SNX9-induced membrane tubulation regulates CD28 cluster stability and signalling.

Manuela Ecker,Pascal Rossatti,Verena M Betzler,Nicholas Ariotti,Natasha Kapoor-Kaushik,Maté Biro,Richard Schregle,Daryan Kempe,Gregory Mi Redpath,Jeremie Rossy

doi:10.7554/elife.67550

Abstract

T cell activation requires engagement of a cognate antigen by the T cell receptor (TCR) and the co-stimulatory signal of CD28. Both TCR and CD28 aggregate into clusters at the plasma membrane of activated T cells. While the role of TCR clustering in T cell activation has been extensively investigated, little is known about how CD28 clustering contributes to CD28 signalling. Here, we report that upon CD28 triggering, the BAR-domain protein sorting nexin 9 (SNX9) is recruited to CD28 clusters at the immunological synapse. Using three-dimensional correlative light and electron microscopy, we show that SNX9 generates membrane tubulation out of CD28 clusters. Our data further reveal that CD28 clusters are in fact dynamic structures and that SNX9 regulates their stability as well as CD28 phosphorylation and the resulting production of the cytokine IL-2. In summary, our work suggests a model in which SNX9-mediated tubulation generates a membrane environment that promotes CD28 triggering and downstream signalling events.

Highlights

T cell activation is at the centre of the adaptive immune response and relies primarily on the T cell receptor (TCR)
A blinded analysis of the localisation of sorting nexin 9 (SNX9) revealed that it was present at the immunological synapse from 2 min onwards, where it was detected in 75% ± 7.6% of the conjugates after 15 min of activation (Figure 1A and B)
As our observations showed that CD28 triggering leads to the formation of SNX9-p ositive membrane structures at the immunological synapse to a higher extent than TCR stimulation alone, we sought to determine the potential connection between SNX9 and CD28 clusters

Summary

Introduction

T cell activation is at the centre of the adaptive immune response and relies primarily on the T cell receptor (TCR). Stimulation of TCR and CD28 is required to localise CD28 within the immunological synapse (Sanchez-Lockhart et al, 2008), whose formation is impaired in absence of CD28 co-simulation (Wülfing et al, 2002; Huang et al, 2002). Localisation and activation of CD28 at the synapse are required to trigger downstream signalling events required for productive T cell activation (Sanchez-Lockhart et al, 2008; Tseng et al, 2005; Yokosuka et al, 2008; Huang et al, 2002). We sought to investigate how the membrane remodelling properties of SNX9 contribute to organise the immunological synapse, T cell activation and CD28 signalling. Together our data indicate that membrane organisation at CD28 clusters by SNX9 promotes CD28 triggering and contributes to steer T cells away from anergy during activation

Results

Discussion

Materials and methods