Caveolin-1 Influences LFA-1 Redistribution upon TCR Stimulation in CD8 T Cells.

Jessica G. Borger,Andrew Filby,Celine Garcia,Vicky L. Morrison,Rose Zamoyska,Fabio Simbari,Susanna C. Fagerholm,Liisa M. Uotila

doi:10.4049/jimmunol.1700431

Abstract

TCR stimulation by peptide–MHC complexes on APCs requires precise reorganization of molecules into the area of cellular contact to form an immunological synapse from where T cell signaling is initiated. Caveolin (Cav)1, a widely expressed transmembrane protein, is involved in the regulation of membrane composition, cellular polarity and trafficking, and the organization of signal transduction pathways. The presence of Cav1 protein in T cells was identified only recently, and its function in this context is not well understood. We show that Cav1-knockout CD8 T cells have a reduction in membrane cholesterol and sphingomyelin, and upon TCR triggering they exhibit altered morphology and polarity, with reduced effector function compared with Cav1 wild-type CD8 T cells. In particular, redistribution of the β2 integrin LFA-1 to the immunological synapse is compromised in Cav1-knockout T cells, as is the ability of LFA-1 to form high-avidity interactions with ICAM-1. Our results identify a role for Cav1 in membrane organization and β2 integrin function in primary CD8 T cells.

Highlights

The abundance of Cav2 was greatly reduced in Cav1-KO CD8 T cells (Fig. 1A), consistent with reports showing that when not oligomerized with Cav1, Cav2 was rapidly degraded by the proteosome [42]
As previously suggested [37,38,39,40], we could not identify any caveolae-like structures in naive CD8 T cells whereas they could be seen by electron microscopy in A431 cells (Supplemental Fig. 1D), confirming that Cav1 in T cells was not associated with caveolae
We show that lack of Cav1 in primary CD8 T cells directly impacted the lipid content of the T cell membrane, with a specific overall reduction in the abundance of short-chain fatty acid sphingomyelins and cholesterol

Summary

Introduction

There was impaired homotypic adhesion and impaired LFA-1 recruitment to the IS upon TCR/pMHC association in Cav1-deficient CD8 T cells, together with a reduction in their response to Ag. Loss of Cav1 reduced the cholesterol and sphingomyelin content of CD8 T cells, suggesting that Cav1 plays a role in membrane lipid homeostasis, which influenced the redistribution of LFA-1 and its avidity for ICAM-1. To assess whether the reduced activation of Cav1-KO CD8 T cells was linked to changes in IS formation, we used a highthroughput imaging flow cytometer, ImageStream, to obtain a measure of the spatial distribution of LFA-1 (CD11a) from a large number of conjugates over multiple early time points.

Results

Conclusion