Exploring biomolecular condensates in T cell receptor signaling – CONDENSING

Biomolecular condensates (BCs), originally identified as membraneless cytosolic fluid droplets, are found throughout the cell and are fundamental to cellular activities. Although comparatively less studied, BCs formed at the plasma membrane are proposed to play a crucial role in transmembrane signaling processes. The aim of the CONDENSING project is to investigate the structural and functional properties of T cell receptor (TCR) signaling BCs, which are proposed to be present at the plasma membrane of T lymphocytes during antigen recognition. We have therefore assembled a consortium to perform interdisciplinary studies using state-of-the-art biophotonics, biophysics, biochemistry and genetic engineering. We postulate that BC formation is critical to propagate and amplify the initiation of TCR signaling pathways upon binding to antigenic ligands by building molecular machines that enable the highly efficient and specific receptor-mediated signal transduction mechanism. Accordingly, we will develop three complementary lines of research to study TCR signaling BCs in mouse primary T cells: (i) to perform state-of-the-art microscopic and biophysical analyses of the organization and dynamics of BCs at the nanoscale; (ii) to analyze the TCR signaling interactomes involved in BC induction using proximity biotinylation labeling of gene-edited T cells and mass spectrometry, and to determine the functional contributions of BCs; (iii) to investigate how physicochemical and mechanical properties of membrane lipid bilayers interact with the formation, stability and activities of BCs. We anticipate that the results of this research program will lead to breakthroughs in the understanding of the mechanisms underlying the initiation of T cell activation and, more broadly, provide important insights into the role of BCs in signal transduction.