identification-mediators-t-cell-receptor-signaling-via-screening

Identification of Mediators of T-cell Receptor Signaling <em>via</em> the Screening of Chemical Inhibitor Libraries

The T-cell receptor (TCR) signaling pathway comprises a multitude of mediators that transmit signals upon the activation of the TCR. Different strategies ...

National University of Singapore

Katholieke Universiteit (KU) Leuven

Thymocyte selection involves the positive and negative selection of the repertoire of T cell receptors (TCRs) such that the organism does not suffer autoimmunity, yet has the benefit of the ability to recognize any invading pathogen. The signal transduced through the TCR is translated into a number of different signaling cascades that result in transcription factor activity in the nucleus and changes to the cytoskeleton and motility. Negative selection involves inducing apoptosis in thymocytes that express strongly self-reactive TCRs, whereas positive selection must induce survival and differentiation programs in cells that are more weakly self-reactive. The TCR recognition event is analog by nature, but the outcome of signaling is not. A large number of molecules regulate the strength of the TCR-derived signal at various points in the cascades. This review discusses the various factors that can regulate the strength of the TCR signal during thymocyte development.

TCR Signal Strength and T Cell Development.

Activation of the T cell receptor (TCR) leads to the generation of a network of signaling events critical to the developmental decision making and activation of T cells. Various experimental approaches continue to identify new signaling molecules, adaptor proteins, and other regulators of TCR signaling. We propose a screening strategy for the identification of small molecules affecting TCR signaling based on the uncoupling of TCR stimulation from cellular responses in developing thymocytes. We demonstrate that this strategy successfully identifies inhibitors of kinases already shown to act downstream of TCR engagement, as well as new inhibitors. The proposed strategy is easily scalable for high throughput screening and will contribute to the identification of new druggable targets in T cell activation.

Development of a screening strategy for new modulators of T cell receptor signaling and T cell activation.

Thymocyte-expressed molecule involved in selection (Themis) has been shown to be important for T cell selection by setting the threshold for positive versus negative selection. Themis interacts with the protein tyrosine phosphatase (PTP) Src-homology domain containing phosphatase-1 (Shp1), a negative regulator of the T cell receptor (TCR) signaling cascade. However, how Themis regulates Shp1 is still not clear. Here, using a very sensitive phosphatase assay on ex vivo thymocytes, we have found that Themis enhances Shp1 phosphatase activity by increasing its phosphorylation. This positive regulation of Shp1 activity by Themis is found in thymocytes, but not in peripheral T cells. Shp1 activity is modulated by different affinity peptide MHC ligand binding in thymocytes. Themis is also associated with phosphatase activity, due to its constitutive interaction with Shp1. In the absence of Shp1 in thymocytes, Themis interacts with Shp2, which leads to almost normal thymic development in Shp1 conditional knockout (cKO) mice. Double deletion of both Themis and Shp1 leads to a thymic phenotype similar to that of Themis KO. These findings demonstrate unequivocally that Themis positively regulates Shp1 phosphatase activity in TCR-mediated signaling in developing thymocytes.

Article	Year
TCR Signal Strength and T Cell Development. Annual review of cell and developmental biology\| PubMed ID: 27712102	2016
Development of a screening strategy for new modulators of T cell receptor signaling and T cell activation. Scientific reports\| PubMed ID: 29968737	2018
Themis-associated phosphatase activity controls signaling in T cell development. Proceedings of the National Academy of Sciences of the United States of America\| PubMed ID: 30413615	2018

Vasily Rybakin

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