Regulation of T cell activation by two conserved phosphotyrosines in Lck and its adapter protein TSAd
AbstractT cells are major players in the immune system. These cells can recognize dangerous antigens through their specific receptors. Harnessing the power of T cells would be beneficial for not only fighting numerous infectious diseases, but also for treating cancer or preventing autoimmune diseases. However, the intracellular signalling involved in the T-cell receptor (TCR) pathway is remarkably complex. It is necessary to understand it more fully in order to control the T cells behaviour. We focused on two proteins involved in TCR signalling. First, lymphocyte-specific protein tyrosine kinase (Lck) starts a phosphorylation cascade downstream of TCR stimulation. Lck itself is tightly controlled by the phosphorylation of two tyrosines: Tyr394 and Tyr505. Recently a third tyrosine, Tyr192, emerged as an important regulatory site. Second, T cell specific adaptor protein (TSAd) is best known for its interaction with Lck. Its main function is to facilitate binding between other proteins. TSAd itself contains a number of phosphotyrosines. One of the most interesting is Tyr290, as it is highly conserved, but it is not predicted to be a prototypic binding site. The aim of this thesis was to understand the function of two phosphotyrosines, Tyr192 in Lck and Tyr290 in TSAd, in order to better comprehend the intracellular signalling of the TCR. The study was based on the knock-in cell lines generated with CRISPR/Cas9 genome editing. The mutated cell lines were studied using a wide spectrum of molecular biology techniques, including mass spectrometry, western blotting, immunoprecipitation and flow cytometry. Our findings revealed that Lck Tyr192 could control and stabilize Lck activity, both positively and negatively. TSAd Tyr290 could also control the protein’s activity. Our results suggest that this tyrosine most likely facilitates the proteins conformation. We have shown that both phosphotyrosines could influence the whole TCR signalling pathway.
List of papers
|Paper I: A simple and efficient workflow for generation of knock-in mutations in Jurkat T cells using CRISPR/Cas9. P. Borowicz, H. Chan, D. Medina, S. Gumpelmair, H. Kjelstrup, A. Spurkland. Manuscript. Published in Scandinavian Journal of Immunology. 2020, 91 (4). DOI: 10.1111/sji.12862. The article is included in the thesis. Also available in DUO: http://urn.nb.no/URN:NBN:no-78665|
|Paper II: Tyr192 is a critical regulator of lymphocyte-specific tyrosine kinase activity in T cells. P. Borowicz, V. Sundvold-Gjerstad, H. Chan, G. Abrahamsen, H. Kjelstrup, T. A. Nyman, A. Spurkland. [Submitted]. To be published. The paper is not available in DUO awaiting publishing.|
|Paper III: A conserved pTyr motif in the unstructured C-terminus regulates the function of the T cell specific adaptor TSAd. P. Borowicz, R. P. Gopalakrishan, H. Chan, H. Kjelstrup, S. Foss, G. A. de Souza, V. Sundvold-Gjerstad, A. Spurkland. [Manuscript]. To be published. The paper is not available in DUO awaiting publishing.|