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Role of Membrane Dynamics on Immunological Responses

Final Report Summary - MEMBRANE DYNAMICS (Role of Membrane Dynamics on Immunological Responses)

There is strong evidence that molecular bioactivity in the plasma membrane, such as the activation of membrane receptors upon ligand binding, is modulated not only by specific protein-protein or lipid-protein interactions, but also by the ensemble behaviour of molecules at the membrane. Molecular ordering of lipids (i.e. lipid packing), for example, can locally change the conformational states of e.g. receptors, which in turn alters the interaction capability of associated proteins, with the net result being the compartmentalisation of signalling processes. Previous research has indicated that membrane organisation of this type could play an important role in immune cell activation by concentrating various key molecules in specific domains of the membrane and constituting a catalytic platform to initiate signaling. However, important questions remain, some of which Dr. Erdinc Sezgin had been pursuing in during his project duration: (1) is there any heterogeneity in lipid and protein organization in the plasma membrane of immune cells such as T-cells, mast cells and antigen presenting cells; (2) how does such heterogeneity affect the compartmentalization of key proteins involved in signaling and antigen presentation; and (3) how does this heterogeneity and/or compartmentalization affect functionality? Using biochemical approaches and model membrane systems he with other researchers have shown that the T-cell receptor prefers unsaturated lipid environments (Beck-Garcia et al., Biochim Biophys Acta, 2014). However, these methods did not allow us to observe the protein dynamics in their native environment in live cells. To address this issue in more native conditions, he has developed advanced new tools to visualise the heterogeneity of plasma membrane organisation in live cells. For example, he developed a spectral imaging method to accurately measure membrane lipid packing using a confocal microscope (Sezgin et al., ChemPhysChem, 2015). Also, he compared the abilities of a variety of fluorescent lipid reporters, in various experimental modalities, to reveal cellular membrane heterogeneity using advanced imaging approaches (Sezgin et al., Journal of Lipid Research, 2016). In addition, he has been developing super-resolution tools to investigate the nano-scale dynamics of the cellular plasma membrane (Honigmann et al., Nature Communications, 2014; Clausen et al., Methods, 2015; Vicidomini et al., Nano Letters, 2015). Finally, he is part of development of open-source, open-access computational tools for the analysis of this high-end microscopy and spectroscopy data (Waithe et al., Bioinformatics, 2016), which will enable other researchers to quantitatively characterise the nature of cellular membrane heterogeneity. Outcomes of this interdisciplinary, collaborative project will possibly be useful of medical applications which is directly related to “health”, one of the main FP7 priorities. It has a strong aspect on development of new tools to connect research and health to carry out translational research. Immunology and immune system diseases (e.g. AIDS, Diabetes Type 1, and leukaemia) are one of the top priorities of the health sector worldwide. Therefore, any development concerning immune system will have an impact on entire health sector. The innovations resulted from the proposed project (for instance; the in-vitro model for immune response and drug screening, single molecule imaging and data processing) will influence the European excellence dramatically. We believe, this project is a very solid example of translational research which will carry both European research and European health fields steps further.