Regulation of T-cell Function Through Changes in Local Membrane Architecture

• Applicant: Dr. Marcin Lyszkiewicz, Ph.D.
• Subject Area: Clinical Immunology and Allergology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 504988939

Primary immunodeficiencies provide a unique insight into the mechanism governing the human immune system at times leading to astounding results. In the age of widespread omics technologies identification of the genes responsible for inborn defects of immunity has become easier than ever before. Also probing the affected cells on transcriptome or proteome level gives a superficially detailed description of the disease. Although such an approach results in the generation of a large volume of data, it sometimes fails to explain an exact mechanism involved. To decipher the molecular basis of the disease and to link how a deficiency in a particular gene impact the cells of the immune system, the generation of a suitable model(s) is frequently a must. Here, the rationale of the project is rooted in a recently published discovery, where we directly link a specific nucleator of clathrin-mediated endocytosis called FCHO1 with the generation and activation of T cells in humans. By developing numerous heterologous in vitro systems and by applying state-of-the-art confocal microscopy techniques we explained how the mutations impact protein function on molecular level and provided direct evidence that clathrin-mediated endocytosis plays an indispensable role in the endocytosis of T-cell receptors. However, the exact mechanism of how this process is governed and how specific CME-adaptor evolved to support the adaptive immune system remain enigmatic. In this proposal, upon the development of murine models of FCHO1 and its paralogue FCHO2 deficiency, we will test the hypothesis that the FCHO1 protein in higher vertebrates evolved to govern the endocytosis of lymphocyte receptors, such as TCR. To address those questions, the following specific aims will be taken: Aim Ia: How does FCHO1 insufficiency affect the TCR internalisation and signalling dynamic? Aim Ib: How perturbation of CME in lymphocytes affects lymphocyte biology and thus predispose individuals to infection? Aim Ic: Is evolutionary speciation of two FCHO paralogues associated with their functorial specialisation in higher vertebrates? Aim Id: Does genetic polymorphism in the FCHO1 locus affect TCR internalisation and clustering?

• DFG Programme: Research Grants