Phase separation of signaling molecules promotes T cell receptor signal transduction

TLDR

Receptor activation reorganizes downstream signaling molecules into micrometer‑ or submicrometer‑sized clusters, but the functional impact of this clustering has been unclear. The authors reconstituted a 12‑component TCR signaling cascade on model membranes, linking receptor activation to actin assembly. TCR phosphorylation induced liquid‑like phase separation of signaling proteins, forming kinase‑rich, phosphatase‑poor clusters that enhanced actin assembly and amplified signaling in vitro and in Jurkat T cells, demonstrating that phase separation creates a compartment that facilitates signal transduction.

Abstract

Activation of various cell surface receptors triggers the reorganization of downstream signaling molecules into micrometer- or submicrometer-sized clusters. However, the functional consequences of such clustering have been unclear. We biochemically reconstituted a 12-component signaling pathway on model membranes, beginning with T cell receptor (TCR) activation and ending with actin assembly. When TCR phosphorylation was triggered, downstream signaling proteins spontaneously separated into liquid-like clusters that promoted signaling outputs both in vitro and in human Jurkat T cells. Reconstituted clusters were enriched in kinases but excluded phosphatases and enhanced actin filament assembly by recruiting and organizing actin regulators. These results demonstrate that protein phase separation can create a distinct physical and biochemical compartment that facilitates signaling.