Clustering of the ζ-Chain Can Initiate T Cell Receptor Signaling

Yuanqing Ma,Katharina Gaus,Yean J Lim,Aleš Benda,Jesse Goyette,Jieqiong Lou

doi:10.3390/ijms21103498

Abstract

T cell activation is initiated when ligand binding to the T cell receptor (TCR) triggers intracellular phosphorylation of the TCR-CD3 complex. However, it remains unknown how biophysical properties of TCR engagement result in biochemical phosphorylation events. Here, we constructed an optogenetic tool that induces spatial clustering of ζ-chain in a light controlled manner. We showed that spatial clustering of the ζ-chain intracellular tail alone was sufficient to initialize T cell triggering including phosphorylation of ζ-chain, Zap70, PLCγ, ERK and initiated Ca2+ flux. In reconstituted COS-7 cells, only Lck expression was required to initiate ζ-chain phosphorylation upon ζ-chain clustering, which leads to the recruitment of tandem SH2 domain of Zap70 from cell cytosol to the newly formed ζ-chain clusters at the plasma membrane. Taken together, our data demonstrated the biophysical relevance of receptor clustering in TCR signaling.

Highlights

T cell activation is initialized by peptide-bound major histocompatibility complex molecules engaging the αβ chain of the T cell receptor (TCR)
To avoid any association of the ζ-chain with endogenous TCR subunits, we replaced the extracellular and transmembrane domain of the ζ-chain with the membrane anchor of Lck so that the intracellular domain of ζ-chain is attached to the plasma membrane via palmitoylation and myristoylation groups [19]
LIC-Z did not trigger signaling via endogenous components of the TCR-CD3 complex since the transmembrane domain of ζ-chain that is required for interaction with other subunit [39] was replaced by the membrane anchor of Lck (Lck10)

Summary

Introduction

T cell activation is initialized by peptide-bound major histocompatibility complex (pMHC) molecules engaging the αβ chain of the TCR. T cells that express the extracellular and transmembrane domains of the co-receptor CD8 fused to the intracellular domain of ζ-chain respond to ligation in a similar manner as the TCR-CD3 complex, including activation of the canonical TCR signaling pathways [3]. The ability of CARs to elicit T cell responses analogous to the native TCR by integrating into the T cell signaling network has led to the clinical success of CAR T cell therapies [4]. It raises the fundamental question of whether other mechanisms apart from conformational changes could facilitate TCR triggering

Objectives

Methods

Results

Conclusion