Retrograde and Anterograde Transport of Lat-Vesicles during the Immunological Synapse Formation: Defining the Finely-Tuned Mechanism.

Juan Saez,Massiullah Shafaq-Zadah,Andrés Zucchetti,Claire Hivroz,Ludger Johannes,Stephanie Dogniaux

doi:10.3390/cells10020359

Abstract

LAT is an important player of the signaling cascade induced by TCR activation. This adapter molecule is present at the plasma membrane of T lymphocytes and more abundantly in intracellular compartments. Upon T cell activation the intracellular pool of LAT is recruited to the immune synapse (IS). We previously described two pathways controlling LAT trafficking: retrograde transport from endosomes to the TGN, and anterograde traffic from the Golgi to the IS. We address the specific role of four proteins, the GTPase Rab6, the t-SNARE syntaxin-16, the v-SNARE VAMP7 and the golgin GMAP210, in each pathway. Using different methods (endocytosis and Golgi trap assays, confocal and TIRF microscopy, TCR-signalosome pull down) we show that syntaxin-16 is regulating the retrograde transport of LAT whereas VAMP7 is regulating the anterograde transport. Moreover, GMAP210 and Rab6, known to contribute to both pathways, are in our cellular context, specifically and respectively, involved in anterograde and retrograde transport of LAT. Altogether, our data describe how retrograde and anterograde pathways coordinate LAT enrichment at the IS and point to the Golgi as a central hub for the polarized recruitment of LAT to the IS. The role that this finely-tuned transport of signaling molecules plays in T-cell activation is discussed.

Highlights

T cell activation is key in establishing an adaptive immune response and it requires a direct interaction between T cells and antigen presenting cells (APC), where the T cell receptor (TCR) recognizes a peptide presented by MHC molecules on the APC [1,2]
We previously showed that the vesicular SNARE VAMP7 [13], the small GTPase Rab6 [21], the target SNARE syntaxin-16 (Synt16) [21] and the Golgin GMAP210 [22] were present on linker for activation of T cells (LAT) vesicles and that they all controlled the recruitment of LAT to the immune synapse as well as some aspects of the TCR-induced activation of T lymphocytes
We have previously observed that LAT undergoes endocytosis from the plasma membrane to intracellular compartments from where it can be recruited to the immune synapse (IS) under TCR triggering [14,21]

Summary

Introduction

T cell activation is key in establishing an adaptive immune response and it requires a direct interaction between T cells and antigen presenting cells (APC), where the T cell receptor (TCR) recognizes a peptide presented by MHC molecules on the APC [1,2]. The contact region between both cells forms the immune synapse (IS), where both endocytic and exocytic vesicular trafficking focus [3] This regulated transport plays a key role in T cell activation since it controls the polarized secretion and concentration towards the interacting cells of cytokines [4,5], extracellular vesicles [6,7,8] and receptors and ligands such as CD40L [9,10], shaping the adaptive immune response. Different studies, including ours, have shown that molecules involved in T cell signaling are present both at the plasma membrane and in intracellular vesicular pools [12,13,14]. Deciphering the nature of these trafficking pathways and the molecular machinery involved is important for understanding the role(s) of this traffic in T cell activation

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Results

Conclusion