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Various Stages of Immune Synapse Formation Are Differently Dependent on the Strength of the TCR Stimulus.

ABSTRACT: Cytotoxic T lymphocytes (CTL) are key players of the adaptive immune system that target tumors and infected cells. A central step to that is the formation of a cell-cell contact zone between the CTL and its target called an immune synapse (IS). Here, we investigate the influence of the initial T cell receptor (TCR) trigger of a cytolytic IS on the distinct steps leading to cytotoxic granule (CG) exocytosis. We stimulated primary CTLs from mouse using lipid bilayers with varying anti-CD3 but constant ICAM concentrations. We fluorescently labeled molecular markers of distinct IS zones such as actin, CD3, granzyme B, and Synaptobrevin2 in CTLs and imaged cytolytic IS formation by total internal reflection fluorescence microscopy (TIRFM). We found that an intermediate anti-CD3 concentration of 10 µg/mL induces the fastest adhesion of CTLs to the bilayers and results in maximal CG fusion efficiency. The latency of actin ring formation, dwell time, and maximum surface area at the IS exhibit different dependencies on the stimulatory anti-CD3 concentrations. The number and surface area of CD3 clusters at the IS seem to show a different dependency to the TCR trigger when compared to their dwell time. Finally, the mode of full CG exocytosis appears to be independent of the TCR trigger.

SUBMITTER: Estl M

PROVIDER: S-EPMC7177831 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature

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Various Stages of Immune Synapse Formation Are Differently Dependent on the Strength of the TCR Stimulus.

Estl Michael M Blatt Pascal P Li Xuemei X Becherer Ute U Chang Hsin-Fang HF Rettig Jens J Pattu Varsha V

International journal of molecular sciences 20200402 7

Cytotoxic T lymphocytes (CTL) are key players of the adaptive immune system that target tumors and infected cells. A central step to that is the formation of a cell-cell contact zone between the CTL and its target called an immune synapse (IS). Here, we investigate the influence of the initial T cell receptor (TCR) trigger of a cytolytic IS on the distinct steps leading to cytotoxic granule (CG) exocytosis. We stimulated primary CTLs from mouse using lipid bilayers with varying anti-CD3 but cons ...[more]

PMID: 32252488

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Project description:T lymphocyte recognition of antigenic peptides on the surface of antigen-presenting cells (APC) leads to immune synapse formation (IS). By analogy with the nervous synapse, this cell-cell communication model requires the formation of highly organized structures that delimit an active zone of membrane traffic. For T cells to connect antigen recognition with the biological response, receptors and signaling proteins must be recycled. Sorting nexin 27 (SNX27) is an endosomal protein best known for its role in recycling PDZ (PSD95, Dlg1, ZO-1)-interacting neuronal proteins via the retromer transport machinery. Alteration of this sorting pathway leads to neurodegeneration and is associated to Down syndrome, Alzheimer’s and Parkinson’s diseases. In T lymphocytes, SNX27 interacts with diacylglycerol kinase zeta (DGKz), which provides a mechanistic link between diacylglycerol metabolism and membrane trafficking. Following antigen recognition, SNX27-positive endosomes polarize to the IS and a PDZ-dependent SNX27 pool accumulates at the cell-cell contact area. To test for additional SNX27 functions, we carried out proteomic analysis of the SNX27 interactome purified from T cells in contact with APC, and identified SNX27 interaction with the retromer and with members of the WASH (Wiskott-Aldrich syndrome protein and SCAR homologue) complex. This finding indicates the conserved nature of the SNX27/WASH/retromer complex in hematopoietic cells and suggests similarity between neurological diseases and abnormal immune/inflammatory responses. We also found PDZ-dependent SNX27 cargoes, including modulators of cytoskeletal reorganization such as zona occludens-2 (ZO-2). ZO-2, a cytosolic component of epithelial cell-cell junctions, localized to the IS, and SNX27 silencing affected ZO-2 stability at the synapse. This study broadens our knowledge of SNX27 function in T lymphocytes, and suggests that pathways that delimit polarized structures in epithelial systems also participate in IS regulation.

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Various Stages of Immune Synapse Formation Are Differently Dependent on the Strength of the TCR Stimulus.

Publications

Various Stages of Immune Synapse Formation Are Differently Dependent on the Strength of the TCR Stimulus.

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