ERM-Dependent Assembly of T Cell Receptor Signaling and Co-stimulatory Molecules on Microvilli prior to Activation

Shirsendu Ghosh,Vincenzo Di Bartolo,Liron Tubul,Eyal Shimoni,Elena Kartvelishvily,Tali Dadosh,Sara W Feigelson,Ronen Alon,Andres Alcover,Gilad Haran

doi:10.1016/j.celrep.2020.02.069

Shirsendu Ghosh, Vincenzo Di Bartolo + Show 8 more

Open Access

https://doi.org/10.1016/j.celrep.2020.02.069

Copy DOI

Abstract

T cell surfaces are covered with microvilli, actin-rich and flexible protrusions. We use super-resolution microscopy to show that ≥90% of T cell receptor (TCR) complex molecules TCRαβ and TCRζ, as well as the co-receptor CD4 (cluster of differentiation 4) and the co-stimulatory molecule CD2, reside on microvilli of resting human Tcells. Furthermore, TCR proximal signaling molecules involved in the initial stages of the immune response, including the protein tyrosine kinase Lck (lymphocyte-specific protein tyrosine kinase) and the key adaptor LAT (linker for activation of Tcells), are also enriched on microvilli. Notably, phosphorylated proteins of the ERM (ezrin, radixin, and moesin) family colocalize with TCRαβ as well as with actin filaments, implying a role for one or more ERMs in linking the TCR complex to the actin cytoskeleton within microvilli. Our results establish microvilli as key signaling hubs, in which the TCR complex and its proximal signaling molecules and adaptors are preassembled prior to activation in an ERM-dependent manner, facilitating initial antigen sensing.

Highlights

T cells play a pivotal role in adaptive immunity
We recently discovered that in human peripheral blood T cells and in effector T lymphocytes differentiated from these lymphocytes, TCRab molecules are preferentially localized to microvilli, suggesting a role for these dynamic protrusions in initial T cell recognition of cognate antigenic peptides presented by dendritic cells and other antigen-presenting cells (APCs) (Jung et al, 2016)
Mapping the Distribution of Membrane Proteins in Relation to Microvilli We previously demonstrated that a combination of variableangle total internal reflection microscopy (VA-TIRFM) and stochastic localization nanoscopy (SLN) can map the distribution of peripheral blood human T cell surface proteins with respect to microvilli (Jung et al, 2016)

Summary

Introduction

T cells play a pivotal role in adaptive immunity. When encountering antigen-presenting cells (APCs), T cells undergo a major reorganization of their surface, with a subset of these encounters leading to the formation of immunological synapses (ISs) (Dustin, 2014; Grakoui et al, 1999; Monks et al, 1998). The TCR complex (composed of the transmembrane proteins TCRab, CD3g,d,ε, and TCRz) initiates the T cell immune response after it recognizes foreign-antigen-derived peptides bound to major histocompatibility complex (MHC) molecules on the surface of APCs. The roles of the TCR co-receptors CD4 (cluster of differentiation 4) or CD8, adhesion and cosignaling receptors like CD2, and proximal signaling proteins such as the protein tyrosine kinase Lck (lymphocyte-specific protein tyrosine kinase), the adaptor LAT (linker for activation of T cells), and the tyrosine phosphatase CD45 are well described (Dustin, 2014; Kaizuka et al, 2009; Malissen and Bongrand, 2015; Monks et al, 1998). While several T-cell-related or more general models were proposed to explain protein distribution on cellular surfaces, (Davis and van der Merwe, 2006; Lillemeier et al, 2010; Roh et al, 2015; Sezgin et al, 2017; Simons and Sampaio, 2011), much remains to be learned about the organization of key surface receptors implicated in T-cell activation and the formation of functional immune synapses

Results

Discussion

Conclusion