers the sequential recruitment of IRAK4 and IRAK1. Notably, genetic knockout of IRAK4 enhanced MyD88 oligomerization, indicating that IRAK4 controls MyD88 oligomer size and growth. MyD88 oligomer size thus functions as a physical threshold to trigger downstream signaling. These results provide a mechanistic basis for how protein oligomerization might function in cell signaling pathways.

immunology↗